Postoperative hypoxaemia and oxygen therapy

A comparison of oxygen therapy devices used in the postoperative recovery period

Seventy-one patients scheduled to undergo upper or lower abdominal surgical procedures were allocated at random to one of seven treatment groups: in the recovery room they were to receive oxygen via a 40% Ventimask with 10 litres/minute oxygen flow, or via either a Hudson mask or a nasal cannula with 3, 6 or 9 litres/minute oxygen flow. The 40% Ventimask gave the most consistent, satisfactory postoperative values of PaO2 but the much cheaper nasal cannula at 6 or 9 litres/minute was generally adequate in conscious patients. The performance of the intermediately priced Hudson mask was similar to that of the nasal cannula at these flows. The unconscious state was associated with a 45% lower PaO2 than the rousable or awake states. Differences between the treatments with regard to postoperative PaCO2 were small and non-significant. The nasal cannula with 6 litres/minute humidified oxygen flow is recommended for routine treatment, and the Ventimask for unconscious patients.

Pulmonary function before and after abdominal surgery in the aged

In patients 70 years or older, pulmonary function tests were performed before and after abdominal surgery to correlate the results with the development of postoperative pulmonary complications which developed in 48% of these patients, compared to 15% in the control group. To predict the development ot PPC, preoperative analysis of the flow-volume curve is useful and 4 (V50-V25)/forced vital capacity is a valuable parameter for the analysis of the flow-volume curve. Postoperatively, pulmonary function was reduced and there was a delay in the restoration of pulmonary function in cases with postoperative pulmonary complications. The administration of appropriate analgesics may be useful to improve postoperative ventilatory disturbances.

Postoperative hypoxaemia and oxygen therapy

To observe the duration of hypoxaemia 8 patients were monitored every day for the first 7 days following upper abdominal surgery. Three of these patients who had failed to regain their preoperative PO2 value by the seventh postoperative day were further monitored on alternate days until the fourteenth postoperative day. A further 3 patients were similarly monitored on alternate days for 14 days. In another group of 10 patients blood gases were monitored every 4 h for the first 48 h following major abdominal surgery, during which time the patients were given 35 per cent oxygen for the first 24 h after operation. (All patients in this group had a diminished respiratory reserve preoperatively to a sufficient degree to warrant admission to the intensive therapy unit postoperatively, and these patients were treated with oxygen for 24 h, as is the practice in our unit and in other surgical units.) Oxygen was administered using a Ventimask at 8 l/min (British Medical Journal, 1972). Nine of the 10 patients did not show postoperative hypoxaemia while being treated with 35 per cent oxygen, although the PO2 value attained were lower than expected. On withdrawal of oxygen after 24 h, the PO2 decreased below preoperative levels in all patients. The PO2 of 7 patients in this group decreased below 8 kPa during the second 24 postoperative hours, in 4 of whom the level fell below 6-7 kPa. Some recommendations to improve the respiratory care of the surgical patient are presented.