Morphine pharmacokinetics in premature and mature newborn infants

The pharmacokinetics of a single dose of morphine was investigated in five term infants (gestational age 37-40 weeks) and eight preterm infants (gestational age 25-32 weeks). In the five term infants, median (range) volume of distribution at steady state (Vd beta) was 1758 (634-2700) ml/kg, plasma clearance (Cl) was 4.73 (1.75-6.61) ml/kg/min and terminal half-life (T1/2) was 224 (107-394) min. In the eight preterm infants, Vd beta was 2366 (1662-2876) ml/kg, Cl was 2.82 (1.88-6.60) ml/kg/min and T1/2 was 556 (248-834) min. No correlation was found between clearance and gestational age, but we found a significant negative correlation between T1/2 and gestational age. We conclude that there is considerable variation in the pharmacokinetic properties of morphine in both term and preterm newborn infants. Because of this variation, careful individual assessment of the clinical effect of therapy with morphine in newborn infants should be exercised.

Prevention of hypotension during spinal anaesthesia for caesarean section

Twenty-six parturients scheduled to receive spinal anaesthesia for caesarean section were randomized to receive either isotonic saline 750 ml plus 20 ml/kg (group A) or 750 ml plus 500 ml (group B) before subarachnoid administration of bupivacaine 13 mg. Ephedrine 0.15 mg/kg i.v. followed by an infusion 0.4 mg.kg(-1) h(-1) were then administered in group B. In both groups ephedrine 10 mg/min i.v. was given if the mean arterial blood pressure decreased more than 10 mmHg. Despite the fluid preload and large doses of ephedrine noted {median (range), group A 30 mg (10-80), group B 92 mg (25-194)}, hypotension, sometimes accompanied by nausea, still occurred. Mean maternal arterial was significantly lower in group A than in group B 5-10 min after induction of spinal anaesthesia (P < 0.05). There was no difference in the frequency of nausea or vomiting, Apgar score, or pH in umbilical cord blood. One neonate in group A and 2 in group B were acidotic. In conclusion, a reduced volume loading could be compensated with an increased ephedrine administration after induction of spinal anaesthesia, without increasing the incidence of hypotension or other maternal or neonatal complications. However, the fluid volumes and/or ephedrine doses used were not sufficient to prevent hypotension altogether.

[Hypertrophic tonsils, upper airway obstruction and cardiac complications. A combined otological, medical and anesthesiological problem]

Hypoventilation in children with hypertrophied tonsils can cause hypoxemia, hypercarbia, acidosis and pulmonary vasoconstriction resulting in cardiac arrhythmias or cor pulmonale. In addition, cerebral symptoms such as day-time hypersomnia or even seizures may be present. Early recognition of hypertrophied tonsils is necessary to avoid development of severe cardiac symptoms. If cardiac incompensation is present, medical treatment is advocated prior to tonsillectomy. Anaesthesia for tonsillectomy in these children is associated with special considerations. Preoperative sedation should be excluded, and inhalational induction with O2 and Halothane is recommended. On induction a difficult intubation should be expected.

Preliminary results of left heart bypass in pigs using a heparin-coated centrifugal pump

To assess the feasibility of left ventricular assist without systemic heparinization, we used a commercially available (Sarns 3M) centrifugal pump with tubing set and cannulas, all internally precoated for the purpose of this study with heparin, to bypass the left ventricle in 12 pigs for periods of either 1 or 3 hours. There was no significant activation of clotting and there was no sign of generalized embolization. However, on postmortem studies, 5 kidneys out of 22 examined showed signs of minimal thromboembolism. This experiment shows that artificial left ventricular assist, free of systemic heparinization but using heparin precoating, is feasible and safe, at least for a short period of time.

Mitral prosthetic replacement in small left atria

A modified transseptal approach for exposure of the difficult mitral valve is described. This allows the surgeon to visualize the valve, especially during prosthetic replacement, in the presence of a small, friable, or noncompliant left atrium.

[The centrifugal pump--a new method of assisting the failing heart following open heart surgery]

The centrifugal pump is a new mechanical ventricular assistant device, which is used to help the failing heart after cardiopulmonary bypass or postoperatively in the ICU. The centrifugal pump is hemodynamically able to improve the coronary and peripheral perfusion in patients in cardiogenic shock. The pump can displace the entire cardiac output and let the blood bypass the left ventricle, which gives the failing heart a possibility for metabolic correction and regeneration. Ten patients were included in the early personal experience at the cardio-thoracic unit in Edinburgh, with a survival rate of 50%, which is regarded as being very satisfactory. All hemodynamic parameters were normalised in the surviving patients.

Excretion of morphine in human breast milk

Five lactating women who underwent surgery and were treated with morphine epidurally or IV/IM in the postoperative phase were included in the study. The morphine concentrations in plasma and breast milk were determined 0, 15, 30, 45, 60, 90, 120, 240, 360 and 480 min after drug administration by means of a specific radioimmunoassay for morphine. The milk-to-plasma ratio was 2.45 +/- 0.8 (mean +/- s.d.). The amount of morphine transferred by nursing is, even at the peak concentration of 500 ng/ml milk, small and will hardly cause respiratory depression or drowsiness in the child.