Michael J. Fredrickson

The utility of continuous perineural infusions for lesser painful shoulder procedures is not well established. We hypothesized that the addition of a continuous interscalene ropivacaine infusion to a single-injection interscalene block would improve analgesia after minor arthroscopic shoulder surgery. An ultrasound-guided interscalene catheter targeting the C5-C6 roots/superior trunk was placed preoperatively in patients undergoing arthroscopic subacromial decompression, excision lateral clavicle, or stabilization. Ropivacaine 0.5% 30 mL was administered via this catheter before surgery was conducted under general anesthesia. All patients received dexamethasone and ondansetron antiemetic prophylaxis. At surgery conclusion, patients were randomly assigned to catheter removal in the postanesthesia care unit ("SS," n = 30) or to an elastomeric infusion of ropivacaine 0.2% 2 mL/hr with patient-controlled 5-mL boluses every hour ("Continuous," n = 31). Multimodal analgesia (acetaminophen, diclofenac, and rescue tramadol) was administered in both groups. Patients were questioned on postoperative days 1 and 2 for numerical rating pain score (0-10), supplemental tramadol consumption, and adverse effects of treatment. Median (quartiles) worst numerical rating pain score was lower in the Continuous group on day 1 on movement (SS = 4 [3-6], Continuous = 2 [0-4], P = 0.008) and at rest (SS = 2 [2-5], Continuous = 1 [0-3], P = 0.007) but was similar between groups on day 2. Median (quartiles) tramadol tablet consumption was lower in the Continuous group on both day 1 (SS = 1 [0-2], Continuous = 0 [0-0], P < 0.001) and day 2 (SS = 1 [0-2], Continuous = 0 [0-1], P = 0.017). Adverse effects of treatment were similar between groups except for numerically rated arm numbness, which was higher for the Continuous group. One patient in the SS group required 2 nights of hospitalization for intravenous opioid. After minor arthroscopic shoulder surgery, the addition of a continuous interscalene ropivacaine infusion to a single-shot interscalene block reduces pain, especially with movement, during the first 24 hrs.

Recent reports of painless intraneural injection of low volumes of local anesthetic without subsequent neurological deficit have led to the suggestion that deliberate subepineural injection may be a safe and therefore acceptable practice. This report describes a case where a venous cannulation needle inadvertently penetrated a patient’s median nerve. Sudden onset severe lancinating pain occurred in the median nerve sensory distribution. A subsequent thorough ultrasound examination showed the median nerve to be located immediately posterior to the targeted median cubital vein. New onset sensory symptoms (numbness, tingling, pain, and altered sensation to touch) in the distribution of the penetrated median nerve persisted for >6 weeks. This report highlights the hazards of intraneural needle placement irrespective of an associated injection. Des comptes-rendus récents rapportant une injection intraneurale indolore de faibles volumes d’anesthésique local sans déficit neurologique subséquent nous ont mené à l’hypothèse qu’une injection sous l’épinèvre pourrait constituer une pratique sécuritaire, donc acceptable. Ce compte-rendu décrit la situation suivante : une aiguille de canulation veineuse a pénétré par inadvertance le nerf médian d’un patient. Une douleur lancinante sévère et soudaine est apparue dans la distribution sensorielle du nerf médian. Par la suite, nous avons réalisé un examen approfondi par ultrason qui a révélé que le nerf médian se situait immédiatement derrière la veine cubitale médiane visée. De nouveaux symptômes sensoriels (engourdissement, picotement, douleur, et sensation altérée au toucher) ont persisté dans la distribution du nerf médian pénétré durant > 6 semaines. Ce compte-rendu démontre les risques d’un placement intraneural d’aiguille indépendamment d’une injection associée.

In this prospective, randomized, triple-blinded study, we tested the hypothesis that a 48 h continuous C5–6 root/superior trunk patient-controlled infusion of ropivacaine 0.4% would provide superior analgesia after shoulder surgery compared with the same infusion of ropivacaine 0.2%. Patients presenting for painful shoulder surgery were recruited. A perineural catheter was placed under ultrasound guidance immediately adjacent to the C5–6 roots/superior trunk. Ropivacaine 5 mg ml⁻¹ (30 ml) was administered via this catheter before surgery under general anaesthesia. At the end of surgery, patients were randomized to receive ropivacaine 2 mg ml⁻¹ (0.2%) (n=32) or 4 mg ml⁻¹ (0.4%) (n=33) via an elastomeric pump delivering 2 ml h⁻¹ with on-demand patient-controlled boluses of 5 ml as required. Acetaminophen and diclofenac were administered if any postoperative pain occurred, ropivacaine boluses for a numerical rating pain score (NRPS, 0–10) of >2, and rescue tramadol for an NRPS >3. All patients were phoned on postoperative days 1 and 2 and questioned for indices of treatment effectiveness and adverse effects. NRPS, patient ropivacaine demands, and supplemental tramadol consumption were similar in each group [median ‘average daily pain’ days 1/2 (0.2%=1/3, 0.4%=2/3)]. Episodes of an insensate/densely blocked arm occurred only with ropivacaine 0.4% (5 vs 0 episodes, P=0.05). Satisfaction (numerical rating scale, 0–10) was higher for ropivacaine 0.2% [mean difference (95% confidence interval)=1.3 (0.3–2.4), P=0.01)]. After major shoulder surgery, ropivacaine 0.2% at 2 ml h⁻¹ with on-demand 5 ml boluses administered via an ultrasound-guided C5–6 root/superior trunk perineural catheter produces similar analgesia, but higher patient satisfaction compared with ropivacaine 0.4%. Trial Registration: ANZCTR: ACTRN12608000591358. URL: www.anzctr.org.au/registry/trial_review.aspx?ID=83028.

Summary: Little data exists regarding the frequency of neurological complications following ultrasound guided peripheral nerve blockade. Therefore, we studied single injection and continuous ultrasound guided interscalene, supraclavicular, infraclavicular, femoral and sciatic nerve blocks in patients undergoing orthopaedic extremity surgery. All patients were contacted during postoperative weeks 2–4 and questioned for numbness or altered sensation anywhere in the involved extremity, and pain or weakness unrelated to surgery. The presumed aetiology of symptoms was based on the collective agreement of principal investigator, primary surgeon and a neurologist. Multivariate analysis was performed for characteristics potentially important in the causation of neurological complications. Of 1010 consecutive blocks, successful follow up between weeks 2 and 4 occurred in 98.6%. New, all‐cause, neurological symptoms were present in 56/690 blocks (8.2%) at day 10, 37/1010 (3.7%) at 1 month and 6/1010 (0.6%) at 6 months. Most symptoms were due to causes unrelated to the block. Of 452 patients directly questioned at the time of the block, new neurological symptoms were more common in patients who experienced procedure‐induced paraesthesia (odds ratio = 1.7, p = 0.029). The postoperative neurological symptom rate in this series is very similar to those previously reported following traditional techniques.

Summary: This prospective, randomised, observer blinded study compared the onset time of brachial plexus block using 2% lidocaine 25–30 ml with adrenaline 5 μg.ml ⁻¹ into the ‘corner pocket’ inferolateral/lateral to the subclavian artery (supraclavicular, n = 30) or to a triple point injection around the axillary artery (infraclavicular, n = 30). Mean (SD) onset time for complete pinprick sensory blockade assessed by a blinded observer in all four distal nerves was similar in both groups: supraclavicular = 22 (9.4) min, infraclavicular = 21 (7.1) min, p = 0.59. Complete sensory blockade in all four nerve territories at 30 min was achieved in 57% in group supraclavicular and 70% in group infraclavicular (p = 0.28). Painless surgery without the requirement for block supplementation was higher in group infraclavicular (28/30, 93%) compared with group supraclavicular (19/30, 67%; p = 0.01). Of the 11 failures in group supraclavicular, nine were due to incomplete ulnar nerve territory anaesthesia. These results do not support the concept of rapid onset successful supraclavicular block via a simple ultrasound‐guided local anaesthetic injection inferolateral to the subclavian artery.

Summary: Ambulatory local anaesthetic delivery systems are often limited by a short effective duration of infusion. Prolonging nerve blockade by substituting a new pump as recommended by the manufacturers, represents a substantial consumable item cost ($US300–500). We therefore evaluated the flow delivery performance of 31 single model elastomeric devices (all with a 2 ml.h ⁻¹ background and 5 ml every hour bolus capability) that had been filled, used in clinical practice and then refilled in the laboratory. For the second infusion, there was a pattern of over‐infusion (< 10 ml.h ⁻¹ ) in the first hour; however, all pumps depreciated to < 150% of predicted by the second hour. The subsequent performance of all pumps was not only within safe limits, but also predominantly within the range (background infusion ± 15%, bolus +10/−20%) specified by the manufacturer for primary infusion. We conclude that this elastomeric regional anaesthesia pump design performs satisfactorily after having been refilled following a single previous use.

Neurostimulation during single shot interscalene block has a significant false negative motor response rate. Compared with tangential needle approaches for single shot block, interscalene catheter (ISC) placement commonly involves Tuohy needles inserted longitudinally to the brachial plexus. This study aimed to determine the sensitivity of neurostimulation during ultrasound-guided ISC needle placement, and the feasibility of an ultrasound-guided ISC needle endpoint. One hundred fifty-five consecutive nonstimulating ISCs were placed with the needle tip position confirmed by the sonographic spread of 5 mL dextrose 5%. Catheter advancement was then blind 2 to 3 cm past the needle tip. A 0.8 mA electrical stimulus at 2 Hz was applied throughout. When a satisfactory image was obtained, neurostimulation was ignored and the minimum motor response amplitude noted. If imaging was equivocal, a brief appropriate motor response at 0.8 mA was sought. A sustained response at <0.5 mA was only sought if imaging was suboptimal. Prior to surgery conducted under general anesthesia, 30 mL ropivacaine 0.5% was administered through the ISC. Catheter success was defined as a recovery room numerical rating pain score of ≤2 (scale, 0-10). In 57% of patients, a muscle response was not elicited. An ultrasound needle endpoint was used in 92% of ISC placements, of which 96% were successful. Sustained twitches at <0.5 mA were obtained in 12 (8%) patients, 6 (4%) of these deliberately sought because of suboptimal imaging. Catheter success overall was 95%. This study suggests that the false negative motor response rate for longitudinal ISC needle placement is higher than the false negative response rate associated with tangential needle approach interscalene block. An ultrasound guided ISC needle endpoint is a feasible alternative to a neurostimulation endpoint.

Large prospective studies evaluating continuous interscalene block for shoulder surgery have thus far been limited to inpatient and university teaching practices. Shoulder surgery is increasingly being performed on an outpatient basis. The aim of this case series was to prospectively evaluate a large series of interscalene catheters for ambulatory shoulder surgery in a private practice setting. A single operator placed nonstimulating catheters using a combination of ultrasound and nerve stimulation. Following postanesthesia care unit (PACU) discharge, opioid-like analgesic adjuvants other than tramadol were avoided unless patients experienced inadequate pain relief. All patients were assessed in the PACU, on the first postoperative morning, and at 3 weeks for catheter effectiveness and for acute and chronic complications. Pain scores and patient satisfaction were assessed in subgroups of 100 consecutive patients. Three hundred patients were studied. The first attempt catheter success rate was 96%. In all but 1 patient, ineffective catheters in the PACU were effectively reinserted. Thirteen patients experienced inadequate pain relief after leaving the PACU. Of these patients, 5 were rescued with additional ropivacaine, 3 had the catheter effectively reinserted, and 5 were managed with oral opioids. One patient required antibiotic treatment for catheter site infection. Neurological sequelae potentially attributable to the catheter were present in 3 patients at 3 weeks, and remained in 1 patient at 4 weeks. This patient's symptoms resolved at 6 months. Continuous interscalene block for ambulatory shoulder surgery in a private practice setting had a high success rate, a low complication rate, and enabled the avoidance of the use of potent opioids in 98% of patients.