Christopher B. Robards

Intraneural Injection with Low-Current Stimulation During Popliteal Sciatic Nerve Block

BACKGROUND: Prevention of an intraneural injection of a local anesthetic during peripheral nerve blockade is considered important to avoid neurologic injury. However, the needle-nerve relationship during low-current electrical nerve localization is not well understood. METHODS: We postulated that intraneural needletip location is common during low-current stimulation popliteal sciatic nerve blockade. Twenty-four consecutive ASA class I-III patients scheduled for foot or ankle surgery under popliteal sciatic nerve block using a combined ultrasound and nerve stimulator-guided technique were prospectively studied. The end point for needle advancement was predetermined to be either an elicited motor response between 0.2 and 0.5 mA (100 &mgr;s/2 Hz) or an apparent intraneural location of the needletip as seen on ultrasound, whichever came first. The injection occurred at either end points provided the injection pressure was <20 psi. The injection was considered intraneural when injectate resulted in both the swelling and compartmentalization of the nerve within the epineurium. RESULTS: Elicited motor response could be obtained only upon entry of the needle into the intraneural space in 20 patients (83.3%). In the remaining four patients (16.7%), a motor response with a stimulating current of 1.5 mA could not be obtained even after the needle entry into the intraneural space. An injection in the intraneural space occurred in all patients who had motor-evoked response at current 0.2–0.4 mA. All 24 blocks resulted in adequate anesthesia for foot surgery. No patient developed postoperative neurologic dysfunction. CONCLUSION: The absence of motor response to nerve stimulation during popliteal sciatic nerve block does not exclude intraneural needle placement and may lead to additional unnecessary attempts at nerve localization. Additionally, low-current stimulation was associated with a high frequency of intraneural needle placement.

Real-time three-dimensional ultrasound-assisted axillary plexus block defines soft tissue planes.

Two-dimensional (2D) ultrasound is commonly used for regional block of the axillary brachial plexus. In this technical case report, we described a real-time three-dimensional (3D) ultrasound-guided axillary block. The difference between 2D and 3D ultrasound is similar to the difference between plain radiograph and computer tomography. Unlike 2D ultrasound that captures a planar image, 3D ultrasound technology acquires a 3D volume of information that enables multiple planes of view by manipulating the image without movement of the ultrasound probe. Observation of the brachial plexus in cross-section demonstrated distinct linear hyperechoic tissue structures (loose connective tissue) that initially inhibited the flow of the local anesthesia. After completion of the injection, we were able to visualize the influence of arterial pulsation on the spread of the local anesthesia. Possible advantages of this novel technology over current 2D methods are wider image volume and the capability to manipulate the planes of the image without moving the probe.

Intravascular Injection During Ultrasound-guided Axillary Block: Negative Aspiration Can Be Misleading

Needle visualization is an advantage of ultrasound-guided nerve blocks compared to traditional methods of nerve localization. However, visualization of local anesthetic spread is also important. During an ultrasound-guided axillary block, there was negative aspiration for blood. However, the absence of local anesthetic spread on ultrasound imaging suggested possible intravascular injection. The ultrasound transducer was removed from the patients arm and venous blood was aspirated from the nerve block needle. Pressure applied to an ultrasound transducer can occlude venous structures making negative aspiration of blood unreliable for excluding intravascular needle placement.

Real-time 3-dimensional ultrasound-assisted infraclavicular brachial plexus catheter placement: implications of a new technology.

Background. There are a variety of techniques for targeting placement of an infraclavicular blockade; these include eliciting paresthesias, nerve stimulation, and 2-dimensional (2D) ultrasound (US) guidance. Current 2D US allows direct visualization of a “flat” image of the advancing needle and neurovascular structures but without the ability to extensively analyze multidimensional data and allow for real-time manipulation. Three-dimensional (3D) ultrasonography has gained popularity and usefulness in many clinical specialties such as obstetrics and cardiology. We describe some of the potential clinical applications of 3D US in regional anesthesia. Methods. This case represents an infraclavicular catheter placement facilitated by 3D US, which demonstrates 360-degree spatial relationships of the entire anatomic region. Results. The block needle, peripheral nerve catheter, and local anesthetic diffusion were observed in multiple planes of view without manipulation of the US probe. Conclusion. Advantages of 3D US may include the ability to confirm correct needle and catheter placement prior to the injection of local anesthetic. The spread of local anesthetic along the length of the nerve can be easily observed while manipulating the 3D images in real-time by simply rotating the trackball on the US machine to provide additional information that cannot be identified with 2D US alone.

Case report: continuous interscalene block associated with neck hematoma and postoperative sepsis.

Continuous peripheral nerve blockade is often used for the management of postoperative pain, even in ambulatory patients. The reported incidence of infectious complications after continuous nerve blockade is low. We report a case of Staphylococcus aureus sepsis after total shoulder arthroplasty in a patient who presented to her surgeon 8 days postoperatively with lethargy and labored breathing. Preoperatively, the patient had received a continuous interscalene block for analgesia that was associated with a neck hematoma. After readmission, exploratory laparotomy, and extensive hospital stay, the patient was discharged to an extended care facility in good condition.

Ultrasound-guided transversus abdominis plane blocks for patients undergoing laparoscopic hand-assisted nephrectomy: a randomized, placebo-controlled trial.

Postoperative pain is a common complaint following living kidney donation or tumor resection using the laparoscopic hand-assisted technique. To evaluate the potential analgesic benefit of transversus abdominis plane blocks, we conducted a randomized, double-blind, placebo-controlled study in 21 patients scheduled to undergo elective living-donor nephrectomy or single-sided nephrectomy for tumor. Patients were randomized to receive either 20 mL of 0.5% ropivacaine or 20 mL of 0.9% saline bilaterally to the transversus abdominis plane under ultrasound guidance. We found that transversus abdominis plane blocks reduced overall pain scores at 24 hours, with a trend toward decreased total morphine consumption. Nausea, vomiting, sedation, and time to discharge were not significantly different between the two study groups.

Low interscalene block provides reliable anesthesia for surgery at or about the elbow

STUDY OBJECTIVE To determine whether interscalene brachial plexus block (ISB) provides adequate anesthesia for surgery on or about the elbow. STUDY DESIGN Case series. SETTING Operating room of an academic teaching hospital. PATIENTS 78 patients scheduled for elective elbow surgery. INTERVENTIONS All patients received an ISB using a low approach technique. A stimulating needle was inserted in the interscalene groove two cm above the clavicle. A volume of 35-45 mL of mepivacaine 1.5% or ropivacaine 0.5% was administered after obtaining a motor response of any component of the brachial plexus with a current intensity of 0.2-0.4 mA (0.1 msec). MEASUREMENTS Block success rate, defined as the ability to complete surgery without use of intraoperative opioids or general anesthesia, was assessed. Verbal rating scores for pain (0 = no pain, 10 = worst pain imaginable) were obtained in the recovery room. MAIN RESULTS Low ISB resulted in successful surgical anesthesia in 75 (96%) of the study patients. Verbal rating scores were low (0-2) for all patients postoperatively. CONCLUSIONS The low interscalene block can be used to provide surgical anesthesia in the majority of patients having surgery on or about the elbow.

Opioid consumption in total knee arthroplasty patients: a retrospective comparison of adductor canal and femoral nerve continuous infusions in the presence of a sciatic nerve catheter.

OBJECTIVE To compare opioid consumption among patients who receive a continuous adductor canal block (ACB) versus continuous femoral nerve block (FB) for total knee arthroplasty analgesia in the presence of an intermittent sciatic nerve catheter (iSB). DESIGN Matched cohort retrospective study. SETTING Mayo Clinic, Jacksonville, FL. PATIENTS Ninety patient charts were included in this study: 45 patients with continuous ACB/iSB and 45 with continuous FB/iSB. Patients were matched according to mean preoperative opioid consumption and pain scores, BMI, age, and gender. MEASUREMENTS The primary outcome of the study was postoperative on-demand opioid consumption on postoperative days 0 (POD 0), 1 (POD 1), and 2 (POD 2). Secondary outcomes included postoperative Visual Analog Scale (VAS) scores for anterior and posterior knee pain, incidence of nausea and pruritus, need for intravenous rescue opioid, and need for catheter bolus by a physician. MAIN RESULTS On POD 0, mean opioid consumption in milligrams of oral morphine equivalent [mean±SD (95% CI)] was 43.98mg±33.36 (33.96, 54) in the ACB/iSB group vs 38.45mg±30.99 (29.14, 47.76) in the FB/iSB group, respectively (P=.42); on POD 1, 74.96mg±37.23 (63.78, 86.14) vs 72.40mg±62.34 (53.67, 91.13) (P=.81); on POD 2, 28.19mg±17.69 (22.87, 33.51) vs 31.84mg±23.09 (24.90, 38.78) (P=.40). On POD 1, median anterior knee VAS scores at rest were equivalent in both the ACB/iSB and FB/iSB groups (1 vs 1, respectively, P=.46); however, patients in the ACB/iSB group were more likely to have higher anterior knee pain scores with movement (4 vs 1, P=.002). CONCLUSION In the first 2 days after a total knee arthroplasty, opioid consumption in patients with continuous ACB/iSB was not significantly different from patients receiving continuous FB/iSB. Continuous adductor canal block appears to provide adequate analgesia when compared to continuous femoral blockade.

Tip adhesions complicate infraclavicular catheter removal.

To the Editor, Continuous peripheral nerve blocks (CPNBs) are a versatile tool for ambulatory anesthesia because they can offer both surgical anesthesia as well as prolonged postoperative analgesia. For orthopedic procedures in particular, they reduce the need for general anesthesia and opioids with a decreased incidence of nausea and vomiting. However, there are complications with CPNBs that give rise to concern including migration, kinking, knotting, dislodgement, site infection, and nerve injury. In a previous report, we described additional complications due to shearing in five patients who received continuous nerve blocks with stimulating catheters. Those reported complications suggested a dilemma in placing continuous stimulating perineural catheters on an ambulatory basis, i.e., in each case, a return trip to the hospital was required for removal. In this regard, we report tissue adhesions complicating removal of a stimulating catheter. The authors consulted the institutional Ethics Review Board and obtained approval for publication in the Journal. A 46-yr-old male (American Society of Anesthesiologists physical status II, body mass index 29 kg m) was scheduled for right wrist tumour re-excision and splitthickness skin graft. His medical history was negative except for prior removal of an eccrine tumour on his right wrist. After obtaining the patient’s written consent, an ultrasound-guided infraclavicular CPNB with a 19G StimCath (Arrow International, Reading, PA, USA) was performed for postoperative analgesia. Ropivacaine 0.2% was infused at 5 mL hr with a patient-controlled analgesia dose of 5 mL every hour. The patient was discharged from hospital the following day. It is routine practice at our institution to discontinue the catheter within 72 hr of placement, which is usually the duration of the volume in the local anesthesia reservoir. In this case, the patient called on postoperative day (POD) 4 with a complaint concerning difficulty removing his catheter. He lived two hours distance from our medical centre and did not want the added drive during the weekend to have the catheter removed. Consequently, the attempted removal at home occurred on POD 4 when the infusion device was empty. During the procedure, the white-coloured polyurethane sheath separated from the coiled omni-port stainless steel tip. Ultimately, successful removal the catheter was achieved on POD 6 by applying steady traction on the catheter and using a reverse Seldinger technique. The patient did not complain of paresthesia during the procedure although the catheter tip was enveloped with tissue (Figure); the pathological diagnosis was benign fibrinous tissue. Since the patient was observed overnight prior to discharge and, possibly more important, because he declined to return to the hospital on POD 4 when he encountered difficulty with removal, the catheter remained in place without local anesthetic infusing for approximately 48 hr. This scenario mimics the findings of Buckenmaier et al. where catheters were left in vivo in rats without local anesthetic infusions. While there was a large amount of fibrous tip adhesion found upon catheter removal, it is not known whether it occurred over the course of the almost 48 hr that the local anesthetic was not infusing or whether a portion of it occurred as early as during the continuous infusion. The tip adhesion data from Buckenmaier et al. were collected following seven days of catheter maintenance. Our case suggests that fibrous adhesions may occur R. Duclas Jr, MD (&) C. B. Robards, MD B. L. Ladie, MD S. R. Clendenen, MD Mayo Clinic, Jacksonville, FL, USA e-mail: rduclasjr@gmail.com

Sciatic nerve catheter placement: success with using the Raj approach.

BACKGROUND:Continuous regional analgesia has increased in popularity and is becoming standard of care for many painful surgical procedures. Various approaches of sciatic catheter insertion have been proposed, each with attributes and disadvantages. We investigated whether the Raj approach that uses a simple midpoint landmark between the ischial tuberosity and greater trochanter will facilitate sciatic catheter placement. METHODS:After informed consent, 20 patients were recruited to receive sciatic catheter placement using the Raj approach. An insulated Tuohy needle was inserted perpendicular to skin at the midpoint of a line between the ischial tuberosity and greater trochanter. After sciatic nerve stimulation, a catheter was inserted 2–4 cm past the end of the needle and secured. The catheters were then incrementally injected with 30 mL of 1.5% mepivacaine. Twenty minutes after local anesthetic injection, sensory block was assessed using cold and pinprick tests, whereas motor block was assessed using a modified Bromage score. Complications and side effects were recorded. RESULTS:In all instances, blocks were easy to perform and were successful. No major side effects or complications were noted. CONCLUSION:Use of a simple landmark between easily identifiable bony structures enhances the simplicity and placement of a sciatic nerve catheter and is recommended for use in clinical practice.