What happens when chest tubes are removed in children?

OBJECTIVE: To evaluate the incidence, onset, and severity of complications in children after chest tube removal. DESIGN: A prospective evaluation of patients. SETTING: Pediatric intensive care unit in a tertiary care university hospital. PATIENTS: One hundred and one consecutive children requiring intraoperative placement of chest tubes for cardiac or noncardiac thoracic surgery. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Of the 120 chest tubes placed in 101 patients, 16 were associated with positive findings after removal. Of these 16, only six required changes in management, and only two were serious complications. There was no association of complications with duration of chest tube placement. Children who developed complications were younger. All serious complications were immediately apparent after chest tube removal. CONCLUSION: Serious complications of chest tube removal in children are very uncommon and in this series were immediately apparent.

Influence of congenital heart disease on mortality after noncardiac surgery in hospitalized children

OBJECTIVE

To evaluate the incremental risk of congenital heart disease on mortality after noncardiac surgery in children.

DESIGN

We reviewed the clinical information network database of the University Hospital Consortium for the period January 1, 1993, through December 31, 1996, and identified 191 261 patients <18 years old having 1 or more noncardiovascular surgical procedures. Of these patients, 6.5% had a diagnosis of congenital heart disease. Patients having ambulatory surgery are excluded from this database. Short-term (1-, 2-, and 3-day) and 30-day mortality were compared, as well as mortality for neonates, infants (31 days to 1 year), and older children (1-17 years); mortality for the 100 most common surgical procedures, mortality for 10 relatively minor surgical procedures, and mortality in subgroups of patients with minor versus severe cardiac diagnoses.

RESULTS

Short-term and 30-day mortality was increased in the patients with congenital heart disease patients (30-day mortality odds ratio 3.5; 95% confidence limit, 3.2-3.9). Mortality was also increased in patients with congenital heart disease in the 2 youngest age groups, for the 100 most common operations, and for 10 relatively minor operations. Children with more severe heart disease diagnoses had higher mortality than did children carrying less serious cardiac diagnoses.

CONCLUSION

A diagnosis of congenital heart disease adds significant incremental risk of mortality in children requiring inpatient noncardiovascular surgery. This outcome difference is present for both minor and major surgical procedures, and regardless of whether mortality is measured at 1, 3, or 30 days. The incremental risk is greatest in neonates and infants where the presence of congenital heart disease is associated with a 2-fold increase in mortality from noncardiac surgery.

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% N2O and 8% sevoflurane before application of the face mask), gradual sevoflurane (GS; primed with 70% N2O with increments of sevoflurane), and gradual halothane (HAL; 70% N2O with incremental halothane). Blind video recordings were made, and each child's 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/N2O results in a significantly faster induction than GS or HAL;2) in children, HS in N2O 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.

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.

The adult patient with congenital heart disease

In adults with congenital heart disease who are confronted with noncardiac surgery, perioperative risks can be reduced, often appreciably, when problems inherent to this patient population are anticipated. The first necessity is to clarify the diagnosis and to be certain that appropriate information is obtained from a cardiologist with adequate knowledge of congenital heart disease in adults. Physiology and anatomy can vary significantly among patients who superficially carry identical diagnoses. Elective noncardiac surgery should be preceded by clinical assessment including review of clinical and laboratory data and securing the results of necessary diagnostic studies. Preoperative assessment should be performed far enough in advance of the anticipated date of surgery to allow critical assessment of the data and potential discussions with colleagues. Appropriate cardiovascular laboratory studies to be obtained or reviewed include electrocardiograms, chest radiographs, echocardiograms, and cardiac catheterization data, which may include specialized intracardiac electrophysiologic testing. Congenital heart disease in adults is a new and evolving area of special interest and expertise in cardiovascular medicine. Multidisciplinary centers for the care of these patients are being developed. The 22nd Bethesda Conference recommended that these centers include among their consultants anesthesiologists with special expertise in managing patients with congenital heart disease. These anesthesiologists can have the option of serving either as the attending anesthesiologists when patients require noncardiac surgery or as consultants and resource individuals to other anesthesiologists.

Effect of airway pressure on inferior vena cava pressure as a measure of central venous pressure in children

We evaluated the effect of elevated airway pressure on the validity of intravascular pressure obtained in the distal inferior vena cava (IVC) as a measure of central venous pressure (CVP) in a group of children receiving mechanical ventilation. The IVC pressure correlated well with CVP in the patients without abdominal distention, but the disparity was wider in those with abdominal distention. Elevated mean airway pressure or positive end-expiratory pressure had no effect on the relationship of IVC to CVP.

Effects of infused epinephrine on slow phase of O2 uptake kinetics during heavy exercise in humans

We tested the hypothesis that infused epinephrine (Epi) would augment the slow phase of oxygen uptake (VO2) during heavy exercise. Six normal healthy males initially performed a ramp test on a cycle ergometer to estimate the lactate threshold (LT) and determine peak VO2. Each subject then performed two 20-min constant-load tests at a power output calculated to elicit a VO2 equal to estimated LT + 0.2(peak VO2--estimated LT) under control conditions throughout and with an intravenous infusion of Epi from minutes 10 to 20 at a rate of 100 ng.kg-1.min-1. Pulmonary gas exchange variables were determined breath by breath. Arterialized venous blood was repeatedly sampled from the dorsum of the heated hand. Epi infusion elevated (P < 0.05) plasma Epi concentration (i.e., from 420 +/- 130 pg/ml at minute 10 to 2,190 +/- 410 pg/ml at minute 20) but had no effect on plasma norepinephrine or K+ concentrations. Concentrations of blood lactate and pyruvate were increased, pH was decreased, and base excess became more negative by infusion of Epi (P < 0.05). Epi infusion increased (P < 0.05) CO2 production and the respiratory exchange ratio but had no effect on ventilation or VO2. VO2 increased (P < 0.05) to the same extent in both control (3.14 +/- 0.12 l/min at minute 10, 3.28 +/- 0.12 l/min at minute 20) and Epi infusion (3.10 +/- 0.11 l/min at minute 10, 3.25 +/- 0.11 l/min at minute 20) trials. We therefore concluded that neither Epi nor its associated humoral consequences contribute significantly to the slow phase of VO2 kinetics during heavy exercise.

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.

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

We evaluated the effects of clinically relevant concentrations of halothane (1%) and ketamine (10(-4) M) 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.

Inferior vena caval pressure reliably predicts right atrial pressure in pediatric cardiac surgical patients

OBJECTIVE

To compare "central venous pressure" in pediatric patients in a clinical setting as measured from catheters in the infrahepatic inferior vena cava and the right atrium.

DESIGN

Prospective, unblinded study.

SETTING

Cardiothoracic intensive care unit of a tertiary care university hospital.

PATIENTS

Thirty-three pediatric cardiac surgical patients, 2 days to 92 months of age (mean 24 +/- 4 months).

INTERVENTIONS

All patients had intraoperative placement of an 8-cm, double-lumen, femoral venous catheter and a transthoracic right atrial catheter. Patients were studied for 0 to 2 days after surgery.

MEASUREMENTS AND MAIN RESULTS

Measurements were obtained during mechanical and spontaneous ventilation. Although not statistically identical, measurements of "central" venous pressure in the inferior vena cava and right atrium correlated well (r2 = .87 for mechanical ventilation; r2 = .83 for spontaneous ventilation). Of 31 data pairs in mechanically ventilated patients, the absolute difference in pressures was as large as 3 mm Hg in three patients and <3 mm Hg in all the rest. In 15 spontaneously breathing patients, there were only three data measurements where the difference in pressure was 2 mm Hg and none of the differences was greater. In spontaneously breathing patients, the phasic changes due to respiratory variations in venous pressure were in phase in both the intrathoracic and intra-abdominal catheter positions.

CONCLUSIONS

We conclude that while "central" venous pressures measured in the inferior vena cava and in the right atrium are not statistically identical, any differences are well within clinically important limits. Placement of central venous pressure catheters in the inferior vena cava by the femoral venous approach is a reliable alternative to cannulating the superior vena cava in pediatric patients without clinically important intra-abdominal pathology and with anatomic continuity of the inferior vena cava with the right atrium. Relatively short femoral vein catheters allow adequate measurement of central venous pressure without concern for exact catheter tip position and without the risk of right atrial perforation, intracardiac arrhythmias, and inadvertent puncture of carotid and intrathoracic structures. Unlike previously reported results in neonates, we found that the phasic changes of venous pressure with the respiratory cycle were similar in both intrathoracic and intra-abdominal recordings, making this an inappropriate clinical indicator of venous catheter tip position.

Anesthetic implications of adults with congenital heart disease

In adults with congenital heart disease who are confronted with noncardiac surgery, perioperative risks can be reduced, often appreciably, when problems inherent to this patient population are anticipated. The first necessity is to clarify the diagnosis and to be certain that appropriate information is obtained from a cardiologist with adequate knowledge of congenital heart disease in adults. Physiology and anatomy can vary significantly among patients who superficially carry identical diagnoses and would seem to fit under the same rubric. Elective noncardiac surgery should be preceded by clinical cardiovascular assessment, including reviewing clinical and laboratory data and securing necessary diagnostic studies. Preoperative assessment should be performed far enough in advance of the anticipated surgery to allow for critical assessment of the data. Appropriate cardiovascular laboratory studies to be obtained or reviewed include electrocardiograms, chest radiographs, echocardiograms, and cardiac catheterization data (which may include specialized intracardiac electrophysiologic testing). Congenital heart disease in adults is a new and evolving area of special interest and expertise in cardiovascular medicine. Multidisciplinary centers for the care of these patients are being developed. The 22nd Bethesda Conference recommended that these centers include anesthesiologists with special expertise in managing patients with congenital heart disease among their consultants. These anesthesiologists can function either as attending anesthesiologists when patients require noncardiac surgery, or as consultants and resource individuals to other anesthesiologists. Adults with congenital heart disease may present with age-related acquired cardiovascular and noncardiovascular disorders in addition to postoperative cardiac residua and sequelae, all of which require meticulous preoperative planning and consultation before noncardiac surgery is performed. We recommend that, particularly in larger departments of anesthesiology, select members of the department serve as consultants to anesthesiologists and to other members of the medical staff for these cases, especially when large numbers of adults with congenital heart disease are to be treated.

Distinctive effects of three intravenous anesthetics on the inward rectifier (IK1) and the delayed rectifier (IK) potassium currents in myocardium: implications for the mechanism of action

The mechanism(s) of action of anesthetics on cell membrane ionic currents are not known. To investigate this further the effects of clinically relevant concentrations of ketamine, methohexital, and propofol on the delayed rectifier (IK) and the inward rectifier (IK1) currents of single dispersed guinea pig ventricular myocytes were studied. These voltage-gated currents are major components of cardiac cell electrophysiologic function regulating resting potential and repolarization. Each of the three anesthetics had a distinct spectrum of activity. Ketamine (10(-4) M) decreased IK1 (P < 0.05) but had no effect on IK. Methohexital (10(-4) M) had no significant effect on either current. Propofol (2.8 x 10(-5) M) resulted in significant depression of IK (P < 0.001) but had no effect on IK1. These results suggest that these intravenous anesthetics may have more specific effects on sarcolemma than volatile anesthetics, whose effects may be more generalized membrane effects.

Progesterone potentiation of bupivacaine arrhythmogenicity in pentobarbital-anesthetized rats and beating rat heart cell cultures

The effects of progesterone treatment on bupivacaine arrhythmogenicity in beating rat heart myocyte cultures and on anesthetized rats were determined. After determining the bupivacaine AD50 (the concentration of bupivacaine that caused 50% of all beating rat heart myocyte cultures to become arrhythmic), we determined the effect of 1-hour progesterone HCl exposure on myocyte contractile rhythm. Each concentration of progesterone (6.25, 12.5, 25, and 50 micrograms/ml) caused a significant and concentration-dependent reduction in the AD50 for bupivacaine. Estradiol treatment also increased the arrhythmogenicity of bupivacaine in myocyte cultures, but was only one fourth as potent as progesterone. Neither progesterone nor estradiol effects on bupivacaine arrhythmogenicity were potentiated by epinephrine. Chronic progesterone pretreatment (5 mg/kg/day for 21 days) caused a significant increase in bupivacaine arrhythmogenicity in intact pentobarbital-anesthetized rats. There was a significant decrease in the time to onset of arrhythmia as compared with control nonprogesterone-treated rats (6.2 +/- 1.3 vs. 30.8 +/- 2.5 min, mean +/- SE). The results of this study indicate that progesterone can potentiate bupivacaine arrhythmogenicity both in vivo and in vitro. Potentiation of bupivacaine arrhythmia in myocyte cultures suggests that this effect is at least partly mediated at the myocyte level.

Will the calcium channel agonist BAY K8644 inhibit halothane-induced impairment of calcium current?

The inhaled anesthetics impair transsarcolemmal calcium entry (ICa) in myocardial cells, although the mechanism of this interaction is not known. This inhibition of calcium entry has been implicated in the myocardial depression of the volatile anesthetics. To further characterize this interaction and to evaluate whether a calcium channel agonist could attenuate or prevent the inhibition of calcium entry, the effect of the calcium channel agonist BAY K8644 on the impairment of ICa by halothane was evaluated in single guinea pig ventricular myocytes. Calcium currents were evoked by means of the whole-cell voltage-clamp technique. Baseline peak ICa was higher in the cells exposed to 5 microM BAY K8644 (311 vs 206 pA/cm2, P less than 0.04). On exposure to 1% halothane, peak ICa was impaired to an identical degree whether or not cells were exposed to BAY K8644 (78% and 79% of baseline value). This is consistent with the suggestion that the effects of these agents on ICa are nonspecific. However, the increase in ICa suggests that appropriate calcium channel agonists might serve to ameliorate the myocardial depressant effects of halothane.

Ketamine inhibits transsarcolemmal calcium entry in guinea pig myocardium: direct evidence by single cell voltage clamp

To clarify the direct effect of ketamine on calcium entry into myocardium, we directly measured transsarcolemmal calcium entry into single enzymatically dissociated guinea pig myocardial cells by means of the whole cell voltage clamp. Cells were studied in the presence of 0, 10(-5) M, or 10(-4) M ketamine. Peak baseline calcium current was similar in all three groups (911 +/- 92 pA, 954 +/- 66 pA, and 962 +/- 54 pA, respectively). During exposure to ketamine, peak calcium current was unchanged in the no-ketamine control group (886 +/- 74 pA) but decreased in both the 10(-5) M group (723 +/- 38 pA) and the 10(-4) M group (798 +/- 62 pA) (P less than 0.002 vs no-ketamine cells for both groups). We conclude that ketamine has a direct inhibitory effect on transsarcolemmal calcium influx in guinea pig myocardial cells.

Cardiac myosin isoenzyme shifts in non-insulin treated spontaneously diabetic rats

We evaluated myocardial myosin isoform distribution in a group of diabetic BB/W rats from which insulin was withheld for varying periods in order to evaluate the time course and extent of myosin isoform shifts in these animals. Prior studies of myosin isoform distribution in diabetic rats have utilized chemically induced diabetic rats or insulin-treated BB/W rats. Following a stabilization period on insulin therapy, insulin was withheld for 9-28 days during which the animals received supplemental parenteral bicarbonate and Ringer's lactate. Left ventricular myocardial myosin isoform distribution was determined by nondenaturing pyrophosphate gel electrophoresis. We found that the normal predominance of V1 isomyosin in these rats was shifted to V3 predominance by approximately two weeks after the cessation of insulin therapy. This was significantly sooner than was seen in another study which utilized insulin treated BB/W rats, and is similar to the time course seen with chemically induced diabetic rats. In addition, the normal V1 myosin isoform distribution observed during insulin therapy and the progressive shift to the V3 isoform distribution during increasing periods without insulin suggest that this shift can be prevented with insulin alone.

Abnormal cardiac function after exercise in insulin-dependent diabetic children and adolescents

We evaluated the cardiac response to dynamic exercise in a group of otherwise healthy insulin-dependent older children and adolescents and in a nondiabetic control group by postexercise echocardiography. Both groups had similar left ventricular function at rest. After exercise we found abnormalities in the indicators of systolic function, fractional shortening (0.37 vs. 0.43) and rate-corrected velocity of circumferential fiber shortening (2.80 vs. 3.35 circumferences/s). In addition, we found an association of flattened interventricular septal motion with finger contractures in the diabetic subjects. Echocardiographic abnormalities in asymptomatic young diabetic adolescents can be elucidated by postexercise echocardiography. Postexercise echocardiography is a noninvasive procedure that can easily be done in the adolescent population and is useful for evaluating subclinical cardiomyopathy.

Pulsus paradoxus in a patient with tricuspid atresia and hypoplastic right heart

Increased inspiratory right ventricular filling with a consequent shift of the ventricular septum to the left, thereby decreasing left ventricular filling, has been suggested as a mechanism of pulsus paradoxus. We recently saw a patient with tricuspid atresia and hypoplastic right ventricle who developed pulsus paradoxus. His course may help clarify the contribution of this mechanism.