After injection of the spinal anesthetic drug, women will be allowed to lie down immediately
(0-30 sec) or after three minutes (180 sec) of sitting. The incidence of maternal hypotension
and fetal umbilical cord blood pH will be recorded.
At our centre a conventional dose of 12 mg of hyperbaric bupivacaine in combination with a
short acting opioid fentanyl (to increase block density) and a long acting opioid morphine
(to provide post-operative pain relief ) is used for spinal anesthesia for cesarean
section.However, larger doses of local anesthetic drug when used in caesarean section
commonly cause low blood pressure and requires drugs (vasopressors) to treat it. In our study
the investigators will standardize the doses of both opioids (fentanyl/morphine) and adjust
the dose of local anesthetic (bupivacaine) based on the patients height and weight .One of
the obvious challenges anesthesiologists face is providing adequate anesthesia to the patient
whilst minimizing harmful side effects. Our primary concern is the low blood pressure as an
effect of the spinal anesthetic as it is harmful to both mother and the baby. The
investigators propose that the extent of surgical anesthetic block, which is dependent on
height and weight in our adjusted dose group, will provide adequate anesthesia for surgery
and minimise maternal low blood pressure.
Opioid analgesic drugs are the main treatment of patients during anesthesia. Although highly
effective, their use is not without problems. One is the increasing requirement of these
address the same nociceptive stimulus.
Opioid induced hyperalgesia could be an explanation studies in animal models. Through
mechanisms where N-methyl-D-aspartate receptors, glutamatergic system disturbances and
changes in intracellular calcium regulation involved.
The hyperalgesia induced by intrathecal opioids is controversial. The investigators propose a
model study in patients undergoing cesarean section to study the secondary hyperalgesia
induced based on the study of nociceptive thresholds with two methods opioids: Von Frey
filaments and digital algometer.
If intrathecal fentanyl is used in spinal anesthesia for elective cesarean section, then, an
increase in sensitivity will occur. This increase can be measured by von Frey filaments,
expressed in increased requirement clinically opioids.
We propose to study the effects on hemodynamics (blood pressure, cardiac output, and central
venous pressure) of two doses of bupivacaine for spinal anesthesia during cesarean section: a
higher dose of 12 mg to a lower dose of 4.5 mg. We will examine recovery times, incidence of
hypotension, and compare pain control and maternal satisfaction during and after cesarean
section.
We hypothesize that low dose bupivacaine spinal anesthesia will provide equivalent anesthesia
for cesarean section compared to conventional dose bupivacaine, with less hypotension, faster
recovery time, and enhanced maternal satisfaction. Maternal satisfaction will be assessed by
self-reported pain scores, incidence of nausea and vomiting, shivering, and ability to
interact with baby in the OR.
