Sex-based differences in local anaesthetic-induced motor block:

Sex and gender differences in anesthesia: Relevant also for perioperative safety?

Sex (a biological determination) and gender (a social construct) are not interchangeable terms and both impact perioperative management and patient safety. Sex and gender differences in clinical phenotypes of chronic illnesses and risk factors for perioperative morbidity and mortality are relevant for preoperative evaluation and optimization. Sex-related differences in physiology, as well as in pharmacokinetics and pharmacodynamics of anesthetic drugs may influence the anesthesia plan, the management of pain, postoperative recovery, adverse effects, patient satisfaction, and outcomes. Further studies are needed to characterize outcome differences between men and women in non-cardiac, cardiac, and transplantation surgery in order to individualize perioperative management and improve patient safety. Transgender patients represent a vulnerable population who need special perioperative care. Gender balance increases team performance and may improve perioperative outcomes.

Sex-dependent prolongation of sciatic nerve blockade in diabetes patients: a prospective cohort study

INTRODUCTION

Diabetes may affect the duration of nerve block after regional anesthesia. This study aimed to compare the durations of sensory and motor block in diabetes versus non-diabetes patients after lower limb nerve block and delineate any sex-based differences in the duration of sensory and motor blocks of both diabetes and non-diabetes patients.

METHODS

This prospective single-blinded cohort study recruited 86 patients who underwent unilateral lower extremity surgery; 52 patients were non-diabetic and 34 were diabetic. Each patient received an ultrasound-guided nerve stimulator-assisted subgluteal sciatic nerve block with 0.75% ropivacaine. Duration of sensory block was assessed with the Semmes-Weinstein monofilament test, and duration of motor block was assessed with dorsal and plantar flexion of the foot.

RESULTS

The sensory and motor block durations of diabetes patients were significantly prolonged versus non-diabetes patients (19.8±6.0 hours vs 15.6±5.1 hours; p<0.05) and (19.5±8.1 hours vs 14.8±5.7 hours, p=0.005), respectively. The durations of sensory and motor block were comparable between male diabetes and non-diabetes patients, but they were significantly longer in female diabetes patients. Multiple regression analysis further revealed that, after adjustment for age and preoperative sensory threshold, diabetes, fasting plasma glucose and HbA1c levels were significantly associated with sensory and motor blocks. Sex analysis showed the association was only present in female diabetes patients, not male diabetes patients.

CONCLUSION

The durations of sensory and motor block are significantly prolonged after subgluteal sciatic nerve block in diabetes patients. Furthermore, the prolonged nerve blockade is present only in diabetes women, not diabetes men.

TRIAL REGISTRATION NUMBER

NCT02482831.

Factors predictive of the onset and duration of action of local anesthesia in mandibular third-molar surgery: a prospective study

The aim of this study was to assess the influence of patients' and surgical variables on the onset and duration of action of local anesthesia (LA) in mandibular third-molar (M3) surgery. Patients scheduled for mandibular M3 surgery were considered for inclusion in this prospective cohort study. Patients' and surgical variables were recorded. Two per cent (2%) lidocaine with 1:100,000 epinephrine was used to block the nerves for extraction of mandibular M3. Then, the onset of action and duration of LA were monitored. Univariate analysis and multivariate regression analysis were used to analyze the data. The final cohort included 88 subjects (32 men and 56 women; mean age ± SD = 29.3 ± 12.3 yr). With univariate analysis, age, gender, body mass index (BMI), smoking quantity and duration, operation time, and 'volume of local anesthetic needed' significantly influenced the onset of action and duration of LA. Multivariate regression revealed that age and smoking quantity were the only statistically significant predictors of the onset of action of LA, whereas age, smoking quantity, and 'volume of local anesthetic needed' were the only statistically significant predictors of duration of LA. Further studies are recommended to uncover other predictors of the onset of action and duration of LA.

Lack of Sex Difference in Minimum Local Analgesic Concentration of Ropivacaine for Ultrasound-Guided Supraclavicular Brachial Plexus Block

Background

Sex differences, which may be an important variable for determining anesthetic requirements, have not been well investigated in the aspect of local anesthetic. This investigation aimed to compare the minimum local analgesic concentration (MLAC) of ropivacaine for ultrasound-guided supraclavicular brachial plexus block (US-SCB) between men and women.

Material/Method

Patients aged 18–45 years undergoing elective forearm, wrist, or hand surgeries under US-SCB were divided into 2 groups according to sex. The initial concentration was 0.375% ropivacaine 20 mL and the concentration for the next patient was determined by the up-down technique at 0.025% intervals. Success was defined as the absence of any pain in response to a pinprick in the region of all 4 terminal nerves and the skin incision within 45 min. The primary outcome was the MLAC of ropivacaine, which was estimated by the Dixon and Massey method. The analgesia duration, which was defined as the time from the end of the US-SCB injection to the time of feeling discomfort and need for additional analgesics, was observed for each patient.

Results

The MLAC of ropivacaine 20 mL for US-SCB was 0.2675% (95% confidence interval [CI], 0.2512–0.2838%) in men and 0.2675% (95% CI, 0.2524–0.2826%) in women. There was no significant difference in MLAC or the analgesia duration between the 2 groups (P>0.05).

Conclusions

We found no significant sex-related differences in MLAC or analgesia duration of ropivacaine for US-SCB.

Sex and gender aspects in anesthetics and pain medication

The influence of sex and gender on anesthesia and analgesic therapy remains poorly understood, nevertheless the numerous physiological and pharmacological differences present between men and women. Although in anesthesiology sex-gender aspects have attracted little attention, it has been reported that women have a greater sensitivity to the non-depolarizing neuroblocking agents, whereas males are more sensitive than females to propofol. It has been suggested that men wake slower than women after general anesthesia and have less postoperative nausea and vomiting. Sexual hormones seem to be of importance in the onset of differences. Nevertheless, in the last years, sex-gender influences on pain and analgesia have become a hot topic and data regarding sex-gender differences in response to pharmacologic and non-pharmacologic pain treatments are still scanty, inconsistent, and non-univocal. In particular, females seem to be more sensitive than males to opioid receptor agonists. Women may experience respiratory depression and other adverse effects more easily if they are given the same doses as males. Evidently, there is an obvious need for more research, which should include psychological and social factors in experimental preclinical and clinical paradigms in view of their importance on pain mechanism, in order to individualize analgesia to optimize pain relief.

Sex-related differences of patient-controlled epidural analgesia for postoperative pain

Gender differences in pain modulation are evident but data are rare with regard to perioperative regional analgesia. The aim of the present analysis was to assess gender-related differences in pain ratings, analgesic consumption, and adverse events in a large group of patients treated with patient-controlled epidural analgesia (PCEA) after major surgery. Data from 14,988 adult patients (6506 women; 8482 men) receiving a PCEA between January 1998 and December 2009 were examined. Demographic data and postoperative measurements assessed by the Acute Pain Service, including total PCEA consumption, pain scores, and complications, were analyzed by using PASW Statistics (18.0; SPSS Inc, Chicago, IL, USA). Beyond standard descriptive analyses, gender-related differences were investigated using a stepwise multivariate analysis of variances. Postoperative pain scores during rest and movement were almost equal between men and women. However, women showed lower total PCEA consumption consistently throughout the 5-day observation period (relative reduction by 1.7%-10.2% compared to men; P=0.00). Total PCEA consumption did not interact with surgical site (abdomen, thorax, extremity) (P=0.379) or age (<50, 50-75, >75 years; P=0.330), but was influenced by body mass index (P=0.017) and vomiting (P=0.011). Furthermore, motor blockade was greater in females compared to males (P=0.000). In patients treated with PCEA, gender differences in numeric rating scale scores exist but are not clinically relevant. However, reduced total PCEA consumption in women might be a consequence of an increased incidence of motor blockade and vomiting; the latter point towards an opioid-free PCEA solution in female patients at high risk for vomiting.