Martha R. Arden

Resolution of vital sign instability: an objective measure of medical stability in anorexia nervosa

PURPOSE To determine the amount of time necessary for stabilization of blood pressure and heart rate in patients with anorexia nervosa (AN) and the percentage of ideal body weight (IBW) at which this occurs. METHODS A retrospective study was conducted on 36 adolescent patients (33 F, 3 M) with AN, restricting type (Diagnostic and Statistical Manual of Mental Disorders, Fourth edition [DSM-IV] criteria), admitted to a specialized eating disorders unit for nutritional rehabilitation between October 1996 and August 1998. Mean age was 16.5 +/- 2.5 years, range 12-23 years. Each morning, pulse and blood pressure were measured supine and after standing for 2 minutes using an automated blood pressure/pulse measuring device (Dynamap). Orthostasis was defined as a drop in systolic blood pressure > 20 mm Hg with or without a drop in diastolic blood pressure > 10 mm Hg or an increase in heart rate >20 bpm on standing. Time of resolution of orthostasis was defined as the day after which the patient was no longer orthostatic for 48 hours. RESULTS On admission mean pulse rate was 54.4 +/- 14.8 bpm (range 38-78) and mean pulse rate slowly increased to 70 bpm by Day 12 of hospitalization. On admission, 60% of patients had orthostatic pulse changes and with refeeding, this number increased to 85% by Day 4 of admission. The mean number of days until patients were no longer orthostatic was 21.6 +/- 11.1 days and resolution of orthostasis occurred when subjects reached 80.1 +/- 5.7% of IBW. Orthostatic pulse changes were more sensitive indicators of hemodynamic instability than orthostatic blood pressure changes and took longer to resolve. CONCLUSION This study demonstrates that of patients with AN, the majority have orthostatic pulse changes on admission. Normalization of orthostatic pulse changes was achieved after approximately 3 weeks of nutritional rehabilitation when subjects reached 80% of their IBW. Resolution of orthostasis can be used as one of the objective measures to determine medical stability and readiness for discharge to an alternate level of care.

Indirect calorimetry in the nutritional management of eating disorders

The caloric prescription, a key component of the nutritional therapy of anorexia nervosa (AN) and bulimia nervosa (BN), may be empirically prescribed, or based on predicted resting energy expenditure (REE), yet adaptive changes in the metabolic rate may render both methods unreliable. Indirect calorimetry measurement of fasting REE was obtained in 32 patients with AN (n = 21) or BN (n = 11). Predicted REE was calculated according to the Harris-Benedict equation, and empiric caloric prescriptions were made by experienced physicians. In the AN group, mean measured REE was significantly lower than predicted REE (p = .00). The empiric caloric prescription was, as intended, significantly higher than the measured REE, but the two methods correlated significantly (r = .53, p < .05). The predicted REE overestimated caloric needs but was also highly correlated with measured REE (r = .69, p < .001). By regression analysis, measured REE could be calculated from predicted REE as follows: measured REE (Kcal/day) = (1.84 x Harris-Benedict predicted REE) - 1,435. In the BN group, mean measured REE was not significantly different from the empiric caloric prescription (p = .09) but was significantly lower than the Harris-Benedict predicted REE (p = .022). Neither correlated with measured REE in BN. Therefore, in BN indirect calorimetry is the only reliable method for determining caloric needs. In AN indirect calorimetry remains the preferred method, but when not available, we recommend the above equation to determine resting energy requirements.