EFFECT OF ACUTE HYPERCAPNIA ON ALPHA-ATRIAL-NATRIURETIC-PEPTIDE, RENIN, ANGIOTENSIN-II, ALDOSTERONE, AND VASOPRESSIN PLASMA-LEVELS IN PATIENTS WITH COPD

Disturbances in hormonal systems involved in sodium and water homeosta sis are common during respiratory insufficiency. To investigate the ro le of hypercapnia, we designed a study to examine the hormonal respons e to acute hypercapnia induced at constant cardiac filling pressures a nd without hypoxemia. Seven sedated patients with COPD receiving mecha nical ventilation were studied during five successive periods. Hemodyn amics, arterial blood gases, and plasma hormone levels (atrial natriur etic peptide, renin, angiotensin II, aldosterone, vasopressin) were me asured three times during 60 min of acute hypercapnia (52 +/- 5 mm Hg) and at control periods, before (36 +/- 4 mm Hg) and after (42 +/- 3 m m Hg) acute hypercapnia. During acute hypercapnia, mean pulmonary arte rial pressure and cardiac output were increased without variation of o ther measured cardiorespiratory data and hormonal levels when compared with control values. After acute hypercapnia, cardiorespiratory varia bles returned to control values without variations of hormonal levels. Our results show that moderate acute hypercapnia does not significant ly influence the hormonal levels when cardiac filling pressures and sy mpathetic tone remain stable. We suggest that changes in those plasma hormones involved in salt and water homeostasis during acute hypercapn ia are secondary to hemodynamic changes induced by acute respiratory f ailure and not to acute hypercapnia per se.