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Neither propofol nor isoflurane anesthesia alter sinoatrial or atrioventricular node function in pediatric patients undergoing radiofrequency catheter ablation, compared to values obtained during baseline anesthesia with alfentanil and midazolam.

In order to define the changes in intracranial pressure which occur during tracheal intubation in young infants, a Ladd transducer was used to monitor anterior fontanelle pressure (AFP) non-invasively in awake (group 1, n = 14) and anaesthetized (group 2, n = 10) infants during intubation of the trachea. Heart rate and systolic arterial pressure were also recorded. In quiet, undisturbed infants, AFP (mean +/- SEM) was similar in groups 1 (9.6 +/- 0.5 mm Hg) and 2 (8.7 +/- 0.8 mm Hg); with crying, AFP increased significantly in both groups. During laryngoscopy in group 1, AFP increased to 33.5 +/- 3.6 mm Hg, which was significantly greater than in the quiet infant, but did not differ significantly from measurements in the crying infant. In group 2, AFP increased significantly to 15.8 +/- 18 mm Hg during laryngoscopy. This increase was significantly less than the group 1 response. Neither heart rate nor systolic arterial pressure changed significantly in either group during laryngoscopy--when compared with measurements in the quiet state. It was concluded that AFP increases significantly during intubation and during crying in the infant. The response to intubation is only partially attenuated by the prior administration of general anaesthesia.

SummaryHeparin therapy for children undergoing cardiopulmonary bypass (CPB) is monitored in the operating room by automated whole blood activated clotting times (ACT). For many years our institution used Hemochron (HC) ACT machines but changed to HemoTec (HT) ACT machines because they required a smaller blood sample and provided results in duplicate. When HemoTec ACT machines were introduced at our institution, the surgical team was concerned that increased amounts of heparin were being administered to our patients during CPB. This study was conducted to investigate the potential mechanisms responsible for these clinical observations. First, we compared ACT values on ex vivo blood samples from 20 consecutive pediatric patients (6 samples each) during CPB. The HC ACT values were significantly and systematically increased over HT ACT values (HC: 750 ± 40 vs HT: 418 ± 26, Mean ± SEM, p <0.01). 94% of all HC ACT values were above 450 s compared to only 27% of HT ACT values. If HT ACT values had been used for patient monitoring, all patients would have received more heparin to achieve ACT values above 450 s. The two machines reported similar ACT values when heparin was added in vitro to whole blood (0.1-5.0 units/ml), (HC: Y = 98X + 104, r2 = 0.93 HT: Y = 82X + 109, r2 = 0.94). Heparin concentrations in our patients following a bolus of 300 U/kg of heparin, but prior to CPB were 3.2 ± 0.07 units/ml. Following the initiation of CPB, heparin concentrations decreased to 1.3 ± 0.05, reflecting, in part, hemodilution by the pump prime (1 U of heparin/ml). In contrast to the in vitro results, there was no relationship between ACT values measured by either machine and plasma heparin concentrations in ex vivo samples. Finally, plasma concentrations of 8 coagulation proteins measured prior to CPB and following CPB were decreased by 27-55%, predominantly reflecting the final dilution by CPB. In conclusion: 1) HT and HC machines cannot be used interchangeably in pediatric patients without risk of altering clinical practice in an uncontrolled fashion; and 2) ACT values from children on CPB correlate poorly with heparin concentrations, likely due to hemodilution. Optimal use of anticoagulant therapy during CPB in children requires further study in clinical trials and ongoing quality control.