Is Arrhythmia Detection by Automatic External Defibrillator Accurate for Children?

Background —Use of automatic external defibrillators (AEDs) in children aged <8 years is not recommended. The purpose of this study was to develop an ECG database of shockable and nonshockable rhythms from a broad age range of pediatric patients and to test the accuracy of the Agilent Heartstream FR2 Patient Analysis System for sensitivity and specificity.

Methods and Results —Children aged ≤12 years who either developed arrhythmias or were at risk for developing arrhythmias were studied. Two sources were used for the database: children whose rhythms were recorded prospectively via a modified AED and children who had arrhythmias captured on paper and digitized for subsequent analysis. The rhythms were divided into 5-second strips, classified by 3 reviewers, and then assessed by the AED analysis algorithm. A total of 696 five-second rhythm strips from 191 children (81 female and 110 male) aged 1 day to 12 years (median 3.0 years) were analyzed. There was 100% specificity for nonshockable rhythms. Sensitivity for ventricular fibrillation was 96%.

Conclusions —There was excellent AED rhythm analysis sensitivity and specificity in all age groups for ventricular fibrillation and nonshockable rhythms. The high specificity and sensitivity indicate that there is a very low risk of an inappropriate shock and that the AED correctly identifies shockable rhythms, making the algorithm both safe and effective for children.

Stress response in infants undergoing cardiac surgery: a randomized study of fentanyl bolus, fentanyl infusion, and fentanyl-midazolam infusion

There have been significant changes in the management of neonates and infants undergoing cardiac surgery in the past decade. We have evaluated in this prospective, randomized, double-blinded study the effect of large-dose fentanyl anesthesia, with or without midazolam, on stress responses and outcome. Forty-five patients < 6 mo of age received bolus fentanyl (Group 1), fentanyl by continuous infusion (Group 2), or fentanyl-midazolam infusion (Group 3). Epinephrine, norepinephrine, cortisol, adrenocortical hormone, glucose, and lactate were measured after the induction (T1), after sternotomy (T2), 15 min after initiating cardiopulmonary bypass (T3), at the end of surgery (T4), and after 24 h in the intensive care unit (T5). Plasma fentanyl concentrations were obtained at all time points except at T5. Within each group epinephrine, norepinephrine, cortisol, glucose and lactate levels were significantly larger at T4 (P values < 0.01), but there were no differences among groups. Within groups, fentanyl levels were significantly larger in Groups 2 and 3 (P < 0.001) at T4, and among groups, the fentanyl level was larger only at T2 in Group 1 compared with Groups 2 and 3 (P < 0.006). There were no deaths or postoperative complications, and no significant differences in duration of mechanical ventilation or intensive care unit or hospital stay. Fentanyl dosing strategies, with or without midazolam, do not prevent a hormonal or metabolic stress response in infants undergoing cardiac surgery.

IMPLICATIONS

We demonstrated a significant endocrine stress response in infants with well compensated congenital cardiac disease undergoing cardiac surgery, but without adverse postoperative outcome. The use of large-dose fentanyl, with or without midazolam, with the intention of providing "stress free" anesthesia, does not appear to be an important determinant of early postoperative outcome.

Combined lung and liver transplantation in a girl with cystic fibrosis

PURPOSE

To describe the anesthetic considerations of a combined lung and liver transplant in a 14-yr-old girl with cystic fibrosis.

CLINICAL FEATURES

A 14 yr-old girl with cystic fibrosis presented for combined liver and lung transplantation. Anesthetic management was complex in that the pulmonary, hemodynamic, and hematological changes after cardiopulmonary bypass and lung transplantation made the management of the subsequent liver transplant unique. We used a moderate dose fentanyl and isoflurane anesthetic with invasive monitoring including a pulmonary artery catheter. Upon reperfusion of the new liver our patient exhibited severe pulmonary hypertension that was associated with a decrease in cardiac output and systemic hypotension. Utilizing a pulmonary artery catheter, this episode was treated with an increase of prostaglandin E1 (PGE1) infusion to 0.025 microg x kg(-1) x min(-1) and the initiation of 3 microg x kg(-1) x min(-1) dobutamine. The pulmonary hypertension resolved and the cardiac output and blood pressure returned to baseline levels.

CONCLUSION

The anesthetic considerations for a combined lung and liver transplant are complex because of the interactions and alterations in cardiovascular, pulmonary and hemostatic systems. The use of a pulmonary artery catheter was critical to the management of our patient because it allowed us to accurately treat an episode of hypotension occurring during liver transplantation. This episode was secondary to acute pulmonary hypertension which is common after pulmonary transplantation but unusual during liver transplantation. It is also critical that a team approach is used to consider all of the concerns of the multiple services managing these complex patients.

Prevalence of factor V Leiden in a population of patients with congenital heart disease

PURPOSE

The incidence of thrombotic events following cardiopulmonary bypass (CPB) in patients receiving surgical repair or palliation of congenital heart defects (CHD) is as high as 16%. Protein C, an intrinsic anticoagulation protease which, when activated, breaks down factor Va of the coagulation system, aids in maintaining a normal procoagulant/anticoagulant balance. Resistance of factor Va to degradation by activated protein C occurs and predisposes to thrombotic events. The resistance of factor Va to such degradation is, in the majority of cases, due to a genetic mutation referred to as factor V Leiden (FVLeiden). The presence of FVLeiden can be diagnosed using a DNA based assay. The prevalence of FVLeiden in the with CHD has not been determined. The objective of this study was to determine the prevalence of FVLeiden in patients with CHD.

METHODS

Two hundred consecutive patients with CHD undergoing surgical repair or palliation requiring cardiopulmonary bypass were studied. Blood was taken before administration of homologous blood transfusion and assayed using a DNA based method with polymerase chain reaction amplification for the FVLeiden mutation.

RESULTS

The prevalence of FVLeiden in our study population was 9/200 (4.5%). None of these patients demonstrated thrombotic complications. However, three patients (1.5%) without the FVLeiden mutation developed postoperative thrombotic complications.

CONCLUSIONS

The prevalence of FVLeiden in patients is 4.5% that is not different from that of the population at large. There was no identifiable association with the occurrence of postoperative thrombotic events.

A new anesthetic system for microlaryngeal surgery

Anesthesia for microlaryngeal surgery creates many obstacles for the anesthesiologist and otolaryngologist. Anesthetic techniques developed to improve surgical exposure have been met with significant limitations and are difficult for the anesthesiologist to monitor. A new subglottic jet ventilation anesthesia system is introduced that meets the needs of the otolaryngologist and the anesthesiologist. This new system is made up of two components: (1) The Hunsaker Mon-Jet tube is a laser-safe, subglottic jet ventilation tube constructed of a nonflammable fluoroplastic material. It allows monitoring of tracheal pressure and end tidal carbon dioxide, and it is designed with a basket-shaped distal extension to align the jet port away from the tracheal mucosa and to prevent trauma and submucosal injection of jetted gas. (2) An automatic jet ventilator, which has an adjustable respiratory rate, inspiratory/expiratory ratio, and flow rate, also monitors expiratory end peak airway pressures and has an automatic shutdown feature if either of these pressures are exceeded. This system was successfully used in 36 patients undergoing microlaryngeal surgery.

The limits of detectable cerebral perfusion by transcranial Doppler sonography in neonates undergoing deep hypothermic low-flow cardiopulmonary bypass

OBJECTIVE

Neurologic morbidity including seizures, abnormal neurologic function, and delayed psychomotor development continue to be significant problems for some patients undergoing operations for congenital heart disease, particularly for those subjected to deep hypothermic circulatory arrest. The technique of low-flow cardiopulmonary bypass has been advocated to decrease the incidence of neurologic sequelae. Our study examined the limits of detectable blood flow in the middle cerebral artery during low-flow cardiopulmonary bypass in 28 neonates undergoing the arterial switch procedure.

METHODS

Cerebral blood flow velocity was measured noninvasively in the M1 segment of the middle cerebral artery with a 2 MHz range-gated pulsed-wave transcranial Doppler sonographic probe that was placed over the left temporal window. As part of the initiation of a planned period of deep hypothermic circulatory arrest, the cardiopulmonary bypass flow rate was decreased in stages to five low-flow rates (50, 40, 30, 20, and 10 ml/kg per minute). After a period of stabilization, cerebral blood flow velocities were recorded at each of the five low-flow rates and reported as a percentage of baseline.

RESULTS

All 28 neonates had detectable perfusion in the middle cerebral artery at flow rates of 30 ml/kg per minute or higher. At flows of 20 and 10 ml/kg per minute, one and eight, respectively, of the 28 neonates had no detectable perfusion in the middle cerebral artery.

CONCLUSIONS

Our data show that cerebral perfusion can be detected by transcranial Doppler sonography in the middle cerebral artery in some neonates at bypass pump flows as low as 10 ml/kg per minute. However, when transcranial Doppler sonography was used in our patient population, a minimum bypass flow rate of 30 ml/kg per minute was needed to detect cerebral perfusion in all neonates.

The efficacy of tranexamic acid versus placebo in decreasing blood loss in pediatric patients undergoing repeat cardiac surgery

The antifibrinolytic drug, tranexamic acid, decreases blood loss in adult patients undergoing cardiac surgery. However, its efficacy has not been extensively studied in children. Using a prospective, randomized, double-blind study design, we examined 41 children undergoing repeat sternotomy for repair of congenital heart defects. After induction of anesthesia and prior to skin incision, patients received either tranexamic acid (100 mg/kg, followed by 10 mg.kg-1.h-1) or saline placebo. At the onset of cardiopulmonary bypass, a second bolus of tranexamic acid (100 mg/kg) or placebo was administered. Total blood loss and transfusion requirements during the period from protamine administration until 24 h after admission to the intensive care unit were recorded. Children who were treated with tranexamic acid had 24% less total blood loss (26 +/- 7 vs 34 +/- 17 mL/kg) compared with children who received placebo (univariate analysis P = 0.03 and multivariate analysis P < 0.01). Additionally, the total transfusion requirements, total donor unit exposure, and financial cost of blood components were less in the tranexamic acid group. In conclusion, tranexamic acid can reduce perioperative blood loss in children undergoing repeat cardiac surgery.

Propofol and alfentanil prevent the increase in intraocular pressure caused by succinylcholine and endotracheal intubation during a rapid sequence induction of anesthesia

The increase in intraocular pressure (IOP) associated with succinylcholine (Sch) has made its use in patients with open globe injuries controversial. Studies that have examined techniques to prevent the increase in IOP due to Sch have shown a larger increase in IOP from the stimulus of laryngoscopy and endotracheal intubation. The purpose of our study was to examine whether the combination of propofol and alfentanil would prevent the increase in IOP due to Sch as well as endotracheal intubation during a rapid sequence induction of anesthesia. Sixty patients were randomized to receive either thiopental 5 mg/kg and Sch 1.5 mg/kg (Group I), propofol 2 mg/kg and Sch 1.5 mg/kg (Group II), or propofol 2 mg/kg, alfentanil 40 micrograms/kg, and Sch 1.5 mg/kg (Group III). The IOP was measured continuously from baseline awake (control) values until 15 s after successful intubation. All three groups had a significant decrease in IOP with the induction of anesthesia. Succinylcholine produced a consistent increase in IOP from the postinduction low in Groups I and II, but this increase was not significantly higher than baseline. The postintubation IOPs in Groups I and II were significantly higher than baseline (P < 0.001). During the entire study period, the IOP in Group III never increased above baseline. The IOP in Groups I and II had already begun to decline by 15 s postintubation, suggesting that laryngoscopy and intubation have the greatest effect on increasing IOP. We conclude that the combination of propofol and alfentanil prevents the increase in IOP from Sch as well as the increase associated with endotracheal intubation during a rapid sequence induction of anesthesia.