Nerve injury and regional anaesthesia

Regional Anesthesia in the Elite Athlete

Elite athletes are exposed to an elevated risk of musculoskeletal injury which may present a significant threat to an athlete's livelihood. The perioperative anesthetic plan of care for these injuries in the general population often incorporates regional anesthesia procedures due to several benefits. However, some concern exists regarding the potential for regional anesthesia to adversely impact functional recovery in an elite athlete who may have a lower tolerance for this risk. This article aims to review the data behind this concern, discuss strategies to improve the safety of these procedures and explore the features of consent in this patient population.

The potencies and neurotoxicity of intrathecal levobupivacaine in a rat spinal model: Effects of concentration

This study was aimed at examining the anesthetic effects and spinal cord injuries in the rats by intrathecal injection of levobupivacaine at different concentrations. Rats with successful intrathecal cannulation were selected and randomly divided into six groups (n = 72), and administered 0.1 mL of 0.125%, 0.25%, 0.5%, or 0.75% levobupivacaine, saline or 5% lidocaine via intrathecal catheters. The potency of levobupivacaine was evaluated by walking behavior. To identify the motor and sensory function, walking behavior and paw withdrawal thresholds (PWTs) were measured once a day. After 7 days, the L4-5 spinal cord segments were removed for histological examination. The onset time of 0.125% levobupivacaine intrathecal injection was 70.0 ± 8.9 s, and the maintenance time was 9.5 ± 1.8 min. The onset time of 0.75% levobupivacaine intrathecal injection was significantly shortened to 31.0 ± 5.5 s, and the maintenance time was significantly extended to 31.3 ± 5.4 min. The severe injury was observed in the 5% lidocaine group, while milder injury was observed in the 0.75% levobupivacaine group. The damage in the 0.5% levobupivacaine group was mild, and there were no histological abnormalities in the 0.125%, 0.25% levobupivacaine and saline groups. The neurotoxicity of intrathecally administered levobupivacaine was concentration dependent. In addition, higher concentrations of levobupivacaine were associated with shorter onset and longer maintenance times. The clinical concentration of levobupivacaine should not exceed 0.5% to avoid potential damage.

"Knowing It Before Blocking It," the ABCD of the Peripheral Nerves: Part C (Prevention of Nerve Injuries)

"A clever person solves the problem. A wise person avoids it" (Albert Einstein). There is no convincing evidence that any modality 100% effectively prevents nerve injury. The risk of nerve injury remains the same even with the ultrasound due to limitations in the resolution of images and inter-operator and inter-patient differences. In a nutshell, caution is required when dealing with precious nerves in the perioperative period, either during peripheral nerve blocks (PNBs), patient positioning, or surgery. Identifying pre-existing nerve injury, either due to trauma or an existing neuropathy, and preventing further nerve injury should be an important goal in providing safe regional anesthesia (RA). Multimodal monitoring is key to avoiding multifactorial nerve injuries. The use of triple guidance (ultrasound + peripheral nerve stimulator + injection pressure monitor) during PNBs further improves the safety of RA. The ultrasound helps in real-time visualization of the nerve, needle, and drug spread; the peripheral nerve stimulator helps confirm the target nerves; and the injection pressure monitor helps avoid nerve injury. Such multimodalities can also give the confidence to administer PNB without risk of nerve injury. This article is part of the comprehensive overview of the essential understanding of peripheral nerves before blocking them. It describes various preventive measures to avoid peripheral nerve injuries while administering PNBs. It will help readers understand the importance of prevention in each step to avoid perioperative PNIs.

Regional Anesthesia in the Elite Athlete

Elite athletes are exposed to an elevated risk of musculoskeletal injury which may present a significant threat to an athlete's livelihood. The perioperative anesthetic plan of care for these injuries in the general population often incorporates regional anesthesia procedures due to several benefits. However, some concern exists regarding the potential for regional anesthesia to adversely impact functional recovery in an elite athlete who may have a lower tolerance for this risk. This article aims to review the data behind this concern, discuss strategies to improve the safety of these procedures and explore the features of consent in this patient population.

[Arachnoiditis following spinal anesthesia-Case report and review of the literature]

A 61-year-old woman underwent a tension-free vaginal tape (TVT) operation due to stress incontinence. After technically difficult spinal anesthesia with two attempts the patient developed symptoms of nerve irritation, complained about neckache and headache and showed signs of agitation. The regimen was shifted to general anesthesia and surgery was performed. Because of postoperatively persistent headache and sensory disturbances an MRI scan of the lumbar spine was performed on the first postoperative day without pathological findings. The patient was able to leave the hospital after 1 week with significant relief of symptoms but 3 weeks later she developed neurocognitive impairment with memory deficits. A second MRI scan of the head now showed signs of disturbance of CSF circulation with hydrocephalus. Treatment was performed with drainage and ventriculoperitoneal shunt. Further evaluation showed a severe, multisegmental arachnoiditis and the patient developed a progressive paraparesis. The patient presented her case for assessment to a commission on medical malpractice 13 months after anesthesia. The commission detected no treatment errors. In connection to the case report a literature review of characteristics and etiologies of chronic adhesive arachnoiditis is given, which is a known but very rare complication of spinal anesthesia or similar procedures.

Detection of intraneural needle-placement with multiple frequency bioimpedance monitoring: a novel method

Electrical impedance measurements have been used to detect intraneural needle placement, but there is still a lack of precision with this method. The purpose of the study was to develop a method for the discrimination of nerve tissue from other tissue types based on multiple frequency impedance measurements. Impedance measurements with 25 different frequencies between 1.26 and 398 kHz were obtained in eight pigs while placing the tip of a stimulation needle within the sciatic nerve and in other tissues. Various impedance variables and measurement frequencies were tested for tissue discrimination. Best tissue discrimination was obtained by using three different impedance parameters with optimal measurement frequencies: Modulus (126 kHz), Phase angle (40 kHz) and the Delta of the phase angle (between 126 and 158 kHz). These variables were combined in a Compound variable C. The area under the curve in a receiver operating characteristic was consecutively increased for the Modulus (78 %), Phase angle (86 %), Delta of the phase angle (94 %), and the Compound variable C (97 %), indicating highest specificity and sensitivity for C. An algorithm based on C was implemented in a real-time feasibility test and used in an additional test animal to demonstrate our new method. Discrimination between nerve tissue and other tissue types was improved by combining several impedance variables at multiple measurement frequencies.

Effects of epinephrine in the epidural space on the incidence of blood vessel injury by epidural catheter insertion for cesarean section: a prospective, randomized, double-blind study

STUDY OBJECTIVE

To evaluate the effects of epinephrine (1:200,000) in the epidural space on the incidence of blood vessel injury by epidural catheter insertion for cesarean section.

DESIGN

Prospective observational study.

SETTING

University-affiliated teaching hospital.

PATIENTS

Four hundred laboring women with singleton cephalic presentations at term who underwent cesarean section and requested continuous epidural analgesia.

INTERVENTIONS

Predistension of 5 mL of isotonic sodium chloride solution containing epinephrine (1:200,000) or 5 mL of isotonic sodium chloride solution through an epidural needle before catheter insertion.

MEASUREMENTS

Cases with bloody fluid in the epidural needle or catheter during catheter insertion, aspiration of frank blood from the epidural catheter, and blood noted in the caudal end of the epidural catheter upon removal were recorded.

MAIN RESULTS

Eight parturients were excluded from the analysis for technical reasons. There were no significant differences between patients in the 2 groups with respect to cases with bloody fluid in the epidural needle during catheter insertion (7.6% vs 9.8%, P = .44), the epidural catheter during catheter placement (6.0% vs 6.7%, P = .80), aspiration of frank blood in the epidural catheter (1.0% vs 1.0 %, P = .98), and blood noted in the caudal end of the epidural catheter upon removal (27.3% vs 30.4 %; P > .49).

CONCLUSION

Twenty-five micrograms of epinephrine (1:200,000) in the epidural space does not reduce the incidence of blood vessel injury induced by insertion of an epidural catheter.

Duration of upper and lower extremity peripheral nerve blockade is prolonged with dexamethasone when added to ropivacaine: a retrospective database analysis

BACKGROUND

Dexamethasone, when added to local anesthetics, has been shown to prolong the duration of peripheral nerve blocks; however, there are limited studies utilizing large numbers of patients. The purpose of this study was to examine the effect of adding dexamethasone to ropivacaine on duration of nerve blocks of the upper and lower extremity.

METHODS

We reviewed 1,040 patient records collected in an orthopedic outpatient surgery center that had received an upper or lower extremity peripheral nerve block with ropivacaine 0.5% with or without dexamethasone and/or epinephrine. The primary outcome was duration of analgesia in upper or lower extremity blocks containing dexamethasone as an adjunct. Secondary outcomes included postoperative patient pain scores, satisfaction, and the incidence of block related complications. Linear and ordinal logistic regression models were used to examine the independent effect of dexamethasone on outcomes.

RESULTS

Dexamethasone was observed to increase median block duration by 37% (95% confidence interval: 31-43%). The increased block duration persisted within body regions (upper and lower) and across a range of block types. Dexamethasone was also observed to reduce pain scores on the day of surgery (P = 0.001) and postoperative day 1 (P < 0.001). There was no significant difference in duration of nerve blocks when epinephrine (1:400,000) was added to 0.5% ropivacaine with or without dexamethasone.

CONCLUSION

The addition of dexamethasone to 0.5% ropivacaine prolongs the duration of peripheral nerve blocks of both the upper and lower extremity.

Effects of predistention with normal saline containing adrenaline on blood-vessel injury during epidural catheter placement

This study investigated the effects of predistention with normal saline containing adrenaline on vascular plexus injury during epidural catheter placement. Three hundred parturients undergoing caesarean sections were randomly divided into three groups. Group I (n = 102) received an epidural injection with 5 ml normal saline; group II (n = 93) received 5 ml normal saline containing adrenaline (5 μg/ml); group III (n = 100) received direct epidural catheter placement. Five women were excluded from the analysis for technical reasons. The incidence of bloody fluid in the epidural needle was significantly lower in groups I and II compared with group III (eight [7.8%] and seven [7.5%] versus 17 [17.0%], respectively). There were no significant differences in the incidence of bloody fluid in the epidural catheter or in the incidence of intravascular epidural catheter placement between the three groups. Predistention with 5 ml normal saline before catheter insertion reduced the incidence of blood-vessel injury during epidural catheter placement, but adrenaline provided no additional protective effects.

Pediatric regional anesthesia: what is the current safety record?

The use of regional anesthetics, whether as adjuncts, primary anesthetics or postoperative analgesia, is increasingly common in pediatric practice. Data on safety remain limited because of the paucity of very large-scale prospective studies that are necessary to detect low incidence events, although several studies either have been published or have reported preliminary results. This paper will review the data on complications and risk in pediatric regional anesthesia. Information currently available suggests that regional blockade, when performed properly, carries a very low risk of morbidity and mortality in appropriately selected infants and children.

Fifteen years of ultrasound guidance in regional anaesthesia: part 1

Ultrasound guidance for regional anaesthesia has gained enormous popularity in the past decade. The use of ultrasound guidance for many regional anaesthetic techniques is common in daily clinical practice, and the number of practitioners using it is increasing. However, alongside the enthusiasm, there should be a degree of informed scepticism. The widespread use of the various techniques of ultrasound-guided regional blocks without adequate training raises the danger of malpractice and subsequent impaired outcome. Adequate education in the use of regional block techniques under ultrasound guidance is essential. This review article addresses ultrasound guidance for regional anaesthesia, and is divided into two parts because of the size of the topic and the number of issues covered. This first part includes a review and preview of ultrasound guidance in regional anaesthesia and discusses all aspects of ultrasound for regional anaesthesia with a focus on recent technical developments, the positive implications in economics, further potential advantages (e.g. detection of anatomical variants, painless performance of blocks) and education. It also attempts to define a 'gold standard' in regional anaesthesia with the most recent findings in adequate volumes of local anaesthetics for peripheral nerve blocks. This standard should include an extraneural needle position, a high success rate, and wide application of ultrasound guidance in regional anaesthesia. The second part describes the impact of ultrasound on the development of nerve block techniques in the past 5 yr.

Compressed air injection technique to standardize block injection pressures

PURPOSE

Presently, no standardized technique exists to monitor injection pressures during peripheral nerve blocks. Our objective was to determine if a compressed air injection technique, using an in vitro model based on Boyle's law and typical regional anesthesia equipment, could consistently maintain injection pressures below a 1293 mmHg level associated with clinically significant nerve injury.

METHODS

Injection pressures for 20 and 30 mL syringes with various needle sizes (18G, 20G, 21G, 22G, and 24G) were measured in a closed system. A set volume of air was aspirated into a saline-filled syringe and then compressed and maintained at various percentages while pressure was measured. The needle was inserted into the injection port of a pressure sensor, which had attached extension tubing with an injection plug clamped "off". Using linear regression with all data points, the pressure value and 99% confidence interval (CI) at 50% air compression was estimated.

RESULTS

The linearity of Boyle's law was demonstrated with a high correlation, r = 0.99, and a slope of 0.984 (99% CI: 0.967-1.001). The net pressure generated at 50% compression was estimated as 744.8 mmHg, with the 99% CI between 729.6 and 760.0 mmHg. The various syringe/needle combinations had similar results.

CONCLUSION

By creating and maintaining syringe air compression at 50% or less, injection pressures will be substantially below the 1293 mmHg threshold considered to be an associated risk factor for clinically significant nerve injury. This technique may allow simple, real-time and objective monitoring during local anesthetic injections while inherently reducing injection speed.