Effects of acute haemorrhagic hypotension during pregnancy and lactation in conscious goats.

Effects of acute, short-lasting haemorrhage have been studied in six goats. The experiments were made 55 +/- 3 days (mid-pregnancy = MP), and 24 +/- 2 days (late pregnancy = LP) before parturition, in lactation weeks 3-8, and in the non-pregnant, non-lactating (= control) period. The room temperature was kept at 20 +/- 1 degrees C, except during one experimental series in lactating goats, which was performed at +30 degrees C. Approximately the same volume of blood had been removed in all periods, when the mean arterial blood pressure (MAP) fell. At this moment bleeding was stopped. The volume loss, calculated as per cent of total blood volume, was significantly smaller during pregnancy and lactation than in the control period. The fastest heart rate, both at rest and during haemorrhage, was observed in LP goats. The respiratory frequency of the LP goats increased markedly in response to haemorrhage, but the most rapid respiratory rate was observed in lactating goats bled at the room temperature +30 degrees C. The increase in plasma vasopressin (AVP) concentration coincided with the fall in MAP. The AVP rise seen during late pregnancy was significantly higher than in all the other periods. The plasma noradrenaline (NA) concentration increased by about five times in LP goats, but did not change significantly in the other periods. Plasma renin activity did not rise, with the exception of a small increase in lactating goats bled at +30 degrees C. The plasma aldosterone concentration rose, but there was no difference between periods.(ABSTRACT TRUNCATED AT 250 WORDS)