Karen C. Nielsen

Interscalene brachial plexus block with a continuous catheter insertion system and a disposable infusion pump.

Continuous interscalene brachial plexus blockade traditionally requires a hospital stay for local anesthetic infusion, and achieving consistent catheter insertion may be difficult. Incorporating long-acting pain relief from a continuous peripheral nerve block, with a reliable method of catheter insertion, and a self-contained infusion system would be a valuable asset for short-stay care. We compared the efficacy of single injection interscalene brachial plexus blockade to a continuous peripheral nerve block, with an insulated Tuohy system and a disposable infusion pump. Forty adult patients scheduled for open rotator cuff repair were entered in this randomized, double-blinded, placebo-controlled study. Patients received an interscalene brachial plexus blockade and a continuous peripheral nerve catheter as their primary anesthetic and then, were assigned to receive one of two different postoperative infusions: either 0.2% ropivacaine at 10 mL/h via a disposable infusion pump or normal saline at 10 mL/h via a disposable infusion pump (n = 18–20 per group). Visual analog pain scores and postoperative morphine consumption were measured for 24 h. The ropivacaine group showed less pain than the placebo group (P = 0.0001) between 12 and 24 h after the initial injection of local anesthetic. In addition, initial interscalene blockade was successful in all patients and all redosed catheters were functional after 24 h with the continuous catheter insertion system. We conclude that it is possible to achieve a high rate of successful catheter placement and analgesia by using the continuous catheter insertion system and a disposable infusion pump in the ambulatory setting. This method of analgesia may offer improved pain relief after outpatient rotator cuff repair. Implications This study demonstrates that it is possible to achieve successful interscalene brachial plexus continuous catheter insertion and a high degree of persistent analgesia by using a catheter insertion system and a disposable infusion pump administering 0.2% ropivacaine.

Continuous peripheral nerve block for ambulatory surgery.

Background and Objectives Adenosine is an endogenous compound that may have analgesic effects. Results from clinical trials are not consistent, however, and there is a need for large-scale, randomized, placebocontrolled studies to clarify the role of adenosine in the treatment of pain states, including acute nociceptive pain and pain involving central sensitization. Methods The analgesic and antihyperalgesic effect of systemic adenosine on the heat/capsaicin sensitization model of experimental pain was investigated in 25 healthy human volunteers. Sensitization was produced by heating the skin to 45°C for 5 minutes, followed by a 30-minute application of 0.075% capsaicin cream, and maintained by periodically reheating the sensitized skin to 40°C for 5 minutes at 40-minute intervals. Subjects received intravenous adenosine 60 μg/kg/min or saline for 85 minutes. Areas of secondary hyperalgesia to von Frey hair and brush stimulation, heat-pain detection thresholds (HPDTs) in normal and sensitized skin, and painfulness of stimulation with 45°C for 1 minute (LTS) in normal skin were quantified before, during, and after study drug infusion. Results Systemic adenosine had no effect on the area of secondary hyperalgesia to von Frey hair or brush stimulation, HPDT in normal or sensitized skin, or painfulness of LTS in normal skin. Conclusion We conclude that adenosine has no effect on acute nociceptive pain induced by heat stimulation or on secondary hyperalgesia induced by heat/capsaicin sensitization in healthy volunteers.

Ambulatory discharge after long-acting peripheral nerve blockade: 2382 blocks with ropivacaine.

Discharging patients with a long-acting peripheral nerve block remains controversial. Concerns about accidental injury of the limb or surgical site because of an insensate extremity are common despite a lack of data on the subject. We report a study examining the efficacy and complications of discharge after long-acting block. This prospective study included 1791 patients receiving an upper or lower extremity nerve block with 0.5% ropivacaine and discharged the day of surgery. Efficacy (conversion to general anesthesia and opioid use), persistent motor or sensory weakness, complications, satisfaction, and unscheduled health care visits were assessed in the postanesthesia care unit (PACU) and at 24 h and 7 days postoperatively using a detailed questionnaire. There were 2382 blocks placed: 1119 upper extremity blocks and 1263 lower extremity blocks. Efficacy was demonstrated by a small conversion to general anesthesia (1%–6%) and a lack of patients requiring opioids in the PACU (89%–92%). A large percentage of patients continued to use opioids at 7 days (17%-22%). Despite the requirement for opioids, satisfaction with the anesthesia experience was high at 24 h and 7 days (Liekert scale [1–5] mean at 24 h, 4.88 ± 0.44; mean at 7 days, 4.77 ± 0.69) and most (98%) would choose the same anesthetic again. Thirty-seven patients (1.6%) were identified with symptoms or complaints at 7 days. After review, 6 of them (0.25%) had a persistent paresthesia that may have been related to the block or discharge. We conclude that long-acting peripheral nerve blockade may be safely used in the ambulatory setting with a high degree of efficacy, safety, and satisfaction. This technique is associated with an infrequent incidence of neurologic complications and injuries. Given the frequent incidence of persistent pain at 7 days, prolongation of the analgesia would be beneficial.

Influence of Obesity on Surgical Regional Anesthesia in the Ambulatory Setting: An Analysis of 9,038 Blocks

Background: Regional anesthesia is increasing in popularity for ambulatory surgical procedures. Concomitantly, the prevalence of obesity in the United States population is increasing. The objective of the present investigation was to assess the impact of body mass index (BMI) on patient outcomes after ambulatory regional anesthesia. Methods: This study was based on prospectively collected data including 9,038 blocks performed on 6,920 patients in a single ambulatory surgery center. Patients were categorized into three groups according to their BMI (<25 kg/m2, 25–29 kg/m2, ≥30 kg/m2). Block efficacy, rate of acute complications, postoperative pain (at rest and with movement), postoperative nausea and vomiting, rate of unscheduled hospital admissions, and overall patient satisfaction were assessed. Linear and logistic multivariable analyses were used to obtain the risk-adjusted effect of BMI on these outcomes. Results: Of all patients 34.8% had a BMI <25 kg/m2, 34.0% were overweight (BMI 25–29 kg/m2), and 31.3% were obese (BMI ≥ 30 kg/m2). Patients with BMI ≥30 kg/m2 were 1.62 times more likely to have a failed block (P = 0.04). The unadjusted rate of acute complications was higher in obese patients (P = 0.001). However, when compared with patients with a normal BMI, postoperative pain at rest, unanticipated admissions, and overall satisfaction were similar in overweight and obese patients. Conclusions: The present investigation shows that obesity is associated with higher block failure and complication rates in surgical regional anesthesia in the ambulatory setting. Nonetheless, the rate of successful blocks and overall satisfaction remained high in patients with increased BMI. Therefore, overweight and obese patients should not be excluded from regional anesthesia procedures in the ambulatory setting.

Peripheral nerve block techniques for ambulatory surgery

Peripheral nerve blocks (PNBs) have an increasingly important role in ambulatory anesthesia and have many characteristics of the ideal outpatient anesthetic: surgical anesthesia, prolonged postoperative analgesia, and facilitated discharge. Critically evaluating the potential benefits and supporting evidence is essential to appropriate technique selection. When PNBs are used for upper extremity procedures, there is consistent opioid sparing and fewer treatment-related side effects when compared with general anesthesia. This has been demonstrated in the immediate perioperative period but has not been extensively investigated after discharge. Lower extremity PNBs are particularly useful for procedures resulting in greater tissue trauma when the benefits of dense analgesia appear to be magnified, as evidenced by less hospital readmission. The majority of current studies do not support the concept that a patient will have difficulty coping with pain when their block resolves at home. Initial investigations of outpatient continuous peripheral nerve blocks demonstrate analgesic potential beyond that obtained with single-injection blocks and offer promise for extending the duration of postoperative analgesia. The encouraging results of these studies will have to be balanced with the resources needed to safely manage catheters at home. Despite supportive data for ambulatory PNBs, most studies have been either case series or relatively small prospective trials, with a narrow focus on analgesia, opioids, and immediate side effects. Ultimately, having larger prospective data with a broader focus on outcome benefits would be more persuasive for anesthesiologists to perform procedures that are still viewed by many as technically challenging.

Peripheral Nerve Blockade with Long-acting Local Anesthetics: A Survey of The Society for Ambulatory Anesthesia

Despite the growth of ambulatory anesthesia and the renewed popularity of regional techniques, there is little current information concerning outpatient regional anesthesia practices or attitudes about discharge with an insensate extremity. We present results from a survey sent to all members of the Society for Ambulatory Anesthesia (SAMBA). The survey was mailed in January 2001 to 2373 SAMBA members, along with a self-addressed stamped return envelope. After 3 mo, 1078 surveys were returned (response rate 45%). Respondents indicated that they were most likely to perform axillary (77%), interscalene (67%), and ankle blocks (68%) on ambulatory patients. They were less likely to perform lower extremity conduction blocks in ambulatory patients (femoral blocks, 40%; all other types of blocks, <23%]. Eighty-five percent of respondents discharged patients with long-acting blocks, but this was mainly limited to three types. Of the 16% who never or rarely discharged patients with long-acting blocks, the primary reasons were concern about patient injury (49%) and the inability for patients to care for themselves (28%). Only 22% of office-based anesthesiologists would perform upper extremity blocks and only 28% would perform lower extremity blocks (P < 0.001). This survey demonstrates that use of regional anesthesia in outpatients is common but restricted to a few techniques. Discharge with an insensate upper extremity is prevalent but discharge with an insensate lower extremity is not common and remains controversial. Despite the reasoning for the reported practices, randomized data are necessary to confirm the validity of these concerns.

Interscalene brachial plexus block with continuous intraarticular infusion of ropivacaine.

Providing intraarticular analgesia with a continuous infusion of local anesthetic via a disposable infusion pump has gained popularity. Despite the prevalence of this technique, data comparing this method of analgesia to conventional regional anesthesia are not available. We present a prospective study that compared a single-dose interscalene block with a single-dose interscalene block plus continuous intraarticular infusion of local anesthetic. Forty patients scheduled for shoulder arthroscopy were entered in this prospective, double-blinded study. All patients received an interscalene brachial plexus block as their primary anesthetic. Patients were randomly assigned to 1 of 2 groups: 1. interscalene block with 1.5% mepivacaine (40 mL) followed by a postoperative intraarticular infusion of 0.5% ropivacaine at 2 mL/h, or 2. interscalene block with 0.5% ropivacaine (40 mL) followed by a postoperative intraarticular infusion of 0.9% saline (placebo) at 2 mL/h. Postoperative infusions were maintained for 48 h. Visual analog scale pain scores and postoperative oxycodone consumption were measured for 48 h. Visual analog scale scores at rest and with ambulation in the Mepivacaine/Intraarticular Ropivacaine group were reduced when compared with the Ropivacaine/Saline group (rest:P = 0.003, ambulation:P = 0.006). Oxycodone consumption was also decreased (28 ± 21 mg vs 44 ± 28 mg, P = 0.046), respectively. We conclude that a brachial plexus block with 1.5% mepivacaine and a continuous intraarticular infusion of 0.5% ropivacaine at 2 mL/h provides improved analgesia for minor surgery at 24 and 48 h versus a single-injection interscalene block with 0.5% ropivacaine.

Increased body mass index and ASA physical status IV are risk factors for block failure in ambulatory surgery — an analysis of 9,342 blocks

PurposeRegional anesthesia can be the technique of choice for selected ambulatory surgery procedures, but in spite of its benefits, it has an inherent failure rate even in experienced hands. We examine the efficacy and factors associated with failure of ambulatory regional anesthesia techniques.MethodsThis study included 9,342 blocks performed on 7,160 patients at the Duke University Ambulatory Surgery Center. Blocks were classified as interscalene, supraclavicular, axillary, lumbar plexus, femoral, sciatic, ankle, paravertebral, spinal, and other (frequency less than 100). A block was considered surgical if a single attempt at placing the block resulted in a complete sensory, motor, and sympathetic nerve block. Multiple logistic regression analyses were used to assess the risk-adjusted association between patient characteristics and block failure.ResultsParavertebral blocks and those considered in the “other” category had significantly higher failure rates (P < 0.001 ), while spinal and lumbar plexus blocks had lower than average rates of failure (P < 0.001 andP = 0.03, respectively). In multiple logistic regression analyses excluding paravertebral blocks, body mass index (BMI) scores greater than 25 (P values: BMI 25–29: < 0.001; BMI 30–34:P < 0.001; BMI 35:P < 0.001) and ASA physical status IV (P < 0.001 ) were significantly associated with higher block failure rates.ConclusionHigh BMI and ASA IV are independent risk factors for block failure in ambulatory surgery patients.RésuméObjectifL’anesthésie régionale peut être la technique de choix pour certaines interventions chirurgicales ambulatoires, mais en dépit de ses avantages, elle présente un taux d’échec inhérent même entre des mains expertes. Nous vérifions l’efficacité des techniques d’anesthésie régionale ambulatoire et les facteurs associés à son échec.MéthodeNotre étude comprend 9 342 blocs réalisés sur 7 160 patients au Duke University Ambulatory Surgery Center. Les blocs ont été classifiés comme interscalène, supraclaviculaire, axillaire, du plexus lombaire, fémoral, sciatique, de la cheville, paravertébral, rachidien et autre (d’une fréquence de moins de 100). Un bloc était considéré chirurgical si un seul essai provoquait un blocage nerveux sensitif, moteur et sympathique. Des analyses de régression logistique multifactorielle ont servi à évaluer l’association ajustée au risque entre les caractéristiques du patient et l’échec du bloc.RésultatsLes blocs paravertébraux et ceux de la catégorie «autre» avaient un taux d’échec significativement plus élevé (P < 0,001), tandis que les blocs rachidiens et ceux du plexus lombaire avaient un taux d’échec sous la moyenne (P < 0,001 etP = 0,03, respectivement). Dans les analyses de régression logistique excluant les blocs paravertébraux, les indices de masse corporelle (IMC) de plus de 25 (IMC de 25–29:P < 0,001; IMC de 30–34:P < 0,001; IMC de 35:P < 0,001) et un état physique ASA N (P < 0,001) étaient significativement associés à des taux d’échec de bloc plus élevés.ConclusionUn IMC élevé et un état physique ASA IV sont des facteurs de risque indépendants d’échec du bloc en chirurgie ambulatoire.

Paravertebral somatic nerve block compared with peripheral nerve blocks for outpatient inguinal herniorrhaphy.

Background Inguinal herniorrhaphy (IH) is a common outpatient procedure, yet postoperative pain and anesthetic side effects remain a problem. Paravertebral somatic nerve blocks (PVB) have the potential to offer unilateral abdominal wall anesthesia and long-lasting pain relief with minimal side effects. We compared PVB with peripheral neural blocks for outpatient IH. Methods Forty-six patients scheduled for IH were entered into this prospective, single-blind study. All patients underwent a standardized general anesthetic. Patients were randomly assigned to receive a PVB (levels T10-L2) preoperatively (n = 24) or an intraoperative peripheral block (PB) by the surgeon (n = 22), using 0.5% ropivacaine (40 mL). Opioid use, verbal analog pain scores, and side effects were documented for 72 hours. Results The use of opioids during surgery was less for the PVB group 162 ± 70 mg than the PB group, 210 ± 60 (P = .02). Need for opioids in PACU was less for the PVB group (39%) than the PB group (61%) (P = .002). Time until first pain after discharge was not different between groups, 312 ± 446 minutes (PB) and 425 ± 384 minutes (PVB) (P = .12). Of the PVB patients, 29% used no opioids at all compared with 18% of PB patients (P = .12). Mean time until first oxycodone use was similar between groups, 303 ± 469 minutes (PB) and 295 ± 225 minutes (PVB) (P = .18). Oxycodone use was also similar; 35 ± 34 mg (PVB) versus 49 ± 42 mg (PB) (P = .30). More patients in the PB group (50%) required antiemetic treatment in the postanesthesia care unit than the PVB group (21%) (P < .001). Side effects were similar at all other measurements. Conclusions This study shows that PVB provides analgesia equivalent to extensive peripheral nerve block for inguinal herniorrhaphy, offering an alternative method of postoperative pain management and perhaps fewer side effects.

Successful resuscitation after ropivacaine-induced ventricular fibrillation.

Human data about resuscitation after cardiac arrest from ropivacaine are limited. We present a case of successful cardiopulmonary resuscitation after accidental ropivacaine-induced ventricular fibrillation. A 76-yr-old female patient presented for foot osteotomy. A femoral block was performed using a nerve stimulator, a short bevel needle and 20 mL of 1.5% mepivacaine with 1:400,000 epinephrine. The patient remained relaxed and conversant. Five minutes later, an anterior sciatic block was done with 0.5% ropivacaine with 1:400,000 epinephrine for prolonged analgesia. Despite a negative aspiration and incremental injection, the patient developed a tonic-clonic seizure, then gradual widening of the QRS complex, and subsequently ventricular fibrillation. The patient was resuscitated with chest compressions and airway support prior to pharmacologic treatment of defibrillation. Total venous ropivacaine concentration 5 min after the last injection was 3.2 mg/L, free ropivacaine was 0.5 mg/L, and total mepivacaine was 0.22 mg/L. The patient was admitted to the hospital and discharged the next morning without complications. This case demonstrates that techniques used to detect intravascular injection may reduce but not eliminate catastrophic events. Consequently, regional anesthesia using large amounts of local anesthetic should be done in locations with resuscitation equipment and by individuals trained to recognize these complications and begin early treatment.