Spinal anaesthesia remains an established technique for lower abdominal and infraumbilical operations because it provides a reliable sensory and motor block through a relatively straightforward neuraxial procedure. [1] Bupivacaine is commonly selected for subarachnoid block because of its duration of action. Nevertheless, postoperative pain may require additional management as the block regresses. [2] Several agents have been investigated as intrathecal adjuvants to improve the quality or duration of spinal anaesthesia and postoperative pain relief. These include opioids and alpha-2 adrenergic agonists. [3] Clinical studies have evaluated intrathecal midazolam with bupivacaine in infraumbilical and lower abdominal procedures. [4] Other comparative studies have examined midazolam against clonidine or dexmedetomidine as an adjunct to intrathecal bupivacaine. [5] A randomised comparison has also evaluated dexmedetomidine and midazolam in this setting. [6] Midazolam is a benzodiazepine that enhances gamma-aminobutyric acid-mediated inhibitory neurotransmission. Its potential neuraxial antinociceptive action has been investigated in experimental and clinical studies. [4] The clinical rationale for evaluating intrathecal midazolam as an adjunct to bupivacaine has been explored in randomised comparative studies. [5] The present study compared intrathecal 0.5% hyperbaric bupivacaine alone with the same regimen combined with 2 mg midazolam in patients undergoing lower abdominal surgery. Postoperative analgesia was evaluated alongside sensory and motor block characteristics, physiological stability and recorded adverse effects.

Study design and setting: This prospective, randomised comparative study was conducted in the Department of Anaesthesiology at Malla Reddy Institute of Medical Sciences and Hospital, Hyderabad, following institutional ethics committee approval. The dissertation described an 18-month study period during 2023–2025. Participants: Sixty patients aged 20–60 years who were scheduled for lower abdominal surgery and classified as ASA physical status I or II were enrolled after written informed consent. Exclusion criteria were absence of valid consent, ASA physical status III or higher, allergy to local anaesthetics, significant coagulopathy, local infection at the proposed block site and difficult airway. Group allocation and study medication: Participants were allocated by lottery method into two equal groups (n=30 each). Group A received 3.5 mL of 0.5% hyperbaric bupivacaine intrathecally. Group B received 3.5 mL of 0.5% hyperbaric bupivacaine with 2 mg preservative-free midazolam. Perioperative management: Patients underwent pre-anaesthetic evaluation and routine investigations. The dissertation recorded oral alprazolam 0.5 mg and pantoprazole 40 mg as premedication on the night before surgery. In the operating room, intravenous access was secured and baseline heart rate and mean arterial pressure were recorded. With the patient seated and under aseptic precautions, a midline lumbar puncture was performed using a 25-gauge spinal needle. After free flow of cerebrospinal fluid was confirmed, the allocated intrathecal solution was administered. Outcome assessment: Outcomes included time taken to reach T6, time to attain maximum sensory level, motor block assessed using the modified Bromage scale, postoperative pain scores at 15 minutes, 30 minutes and one hour, time to first analgesia, duration of analgesia, duration of sensory and motor blockade, postoperative analgesic requirement, and adverse events. Heart rate, systolic and diastolic blood pressure, mean arterial pressure, respiratory rate and oxygen saturation were recorded at baseline and specified intervals after spinal injection. Statistical analysis: Continuous variables were expressed as mean and standard deviation, and categorical variables as number and percentage. The dissertation reported use of the unpaired Student’s t-test for continuous variables and the chi-square test for categorical variables; the Mann–Whitney U test was reported for pain scores. A p-value below 0.05 was considered statistically significant.

Table 1. Baseline characteristics Characteristic Group A (n=30) Group B (n=30) p-value Age, years 39.00 ± 8.18 40.40 ± 8.33 0.514 Female, n (%) 10 (33.3) 12 (40.0) 0.395 Male, n (%) 20 (66.7) 18 (60.0) ASA I, n (%) 19 (63.3) 19 (63.3) 0.605 ASA II, n (%) 11 (36.7) 11 (36.7) Weight, kg 75.03 ± 7.53 76.34 ± 9.04 0.544 Height, cm 168.20 ± 6.62 169.23 ± 5.50 0.513 BMI, kg/m² 26.58 ± 2.91 26.72 ± 3.46 0.868 Block at L3–L4, n (%) 23 (76.7) 20 (66.7) 0.284 Block at L4–L5, n (%) 7 (23.3) 10 (33.3) Values were mean ± SD or n (%). Sixty patients were studied, with 30 participants in each group. Mean age was 39.00 ± 8.18 years in Group A and 40.40 ± 8.33 years in Group B (p=0.514). Sex distribution, ASA physical status, weight, height, body mass index and level of spinal puncture were also comparable between groups. (Table 1). Table 2. Sensory and motor block characteristics Outcome Group A Group B p-value Time to reach T6, min 10.27 ± 2.10 12.93 ± 2.26 0.001 Time to maximum sensory level, min 1.47 ± 0.51 1.57 ± 0.50 0.447 Bromage score at 5 min 1.37 ± 0.76 1.50 ± 0.68 0.479 Bromage score at 10 min 2.60 ± 0.50 2.37 ± 0.49 0.073 Bromage score at 15 min 3.00 ± 0.00 2.90 ± 0.31 0.078 Bromage score at 20 min 3.00 3.00 Not applicable Values were mean ± SD. Maximum sensory level was T6 in both groups. Time taken to reach T6 was shorter in Group A than Group B (10.27 ± 2.10 versus 12.93 ± 2.26 minutes; p=0.001). Time to attain maximum sensory level was similar (1.47 ± 0.51 versus 1.57 ± 0.50 minutes; p=0.447). All participants attained a maximum sensory level of T6. Motor block scores at 5, 10 and 15 minutes did not differ significantly, and both groups reached a modified Bromage score of 3 by 20 minutes. (Table 2). Table 3. Summary of physiological measurements Parameter Measurement times Between-group result Heart rate Baseline, 1, 3, 5 and 10 min All p>0.05 Systolic blood pressure Baseline, 1, 3, 5 and 10 min All p>0.05 Diastolic blood pressure Baseline, 1, 3, 5 and 10 min All p>0.05 Mean arterial pressure Baseline, 1, 3, 5 and 10 min All p>0.05 Respiratory rate Baseline, 1, 3, 5 and 10 min All p>0.05 Oxygen saturation Baseline, 1, 3, 5 and 10 min All p>0.05 Heart rate, systolic and diastolic blood pressure, mean arterial pressure, respiratory rate and oxygen saturation were comparable between groups at baseline and at the recorded intervals. No measured time point showed a statistically significant between-group difference. (Table 3). Table 4. Postoperative pain and analgesia-related outcomes Outcome Group A (n=30) Group B (n=30) p-value Pain score at 15 min 4.63 ± 1.28 1.46 ± 1.11 0.001 Pain score at 30 min 4.56 ± 0.85 2.86 ± 1.77 0.001 Pain score at 1 hour 4.63 ± 1.09 4.10 ± 1.06 0.061 Time to first analgesia, min 192.94 ± 1.95 182.46 ± 2.96 0.000 (reported) Duration of analgesia, min 177.80 ± 33.62 364.27 ± 56.87 0.001 Sensory blockade duration, min 132.57 ± 12.86 196.53 ± 13.79 0.001 Motor blockade duration, min 169.90 ± 19.51 215.00 ± 18.89 0.001 Values were mean ± SD. Postoperative pain scores were lower in Group B at 15 minutes (1.46 ± 1.11 versus 4.63 ± 1.28; p=0.001) and 30 minutes (2.86 ± 1.77 versus 4.56 ± 0.85; p=0.001). At one hour, the difference was not statistically significant (4.10 ± 1.06 versus 4.63 ± 1.09; p=0.061). Time to first analgesia was reported as 192.94 ± 1.95 minutes in Group A and 182.46 ± 2.96 minutes in Group B (reported p=0.000). This endpoint was kept distinct from the separately tabulated duration of analgesia. (Table 4). Mean duration of analgesia was 177.80 ± 33.62 minutes in Group A and 364.27 ± 56.87 minutes in Group B (p=0.001). Sensory blockade lasted 132.57 ± 12.86 minutes in Group A and 196.53 ± 13.79 minutes in Group B; motor blockade lasted 169.90 ± 19.51 and 215.00 ± 18.89 minutes, respectively (p=0.001 for both). (Table 4). Table 5. Postoperative analgesic requirement Analgesic Group A (n=30) Group B (n=30) p-value IV paracetamol 1 g, n (%) 29 (96.7) 1 (3.3) 0.001 Tramadol in 24 hours, n (%) 1 (3.3) 29 (96.7) Postoperative analgesic distribution differed between groups. In Group A, 29 patients (96.7%) received intravenous paracetamol 1 g and one patient (3.3%) received tramadol. In Group B, one patient (3.3%) received paracetamol and 29 (96.7%) received tramadol (p=0.001). (Table 5).

In the present study, baseline demographic characteristics were comparable between Group A and Group B. The mean age was 39.00 ± 8.18 years in Group A and 40.40 ± 8.33 years in Group B (p=0.514). The gender distribution, ASA physical status, weight, height, body mass index and level of spinal puncture also showed no statistically significant differences. This comparability is important when evaluating the differences in block characteristics and postoperative analgesia observed between the two groups. Similar demographic findings were reported by Joshi et al., who compared intrathecal midazolam with clonidine in patients undergoing lower abdominal surgery and found no significant differences in baseline characteristics. [5] Chattopadhyay et al., in their study of 90 patients undergoing infraumbilical surgery, also reported comparable demographic characteristics between the bupivacaine-alone and bupivacaine–midazolam groups. [4] Hasan, in a study involving 60 patients undergoing lower abdominal surgery, likewise reported comparable baseline characteristics between the two groups. [7] Time to Reach T6 Level In the present study, the mean time required to reach the T6 sensory level was 10.27 ± 2.10 minutes in Group A and 12.93 ± 2.26 minutes in Group B. The difference was statistically significant (p=0.001), with Group A achieving the required sensory level earlier than Group B. This indicates that the addition of midazolam was associated with a longer time to reach T6 in the present study. A similar trend towards delayed sensory block development with the addition of midazolam was described by Choudhary et al. (2018), who compared intrathecal dexmedetomidine and midazolam with bupivacaine in lower abdominal surgeries. [8] However, the findings should be interpreted in relation to the specific sensory endpoint assessed, as time to reach a predetermined dermatome and time to attain the maximum sensory level are different measurements. In the present study, despite the difference in time to reach T6, all patients in both groups attained the same maximum sensory level. Sensory Onset Time In the present study, the mean time to attain the maximum sensory level was 1.47 ± 0.51 minutes in Group A and 1.57 ± 0.50 minutes in Group B. The difference was not statistically significant (p=0.447), indicating that the addition of intrathecal midazolam did not significantly alter this recorded sensory onset parameter. This finding is comparable with the observations of Agrawal et al., who reported sensory onset times of approximately 186 seconds and 180 seconds in their respective study groups. [9] Gupta et al. also reported similar onset times of approximately 180 and 174 seconds in patients receiving bupivacaine with and without intrathecal midazolam. [10] Hasan reported mean onset times of 190.50 ± 21.30 seconds in the control group and 185.33 ± 26.81 seconds in the midazolam group, without a statistically significant difference. [7] These findings indicate that the addition of intrathecal midazolam does not necessarily alter the initial development of sensory blockade, although the duration of the block may be prolonged. Motor Blockade In the present study, the modified Bromage scores at 5, 10 and 15 minutes were comparable between the two groups. The mean scores at 5 minutes were 1.37 ± 0.76 in Group A and 1.50 ± 0.68 in Group B (p=0.479). At 10 minutes, the scores were 2.60 ± 0.50 and 2.37 ± 0.49, respectively (p=0.073), while at 15 minutes they were 3.00 ± 0.00 and 2.90 ± 0.31 (p=0.078). Both groups attained a score of 3 by 20 minutes. Thus, the addition of midazolam did not produce a statistically significant difference in the early progression of motor blockade. Kapdi and Desai also evaluated intrathecal preservative-free midazolam as an adjuvant to bupivacaine and reported that the addition of midazolam prolonged postoperative analgesia without a significant alteration in the initial block characteristics. [11] Similar observations regarding the motor block characteristics of intrathecal midazolam have been reported by Lee et al. [12] In the present study, however, the duration of motor blockade was significantly longer in Group B, indicating that the effect of midazolam was more evident in the duration of blockade than in its initial development. Pain Score In the present study, postoperative pain scores were significantly lower in Group B at 15 and 30 minutes. At 15 minutes, the mean pain score was 4.63 ± 1.28 in Group A compared with 1.46 ± 1.11 in Group B (p=0.001). At 30 minutes, the corresponding scores were 4.56 ± 0.85 and 2.86 ± 1.77 (p=0.001). At one hour, the difference between the groups was not statistically significant (p=0.061). These findings indicate better pain control in the midazolam group during the early postoperative period. Chattopadhyay et al. reported lower postoperative pain scores and a prolonged duration of analgesia in patients who received intrathecal midazolam with bupivacaine compared with those who received bupivacaine alone. [4] Joshi et al. also reported significantly lower verbal rating pain scores in the midazolam group compared with the clonidine group. [5] The findings of the present study were in agreement with these observations, particularly with regard to the reduction in early postoperative pain scores. Time to First Analgesia In the present study, the mean time to first analgesia was 192.94 ± 1.95 minutes in Group A and 182.46 ± 2.96 minutes in Group B. The difference was reported as statistically significant (p=0.000), with a longer interval in the bupivacaine-alone group. This finding differs from the separately recorded duration-of-analgesia result, which was significantly longer in Group B. Samantaray et al. compared intrathecal dexmedetomidine, midazolam and saline as adjuvants to hyperbaric bupivacaine. They reported a mean duration of effective analgesia of 236.9 ± 64.9 minutes in the midazolam group and 212.7 ± 70.2 minutes in the control group, although the difference between midazolam and control was not statistically significant. [6] Joshi et al. reported a longer duration of postoperative analgesia in the midazolam group than in the clonidine group (391.64 ± 132.98 versus 296.60 ± 52.77 minutes). [5] Duration of Analgesia In the present study, the mean duration of analgesia was 177.80 ± 33.62 minutes in Group A and 364.27 ± 56.87 minutes in Group B. The difference was statistically significant (p=0.001), demonstrating a considerably longer reported duration of analgesia following the addition of intrathecal midazolam. Chattopadhyay et al. reported a median duration of analgesia of 220 minutes in the bupivacaine-alone group and 320 minutes in the bupivacaine–midazolam group. [4] Hasan reported a mean duration of analgesia of 195.56 ± 36.29 minutes in the control group and 318.93 ± 38.24 minutes in the midazolam group. [7] Bhattacharya et al. also reported prolonged analgesia following the addition of intrathecal midazolam to bupivacaine, with mean durations of approximately 210 and 300 minutes in the respective groups. [13] Prakash et al., while evaluating two doses of intrathecal midazolam with bupivacaine in patients undergoing caesarean delivery, reported longer analgesia durations in the midazolam groups, with values of approximately 228 and 366 minutes. [14] Bharti et al. also reported improved duration and quality of spinal anaesthesia and prolonged perioperative analgesia following the addition of intrathecal midazolam. [15] The findings of these studies were comparable with the present study and support the prolongation of postoperative analgesia when midazolam is added to intrathecal bupivacaine. However, Samantaray et al. did not demonstrate a statistically significant prolongation of effective analgesia with 1 mg intrathecal midazolam compared with the control group. [6] The difference in dose and study protocol may contribute to the variation in findings. Choudhary et al. also reported a longer duration of effective analgesia with dexmedetomidine than with midazolam, although the midazolam group demonstrated a longer duration than the control group. [8] Duration of Sensory Blockade In the present study, the mean duration of sensory blockade was 132.57 ± 12.86 minutes in Group A and 196.53 ± 13.79 minutes in Group B. The difference was statistically significant (p=0.001), demonstrating a prolonged sensory block following the addition of midazolam. Hasan reported a similar finding, with mean sensory blockade durations of 130.40 ± 36.36 minutes in the control group and 191.90 ± 36.40 minutes in the midazolam group. [7] Lee et al. reported sensory block durations of approximately 139 and 206.70 minutes in the control and midazolam groups, respectively. [12] Yun et al. also reported prolonged sensory blockade with intrathecal midazolam, with mean durations of approximately 117 and 169.20 minutes. [16] Prakash et al. reported corresponding sensory block durations of approximately 126 and 182 minutes. [14] These observations align with the present findings and indicate that adding intrathecal midazolam prolongs the duration of sensory blockade when used with bupivacaine. Duration of Motor Blockade In the present study, the mean duration of motor blockade was 169.90 ± 19.51 minutes in Group A and 215.00 ± 18.89 minutes in Group B. The difference was statistically significant (p=0.001), indicating a longer duration of motor blockade in patients receiving intrathecal midazolam. Hasan reported a mean motor blockade duration of 176.30 ± 23.70 minutes in the control group and 208.10 ± 18.21 minutes in the midazolam group. [7] These values closely match to those observed in the present study. Lee et al. reported motor block durations of approximately 118.30 and 179.70 minutes in the respective groups. [12] Bharti et al. also observed prolonged motor blockade following the addition of intrathecal midazolam, reporting values of approximately 180 and 225 minutes. [15] The findings of these studies were in agreement with the present study and demonstrate that intrathecal midazolam prolongs motor blockade in addition to sensory blockade. Although this may contribute to a longer period of anaesthesia, the prolonged motor block should also be considered when planning postoperative mobilisation. Postoperative Analgesic Requirement In the present study, a statistically significant difference was observed in the type of postoperative analgesic administered. In Group A, 29 patients (96.7%) received intravenous paracetamol 1 g, while one patient (3.3%) received tramadol. In Group B, 29 patients (96.7%) received tramadol, while one patient (3.3%) received paracetamol (p=0.001). Shiva Kumar and Ravi Kumar reported a lower requirement for rescue analgesia in patients receiving intrathecal midazolam, with a mean of 1.20 ± 0.61 doses in the midazolam group compared with 3.03 ± 0.18 doses in the bupivacaine-alone group. [17] Chattopadhyay et al. also reported prolonged analgesia and a delayed requirement for rescue medication following the addition of midazolam. [4] Kim and Lee similarly reported an increased analgesic effect of spinal blockade with intrathecal midazolam in patients undergoing haemorrhoidectomy. [18] Haemodynamic and Respiratory Parameters In the present study, heart rate, systolic blood pressure, diastolic blood pressure, mean arterial pressure, respiratory rate and oxygen saturation did not show statistically significant differences between the two groups at the recorded intervals. These findings indicate that the addition of intrathecal midazolam was not associated with measurable changes in the monitored physiological parameters in the present study population. Chattopadhyay et al. reported no clinically significant haemodynamic differences between patients receiving bupivacaine alone and those receiving bupivacaine with midazolam. [4] Joshi et al. also evaluated haemodynamic stability and adverse effects during intrathecal midazolam administration. [5] Hasan reported comparable heart rate, blood pressure and respiratory parameters between the control and midazolam groups. [7] These findings agree with the present observations. The study was limited by its relatively small sample size of 60 patients and its single-centre design. The findings were therefore applicable primarily to patients with ASA physical status I and II undergoing lower abdominal surgery. Long-term neurological outcomes were not assessed. The study also did not provide sufficiently detailed operational definitions to reconcile the separately reported time to first analgesia and duration of analgesia. Further studies with larger sample sizes, clearly defined analgesic endpoints and systematic postoperative follow-up are required.

In patients undergoing lower abdominal surgery, addition of 2 mg intrathecal midazolam to 0.5% hyperbaric bupivacaine was associated with a longer reported duration of postoperative analgesia and longer sensory and motor blockade than bupivacaine alone. Measured haemodynamic and respiratory variables remained comparable between groups. Time to first analgesia and duration of analgesia were distinct study outcomes and have been presented separately. Larger studies with clearly operationalised analgesia endpoints and systematic adverse-event follow-up are warranted.

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