Daryl S. Henshaw

Ultrasound‐Guided Continuous Superficial Peroneal Nerve Block below the Knee for the Treatment of Nerve Injury

(CRPS) describes a constellation of symptoms including pain, trophic changes, hyperesthesia, allodynia, and dysregulation of local blood flow often following trauma. It is often confined to the extremities. Treatment of this disorder consists of a variety of modalities including systemic pharmacotherapy, local anesthetic injections or infusions, psychological nonpharmacotherapy, physical rehabilitation, and surgical intervention. Chronic pain not related to CRPS can also be treated with similar interventions. Despite the array of available therapies, it can still be difficult to manage. We report a case of a 19‐year‐old patient diagnosed by her surgeon as having CRPS Type II, secondary to foot trauma, which was treated with a continuous infusion of local anesthetic at the superficial peroneal nerve (SPN). While placement of peripheral nerve block catheters to augment chronic pain therapy is not novel, the application of a perineural catheter at the SPN has not been previously described.

The use of anatomical position for regional block description.

To the Editor: We read with great interest the recent publication by Duma et al on nitrous oxide analgesic effect. In this post hoc analysis, they compared the early postsurgical opioid consumption and pain in patients receivingN2O (n = 353) with those who did not receive N2O (n = 89) during general anesthesia. They found no difference between the 2 groups either in pain intensity or equianalgesic morphine dosage throughout the postoperative postanesthesia care unit period. Although this finding might contradict certain laboratory works on Fischer rats, the lack of nitrous oxide– induced preemptive analgesic efficacy correlates well with our earlier studies in Sprague-Dawley rats receiving formalin injection. The formalin test consists of an early nociceptive phase (0–5 minutes) and the late spinal sensitization phase (10–60minutes). We administered pure oxygen (negative control), 75% nitrous oxide (0.5 MAC), 2% halothane (1 MAC), and 75% nitrous oxide with 2% halothane (1.5 MAC) during the early phase. Regardless of the gas in use, we found no difference in behavioral responses during the late phase (20–60 minutes) and the extent of c-fos expression in the spinal cord dorsal horn. In a subsequent study, rats were placed in an anesthetic chamber maintained with equianesthetic concentration (0.5 MAC) of N2O (75%) and halothane (0.5%) throughout the early and late phases. N2O and halothane increased the thermal nociceptive threshold, suppressed licking/biting behavior in both early and late phases of the formalin test but failed to suppress c-fos expression. Unlike fentanyl, 75% N2O was unable to suppress the spinal sensitization despite the apparent attenuation in behavioral hyperalgesic responses. Given these findings, we suggest that subanesthetic concentrations of inhalation anesthetic agents, both N2O and halothane, suppress the early and late phase behavioral response because of anesthetic but not analgesic effects.

Transversus abdominis plane block as the primary anesthetic for peritoneal dialysis catheter surgery.

STUDY OBJECTIVE The primary goal of this study was to determine whether transversus abdominis plane (TAP) blocks were effective as the primary anesthetic technique for insertion and/or removal of peritoneal dialysis catheters. DESIGN This study is a descriptive case series investigation. SETTING Operating rooms at a tertiary care academic medical center. PATIENTS Twenty-four patients, American Society of Anesthesiologists (ASA) physical status 3 and 4, were included in this study. INTERVENTIONS Patients who had received a TAP block preoperatively for open surgical insertion or removal of a peritoneal dialysis catheter over a 26-month period with the intent of the block to serve as the primary anesthetic were included in this study. MEASUREMENTS Preoperative and intraoperative sedative medications and local anesthetic medications were analyzed. The primary outcome of the study was the ability of the TAP block to provide surgical anesthesia as determined by a lack of need to convert to general anesthesia (defined by placement of an airway device, use of volatile anesthetics, intraoperative propofol infusion dose equal to or greater than 100 μg kg(-1) min(-1)). Secondary outcomes included analysis of any complications from the higher concentrations of local anesthetics required for surgical block. MANI RESULTS Of 24 patients, 21 underwent the procedure without conversion to general anesthesia as defined above. No complications related to local anesthetics were found. CONCLUSION Transversus abdominis plane blockade can be successful at serving as the primary anesthetic modality for the insertion and/or removal of a peritoneal dialysis catheter by open-surgical approach. There were no systemic toxic effects or other complications recorded.

Ultrasound-Guided Continuous Superficial Radial Nerve Block for Complex Regional Pain Syndrome

ABSTRACT Although there are many potentially effective therapeutic options for complex regional pain syndrome (CRPS), no definitive treatment exists. Therefore, patients often exhaust both medical and surgical treatment options attempting to find relief for their symptoms. As pain control and restoration of physical movement are primary treatment goals, strategies that include regional anesthesia techniques are commonly employed, but potentially underutilized, treatment modalities. The authors present a patient with refractory CRPS that had significant improvement in both pain control and the ability to tolerate intensive physical therapy following the placement of a superficial radial nerve catheter and an infusion of local anesthetic for 6 days as part of a multimodal analgesic regimen. This treatment approach also assisted in the decision-making process related to future treatment options. Although the use of regional anesthesia and perineural infusions of local anesthetic have previously been described as viable treatment options for CRPS, this case report represents the first known use of a superficial radial nerve catheter for treating CRPS as well as the first description of a technique for placing a superficial radial nerve (SRN) catheter using ultrasound guidance.

An Evaluation of Ultrasound-Guided Adductor Canal Blockade for Postoperative Analgesia After Medial Unicondylar Knee Arthroplasty.

BACKGROUND:Unicondylar knee arthroplasty (UKA) is a commonly performed procedure with significant expected postoperative pain. Peripheral nerve blocks are 1 analgesic option, but some approaches may decrease quadriceps motor strength and interfere with early ambulation. In this study, we compared the analgesia provided by an adductor canal block (ACB) and a psoas compartment block (PCB) after UKA. We hypothesized that the ACB would provide equivalent analgesia, defined as a difference of <2 points on the pain scale (0–10 numeric rating scale [NRS]), at rest and with movement 6 hours after block placement. METHODS:One hundred fifty patients undergoing medial UKA were randomly assigned to receive either an ACB or a PCB with 0.25% bupivacaine, 5 &mgr;g/mL epinephrine, and 1.67 &mgr;g/mL clonidine. All patients received multimodal analgesics, sham blockade at the alternate site, and a posterior capsule injection during surgery. Patients and observers were blinded to treatment groups. The primary end points were NRS pain scores with rest and movement at 6 hours. Secondary end points included quadriceps muscle strength at 6 hours (0–5 [5 being full strength]; Medical Research Council scale) as well as NRS pain scores, opioid consumption, and opioid-related side effects over 24 hours. RESULTS:One hundred forty-seven patients were analyzed. Pain scores were equivalent at 6 hours with rest (ACB 1.0 ± 2 vs PCB 1.1 ± 2.2 [mean NRS ± SD]; 95% confidence interval of mean difference, −0.8 to 0.6; P < 0.0001) and with movement (ACB 1.6 ± 2.6 vs PCB 1.5 ± 2.8; 95% confidence interval of mean difference, −0.8 to 0.9; P < 0.0001). In addition, pain scores at rest and with movement at 12, 18, and 24 hours were equivalent. Quadriceps motor strength was significantly increased in the ACB group (Medical Research Council scale score, 4.0 ± 1.1 vs 2.5 ± 1.3 [mean ± SD]; P < 0.0001). No significant differences were found between groups for time to first analgesic or for cumulative opioid consumption at 6, 12, 18, or 24 hours. Other than an increase in the incidence of pruritus in the ACB group at 6 hours, there were no differences in opioid-related side effects. CONCLUSIONS:An ACB provides equivalent analgesia after medial UKA when compared with a PCB. In addition, the ACB caused significantly less motor weakness. An ACB should be considered for postoperative analgesia after medial UKA.

Intravenous dexamethasone fails to prolong psoas compartment block when assessed by objective pinprick sensory testing: a prospective, randomised, dose-dependent, placebo-controlled equivalency trial

Background: Recent studies have concluded that i.v. dexamethasone can prolong the duration of peripheral nerve blockade. We hypothesized that a 4 mg dose would equally prolong the duration of psoas compartment blocks (PCBs) when compared with 8 mg, and that both doses would prolong the duration when compared with placebo. Methods: This was a prospective, randomized, placebo‐controlled, dose‐dependent, equivalency trial with 115 patients undergoing total hip arthroplasty. The patients received a PCB. Subsequently, 15 patients received i.v. normal saline (placebo), 50 patients received i.v. dexamethasone 4 mg, and 50 patients received i.v. dexamethasone 8 mg. The primary outcome was the duration in hours of PCB, determined by serial pinprick assessments. Secondary outcomes included pain scores, time to first analgesic, and opioid consumption. An intention‐to‐treat‐analysis (ITA) and per‐protocol analysis (PPA) were performed. Results: The ITA showed that block duration in the 4 and 8 mg groups was equivalent [mean (standard deviation), 18.5 h (8.0) vs 18.1 h (7.1)]. However, neither group differed from placebo [19.6 h (6.7), (4 mg vs placebo), P=0.97; (8 mg vs placebo), P=0.77)]. Postoperative pain scores and opioid consumption were not different between groups. Time to first analgesic was not different between the 4 and 8 mg groups, or the 4 mg and placebo groups. The 8 mg group, however, had a longer time to first analgesic (median of 533 vs 432 min, P=0.047) when compared with placebo, although the significance was not observed in the PPA (P=0.058). Conclusions: I.V. dexamethasone did not prolong PCB when duration was objectively assessed, or decrease total opioid consumption. However, dexamethasone 8 mg prolonged the time to first analgesic. Clinical trial registration: NCT 02464176.

Perineural dexamethasone successfully prolongs adductor canal block when assessed by objective pinprick sensory testing: A prospective, randomized, dose-dependent, placebo-controlled equivalency trial

STUDY OBJECTIVE To determine whether perineural dexamethasone prolongs peripheral nerve blockade (PNB) when measured objectively; and to determine if a 1 mg and 4 mg dose provide equivalent PNB prolongation compared to PNB without dexamethasone. SETTING Multiple studies have reported that perineural dexamethasone added to local anesthetics (LA) can prolong PNB. However, these studies have relied on subjective end-points to quantify PNB duration. The optimal dose remains unknown. We hypothesized that 1 mg of perineural dexamethasone would be equivalent in prolonging an adductor canal block (ACB) when compared to 4 mg of dexamethasone, and that both doses would be superior to an ACB performed without dexamethasone. DESIGN This was a prospective, randomized, double-blind, placebo-controlled equivalency trial involving 85 patients undergoing a unicompartmental knee arthroplasty. INTERVENTIONS All patients received an ACB with 20 ml of 0.25% bupivacaine with 1:400,000 epinephrine. Twelve patients had 0 mg of dexamethasone (placebo) added to the LA mixture; 36 patients had 1 mg of dexamethasone in the LA; and 37 patients had 4 mg of dexamethasone in the LA. MEASUREMENTS The primary outcome was block duration determined by serial neurologic pinprick examinations. Secondary outcomes included time to first analgesic, serial pain scores, and cumulative opioid consumption. MAIN RESULTS The 1 mg (31.8 ± 10.5 h) and 4 mg (37.9 ± 10 h) groups were not equivalent, TOST [Mean difference (95% CI); 6.1 (-10.5, -2.3)]. Also, the 4 mg group was superior to the 1 mg group (p-value = 0.035), and the placebo group (29.7 ± 6.8 h, p-value = 0.011). There were no differences in opioid consumption or time to analgesic request; however, some pain scores were significantly lower in the dexamethasone groups when compared to placebo. CONCLUSION Dexamethasone 4 mg, but not 1 mg, prolonged the duration of an ACB when measured by serial neurologic pinprick exams. CLINICAL TRIAL REGISTRATION NCT02462148.

Residual Enoxaparin Activity, Anti-Xa Levels, and Concerns About the American Society of Regional Anesthesia and Pain Medicine Anticoagulation Guidelines

Abstract Currently, the American Society of Regional Anesthesia and Pain Medicine (ASRA) anticoagulation guidelines recommend that before the performance of a neuraxial procedure a minimum of 24 hours should elapse following a treatment dose of enoxaparin (1 mg/kg twice daily or 1.5 mg/kg once daily). The guidelines have since their inception also consistently recommended against the routine use of anti-Xa level monitoring for patients receiving enoxaparin. However, we noted in our clinical practice that anti-Xa levels were frequently still elevated despite patients meeting the time-based recommendation for treatment dose enoxaparin. To further investigate the possibility that residual anticoagulant activity may persist longer than 24 hours after a treatment dose of enoxaparin, we assessed anti-Xa level activity in patients presenting for elective surgery. Despite nearly universal compliance with ASRAs anticoagulation guidelines (1 sample was drawn at 23.25 hours), anti-Xa activity was found to be elevated in 11 of 19 patients. While 10 patients had an anti-Xa level within the peak prophylactic range (0.2–0.5 IU/mL), 1 patients level was found to still be in the peak therapeutic range (0.5–1.0 IU/mL). These findings suggest that significant anticoagulant activity may persist longer than previously appreciated after the last treatment dose of enoxaparin and that the current time-based ASRA recommendation may not be conservative enough. Further research is needed to delineate the level of anti-Xa activity below which it is likely safe to proceed with a neuraxial procedure, but it may be time to reconsider the utility of anti-Xa level monitoring when it is available.

Benefits of thoracic epidural analgesia in patients undergoing an open posterior component separation for abdominal herniorrhaphy

ABSTRACT An open posterior component separation (PCS) is a commonly utilized surgical approach for repair of complex abdominal wall defects and hernias. Although this approach may improve surgical outcomes, significant postoperative pain can be expected given the required laparotomy and extensive abdominal wall manipulation. Both systemic opioids and thoracic epidural analgesia (TEA) are viable postoperative analgesic options, and both are commonly utilized. Although the benefits of TEA have been investigated following a variety of surgeries, there is a paucity of literature related to its efficacy for this particular surgery. The aim of this study was to evaluate the benefits of TEA following open PCS under the hypothesis that the incorporation of TEA into the postoperative analgesic regimen would hasten bowel recovery. Patients who previously underwent an open PCS were identified through an electronic medical record query. A retrospective chart review was then performed, and patients who had TEA, either alone or combined with systemic opioids, were compared with patients who had only systemic opioids. The primary end point was a comparison of the postoperative day (POD) on which a full diet was started. Secondarily, time to liquid diet, postsurgical length of stay (LOS), intensive care unit (ICU) admission rate, ICU LOS, and the rates of several postoperative adverse events were compared. A post hoc analysis was also performed, using the same end points, to compare the subgroup of TEA patients who avoided systemic opioids with all patients who received systemic opioids, whether alone or combined with TEA. One hundred and one patients were ultimately included for analysis. Time to full diet was not significantly different between patients who had TEA, either with or without systemic opioids, and those who received only systemic opioids (TEA 2.6 ± 1.7 vs. systemic opioids 3.1 ± 2.1 [mean POD ± SD], P = .21). Additionally, no statistically significant differences were found for any secondary outcome. In the post hoc analysis, the subgroup of TEA patients who avoided systemic opioids had a significantly faster time to bowel recovery when compared with all patients who received systemic opioids (2.2 ± 1.0 vs. 3.2 ± 2.2, P = .0033). This subgroup also had a significantly shorter time to liquid diet and a decreased postoperative LOS. In conclusion, for patients undergoing an open PCS, the inclusion of TEA in the postoperative analgesic regimen did not by itself hasten the return of bowel function. However, when TEA was utilized and systemic opioids were avoided, bowel recovery occurred significantly sooner and resulted in a shortened hospital LOS.