e86 SECTION XV Pediatric Critical Care Board Review Questions Rationale An increased heart rate and decreased blood pressure may reflect a negative heart lung interaction due to the positive airway pr[.]
e86 S E C T I O N XV Pediatric Critical Care: Board Review Questions Rationale An increased heart rate and decreased blood pressure may reflect a negative heart-lung interaction due to the positive airway pressure during NIV and should be avoided Abdominal paradox should be reduced with NIV, not increased Decreased retractions signify decreased work of breathing associated with NIV Chapter 56: Extracorporeal Life Support The major cardiac effects of venoarterial ECMO include: A Decreased preload and afterload B Decreased preload and increased afterload C Decreased preload and no effects on afterload D Decreased afterload and increased preload Preferred response: C Rationale As venoarterial ECMO removes venous blood from the right side of the heart, preload is decreased As the oxygenated return from the ECMO pump has to have a higher pressure than the systemic mean arterial fraction in the patient to provide forward flow into the patient, the afterload to the left heart is increased This is a major problem in VA ECMO in patients with left heart dysfunction, as the afterload increase can result in acute left ventricular failure, left atrial and pulmonary venous hypertension, pulmonary edema, or frank pulmonary hemorrhage In a 10-year-old patient with pneumonia and no evidence of hemodynamic compromise, the optimal mode of ECMO is: A Cervical venoarterial access B Double lumen venovenous access C Femoral venoarterial access D Venovenoarterial cannulation Preferred response: B Rationale While all these modes could potentially be used, a 10-year-old has a large enough internal jugular vein to consider using a double lumen cannula or any venovenous mode The important note is that the patient is hemodynamically stable, and thus native cardiac output should be able to propel oxygenated return from the right heart and left heart to the systemic circulation A 10-year-old with pneumonia and severe lung injury is on venovenous ECMO support via drainage of the femoral vein and reinfusion though the right internal jugular vein You are called because patient arterial saturations have declined from 92% to 84% Function and parameters in the ECMO circuit seem unchanged The patient’s heart rate has also increased from 90 beats per minute to 110 beats per minute His blood pressure has increased from 85/60 mm Hg to 98/67 mm Hg The best explanation for the decrease in patient oxygenation is: A Decreased native cardiac output B Increased native cardiac output C Increased recirculation of venovenous support D Pneumothorax Preferred response: B Rationale While pneumothorax and decreased cardiac output can affect venous return and thus reduce oxygenation to the patient, the fact that the ECMO circuit and parameters (venous saturation, flows) have not changed indicates that the reduction in systemic oxygenation is not likely due to the ECMO flow itself As the patient has poor native gas exchange, blood flowing through the native cardiopulmonary circuit will not have much additional oxygen added The fact that the patient’s cardiac output has increased (increased heart rate, increased blood pressure) at a constant ECMO flow would increase the mixture of desaturated blood from the patient’s pulmonary circuit and native output to mix with the oxygenated return from the ECMO circuit This will be demonstrated by a decrease in systemic pulse oximetry and arterial partial pressure of oxygen (Pao2), although overall oxygen delivery may still be adequate A 12-month-old child is on venoarterial ECMO support with a centrifugal pump for respiratory failure You notice that the patient’s arterial saturations are low Potential causes include: A Decrease in patient’s systemic vascular resistance B Increase in patient’s pulmonary vascular resistance C Increased recirculation into the ECMO circuit D Sudden increase in patient systemic vascular resistance Preferred response: D Rationale In venoarterial ECMO, recirculation should not occur An increase in the patient’s pulmonary vascular resistance should not affect any systemic arterial saturation A decrease in systemic vascular resistance should allow easier return of ECMO flow, and if settings are guided by revolutions per minute, more flow should be delivered, which should increase patient oxygenation An increase in the patient’s systemic vascular resistance will make it harder for the centrifugal pump to push oxygenated blood into the patient To improve oxygenation, the RPMs in the circuit should be increased or the patient’s blood pressure decreased A 6-month-old boy has been on venoarterial extracorporeal membrane oxygenation (ECMO) through the cervical vessels for days to treat respiratory failure associated with respiratory syncytial virus (RSV) pneumonia He was doing well until the venous return alarm on the ECMO circuit began to ring and circuit flow was interrupted He is now crying, and the venous line does not appear to be kinked His blood pressure, heart rate, and perfusion are normal What is the most likely cause of the alarm? A Hypervolemia after receiving blood B Hypovolemia related to capillary leak syndrome C Increased intrathoracic or intraabdominal pressure with crying D Pericardial tamponade Preferred response: C Rationale Increased intrathoracic or intraabdominal pressure will restrict venous return to the right atrium and thus decrease venous return to the ECMO circuit CHAPTER 136 Board Review Questions A patient on venovenous (VV) extracorporeal membrane oxygenation (ECMO) support has a mixed venous oxygen saturation reading on the ECMO circuit of 65% but is hypoxic with an arterial saturation of 72% Increasing the ECMO flow brings the venous saturation to 73%, but the patient’s arterial saturation does not improve What is the most likely cause of this response? A Hypovolemia B Loss of oxygen to the patient’s ventilator circuit C Recirculation of the VV circuit D Severe anemia Preferred response: C Rationale Increasing flow to the venovenous circuit can increase recirculation This means that oxygenated blood returning from the ECMO pump is drawn immediately back into the venous drainage cannula This will increase the saturation of oxygenated blood within the ECMO circuit and give a falsely high venous saturation reading in the circuit as compared to what the patient’s system is actually seeing The recirculated blood will not be delivered to the patient’s systemic circulation, and thus oxygen delivery and saturation will not improve Recirculation can sometimes be reduced by decreasing the ECMO flow and allowing more oxygenated blood to be delivered systemically Other measures to improve oxygenation include increasing oxygen content by hemoglobin transfusion; reducing oxygen extraction by correcting fever, pain, and the like; or increasing cardiac output from the patient by inserting another venous drainage cannula or converting to venoarterial support An 8-month-old girl born at 32 weeks’ gestation is placed on venovenous (VV) extracorporeal membrane oxygenation (ECMO) because of worsening pneumonia Her oxygen index on a highfrequency oscillator ventilator is greater than 60 An echocardiogram done prior to the initiation of ECMO showed normal cardiac function Which of the following best describes VV ECMO? A Myocardial stunning is a common feature B Native cardiac function is relied on for maintaining systemic circulation C Patients are at increased risk for cerebral and systemic emboli D Percutaneous cannulation of the internal carotid artery is common Preferred response: B Rationale VV ECMO differs from venoarterial ECMO in that blood is both withdrawn and reinfused into the patient’s venous circulation Cannulation can be introduced via either the cervical or the femoral vessels Several types of multiple lumens, single cannulas exist One, manufactured by Origen Inc is available in sizes from 12 to 18 French and can support a patient weighing up to 12 kg This cannula is placed into the right internal jugular vein and requires only one surgical site The drainage and infusion lumens in this cannula are separated by a distance of a few centimeters Careful placement and orientation of the cannula can reduce recirculation of reinfused blood from the ECMO circuit, although some amount of recirculation always occurs A new VV cannula manufactured by Avalon Laboratories Inc also has become e87 available in sizes from 13 to 31 French and is able to obtain flow rates to support even large adult patients This cannula has two drainage lumens, one that is positioned in the inferior vena cava and one positioned in the superior vena cava ECMO also can be provided via two (or more) separate access sites The right internal jugular vein and the femoral vein provide access in the majority of patients Patients with VV cannulation may have venous blood drained from the right atrium via the internal jugular vein or from the inferior vena cava via the femoral vein Because blood is both withdrawn and reinfused into the venous circulation, adequate native cardiac function must exist to provide the “pumping” of oxygenated ECMO return to the patient’s systemic circulation One factor that may influence cardiac function during VV ECMO is that well-oxygenated blood returning from the ECMO circuit will enter the right heart This highly oxygenated blood may reduce pulmonary artery pressure by reducing pulmonary vascular resistance, which may in turn improve right heart function Likewise, highly saturated blood ejected from the left ventricle to the coronary arteries may improve myocardial blood flow and cardiac performance For these reasons, some clinicians will initiate VV ECMO even in patients with cardiac dysfunction and transition to venoarterial ECMO if support is inadequate Other clinicians prefer to use venoarterial ECMO preferentially if cardiac dysfunction exists Another feature of VV ECMO is that because blood is withdrawn and reinfused into the venous side of the circulation, some of the return coming from the ECMO circuit will be drained by the venous drainage cannula before it goes through the patient’s heart into the systemic circulation This phenomenon is known as recirculation, and it can be a major limiting factor in providing adequate patient support with VV ECMO With double lumen cannulas placed via the right internal jugular vein to the right atrium, careful orientation of the inflow lumen toward the tricuspid valve may limit recirculation The larger separation of drainage and inflow lumens with the Avalon device seems to be associated with fewer recirculation difficulties With two-site venous cannulation, recirculation can be limited to some degree by ensuring that some distance separates the end tips of the drainage and infusion cannulas in the body Recirculation also can be reduced by draining from the femoral vein cannula and reinfusing into the right internal jugular vein cannula The extent of recirculation can be estimated by following the venous saturation in the extracorporeal life support circuit; high levels of recirculation will elevate the displayed venous saturation on the drainage line because some of the highly saturated return from the extracorporeal life support circuit is immediately drawn out by the drainage cannula Whether VV cannulation will adequately capture the patient’s cardiac output for ECMO support depends on how large the cannulas are, where they lie in the vessel, and how much overall ECMO support the patient requires Which of the following factors is associated with an increased chance of survival in children placed on ECMO during arrest? A Metabolic abnormality B Renal insufficiency C Underlying cardiac illness D Use of sodium bicarbonate or tromethamine during arrest Preferred response: C e88 S E C T I O N XV Pediatric Critical Care: Board Review Questions Rationale A review from the National Registry of Cardiopulmonary Resuscitation found that 199 pediatric patients placed on ECMO during arrest had an overall survival rate of 44% In 59 survivors in whom a neurologic outcome was recorded, 95% had favorable outcomes based on Pediatric Cerebral Performance scores By multivariate analysis, renal insufficiency, metabolic or electrolyte abnormality at the time of arrest, and use of sodium bicarbonate or tromethamine were associated with decreased survival Underlying cardiac illness was associated with an increased survival to discharge Chapter 57: Pediatric Lung Transplantation Which of the regimens below best exemplifies the maintenance triple drug regimen for immune suppression in lung transplant: A Anti-thymocyte globulin, a calcineurin inhibitor, and corticosteroid B Anti-CD52 biological, anti-thymocyte globulin, and prednisone C Anti-CD25 biological, a B-cell proteasome inhibitor, and corticosteroid D A calcineurin inhibitor, a T-cell anti-proliferative, and corticosteroid Preferred response: D Rationale The registry of the International Society of Heart and Lung Transplant publishes annual synopsis of the treatment practices of thoracic transplant centers This triple-armed regimen suppresses several arms of the immune system with guidelines for therapeutic level monitoring The regimen provides the most complete immune suppression with accepted known toxicities and infection risk Which of the following statements is true regarding outcomes in pediatric transplant: A Children who undergo lung transplant never regain a normal functional status B Survival of children after a lung transplant is worse than that of adults C Survival of children who have been treated with ECMO prior to transplant is extremely poor D Survival of children after a lung transplant is as good as that of adults Preferred response: D Rationale The findings of the annual registry of the International Society of Heart and Lung Transplant (ISHLT) support this statement 3 Your patient, who is years post lung transplant and has maintained stable pulmonary function tests (PFTs), is seen in clinic for acute complaint of coughing and wheezing for days You obtain a chest radiograph, PFT, and a bronchoalveolar lavage (BAL) with transbronchial biopsy The PFT shows a decrease in forced expiratory volume in one second (FEV1) from baseline best by 50%, the radiograph shows mild hyperinflation, the BAL fluid is positive for respiratory syncytial virus (RSV) You decide to treat this with: A Increase tacrolimus levels to twice baseline, order an oral steroid pulse and antibiotics B Increase oral corticosteroid dose, no change in immune suppression, and oral antibiotics C Mechanical ventilation D Photopheresis, IV corticosteroid pulse, and augmented immune suppression regimen E Plasmapheresis, intravenous corticosteroid pulse, and augmented immune suppression Preferred response: B Rationale This patient is demonstrating acute changes in graft function due to RSV The appropriate initial response is to quell the inflammatory response with a small dose of corticosteroid Reassessment of graft function is merited before other steps are taken The type of chronic lung allograft disease (CLAD) that is representative of the biopsy and PFT findings seen in Fig 136.20 below in a patient years after transplant is: A Acute cellular rejection B Antibody mediated rejection C Bronchiolitis obliterans D Normal histological findings E restrictive allograft syndrome Preferred response: C –2 –4 –6 –8 Pred Pre Post • Fig 136.20 Rationale The emergence of airway luminal obliteration is seen on the histology and would lead to an obstructive pattern on pulmonary function testing; this would be described as bronchiolitis obliterans CHAPTER 136 Board Review Questions Chapter 58: Structure, Function, and Development of the Nervous System Global cerebral blood flow is highest in which of the following age groups? A Term newborns at 38–42 weeks estimated gestational age B Infants 1–12 months of age C Children 2–8 years of age D Adolescents 12 and adults Preferred response: C Rationale Peak cerebral blood flow in humans occurs at approximately years of age and coincides with peak cerebral metabolism during neurodevelopment Cerebral blood flow declines toward adult values during adolescence Which of the following statements regarding the action of barbiturates is correct? A Barbiturates increase the duration that gamma-aminobutyric acid (GABA) receptors remain open B Barbiturates increase the frequency of gamma-aminobutyric acid (GABA) receptor opening C Barbiturates increase the duration that N-methyl-d-aspartate (NMDA)-type glutamate receptors remain open D Barbiturates increase the frequency of N-methyl-d-aspartate (NMDA)-type glutamate receptor opening Preferred response: A Rationale Barbiturates act at GABA receptors to increase the duration that GABA channels remain open Benzodiazepines increase the frequency of GABA channel opening Barbiturates are not NMDA or serotonin receptor antagonists A previously healthy 3-year-old boy presents with a fever of 41°C, nuchal rigidity, and photophobia A lumbar puncture reveals cerebrospinal fluid (CSF) with a markedly elevated WBC count The child is treated with ceftriaxone, vancomycin, and acyclovir and admitted to the PICU for observation CSF culture grows Streptococcus pneumoniae that is sensitive to ceftriaxone The fever resolves over the next 72 hours with improvement in his clinical exam On the fourth day of admission, he complains of headache in the morning and vomits In the afternoon, he acutely becomes unresponsive with a dilated and fixed right pupil An emergent head CT shows a nonobstructive hydrocephalus with enlargement of the lateral ventricles and effacement of the cerebral sulci Of the following, which option best explains the pathophysiology of his hydrocephalus? A Decreased CSF absorption due to blockage of the aqueduct of Sylvius with bacterial and cellular debris B Decreased CSF absorption due to blockage of arachnoid granulations with bacterial and cellular debris C Increase in CSF production due to inflammation D Low-pressure hydrocephalus due to loss of cerebral cortical volume Preferred response: B Rationale Bacterial debris and cellular breakdown products in CSF can lead to blockage and thickening of arachnoid granulations and in some cases hydrocephalus and intracranial hypertension e89 The type of chronic lung allograft disease (CLAD) that is representative of the biopsy and PFT findings seen below in a patient years after transplant is: A Acute cellular rejection B Antibody mediated rejection C Bronchiolitis obliterans D Normal histological findings E Restrictive allograft syndrome Preferred response: C Rationale The emergence of airway luminal obliteration is seen on the histology and would lead to an obstructive pattern on pulmonary function testing, and would be described as bronchiolitis obliterans During the CT scan, the boy develops hypertension (blood pressure, 200/120 mm Hg) and bradycardia to 30 beats/min, loses pupillary reflex in his left eye, and develops gasping intermittent respirations His symptoms are most consistent with compression of which brain structure? A Cerebellum B Cortex C Optic nerves D Pons Preferred response: D Rationale Compression on the pons, in this case as a consequence of intracranial hypertension leading to herniation, produces the classic Cushing triad of hypertension, bradycardia, and irregular breathing The patient is treated with hyperosmolar agents to reverse his herniation and is endotracheally intubated A member of the neurosurgery staff places an external ventricular drain at the patient’s bedside, which resolves his intracranial hypertension (ICP ,20 mm Hg) An electroencephalogram reveals status epilepticus Midazolam boluses and a rapidly escalating midazolam infusion fail to control his seizures The patient is then converted from midazolam to a pentobarbital infusion, which controls his seizures He is weaned off pentobarbital in days, extubated on hospital day 11, and leaves the PICU on day 12 A neurodevelopmental screen months later demonstrates mild residual hearing loss and mild attention deficits What is the most likely reason pentobarbital but not midazolam controlled his seizures? A Pentobarbital acts on glycine receptors, whereas midazolam acts on GABA receptors B Pentobarbital penetrates the blood-brain barrier better than does midazolam C Pentobarbital but not midazolam depresses respiratory activity, allowing for better control of pco2 D Pentobarbital at high doses becomes a direct GABA agonist, leading to suppression of neuronal activity independent of endogenous GABA release Preferred response: D Rationale Pentobarbital acts on GABA receptors by increasing the duration of chloride channel opening, but at high doses it becomes a direct GABA agonist Midazolam acts on GABA receptors by increasing the frequency of chloride channel opening and does not act as a direct GABA agonist even at high doses e90 S E C T I O N XV Pediatric Critical Care: Board Review Questions A global cerebral blood flow (CBF) value of 50 mL/100 g brain/min is normal in which of the following cases? A A healthy term newborn human B A healthy 4-year-old child C A healthy 12-year-old child D A healthy 20-year-old adult human Preferred response: D Rationale Normal global CBF for humans from around age 20 to 60 years is approximately 50 mL/100 g brain/min Normal global CBF for newborns is approximately 40 mL/100 g brain/min CBF begins to increase from newborn values a few days after birth, peaking around years of age and then declining toward adult values at the end of adolescence Chapter 59: Critical Care Considerations for Common Neurosurgical Conditions Arachnoid cysts most commonly present with which of the following complaints: A Blindness B Focal neurologic deficit C Incidental finding D Seizure Preferred response: C Rationale Arachnoid cysts have been associated with seizures in rare instances, and a focal neurologic deficit or visual impairment could be caused by mass effect But these are most commonly silent lesions found when a patient is scanned for an unrelated reason Congenital encephaloceles are most commonly found at which anatomical site? A Occipital B Optic canal C Parietal D Squamosal suture Preferred response: A Rationale Encephaloceles can occur anywhere but are most frequently found in the midline occipital region Which of the following is a risk associated with fetal myelomeningocele repair? A Fetal death B Hydrocephalus C Preeclampsia D Seizures Preferred response: A Rationale Fetal surgery presents risks to both the mother and fetus Preeclampsia and seizures have not been shown to be associated with fetal interventions Hydrocephalus is independently associated with myelomeningocele, not specifically with any form of repair 4 A 12-year-old child with a history of myelomeningocele and hydrocephalus treated with a ventriculoperitoneal shunt is admitted with urosepsis In addition to dysuria, she has been complaining of headache for several days Overnight, she becomes increasingly somnolent and difficult to rouse Which of the following clinical findings are consistent with elevated intracranial pressure from shunt failure? A Absence of papilledema B Enlarged ventricles on computed tomography or magnetic resonance imaging C Inability to look downward D Tachycardia and hypotension Preferred response: B Rationale Shunt failure and untreated hydrocephalus lead to an accumulation of cerebrospinal fluid in the ventricles, causing them to enlarge in most patients It is useful to compare new imaging with older studies, as some patients have large ventricles at baseline; relative enlargement compared with old studies is highly concerning for shunt failure Elevated intracranial pressure from any cause can also lead to papilledema, which is seen on funduscopic examination of the retina Papilledema may take several days to develop after the intracranial pressure becomes elevated, so its absence should not be interpreted as reassuring in the acute setting As intracranial pressure continues to rise, pressure on the midbrain can cause an upgaze palsy, also known as Parinaud syndrome Late in the course, dangerous elevations in intracranial pressure cause brainstem compression, leading to bradycardia and hypertension Leukocytosis per se is not specific for shunt failure and elevated intracranial pressure, although it can be seen in the setting of shunt infections A 5-year-old boy is involved in a motor vehicle accident and suffers multiple traumatic injuries to the extremities and abdomen As part of his trauma workup, a computed tomography scan of the head is performed This study shows no intracranial hemorrhage but does demonstrate a large cystic structure anterior to the temporal lobe on the right The brain appears to be displaced slightly by the lesion, and the overlying skull is thinned and protuberant The family members deny that the boy had experienced headaches or any neurologic problems prior to the accident The radiologist suggests that this might be an arachnoid cyst What is the appropriate next step to manage this finding? A Administration of mannitol B Immediate operative decompression C MRI once the patient has been stabilized D Percutaneous needle biopsy to confirm the diagnosis Preferred response: C Rationale Suspected arachnoid cysts should be imaged with contrast-enhanced MRI to rule out other diagnoses, such as a neoplasm There is no need to perform this study emergently; it should only be done once the patient is stabilized and his injuries are treated Indeed, most arachnoid cysts are asymptomatic and are discovered incidentally The majority never require surgery Operative intervention can be required when there is hemorrhage into the cyst or when the cyst progressively enlarges, but these circumstances are rare Although these lesions tend to displace the brain, they so chronically and not cause acute intracranial hypertension; there is no indication for mannitol Tissue biopsy is ... recirculation This means that oxygenated blood returning from the ECMO pump is drawn immediately back into the venous drainage cannula This will increase the saturation of oxygenated blood within the... patient weighing up to 12 kg This cannula is placed into the right internal jugular vein and requires only one surgical site The drainage and infusion lumens in this cannula are separated by... on the pons, in this case as a consequence of intracranial hypertension leading to herniation, produces the classic Cushing triad of hypertension, bradycardia, and irregular breathing The patient