Atrial natriuretic factor release during hypovolemia and after volume replacement.

Objective: To examine plasma atrial natriuretic factor activity during hypovolemia and after vascular volume replacement.
Design: Prospective, descriptive study.
Settings: Scene of emergency, Emergency Department, and the ICU of a university hospital.
Patients: A total of 47 trauma patients with evidence of hypovolemia were grouped according to their major injury into a thoracic injury group (15 patients; mean Injury Severity Score = 38.5 +/- 3.1 [SEM], Hospital Trauma Index = 14.1 +/- 0.7), an abdominal injury group (14 patients; Injury Severity Score = 36 +/- 3.3, Hospital Trauma Index = 14 +/- 0.9), and a severe head injury group (18 patients; Injury Severity Score = 23 +/- 1.5, Hospital Trauma Index = 10 +/- 0.6).
Measurements and Main Results: Measurements were taken at the scene of emergency; after volume replacement in the Emergency Department; and after 3, 7, 12, 24, 36 hrs and on day 5 in the ICU. In all groups, the average plasma atrial natriuretic factor levels were increased at the scene of emergency and declined significantly to normal values with volume replacement. In the thoracic injury group, plasma atrial natriuretic factor activity decreased from 253 +/- 73 to 115 +/- 83 pg/mL (p less than .0017); in the abdominal injury group, plasma atrial natriuretic factor activity decreased from 194 +/- 42 to 91 +/- 24 pg/mL (p less than .006); in the severe head injury group, plasma atrial natriuretic factor activity decreased from 167 +/- 28 to 70 +/- 13 pg/mL (p less than .02) with volume replacement. Plasma atrial natriuretic factor levels at the scene of emergency were significantly (252 +/- 73 vs. 167 +/- 28 pg/mL; p less than .05) higher in the thoracic injury group and in the abdominal injury group (194 +/- 42 vs. 167 +/- 28 pg/mL; p less than .05), as compared with the severe head injury group.
Conclusions: In trauma patients, plasma atrial natriuretic factor concentrations were markedly increased in patients with untreated hypovolemia and were decreased to normal values with vascular volume replacement. Thus, atrial natriuretic factor seems to play an important physiologic role during hypovolemia.