Respiratory outcome in extremely premature infants following ketamine anaesthesia.

Premature infants are prone to develop postoperative apnoea. The purpose of the present study was to determine if risk factors could be identified to predict which patients would require postoperative tracheal intubation and lung ventilation. Twenty-five extremely premature infants (birth weight: 811 +/- 242 g (mean +/- SD) and operation weight: 1585 +/- 394 g) needing cryotherapy for retinopathy were studied. After surgery the tracheas were extubated if there was no prolonged apnoea, SaO2 greater than 85%, and heart rate greater than 120 bpm. In eight, tracheal extubation in the operating room was unsuccessful. Using multivariate discriminant analysis, four risk factors correlated with the need for pulmonary ventilation-gestational duration, birth weight, postconceptional age, and preoperative aminophylline treatment for seven days. A scoring system using these factors successfully predicted the need for a tracheal tube after surgery in 92% of patients. It is concluded that the system may be clinically useful in the perioperative care of low-birth-weight infants as it identifies important variables for evaluating postoperative prolonged apnoea.