Canadian Journal of Anesthesia, Vol 22, 307-315, Copyright © 1975 by Canadian Anesthesiologists' Society

Anaesthesia for Intestinal Short Circuiting in the Morbidly Obese with Reference to the Pathophysiology of Gross Obesity

¹ Department of Anaesthesia, Royal Victoria Hospital & McGill University, Montreal

Sixteen extremely obese patients were anaesthetized for intestinal short circuiting operations. Severe obesity may cause pathological cardio-pulmonary changes. Cardiovascular alterations include increased systemic, pulmonary artery and pulmonary capillary venous pressure. Cardiac output, total blood volume and left ventricular work increase.

Expiratory reserve volume and consequently functional residual capacity decrease with gross obesity. Functional residual capacity falls below closing volume and inspired gas may be distributed to non-dependent lung zones, resulting in decreased ventilation/perfusion ratios and arterial hypoxaemia. Low total respiratory compliance increases the oxygen cost of the work of breathing.

Obesity may change the dose requirements for regional anaesthesia and longacting muscle relaxants. General anaesthesia may also reduce functional residual capacity.

We used a technique of anaesthesia which consisted of epidural analgesia with intra-operative mechanical ventilation and which specifically avoided volatile inhalation agents and long-acting muscle relaxants. All patients were extubated immediately after operation and returned to the recovery room for an average duration of 26 hours. Post-operative treatment included humidified oxygen, chest physiotherapy and elevation of the head of the bed to 45°. Each patient's respiratory progress was monitored by repeated determinations of arterial blood gases and vital capacity and by serial chest X-rays. None of the patients in this group required post-operative tracheal intubation and mechanical ventilation.