Date Published: May 15, 2013
Publisher: Hindawi Publishing Corporation
Author(s): Anirban Chattopadhyay, Souvik Maitra, Suvadeep Sen, Sulagna Bhattacharjee, Amitava Layek, Sugata Pal, Kakali Ghosh.
Spinal anaesthesia, which is one of the techniques for infraumbilical surgeries, is most commonly criticized for limited duration of postoperative analgesia. Several adjuvants have been tried along with local anesthetic for prolonging the duration of analgesia. In this study, we have observed the effect of midazolam as an adjuvant in patients undergoing infraumbilical surgery. In this prospective, randomized, double blinded, and parallel group and open label study of 90 adult patients aged 18–60 years, of American Society of Anaesthesiologists (ASA) status I and II, scheduled for elective infraumbilical surgery, were randomly allocated in two groups. Each patient in group “B” received hyperbaric bupivacaine 12.5 mg along with 0.4 mL of normal saline in the subarachnoid block, and patients of group “BM” received 12.5 mg hyperbaric bupivacaine along with preservative free midazolam 0.4 mL (2 mg). We found that use of midazolam as adjuvant with the local anesthetic in spinal anaesthesia significantly increases the duration of analgesia (median 320 min versus 220 min) and motor block (median 255 min versus 195 min) but decreases the incidence of postoperative nausea-vomiting (PONV).
Spinal subarachnoid block is one of the most versatile regional anesthesia techniques available today. Regional anesthesia offers several advantages over general anesthesia—blunts stress response to surgery, decreases intraoperative blood loss, lowers the incidence of postoperative thromboembolic events, and provides analgesia in early postoperative period. Subarachnoid block provides adequate anesthesia for patients undergoing infraumbilical surgery.
In this study, intrathecal analgesia with 0.5% hyperbaric bupivacaine 2.5 mL with 0.4 mL 0.9% normal saline has been compared with 0.5% hyperbaric bupivacaine 2.5 mL plus 0.4 mL (2 mg) preservative free midazolam in a predetermined dose, and two groups will be compared in terms of duration of effective analgesia by time interval between the onset of intrathecal block to time for request for first rescue analgesia and by VAS pain score. Perioperative sedation, hemodynamic changes, peak height of block, time for regression of motor block to sacral dermatome, and any obvious side effect were also assessed.
To compare duration of effective analgesia between the two groups.To assess the perioperative hemodynamic changes.To observe perioperative sedation and any obvious adverse effects.
After obtaining institutional ethics committee clearance and written informed consent from the patients, 90 adult patients of ASA physical status I and II and aged 18–60 years undergoing elective infraumbilical (gynecologic/urologic) under spinal subarachnoid block anesthesia were included into the study. Patients refusing to participate, with known allergic to local anaesthetic and midazolam, suffering from chronic pain, and pregnant women were excluded from the study. Patients having the level of sensory block below T10 after 15 minutes of subarachnoid block or having VAS pain score greater than 40 at any point of time during intraoperative period were offered general anesthesia for the rest of the procedure. This subset of patients were planned to regard as “incomplete block” category and planned to exclude from the final data analysis.
The patients in both groups were comparable in terms of demographic profile, that is, age, height, weight, sex, ASA PS distribution, duration of surgery, and types of surgeries (Table 1).
The baseline characteristics in either group were similar from statistical standpoint. Considering the intraoperative hemodynamic variables the result of our study is comparable with studies done by Batra et al. , Kim and Lee , Agrawal et al. , and Gupta et al.  who also did not find statistically significant difference in heart rate, arterial blood pressure in their studies. Incidence of hypotension and bradycardia is found to be similar in both groups.
We conclude that the addition of 2 mg preservative free midazolam to 0.5% hyperbaric bupivacaine for subarachnoid block in infraumbilical surgery prolongs the duration of effective analgesia as compared to bupivacaine alone and delays the need for postoperative rescue analgesics without having any sedative effect, pruritus, or respiratory depression. The use of intrathecal midazolam also decreases the incidence of postoperative nausea-vomiting (PONV). Intrathecal midazolam in a dose of 2 mg does not have any clinically significant effect on perioperative hemodynamics.