The impact of biological sex in peripheral nerve blockade: A prospective pharmacodynamic, pharmacokinetic and morphometric study in volunteers

STUDY OBJECTIVE

The impact of biological sex in peripheral regional anaesthesia is largely unknown. We therefore designed a prospective study in volunteers to investigate the impact of biological sex on pharmacodynamic, pharmacokinetic and morphometric characteristics for peripheral nerve blockade.

METHODS

The initial study plan was powered to include 90 volunteers to find a difference of 35 min in duration of sensory block (primary outcome variable) with 80% power and alpha error at 5%. After discussions in ethical review, a pilot study of 2 x 12 volunteers from each sex were studied. Female and male volunteers received ultrasound guided nerve blockade with 3.0 mL ropivacaine 7.5 mg mL-1. Sensory duration of blockade, as the primary outcome, was evaluated by pinprick testing. Secondary outcomes were sensory onset time of blockade, pharmacokinetic characteristics and the visibility of ulnar nerves using ultrasound. Analyses included Mann-Whitney U-statistics with P<0.05 (two-sided) as significant.

RESULTS

After 24 participants, the median (IQR) duration of sensory blockade was 450 (420; 503) min in women and 480 (450; 510) min in men (P = 0.49). Sensory onset time of blockade, and ultrasound visibility of nerves were also similar between the study groups. The total drug exposure across time (AUC0-infinity) was significantly higher in women (P = 0.017). After a the planned power re-analysis after these 24 study paticipants, which suggested that > 400 subjects would be required with 80% power and alpha error of 5% to find significance for the primary outcome parameter for marginal differences, we terminated the study at this point.

CONCLUSIONS

We did not detect significant differences between female and male study participants in terms of pharmacodynamic and morphometric characteristics after ultrasound guided ulnar nerve blocks. Women did show significantly greater pharmacokinetic ropivacaine exposures. The results of this study indicate that peripheral regional block pharmacodynamic characteristics are independent of the biological sex, whereas pharmacokinetic parameters are sex-dependent.

Evaluation of age-based local anaesthetic dosing of bupivacaine for popliteal sciatic nerve block in children undergoing foot and ankle surgery: A prospective single arm interventional study

Background and Aims

Recommendations on paediatric single-injection local anaesthetic (LA) dosing for peripheral nerve blocks (PNBs) are based on the children's weight and limited by weight-based toxicity concerns. In this study, we assessed the extent of circumferential spread and block characteristics following the injection of an age-based volume (age in years = LA volume) of 0.25% bupivacaine following popliteal sciatic nerve block (PSNB).

Methods

Thirty children aged between 2 and 12 years with the American Society of Anesthesiologists (ASA) physical status I and II and undergoing foot and ankle surgical procedures were given single-injection ultrasound-guided subparaneural PSNB using 0.25% bupivacaine at age-based LA volume after the administration of anaesthesia. The circumferential pattern of LA spread (primary objective) was assessed along the nerve (both cephalad and caudal) using ultrasound from the point of administration and the block characteristics in terms of duration of sensory block.

Results

The mean [standard deviation (SD)] cephalic circumferential LA spread distance was 2.52 (0.68) [95% confidence interval (CI): 2.27-2.76] cm. The mean (SD) caudal circumferential LA spread distance was 2.27 (0.48) [95% CI: 2.09-2.44] cm. The mean (SD) duration of the sensory block was 9.03 (0.97) [95% CI: 8.67-9.38] h.

Conclusion

The age-based LA volume of bupivacaine for ultrasound-guided PSNB resulted in a longitudinal circumferential spread of around 4.7 cm (adding both cephalic and caudal spread) and provided adequate analgesia for nine postoperative hours.

Regional anesthesia for shoulder surgery

Regional anaesthesia should be the preferred technique for analgesia in shoulder surgery, which is a frequent procedure in the daily practice of anaesthesiologists. The use of ultrasound guidance enables the visualization of the relevant nerve structures and the adjacent anatomical details. Low volumes of local anaesthetics reduce the incidence of inadvertent blockade of the phrenic nerve with subsequent respiratory impairment. The additional administration of dexmedetomidine to local anaesthetics prolonges the duration of analgesia with a minimal increased incidence of haemodynamic side effects. An optimal workflow is associated with economical advantages due to an improved use of operation rooms. Attention have to be paid regarding intraoperative hypotension, cerebral hypoperfusion and complications due to positioning.

Intricacies of ultrasound-guided lumbar plexus block in octogenarians: A retrospective case series

Background:

Ultrasound (US)-guided lumbar plexus block (LPB) could be technically challenging in elderly patients. The lumbar paravertebral sonoanatomy is undescribed in the elderly. In an attempt to understand the relevant sonoanatomy, identify the lumbar plexus elements, and understand the difficulties that encountered while performing LPB in elderly patients, we retrospectively analyzed US of 23 elderly patients who were administered US-guided LPBs.

Methods:

After institutional ethics committee approval, we retrospectively reviewed stored US images of lumbar paravertebral sonoanatomy in 23 elderly patients and analyzed psoas major muscle, lumbar vertebral body, lumbar nerve, and lumbar artery.

Results:

On US examination, features of psoas major muscle, lumbar vertebral body, lumbar nerve, and lumbar artery were noted and analyzed.

Conclusion:

US-guided visualization of the components of the lumbar paravertebral area is difficult and inconsistent in the elderly. Therefore, we suggest performing a scout scan, identify the structures, and use neurostimulation all the time for performing LPB in these patients.

Comparison of the effectiveness of circumferential versus non-circumferential spread in median and ulnar nerve blocks. A double-blind randomized clinical trial

BACKGROUND AND OBJECTIVES

Circumferential (C) spread of local anesthetic around the nerve is recommended for a successful nerve block. We tested the hypothesis that C spread produces a more complete block than non-circumferential (NC) spread.

METHODS

We randomized 124 patients undergoing open carpal tunnel syndrome surgery to receive C or NC spread ultrasound-guided median and ulnar nerve blocks. The primary outcome was the proportion of patients who developed complete sensory block measured at 5, 15 and 30 min. The loss of cold sensation was graded as: 0 (complete block), 1 (incomplete block), or 2 (no block). Secondary outcomes included motor block, nerve swelling and adverse events.

RESULTS

In group C, complete sensory block at 5 min was 2.4 (95% CI 1.0 to 5.7; p=0.04) times more frequent in the median nerve and 3.0 (95% CI 1.2 to 7.2; p=0.01) times more frequent in the ulnar nerve compared with group C. However, at 15 and 30 min, it was similar between groups. Complete motor block was more frequent in group C than in group NC for both the median nerve: 1.5 (95% CI 1.1 to 2.2; p<0.01) at 15 min, 1.1 (95% CI 1.0 to 1.2; p=0.02) at 30 min, and the ulnar nerve: 1.7 (95% CI 1.2 to 2.6; p<0.01) at 15 min, 1.2 (95% CI 1.0 to 1.4; p<0.01) at 30 min. The incidence of nerve swelling and adverse effects was similar between groups.

CONCLUSIONS

C spread around the median and ulnar nerves at the level of the antecubital fossa generates more complete sensory and motor blocks compared with NC spread.

TRIAL REGISTRATION NUMBER

EudraCT 2011-002608-34 and NCT01603680.

Intra- and inter-Individual variability in nerve block duration: A randomized cross-over trial in the common peroneal nerve of healthy volunteers

BACKGROUND

The reported variation in nerve block duration is considerable. To individualize nerve block therapy, knowledge of the intra- vs inter-individual variability is essential. We investigated the relative contribution of these 2 parameters to the overall nerve block duration variability.

METHODS

With ethics committee approval, we conducted a randomized cross-over trial where 20 healthy volunteers received 8 common peroneal nerve blockades with lidocaine 0.5% on 4 consecutive days. Allocations were 5 mL to either the right or left side and 10 mL to the opposite side on day 1 and 2 and vice versa on day 3 and 4. With fixed needle entry and nerve target, we repeated local anaesthetic deposition for each blockade. The primary outcome was variation in duration of sensory nerve block defined as insensitivity to a cold stimulus. Data were analysed using linear mixed model regression.

RESULTS

The mean sensory block duration of 380 (95% CI = [342; 418]) minutes on day one was 55 [33; 77] minutes longer than on day two (P < .001), but there were no differences in mean duration between days 2, 3 and 4. The ratios with 2.5; 97.5 percentiles between inter- and intra-individual variation were 2.4 [0.8; 5.2] for the 5 mL blockades and 3.0 [0.9; 6.7] for the 10 mL blockades. The probabilities of inter- to intra-individual variation-ratios >1 were 96% and 97%.

CONCLUSION

The intra-individual variability is a substantially minor contributor to the overall variability in sensory nerve block duration compared with the inter-individual variability.

Longitudinal neural exposure to local anesthetic and nerve block duration: a retrospective analysis of experimental data from healthy volunteer trials

Background and objectives

Characteristics of a nerve block depend on the distribution of local anesthetic (LA) close to the nerve. The relationship between longitudinal distribution of LA and nerve block characteristics has not been investigated in vivo, but one in vitro study showed decrements in action potential amplitudes with increasing exposure length. We describe the influence of longitudinal neural exposure to LA on nerve block duration adjusted for other likely influential factors.

Methods

We analyzed data from an ethical board approved prospective consecutive collected dataset of 180 healthy volunteers with a common peroneal nerve block (2.5–20 mL, 5–40 mg of ropivacaine). Data were retrieved from three independent randomized controlled trials. The longitudinal neural exposure to LA in millimeters was evaluated using ultrasound. Interventional covariates and demographics were retrieved. Nerve block duration, the dependent variable in the primary assessment, was defined as time of insensitivity to a cold stimulus and was evaluated blinded to all other covariates. Using a multiple linear mixed-effects model, we explored the association between neural exposure to LA and nerve block duration.

Results

We found a significant positive association between longitudinal neural exposure to LA and block duration (p<0.01). A 10% increase in longitudinal exposure resulted in an 8.7 (2.5; 15) min increase in block duration. LA dose was associated to block duration (p<0.001) but LA volume had no impact (p=0.93).

Conclusions

Longitudinal neural exposure to LA was significantly associated with nerve block duration. LA dose was the strongest determinant for block duration whereas LA volume had no influence.

Resistance to local anesthesia in people with the Ehlers-Danlos Syndromes presenting for dental surgery

Background

People with the Ehlers-Danlos Syndromes (EDS), a group of heritable disorders of connective tissue, often report experiencing dental procedure pain despite local anesthetic (LA) use. Clinicians have been uncertain how to interpret this apparent LA resistance, as comparison of EDS and non-EDS patient experience is limited to anecdotal evidence and small case series. The primary goal of this hypothesis-generating study was to investigate the recalled adequacy of pain prevention with LA administered during dental procedures in a large cohort of people with and without EDS. A secondary exploratory aim asked people with EDS to recall comparative LA experiences.

Methods

We administered an online survey through various social media platforms to people with EDS and their friends without EDS, asking about past dental procedures, LA exposures, and the adequacy of procedure pain prevention. Among EDS respondents who both received LA and recalled the specific LA used, we compared agent-specific pain prevention for lidocaine, procaine, bupivacaine, mepivacaine, and articaine.

Results

Among the 980 EDS respondents who had undergone a dental procedure LA, 88% (n = 860) recalled inadequate pain prevention. Among 249 non EDS respondents only 33% (n = 83) recalled inadequate pain prevention (P < 0.001 compared to EDS respondents). The agent with the highest EDS-respondent reported success rate was articaine (30%), followed by bupivacaine (25%), and mepivacaine (22%).

Conclusions

EDS survey respondents reported nearly three times the rate of LA non-response compared to non-EDS respondents, suggesting that LAs were less effective in preventing their pain associated with routine office dental procedures.

Dexamethasone as an adjuvant for peripheral nerve blockade: a randomised, triple-blinded crossover study in volunteers

BACKGROUND

The efficacy of dexamethasone in extending the duration of local anaesthetic block is uncertain. In a randomised controlled triple blind crossover study in volunteers, we tested the hypothesis that neither i.v. nor perineurally administered dexamethasone prolongs the sensory block achieved with ropivacaine.

METHODS

Ultrasound-guided ulnar nerve blocks (ropivacaine 0.75% wt/vol, 3 ml, with saline 1 ml with or without dexamethasone 4 mg) were performed on three occasions in 24 male volunteers along with an i.v. injection of saline 1 ml with or without dexamethasone 4 mg. The combinations of saline and dexamethasone were as follows: control group, perineural and i.v. saline; perineural group, perineural dexamethasone and i.v. saline; i.v. group, perineural saline and i.v. dexamethasone. Sensory block was measured using a VAS in response to pinprick testing. The duration of sensory block was the primary outcome and time to onset of sensory block the secondary outcome.

RESULTS

All 24 subjects completed the trial. The median [inter-quartile range (IQR)] duration of sensory block was 6.87 (5.85-7.62) h in the control group, 7.37 (5.78-7.93) h in the perineural group and 7.37 (6.10-7.97) h in the i.v. group (P=0.61). There was also no significant difference in block onset time between the three groups.

CONCLUSION

Dexamethasone 4 mg has no clinically relevant effect on the duration of sensory block provided by ropivacaine applied to the ulnar nerve.

CLINICAL TRIAL REGISTRATION

DRKS, 00014604; EudraCT, 2018-001221-98.

Local Anesthetic Injection Speed and Common Peroneal Nerve Block Duration: A Randomized Controlled Trial in Healthy Volunteers

BACKGROUND AND OBJECTIVES

The speed of local anesthetic (LA) injections in peripheral regional anesthesia ranges from slow continuous infusions (3-12 mL/h) to rapid manual injections (>7500 mL/h). Optimizing injection speed could augment the spread of LA toward the targeted nerves and influence nerve block characteristics. The objective of this study was to investigate whether injection speed of a single dose of LA affects peripheral nerve block duration.

METHODS

After approval from the Danish Regional Scientific Ethics Committee, we enrolled 60 healthy adult volunteers. We used an ultrasound-guided catheter-based technique to perform a common peroneal nerve block. Participants were randomized to receive 4.0 mL of ropivacaine 0.2% with 1 of 5 injection speeds: 12, 60, 300, 600, or 1800 mL/h. Investigators and participants were blinded to group assignment and intervention. Primary outcome was duration of sensory nerve block defined by insensitivity toward cold. Secondary outcomes were duration of motor nerve block, time to onset of sensory nerve block, and grades of sensory and motor nerve block.Intergroup differences were tested by one-way analysis of variance.

RESULTS

We found no differences in sensory block duration between the 5 groups. Durations were median [range]: 11 [6-14], 12 [9-14], 10.5 [2-15], 11 [8-17], and 12 [9-18] hours, respectively (P = 0.294). In addition, we found no differences in secondary outcomes.

CONCLUSIONS

Injection speed of LA in the range of 12 to 1800 mL/h did not affect common peroneal nerve block duration.

CLINICAL TRIAL REGISTRATION

This study was registered at ClinicalTrials.gov, identifier NCT02801799.

Regional anesthesia to ameliorate postoperative analgesia outcomes in pediatric surgical patients: an updated systematic review of randomized controlled trials

Regional anesthesia is becoming increasingly popular among anesthesiologists in the management of postoperative analgesia following pediatric surgery. The main objective of this review was to systematically evaluate the last 5 years of randomized controlled trials on the role of regional anesthesia techniques in alleviating postoperative pain associated with various pediatric surgical procedures. Forty studies on 2,408 pediatric patients were evaluated. The majority of the articles published from 2013 to 2017 reported that the use of regional anesthesia minimized postoperative pain and reduced opioid consumption. Only a few surgical procedures (cholecystectomy, inguinal hernia repair, and non-laparoscopic major abdominal surgery) reported no significant difference in the postoperative pain relief compared with the standard anesthetic management. The growing number of randomized controlled trials in the pediatric literature is very promising; however, additional confirmation is needed to reinforce the use of specific regional anesthesia techniques to provide optimal postoperative pain relief for a few surgical procedures (reconstructive ear surgery, chest wall deformity, hypospadias, umbilical hernia, cleft palate repair) in pediatric patients. More randomized controlled trials are needed to establish regional anesthesia as an essential component of postoperative analgesia management in children.

Holistic ultrasound in trauma: An update

Holistic ultrasound is a total body examination using an ultrasound device aiming to achieve immediate patient care and decision making. In the setting of trauma, it is one of the most fundamental components of care of the injured patients. Ground-breaking imaging software allows physicians to examine various organs thoroughly, recognize imaging signs early, and potentially foresee the onset or the possible outcome of certain types of injuries. Holistic ultrasound can be performed on a routine basis at the bedside of the patients, at admission and during the perioperative period. Trauma care physicians should be aware of the diagnostic and guidance benefits of ultrasound and should receive appropriate training for the optimal management of their patients. In this paper, the findings of holistic ultrasound in trauma patients are presented, with emphasis on the lungs, heart, cerebral circulation, abdomen, and airway. Additionally, the benefits of ultrasound imaging in interventional anaesthesia techniques such as ultrasound-guided peripheral nerve blocks and central vein catheterization are described.

Ultrasound-guided perineural injection for nerve blockade: Does a single-sided injection produce circumferential nerve coverage?

PURPOSE

Our current clinical technique for sonographic-guided perineural injection consists of two-sided perineural needle placement to obtain circumferential distribution of the injectate. This study aimed to determine if a single-side needle position will produce circumferential nerve coverage.

METHODS

Fresh-frozen cadaveric specimens were used for this study. In six upper extremities, a needle was positioned along the deep surface of median, radial, and ulnar nerves in the carpal tunnel, radial tunnel, and cubital tunnel, respectively, and 2 ml of contrast was injected for each nerve. In three pelvic specimens, a needle was positioned deep to the sciatic nerves bilaterally, and 5 ml of contrast was injected. An additional four median nerve injections were performed using superficial surface needle position. The specimens then underwent CT scanning to assess the distribution of the perineural contrast medium.

RESULTS

One hundred percent of the radial, ulnar, and sciatic nerves demonstrated circumferential distribution on CT. Only 50% of the median nerve injections with the needle placed deep to the nerve produced circumferential coverage, whereas 100% of median nerves injected with the needle between the nerve and retinaculum demonstrated circumferential coverage. The average length of spread of perineural injectate was 11.6 cm in the upper extremity and 10.3 cm for the sciatic nerves.

CONCLUSIONS

Using clinical volumes of fluid, needle positioning at the deep surface of upper extremity and sciatic nerves was sufficient to produce circumferential coating of the nerve, except in the carpal tunnel, where placement of the needle between the nerve and flexor retinaculum is recommended. © 2016 Wiley Periodicals, Inc. J Clin Ultrasound 44:465-469, 2016.

Dose effect of local anesthetics on analgesic outcomes for the transversus abdominis plane (TAP) block in children: a randomized, double-blinded, clinical trial

BACKGROUND

Current knowledge on local anesthetic dosage for the TAP block in pediatric patients is very limited.

OBJECTIVE

To evaluate the effect of two escalating local anesthetic doses on postsurgical analgesic outcomes in children receiving a TAP block.

METHODS

The study was a prospective, randomized, double-blinded, clinical trial. Children (<8 years) were randomized to one of the two intervention groups: TAP block with bupivacaine at a dose of 2.5 mg · kg(-1) or 1.25 mg · kg(-1). Analgesic outcomes included pain scores in the postanesthesia care unit (PACU), time to analgesic requirement and total number of analgesic requirements.

RESULTS

Thirty-six patients were recruited in the study. Pain scores in PACU were not different between study groups. The total number of analgesic dosage required in 24 h after surgery was higher in the lower dose group, median (IQR) of 4 (3 to 5) compared to 2.5 (1.5 to 3) in the greater dose group, P = 0.03. There was a clinically but not statistically significant difference in the time to first analgesic requirement in the 2.5 mg · kg(-1) group, median (IQR) of 248 (130 to 367) minutes compared to 146 (95 to 261) minutes in the 1.25 mg · kg(-1) dose group, P = 0.15.

CONCLUSIONS

The use of higher local anesthetic doses for the TAP block in children does not provide benefits on early pain scores but seems to improve analgesic duration and decrease the need for additional analgesics over 24 h after surgery. The use of higher, but yet safe, local anesthetic dosages for TAP blocks is a viable strategy to improve analgesia in children.