102 SECTION II Pediatric Critical Care Tools and Procedures to acute blood loss Cardiac tamponade can occur when the cath eter perforates within the pericardial reflection Undesirable posi tioning of[.]
102 S E C T I O N I I Pediatric Critical Care: Tools and Procedures to acute blood loss Cardiac tamponade can occur when the catheter perforates within the pericardial reflection Undesirable positioning of a central venous line can be detected radiographically and should be corrected as soon as possible.78,79 Peripherally Inserted Central Venous Catheters Clavicle Subclavian vein Sternal notch • Fig 14.5 Approach to the subclavian vein The patient is supine, in slight Trendelenburg position, with a small roll along the spine between the shoulders The needle enters the skin at the junction of the lateral and middle thirds of the inferior clavicle and is directed toward the suprasternal notch, passing along the inferior edge of the clavicle Inguinal ligament Femoral nerve Femoral artery Femoral vein Peripherally inserted CVCs (PICCs) are used with increasing frequency in PICU patients For infants and smaller children, often only a single-lumen catheter can be placed Multilumen catheters may be placed in older children Although PICC lines can often be placed by visualization or palpation of veins in the antecubital fossae, ultrasound is frequently used to place these catheters proximal to the antecubital fossa Success is more frequent when the catheters are inserted in the basilic vein.80 PICC lines are most often constructed of soft silicone or plastic polymer The catheter length is measured before catheter insertion, and the catheter is trimmed to the appropriate length Placement of PICC lines is most commonly performed using a modification of the Seldinger technique A needle or catheter is inserted into the vein; then, a guidewire is placed, followed by a dilator A soft peel-away introducer is often inserted next, with the catheter inserted through the introducer sheath The sheath is peeled away after the catheter is in place Outside of interventional radiology suites, chest radiography remains the primary method for documenting the location of the catheter tip While PICC lines are popular and associated with a lower risk of placement-related complications, they are subject to the same complications as CVCs, including catheter-associated infection, frequent thrombosis, perforation, embolization, and fracture.81–84 Recent data in adults demonstrate a very high incidence of catheter-related thrombosis when the catheter exceeds 45% of the vessel diameter, although pediatric data are lacking.85 PICC lines are associated with added thrombosis risk when compared with other types of CVCs in children The associated thrombotic complications can ultimately limit vascular access options in chronically ill children Ultrasound-Assisted Peripheral Venous Access Right leg • Fig 14.6 Approach to the femoral vein The patient is flat and supine, with the thigh slightly abducted and externally rotated The introducer needle enters the skin to cm distal to the inguinal ligament and 0.5 to cm medial to the pulse of the femoral artery result in pelvic or retroperitoneal bleeding Lacerations of the jugular, subclavian, or innominate veins or superior vena cava may result in hemothorax Bleeding complications are more severe in the presence of a coagulopathy or thrombocytopenia If possible, these should be treated before and/or during central vein access attempts.78,79 A CVC positioned where it applies pressure to the wall of a vessel or the heart increases the risk of perforation, which can lead Ultrasound-assisted peripheral venous access is increasingly used for challenging venous access situations given the availability of point-of-care ultrasound in critical care settings Ultrasound facilitates visualization of deeper veins that may not be readily found using inspection and palpation and can be used as a dynamic technique to guide catheter placement in real time This technique requires operator training and experience—like most procedures, its success improves with increasing operator experience Studies comparing the success of this technique to conventional peripheral venous access have yielded mixed results Venous Cutdown With the widespread use of central venous access and IO access during emergencies, venous cutdown is rarely performed Venous cutdown is indicated when percutaneous access is not achievable and the need for IV access warrants a more invasive approach Materials needed depend on the technique used for vein cannulation As with percutaneous CVC placement, the skin should be prepped and draped, and aseptic technique should be used A skin incision is made perpendicular to the vein The tissue surrounding the vein is bluntly dissected to completely expose the vein CHAPTER 14 Pediatric Vascular Access and Centeses 103 Supplies and Equipment Distal ligature Venotomy Proximal ligature • Fig 14.7 Venous cutdown Ligatures are passed around the vein, distal and proximal to the intended site of cannulation A small venotomy is created; using the ligatures to control the vein, a catheter is directly passed into the lumen of the vein The distal ligature can be tightened to control bleeding, while the proximal ligature helps secure the catheter (Fig 14.7) Alternatively, an over-the-needle IV catheter can be directly introduced into the exposed vein without venotomy Finally, the Seldinger technique can be used, in which an introducer needle and guidewire are inserted into the lumen of the exposed vein, followed by catheter placement over the wire This approach is particularly useful for femoral venous cutdown After the catheter is in place, it is secured with suture, and the wound is closed around the catheter The complications of venous cutdown are similar to those seen in other venous access techniques There is a risk of bleeding from the open wound, especially in patients with coagulopathy or systemic anticoagulation The open wound also increases the risk of infection Injury to adjacent structures, such as arteries and nerves, during incision and blunt dissection is another risk with cutdown.64,86,87 Umbilical Arterial Catheter and Umbilical Venous Catheter Placement Umbilical vein cannulation was first described in 1947 for an exchange transfusion in an infant with severe indirect hyperbilirubinemia.88 Umbilical artery cannulation was later described in 1959 for blood gas sampling.88 Since the early 2000s, umbilical arterial catheter (UAC) and umbilical venous catheter (UVC) placement have become routine procedures in the neonatal intensive unit (NICU).89 The UAC is indicated for frequent blood sampling, continuous measurement of blood pressure, and exchange transfusion.89,90 The UVC is used for administration of fluids, parenteral nutrition, and blood products.89,90 However, the advantages of these lines must be carefully balanced against the potential risks.91,92 Several life-threatening complications have been associated with the use of these catheters.91,92 As many neonates admitted to PICUs are older than a few days of age, this procedure is of limited value for most pediatric intensivists but can be very useful in the first few days of life Prepackaged umbilical catheter insertion trays are commercially available and contain different sizes of catheters The 3.5 Fr and Fr are the most frequently used catheters.89,90 Umbilical catheters are typically made of polyvinylchloride and have a single end hole, as side hole catheters have been linked with higher incidence of thrombosis.93,94 Umbilical catheters are available as single or multiple lumens A single lumen can be used in either vessel, whereas a double- or triple-lumen catheter is used exclusively in the umbilical vein.95 More than one lumen allows the administration of incompatible fluids A 3.5 Fr catheter is used for infants weighing ,1500 g, and a Fr catheter is used for larger infants.89,90 Technique The infant is kept in a supine position by using soft restraints of the arms and legs or via a swaddling technique A catheter is prepared for insertion by connecting to a Luer-Lok stopcock and flushing with saline, with or without heparin The umbilical stump and surrounding skin are thoroughly cleansed with 2% chlorhexidine or povidone-iodine.89,96 The antiseptic agent is allowed to dry and is then removed with sterile saline The area is draped, sparing the head and chest to allow for appropriate patient monitoring A cord tie is applied around the umbilical stump Using a scalpel, the cord is horizontally cut to cm above the umbilical ring.96 The larger, single thin-walled umbilical vein is typically located at the 12 o’clock position, whereas the two thick-walled generally constricted umbilical arteries are identified at the and o’clock positions.96 A single umbilical artery is sometimes isolated and can be a normal variation.89,96 Umbilical Arterial Cannulation Once the umbilical artery is identified, the iris forceps is used to gently dilate the arterial lumen by first inserting the forceps in the closed position and subsequently allowing both prongs to spring open and dilate the lumen.89,90 The catheter is introduced 0.5 cm in the lumen of the vessel.89,90 Thereafter, the umbilical cord is pulled toward the infant’s head before further advancing the catheter The direction of the catheter advancement is caudal.97 The catheter enters the umbilical artery, passes through the right internal iliac artery, the right common iliac artery, and, finally, the descending aorta.97 Resistance to catheter advancement is occasionally encountered secondary to vasospasm, at the junction of the umbilical artery and fascial plane, or at the level of the bladder Gentle pressure can be applied Sometimes, the catheter can cross the wall of the umbilical artery, creating a false lumen A double-catheter technique can then be attempted.98 The first misdirected catheter follows a path of least resistance A second catheter is also used to bypass this pathway and then enters the aorta.98 If this technique fails, the second umbilical artery is cannulated The patency of the catheter is verified by easy blood aspiration and flushing The catheter is sutured in place, using a purse string stitch cinched tightly to provide hemostasis and wrapping both ends of the suture around the catheter before tying a square knot The line is further secured using a tape bridge or other available stabilization device.99 The umbilical tie is loosened and kept in place for any needed hemostasis A transducer can be attached for continuous blood pressure monitoring while still allowing blood sampling.100 104 S E C T I O N I I Pediatric Critical Care: Tools and Procedures Two lengths of UAC insertion are described in the literature.101–103 Low or high placement of the catheter is based on the vertebral level at which the catheter tip resides in the aorta.97,101–103 Low placement is defined as the catheter tip caudal to the origins of the renal arteries, whereas a high placement is described as the catheter tip in the descending aorta above the diaphragm and below the left subclavian artery.97,101–103 A Cochrane review evaluated the effects of the position of UACs and concluded that high-placed catheters led to fewer clinical vascular complications.104 Although reference charts based on patient morphometrics are available, there are simple formulas that predict the depth of insertion of arterial catheter.101–103 Shukla’s regression equation based on birth weight (BW) predicts UAC insertion length (cm) as (3 BW (kg) 9) for infants weighing 1500 g or more, whereas Wright’s formula (4 BW [kg] 7) results in more accurate UAC placement (cm) for infants weighing less than 1500 g.102,103 Umbilical Venous Cannulation Once the umbilical vein is identified, a catheter is introduced carefully in the lumen The umbilical vein does not always require routine dilation prior to the introduction of the catheter.89,90,96 The umbilical cord is gently pulled toward the feet during placement to straighten the course of the vein The direction of the catheter advancement is cephalad A properly placed UVC resides at the inferior vena cava–right atrial junction via the umbilical vein and the ductus venosus.105 Sometimes, the catheter is misdirected into the portal, splenic, or mesenteric vein If there is resistance to insertion or poor blood return, inappropriate position of the catheter should be suspected The double-catheter technique, described in the UAC section, can also be used in UVC placement.105 The patency of the catheter is then verified by adequate blood return and flushing The line is secured using the same technique described for UACs The length of inserted catheter is determined by the size of the infant and indication for placement.89,102,105 In emergency situations, the catheter is advanced to a depth where rapid blood return is achieved (2–4 cm in most infants) A long-term UVC resides at the junction of the inferior vena cava and right atrium The two most commonly used methods to predict accurate depth of UVC are nomograms based on the measurement of the shoulder-umbilicus length and regressions equations based on BW.101,102 Shukla’s formula, ([3 BW (kg) 9]/2) 1, is widely used to estimate the length of UVC insertion (cm).102 Verheij suggested that Shukla’s formula leads to overinsertion of catheters and recommended a revised formula, (3 BW [kg] 9)/2.106 Proper Placement of Umbilical Arterial and Venous Catheters Anteroposterior and lateral views of a thoracoabdominal radiograph are required to confirm proper placement of the catheters Low UAC placement correlates with the third and fourth lumbar vertebrae on chest film, whereas a high placement correlates with the sixth and tenth thoracic vertebrae.107 UVC tip should be positioned at or just above the diaphragm or between the eighth to tenth vertebrae Several studies have questioned the optimal diagnostic approach to determine the correct position of the umbilical catheters.107 Questions were raised on the difficulty of relating anatomic structures to the projection of vertebral bodies on radiographs secondary to the variability of these structures in relation to bony landmarks Bedside ultrasonography is suggested as a better modality for verifying the position of the umbilical catheters.107 However, the disadvantage of this technique is the constant need for qualified personnel to perform the study at the time of the catheter’s placement Owing to this limitation, most centers still rely on radiography to assess catheter position Maintenance Infants are typically placed in the supine position or on their sides A dressing should not be applied to the umbilicus so that the catheter insertion site can be easily inspected.89,90,96 The UVC is maintained as part of a closed system to prevent air embolism A continuous infusion is needed to keep the lumen of the UAC clear, and the catheter is flushed after blood draws to minimize clot formation Continuous fluid infusion containing heparin is needed in the arterial line.108 The composition of the heparincontaining fluid varies by institution and is influenced by gestational age and electrolyte status A typical infusion includes 38 to 77 mEq/L sodium chloride or sodium acetate or an isotonic amino acid solution with heparin U/mL.97,109 Removal Umbilical catheters are removed one at a time Each catheter is pulled to approximately cm, then the catheter is slowly withdrawn in increments of cm/min.97 This process is especially important during the removal of UACs because it allows the artery to spasm and provide hemostasis If bleeding occurs, pressure is applied by elevating and pinching the skin just above the cord for venous bleeding or below the cord for arterial bleeding A hemostat can also be used to pinch the lumen of the vessel for persistent bleeding.89,97 Complications Umbilical venous and arterial cannulations are associated with potential complications These complications are related to placement and malposition of the catheters or prolonged catheter placement in the umbilical vessel Umbilical Arterial Cannulation Several complications are linked to UAC placement and catheter tip position Trauma to the vessel, leading to hemorrhage, can occur during placement Vasospasm of the umbilical artery with resulting blanching or cyanosis of the toes, feet, or buttocks has been described.110,111 Warming of the unaffected limb may improve perfusion of the other extremity Otherwise, catheter removal is warranted to prevent ischemic complication.90,110,111 Other complications include peritoneal perforation, bladder injury, catheter fracture, intravascular knots of catheters, or catheterization of the urachus, resulting in urinary ascites.90,110,111 Additional complications can develop with prolonged indwelling of the UAC McAdams and colleagues investigated the effects of UAC placement in an animal model and concluded that thrombus formation was detected in 80% of aortic sections.112 In addition, the incidence of developing aortic thrombus increases proportionally to the duration of UAC placement and has been reported as 16% within day, 32% within days, and 80% within 21 days of UAC placement The presentation of emboli ranges from asymptomatic to limb-threatening ischemia or mesenteric artery occlusion with necrotizing enterocolitis or renal CHAPTER 14 Pediatric Vascular Access and Centeses artery occlusion with renal failure and hypertension.90,110–112 Furthermore, once the intima of the vessel has been traumatized, the vessel becomes susceptible to infection In most instances, the microorganisms are coagulase-negative staphylococci These pathogens produce a biofilm that preferentially adheres to irregular catheter surfaces.113 Catheter-related infection may also cause aortic aneurysm.92 The Centers for Disease Control and Prevention (CDC) reaffirmed in 2011 that UACs should be removed as soon as possible and should not be kept longer than days— sooner if signs of vascular insufficiency occur.113 Umbilical Venous Cannulation A common complication of UVC placement is catheter tip malposition A low-positioned UVC within the confluence of the portal circulation may precipitate hepatic injury.91 Clinical features of liver complications vary and can be asymptomatic or present as abdominal distension with hepatomegaly, hypotension, worsening respiratory status, or portal thrombosis with chronic portal hypertension A catheter tip in the right atrium can also result in pericardial effusion and tamponade.114 Complications related to prolonged UVC cannulation include sepsis and thrombosis.115 Multiple interventions are recommended to prevent central line–associated bloodstream infection and include limiting central line access for injecting medications, enforcing hub disinfection before accessing the central line, and replacing UVCs as soon as possible with PICCs.113 The CDC has recommended removal of UVCs as soon as possible when no longer needed, but this could be extended up to 14 days if managed aseptically.113 Interestingly, Butler-O’Hara and colleagues completed a randomized controlled trial that showed similar infection rates with UVCs left in place up to 28 days compared with UVCs replaced by PICCs after to 10 days.116 However, the same authors later published a quality improvement project revealing a greater risk of infection with long-term compared with short-term UVC followed by PICC placement.117 The authors concluded that the substantial decrease in PICC infection rates in their unit altered the risk-benefit ratios between the two strategies (short and long term) of UVC use Summary Umbilical lines are commonly used in the care of severely ill neonates The use of UACs for blood collection and blood pressure monitoring and the use of UVCs for nutrition or medications have become commonplace in NICUs and can also be used in the PICU Although there are several benefits to their use, umbilical catheters are associated with potential problems An awareness of the possible complications is important to minimize serious consequences and provide timely interventions Pulmonary Artery Catheterization Pulmonary artery catheter (PAC) monitoring was introduced into practice in 1970 by Swan and Ganz (see Chapters 26, 27, and 30) However, because of the invasiveness of the procedure and lack of a proven survival benefit for patient management, other less invasive surrogate techniques have significantly decreased the use of the PAC.118–121 Placement of the catheter can be performed at the bedside, but skill and experience in the placement, management, and data acquisition are required to avoid complications and for proper interpretation of the hemodynamic data Most catheters are balloon 105 tipped and flow directed They are able to measure right atrial, pulmonary artery, and pulmonary capillary wedge pressures as well as determine cardiac output and oxygen saturations in the right heart chambers Single-lumen catheters may be placed directly into the pulmonary artery at the time of cardiac surgery Both techniques are used in pediatric patients, but the singlelumen catheter is most frequently employed because of the frequency of pulmonary hypertension complicating the postoperative management of pediatric cardiac patients The flowdirected, balloon-tipped catheter is usually placed in the ICU to assist in determining the etiology of shock, pulmonary edema, and pulmonary hypertension, as well as to help guide fluid and vasoactive-inotropic therapy over time The PAC should not be used for the routine care of ICU patients, but it may be useful in heart failure patients with persistent symptoms despite standard measures, in patients undergoing heart transplantation evaluation, and for patients with pulmonary hypertension.120,121 Pulmonary hypertension may either be primary or secondary, the latter including pulmonary hypertension in postoperative congenital cardiac patients These patients are prone to wide swings in pulmonary artery (PA) pressures associated with variations in oxygenation, ventilation, and sedation level When inhaled nitric oxide is used to manage postoperative pulmonary hypertension, direct measurement of PA pressure helps guide titration of therapy In patients with severe respiratory failure requiring high positive airway pressure with associated hemodynamic compromise, PACs may facilitate diagnosis of low cardiac output and direct therapy When Do2 in such patients is significantly limited because of hypoxemia, low cardiac output, or both, measurement of Do2 using variables derived from information provided by the catheter may be useful In children with severe shock unresponsive to fluid resuscitation and requiring vasoactive-inotropic infusions, the PAC may better define the hemodynamic profile, thus directing more specific therapy Significant controversy exists regarding the benefits and potential harms caused by this invasive form of hemodynamic monitoring.120–122 An older multicenter observational study reported increased mortality with PACs Subsequently, several randomized clinical trials failed to demonstrate a benefit to PAC-guided therapy Some studies reported an association with increased morbidity and mortality,119 whereas others did not find differences with or without PACs.122 No studies in children have demonstrated better outcomes with the use of the PAC monitoring Multiple barriers exist to PAC use, including patient risk with placement, the ability to measure similar variables via less invasive measures, increased cost, inaccurate measurement leading to misuse of PAC-derived variables, and incorrect interpretation and clinical application Additionally, with the decreased use of this technology, the skill required to maintain competency in placement and interpretation of the data provided presents a significant challenge to many institutions Contraindications There are no specific contraindications to placement of a PAC, but there are several relative contraindications, including bleeding diathesis, which increases the risk for percutaneous access, and severe tricuspid or pulmonary insufficiency, which can make bedside catheter placement prohibitively difficult Unstable cardiac arrhythmias that are easily triggered by catheter manipulation are also a relative contraindication Catheter placement for measurement of cardiac output using the thermodilution technique is 106 S E C T I O N I I Pediatric Critical Care: Tools and Procedures contraindicated in the presence of intracardiac shunts, tricuspid insufficiency, or pulmonary insufficiency, as the thermodilution measurement will be inaccurate Procedure and Equipment Balloon-tipped, flow-directed catheters are available with two diameters, Fr and Fr The Fr diameter catheter is most appropriate for patients weighing less than 15 kg; the Fr diameter catheter is best for patients weighing more than 15 kg Some PACs employ fiberoptic spectrophotometry for continuous measurement of mixed venous oxygen saturation Single-lumen PACs are most commonly placed in the operating room at the time of heart surgery The standard PAC is m long The PAC is equipped with proximal and distal ports facilitating measurement of intravascular pressures, infusion of vasoactive agents, fluids, and blood sampling The distance between the proximal and distal lumen ports varies depending on the catheter: standards are 10, 15, 20, and 30 cm Choosing the catheter with the correct lumen distances is crucial in order to monitor the appropriate pressure At the tip are a thermistor used to calculate cardiac output and a balloon that may be inflated and deflated as necessary Some catheters have an additional right ventricular port for temporary pacemaker insertion, and some have the fiberoptic oxygen saturation sensor for continuous measurement of mixed venous oxygen saturation Other necessary pieces of equipment are a monitor with cardiac output capability or a computer to determine cardiac output using thermodilution and compatible pressure transducers Carbon dioxide is used in some centers to inflate the balloon to minimize the risk of air embolization, although room air is most commonly used The catheters are placed through a percutaneous introducer sheath, which is placed with the same technique as described for CVCs Before placement, the catheter should be flushed and filled with fluid through which intravascular pressures are transmitted to a transducer The equipment is then zeroed to atmospheric pressure at the level of the patient’s left atrium (midaxillary line, fourth intercostal space) and calibrated If all air bubbles are not removed from the tubing, they may result in damping of the waveform tracing and, consequently, erroneously low systolic pressure Thrombus at the tip of the catheter may also alter the waveform (see also Chapter 26) The insertion site is prepared in sterile fashion with chlorhexidine solution and draped with sterile towels It is important to drape a wide area with sterile sheets (full field barrier drape) in order to avoid exposure of the catheter, because of the length of the PAC The PAC is inserted through the introducer sheath A sterile sleeve is placed on the end of the sheath, and the catheter is passed through the sleeve, then through the introducer diaphragm and into the sheath Anatomically, the preferred sites of insertion are the right internal jugular, left subclavian, right subclavian, and left internal jugular veins Usually, the placement of the catheter is guided by pressure waveform monitoring, but fluoroscopic visualization will occasionally be needed, particularly if the PAC is placed from a femoral site Once the catheter tip enters the venous circulation, the balloon is inflated with air From this point, the catheter should be advanced with the balloon inflated to prevent damage to the myocardium, cardiac valves, or pulmonary artery branches If the catheter is withdrawn, the balloon must first be deflated to avoid valvular injury The catheter is advanced to the right atrium (RA), then across the tricuspid valve into the right ventricle (RV), and across the pulmonary valve into the PA As the catheter continues to float with the balloon inflated, it will wedge in a branch PA, occluding the blood flow The pulmonary artery occlusion pressure (PAOP), or pulmonary artery wedge pressure (PAWP), will be recorded from the distal lumen If the balloon is deflated, a PA pressure tracing will be recorded If the waveforms are not obtained, the balloon should be deflated, and the catheter pulled back to the RA before attempting placement again After insertion, a chest radiograph is obtained to ensure proper catheter placement and rule out pneumothorax The catheter tip should be visualized within West zone III of the lung ideally (see Chapters 26, 42, and 43) The pressure waveforms are characteristic; when the catheter is advanced to the RA, the atrial trace has a respiratory variation that helps to confirm that the catheter is in the thorax Once in the atrium, the balloon is inflated and advanced to the RV, where the trace is characterized by a rapid upstroke in early systole with an equally rapid downstroke at the end of systole and diastolic pressure near zero Turning the catheter with a clockwise motion usually helps in advancing the PAC The catheter is advanced to the PA The PA trace has the same peak systolic pressure of the RV, but as systole ends, the trace shows a slower fall that continues through diastole, because the diastolic pressure in the PA is higher than the RV diastolic pressure Once in the PA, the catheter is advanced slightly until a pulmonary wedge trace is seen This trace is similar to the RA trace, although usually with a higher pressure PAWP is obtained when the balloon is inflated and the catheter floats into the wedge position Because the catheter floats to an area of greatest blood flow in the lung, it most likely will be in an area consistent with West zone III, where arterial pressure is higher than both venous and alveolar pressures Measurement of PAWP is best done at end expiration to minimize the effect of changes in pleural pressure Once the wedge is measured and the balloon is deflated, the PA trace should return If the trace does not change, the catheter should be retracted until the PA trace is seen The catheter should not be left inflated in the wedge position because of the risk of pulmonary infarction The catheter is appropriately positioned when the PA pressure trace is present when the balloon is not inflated and the pulmonary capillary wedge trace is present when the balloon is inflated Once it has been confirmed that the PAC is in good position by pressure trace and radiography, the catheter should be secured in the sleeve and taped to the patient PAC information acquisition and interpretation is detailed on ExpertConsult.com and in Chapter 26 Maintenance Care of the PAC is similar to that for any CVC The catheter and sheath should be dressed sterilely at all times, and the dressing changed according to protocol The catheter is housed in a sterile sleeve that allows for aseptic technique if further manipulation is necessary Pressure transduction of the distal (PA) and proximal (RA) ports and continuous electrocardiographic (ECG) monitoring are mandatory This setup continually confirms proper placement of the catheter Whenever the balloon is inflated to determine PAWP, the balloon is allowed to deflate passively by opening the balloon port and removing the syringe This step helps prevent balloon rupture Balloon rupture should be suspected if blood is obtained when aspirating the balloon port In this situation, ... proportionally to the duration of UAC placement and has been reported as 16% within day, 32% within days, and 80% within 21 days of UAC placement The presentation of emboli ranges from asymptomatic... follows a path of least resistance A second catheter is also used to bypass this pathway and then enters the aorta.98 If this technique fails, the second umbilical artery is cannulated The patency... catheters.107 However, the disadvantage of this technique is the constant need for qualified personnel to perform the study at the time of the catheter’s placement Owing to this limitation, most centers still