Perioperative Management of the Obese Patient

Obesity is a metabolic disease in which adipose tissue comprises a greater proportion of body tissue than normal. It affects up to 33 % of the population in North America 11, 112. Almost 5% weigh more than double their ideal body weight as predicted by age, sex and height. The precursors to obesity are multifactorial and include a genetic tendency, environmental effects, education, sex, race and socio-economical status 83. Most of die major obesity-related health risks increase disproportionately with increasing weight. The rate of premature death is increased in patients 30% overweight and doubles in populations weighing 40-60 % more than ideal body weight 29,47,73. The incidence of sudden unexplained death is at least 13 times greater in morbidly obese women compared with non-obese ones 73. In men participating in the Framingham study, being overweight was found to be associated with a mortality rate of up to 3.9 times greater than the normal-weight group. An increased rate of chronic diseases, many life threatening, has been found in prospective studies of obese patients 46, 118. These include peripheral vascular disease, cardiorespiratory derangements, liver disease, diabetes mellitus, polycythaemia, hyperlipoproteinaemia, diaphragmatic hiatus hernia and malignancies 22,26,42,46,68,73,112,115. Nevertheless,weight reduction immediately before surgery has not been shown to reduce perioperative morbidity or mortality, even though it may reverse some of the pathophysiological changes in the obese patient 5-7, 67, 102, 104. In this review we discuss the pathophysiological changes in the obese patient and their effects in the periods before, during and after operation. The anaesthetist managing an obese patient should be familiar with the special difficulties expected, and plan management accordingly 26, 29.