EFFECTS OF INTRATHECAL MIDAZOLAM WITH HYPERBARIC BUPIVACAINE ON POSTOPERATIVE PAIN RELIEF IN ADULT PATIENTS SCHEDULED FOR MYOMECTOMY

Abstract

Background: Postoperative pain relief can improve functionality, reduce physiological and
emotional morbidity, and enhance quality of life. Subarachnoid block (SAB) with local
anaesthetics and adjuvants has been extensively used for gynaecological surgeries. In order to
maximize the quality of anaesthesia and postoperative analgesia, a number of adjuvants have
been added to spinal local anaesthetics. However none had become established in regular
clinical use because of their adverse effects. Intrathecal midazolam has been shown to have
analgesic property and to potentiate the effects of intrathecal bupivacaine with acceptable side
effects profile. This study compared intrathecal bupivacaine with and without midazolam to
assess its efficacy and analgesic effects on duration of sensory block, pain relief and safety in
patients scheduled for elective myomectomy.
Aim and Objectives: To compare the effects of intrathecal midazolam – hyperbaric
bupivacaine combination with bupivacaine alone, on postoperative pain relief in patients
scheduled for myomectomy.
Methodology: A total of 96 patients scheduled for elective myomectomy with uterine mass of
not more than 22 weeks, American Society of Anesthesiologists (ASA) I or II, aged 18-60years,
were recruited to participate in this prospective, randomized, double-blind comparative study.
After obtaining Hospital Research and Ethics Committee approval and signed informed written
consent form, patients were randomly allocated to two groups of equal number for intrathecal
drug administration. Group 1 (n=48) received 15mg (3ml) of 0.5% hyperbaric bupivacaine
with 0.4ml of normal saline (B group), while group II (n=48) received 15mg (3ml) of 0.5%
bupivacaine with 2mg (0.4ml) preservative-free midazolam (BM group) in the L4-5 or L3-4
interspaces. Standard monitoring of haemodynamic parameters were recorded throughout and
after the procedure. The proportion of patients scoring < 3 on Visual Analogue Scale (VAS) at
the fourth hour after establishment of SAB was used as benchmark for clinically effective
analgesia. The time to first analgesic requirement postoperatively, total analgesic consumption
in 24hours postoperatively, incidence of side effects, and patients’ satisfaction with pain relief
were also evaluated.
Results: The sociodemographic characteristics were similar in both groups. The baseline pulse
rates, systolic and diastolic blood pressures were similar in both groups. The preoperative mean
pulse rate (beats per minute) was 82.66±7.12 in group B while group BM was 80.92±5.52, p
=0.78.The mean systolic blood pressure of group B (mmHg) was 121.00±8.83 versus
124.47±7.98 in group BM, p=0.64. The mean baseline diastolic blood pressure (mmHg) was
77.48±5.33 in group B, 78.28±5.22 in group BM, p=0.75. With regard to intraoperative
haemodynamic variations, (Pulse rates, Systolic blood pressure, and Diastolic blood pressure)
after administration of study drugs, there were no significant statistical differences between the
two groups. P values ranged from 0.19 to 0.95 for pulse rates, 0.10 to 0.91 for systolic blood
pressures, and 0.19 to 0.907 for diastolic blood pressures respectively.
The duration of bupivacaine induced sensory block was 290.0 + 35.1 minutes in group BM as
against 175.0+ 25.1 minutes in group B, p=0.003.The number of pain medications (pethidine
and paracetamol) that were required intraoperatively, was 6 in the BM group as against 12 in
group B, p=0.65. Sensory blockade onset time in B group was 2.29+0.23minutes, versus
2.03+0.12minutes in BM group.( p=0.0002.) Patients, satisfaction with pain relief were rated
as very good by 26 patients in the BM group versus 12 patients in B group, p=0.03. The mean
pentazocine (mg), consumed in 24 hours was 367.90+8.89mg in Bupivacaine group as against
208.0+7.55mg in Bupivacaine-Midazolam group, p=0.001. The mean paracetamol (mg)
consumed in 24 hours was 537.97±113.56mg in group B versus 318.40±78.12mg in group BM,
p=0.001. Injection pentazocine was used for postoperative analgesia. Eight patients in group B
had hypotension while 12 patients in group BM had hypotension. P = 0.082. No report or record
of respiratory depression and pruritus in both groups.
Conclusion: The addition of midazolam to intrathecal bupivacaine improved intraoperative
anaesthesia, prolonged duration of analgesia, and significantly reduced the analgesic
consumptions in the postoperative period.