Determination of the ED95 of intrathecal hyperbaric prilocaine with sufentanil for scheduled cesarean delivery: a dose-finding study based on the continual reassessment method

Crystallization of short-acting and intermediate-acting local anesthetics when mixed with adjuvants: a semiquantitative light microscopy analysis

INTRODUCTION

The addition of adjuvants to short-acting local anesthetics (LA) is common practice in clinical routine to speed up block onset and decrease pain on injection. In a previous study, we observed the development of microscopic crystal precipitations after bupivacaine or ropivacaine were mixed with adjuvants; this follow-up study is intended to clarify whether crystallization (A) also occurs in short-acting or intermediate-acting LA-adjuvant mixtures, (B) changes over time, and (C) is associated with the solutions' pH.

METHODS

Lidocaine 2%, prilocaine 2%, mepivacaine 2%, procaine 2% and chloroprocaine 2% were individually mixed with clonidine, dexamethasone, dexmedetomidine, epinephrine, fentanyl, morphine or sodium bicarbonate 8.4% in clinically established ratios. For each mixture, we measured initial pH and recorded crystallization patterns at 0, 15, 30 and 60 min using a standardized, semiquantitative light microscopy approach.

RESULTS

Lidocaine 2% and mepivacaine 2% plus sodium bicarbonate 8.4%, and mepivacaine 2% plus dexamethasone developed delayed grade 5 crystallization over 1 hour. Prilocaine-based, procaine-based and chloroprocaine-based mixtures showed much less pronounced crystallization, with a maximum of grade 2. Initial pH and grade of crystallization showed weak monotonic relationships at time points t0, t15 and t30 (ρ=-0.17, 0.31 and 0.32, (all p>0.05)) and a moderate relationship time point t60 (ρ=0.57 (p=0.0003)) CONCLUSIONS: Our study revealed high grades of crystallization in lidocaine/mepivacaine-bicarbonate and mepivacaine-dexamethasone mixtures, although these were previously considered safe for local, perineural or neuraxial use. Our findings cast particular doubt on the safety of preparing these formulations for later use.

Influence of height on ED95 of intrathecal 2-chloroprocaine for knee arthroscopy: A prospective dose-response clinical trial

BACKGROUND

Plain 2-chloroprocaine , a rapid acting amino-ester-type local anaesthetic, is used in short ambulatory procedures under spinal anaesthesia. The ED 95 of 2-chloroprocaine for lower limb surgery has not yet been defined. Moreover, patients' body height could influence the effects of the administered dose.

OBJECTIVES

The aim of this study was to determine the ED 95 of plain 2-chloroprocaine based on the height of patients undergoing ambulatory knee arthroscopy under spinal anaesthesia using the continual reassessment statistical method (CRM).

DESIGN

Prospective, dose-response, double blind, controlled, bi-center, clinical trial.

SETTING

One university teaching hospital in Brussels and one general teaching hospital, Braine l'Alleud, Belgium. Université libre de Bruxelles.

PATIENTS

ASA I-III (120 patients) scheduled for day-case knee arthroscopy under spinal anaesthesia.

INTERVENTIONS

Patients were divided into three groups of 40, each comprising 10 cohorts of 4 patients, according to their respective heights (Group 1: 150-165 cm, Group 2: 166-180 cm, Group 3: 181-195 cm). Each patient enrolled into one of the 3 groups received an intrathecal dose of plain 2-chloroprocaine determined by the CRM. The starting doses for the first cohorts of four were 40 mg in group 1, 45 mg in group 2 and 50 mg in group 3. The doses for subsequent cohorts were determined by CRM of outcomes in all patients in the previous competed cohorts. Anaesthesia was considered successful when there was a lack of pinprick or cold sensation up to T12, the visual analogue scale score for tourniquet pain was < 2 and no pain during surgery.

MAIN OUTCOMES

The primary outcome was the success or failure of the block. Side effects were also recorded.

RESULTS

ED 95 of 2-chloroprocaine is 40 mg in group 1, 35 mg in group 2, 45 mg in group 3. Groups were different in terms of height and gender ( P  < 0.05) and similar in terms of body mass index and age ( P  > 0.05).

CONCLUSION

The ED95 of intrathecal 2-chloroprocaine for patients undergoing ambulatory knee arthroscopy is between 35 and 45 mg. Height could be a factor involved in the calculation, and patient sex could partly explain the nonlinear relation between height and dose.

TRIAL REGISTRY NUMBER

Clinicaltrials.gov NCT03882489.

Comparison of equipotent doses of intrathecal hyperbaric prilocaine 2% and hyperbaric bupivacaine 0.5% for elective caesarean section: A prospective, randomised, controlled, two-centre clinical trial

BACKGROUND

Elective caesarean section is performed mainly under spinal anaesthesia using hyperbaric bupivacaine combined with opioids. Despite rapid onset, good quality anaesthesia, bupivacaine provides a long duration of motor block and is related to maternal hypotension. Current policies appeal for implementation of enhanced recovery procedures after caesarean section. Hyperbaric prilocaine is an intermediate-acting local anaesthetic known for its efficacy in ambulatory surgery. Evidence on the clinical relevance of intrathecal prilocaine use for caesarean section is currently lacking.

OBJECTIVES

We aimed to investigate whether hyperbaric prilocaine would offer a shorter motor block and recovery than bupivacaine, when comparing equipotent doses. We also assessed the characteristics of sensory block, maternal haemodynamics and side effects for both mother and newborn.

DESIGN

Prospective, randomised, double-blind, controlled, two-centre, clinical trial.

SETTING

One university teaching hospital and one general teaching hospital in Brussels, Belgium.

PATIENTS

American Society of Anesthesiologists' physical status 2 parturients (n = 40) undergoing caesarean section under spinal anaesthesia.

INTERVENTIONS

Patients were randomly assigned to receive spinal anaesthesia using hyperbaric prilocaine 50 mg or hyperbaric bupivacaine 10 mg, both given with sufentanil 2.5 μg and morphine 100 μg. An epidural catheter was introduced as a backup in case of failure.

MAIN OUTCOMES

The primary outcome was the motor block regression (modified Bromage scale 1 to 6). Secondary outcomes included sensory block characteristics, first unassisted ambulation, maternal side effects, newborns' parameters and overall satisfaction.

RESULTS

Median [IQR] motor block was significantly shorter in the hyperbaric prilocaine group (110 [104 to 150] min versus 175 [135 to 189] min, P = 0.001). First unassisted ambulation was achieved earlier after prilocaine (204.5 [177 to 246.5] min versus 314 [209.25 to 400] min, P = 0.007), and the incidence of maternal hypotension was significantly higher with bupivacaine (P = 0.033). No supplementary epidural analgesia was needed.

CONCLUSION

Prilocaine provides shorter motor block, faster recovery and better haemodynamic stability than bupivacaine while offering equivalent surgical anaesthesia.

TRIAL REGISTRATION

Clinicaltrials.gov: NCT02973048, EudraCT: 2016-003010-26.