Peripheral nerve stimulation through a 'dry' peripheral nerve catheter for shoulder analgesia: a case report.

Revision shoulder surgery can pose significant analgesic challenges as locoregional blocks are often avoided to enable early recognition of iatrogenic nerve injuries. Our case describes the utilisation of pre-operative and intra-operative low-frequency percutaneous peripheral nerve stimulation via a 'dry' interscalene catheter, inserted pre-operatively for a patient presenting for revision total shoulder arthroplasty who was experiencing significant shoulder joint pain despite a prior total shoulder arthroplasty. The clinical considerations and safety aspects are discussed further.

Pain management using a novel hybrid technique of perineural stimulation combined with regional anaesthesia through a stimulating perineural catheter for below knee amputation.

Pain after amputation can be difficult to manage due to its complex aetiology. A multimodal approach to analgesia, including regional anaesthetic techniques, is advised. However, optimal pain management cannot always be achieved, and high doses of opioid analgesics may contribute to adverse effects. We describe the management of an elderly patient with significant co-morbidities undergoing below knee amputation. Pre-operatively, a popliteal sciatic stimulating perineural catheter and a femoral non-stimulating perineural catheter were placed. When pain control was suboptimal on the first postoperative day, a combination of local anaesthetic and a brief period of peripheral nerve stimulation through the sciatic stimulating perineural catheter was used to augment pain control, thereby avoiding additional opioid use. Although nerve stimulation utilising specialised equipment, such as percutaneous stimulator electrodes, has been previously described in acute pain medicine, we demonstrate the use of a novel hybrid technique which combines nerve stimulation through a perineural catheter and local anaesthetic. Further research is warranted to explore the utility of this neuromodulation technique in clinical practice.

Successful postoperative analgesia with ilio-inguinal nerve block following sclerotherapy for a labial venous malformation.

Though ilio-inguinal nerve block has been commonly utilised in male urologic surgery, a single injection ilio-inguinal nerve block alone has not previously been reported for analgesia of the vulva. In this report, we describe the case of a 14-year-old girl undergoing sclerotherapy of a venous malformation affecting the labia majora and minora. After induction of anaesthesia, we performed an ultrasound-guided ilio-inguinal nerve block using a total volume of 15 ml of ropivacaine 0.2% with 1 µg.ml-1 dexmedetomidine which provided effective postoperative analgesia. Though the patient received intravenous analgesia intra-operatively and had an inpatient bed reserved in anticipation of severe postoperative pain, she required no further analgesia and was discharged home following 2 hours in the postoperative anaesthesia care unit. With the additional use of dexmedetomidine resulting in prolonged efficacy of the block, the patient reported effective postoperative relief for approximately 30 hours, solely using ibuprofen for pain relief. This case reminds clinicians that the ilio-inguinal nerve block may provide benefit not only for male urologic surgery but also for procedures involving the external female genitalia, with extended analgesia with the use of dexmedetomidine.

Sublingual ultrasound as an assessment method for predicting difficult intubation: a pilot study.

Current methods to assess the airway before tracheal intubation are variable in their ability to predict a difficult airway accurately. We hypothesised that sublingual ultrasound could provide additional information to predict a difficult airway with greater success than current methods. We recruited 110 patients to perform sublingual ultrasound on themselves following brief instruction. Ability to view the hyoid bone on sublingual ultrasound, mouth opening distance, thyromental distance, neck mobility, size of mandible and modified Mallampati classification were recorded and assessed for ability to predict a difficult intubation based on the grade of laryngoscope. Visibility of the hyoid using ultrasound was associated with a laryngoscopic grade of 1-2 (p < 0.0001), and (p < 0.0001) had a positive likelihood ratio of 21.6 and a negative likelihood ratio of 0.28. Each of the other methods had considerably lower positive likelihood ratios and lower sensitivity. Our results suggest that sublingual ultrasound is a potential tool for predicting a difficult airway in addition to conventional methods.

The effects of general anaesthesia on nerve-motor response characteristics (rheobase and chronaxie) to peripheral nerve stimulation.

Using a simple surface nerve stimulation system, I examined the effects of general anaesthesia on rheobase (the minimum current required to stimulate nerve activity) and chronaxie (the minimum time for a stimulus twice the rheobase to elicit nerve activity). Nerve stimulation was used to elicit a motor response from the ulnar nerve at varying pulse widths before and after induction of general anaesthesia. Mean (SD) rheobase before and after general anaesthesia was 0.91 (0.37) mA (95% CI 0.77-1.04 mA) and 1.11 (0.53) mA (95% CI 0.92-1.30 mA), respectively. Mean (SD) chronaxie measured before and after general anaesthesia was 0.32 (0.17) ms (95% CI 0.26-0.38 ms) and 0.29 (0.13) ms (95% CI 0.24-0.33 ms), respectively. Under anaesthesia, rheobase values increased by an average of 20% (p = 0.05), but chronaxie values did not change significantly (p = 0.39). These results suggest that threshold currents used for motor response from nerve stimulation under general anaesthesia might be higher than those used in awake patients.

Comparison of blind and electrically guided tracheal needle insertion in human cadavers.

The purpose of this study was to investigate whether an electrically guided needle insertion technique would enable greater success at intratracheal needle tip insertion than the traditional, aspiration-of-air technique. Twenty-seven anaesthesiology residents were assessed in their ability to place a needle tip in the trachea of cadavers using the two methods. Success of needle placement, time to placement and confidence in placement were recorded. Correct intratracheal needle placement was achieved by 22% of residents (6/27) using the aspiration-of-air method vs 82% (22/27) using the electrically guided method (p<0.001). For the instances of success, there was no significant difference between the two methods in the median (IQR [range]) time taken (28 (24-49 [18-63]) s aspiration vs 32 (19-49 [15-84]) s electrical; p=0.93). The electrically guided method provides an acceptably quick and accurate way of placing a needle tip into the tracheal lumen and can be learnt easily by anaesthesiology residents.

Continuous interscalene block: the good, the bad and the refined spread.

Continuous interscalene block is popular for shoulder surgery, but there are several challenges when performing this continuous block. The interscalene catheter is susceptible to incidental dislodgement and migration due to movement of the head and neck. Another important consideration is phrenic nerve involvement; the phrenic nerve is susceptible to being incidentally anaesthetised with local anaesthetic during interscalene block, owing to its close proximity to the interscalene groove. We present two cases: firstly, a case demonstrating an interscalene catheter insertion approach that provides an effective spread of local anaesthetic perineurally within the interscalene groove, with the additional benefit of preventing catheter dislodgement. Secondly, we present a case in which ultrasound-guided interscalene catheter insertion resulted in phrenic nerve palsy in an asthmatic patient, where dilution or 'wash-off' of local anaesthetic with normal saline and repositioning of the catheter under ultrasound guidance resulted in rapid recovery of respiratory function and adequate pain control.

Cervical epidural analgesia via a thoracic approach using nerve-stimulation guidance in adult patients undergoing total shoulder replacement surgery.

BACKGROUND: Continuous cervical epidural anesthesia can provide excellent peri- and post-operative analgesia, although several factors prevent its widespread use. Advancing catheters from thoracic levels to the cervical region may circumvent these barriers, provided they are accurately positioned. We hypothesize that guiding catheters from thoracic to cervical regions using low-current epidural stimulation will have a high success rate and enable excellent analgesia in adults undergoing total shoulder arthroplasty. METHODS: After Institutional Review Board approval, adult patients were studied consecutively. A 17-G Tuohy needle was inserted into the thoracic epidural space using a right paramedian approach with loss of resistance. A 20-G styletted epidural catheter, with an attached nerve stimulator, was primed with saline and a 1-10 mA current was applied as it advanced in a cephalad direction towards the cervical spine. Muscle twitch responses were observed and post-operative X-ray confirmed final placement. After a test dose, an infusion (2-8 ml/h) of ropivacaine 2 mg/ml and morphine 0.05 mg/ml (or equivalent) was initiated. Verbal analog pain scale scores were collected over 72 h. RESULTS: Cervical epidural anesthesia was performed on 10 patients. Average current required to elicit a motor response was 4.8 +/- 2.0mA. Post-operative X-ray of catheter positions confirmed all catheter tips reached the desired region (C4-7). The technical success rate for catheter placement was 100% and excellent pain control was achieved. Catheters were positioned two to the left, four to the right and four to the midline. CONCLUSION: This epidural technique provided highly effective post-operative analgesia in a patient group that traditionally experiences severe post-operative pain and can benefit from early mobilization.

Thoracic epidural catheters via the caudal and lumbar approaches using styletted multiple port catheters in pediatric patients: a report of three cases.

Advancing catheters from the lumbar and caudal epidural spaces to the thoracic level has been reported to be an alternative to the direct thoracic approach. However, as children grow, the threading of catheters in the epidural space becomes increasingly difficult. This report describes three cases of thoracic epidural placement using a multiport catheter threaded from the caudal and lumbar spaces using electrical stimulation guidance. In the first case, a multiport catheter was threaded 22 cm from the lumbar space to T8 following a failed attempt with a single-port catheter in a 9-year-old boy scheduled to undergo a right nephrectomy. In the second case, a multiport catheter was threaded 26 cm from the caudal space to T9 in a 3-year-old girl undergoing fundoplication. In the last case, a multiport catheter was inserted at the completion of a fundoplication in a 2-year-old girl after it had been confirmed that the single-port catheter inserted prior to surgery had not advanced to the desired thoracic level. The multiport catheter was threaded 17 cm without resistance from the caudal space to T9. In all cases, electrical stimulation was used to confirm the location of the catheter tip at the time of insertion. The position of the catheters was later confirmed by X-ray. The multiport catheter incorporates a stylet, which extends to a closed distal tip, within a catheter body that ejects fluid from three lateral holes in a direction perpendicular to the advancing catheter. These properties may facilitate the reliable advancement of catheters in the epidural space.