Epidural anaesthesia with mixtures of bupivicaine and lidocaine

The effect of local anaesthetic on delayed bleeding in a epigastric flap model of rats

OBJECTIVE

Local anaesthetics are often used in plastic surgery practice. Through their mechanism of action, local anaesthetics produce a sympathetic blockage with a subsequent vasodilatation and a resulting local increase of perfusion. The effect of vasodilation of the local anaesthetics causes bleeding locally resulting in haematoma, bruising and/or pain. We present an experimental study of the effects of local anaesthetics on delayed bleeding.

METHOD

In this animal study, 36 adult male Wistar rats were divided into four groups of nine animals: lidocaine; lidocaine and epinephrine; bupivacaine; and control. An epigastric flap model was harvested. Local anaesthetics that are frequently used in daily practice were administered in equal amounts to the harvested flap.

RESULTS

After 24 hours, the rats were euthanised to collect and measure all coagula under the epigastric flap. No statistically significant differences in relation to the amount of coagulum were found between the groups.

CONCLUSION

Our results suggest that proper haemostasis is achieved, there is no difference on the effect of delayed bleeding between the local anaesthetics which are often used.

Exploring the missing heritability in subjects with hearing loss, enlarged vestibular aqueducts, and a single or no pathogenic SLC26A4 variant

Pathogenic variants in SLC26A4 have been associated with autosomal recessive hearing loss (arHL) and a unilateral or bilateral enlarged vestibular aqueduct (EVA). SLC26A4 is the second most frequently mutated gene in arHL. Despite the strong genotype–phenotype correlation, a significant part of cases remains genetically unresolved. In this study, we investigated a cohort of 28 Dutch index cases diagnosed with HL in combination with an EVA but without (M0) or with a single (M1) pathogenic variant in SLC26A4. To explore the missing heritability, we first determined the presence of the previously described EVA-associated haplotype (Caucasian EVA (CEVA)), characterized by 12 single nucleotide variants located upstream of SLC26A4. We found this haplotype and a delimited V1-CEVA haplotype to be significantly enriched in our M1 patient cohort (10/16 cases). The CEVA haplotype was also present in two M0 cases (2/12). Short- and long-read whole genome sequencing and optical genome mapping could not prioritize any of the variants present within the CEVA haplotype as the likely pathogenic defect. Short-read whole-genome sequencing of the six M1 cases without this haplotype and the two M0/CEVA cases only revealed previously overlooked or misinterpreted splice-altering SLC26A4 variants in two cases, who are now genetically explained. No deep-intronic or structural variants were identified in any of the M1 subjects. With this study, we have provided important insights that will pave the way for elucidating the missing heritability in M0 and M1 SLC26A4 cases. For pinpointing the pathogenic effect of the CEVA haplotype, additional analyses are required addressing defect(s) at the RNA, protein, or epigenetic level.

Effect of Thoracic Epidural Anesthesia on Ventricular Excitability in a Porcine Model

BACKGROUND

Imbalances in the autonomic nervous system, namely, excessive sympathoexcitation, contribute to ventricular tachyarrhythmias. While thoracic epidural anesthesia clinically suppresses ventricular tachyarrhythmias, its effects on global and regional ventricular electrophysiology and electrical wave stability have not been fully characterized. The authors hypothesized that thoracic epidural anesthesia attenuates myocardial excitability and the proarrhythmic effects of sympathetic hyperactivity.

METHODS

Yorkshire pigs (n = 15) had an epidural catheter inserted (T1 to T4) and a 56-electrode sock placed on the heart. Myocardial excitability was measured by activation recovery interval, dispersion of repolarization, and action potential duration restitution at baseline and during programed ventricular extrastimulation or left stellate ganglion stimulation, before and 30 min after thoracic epidural anesthesia (0.25% bupivacaine).

RESULTS

After thoracic epidural anesthesia infusion, there was no change in baseline activation recovery interval or dispersion of repolarization. During programmed ventricular extrastimulation, thoracic epidural anesthesia decreased the maximum slope of ventricular electrical restitution (0.70 ± 0.24 vs. 0.89 ± 0.24; P = 0.021) reflecting improved electrical wave stability. Thoracic epidural anesthesia also reduced myocardial excitability during left stellate ganglion stimulation-induced sympathoexcitation through attenuated shortening of activation recovery interval (-7 ± 4% vs. -4 ± 3%; P = 0.001), suppression of the increase in dispersion of repolarization (313 ± 293% vs. 185 ± 234%; P = 0.029), and reduction in sympathovagal imbalance as measured by heart rate variability.

CONCLUSIONS

Our study describes the electrophysiologic mechanisms underlying antiarrhythmic effects of thoracic epidural anesthesia during sympathetic hyperactivity. Thoracic epidural anesthesia attenuates ventricular myocardial excitability and induces electrical wave stability through its effects on activation recovery interval, dispersion of repolarization, and the action potential duration restitution slope.

Onset and duration of intradermal mixtures of bupivacaine and lidocaine with epinephrine

BACKGROUND/OBJECTIVE

Bupivacaine and lidocaine are often used concurrently, in theory, to combine the more rapid onset of lidocaine and the longer duration of bupivacaine. The purpose of this study was to evaluate this concept.

METHODS

Twenty-five subjects were enrolled in a double-blinded, randomized block design study to evaluate the onset and duration of four different mixtures of lidocaine and bupivacaine with epinephrine. The study was designed to achieve 80% power to detect an effect size of 0.37 at 5% overall significance. The four mixtures tested were: 0.25% bupivacaine with epinephrine (1:200,000); 1% lidocaine with epinephrine (1:100,000); 0.125% bupivacaine and 0.5% lidocaine with epinephrine (1:150,000); and 0.25% bupivacaine and 1% lidocaine with epinephrine (1:150,000). Four intradermal injections were made in the volar forearms of each participant. Time to effect and duration were measured by sensation of a sharp skin prick.

RESULTS

Mean time to onset ranged from 12 s to 29 s without statistical significance across all tested solutions (P=0.891). Mean duration of effect ranged from 6 h 38 min to 7 h 25 min with a statistically significant difference across the tested solutions (P=0.036).

CONCLUSIONS

No statistical benefit was measured when comparing lidocaine with epinephrine, bupivacaine with epinephrine, and mixtures of these local anesthetics with regard to onset of action. While a statistical difference was observed in duration of effect, the clinical benefit measured was narrow.

Ropivacaine, articaine or combination of ropivacaine and articaine for epidural anesthesia in cesarean section: a randomized, prospective, double-blinded study

BACKGROUND AND OBJECTIVES

Initiation of epidural anesthesia with long-lasting local anesthetics consumes a significant amount of time, which could be problematic in busy obstetric anesthesia suites. We have hypothesized that a combination of articaine and ropivacaine provides faster onset and even an early recovery of sensory-motor block characteristics.

METHODS

Sixty term parturients scheduled to have elective cesarean section were randomly allocated into three groups to receive either 20 mL 2% articaine (Group A), 10 mL 2% articaine + 10 mL 0.75% ropivacaine (Group AR) or 20 mL 0.75% ropivacaine (Group R) via lumbar epidural catheter. The onset time of sensory block to T₁₀, T₆ and maximum sensory block level, time to two segments regression from maximum sensory block level, onset time and duration of motor block were all recorded. Intraoperative and postoperative additional analgesic requirements were also recorded.

RESULTS

Demographic data were similar. The onset times of sensorial block to T₁₀ and T₆ were significantly shorter in Groups A and AR in comparison with Group R (p<0.05). The onset times of motor block were similar in all groups, but a more intense motor block was observed in Group R (p<0.05). Two segments regression time and motor block durations were significantly shorter in Groups A and AR in comparison with Group R (p<0.05). Intraoperative supplementary analgesic requirements were higher in Group A than in the other two groups (p<0.05).

CONCLUSION

A combination of 2% articaine and 0.75% ropivacaine for epidural anesthesia in a cesarean section should be preferred over epidural 0.75% ropivacaine alone.

Spinal biopharmaceutics of bupivacaine and lidocaine by microdialysis after their simultaneous administration in rabbits

The aim of the present study was to determine the intrathecal bioavailability of a mixture of lidocaine and bupivacaine in a rabbit model of spinal anesthesia by using the microdialysis technique. Catheter and microdialysis probe were inserted under control of the view either in the epidural or in the intrathecal space. First, the epidural disposition of the mixture of bupivacaine and lidocaine was studied after epidural administration. Then, the intrathecal and plasma dispositions of bupivacaine and lidocaine were investigated following intrathecal or epidural administration. The epidural clearance of bupivacaine was higher than that of lidocaine, suggesting a more significant uptake of bupivacaine into the systemic circulation and/or into the CSF. The intrathecal bioavailability of bupivacaine and lidocaine was 12.3 and 17.9%, respectively, while it was 5.5 and 17.7% following the separate administration of each agent [Clément, R., Malinovsky, J.M., Le Corre, P., Dollo, G., Chevanne, F., Le Verge, R., 1999. Cerebrospinal fluid bioavailability and pharmacokinetics of bupivacaine and lidocaine following intrathecal and epidural administrations in rabbits using microdialysis. J. Pharmacol. Exp. Ther. 289, 1015-21]. After intrathecal administration, a decrease in C(max) and AUC values was observed for bupivacaine in comparison with the separate administration. Moreover, after epidural administration, the systemic resorption was slower and lower, especially for bupivacaine. Such a reduction in the systemic absorption of bupivacaine might increase its intrathecal bioavailability, resulting from a vasoconstrictor effect of lidocaine reducing the systemic absorption of bupivacaine from the epidural space leading to an increase of its extent of absorption through meninges into CSF although its absorption rate was not modified.

Duration of experimental nerve block by combinations of local anesthetic agents

The effects of bupivacaine-prilocaine and meperidine-lidocaine combinations (as compared with those of the agents used alone) on the duration of peripheral sensory nerve block were studied with the infraorbital nerve block model (IONB) in the rat, and those on motor block with spinal anesthesia (SA) in the mouse. The duration of bupivacaine-induced IONB was invariably prolonged when prilocaine was included in the solution. When included in 0.125% bupivacaine, 1.0% prilocaine had a slightly less pronounced enhancing effect than 0.5% prilocaine (24-57% vs. 74%-104%, respectively). The duration of IONB with 1.0% prilocaine was significantly reduced (14-37%) by inclusion of 0.125% bupivacaine. In SA, inclusion in 0.125% bupivacaine of prilocaine (0.5% or 1.0%) prolonged motor block by 128% and 192%, respectively. When included in 0.25% bupivacaine, both 0.5% and 1.0% prilocaine significantly reduced the duration of SA, by 42% and 37%, respectively. With one exception, the duration of IONB by meperidine was significantly shortened (< 44%) when lidocaine was included in the solution. In SA, inclusion of 2% lidocaine with 2% meperidine did not affect the duration of meperidine-induced motor block. The duration of SA obtained with the combination of 4% lidocaine and 4% meperidine was 45% shorter than that induced by 4% meperidine alone. The reasons for these variable effects are not clear, but may be due to interaction or antagonism at any of multiple sites.

The clinical effectiveness of epidural bupivacaine, bupivacaine with lidocaine, and bupivacaine with fentanyl for labor analgesia

STUDY OBJECTIVE

To examine the efficacy of bupivacaine alone and in combination with lidocaine or fentanyl for epidural analgesia during labor.

DESIGN

Randomized, single-blind study.

SETTING

Labor and delivery unit at a university medical center.

PATIENTS

Forty-five primiparas requesting epidural analgesia.

INTERVENTIONS

Following epidural placement at L3-4 interspace, patients received either bupivacaine 0.5% (Group 1, n = 15), bupivacaine 0.25% with lidocaine 1% (Group 2, n = 15), or bupivacaine 0.5% with fentanyl 50 micrograms in 10 ml of saline (Group 3, n = 15). Patients in Groups 1 and 2 received 6 to 10 ml of local anesthetic depending on patient height, while patients in Group 3 received 5 ml of local anesthetic plus 50 micrograms of fentanyl in 10 ml of saline. All solutions contained epinephrine 1:200,000.

MEASUREMENTS AND MAIN RESULTS

Patients were assessed at regular intervals following administration of the epidural solution. Visual analog scale (VAS) scores were used to measure onset of analgesia, time to complete pain relief, duration of analgesia, and patient satisfaction with therapy. The frequency of shivering and pruritus and the extent of sensory/motor block also were evaluated. There were no intragroup differences in time to complete pain relief or patient satisfaction. However, patients in Group 3 noted the most rapid onset and longest duration of pain relief. Patients in Group 3 also experienced significantly less shivering and had the lowest degree of motor block. Two patients in Group 3 experienced mild pruritus.

CONCLUSIONS

Epidurally administered fentanyl safely extended the duration of labor analgesia while reducing bupivacaine dose requirements and magnitude of motor block. In this setting, the combination of bupivacaine and lidocaine offered no clinical advantage over bupivacaine alone.

[Are combinations of local anesthetics dangerous?]

Although local anaesthetic mixtures are often used, there is often no scientific basis for this. Interactions between the local anaesthetics in the mixture can even increase their toxicity. Such interactions may be due to the physical chemical properties of each constituent (this is not a real problem for amide local anaesthetics), to a mutual displacement from the binding sites on the plasma proteins or to an additional effect on membrane receptors. This displacement would seem to benefit the least toxic drug: the toxicity of local anaesthetic mixtures may therefore be reduced; for example, lidocaine and mepivacaine are displaced by bupivacaine. Moreover, the fraction of drug which leaves the blood vessel is greater than the serum free fraction. During chronic administration, neurological toxicity and free fraction are narrowly linked. When using local anaesthetic mixtures, it must be remembered that potency and toxicity of a local anaesthetic are closely correlated and that the toxic effects are, at least, additive.