Comparison of Hypobaric, Hyperbaric, and Isobaric Solutions of Bupivacaine During Continuous Spinal Anesthesia

Abstract

This study was designed to compare the anesthetic properties of hypobaric bupivacaine with those of isobaric and hyperbaric solutions when administered in the supine position in an elderly population undergoing hip surgery using continuous spinal anesthesia. Plain bupivacaine (0.5%) was mixed with equal volumes of 10% dextrose (hyperbaric), 0.9% NaCl (isobaric), or distilled water (hypobaric) to obtain 0.25% solutions. In a double-blind fashion, all patients received 3 mL (7.5 mg) of their particular solution injected through the spinal catheter in the horizontal supine position. The sensory level obtained in the hyperbaric group (median, T4; range, T3-L3) was significantly higher than in both the isobaric (median, T11; range, T6-L1) and hypobaric (median, L1; range, T4-L3) groups. A motor blockade of grade 2 or 3 was obtained in 14 of 15 and 12 of 15 patients in, respectively, the hyperbaric and isobaric groups, but only in 8 of 15 patients in the hypobaric group. After the initial injection of 3 mL (7.5 mg), a sensory level of T10 and a motor blockade of grade 2 or 3 was obtained in 14 of 15, 5 of 15, and 3 of 15 patients in the hyperbaric, isobaric, and hypobaric groups, respectively. All remaining patients received 1 or 2 additional milliliters (2.5-5 mg) and achieved these required anesthetic conditions, except for one patient in the hyperbaric group and eight patients in the hypobaric group in whom anesthesia was achieved with hyperbaric tetracaine. The decrease in mean arterial pressure was significantly more severe in the hyperbaric (30%) than in either the isobaric (18%) or hypobaric (14%) groups.(ABSTRACT TRUNCATED AT 250 WORDS)

A comparison of the effects of hyperbaric and isobaric bupivacaine spinalanesthesia on hemodynamics and heart rate variability

“…Similarly, Kooger Infante et al (23) observed that following spinal anesthesia with 3 mL (15 mg) of hyperbaric bupivacaine, patients who had 30° torso elevation had a lower sensory block height and incidence of hypotension compared to those in the horizontal position. The most significant difference between our study and the designs of the studies that showed that hyperbaric bupivacaine caused higher sensory block heights and blood pressure decreases is supine positioning after subarachnoid injections (11,21,22). In our study, we applied torso elevation to all patients after spinal anesthesia.…”

“…Hyperbaric bupivacaine has a greater tendency for cephalic spread than isobaric bupivacaine; therefore, it has a greater peak sensory block height and, as a result, a greater incidence of hypotension and blood pressure drops in patients undergoing nonobstetric surgery (11,12,21,22).…”

A randomized comparison of different doses of intrathecal levobupivacaine combined with fentanyl for elective cesarean section: prospective, double-blinded study

“…Sen et al [18] compared the same doses of hyperbaric and isobaric levobupivacaine and found that the speed of onset and offsets of motor and sensory block were significantly faster with hyperbaric levobupivacaine, although the hemodynamic parameters and incidences of adverse effects were similar. However, according to a report by Van Gessel et al [19], the decrease in mean arterial pressure was significantly more severe in the hyperbaric (30%) than in the isobaric (18%) or hypobaric (14%) solutions. Another study reported that the hyperbaric group was associated with an increased incidence of hypotension compared with the plain group [20].…”

Combining Intrathecal Bupivacaine and Meperidine during Caesarean Section to Prevent Spinal Anaesthesia-Induced Hypotension and other Side-Effects

“…Small doses of isobaric solutions have a limited distribution, whereas hyperbaric solutions have a diffuse distribution depending on the patient's position and can, therefore, induce serious hypotension by causing total sympathetic block. 15,16 In obstetric patients, however, the intrathecal use of plain or hyperbaric bupivacaine alters the height of the spinal block used. 17,18 Srivastava et al 19 compared the effects of hyperbaric bupivacaine versus plain bupivacaine combined with fentanyl with regard to the degree of sensory and motor block, the quality of intraoperative anaesthesia, and the …”