Cardiovascular and endocrine responses to haemorrhage in the pig

Heart rate (HR), mean arterial pressure (MAP), indices of sympathetic and parasympathetic activity (plasma concentrations of adrenaline, noradrenaline and pancreatic polypeptide, PP), vasopressin (VP) and aldosterone (ALDO) were measured in six pigs during continuous bleeding resulting in hypovolaemic shock, from which five survived. Three stages of haemorrhage could be defined. Stage I. Resting MAP was 85 +/- 6 mmHg and increased to 96 +/- 5 mmHg with a blood loss of 275 (range 250-300) (10 (9-12)% of the estimated blood volume) concomitant with an increase in HR from 105 +/- 5 to 113 +/- 6 beats min-1 (P less than 0.05). Stage II. After a blood loss of 375 (300-500) ml (15 (13-16)%) MAP fell to 62 +/- 9 mmHg and HR to 95 +/- 5 beats min-1 (P less than 0.05). Stage III. A blood loss of 1113 (825-1450) ml (44 (30-52)%) resulted in a MAP of 50 +/- 4 mmHg and an increase in HR to 206 +/- 3 beats min-1 (P less than 0.05). Adrenaline increased from 0.3 +/- 0.1 to 0.8 +/- 0.3 (stage II) and 3.6 +/- 1.1 nmol l-1 (stage III) (P less than 0.05); noradrenaline from 0.4 +/- 0.1 to 1.5 +/- 0.4 (stage II) and 5.9 +/- 1.7 nmol l-1 (stage III) (P less than 0.05); PP from 6.2 +/- 1.6 to 13.3 +/- 2.3 (stage II) and 20.9 +/- 7.8 pmol l-1 (stage III) (P less than 0.05). VP changed only marginally, but ALDO increased from 496 +/- 54 to 623 +/- 76 pmol l-1 (stage III) (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)