Nutritional status of patients requiring cardiac surgery

Abstract

Nutritional studies were carried out on 47 randomly selected patients undergoing valve replacement. The total-body potassium was measured noninvasively, by use of a whole-body monitor with an accuracy of ±4 percent. This was used as an absolute index of nutritional status of the nonacidotic patient. The metabolic response to operation, as calculated from changes in total-body potassium, was a median loss of 11.1 Gm. or a mean loss of 9.8 Gm. of nitrogen per day over 7 postoperative days, compared with a mean loss of 6.8 Gm. of nitrogen per day in the same patients as calculated by conventional nitrogen balance methods. Total-body water measured before operation was not significantly different from the predicted level (p > 0.05), and there was no difference between preoperative total-body water and that measured on the seventh postoperative day (p > 0.07). Twenty-three of the patients exhibited preoperative nutritional depletion (range, 5 to 30 percent) as assessed by loss of body cell mass from total-body potassium measurements. The well-nourished patients had a median postoperative hospital stay of 17 days (range, 11 to 25) compared with 27 days (range, 12 to 60) for those who had been nutritionally depleted (p < 0.01). None of the 21 normally nourished patients died. Nine of the 26 nutritionally depleted patients died and this difference is significant (Fisher’s exact p = 0.009). In patients with a normal packed cell volume, who are clinically free of edema, there is a highly significant correlation between body cell mass measured by total-body potassium and fat-free mass measured by skinfold calipers (p < 0.01). This allows a better bedside measurement of the degree of preoperative nutritional depletion than derived from unreliable clinical impressions.