Chandra Ramamoorthy

Anesthesia-related cardiac arrest in children: initial findings of the Pediatric Perioperative Cardiac Arrest (POCA) Registry.

Background The Pediatric Perioperative Cardiac Arrest (POCA) Registry was formed in 1994 in an attempt to determine the clinical factors and outcomes associated with cardiac arrest in anesthetized children. Methods Institutions that provide anesthesia for children are voluntarily enrolled in the POCA Registry. A representative from each institution provides annual institutional demographic information and submits anonymously a standardized data form for each cardiac arrest (defined as the need for chest compressions or as death) in anesthetized children 18 yr of age or younger. Causes and factors associated with cardiac arrest are analyzed. Results In the first 4 yr of the POCA Registry, 63 institutions enrolled and submitted 289 cases of cardiac arrest. Of these, 150 arrests were judged to be related to anesthesia. Cardiac arrest related to anesthesia had an incidence of 1.4 ± 0.45 (mean ± SD) per 10,000 instances of anesthesia and a mortality rate of 26%. Medication-related (37%) and cardiovascular (32%) causes of cardiac arrest were most common, together accounting for 69% of all arrests. Cardiovascular depression from halothane, alone or in combination with other drugs, was responsible for two thirds of all medication-related arrests. Thirty-three percent of the patients were American Society of Anesthesiologists physical status 1–2; in this group, 64% of arrests were medication-related, compared with 23% in American Society of Anesthesiologists physical status 3–5 patients (P < 0.01). Infants younger than 1 yr of age accounted for 55% of all anesthesia-related arrests. Multivariate analysis demonstrated two predictors of mortality: American Society of Anesthesiologists physical status 3–5 (odds ratio, 12.99; 95% confidence interval, 2.9–57.7), and emergency status (odds ratio, 3.88; 95% confidence interval, 1.6–9.6). Conclusions Anesthesia-related cardiac arrest occurred most often in patients younger than 1 yr of age and in patients with severe underlying disease. Patients in the latter group, as well as patients having emergency surgery, were most likely to have a fatal outcome. The identification of medication-related problems as the most frequent cause of anesthesia-related cardiac arrest has important implications for preventive strategies.

Anesthesia-Related Cardiac Arrest in Children: Update from the Pediatric Perioperative Cardiac Arrest Registry

BACKGROUND:The initial findings from the Pediatric Perioperative Cardiac Arrest (POCA) Registry (1994–1997) revealed that medication-related causes, often cardiovascular depression from halothane, were the most common. Changes in pediatric anesthesia practice may have altered the causes of cardiac arrest in anesthetized children. METHODS:Nearly 80 North American institutions that provide anesthesia for children voluntarily enrolled in the Pediatric Perioperative Cardiac Arrest Registry. A standardized data form for each perioperative cardiac arrest in children ≤18 yr of age was submitted anonymously. We analyzed causes of anesthesia-related cardiac arrests and related factors in 1998–2004. RESULTS:From 1998 to 2004, 193 arrests (49%) were related to anesthesia. Medication-related arrests accounted for 18% of all arrests, compared with 37% from 1994 to 1997 (P < 0.05). Cardiovascular causes of cardiac arrest were the most common (41% of all arrests), with hypovolemia from blood loss and hyperkalemia from transfusion of stored blood the most common identifiable cardiovascular causes. Among respiratory causes of arrest (27%), airway obstruction from laryngospasm was the most common cause. Vascular injury incurred during placement of central venous catheters was the most common equipment-related cause of arrest. The cause of arrest varied by phase of anesthesia care (P < 0.01). Cardiovascular and respiratory causes occurred most commonly in the surgical and postsurgical phases, respectively. CONCLUSIONS:A reduction in the proportion of arrests related to cardiovascular depression due to halothane may be related to the declining use of halothane in pediatric anesthetic practice. The incidence of the most common remaining causes of arrest in each category may be reduced through preventive measures.

The effects of dexmedetomidine on cardiac electrophysiology in children.

BACKGROUND:Dexmedetomidine (DEX) is an &agr;2-adrenergic agonist that is approved by the Food and Drug Administration for short-term (<24 h) sedation in adults. It is not approved for use in children. Nevertheless, the use of DEX for sedation and anesthesia in infants and children appears to be increasing. There are some concerns regarding the hemodynamic effects of the drug, including bradycardia, hypertension, and hypotension. No data regarding the effects of DEX on the cardiac conduction system are available. We therefore aimed to characterize the effects of DEX on cardiac conduction in pediatric patients. METHODS:Twelve children between the ages of 5 and 17 yr undergoing electrophysiology study and ablation of supraventricular accessory pathways had hemodynamic and cardiac electrophysiologic variables measured before and during administration of DEX (1 &mgr;g/kg IV over 10 min followed by a 10-min continuous infusion of 0.7 &mgr;g · kg−1 · h−1). RESULTS:Heart rate decreased while arterial blood pressure increased significantly after DEX administration. Sinus node function was significantly affected, as evidenced by an increase in sinus cycle length and sinus node recovery time. Atrioventricular nodal function was also depressed, as evidenced by Wenckeback cycle length prolongation and prolongation of PR interval. CONCLUSION:DEX significantly depressed sinus and atrioventricular nodal function in pediatric patients. Heart rate decreased and arterial blood pressure increased during administration of DEX. The use of DEX may not be desirable during electrophysiology study and may be associated with adverse effects in patients at risk for bradycardia or atrioventricular nodal block.

Anesthesia-Related Cardiac Arrest in Children with Heart Disease: Data from the Pediatric Perioperative Cardiac Arrest (POCA) Registry

BACKGROUND: From 1994 to 2005, the Pediatric Perioperative Cardiac Arrest Registry collected data on 373 anesthesia-related cardiac arrests (CAs) in children, 34% of whom had congenital or acquired heart disease (HD). METHODS: Nearly 80 North American institutions that provide anesthesia for children voluntarily enrolled in the Pediatric Perioperative Cardiac Arrest Registry. A standardized data form for each perioperative CA in children 18 years old or younger was submitted anonymously. We analyzed causes of and outcomes from anesthesia-related CA in children with and without HD. RESULTS: Compared with the 245 children without HD, the 127 children with HD who arrested were sicker (92% vs 62% ASA physical status III–V; P < 0.01) and more likely to arrest from cardiovascular causes (50% vs 38%; P = 0.03), although often the exact cardiovascular cause of arrest could not be determined. Mortality was higher in patients with HD (33%) than those without HD (23%, P = 0.048) but did not differ when adjusted for ASA physical status classification. More than half (54%) of the CA in patients with HD were reported from the general operating room compared with 26% from the cardiac operating room and 17% from the catheterization laboratory. The most common category of HD lesion in patients suffering CA was single ventricle (n = 24). At the time of CA, most patients with congenital HD were either unrepaired (59%) or palliated (26%). Arrests in patients with aortic stenosis and cardiomyopathy were associated with the highest mortality rates (62% and 50%, respectively), although statistical comparison was precluded by small sample size for some HD lesions. CONCLUSIONS: Children with HD were sicker compared with those without HD at the time of anesthesia-related CA and had a higher mortality after arrest. These arrests were reported most frequently from the general operating room and were likely to be from cardiovascular causes. The identification of causes of and factors relating to anesthesia-related CA suggests possible strategies for prevention.

Neurological monitoring for congenital heart surgery.

The incidence of neurological complications after pediatric cardiac surgery ranges from 2% to 25%. The causes are multifactorial and include preoperative brain malformations, perioperative hypoxemia and low cardiac output states, sequelae of cardiopulmonary bypass, and deep hypothermic circulatory arrest. Neurological monitoring devices are readily available and the anesthesiologist can now monitor the brain during pediatric cardiac surgery. In this review we discuss near-infrared cerebral oximetry, transcranial Doppler ultrasound, and electroencephalographic monitors for use during congenital heart surgery. After review of the basic principles of each monitoring modality, we discuss their uses during pediatric heart surgery. We present evidence that multimodal neurological monitoring in conjunction with a treatment algorithm may improve neurological outcome for patients undergoing congenital heart surgery and present one such algorithm.

Factors associated with blood loss and blood product transfusions: a multivariate analysis in children after open-heart surgery.

UNLABELLED In this prospective cohort study of 548 children undergoing open-heart surgery, we evaluated demographic and perioperative factors to identify variables associated with perioperative blood loss and blood product transfusions. Using multivariate analysis, younger patient age was found to be the variable most significantly associated with bleeding and transfusions. Higher preoperative hematocrit, complex surgery, lower platelet count during cardiopulmonary bypass (CPB), and longer duration of deep hypothermic circulatory arrest were also significantly associated with bleeding and transfusion. Excessive postoperative chest tube (CT) drainage was associated with intraoperative bleeding. Independently associated variables accounted for 76% of the variability in CT output measured after 2 h in intensive care. Patients were subdivided into children aged < or =1 yr (infants) and children >1 yr; infants bled more intraoperatively (P<0.005); had greater cumulative CT output at 2, 6, 12, and 24 h (P<0.0001); and received more blood products (P<0.0001). Factors associated with bleeding and transfusions varied with patient age. Lower body core temperature during CPB was highly associated with blood loss and transfusions in infants, whereas resternotomy, preoperative congestive heart failure, and prolonged duration of CPB were significant factors associated with bleeding and transfusions in children >1 yr old. IMPLICATIONS Knowledge of the factors associated with blood loss and blood product transfusions can help to identify children at risk of excessive bleeding after open-heart surgery.

Coagulation Tests During Cardiopulmonary Bypass Correlate With Blood Loss in Children Undergoing Cardiac Surgery

OBJECTIVES To examine whether coagulation tests, sampled before and during cardiopulmonary bypass (CPB), are related to blood loss and blood product transfusion requirements, and to determine what test value(s) provide the best sensitivity and specificity for prediction of excessive hemorrhage. DESIGN Prospective. SETTING University-affiliated, pediatric medical center. PARTICIPANTS Four hundred ninety-four children. INTERVENTIONS Coagulation tests. MEASUREMENTS AND MAIN RESULTS Demographic, coagulation test, blood loss, and transfusion data were noted in consecutive children undergoing cardiac surgery. Laboratory tests included hematocrit (Hct), prothrombin time, partial thromboplastin time (PTT), platelet count, fibrinogen concentration, and thromboelastography. Stepwise linear regression analysis indicated that platelet count during CPB was the variable most significantly associated with intraoperative blood loss (in milliliters per kilogram) and 12-hour chest tube output (in milliliters per kilogram). Other independent variables associated with blood loss were thromboelastography maximum amplitude (MA) during CPB, preoperative PTT, preoperative Hct, and preoperative thromboelastography angle and shear modulus values. Thromboelastography MA during CPB was the only variable associated with total products transfused (in milliliters per kilogram). Of all tests studied, platelet count during CPB (< or = 108,000/microL) provided the maximum sensitivity (83%) and specificity (58%) for prediction of excessive blood loss (receiver operating characteristic analysis). Blood loss was inversely related to patient age; neonates received the most donor units (median, 8 units; range, 6 to 10 units). CONCLUSIONS During cardiac surgery, coagulation tests (including thromboelastography) drawn pre-CPB and during CPB are useful to identify children at risk for excessive bleeding. Platelet count during CPB was the variable most significantly associated with blood loss.

Ketamine does not increase pulmonary vascular resistance in children with pulmonary hypertension undergoing sevoflurane anesthesia and spontaneous ventilation.

BACKGROUND:The use of ketamine in children with increased pulmonary vascular resistance is controversial. In this prospective, open label study, we evaluated the hemodynamic responses to ketamine in children with pulmonary hypertension (mean pulmonary artery pressure >25 mm Hg). METHODS:Children aged 3 mo to 18 yr with pulmonary hypertension, who were scheduled for cardiac catheterization with general anesthesia, were studied. Patients were anesthetized with sevoflurane (1 minimum alveolar anesthetic concentration [MAC]) in air while breathing spontaneously via a facemask. After baseline catheterization measurements, sevoflurane was reduced (0.5 MAC) and ketamine (2 mg/kg IV over 5 min) was administered, followed by a ketamine infusion (10 &mgr;g · kg−1 · min−1). Catheterization measurements were repeated at 5, 10, and 15 min after completion of ketamine load. Data at various time points were compared (ANOVA, P < 0.05). RESULTS:Fifteen patients (age 147, 108 mo; median, interquartile range) were studied. Diagnoses included idiopathic pulmonary arterial hypertension (5), congenital heart disease (9), and diaphragmatic hernia (1). At baseline, median (interquartile range) baseline pulmonary vascular resistance index was 11.3 (8.2) Wood units; 33% of patients had suprasystemic mean pulmonary artery pressures. Heart rate (99, 94 bpm; P = 0.016) and Pao2 (95, 104 mm Hg; P = 007) changed after ketamine administration (baseline, 15 min after ketamine; P value). There were no significant differences in mean systemic arterial blood pressure, mean pulmonary artery pressure, systemic or pulmonary vascular resistance index, cardiac index, arterial pH, or Paco2. CONCLUSIONS:In the presence of sevoflurane, ketamine did not increase pulmonary vascular resistance in spontaneously breathing children with severe pulmonary hypertension.

Pharmacokinetics and side effects of milrinone in infants and children after open heart surgery

We investigated the pharmacokinetics and side effects of milrinone in infants and children (<or=to13 yr) after open heart surgery in this prospective, open-label study. Milrinone binding to cardiopulmonary bypass (CPB) circuitry was also examined in out two groups. Children in the small dose group (n = 11) received two 25-micro g/kg boluses with a final infusion rate of 0.5 micro g [center dot] kg-1 [center dot] min-1; those in the large dose group (n = 8) received a 50-micro g/kg bolus and a 25-micro g/kg bolus with a final infusion rate of 0.75 micro g [center dot] kg-1 [center dot] min-1. Blood samples for milrinone concentration were drawn 30 min after each bolus, at steady state, and after discontinuing the milrinone infusion. Pharmacokinetics were evaluated using traditional and nonlinear mixed effects modeling analysis. Milrinone kinetics best fit a two-compartment model. Steady-state plasma levels in the small and large dose groups were within the adult therapeutic range (113 +/- 39 and 206 +/- 74 ng/mL, respectively). The volumes of distribution (V beta) in infants (0.9 L/kg) and children (0.7 L/kg) were not different, but infants had significantly lower milrinone clearance (3.8 vs 5.9 mL [center dot] kg-1 [center dot] min-1). Thrombocytopenia (defined as platelet count <or=to100,000 mm-3) occurred in 58%, and the risk increased significantly with duration of infusion. Tachyarrythmias were noted in two patients. Milrinone did not bind to CPB circuitry. We conclude that milrinone is cleared more rapidly in children than in adults. The major complication was thrombocytopenia. Implications: Most pediatric dosing is based on data published for adults. Infants and children have kinetics that differ from adults. We studied the distribution of IV milrinone in infants and children after open heart surgery. Milrinone had a larger volume of distribution and a faster clearance in infants and children than in adults, and dosing should be adjusted accordingly. (Anesth Analg 1998;86:283-9)

Effects of Inspired Hypoxic and Hypercapnic Gas Mixtures on Cerebral Oxygen Saturation in Neonates with Univentricular Heart Defects

Background Neonates with functional single ventricle often require hypoxic or hypercapnic inspired gas mixtures to reduce pulmonary overcirculation and improve systemic perfusion. Although the impact of these treatments on arterial oxygen saturation has been described, the effects on cerebral oxygenation remain uncertain. This study examined the effect of these treatments on cerebral oxygen saturation and systemic hemodynamics. Methods Neonates with single ventricle mechanically ventilated with room air were enrolled in a randomized crossover trial of 17% inspired oxygen or 3% inspired carbon dioxide. Each treatment lasted 10 min, followed by a 10–20-min washout period. Cerebral and arterial oxygen saturation were measured by cerebral and pulse oximetry, respectively. Cerebral oxygen saturation, arterial oxygen saturation, and other physiologic data were continuously recorded. Results Three percent inspired carbon dioxide increased cerebral oxygen saturation (56 ± 13 to 68 ± 13%;P < 0.01), whereas 17% inspired oxygen had no effect (53 ± 13 to 53 ± 14%;P = 0.8). Three percent inspired carbon dioxide increased the mean arterial pressure (45 ± 8 to 50 ± 9 mmHg;P < 0.01), whereas 17% inspired oxygen had no effect. And 3% inspired carbon dioxide decreased arterial p H and increased arterial carbon dioxide and oxygen tensions. Conclusions Inspired 3% carbon dioxide improved cerebral oxygenation and mean arterial pressure. Treatment with 17% inspired oxygen had no effect on either.