Avinash Shukla

Comparison of commonly used clinical indicators of hypovolaemia with gastrointestinal tonometry

Objective: The gastrointestinal tonometer, which allows measurement of gastrointestinal mucosal CO2 and subsequent derivation of gut intramucosal pH (pHi), has been demonstrated to be a sensitive predictor of outcome following major surgery. Current theory suggests that the origin of the low pH may be hypovolaemia. This study was designed to compare the temporal sequence of changes in tonometric readings with invasive blood pressure, stroke volume, heart rate, lactate and arterial blood gas measurements during progressive haemorrhage. Design: Observational healthy volunteer study. Setting: Intensive care unit at University College London Hospitals. Subjects: Six healthy, medically qualified volunteers. Interventions: After obtaining baseline measurements, the subjects were progressively bled 25 % (range = 21–31 %) of their blood volume over a period of 1 h in two approximately equal aliquots. Equilibration was allowed for 30 min following the bleed, after which further measurements were made and the blood was then retransfused over 30 min. Measurements and main results: There was no consistent change in any of the haemodynamic variables other than gastric intramucosal CO2 : arterial CO2 gap (PiCO2− PaCO2) after removal of the first aliquot of blood, although five of the six subjects also demonstrated a fall in pHi. After removal of the second aliquot of blood, PiCO2− PaCO2 gap and pHi continued to indicate a worsening gastric intramucosal acidosis; stroke volume, as measured by suprasternal Doppler, demonstrated a marked fall, while all other variables measured had not altered consistently or to such a degree as to elicit a clinical response or cause suspicion of a hypovolaemic state. On retransfusion, all variables returned towards baseline. Conclusions: This study demonstrates the value of tonometry as an early monitor of hypovolaemia and highlights the shortcomings of other more commonly measured clinical variables.

Real-Time Continuous Glucose Monitoring in Pediatric Patients During and After Cardiac Surgery

OBJECTIVES. Given the demonstrated benefit of euglycemia in critically ill patients as well as the risk for hypoglycemia during insulin infusion in children, we sought to validate a subcutaneous sensor for real-time continuous glucose monitoring in pediatric patients during and after cardiac surgery. METHODS. Children up to 36 months of age who were undergoing cardiac bypass surgery were recruited. After anesthetic induction, a continuous glucose-monitoring system sensor (CGMS, Medtronic Minimed, Northridge, CA) was inserted subcutaneously. Sensors remained in place for up to 72 hours. Arterial blood glucose was measured intermittently in the central laboratory (Bayer Rapidlab 860, Tarrytown, NY). Sensor data, after prospective calibration with 6-hourly laboratory values using the proprietary Medtronic Minimed Guardian RT algorithm, were compared with all laboratory glucose values. Statistical analysis was performed to test whether sensor performance was affected by body temperature, inotrope dose, or body-wall edema. RESULTS. Twenty patients were enrolled in the study for a total of 40 study days and 246 paired sensor and laboratory glucose values. Consensus error grid analysis demonstrated that 72.0% of sensor value comparisons were within zone A (no effect on clinical action), and 27.6% of comparisons were within zone B (altered clinical action of little or no effect on outcome), with a mean absolute relative deviation of 17.6% for all comparisons. One comparison (0.4%) was in zone C (altered clinical action likely to affect outcome). No significant correlations were found between sensor performance and body temperature, inotrope dose, or body-wall edema. All patients tolerated the sensors well without bleeding or tissue reaction. CONCLUSIONS. Guardian RT real-time subcutaneous blood glucose measurement is safe and potentially useful for continuous glucose monitoring in critically ill children. Subcutaneous sensors performed well in the setting of hypothermia, inotrope use, and edema. These sensors facilitate identifying and following the effects of interventions to control blood glucose.

Hemodynamic Responses to Etomidate on Induction of Anesthesia in Pediatric Patients

Etomidate is often used for inducing anesthesia in patients who have limited hemodynamic reserve. Using invasive hemodynamic monitoring, we studied the acute effects of a bolus of etomidate during induction of anesthesia in children. Twelve children undergoing cardiac catheterization were studied (mean age, 9.2 ± 4.8 yr; mean weight, 33.4 ± 15.4 kg); catheterization procedures included device closure of secundum atrial septal defects (n = 7) and radiofrequency catheter ablation procedures for supraventricular tachycardia (n = 5). Using IV sedation, a balloon-tipped pulmonary artery catheter was placed to measure intracardiac and pulmonary artery pressures and oxygen saturations. Baseline measurements were recorded and then re-peated after a bolus of IV etomidate (0.3 mg/kg). For the entire group, no significant changes in right atrial, aortic, or pulmonary artery pressure, oxygen saturations, calculated Qp:Qs ratio or systemic or pulmonary vascular resistance were detected after the bolus dose of etomidate. The lack of clinically significant hemodynamic changes after etomidate administration supports the clinical impression that etomidate is safe in children. Further research is needed to determine the hemodynamic profile of etomidate in neonates and in pediatric patients with severe ventricular dysfunction and pulmonary hypertension.

The Frequency of Anesthesia-Related Cardiac Arrests in Patients with Congenital Heart Disease Undergoing Cardiac Surgery

BACKGROUND:The frequency of anesthesia-related cardiac arrests during pediatric anesthesia has been reported between 1.4 and 4.6 per 10,000 anesthetics. ASA physical status >III and younger age are risk factors. Patients with congenital cardiac disease may also be at increased risk. Therefore, in this study, we evaluated the frequency of cardiac arrest in patients with congenital heart disease undergoing cardiac surgery at a large pediatric tertiary referral center. METHODS:Using an established data registry, all cardiac arrests from January 2000 through December 2005 occurring in the cardiac operating rooms were reviewed. A cardiac arrest was defined as any event requiring external or internal chest compressions, with or without direct cardioversion. Events determined to be anesthesia-related were classified as likely related or possibly related. RESULTS:There were 41 cardiac arrests in 40 patients (median age, 2.9 mo; range, 2 days to 23 yr) during 5213 anesthetics over the time period, for an overall frequency of 0.79%; 78% were open procedures requiring cardiopulmonary bypass and 22% closed procedures not requiring cardiopulmonary bypass. Eleven cardiac arrests (26.8%) were classified as either likely (n = 6) or possibly related (n = 5) to anesthesia, (21.1 per 10,000 anesthetics) but with no mortality; 30 were categorized as procedure-related. The incidence of anesthesia-related and procedure-related cardiac arrests was highest in neonates (P < 0.001). There was no association with year of event or experience of the anesthesiologist. CONCLUSION:The frequency of anesthesia-related cardiac arrest in patients undergoing cardiac surgery is increased, but is not associated with an increase in mortality. Neonates and infants are at higher risk. Careful preparation and anticipation is important to ensure timely and effective resuscitation.

The frequency of cardiac arrests in patients with congenital heart disease undergoing cardiac catheterization.

BACKGROUND:Cardiac catheterization for patients with congenital heart disease has shifted from diagnostic to predominantly interventional procedures because of advances in catheter-based technologies. Children undergoing therapeutic catheterization may be at higher risk of adverse events, and the purpose of our study was to determine the incidence of cardiac arrest (CA) in patients with congenital heart disease undergoing cardiac catheterization at a large pediatric tertiary referral center. METHODS:All CAs from January 2004 through December 2009 occurring in the cardiac catheterization laboratory were reviewed. A CA was defined as an event in which cessation of circulation required chest compressions. Procedure, patient, practitioner, and system-related factors were examined. RESULTS:Over the study period, during 7289 catheterization procedures, 70 procedures were associated with a CA (0.96 [99% confidence interval, 0.7–1.3] per 100 procedures); 48 events (69%) were successfully resuscitated to a perfusing rhythm, 18 events (26%) resulted in need for extracorporeal membrane oxygenation, and 4 events (6%) resulted in unsuccessful resuscitation. Sudden onset of cardiac arrhythmia led to CA during 38 events (54%). The duration of resuscitation after CA was ⩽11 minutes in 71%. Occurrence of CA was associated with interventional procedures (P < 0.001) and younger age (P < 0.001). A change in systems for scheduling and communication of cases was associated with a significant reduction in the incidence of CA (1.5% vs 0.7%; P = 0.002). CONCLUSIONS:The incidence of CA in children undergoing cardiac catheterization is high compared with pediatric noncardiac surgery. Procedural and system factors were associated with occurrence of CA in this cohort. These issues highlight the need for close communication, anticipation, and preparation.

Anesthesia considerations for children with pulmonary hypertension

Children with pulmonary arterial hypertension undergoing anesthesia pose a challenge. The prevalence of morbidity and mortality in this subgroup is substantially greater than that in the general population. In this article, we attempt to describe the adverse events that occur and also identify some of the factors that may precipitate them. We also suggest mechanisms to attenuate or prevent these crises.

Design and rationale of safe pediatric euglycemia After cardiac surgery: A randomized controlled trial of tight glycemic control After pediatric cardiac surgery

Objectives: To describe the design of a clinical trial testing the hypothesis that children randomized to tight glycemic control with intensive insulin therapy after cardiac surgery will have improved clinical outcomes compared to children randomized to conventional blood glucose management. Design: Two-center, randomized controlled trial. Setting: Cardiac ICUs at two large academic pediatric centers. Patients: Children from birth to those aged 36 months recovering in the cardiac ICU after surgery with cardiopulmonary bypass. Interventions: Subjects in the tight glycemic control (intervention) group receive an intravenous insulin infusion titrated to achieve normoglycemia (target blood glucose range of 80–110 mg/dL; 4.4–6.1 mmol/L). The intervention begins at admission to the cardiac ICU from the operating room and terminates when the patient is ready for discharge from the ICU. Continuous glucose monitoring is performed during insulin infusion to minimize the risks of hypoglycemia. The standard care group has no target blood glucose range. Measurements and Main Results: The primary outcome is the development of any nosocomial infection (bloodstream, urinary tract, and surgical site infection or nosocomial pneumonia). Secondary outcomes include mortality, measures of cardiorespiratory function and recovery, laboratory indices of nutritional balance, immunologic, endocrinologic, and neurologic function, cardiac ICU and hospital length of stay, and neurodevelopmental outcome at 1 and 3 yrs of age. A total of 980 subjects will be enrolled (490 in each treatment arm) for sufficient power to show a 50% reduction in the prevalence of the primary outcome. Conclusions: Pediatric cardiac surgery patients may recognize great benefit from tight glycemic control in the postoperative period, particularly with regard to reduction of nosocomial infections. The Safe Pediatric Euglycemia after Cardiac Surgery trial is designed to provide an unbiased answer to the question of whether this therapy is indeed beneficial and to define the associated risks of therapy.