Victor C. Baum

Very early extubation in children after cardiac surgery.

Objective Very early extubation of children after cardiac surgery has been suggested as a safe alternative to prolonged postoperative intubation but is still not common practice. Studies of early extubation in children may not have described reasons for failure to extubate, or have included nonbypass or only low-risk repairs. We present our experience with very early extubation in an inclusive group of children after cardiac surgery. Design Retrospective chart review. Setting University hospital operating room and pediatric intensive care unit (ICU). Patients A total of 102 consecutive children (age <18 yrs) undergoing cardiac surgery requiring cardiopulmonary bypass. Main Results Forty-eight patients were extubated early (88% in the operating room, 12% on arrival in ICU). Patients extubated late were younger (13.8 ± 26.2 vs. 47.6 ± 44.5 months), smaller (8.1 ± 10.7 vs.17.5 ± 14.2 kg), and had higher ASA scores than patients extubated early (p < .001 for all). The youngest patient extubated early was 2 months old (range, 2–192 months). Paco2 on ICU arrival was higher in the early extubation group (52.4 ± 6.9 vs. 41.2 ± 14.7 mm Hg [7.0 ± 0.9 vs. 5.5 ± 2.0 kPa], p < .001), and pH was lower (7.27 ± 0.04 vs. 7.37 ± 0.16, p < .001). Use of subarachnoid morphine did not affect ability to extubate early. No patients in the early extubation group required special airway support, reintubation, or increased inotropic support after ICU admission. Conclusions Successful early extubation of even young children is possible and easily accomplished in most children undergoing cardiopulmonary bypass, even with complex procedures, but advantages of extubation in the operating room vs. immediate ICU extubation remain unclear. Transient mild-to-moderate mixed acidosis is common and requires no treatment. Full implementation requires acceptance by surgical and ICU staffs.

Difficult airway management in the neonate: a simple method of intubating through a laryngeal mask airway.

Tracheal intubation through a laryngeal mask airway is one option for securing an airway in the patient with a difficult airway. A variety of techniques and equipment have been used to stabilize the position of the tracheal tube while removing the laryngeal mask airway. We have shown that if a fibreoptic bronchoscope is used to place an tracheal tube through a laryngeal mask in neonates, additional equipment is not needed to remove the laryngeal mask airway without endangering tracheal tube placement. This is possible even in small neonates.

Immediate 8% sevoflurane induction in children : A comparison with incremental sevoflurane and incremental halothane

We compared the efficacy and tolerance of pediatric inductions with immediate 8% sevoflurane in 70% nitrous oxide with either incremental sevoflurane or incremental halothane in 70% nitrous oxide.Forty-six unpremedicated children had anesthesia induced by immediate 8% sevoflurane (high sevoflurane [HS]; circuit primed with 70% N2 O and 8% sevoflurane before application of the face mask), gradual sevoflurane (GS; primed with 70% N2 O with increments of sevoflurane), and gradual halothane (HAL; 70% N2 O with incremental halothane). Blind video recordings were made, and each childs distress was rated prior to mask application, during mask application, and every 10 s thereafter using a behavioral rating scale. There were no complications. Of those subjects not quiet and cooperative throughout, times to complete quiet were significantly different (P = 0.001): HS 19.8 +/- 8 s (range 9-34); GS 52 +/- 17 s (range 8-73); HAL 43 +/- 22 s (range 13-73). Times to eye closure were also significantly different (P < 0.001): HS 37 +/- 10 s (range 15-56); GS 70 +/- 18 s (range 35-114); HAL 81 +/- 34 s (range 55-140). Distress scale scores showed more rapid decrement with HS than with GS or HAL. We conclude that 1) immediate 8% sevoflurane/N2 O results in a significantly faster induction than GS or HAL; 2) in children, HS in N2 O will not result in a single-breath induction under the conditions of this study; 3) in this small group, HS was extremely well tolerated in ASA class I and II patients. (Anesth Analg 1997;85:313-6)

When nitrous oxide is no laughing matter: nitrous oxide and pediatric anesthesia

Although often felt to be relatively innocuous, nitrous oxide can have significant metabolic effects in settings of abnormal vitamin B12 and B12‐related metabolism in children. These conditions can be genetic or environmental. Symptoms may not appear until days to weeks after exposure to nitrous oxide. Although overt genetic diseases are relatively uncommon, the implications of nitrous oxide interactions with much more frequent but less symptomatically obvious single nucleotide polymorphisms are potentially more concerning. In addition, nitrous oxide can have direct and differing neurotoxic effects on both immature and aged brain, the clinical impact of which remains undetermined.

Are we improving after 10 years of humanitarian paediatric cardiac assistance

BACKGROUND Paediatric cardiovascular services are frequently absent or poorly developed in many countries around the world. Our foundation made 83 trips in support of cardiovascular services between April 1993 and March 2003 to help alleviate this problem. In this study, we present an analysis of our results over these period of 10 years. METHODS We performed a review of all available records relating to the trips, including patient databases, audited financial statements, donated product inventory lists, lists of team members, and follow-up data from the host sites concerning the state of the patients treated. RESULTS We made 83 trips to 14 countries, 40 of these being in Central Europe, 5 in Eastern Europe, 10 in Caribbean, and Central America, 18 in South America, 9 in Asia, and 1 in the Middle East. In the first 5 years, we made 23, as opposed to 60 in the second 5 years, this difference being significant (p less than 0.01). The total number of primary operations performed over 10 years was 1,580. The number of procedures performed yearly increased over the two intervals from 97.0 plus or minus 32.7 to 219.0 plus or minus 41.7, p less than 0.002. The probability of survival between the periods increased from 84.6 to 93.3 per cent, and this was also significantly different (p less than 0.001). Overall, the rate of survival for the period of 10 years was 90.5 per cent. Moreover, the value of services donated to support each trip also differed significantly, decreasing from 105,900 dollars plus or minus 14,581 dollars for the first period to 54,617 dollars plus or minus 11,425 dollars for the second period (p less than 0.001). CONCLUSIONS Improving paediatric cardiac services in under-served countries requires significant financial and personnel commitments, but can produce reasonable outcomes.

Sodium-Calcium Exchange in Neonatal Myocardium: Reversible Inhibition by Halothane

Neonatal myocardium is distinctly more sensitive to extracellular calcium levels than is mature myocardium. This has been ascribed to the poorly developed sarcoplasmic reticulum of neonatal myocardium. Recent evidence has suggested that there is an increased dependence of neonatal myocardium on the sodium-calcium exchange current, and that sodium-calcium exchange may be a major source of calcium influx in neonatal myocardial cells. We determined the effect of halothane on the sodium-calcium exchange current on single neonatal (2- to 5-day-old) rabbit ventricular myocytes by means of the whole cell voltage clamp. Lower (1.5%) halothane decreased sodium-calcium exchange current by 49%, from 29 +/- 3 to 15 +/- 6 pA. Higher (3%) halothane decreased this current by 66%, from 50 +/- 9 to 17 +/- 9 pA. Thus halothane has a reversible inhibition of sodium-calcium exchange current in neonatal myocardium. Inhibition of sodium-calcium exchange current would be expected to have a magnified effect on contractility in neonatal as opposed to adult myocardium, and could theoretically ameliorate reperfusion injury due to influx of calcium via the sodium-calcium exchanger.

Paediatric cardiac assistance in developing and transitional countries: the impact of a fourteen year effort.

BACKGROUND Paediatric cardiac services are poorly developed or totally absent in underdeveloped countries. Institutions, foundations and interested individuals in those nations in which sophisticated paediatric cardiac surgery is practised have the ability to alleviate this problem by sponsoring paediatric cardio-surgical missions to provide care, and train local caregivers in developing, transitional, and third world countries. The ultimate benefit of such a programme is to improve the surgical abilities of the host institution. The purpose of this report is to present the impact of our programme over a period of 14 years. METHODS We specifically reviewed our database of patients from our missions, our team lists, surgical results, and the number and type of personnel trained in the institutions that we have assisted. In order for the institution to be entered into the study, the foundation had to provide at least 2 months of training. In addition, the institution had to respond to a simple questionnaire concerning the number and types of surgery performed at their facility before and after intervention by the foundation. RESULTS We made 140 trips to 27 institutions in 19 countries, with 12 of the visited institutions qualifying for inclusion. Of these, 9 institutions reported an increase in the number and complexity of cases currently being performed in their facility since the team intervened. This goal had not been accomplished in 3 institutions. The reasons for failure included the economic situation of the country, hospital and national politics, personality conflicts, and continued lack of hardware and disposables. CONCLUSIONS Paediatric cardiac service assistance can improve local services. A significant commitment is required by all parties involved.

Effects of halothane and ketamine on activation and inactivation of myocardial calcium current

Summary: We evaluated the effects of clinically relevant concentrations of halothane (1%) and ketamine (10-4M) on activation, inactivation, and recovery from inactivation of voltage-gated sarcolemmal calcium current (ICa) in single guinea pig ventricular myocytes, using the whole cell voltage clamp. Both anesthetics had qualitatively similar effects. The potential at half-activation was shifted from - 18 to - 23 mV for halothane (p < 0.03) and from −17 to −21 mV for ketamine (p = 0.005). There was no change in the slope of the activation curve for either anesthetic. The potential at half-inactivation was shifted from - 29 to - 40 mV with exposure to halothane (p < 0.001) and from −27 to −33 mV (p < 0.001) with exposure to ketamine. There was no change in the slope of the inactivation curve with either agent. The changes in time constant of recovery from steady-state inactivation with halothane did not reach statistical significance (178 vs. 207 ms, p = 0.20) and was significantly prolonged with exposure to ketamine (106 vs. 157 ms, p = 0.005). The two anesthetics show parallel shifts in activation, inactivation, and recovery from inactivation of ICa in ventricular myocardial cells. These findings in normal ventricular myocytes may help interpret the interactions of these anesthetics with other types of heart muscle, such as ischemic and immature myocardium.

Cardiac trauma in children

Major cardiac trauma in children is a relatively uncommon event, but one that can have signi®cant anaesthetic implications. Despite potential severe consequences, cardiac trauma is often overlooked or covered only minimally in discussions of paediatric trauma (1,2). A recent editorial on severe paediatric trauma in Paediatric Anaesthesia, for example, made no mention of cardiac trauma (3). Cardiac trauma in adults has been recently reviewed (4). This review will discuss the epidemiology, physiology and anaesthetic implications of blunt and penetrating cardiac injury speci®cally in childhood, given the relatively limited amount of information available explicitly about paediatric cardiac injury. It is limited to injury to the heart. Wider thoracic injury, to the chest wall, lungs and great vessels, is not discussed. Cardiac trauma is classically divided into blunt and penetrating trauma. However, it must be appreciated that there is signi®cant overlap in the clinical sequelae.

Effects of Isoflurane on Electrophysiological Measurements in Children with the Wolff‐Parkinson‐White Syndrome

This study was designed to assess the effects of isoflurane (ISO) on the electrophysiological properties of the accessory pathway, atrium, ventricle, and AV node in children with the Wolff‐Parkinson‐White (WPW) syndrome. The results of programmed electrical stimulation were analyzed in 51 patients (4 months to 17 years of age) with WPW. The study population was divided into two groups. Twenty‐seven patients received local anesthesia and intramuscular injection of meperidine, promethazine, and chlorpromazine (MPC group). Twenty‐four patients received general anesthesia with ISO inhalation (ISO group). We compared the antegrade effective refractory period of the accessory pathway (antegrade APERP), ventricular effective refractory period (VERP), atrial effective refractory period (AERP), AH interval, and cycle length of circus movement tachycardia (CMT‐CL) in 12 pairs of age and sex matched patients selected from the MPC and ISO groups. Of the 12 pairs of age and sex matched patients, antegrade APERP in patients who received ISO (299 ± 17 ms, mean ± SEM) was significantly longer as compared with matched patients in the MPC group (262 ± 5 ms, P < 0.025). The VERP and AERP in patients from the ISO group were significantly prolonged compared with the MPC patients (239 ± 7 vs 210 ± 8 ms, P < 0.025, and 228 ± 11 vs 180 ± 6 ms, P < 0.01, respectively). There was no significant difference in the AH interval or CMT‐CL between the two subgroups. Thus, ISO prolongs the antegrade APERPs as well as the effective refractory periods of atrial and ventricular muscle in children with WPW, while the AH interval and CMT‐CL appear to be unaffected. Care must be taken in interpreting measurements of the antegrade APERP made in patients under general anesthesia for RF ablation of accessory pathways.