Complications of Pre-eclampsia 439 chronically stimulating autoregulatory mechanisms, thus increas- ing vascular tone and producing vascular hypertrophy. These changes then may impede pregnancy - induced plasma volume expansion, which occurs in normal pregnancies, and result in general circulatory maladaptation. One of the more striking clinical risk factors for the develop- ment of pre - eclampsia is the antiphospholipid syndrome. At the University of Utah, Branch et al. [44] studied 43 women who presented with severe pre - eclampsia prior to 34 weeks of gesta- tion and found 16% to have signifi cant levels of antiphospholipid antibodies. They recommended that women with early - onset severe pre - eclampsia be screened for antiphospholipid antibodies and, if detected, be considered for prophylactic therapy in subse- quent pregnancies. The same group [45] found a high incidence of pre - eclampsia (51%) and severe pre - eclampsia (27%) in 70 women with antiphospholipid syndrome whose pregnancies pro- gressed beyond 15 weeks of gestation, despite various medical treatment protocols. An integrated model of pre - eclampsia pathophysiology has been proposed by Romero et al. [46] . Abnormal placentation is thought to be the fi rst step in the development of the disease, possibly related to immune mechanisms. Trophoblastic prosta- cyclin, which may be important with respect to trophoblast inva- sion and prevention of blood clotting in the intervillous space, becomes defi cient. A relative decrease in the prostacyclin – thromboxane ratio allows platelet aggregation, thrombin activa- Table 34.1 Classifi cation of hypertensive diseases during pregnancy. Chronic hypertension Hypertension that is present before pregnancy or diagnosed before 20 weeks of gestation Pre - eclampsia – eclampsia Hypertension plus proteinuria usually occurring after 20 weeks of gestation or earlier with trophoblastic diseases Pre - eclampsia superimposed upon chronic hypertension Chronic hypertension with signs and symptoms of pre - eclampsia such as: Blood pressure ≥ 160/110 mmHg Proteinuria ≥ 2.0 g/24 h Serum creatinine > 1.2 mg/dL unless previously elevated Thrombocytopenia Persistent epigastric pain Elevated hepatic transaminases Persistent neurologic disturbances Gestational hypertension These are retrospective diagnoses. If pre - eclampsia is not present at the time of delivery and elevated blood pressure: Transient hypertension of pregnancy: returns to normal by 12 weeks post partum Chronic hypertension: persists beyond 12 weeks Modifi ed from the Working Group Report on High Blood Pressure in Pregnancy. National Heart, Lung, and Blood Institute. NIH Publication No. 00 - 3029, July 2000. Table 34.2 Complications of severe pregnancy - induced hypertension. Cardiovascular Severe hypertension Pulmonary edema Renal Oliguria Renal failure Hematologic Hemolysis Thrombocytopenia Disseminated intravascular coagulopathy Neurologic Eclampsia Cerebral edema Cerebral hemorrhage Amaurosis Hepatic Hepatocellular dysfunction Hepatic rupture Uteroplacental Abruption Intrauterine growth retardation Fetal distress Fetal death Table 34.3 Risk factors for the development of pregnancy - induced hypertension. Risk factor Risk ratio Nulliparity 3 Age > 40 years 3 African - American race 1.5 Family history of pregnancy - induced hypertension 5 Chronic hypertension 10 Chronic renal disease 20 Antiphospholipid syndrome 10 Diabetes mellitus 2 Twin gestation 4 Angiotensinogen gene T235 mutation Homozygous 20 Heterozygous 4 Revised from American College of Obstetricians and Gynecologists. Hypertension in Pregnancy . ACOG Technical Bulletin 219. Washington, DC: American College of Obstetricians and Gynecologists, 1996. tion, and fi brin deposition in systemic vascular beds. Thrombosis and vasospasm develop and lead to multiorgan involvement, including renal, hepatic, neurologic, hematologic, and uteropla- cental dysfunction. Chapter 34 440 necessitates careful evaluation, management in a tertiary care facility, and consideration for delivery [3] . General m anagement p rinciples for p re - eclampsia On suspecting the diagnosis of pre - eclampsia, several steps are initiated simultaneously to treat and further evaluate the mother and her fetus. A peripheral intravenous line is placed and fl uid therapy initiated. These patients are often volume - depleted and benefi t from intravenous hydration, but are also susceptible to volume overload, so meticulous monitoring of intake and output is recommended. Routine laboratory evaluation for pre - eclampsia (Table 34.5 ) includes complete blood count, platelet count, serum creatinine, and liver enzyme analyses [46,56 – 59] . If delivery is not felt to be imminent, a 24 - hour collection of urine should be started for volume, creatinine clearance, and total protein excretion. The patient should be placed in a lateral recumbent position and fetal assessment (ultrasound, non - stress test, or biophysical profi le) performed as indicated [60] . Amniocentesis for fetal lung matu- rity may be considered in those cases in which fetal maturity is in question and the disease process is not severe enough to mandate delivery. When severe pre - eclampsia is diagnosed, immediate delivery, regardless of gestational age, has generally been recommended [61] . Conservative management has been proposed in select cases [62 – 64] ). Sibai and colleagues retrospectively reviewed 60 cases of conservatively managed severe pre - eclampsia during the second trimester (18 – 27 weeks gestation). They found a high maternal morbidity rate, with complications such as abruptio placentae, eclampsia, coagulopathy, renal failure, hypertensive encephalopathy, intracerebral hemorrhage, and ruptured hepatic hematoma. Additionally, an 87% perinatal morality rate was noted [65] . In subsequent prospective studies, Sibai and col- leagues reported improved perinatal outcomes with no increased rate of maternal complications in a select group of women with severe pre - eclampsia between 24 – 27 weeks of gestation and 28 – 32 weeks of gestation [66] who were managed with intensive fetal and maternal monitoring under strict protocols in a tertiary care center. In another randomized controlled trial, expectant management in selected severe pre - eclamptics between 28 and 34 Women with a previous pregnancy complicated by pre - eclampsia have an increased risk for recurrence in subsequent pregnancies. For severe pre - eclamptic women in an initial preg- nancy, recurrence rates for pre - eclampsia are very high, approach- ing 50% in some studies. Furthermore, signifi cant maternal and fetal complications are more common in recurrent pre - eclampsia compared with an initial episode [47] . All of the preceding theories still do not allow accurate predic- tion of which gravidas will develop pre - eclampsia, and an ideal screening test is currently not available [19,48] . Furthermore, it is still not clear which process or processes separate mild disease from the development of critical illness and multiorgan dysfunction. Diagnosis of p re - eclampsia The diagnosis of pre - eclampsia is often clinically confusing and erroneous [49 – 52] . Blood pressure (BP) criteria include a systolic BP of at least 140 mmHg or a diastolic BP of at least 90 mmHg. The relative rise from baseline values in systolic pressure of 30 mmHg or diastolic pressure of 15 mmHg appears to be of questionable value [53,54] . Signifi cant proteinuria is defi ned as at least 300 mg in a 24 - hour period. Semiquantitative dipstick analysis of urinary protein is poorly predictive of the actual degree of proteinuria measured by 24 - hour urinary collections; thus, classifi cation of pre - eclampsia based on proteinuria should be confi rmed with a 24 - hour quantitative collection [55] . Edema and weight gain historically have been included in the diagnostic triad (hypertension, proteinuria, edema) of pre - eclampsia, but have been de - emphasized recently due to the ubiquitous nature of edema during pregnancy [1] . These changes usually occur after 20 weeks of gestation, except when there exist hydatidiform changes of the chorionic villi, such as seen with hydatidiform mole or hydrops fetalis. The signs and symptoms of severe pre - eclampsia are summa- rized in Table 34.4 . The development of these manifestations Table 34.4 Diagnostic criteria for severe pre - eclampsia. Blood pressure > 160 – 180 mmHg systolic or > 110 mmHg diastolic Proteinuria > 5 g/24 h Oliguria defi ned as < 500 mL/24 h Cerebral or visual disturbances Pulmonary edema Epigastric or right upper quadrant pain Impaired liver function of unclear etiology Thrombocytopenia Fetal intrauterine growth retardation or oligohydramnios Elevated serum creatinine Grand mal seizures (eclampsia) Revised from American College of Obstetricians and Gynecologists. Hypertension in Pregnancy . ACOG Technical Bulletin 219. Washington, DC: American College of Obstetricians and Gynecologists, 1996. Table 34.5 Laboratory evaluation for pre - eclampsia. Complete blood count Platelet count Liver function tests (ALT and AST) Renal function tests (creatinine, blood urea nitrogen, uric acid) Urinalysis and microscopy 24 - hour urine collection for protein and creatinine clearance Blood type and antibody screen Complications of Pre-eclampsia 441 These investigators found that the only benefi t of such manage- ment was avoidance of sudden profound drops in systemic blood pressure and fetal distress during antihypertensive therapy. The overall incidence of fetal distress in labor was not affected, however. Because of a signifi cant requirement for pharmacologic diuresis to prevent pulmonary edema in the study group, these authors recommended that COP not be corrected with colloid unless markedly decreased (12 mmHg) or a prolonged negative COP – PCWP gradient was identifi ed. While the infusion of col- loids has been shown to result in less of a decrease in COP when compared with crystalloids, there is no evidence of any clinical benefi t of colloids over crystalloids for the pregnant patient [81] . Thus, in the absence of a fi rm clinical indication for colloid infu- sion, carefully controlled crystalloid infusions appear to be the safest mode of fl uid therapy in severe pre - eclampsia. A randomized clinical trial (n = 264) compared the postpar- tum management of pre - eclampsia with brief furosemide therapy (20 mg oral furosemide daily for 5 days with 20 mEq per day of oral potassium supplementation) versus no furosemide therapy, after spontaneous onset of postpartum diuresis and discontinu- ation of intravenous magnesium sulfate. Only patients with severe pre - eclampsia appeared to benefi t from furosemide therapy, defi ned by more rapid normalization of blood pressure and reduction in the need for antihypertensive therapy. Shortening of hospitalization and reduction of delayed postpartum compli- cations were not observed. Seizure p rophylaxis for p re - eclampsia Magnesium sulfate (MgSO 4 · 7 H 2 O USP) has been used for the prevention of eclamptic seizures since the early 20th century [82 – 84] and has long been the standard treatment of pre - eclamp- sia – eclampsia in the United States [85,86] . The mechanism of action of magnesium sulfate remains controversial [87] . Some investigators feel that magnesium acts primarily via neuromus- cular blockade, while others believe that magnesium acts centrally [88,89] . Two separate investigations evaluating the effect of par- enteral magnesium sulfate on penicillin - induced seizure foci in cats report confl icting data [88,90] . Koontz and Reid [90] postu- late that magnesium may be effective as an anticonvulsant only when the blood – brain barrier is disrupted. Human data reveal that abnormal EEG fi ndings are common in pre - eclampsia – eclampsia, and they are not altered by levels of magnesium con- sidered to be therapeutic [91] . In the rat model, Hallak et al. [92] and Hallak [93] proposed that magnesium ’ s anticonvulsant mechanism of action was central, mediated through excitatory amino acid (N - methyl - d - aspartate) receptors. In a randomized placebo - controlled study, Belfort et al. [94] evaluated the effect of magnesium sulfate on maternal retinal blood fl ow in pre - eclamptics by way of Doppler blood fl ow measurements of central retinal and posterior ciliary arteries. Their fi ndings suggested that magnesium sulfate vasodilates small vessels in the retina and pro- posed that this may refl ect similar changes occurring in the cere- weeks of gestation was not associated with an increase in maternal complications, but did result in a signifi cant prolongation of the pregnancy, reduction of neonates requiring ventilation, and a reduction in the number of neonatal complications [67] . The presence of pre - eclampsia does not guarantee accelerated lung maturation, and a high incidence of neonatal respiratory complications has been associated with premature delivery for pre - eclampsia [68,69] . In a stable maternal – fetal environment, steroid therapy may be considered if amniocentesis reveals fetal lung immaturity or the clinical situation is consistent with pre- maturity. Although delivery is generally indicated for severe pre - eclampsia regardless of gestational age, we feel that conservative therapy in a tertiary care center is appropriate in select premature patients with proteinuria exceeding 5 g/24 h, mild elevations of serum transaminase levels, or borderline decreases in platelet count and blood pressure that is controllable. Fluid t herapy for p re - eclampsia Fluid management in severe pre - eclampsia consists of crystalloid infusions of normal saline or lactated Ringer ’ s solution at 100 – 125 mL/h. Additional fl uid volumes, in the order of 1000 – 1500 mL, may be required prior to use of epidural anesthesia or vasodilator therapy to prevent maternal hypotension and fetal distress [70] . Epidural anesthesia appears to be safe and is the anesthetic method of choice in severe pre - eclampsia, if preceded by volume preloading to avoid maternal hypotension [71 – 75] . Likewise, severely hypertensive patients receiving vasodilator therapy may require careful volume preloading to prevent an excessive hypo- tensive response to vasodilators. Abrupt and profound drops in blood pressure leading to fetal bradycardia and distress may occur in severe pre - eclampsia when vasodilator therapy is not accompanied by volume expansion [76 – 78] . Intravenous fl uids are known to cause a decrease in colloid oncotic pressure (COP) in laboring patients [79] . In addition, baseline COP is decreased in patients with pre - eclampsia and may decrease further postpartum as a result of mobilization of inter- stitial fl uids. This may be clinically relevant with respect to the development of pulmonary edema in pre - eclamptic patients [80] . Therefore, close monitoring of fl uid intake and output, hemody- namic parameters, and clinical signs must be undertaken to prevent an imbalance of hydrostatic and oncotic forces that potentiate the occurrence of pulmonary edema. Kirshon et al. [77] placed systemic and pulmonary artery cath- eters in 15 primigravid patients with severe pre - eclampsia during labor. A hemodynamic protocol requiring strict control of COP, pulmonary capillary wedge pressure (PCWP), and mean arterial pressure (MAP) throughout labor, delivery, and the postpartum period was followed. Low COP and PCWP were corrected with the administration of albumin. Severe hypertension was treated as needed with intravenous nitroglycerin, nitroprusside, or hydralazine. Furosemide was administered for elevated PCWP. Chapter 34 442 [61,69,99] , whereas in the United Kingdom and in a few US centers, conventional antiepileptic agents have been advocated [100 – 103] . Recently, several important randomized clinical trials of magnesium sulfate for prevention or control of eclamptic seizures have been published (Table 34.7 ). In a randomized trial comparing magnesium sulfate with phenytoin for the prevention of eclampsia, Lucas et al. [104] found a statistically signifi cant difference (P = 0.004) in the devel- opment of seizures between the magnesium sulfate group (0/1049) and the phenytoin group (10/1089), with no signifi cant differences in eclampsia risk factors between the two study groups. The Eclampsia Trial Collaborative Group [105] enrolled 1,687 women with eclampsia in an international multicenter random- ized trial comparing standard anticonvulsant regimens of mag- nesium sulfate, phenytoin, and diazepam. Women allocated magnesium sulfate had a 52% lower risk of recurrent convulsions than those allocated diazepam, and a 67% lower risk of recurrent convulsions than those allocated phenytoin. Women allocated magnesium sulfate were less likely to require mechanical ventila- tion, to develop pneumonia, and to be admitted to intensive care than those allocated phenytoin. Furthermore, the babies of mothers allocated magnesium sulfate were less likely to be intu- bated at delivery and less likely to be admitted to the newborn intensive care nursery when compared with babies of mothers treated with phenytoin. The Eclampsia Trial Collaborative Group concluded that magnesium sulfate is the drug of choice for routine anticonvusant management of women with eclampsia, rather than diazepam or phenytoin, and recommended that other anticonvulsants be used only in the context of randomized trials. Coetzee et al. [106] conducted a blinded, randomized, con- trolled trial (n = 822) of intravenous magnesium sulfate versus placebo in the management of women with severe pre - eclampsia. They found that use of intravenous magnesium sulfate signifi - cantly reduced the development of eclampsia (0.3% vs 3.2%, relative risk 0.09; 95% confi dence interval 0.01 – 0.69; P = 0.003) compared to placebo. Thus at present, magnesium sulfate is strongly endorsed as the agent of choice for eclampsia prophylaxis and treatment bral circulation. More recently, Belfort et al. [95] showed that magnesium sulfate reduces cerebral perfusion pressure while at the same time maintaining cerebral blood fl ow. This fi nding sug- gests that at least in part, magnesium sulfate acts by preventing or reducing hypertensive encephalopathy and barotrauma of the cerebral microcirculation [96] . Magnesium sulfate regimens are illustrated in Table 34.6 . Because a regimen of a 4 - g IV loading dose followed by a 1 – 2 - g/h IV maintenance dose failed to prevent eclampsia in a signifi cant number of pre - eclamptic women, Sibai et al. [97] modifi ed this regimen to a 4 - g IV loading dose followed by a 2 – 3 - g/h IV main- tenance dose. Sibai compared Pritchard ’ s regimen of a 4 - g IV and 10 - g IM loading dose followed by a 5 - g IM maintenance dose every 4 hours, with a 4 - g IV loading dose followed by a 1 – 2 - g/h continuous IV maintenance infusion. The IV loading dose with maintenance dose of 1 g/h did not produce adequate serum levels of magnesium (4 – 7 mEq/L); thus, they recommended a 2 – 3 - g/h maintenance dose [97] . We employ a regimen of a 4 – 6 - g IV loading dose over 20 minutes, followed by a 2 – 3 - g/h continuous IV infusion. The maintenance infusion may be adjusted accord- ing to clinical parameters and serum magnesium levels. Pruett et al. [98] found no signifi cant effects on neonatal Apgar scores at these doses. Until relatively recently there remained considerable contro- versy regarding the best agent for eclampsia prophylaxis. In the United States, magnesium sulfate has been the agent of choice Table 34.6 Magnesium sulfate protocols. Loading dose Maintenance dose Pritchard [85] Eclampsia 4 g IV and 10 g IM 5 g IM every 4 h Zuspan [323] Severe pre - eclampsia None 1 g/h IV Eclampsia 4 – 6 g IV over 5 – 10 min 1 g/h IV Sibai et al. [97] Pre - eclampsia – eclampsia 6 g IV over 15 min 2 g/h Table 34.7 Randomized trials comparing magnesium sulfate ( M g SO 4 ) with other agents in prophylaxis (preventing eclampsia in pre - eclamptics) and treatment (preventing recurrent seizures) of eclampsia. Reference Study population n MgSO 4 Placebo Phenytoin Diazepam Lytic cocktail Nimodipine Bhalla [326] Eclamptics 91 2.2% – – – 24.4% – Lucas et al. [104] Mixed pre - eclamptics 2138 0% – 0.9% – – – Eclampsia Trial Collaborative Group [105] Eclamptics 905 13.2% – – 27.9% – – Eclamptics 775 5.7% – 17.1% – – – Coetzee et al. [106] Severe pre - eclamptics 685 0.3% 3.2% – – – – Magpie Trial Collaborative Group [319] Mixed pre - eclamptics 10,141 0.8% 1.9% – – – – Belfort et al. [287] Severe pre - eclamptics 1650 0.8% – – – – 2.6% Complications of Pre-eclampsia 443 Antihypertensive t herapy for s evere p re - eclampsia Pre - eclampsia is sometimes manifested by severe systemic hyper- tension. Careful control of hypertension must be achieved to prevent complications such as maternal cerebral vascular acci- dents and placental abruption. Medical intervention is usually recommended when the diastolic BP exceeds 110 mmHg [116,121,122] . The degree of systolic hypertension requiring therapy is less certain, but most would treat for a level exceeding 160 – 180 mmHg, depending on the associated diastolic pressure. In the previously normotensive patient, cerebral autoregulation is lost and the risk of intracranial bleeding increases when MAP exceeds 140 – 150 mm Hg, as illustrated in Figure 34.1 [123] . Although many different antihypertensive agents are available, we confi ne our discussion to those agents most commonly used for acute hypertensive crises in pregnancy (Table 34.8 ). Hydralazine h ydrochloride Hydralazine hydrochloride (Apresoline) has long been the gold standard of antihypertensive therapy for use by obstetricians in the United States. Hydralazine reduces vascular resistance via direct relaxation of arteriolar smooth muscle, affecting precapil- lary resistance vessels more than postcapillary capacitance vessels [124] . Assali et al. [125] noted the hypotensive effect to be marked and prolonged in pre - eclamptic patients, moderate in patients with essential hypertension, and slight in normotensive subjects. Using M - mode echocardiography, Kuzniar et al. [126] found an attenuated response to a 12.5 - mg IV dose of hydralazine in patients with pre - existing hypertension, compared with those with severe pre - eclampsia. Cotton et al. [127] studied the cardio- vascular alterations in six severe pre - eclamptics following intra- [1,107 – 110] . The Cochrane Review of randomized clinical trials found magnesium superior to lytic cocktail (chlorpromazine, promethazine, pethidine), diazepam, and phenytoin for preven- tion and/or treatment of eclampsia [111 – 114] . The role of mag- nesium sulfate seizure prophylaxis for mild pre - eclamptics is still subject to debate. Plasma magnesium levels maintained at 4 – 7 mEq/L are felt to be therapeutic in preventing eclamptic seizures [3] . Patellar refl exes usually are lost at 8 – 10 mEq/L, and respiratory arrest may occur at 13 mEq/L [85,115] . Urine output, patellar refl exes, and respiratory rates should be monitored closely during magnesium sulfate administration. In those patients who have renal dysfunc- tion, serum magnesium levels should be monitored as well. Calcium gluconate, oxygen therapy, and the ability to perform endotracheal intubation should be available in the event of mag- nesium toxicity [115] . Calcium will reverse the adverse effects of magnesium toxicity. Calcium gluconate is administered as a 1 - g dose (10 mL of a 10% solution) IV over a period of 2 minutes [116] . Bohman and Cotton [117] reported a case of supralethal magnesemia (38.7 mg/dL) with patient survival and no adverse sequelae. The essential elements in the resuscitation and prevention of toxic magnesemia are: (i) respiratory support as determined by clinical indicators; (ii) use of continu- ous cardiac monitoring; (iii) infusion of calcium salts to prevent hypocalcemia and the enhanced cardiotoxicity associated with concurrent hypocalcemia and hypermagnesemia; (iv) use of loop or osmotic diuretics to excrete the magnesium ion more rapidly, as well as careful attention to fl uid and electrolyte balances; (v) a consideration that toxic magnesium is neither anesthetic nor amnestic to the patient; and (vi) assurance that all magnesium infusions be administered in a buretrol - type system or by intramuscular injection to prevent toxic magnesemia. Magnesium sulfate is not an antihypertensive agent [85] . Administration produces a transient decrease in BP in hyperten- sive, but not normotensive, non - pregnant subjects [118] . Young and Weinstein [119] noted signifi cant respiratory effects and a transient fall in maternal BP in patients who received a 10 - g IM loading dose of magnesium sulfate followed by maintenance push doses of 2 g every 1 – 2 hours, but not in patients who received the 10 - g loading dose followed by a 1 - g/h continuous infusion [119] . Cotton et al. [76] observed a transient hypotensive effect related to bolus infusion, but not with continuous infusion in severe pre - eclampsia. Duration of magnesium administration post - delivery for seizure prophylaxis in severe pre - eclampsia has traditionally been 24 hours in many centers. A randomized clinical trial of 98 severe pre - eclamptics compared standard 24 - hour treatment with discontinuation of magnesium upon the onset of maternal diuresis, defi ned as urine output > 100 mL/h for 2 consecutive hours [120] . This study showed no untoward outcomes or need for re - initiation of treatment with discontinuation of therapy at diuresis. 50 100 Normotensive Previously Hypertensive Mean Arterial Pressure mm Hg Cerebral Blood Flow 150 200 Figure 34.1 Cerebral blood fl ow remains constant over a wide range of pressures in normotensive individuals. This range is shifted to the right in individuals with chronic hypertension. (Modifi ed from Zimmerman JL. Hypertensive crisis: emergencies and urgencies. In: Ayers SM, ed. Textbook of Critical Care . Philadelphia: WB Saunders, 1995.) Chapter 34 444 tion (300 mg within 10 s), because the infusion method results in a more gradual decline in BP and can be interrupted in cases of exaggerated drop in BP. Calcium c hannel b lockers Calcium channel blockers such as nifedipine (Procardia, Adalat) lower BP primarily by relaxing arterial smooth muscle. An initial oral dose of 10 mg is administered, which may be repeated after 30 minutes, if necessary, for the acute management of severe hypertension; 10 – 20 mg may then be administered orally every 3 – 6 hours as needed [121] . Principal side effects in severe pre - eclamptics include headache and cutaneous fl ushing. Care must be given when nifedipine is administered to patients receiving concomitant magnesium sulfate because of the possibility of an exaggerated hypotensive response [135] . In a randomized clinical trial, 49 women with severe pre - eclampsia and severe hyperten- sion between 26 and 36 weeks of gestation were primarily treated with sublingual (then oral) nifedipine or intravenous (then oral) hydralazine [136] . Effective control of BP (values consistently below 160/110 mmHg) was achieved in 96% of the nifedipine group and 68% of the hydralazine group (P < 0.05), with acute fetal distress occurring more commonly in the hydralazine group. A benefi cial effect may also be seen on urine output in women with severe pre - eclampsia treated with nifedipine [137,138] . Other calcium channel blockers (nimodipine) have been studied in the management of pre - eclampsia [139 – 142] and are the subject of ongoing investigation. Labetalol Labetalol (Normodyne, Trandate) is a combined α - and β - adrenoceptor antagonist that may be used to induce a controlled venous administration of a 10 - mg bolus of hydralazine. They observed a signifi cant increase in maternal heart rate and cardiac index (CI), with a decrease in MAP and systemic vascular resis- tance (SVR) index. There was a wide range of individual response with respect to peak and duration. Jouppila et al. [128] measured maternal – fetal effects with Doppler in severe pre - eclamptics receiving dihydralazine and demonstrated a fall in maternal BP with no change in intervillous blood fl ow and an increase in umbilical vein blood fl ow. Dihydralazine also has been shown to cross the placenta to the fetus [129] . The administration of hydralazine may result in maternal hypotension and fetal distress [130] . For this reason, we recommend an initial dose of 2.5 – 5.0 mg IV, followed by observation of hemodynamic effects. If appropriate change in BP is not achieved, 5 – 10 mg IV may be administered at 20 - minute intervals to a total acute dose of 30 – 40 mg. Hypertension refractory to the preceding approach war- rants the use of alternative antihypertensive agents [131,132] . Diazoxide Diazoxide (Hyperstat) is a benzothiadiazine derivative that exerts its antihypertensive effect by reducing peripheral vascular resis- tance through direct relaxation of arterioles [133] . The com- monly used 300 - mg bolus injection to treat severe hypertension may induce signifi cant hypotension with resultant morbidity. Minibolus diazoxide titration is clinically effective and relatively free of side effects in non - pregnant, severely hypertensive adults; a suggested dose would be 30 – 60 mg IV in 5 - minute intervals, titrating to desired clinical response. Thien et al. [134] recom- mended that diazoxide for the treatment of severe pre - eclampsia – eclampsia be administered by the infusion method (15 mg/min; total amount, 5 mg/kg body weight) rather than by bolus injec- Table 34.8 Pharmacologic agents for antihypertensive therapy in pre - eclampsia – eclampsia. Generic name Trade name Mechanism of action Dosage Comment Hydralazine Apresoline Arterial vasodilator 5 mg IV, then 5 – 10 mg IV/20 min up to total dose of 40 mg; titrated IV infusion 5 – 10 mg/h Must wait 20 min for response between IV doses; possible maternal hypotension Labetalol Normodyne Trandate Selective α - and non - selective β - antagonist 20 mg IV, then 40 – 80 mg IV/10 min to 300 mg total dose; titrated IV infusion 1 – 2 mg/min Less refl ex tachycardia and hypotension than with hydralazine Nifedipine Procardia Adalat Calcium channel blocker 10 mg PO, may repeat after 30 min Oral route only; possible exaggerated effect if used with MgSO 4 Nitroglycerin Nitrostat IV Tridil Nitro - Bid IV Relaxation of venous (and arterial) vascular smooth muscle 5 µ g/min infusion; double every 5 min Requires arterial line for continuous blood pressure monitoring; potential methemoglobinemia Nitroprusside Nipride Nitropress Vasodilator 0.25 µ g/kg/min infusion; increase by 0.25 µ g/kg/min every 5 min Requires arterial line for continuous blood pressure monitoring; potential cyanide toxicity Modifi ed from Dildy GA, Cotton DB. Hemodynamic changes in pregnancy and pregnancy complicated by hypertension. Acute Care 1988 – 89; 14 – 15: 26 – 46. Complications of Pre-eclampsia 445 may be an early sign of cyanide toxicity. In non - pregnant sub- jects, sodium nitroprusside infusion rates in excess of 4 µ g/kg/ min led to red blood cell cyanide levels that after 2 – 3 hours of administration extended into the toxic range ( > 40 nmol/mL); infusion rates of less than 2 µ g/kg/min for several hours remained non - toxic [157] ). Treatment time should be limited because of the potential for fetal cyanide toxicity [158] . Correction of hypo- volemia prior to initiation of nitroprusside infusion is essential in order to avoid abrupt and often profound drops in BP. Angiotensin - converting e nzyme i nhibitors Angiotensin - converting enzyme (ACE) inhibitors (captopril, enalapril) interrupt the renin – angiotensin – aldosterone system, resulting in a lowering of BP [159] . The risk of inducing neonatal renal failure and other serious complications would contraindi- cate the use of ACE inhibitors during pregnancy [160 – 163] . Fetal abortion has been reported in pregnant rabbits [164] . Additionally, the ACE inhibitors as a class do not appear to be useful in acute treatment of severe hypertension because of a 1 – 4 - hour delay in achievement of peak serum levels after ingestion [159] . Severe h ypertension We recommend labetalol for the initial management of severe hypertension in pre - eclampsia (BP 180 – 160/110 mmHg). Labetalol will be effective in restoring BP to a desired range (160 – 130/110 – 80 mmHg) in the majority of cases and has favorable cerebral hemodynamic effects with a minimum of adverse fetal effects. Hydralazine is used if labetalol is ineffective and if maximum doses (up to 40 mg) have not corrected the severe hypertension, we then proceed to nifedipine. Hydralazine in high doses has been associated with diversion of blood from the utero- placental ciculation and sudden - onset fetal decompensation. In rare cases, these agents are ineffective, and we resort to intrave- nous infusion of nitroglycerin or nitroprusside, which requires an intensive care setting. Analgesia – a nesthesia for p re - eclampsia The use of conduction anesthesia in pre - eclampsia was, at one time, controversial. Concerns have been voiced by some authors that the sympathetic blockade and peripheral vasodilation result- ing from epidural anesthesia may lead to hypotension and fetal distress in patients who are already volume contracted [3,86,165] . However, induction of general endotracheal anesthesia is not without its own inherent risks. General anesthesia has been shown to result in signifi cant rises in systemic arterial pressure in patients with severe pre - eclampsia. An average increase in systolic arterial BP of 56 mmHg during endotracheal intubation of 20 patients with hypertension was reported by Connell et al. [166] . Hodgkinson et al. [167] evaluated 10 severe pre - eclamptic – eclamptic patients undergoing general anesthesia using the pulmonary artery catheter. They noted severe systemic and pulmonary hypertension during endotracheal intubation and rapid decrease in BP via decreased SVR in patients with severe hypertension [143] . Reports on the effi cacy and safety of labetalol in the treatment of hypertension during pregnancy have been favorable ( [144 – 150] . Mabie et al. [149] compared bolus intrave- nous labetalol with intravenous hydralazine in the acute treat- ment of severe hypertension. They found that labetalol had a quicker onset of action and did not result in refl ex tachycardia. Labetalol also may exert a positive effect on early fetal lung matu- ration in patients with severe hypertension who are remote from term [145,151] . An initial dose of 10 mg is given and is followed by progressively increasing doses (20, 40, 80 mg) every 10 minutes, to a total dose of 300 mg. Alternately, constant intravenous infu- sion may be started at 1 – 2 mg/min until therapeutic goals are achieved, then decreased to 0.5 mg/min or completely stopped [121] . Lunell et al. [152] studied the effects of labetalol on utero- placental perfusion in hypertensive pregnant women and noted increased uteroplacental perfusion and decreased uterine vascu- lar resistance. Morgan et al. [153] evaluated the effects of labetalol on uterine blood fl ow in the hypertensive gravid baboon and found that low doses (0.5 mg/kg) signifi cantly reduced MAP without adversely affecting uterine blood fl ow. Belfort et al. have shown that labetalol has a favorable profi le in terms of its cerebral hemodynamic effects. It reduces elevated cerebral perfusion pres- sure while maintaining cerebral blood fl ow [154] . This may be important in its control of cerebral overperfusion and prevention of hypertensive encephalopathy and associated pathology. Nitroglycerin Nitroglycerin (Nitrostat IV, Nitro - Bid IV, Tridil) relaxes pre- dominantly venous but also arterial vascular smooth muscle, decreasing preload at low doses and afterload at high doses [155] . It is a rapidly acting potent antihypertensive agent with a very short hemodynamic half - life. Using invasive hemodynamic mon- itoring, Cotton et al. [131,156] noted that the ability to control BP precisely was dependent on volume status. Although larger doses of nitroglycerin were required following volume expansion, the ability to effect a smoother and more controlled drop in BP required prevasodilator hydration [156] . Nitroglycerin is admin- istered via an infusion pump at an initial rate of 5 µ g/min and may be doubled every 5 minutes. Methemoglobinemia may result from high - dose (7 µ g/kg/min) intravenous infusion. Patients with normal arterial oxygen saturation who appear cyanotic should be evaluated for toxicity, defi ned as a methemoglobin level greater than 3% [155] . Sodium n itroprusside Sodium nitroprusside (Nipride, Nitropress) is another potent antihypertensive agent that may be used to control severe hyper- tension associated with pre - eclampsia. A dilute solution may be started at 0.25 µ g/kg/min and titrated to the desired effect through an infusion pump by increasing the dose by 0.25 µ g/kg/min every 5 minutes. The solution is light sensitive and should be covered in foil and changed every 24 hours [157] . Arterial blood gases should be monitored for developing metabolic acidosis, which Chapter 34 446 in Table 34.9 . Hemodynamic fi ndings in non - pregnant women, normal third - trimester pregnancy, and severe pre - eclamptics are provided in Table 34.10 . Current indications for the use of a pulmonary artery catheter in pre - eclampsia are listed in Table 34.11 [132,174 – 176] . Routine use of the pulmonary artery catheter in uncomplicated severe pre - eclampsia is not recommended. In these cases, the potential morbidity of pulmonary artery catheterization does not appear to be justifi ed. Known complications of invasive monitoring at the time of insertion include cardiac arrhythmias, pneumotho- rax, hemothorax, injury to vascular and neurologic structures, pulmonary infarction, and pulmonary hemorrhage. Later com- plications include balloon rupture, thromboembolism, catheter knotting, pulmonary valve rupture, and catheter migration into the pericardial and pleural spaces, with subsequent cardiac tam- ponade and hydrothorax [177 – 179] . It should be noted, however, that Clark et al. [174] observed no signifi cant complications from pulmonary artery catheterization in a series of 90 patients who underwent the procedure on an obstetrics – gynecology service. A retrospective study of 115 pregnant women with severe pre - eclampsia and eclampsia managed by pulmonary artery catheter- ization concluded that catheterization was subjectively benefi cial in 93% of cases with an acceptable complication rate of 4% [180] . An alternate approach to the use of invasive monitoring is the use of echocardiography to determine central hemodynamic parameters [181 – 183] . In almost all cases of severe pre - eclampsia an initial echocardiogram will allow determination of cardiac function (cardiac output and ejection fraction), and central venous pressure. This is generally all that is needed to make the important clinical decisions regarding fl uid management and antihypertensive drug choice. It also allows rapid determination of cardiac function and the potential for hypertensive cardiomy- opathy and diastolic dysfunction – two important complications frequently seen in severe hypertension in pre - eclampsia. We have extubation. Ten patients undergoing epidural anesthesia with 0.75% bupivacaine for cesarean section maintained stable sys- temic and pulmonary arterial pressures, with the exception of one patient who developed systemic hypotension that responded promptly to ephedrine. Newsome et al. [75] demonstrated a drop in MAP and a slight but insignifi cant decrease in SVR without change in CI, periph- eral vascular resistance (PVR), central venous pressure (CVP), or PCWP in 11 patients with severe pre - eclampsia undergoing lumbar epidural anesthesia. Jouppila et al. [73] measured inter- villous blood fl ow in nine patients with severe pre - eclampsia during labor with lumbar epidural block and found a signifi cant increase in uterine blood fl ow. Ramos - Santos et al. [168] studied the effects of epidural anesthesia on uterine and umbilical artery blood fl ow by way of Doppler velocimetry in mild pre - eclamptics, chronic hypertensives, and normal controls during active term labor. In the pre - eclamptic group, the uterine artery systolic/ diastolic ratios decreased to levels similar to those of the control group, suggesting a possible benefi cial effect in reducing uterine artery vasospasm. Deleterious hypotension may be avoided by lateral maternal tilt, thus preventing aortocaval occlusion, and preloading with crystalloid solution to compensate for peripheral vasodilation [73] . Contraindications to epidural anesthesia include patient refusal, fetal distress requiring immediate delivery, local infec- tion, septicemia, severe spinal deformities, and coagulopathy [74] . If preceded by volume loading, epidural anesthesia appears benefi cial and safe in severe pre - eclampsia [70 – 75,132] . Clark and Cotton [132] state, “ In skilled hands, a cautiously adminis- tered epidural anesthetic is, in our opinion, not only justifi ed, but the method of choice for anesthesia in cesarean section or for control of the pain of labor in the patient with severe pre - eclamp- sia. ” The safety and effi cacy of neuraxial analgesia for severe pre - eclamptics appears to be well supported by recent studies [169,170] ). When general anesthesia is necessary, careful control of maternal BP, especially around the time of induction and awakening, is essential. Small doses of nitroglycerin or other similar agents are often useful in this regard. Hemodynamic m onitoring for p re - eclampsia The pulmonary artery catheter, introduced over 30 years ago, has been very useful in the management of critically ill patients [171] . In cases of severe pre - eclampsia, most clinicians have obtained excellent results without invasive monitoring [69] . Protocols developed to study the central hemodynamic parameters of severe pre - eclampsia have revealed interesting data, which are sometimes confounded by differences in clinical patient manage- ment prior to and at the time of catheterization [70] . Hemodynamic changes observed in normal pregnancies and pregnancies complicated by hypertension are summarized by Dildy and Cotton [172,173] . Central hemodynamic fi ndings in severe pre - eclampsia are summarized by Clark and Cotton [132] Table 34.9 Hemodynamic fi ndings in severe pregnancy - induced hypertension. Cardiac output is variable Mean arterial pressure is elevated; systemic vascular resistance is normal (early) or elevated (late) Central venous pressure is usually low to normal and does not correlate with pulmonary capillary wedge pressure Pulmonary hypertension and pulmonary vascular resistance are not present, but low pulmonary artery pressure may occur in the presence of hypovolemia Pulmonary capillary wedge pressure may be low, normal or high Oliguria may not refl ect volume depletion Ventricular function is usually hyperdynamic, but may be depressed in the presence of marked elevation in systemic vascular resistance Colloid oncotic pressure is usually low Reproduced with permission from Clark SL, Cotton DB. Clinical indications for pulmonary artery catheterization in the patient with severe preeclampsia. Am J Obstet Gynecol 1988; 158: 453 – 458. Complications of Pre-eclampsia 447 Table 34.10 Hemodynamic profi les of non - pregnant women, normal women during the late third trimester, and severe pre - eclamptics. Normal Normal late non - pregnant (n = 10) * (mean ± SD) Normal/late third trimester (n = 10) * (mean ± SD) Severe pre eclampsia (n = 45) † (mean ± SEM) Severe preeclampsia (n = 41) ‡ (mean ± SEM) Heart rate (beats/min) 71 ± 10 83 ± 10 95 ± 2 9 4 ± 2 Systolic blood pressure (mmHg) N/A N/A 193 ± 3 175 ± 3 Diastolic blood pressure (mmHg) N/A N/A 110 ± 2 106 ± 2 Mean arterial blood pressure (mmHg) 86.4 ± 7.5 90.3 ± 5.8 138 ± 3 130 ± 2 Pulse pressure (mmHg) N/A N/A 84 ± 2 7 0 ± 2 Central venous pressure (mmHg) 3.7 ± 2.6 3.6 ± 2.5 4 ± 1 4.8 ± 0.4 Pulmonary capillary wedge pressure (mmHg) 6.3 ± 2.1 7.5 ± 1.8 10 ± 1 8.3 ± 0.3 Pulmonary artery pressure (mmHg) 11.9 ± 2.0 § 12.5 ± 2.0 § 17 ± 1 1 5 ± 0.5 Cardiac output (L/min) 4.3 ± 0.9 6.2 ± 1.0 7.5 ± 0.2 8.4 ± 0.2 Stroke volume (mL) N/A N/A 79 ± 2 9 0 ± 2 Systemic vascular resistance (dynes · sec · cm − 5 ) 1530 ± 520 1210 ± 266 1496 ± 64 1,226 ± 37 Pulmonary vascular resistance (dynes · sec · cm − 5 ) 119 ± 47 78 ± 22 70 ± 5 6 5 ± 3 Serum colloid osmotic pressure (mmHg) 20.8 ± 1.0 18.0 ± 1.5 19.0 ± 0.5 N/A Body surface area (m 2 ) N/A N/A N/A N/A Systemic vascular resistance index (dynes · sec · cm − 5 · m 2 ) N/A N/A 2726 ± 120 2,293 ± 65 Pulmonary vascular resistance index (dynes · sec · cm − 5 · m 2 ) N/A N/A 127 ± 9 121 ± 7 Right ventricular stroke work index (g · m · M − 2 ) N/A N/A 8 ± 1 1 0 ± 0.5 Left ventricular stroke work index (g · m · M − 2 ) 41 ± 8 4 8 ± 6 8 1 ± 2 8 4 ± 2 Cardiac index (L · min − 1 · m 2 ) N/A N/A 4.1 ± 0.1 4.4 ± 0.1 Stroke volume index (mL · beat · m 2 ) N/A N/A 44 ± 1 4 8 ± 1 COP – PCWP (mmHg) 14.5 ± 2.5 10.5 ± 2.7 N/A N/A Data from * Cotton et al. [176] , † Clark et al. [195] , ‡ Mabie et al. [318] ; § Clark et al., unpublished data . N/A, not available; SD, standard deviation; SEM, standard error of the mean. Table 34.11 Indications for use of pulmonary artery catheter in pregnancy - induced hypertension. Complications related to central volume status Pulmonary edema of uncertain etiology Pulmonary edema unresponsive to conventional therapy Persistent oliguria despite aggressive volume expansion Induction of conduction anesthesia in hemodynamically unstable patients Medical complication that would otherwise required invasive monitoring found that this approach is very useful and in all but the most severe cases allows non - invasive management and avoids the need for a pulmonary artery catheter. Cardiopulmonary c omplications of p re - eclampsia During normal pregnancy, plasma volume increases approxi- mately 42% while red blood cell volume increases approximately 24% [184] . Earlier studies of cardiovascular changes in pre - eclampsia revealed increased vascular resistance, decreased circu- latory volume, and decreased perfusion of various organ systems, most notably the renal and uteroplacental circulations, when compared with normal non - pregnant subjects [17,185] , In preg- nancies complicated by pre - eclampsia, a reduction in plasma volume with hemoconcentration occurs in proportion to the severity of the disease [184] . Signifi cant plasma volume depletion and reduction in circulating plasma protein may occur prior to the clinical manifestations of pre - eclampsia [185 – 187] . In sub- jects who developed hypertension during pregnancy, various degrees of increased cardiac output (CO) and/or SVR were noted [188] . Although the precise cause of these changes remains unknown, further insight into the exact cardiovascular parameters associ- ated with pregnancy - related disease states evolved around 1980, when obstetric and gynecologic indications for use of the pulmo- nary artery catheter were described, and measurements of CVP, pulmonary artery pressure (PAP), PCWP, CO, and mixed venous oxygen became available [178] . Rafferty and Berkowitz [189] studied three pre - eclamptic patients with a pulmonary artery catheter and noted an increased Chapter 34 448 Clark et al. [195] documented for the fi rst time central hemo- dynamic parameters in normotensive late third - trimester preg- nant patients (see Table 34.10 ). They demonstrated that most reported patients with severe pre - eclampsia have SVR in the normal range for pregnancy, and that left ventricular function in normal pregnancy as assessed by LVSWI is not hyperdynamic. This supports the model of an initially hyperdynamic hyperten- sion without vasospasm in pre - eclampsia. This may be followed by the development of elevated SVR associated with vasospasm and a secondary decline in CO and LVSWI. Such a phenomenon has been documented in untreated non - pregnant patients with essential hypertension [196] . Pulmonary e dema Sibai et al. [197] reported a 2.9% incidence of pulmonary edema in severe pre - eclampsia – eclampsia; 70% of these 37 cases devel- oped postpartum. In 90% of the cases that developed antepar- tum, chronic hypertension was identifi ed as an underlying factor. A higher incidence of pulmonary edema was noted in older patients, multigravidas, and patients with underlying chronic hypertension. The development of pulmonary edema was also associated with the administration of excess infusions, either col- loids or crystalloids. Reduction of COP, alteration of capillary membrane permea- bility, and elevated pulmonary vascular hydrostatic pressures may lead to extravasation of fl uids into the interstitial and alveo- lar spaces, resulting in pulmonary edema [192] . Cotton et al. [127] observed a negative COP – PCWP gradient in fi ve pre - eclamptic patients who developed pulmonary edema. Interestingly, Clark et al. [175] compared the hemodynamic alterations in severe pre - eclamptics and eclamptics and suggested that the occurrence of eclamptic seizures may have also been associated with decreased COP rather than with the intensity of peripheral vasospasm. The etiology of pulmonary edema in pre - eclamptic patients appears to be multifactorial, as illustrated by Benedetti ’ s work involving 10 pre - eclamptic women with pulmonary edema [198] . Of these patients eight developed pulmonary edema in the post- partum period. Five patients had an abnormal COP – PCWP gradient, three demonstrated increased pulmonary capillary permeability, and two suffered left ventricular failure. Pulmonary edema secondary to capillary leak versus that due to increased hydrostatic pressure was distinguished by evaluating the ratio of edema fl uid protein to plasma protein [199] . The diagnosis of capillary leak was made in Benedetti ’ s study when the ratio of protein in pulmonary edema fl uid to serum protein was greater than 0.4 [198] . Again, CVP was found not to correlate with PCWP. A decreased COP – PCWP gradient has long been corre- lated with the development of pulmonary edema in non - preg- nant patients [199] . Pregnancy is known to lower COP, and COP is lower in pre - eclamptic patients than in normal pregnant patients. COP decreases further postpartum, secondary to supine positioning, bleeding at the time of delivery, and intrapartum infusion of crystalloid solutions [200] . In 50% of Benedetti ’ s left ventricular stroke index (LVSWI) and normal pulmonary artery resistance. At delivery, the CI and PCWP increased in these patients, probably secondary to increased venous return. These investigators noted an increased PCWP postpartum, which also was felt to be secondary to increased circulatory volume. These fi ndings suggest that the pulmonary vasculature is not involved in the vasospastic process and that pulmonary hypertension is not present in severe pre - eclampsia. Observations made from pulmonary artery catheterization in 10 patients with severe pre - eclampsia during labor showed an increased LVSWI (suggesting hyperdynamic ventricular function), normal PAP, and poor correlation between CVP and PCWP [190] . The poor correlation of PCWP and CVP has been verifi ed by subsequent investigations [127,158] . Hemodynamic studies have consistently demonstrated hyper- dynamic left ventricular function in pre - eclamptic patients [76,191,192] . Phelan and Yurth [191] studied 10 severe pre - eclamptics and noted hyperdynamic cardiac function with ele- vated CO and variable elevation of SVR. Immediately postpartum, a transient fall in left ventricular function with a rise in CVP and PCWP was noted in 6 of 10 patients, possibly secondary to an autotransfusion effect. Hyperdynamic ventricular function returned 1 hour postpartum. One criticism of this study as it related to CO is the fact that several of these patients received intrapartum hydralazine, which could account for the elevated CO. Groenendijk et al. [193] noted a low CI, low PCWP, and high SVR in pre - eclamptics prior to volume expansion. Volume expansion resulted in an elevation of PCWP and CI to normal pregnant values, a drop in SVR, and no change in BP. Vasodilation using hydralazine then resulted in a further drop in SVR and BP, with a rise in CI, and no change in PCWP. Eclamptics studied by Hankins et al. [194] initially demon- strated hyperdynamic left ventricular function and elevated SVR, as well as low right and left ventricular fi lling pressures. Following labor management, consisting of fl uid restriction, magnesium sulfate, and hydralazine, the authors observed a postpartum rise in PCWP in patients who did not have an early spontaneous diuresis. This rise in PCWP was thought to be secondary to mobi- lization of extravascular fl uids before the diuresis phase. They concluded that the hemodynamic status was infl uenced by the severity and duration of the disease, other underlying disease states, and therapeutic interventions such as epidural anesthesia. Cotton et al. [176] summarized the hemodynamic profi le in 45 patients with severe pre - eclampsia or eclampsia. They observed a wide variety of hemodynamic measurements in these patients; however, the majority were found to have an elevated BP, variably elevated SVR, hyperdynamic left ventricular function, normal to increased PCWP, and low CVP. They hypothesized that the ele- vated PCWP with decreased CVP was secondary to elevated left ventricular afterload, combined with a hypovolemic state. These fi ndings are summarized in Table 34.9 . . monitoring; potential cyanide toxicity Modifi ed from Dildy GA, Cotton DB. Hemodynamic changes in pregnancy and pregnancy complicated by hypertension. Acute Care 1988 – 89; 14 – 15: 26 – 46. Complications. furosemide daily for 5 days with 20 mEq per day of oral potassium supplementation) versus no furosemide therapy, after spontaneous onset of postpartum diuresis and discontinu- ation of intravenous. by volume preloading to avoid maternal hypotension [71 – 75] . Likewise, severely hypertensive patients receiving vasodilator therapy may require careful volume preloading to prevent an excessive