A comparative study of isobaric and hyperbaric solution of bupivacaine for spinal anaesthesia in caesarean section. Intrathecal hypobaric versus hyperbaric bupivacaine with morphine for cesarean section. Subarachnoid analgesia for caesarean section. A double-blind comparison of plain and hyperbaric 0.5% bupivacaine. Comparison of 9 mg of intrathecal plain and hyperbaric bupivacaine both with fentanyl for cesarean delivery. Small-dose hyperbaric versus plain bupivacaine during spinal anesthesia for cesarean section. Spinal anesthesia for cesarean section: comparative study between isobaric and hyperbaric bupivacaine associated to morphine.
Though hyperbaric solution of bupivacaine following intrathecal injection had satisfactory spread of analgesia, it regressed rapidly with more side effects. Isobaric bupivacaine seemed to provide a slow regression of analgesia with fewer undesirable effects except for its inadequate spread of analgesia. As a result, if the dosages as well as the time of administration of isobaric solution are well adjusted, we believe that it is safe and reliable with an excellent level of analgesia for caesarean section. Both hyper- and hypobaric solutions of bupivacaine are often combined with morphine to provide subarachnoid anesthesia for cesarean section. Differences in the baricity of subarachnoid solutions influence the intrathecal distribution of anesthetic drugs and would be expected to influence measurable clinical variables. We compared the effects of hyper- and hypobaric subarachnoid bupivacaine with morphine to determine whether one has significant advantages with regard to intraoperative anesthesia and postoperative analgesia in term parturients undergoing elective cesarean section. Thirty parturients were randomized to receive either hyper- or hypobaric bupivacaine (15 mg) with morphine sulfate (0.2 mg). Intraoperative outcomes compared included extent of sensory block, quality of anesthesia, and side effects. Postoperative outcomes, including pain visual analog scale scores, systemic analgesic requirements, and side effects, were monitored for 48 h. Sedation effects were quantified and compared using Trieger and digit-symbol substitution tests. We detected no differences in sensory or motor block, quality of anesthesia, quality of postoperative analgesia, incidence of side effects, or psychometric scores. Both preparations provide highly satisfactory anesthesia for cesarean section and effective postoperative analgesia. Implications: Dextrose alters the density of intrathecal bupivacaine solutions and is thought to influence subarachnoid distribution of the drug. We randomized parturients undergoing cesarean section to one of two often used spinal bupivacaine preparations, hypobaric and hyperbaric. We detected no differences in clinical outcomes between groups. Equal volumes (2.5 ml, 12.5 mg) of plain 0.5% bupivacaine (glucose-free) and hyperbaric 0.5% bupivacaine (in 8% glucose) were compared in a randomized double-blind study of 40 patients undergoing Caesarean section under subarachnoid anaesthesia. There were no differences in the rate of onset, maximum spread, number of patients with high cervical levels, duration of anaesthesia or incidence of post-spinal headaches between the two solutions. The median maximum cephalad levels of analgesia were (hyperbaric) T1 (range C1-T4), and (plain) T2 (range C1-T4). Thirteen patients in the hyperbaric group and 10 in the isobaric group required i.v. ephedrine to treat hypotension. Nine patients (23%) developed a post-spinal headache, and three were treated with an extradural blood patch. We randomized 76 parturients to a double-blinded trial to receive spinal anesthesia with either hyperbaric or plain bupivacaine 9 mg with fentanyl 20 microg for elective cesarean delivery. A combined spinal-epidural technique was used. The onset and duration of anesthesia (absence of pinprick sensation), analgesia (absence of sharp sensation to pinprick), and absence of cold sensation and motor block were measured until recovery from the motor block. No major differences were seen in onset or duration of anesthesia between the groups. Motor block, however, vanished faster when hyperbaric bupivacaine was used (P < 0.05). The level of anesthesia (no pinprick sensation) required for painless operation was at dermatome T5. At this time, the absence of cold sensation ranged from dermatome T1 to C3. The median time for the anesthesia to reach dermatome T5 was 10 min. Cervical spread of pinprick anesthesia was noted in six patients, and five needed supplementary analgesics during surgery (not significant between the groups). Maternal satisfaction was good. Nine milligrams of either plain or hyperbaric bupivacaine with fentanyl intrathecally provided similar onset, depth, and duration of sensory anesthesia for cesarean delivery with good maternal satisfaction. Motor block developed and diminished faster with the hyperbaric solution.
                Nine milligrams of either plain or hyperbaric bupivacaine with fentanyl intrathecally provided similar onset, depth, and duration of sensory anesthesia for cesarean delivery with good maternal satisfaction. Motor block developed and diminished faster with the hyperbaric solution. In a double-blind, randomized trial, 98 parturients undergoing cesarean section received either hyperbaric or plain bupivacaine 6.6 mg combined with sufentanil 3.3 microg as part of a combined spinal-epidural procedure. To prevent hypotension, 1000 mL of lactated Ringer's solution, 500 mL of hydroxyethyl starch 6%, and ephedrine 5 mg were administered i.v. The height of the block was equal in both groups, but more patients in the plain group had blocks that were either too high or too low (P < 0.01). The number of patients requiring epidural supplementation was equal in both groups. Strict criteria were used to treat hypotension. The overall incidence of systolic blood pressure (<90 mm Hg) was 13%, whereas it was more pronounced in the plain group (21% vs 6% in the hyperbaric group, P < 0.05), which required more ephedrine (P < 0.05) and in which a greater incidence of nausea was noticed (P < 0.05). We conclude that the use of a small dose of intrathecal bupivacaine combined with sufentanil plus our described preloading regimen resulted in a lower incidence of hypotension. Further, we conclude that the use of hyperbaric bupivacaine in this manner provides a more reliable block and a lower incidence of hypotension than plain bupivacaine. Implications: A small dose of hyperbaric bupivacaine 0.5% combined with sufentanil used intrathecally during cesarean section offered a more reliable cephalad spread of the spinal block than the glucose-free combination, which was reflected in a lower incidence of hypotension and nausea. Bupivacaine preparations, plain or with glucose, are frequently used in the clinical practice. Blockade upper level is determined by local anesthetic spread in the CSF. This study aimed at comparing isobaric and hyperbaric bupivacaine in patients submitted to spinal anesthesia for Cesarean section.
                In this prospective, randomized and double-blind study 60 patients submitted to spinal anesthesia for Cesarean section were distributed in two groups: IB - (0.5% isobaric bupivacaine, 12.5 mg) and HB - (0.5% hyperbaric bupivacaine, 12.5 mg). After monitoring, venous puncture was performed followed by hydration with lactated Ringers solution. Spinal puncture was paramedially performed at L3-L4 interspace with 27G Quincke needle. Following the CSF dripping, morphine (100 microg) and bupivacaine were separately injected at the speed of 1 ml. 15 s(-1). With the patient back to supine position, two parameters were recorded: onset time (absence of sensitivity in L3) at 1-minute intervals as well as motor and sensory block after 20 minutes. All patients were kept with preanesthetic blood pressure levels until umbilical cord clamping, and if necessary, ephedrine was administered. Neonates were evaluated by Apgars score at 1 and 5 minutes. Sensory and motor blocks were also evaluated at PACU 120 minutes after local anesthetic injection.
                Groups were homogeneous. Onset time: Group IB (1', 50") and HB (1', 33"), with no statistical difference. Motor and sensory block at twenty minutes showed no significant difference. Ephedrine consumption: IB (11.83 mg) and HB (14.17 mg), showed also no statistical difference. PACU motor block evaluation showed significant differences.
                We concluded that 12.5 mg isobaric and hyperbaric bupivacaine associated to morphine (100 microg) in spinal anesthesia for Cesarean section in term pregnant women are effective and present similar profiles.
The criteria for conversion to general anaesthesia should be clearly defined in future research. This review found that intrathecal hyperbaric bupivacaine had a more rapid onset of sensory blockade at the T4 level than isobaric bupivacaine. It may also result in less need for conversion to general anaesthesia and supplemental analgesia. However, due to the rarity of this outcome, variability in the dose, use of adjuvant drugs and differences in the technique used for regional anaesthesia the evidence is weak. Any apparent advantage of hyperbaric bupivacaine needs to be confirmed in larger randomized trials. There were no differences in the adverse effects studied.