Jeff A. Clark

Metabolic acidosis as an underlying mechanism of respiratory distress in children with severe acute asthma

Objective: 1) To alert the clinician that increasing rate and depth of breathing during treatment of acute asthma may be a manifestation of metabolic acidosis with hyperventilation rather than worsening airway obstruction; and 2) to describe the frequency of metabolic acidosis with hyperventilation in children with severe acute asthma admitted to our pediatric intensive care unit. Design: Retrospective medical record review. Setting: University-affiliated childrens hospital. Patients: All patients admitted to the pediatric intensive care unit with a diagnosis of asthma between January 1, 2005, and December 31, 2005. Interventions: None. Measurements and Main Results: Fifty-three patients with asthma (median age 7.8 yrs, range 0.7–17.9 yrs; 35 [66%] male; 46 [87%] black and 7 [13%] white) were admitted to the pediatric intensive care unit during the study period. Fifteen (28%) patients developed metabolic acidosis with hyperventilation (pH <7.35, Pco2 <35 torr [4.6 kPa], and base excess ≤−7 mmol/L) during their hospital course. Of these, lactic acid was assessed in four patients and was elevated in each; all had hyperglycemia (blood glucose >120 mg/dL [6.7 mmol/L]). Patients who developed metabolic acidosis with hyperventilation received asthma therapy similar to that received by patients who did not develop the disorder. Metabolic acidosis resolved contemporaneously with tapering of &bgr;2-adrenergic agonists and administration of supportive care. All patients survived. Conclusions: Metabolic acidosis with hyperventilation manifesting as respiratory distress can occur in children with severe acute asthma. A pathophysiologic rationale exists for the contribution of &bgr;2-adrenergic agents to the development of this acid-base disorder. Failure to recognize metabolic acidosis as the underlying mechanism of respiratory distress may lead to inappropriate intensification of bronchodilator therapy. Supportive care and tapering of &bgr;2-adrenergic agents are recommended to resolve this condition.

Arginine vasopressin to manage hypoxemic infants after stage I palliation of single ventricle lesions

Objective: Management of patients with single ventricle physiology following stage I palliation procedures is often challenging, with optimization of the ratio of pulmonary-to-systemic blood flow as an important goal. Persistent hypoxemia may be a manifestation of elevated pulmonary vascular resistance and therefore decreased blood flow to the lungs. In such situations, the use of arginine vasopressin to increase systemic vascular resistance may be an effective strategy to improve pulmonary blood flow and maintain adequate pulmonary-to-systemic blood flow ratio. We describe three infants in whom persistent hypoxemia improved after institution of arginine vasopressin. Design: Retrospective chart review. Setting: Twenty-four bed medical-surgical pediatric intensive care unit at a large tertiary care academic hospital. Patients: Three neonates with single ventricle physiology who received arginine vasopressin in the setting of hypoxemia following stage I palliation. Results: Arginine vasopressin was initiated in all three patients for hypoxemia with a goal to increase systemic vascular resistance and generate a higher driving pressure for pulmonary blood flow. Twelve hours after arginine vasopressin initiation, systemic arterial saturation as determined by pulse oximetry and blood pressure increased, whereas heart rate, inotrope score, and Fio2 decreased in all three patients. Urine output was maintained and arterial lactate decreased during this time. Pulmonary-to-systemic flow ratio increased in one patient in whom it could be determined. Conclusion: In patients with single ventricle physiology and persistent hypoxemia following stage I palliation, administration of arginine vasopressin could improve oxygenation possibly by increasing systemic vascular resistance and therefore the pulmonary blood flow.

Relative deficiency of arginine vasopressin in children after cardiopulmonary bypass

Objective:To describe changes in plasma arginine vasopress in concentration in children following cardiopulmonary bypass and determine whether, in some patients, plasma arginine vasopressin remains relatively low despite hemodynamic instability. Design:Prospective observational study. Setting:Pediatric intensive care unit at a tertiary care university hospital. Patients:One hundred twenty patients ≤18 yrs of age undergoing open heart surgery requiring cardiopulmonary bypass at Childrens Hospital of Michigan between January 2008 and January 2009. Interventions:Blood samples were collected before cardiopulmonary bypass and 4, 24, and 48 hrs after cardiopulmonary bypass for measurement of plasma arginine vasopressin concentration. Measurements and Main Results:Mean plasma arginine vasopressin (pg/mL) for all patients was 21 ± 63 before cardiopulmonary bypass and 80 ± 145, 43 ± 79, and 19 ± 25 at 4, 24, and 48 hrs, respectively, after cardiopulmonary bypass. Patients with plasma arginine vasopressin below the lower quartile (<9.2 pg/mL) at 4 hrs after cardiopulmonary bypass (n = 29), labeled group A, were examined separately and compared with the rest of the study population, labeled group B. Mean plasma arginine vasopressin was 4.9 ± 2.6 in group A at 4 hrs after cardiopulmonary bypass, statistically unchanged from its baseline mean plasma arginine vasopressin of 5.0 ± 10.4 (p = .977). Mean plasma arginine vasopressin in group B was 104 ± 160 at 4 hrs after cardiopulmonary bypass. Mean plasma arginine vasopressin of group A was also significantly lower as compared with group B before and 24 and 48 hrs after cardiopulmonary bypass. Hemodynamics, inotrope score, and serum sodium did not differ between groups at any time point. Plasma arginine vasopressin was measured immediately before exogenous arginine vasopressin administration in 10 patients; only those (n = 3) with hemodynamic instability and relatively low plasma arginine vasopressin concentration (<9.2 pg/mL) had notable hemodynamic improvement. Conclusions:In some children undergoing open heart surgery, plasma arginine vasopressin concentration is relatively low at baseline and remains low after cardiopulmonary bypass regardless of hemodynamic stability and serum osmolality. These children are likely the optimal candidates for exogenous arginine vasopressin should hemodynamic compromise occur.

Acute thiamine deficiency in diabetic ketoacidosis: Diagnosis and management

Objective: Persistent encephalopathy in a patient with diabetic ketoacidosis is often feared as a sign of cerebral edema. Although thiamine deficiency is a rare diagnosis in children, marginal nutritional status and osmotic diuresis may be risk factors. The objective was to describe a heretofore unreported cause of encephalopathy in a child with diabetic ketoacidosis and review the mechanisms and pathophysiology of thiamine deficiency in this clinical scenario. Design: Case report and review of the literature. Setting: Pediatric intensive care unit of a tertiary care pediatric hospital. Patient: A 13-yr-old girl. Interventions: Treatment of dehydration and hyperglycemia, osmotherapy, and intravenous thiamine administration. Measurements and Main Results: The patient presented with new-onset diabetes mellitus, severe diabetic ketoacidosis, and significant encephalopathy. Despite biochemical improvement with treatment of dehydration and hyperglycemia, her encephalopathy persisted. Computed tomography did not show cerebral edema and she showed no response to osmotherapy. Quantitative and functional assays revealed severe thiamine deficiency. The patient showed an immediate and dramatic response to intravenous thiamine administration. Conclusions: The clinical improvement as well as lab investigations suggests that thiamine deficiency was the cause of this child’s encephalopathy. Because potential mechanisms exist for thiamine deficiency in diabetes mellitus and institution of insulin and glucose therapy may stress thiamine body stores, thiamine deficiency should be considered in children with diabetic ketoacidosis whose encephalopathy does not improve with improvement of biochemical status.

Views of pediatric intensive care physicians on the ethics of organ donation after cardiac death

Objective:Donation after cardiac death has been endorsed by professional organizations, including the American Academy of Pediatrics as a means of increasing the supply of transplantable organs. However, ethical concerns have been raised about donation after cardiac death, especially in children. This study explores the views of pediatric intensive care physicians on the ethics of pediatric donation after cardiac death. Design:Internet survey. Subjects:Physician members of the American Academy of Pediatrics Section of Critical Care. Interventions:Physicians were emailed an anonymous survey consisting of four demographic items and 16 items designed to assess their views on the ethics of pediatric donation after cardiac death. Responses to ethics items were rated on a 5-point scale ranging from strongly disagree to strongly agree. Physicians were also given the opportunity to provide free-text comments regarding their views. Measurements and Main Results:Of the 598 eligible physicians, 264 (44.1%) responded to the survey. Of these, 193 (73.4%) were practicing in a transplant center and 160 (60.6%) participated in at least one donation after cardiac death procedure at the time of survey completion. Two hundred twenty (83.4%) agreed or strongly agreed that regarding donation after cardiac death, parents should be able to make decisions based on the best interests of their child. Two hundred twenty-two (84.1%) agreed or strongly agreed that it is not acceptable to harvest organs from a child before the declaration of death, consistent with the Dead Donor Rule. However, only 155 (59.1%) agreed or strongly agreed that the time of death in donation after cardiac death can be conclusively determined. Twenty-nine (11.0%) agreed or strongly agreed that the pediatric donation after cardiac death donor may feel pain or suffering during the harvest procedure. Conclusions:Most pediatric intensive care physicians agree that the Dead Donor Rule should be applied for donation after cardiac death and that donation after cardiac death can be consistent with the best interest standard. However, concerns about the ability to determine time of death for the purpose of organ donation and the possibility of increasing donor pain and suffering exist.

Low thiamine levels in children with type 1 diabetes and diabetic ketoacidosis: a pilot study.

Objective: Thiamine deficiency has been documented in adults with diabetes and in a single report of reversible encephalopathy in a child with diabetic ketoacidosis. In children who present with severe diabetic ketoacidosis, one of the most serious complications is cerebral edema of which the primary symptom may be encephalopathy. Thiamine deficiency in other disease states has been clearly linked with acute encephalopathy, but there are no data on thiamine status in children with diabetic ketoacidosis. This study describes the prevalence of thiamine deficiency in children with type 1 diabetes mellitus who present with diabetic ketoacidosis and are admitted to the ICU. Design: A prospective observational pilot study. Setting: PICU in a tertiary care children’s hospital. Patients: Children 2–18 years admitted to the ICU for treatment of diabetic ketoacidosis. Interventions: Treatment of diabetic ketoacidosis. Measurements and Main Results: Twenty-two patients were enrolled. The mean age was 13.7 ± 3.6 years. Five of 21 patients (23.8%) had thiamine deficiency prior to insulin administration. After 8 hours of insulin therapy, seven of 20 patients (35%) had thiamine deficiency, and four of these seven patients also had thiamine deficiency at presentation. Sixty-eight percent of patients had a decrease in thiamine levels after 8 hours of insulin therapy, with a mean fall of 20 ± 31.4 nmol/L. Conclusions: Thiamine deficiency is common in children with diabetic ketoacidosis, and this deficiency may be worsened by treatment. When metabolic acidosis persists despite appropriate treatment of diabetic ketoacidosis, other factors such as thiamine deficiency should be considered.