Ketamine, catecholamines, and uterine tone in pregnant ewes.

Blood levels of ketamine, measured in both mother (1,230 ng/ml at 1 minute) and fetus (470 ng/ml at 1 minute) illustrate not only rapidly decreasing levels of the drug after its intravenous administration but also its transplacental passage. Concentrations of norepinephrine, epinephrine, and dopamine did not change in the mother or fetus after ketamine, with the exception of maternal levels of epinephrine, which were significantly higher at 45 minutes than control values (p less than 0.05). Maternal effects of ketamine consisted of increases in mean arterial pressure (7% p less than 0.05), cardiac output (16% p less than 0.01), and respiratory acidosis, all of which were slight and transitory. Although resting uterine tone increased (39% p less than 0.01), the uterine blood flow remained constant. None of the physiologic alterations could be correlated with changes in catecholamine levels. Therefore, the cardiovascular and uterine stimulating properties of ketamine at a dose of 0.7 mg/kg are small and are not the result of increased catecholamine levels in plasma. Further studies are necessary to elucidate the mechanism.

A comparison of T4 and T7 dermatomal levels of analgesia for caesarean section using the lumbar epidural technique.

We compared analgesia to the T4 dermatomal level with analgesia to the T7 level with and without prophylactic intramuscular administration of ephedrine 25 mg to determine the adequacy and side effects of such analgesia for caesarean section. Unmedicated patients were prehydrated (727 +/- 303 ml of saline solution) and kept in a left lateral tilt position. Sufficient three per cent chloroprocaine was given to obtain analgesia to the T7 (T6-T8) dermatomal level (455 +/- 128 mg) or to the T4 (T3-T5) dermatomal level (758 +/- 168 mg). Patients who received analgesia to the higher level required less narcotic than those who received analgesia to the lower level (21 per cent versus 48 per cent) (p less than 0.05). The incidence of hypotension in patients with analgesia at the T4 level was 21 per cent for those receiving ephedrine and 64 per cent for those who did not receive ephedrine (p less than 0.05). Intramuscular administration of ephedrine 25 mg was not associated with increased plasma levels of norepinephrine, epinephrine or dopamine. There was no difference in Apgar score, behavioural test scores, neonatal acid-base status or oxygenation in children of mothers in the different groups. We conclude that a T4 dermatomal level of analgesia combined with intramuscular administration of ephedrine 25 mg, provides more maternal comfort than a T7 level of analgesia does, with or without ephedrine, and is without significant maternal or foetal side effects.