Maria P.B. Simonetti

Hyaluronidase increases the duration of mepivacaine in inferior alveolar nerve blocks.

PURPOSE To evaluate the duration of the effect of mepivacaine when hyaluronidase is injected immediately prior to the end of pulpal anesthesia. PATIENTS AND METHODS Forty bilateral, symmetrical third molar surgeries were performed in 20 healthy patients. Inferior alveolar nerve block was induced using 2.8 mL 2% mepivacaine with epinephrine. Hyaluronidase (75 turbidity-reducing units) or a placebo was injected 40 minutes after the beginning of pulpar anesthesia (randomized and double-blind trial). The duration of effect in the pulpal and gingival tissues was evaluated by response to painful electrical stimuli applied to the adjacent premolar, and by mechanical stimuli (pin prick) to the vestibular gingiva, respectively. RESULTS In both tissues, the duration of anesthetic effect with hyaluronidase was longer (P < .01) than with the placebo. CONCLUSION Hyaluronidase increases the duration of mepivacaine in inferior alveolar nerve blocks.

Does alkalinization of 0.75% ropivacaine promote a lumbar peridural block of higher quality?

Background and Objectives We did not find clinical studies of the alkalization of ropivacaine in the literature. The objectives of this study were: (1) to determine the quantity of sodium bicarbonate (NaHCO3), which alkalinizes 0.75% ropivacaine (with and without adrenaline); (2) to verify the physico-chemical alterations arising from this alkalization; and (3) to determine whether alkalinized ropivacaine produces a higher-quality epidural block measured via sensory-motor onset, block spread and anesthesia duration. Methods It was determined in the laboratory that 0.012 and 0.015 mEq of NaHCO3, respectively, alkalinized 10 mL of the 0.75% ropivacaine solutions without and with adrenaline (1:200,000). In the second phase, the study was random and double-blind and involved 60 patients divided into 3 groups of 20 (G1, G2, and G3). Via epidural lumbar blocks, these groups received, respectively, 10 mL of 0.75% ropivacaine plus 0.5 mL of 0.9% NaCl (solution A), 10 mL of 0.75% ropivacaine plus 0.0012 mEq of NaHCO3 (solution B), and 10 mL of 0.75% ropivacaine (with adrenaline) plus 0.015 mEq of NaHCO3 (solution C). The pH, PCO2 (partial CO2 pressure), and the nonionized fractions of the 0.75% ropivacaine solutions were compared before and after the addition of 0.9% NaCl or NaHCO3 or adrenaline plus NaHCO3. The motor and sensory onsets, block spread, and the duration of the block were evaluated. Results The values of the pH, PCO2, and nonionized fractions increased significantly in solutions B and C in relation to solution A. No differences among the groups were observed in relation to block spread and sensory-motor onset. The duration of the sensory blocks was significantly greater in the patients in groups G2 and G3. Conclusions This study indicates that the quantity of NaHCO3 needed to alkalize 10 mL of 0.75% ropivacaine at room temperature is 0.012 mEq. When the solution contains adrenaline 1:200,000 (mg · mL−1), up to 0.015 mEq of NaHCO3 may be added. The alkalization of the 0.75% ropivacaine solution did not cause a reduction of sensory-motor onset, but did provide a significant increase in the duration of the epidural block with no significant differences between the solutions with and without adrenaline.

Protective effect of a specific platelet-activating factor antagonist, BN 52021, on bupivacaine-induced cardiovascular impairments in rats.

Administration of the local anaesthetic bupivacaine (1.5 or 2 mg/kg, i.v.) to rats elicited a marked decrease of mean arterial blood pressure (MBP) and heart rate (HR) leading to death (in 67% or 90% of animals respectively). Intravenous injection of the specific platelet-activating factor (PAF) antagonist BN 52021 (10 mg/kg), 30 min before bupivacaine administration (2 mg/kg i.v.) suppressed both the decrease of MBP and HR. In contrast, doses of 1 mg/kg BN 52021 given 30 min before or 10 mg/kg administered 5 min before i.v. injection of bupivacaine were ineffective. When BN 52021 (20 mg/kg i.v.) was injected immediately after bupivacaine (2 mg/kg), a partial reversion of the decrease of MBP and HR was observed, whereas the dose of 10 mg/kg was ineffective. A partial recovery of bupivacaine-induced ECG alterations was observed after pretreatment of the rats with BN 52021. Since the administration of BN 52021, at all doses studied, did not alter MBP and HR at the doses used, the bulk of these results clearly demonstrate a protective action of BN 52021, a specific antagonist of PAF, against bupivacaine-induced cardiovascular toxicity. Thus, consistent with its direct effect on heart, PAF appears to be implicated in bupivacaine-induced cardiovascular alterations.

Comparison of histologic spinal cord and neurologic changes in guinea pigs after subarachnoid block with large volumes of racemic bupivacaine, 50% enantiomeric excess bupivacaine (S75-R25), and levobupivacaine

BACKGROUND AND OBJECTIVES: Levobupivacaine has less central nervous system side effects than racemic bupivacaine, but its anesthetic effect is not as intense. The objective of this experimental study was to compare the adverse effects of large volumes of bupivacaine, S75-R25 bupivacaine, and levobupivacaine injected in the subarachnoid space of guinea pigs. METHODS: Forty guinea pigs were divided in four groups. They were anesthetized with 100% O2 and 2% isoflurane, followed by puncture of the L6-S1 intervertebral space. In Group 1, 2 mL of normal saline were injected; in Group II, 2 mL of 0.5% bupivacaine; in Group III, 2 mL of 0.5% S75-R25 bupivacaine, and in Group IV, 2 mL of 0.5% levobupivacaine. After the animal awakened, neurological exam was done at 0, 60, 120, and 180 minutes, and daily for one week. Animals were killed and underwent perfusion with 4% paraformaldehyde. After fixation, the spinal cord was isolated by dissection and analyzed histologically to evaluate the degree of spinal cord lesions. RESULTS: Guinea pigs in the control group did not present nervous block. Those in Group II presented sensitive and motor block for more than 180 minutes. Animals in Groups III (S75-R25) and IV (levobupivacaine) developed sensitive and motor blockade at moment 0, but at 60 minutes the motor blockade was minimal. Histologic exam in Group I showed no changes. In Group II, severe spinal cord changes were observed. In Groups III and IV, spinal cord changes were mild. CONCLUSIONS: Large volumes of levobupivacaine caused little damage in the central nervous system when compared with bupivacaine. Statistically significant changes were not observed between levobupivacaine and S75-R25 bupivacaine.

Comparative study between bupivacaine (S75-R25) and ropivacaine to evaluate cardiovascular safety in brachial plexus block: Hamaji A et al.: Rev Bras Anestesiol, 2013;63(4):322-326

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