Gabriel J. Hauser

Initial postoperative serum lactate levels predict survival in children after open heart surgery

ObjectiveTo evaluate the relationship between postoperative serum lactate levels and outcome in children undergoing open heart surgery.DesignProspective, noninterventional study.SettingPediatric intensive care unit (PICU) of a university hospital.Patients41 nonconsecutive children who had had cardiopulmonary bypass for repair of congenital heart disease.InterventionsNone.Measurements and resultsSerum lactate levels were measured on admission to the PICU immediately after open heart surgery. Lactate levels were correlated with bypass and cross clamp times, estimated intraoperative blood loss, lowest temperature on bypass, admission Pediatric Risk of Mortality score, anion gap, and measures of postoperative morbidity. Mean lactate levels on admission to the PICU were 6.86±0.79 mmol/l for nonsurvivors (n=7) and 2.38±0.13 mmol/l for survivors (n=34) (p<0.0001), and 4.87±0.7 mmol/l and 2.35±0.19 mmol/l, for patients with (n=11) and without (n=30) multiple organ system failure, respectively (p<0.0001). Admission lactate levels correlated with all measurements of postoperative morbidity. A serum lactate level of greater than 4.2 mmol/l had a positive predictive value of 100% and a negative predictive value of 97% for postoperative death.ConclusionsInitial postoperative serum lactate levels after pediatric open heart surgery may be predictive of outcome. Lactate levels are also higher in patients who go on to develop multiple organ system failure. Elevated postoperative lactate levels may reflect intraoperative tissue hypoperfusion, and measures aimed at increasing oxygen delivery, with normalization of lactate, may improve patient outcome.

Interleukin-6 levels in serum and lung lavage fluid of children undergoing open heart surgery correlate with postoperative morbidity

Objective: To evaluate the relationship of perioperative levels of interleukin 6 (IL-6) in serum and bronchoalveolar fluid with morbidity and mortality in children undergoing cardiopulmonary bypass (CPB). Design: Prospective, noninterventional study. Setting: Operating room and pediatric intensive care unit (PICU) of a university hospital. Interventions: None. Measurements and results: IL-6 levels were measured in serum and lung lavage fluid obtained before, during, and after CPB using the B9.9 bioassay. Alveolar epithelial lining fluid (AELF) volume was calculated using the urea correction method. Mean intraoperative AELF IL-6 levels increased fourfold compared to preoperative levels, and mean serum IL-6 levels increased fivefold after CPB. Mean intraoperative AELF IL-6 levels correlated with intraoperative blood transfusion (r2 = 0.18; p = 0.049) and duration of inotropic support (r2 = 0.29; p = 0.009), mechanical ventilation (r2 = 0.24; p = 0.019), and PICU stay (r2 = 0.29; p = 0.008). Mean serum IL-6 levels 2 h after CPB correlated with intraoperative blood transfusion (r2 = 0.3; p = 0.007), and with Pediatric Risk of Mortality score on postoperative day 3 (r2 = 0.24; p = 0.022), and were higher in patients with massive fluid retention (p = 0.014) and in nonsurvivors (p = 0.003). Conclusions: Serum and alveolar IL-6 levels increase after CPB, and correlate with postoperative morbidity. Serum IL-6 levels also correlate with mortality. They may be useful in assessing the severity of the systemic inflammatory response after CPB.

Endogenous neuropeptide Y mediates vasoconstriction during endotoxic and hemorrhagic shock.

Neuropeptide Y (1-36), NPY, is a sympathetic vasoconstrictor whose activities in blood vessels is determined by the presence of vasoconstrictive Y1 receptors and the enzyme dipeptidyl peptidase IV (DPPIV), which converts NPY to non-vasoconstrictive peptides. While the role of the NPY system has been established during cold water stress, its role in hypotensive conditions has not; yet, exogenous NPY improves hemodynamics and survival in rats with endotoxic shock. We used a new selective non-peptidergic Y1 receptor antagonist, BIBP-3226, to determine the role of the endogenous NPY/Y1 system in endotoxic shock (induced by i.v. injection of 10 mg/kg of Escherichia coli lipopolysaccharide 0127:B8, LPS) and hemorrhagic shock (bleeding of 15 ml/kg over 1.5 min). Conscious rats received a bolus of BIBP-3226 or the vehicle 5 min before endotoxin challenge or induction of hemorrhage, followed by continuous infusion. Mean arterial pressure (MAP) at 5 min after LPS administration dropped in the control group by 15%, compared to 36% in the BIBP-3226-treated group (p < 0.01). Similarly, the hemorrhage-induced drop in MAP in the control group was 32% at 5 min, compared to 53% in the BIBP-treated rats (p < 0.01). Plasma NPY levels were unchanged in the endotoxic shock group, but were significantly elevated in the hemorrhagic shock group. BIBP-3226 pretreatment abrogated the increased plasma NPY levels after hemorrhagic shock. Endogenous NPY contributes to blood pressure recovery during endotoxic and hemorrhagic shock.

Effect of neuropeptide Y on endotoxin-induced suppression of the response to various agonists in conscious rats☆

Hypotension during endotoxic shock is related to reduced vascular responsiveness to vasoconstrictors. Neuropeptide Y (NPY) is known to potentiate the pressor response to some agonists, and NPY infusion has been shown to improve hemodynamics and survival in endotoxemic rats. We therefore studied the effect of NPY infusion on the suppressed pressor effect of norepinephrine (NE), angiotensin II (AII), vasopressin (VP), and endothelin (ET) in conscious endotoxemic rats. Chronically cannulated conscious rats were infused with a non-hypotensive dose of endotoxin (LPS, 10 micrograms/10 microliters/min) throughout the experiment. Infusion of NPY, 40 pmol/10 microliters/min was started 15 minutes before the LPS infusion, and continued for 65 minutes. Five minutes after the termination of NPY infusion, increasing agonist doses were administered i.v. to construct dose-response curves. Each experiment included one control group where saline replaced LPS, and one control group where saline replaced NPY. LPS infusion caused suppression of the pressor responses to all four agonists, as expressed by ED50 and by decreased pressor response to the individual agonist doses. In addition, LPS infusion altered the bradycardic response to AII and ET. NPY infusion prior to the administration of NE, AII and VP resulted in partial reversal of the LPS-induced suppressed responsiveness to these agonists. NPY infusion had no effect on the response to ET in either control or endotoxemic rats. Partial reversal of the suppressed responsiveness to the three agonists by NPY infusion may contribute to the observed NPY-induced improvement of blood pressure and survival rate during endotoxic shock.

Pediatric intestinal and multivisceral transplantation : a new challenge for the pediatric intensivist

IntroductionWith increasing survival rates, intestinal transplantation (ITx) and multivisceral transplantation have reached the mainstream of medical care. Pediatric candidates for ITx often suffer from severe multisystem impairments that pose challenges to the medical team. These patients frequently require intensive care preoperatively and have unique intensive care needs postoperatively.MethodsWe reviewed the literature on intensive care of pediatric intestinal transplantation as well as our own experience. This review is not aimed only at pediatric intensivists from ITx centers; these patients frequently require ICU care at other institutions.ResultsPreoperative management focuses on optimization of organ function, minimizing ventilator-induced lung injury, preventing excessive edema yet maintaining adequate organ perfusion, preventing and controlling sepsis and bleeding from varices at enterocutaneous interfaces, and optimizing nutritional support. The goal is to extend life in stable condition to the point of transplantation. Postoperative care focuses on optimizing perfusion of the mesenteric circulation by maintaining intravascular volume, minimizing hypercoagulability, and providing adequate oxygen delivery. Careful monitoring of the stoma and its output and correction of electrolyte imbalances that may require renal replacement therapy is critical, as are monitoring for and aggressively treating infections, which often present with only subtle clinical clues. Signs of intestinal rejection may be non-specific, and early differentiation from other causes of intestinal dysfunction is important. Understanding of the expanding armamentarium of immunosuppressive agents and their side-effects is required.Conclusions As outcomes of ITx improve, transplant teams accept patients with higher pre-operative morbidity and at higher risk for complications. Many ITx patients would benefit from earlier referral for transplant evaluation before severe liver disease, recurrent central venous catheter-related sepsis and venous thromboses develop.

Misplacement of a femoral venous catheter into the ascending lumbar vein: repositioning using ultrasonographic guidance

Abstract A 5-week-old infant with congenital chylothorax required long-term intravenous access for parenteral nutrition. Cannulation of the inferior vena cava via the left femoral vein was attempted, but the catheter was misplaced into the left ascending lumbar vein. Catheter removal is advised when such malposition is identified. We were able successfully to redirect the catheter into the inferior vena cava using ultrasonographic guidance. This procedure has not been described previously in children. We propose that repositioning of incorrectly placed vascular catheters can be achieved using ultrasound guidance at the bedside.

Circulating neuropeptide Y in humans: relation to changes in catecholamine levels and changes in hemodynamics

Neuropeptide-Y (NPY) is a sympathetic cotransmitter, which causes vasoconstriction, decreases coronary blood flow and decreases cardiac output. Circulating immunoreactive NPY (ir-NPY) levels increase with exercise, in patients admitted to the coronary care unit, and during thoracic surgery, and may play a role in postoperative hemodynamics. We studied changes in ir-NPY, epinephrine (E) and norepinephrine (NE) arterial plasma levels, and their correlation to simultaneous hemodynamic measurements at 8 perioperative time points in 13 patients undergoing open heart surgery. Changes in circulating ir-NPY negatively correlated with changes in systemic vascular resistance index (SVRI), mean arterial pressure (MAP) and mean pulmonary arterial pressure (MPAP) (P<0.05), suggesting that the hemodynamic changes were the cause of the changes in ir-NPY levels, inducing overflow of NPY into the circulation via sympathetic activation. Changes in NE and E levels positively correlated with changes in heart rate (HR), SVRI and MPAP. Changes in E levels also positively correlated with changes in stroke volume index (SVI), central venous pressure (CVP) and cardiac index (CI). NE levels correlated well with E levels, but catecholamine levels did not correlate with ir-NPY levels. These results suggest, that the elevation in circulating NPY levels previously noted in patients with heart failure and acute myocardial infarction may reflect changes in NPY overflow and/or clearance secondary to increased sympathetic activity and to hemodynamic changes.

Discordance in interpretation of chest radiographs between pediatric intensivists and a radiologist: Impact on patient management

PURPOSEnWhen radiologists are not available, chest radiographs (CXRs) of pediatric intensive care unit (PICU) patients are commonly interpreted by pediatric intensivists. We prospectively investigated the frequency of errors in CXR interpretation by pediatric intensivists and their impact on patient management.nnnMATERIALS AND METHODSnChest radiographs of PICU patients were evaluated by 5 pediatric intensivists then by a pediatric radiologist (the gold standard). If the interpretation of the radiologist and intensivist differed, an independent intensivist determined whether a management change took place. A pediatric pulmonologist determined how many intensivist interpretations were different from the radiologists interpretations.nnnRESULTSnSeven hundred twenty-eight radiographic findings were identified by the radiologist in 460 CXRs. There were 33 interpretation errors by the intensivists (4.5% of the findings in 7.1% of the CXRs). Only 3/33 error corrections (0.45% of the findings in 0.7% of the CXRs) resulted in change in patient management.nnnCONCLUSIONSnErrors in interpretation of CXRs by pediatric intensivists were common but less than that in other series, probably because of education of the pediatric intensivists through daily rounds with the radiologist. Although interpretation errors that affected patient management were rare, their clinical importance supports the growing practice of 24/7 remote radiograph reading by radiologists.

Use of airway pressure release ventilation in a child with refractory hepatopulmonary syndrome after liver transplantation

HPS is a life‐threatening condition in patients with end‐stage liver disease, in which intrapulmonary vascular dilatations result in intrapulmonary shunts and hypoxemia. The only successful treatment is liver transplantation. Hypoxemia may be severe prior to transplantation; however, it can worsen or become refractory after liver transplantation and result in increased post‐operative mortality. Here, we present the case of a 10‐month‐old female infant with progressive end‐stage liver disease and severe HPS, who developed refractory hypoxemia after a successful liver transplantation. After 19 days of unsuccessful attempts to reverse the hypoxemia using conventional mechanical ventilation and HFOV, the patient responded dramatically to APRV, with rapid improvement in her PaO2 and sharp decline in her OI. She was able to begin weaning from APRV two days later and was extubated within seven days. APRV was successful in treating refractory hypoxemia in this patient with severe HPS after liver transplantation, possibly by modifying distribution of pulmonary blood flow. Although we cannot rule out coincidental natural resolution of the HPS, APRV could be a useful rescue therapy in patients with HPS and refractory hypoxemia.

Technology assessment for an integrated PC-based platform for three telemedicine applications

This paper investigates the design and technical efficacy of an integrated PC based platform for three different medical applications. The technical efficacy of such a telemedicine platform has not been evaluated in the literature and optimal technical requirements have not been developed. The first application, with the Department of Surgery, Division of Urology, tests the utility of a telemedicine platform including radiology images for a surgical stone disease consultation service from an off site location in West Virginia. The second application, with the Department of Internal Medicine, Division of Clinical Pharmacology, investigates the usefulness of telemedicine when used for a clinical pharmacology consultation service from an off-site location. The third application, with the Department of Pediatrics, will test telemedicine for trauma care triage service first within an off-site location in Virginia and then from there to Georgetown University Medical Center.