Labetalo1 infusion is becoming more commonly used in controlling the
blood pressure during anaesthesia in different situation. This work was
designed to study the controlled hypotensive effect of labetalol infusion.
with any possible effect on the skeletal muscle. It was found that labetalot
infusion (100 tig /kglminute) produced a gradual reduction of the systolic
blood pressure from110 + 8 to 70 + 6 mm Hg and the diastolic blood
pressure from 100 + 8 to 60 + 6 mm Hg. This hypotensive effect was mentamed
during the infusion of labetalol. After stoppage of infusion the
blood pressure and the H. R returned within 20 min. to their normal levels.
Also, it was observed that labetalol infusion attenuated the vasopressor
effects of phenylepherine (1 ug / kg), adrenaline (1 ug /kg) and abolished
completely the hypotensive effect of isoprenaline (0.5 ug/ kg).
Moreover, during labetalol infusion, there was 20 % reduction in the contraction
of gasterocnemius of cats. This reduction was not reversed by
stoppage of infusion but it was reversed by L V. infusion of neostigmine
(100 ug /kg). In addition, it was observed that the relaxant effect of DTC.
was potentiated during labetalol infusion and this effect was reversed
only by neostigmine (100 ug / kg). The in-vitro results revealed that labetalol
in concentrations of 0.2, 0.4, 0.8, and 3.2 ug / rrareduced the indirect
and direct contractions of rat phrenic nerve diaphragmpAch and kcl induced
contractions of isolated rectus abdominis muscle of toad in dose
dependent manner Accordingly the skeletal muscle relaxant effect of labetalol
should be investigated clinically and put it in consideration during
its use for controlling blood pressure. |
