Bispectral index monitoring during infant cardiac surgery: relationship of BIS to the stress response and plasma fentanyl levels.

BACKGROUND: We evaluated the relationship of the bispectral index (BIS) to commonly used indices of depth of anaesthesia in 19 infants enrolled in a prospective study of the stress response to hypothermic cardiopulmonary bypass. METHODS: Group 1 (n=8) received high-dose fentanyl by bolus technique; group 2 (n=6) received high-dose fentanyl by continuous infusion; and group 3 (n=5) received a fentanyl-midazolam infusion. Blood pressure (BP), heart rate (HR) and plasma epinephrine, norepinephrine, cortisol, ACTH, glucose, lactate and fentanyl were analysed 15 min postinduction, 15 min poststernotomy, 15 min on CPB during cooling and during skin closure. RESULTS: Mean BIS (SD) values for all 19 patients were 45.3 (12.3), 40.4 (14.5), 24.4 (12.4) and 47.9 (13.9), at the successive time points. No significant differences were observed in changes in BIS over time between the groups. A significant correlation was found 15 min postinduction between BIS and BP (systolic r=0.51, mean r=0.56) in all groups, but not between BIS and HR. BIS did not correlate with BP or HR at any other time point. There was no significant correlation between BIS and hormonal, biochemical or plasma fentanyl levels for any group at any time point. CONCLUSIONS: We were unable to demonstrate a relationship between the BIS and haemodynamic, metabolic or hormonal indices of anaesthetic depth. Further evaluation of the BIS algorithm is required in neonates and infants.

Pethidine-associated seizure in a healthy adolescent receiving pethidine for postoperative pain control.

A healthy 17-year-old male received standard intermittent doses of pethidine via a patient-controlled analgesia (PCA) pump for management of postoperative pain control. Twenty-three h postoperatively he developed a brief self-limited seizure. Both plasma pethidine and norpethidine were elevated in the range associated with clinical manifestations of central nervous system excitation. No other risk factors for CNS toxicity were identified. This method allowed frequent self-dosing of pethidine at short time intervals and rapid accumulation of pethidine and norpethidine. The routine use of pethidine via PCA even for a brief postoperative analgesia should be reconsidered.

Chylous ascites following abdominal aortic surgery.

Chylous ascites is an extremely rare complication of abdominal aortic surgery. A case with a successful outcome is presented, followed by a review of the 17 published cases. Chylous ascites can result in nutritional imbalance, immunological deficit and respiratory dysfunction. Paracentesis confirms the diagnosis and provides symptomatic relief. Conservative management, beginning with a low-fat diet and medium-chain triglyceride (MCT) supplementation, is recommended, changing to total parenteral nutrition if unsuccessful. Failure of non-operative treatment may necessitate the need for laparotomy and ligation of leaking lymphatics or peritoneovenous shunting.

Acetazolamide in the treatment of metabolic alkalosis in critically ill patients.

Metabolic alkalosis is a common acid-base disturbance in critically ill patients. In many patients correction of fluid and electrolyte status does not fully correct the metabolic derangement. In this study we examined the effect of 500 mg of intravenous acetazolamide, after correcting for fluid and electrolyte abnormalities, on the acid-base status of 30 ventilated patients. In all patients studied there was a fall of total serum bicarbonate; the mean reduction at 24 hours was 6.4 mmol/L, with a normalization of the base excess and pH. The onset of action was rapid (within 2 hours), and the maximal effect occurred at a mean of 15.5 hours, although there was wide variation. The effect of acetazolamide was still apparent at 48 hours. No adverse effects were noted. We conclude that in patients with metabolic alkalosis, once fluid and electrolyte abnormalities have been corrected, acetazolamide is an effective and safe form of therapy with a quick onset and long duration of action.