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.