Body surface area and age as a guidance of the dose of intrathecal 0.5% heavy bupivacaine and fentanyl in transurethral procedures

Abstract

Objective: Observe the potency of various drugs doses as milliliters of 0.5% heavy bupivacaine with or without fentanyl for spinal block in transurethral cystoscopic procedures. These doses were calculated from patients and drugs 'characteristic risk factors that interfered with intrathecal drugs spread as weight, height, age, volume, and baricity. Various doses of fentanyl were also added to increase potency of block as necessary except the oldest group.

Material and method: One hundred fifty two ASA I-III adult patients, of both sexes, aged 19 to 80 years, and scheduledfor elective transurethral cystoscopic surgery, were allocated into four groups of age and doses (formulated by earlier studies and the authors' own experiences). Group I was the 16 to 59-years-old, n=32, and received [0.5% hyperbaric bupivacaine in ml (= 5/4 body surface area) + 12.5 mcgfentanyl]. Group 2 was the 60 to 70-years-old group, n=65, and received [0.5% hyperbaric bupivacaine in ml (= I body surface area) + 10 mcgfentanyl]. Group 3 was the 71 to 75-years-old group, n=35, and received[0.5% hyperbaric bupivacaine in ml (= 3/4 body surface area) + 7.5 mcgfentanyl]. Finally, group 4 was the >75 years old, n=20, and received [0.5% hyperbaric bupivacaine in ml (= 3/4 body surface area) without fentanyl]. The statistical analysis included hemodynamic parameters and side effects. Post-hoc analysis was done using ANOVA among the four groups and logistic regression to find any association with successful outcomes.

Results: Eighty-eight percent of the blocks were successful without analgesic supplements (VAS <2). The mean onset time (sensation loss to T10) of patients started at 5.4 +/- 1.4 minutes, time to regress to T11 (expected duration of operable time) was 119.7 +/- 37.9 (45-255) minutes, time to leg up (expected ready to discharge) 132 +/- 39 (65-250) minutes. Hypotension was strikingly low in the study (8%), while bradycardia was 16%, similar to other reports. The other side effects were pruritus 2%, nausea 7%, and vomiting 1%. Total successful without any supplement was 87.5% but increase to 93.4% with low dose of fentanyl <50 mcg intravenously. The formulas predicted less successful blocks for the oldest age groups that LA dose less than 1 BSA, and fentanyl added had a significant weight on the outcomes (OR 1.2635, 95% CI 1.0719-1.4894).

Conclusion: Age and body surface area guided spinal anesthesia is safe. The dose of bupivacaine is lower when combined with fentanyl. Furthermore, hemodynamic stability is better. The technique is suitable for transurethral procedure within 60 minutes but not in longer operation time. Additionally, it needs patients' cooperation due to less potent of motor and pressure sensation block.