Inappropriate Implantable Cardioverter-Defibrillator Therapy During Total Hip Arthroplasty.

Electromagnetic interference (EMI) is a known risk factor for triggering inappropriate therapy from implantable cardioverter-defibrillators (ICDs). Recommendations from the American Society of Anesthesiologists focus on EMI when using monopolar electrocautery for supraumbilical surgeries. Infraumbilical surgeries are not considered high risk for EMI; thus, no magnet must be applied routinely to prevent inappropriate ICD therapy intraoperatively. We describe a case of a 71-year-old woman who presented for left total hip arthroplasty with a history of an ICD. The patient's history was significant for non-ischemic cardiomyopathy. Monopolar electrocautery was used, and the level of the surgery was below the umbilicus. She experienced nine inappropriate ICD therapies intraoperatively with no long-term sequelae. The location of the electrocautery dispersion pad may have contributed to inappropriate therapies. Thus, the dispersion pad location should be considered when deciding whether to suspend anti-tachycardia functions intraoperatively. We present a case of inappropriate therapy from an ICD and make a recommendation for preventing such events.

Clotting-Factor Concentrations 5 Days After Discontinuation of Warfarin.

BACKGROUND: The American Society of Regional Anesthesia and Pain Medicine guidelines recommend discontinuation of warfarin and an international normalized ratio (INR) of 1.2 or less before a neuraxial injection. The European and Scandinavian guidelines accept an INR of 1.4 or less. We evaluated INR and levels of clotting factors (CFs) II, VII, IX, and X 5 days after discontinuation of warfarin. METHODS: Patients who discontinued warfarin for 5 days and had an INR of 1.4 or less had activities of factors II, VII, IX, and X measured. The primary outcome was the frequency of subjects with CF activities of less than 40%. RESULTS: Twenty-three patients were studied; 21 (91%) had an INR of 1.2 or less. In these 21 patients, the median (interquartile range) activities of factors II, VII, IX, and X were 66% (52%-80%), 114% (95%-132%), 101% (84%-121%), and 55% (46%-63%), respectively. Ninety-five percent (99% confidence interval, 69%-99%) had CF activities of greater than 40%. The patient who did not CF activities greater than 40% had end-stage renal disease. Two subjects had an INR of greater than 1.2; the activities of factor II, VII, IX, and X were 37% and 46%, 89% and 105%, 66% and 78%, and 20% and 36%, respectively. Neither patient had CF activities of greater than 40%. CONCLUSIONS: Based on 40% activity of CFs, patients with INRs of 1.2 or less can be considered to have adequate CFs to undergo neuraxial injections. The number of patients with an INR of 1.3 and 1.4 is too small to make conclusions.

Back Pain and Neuraxial Anesthesia.

The incidence of back pain after neuraxial anesthesia in the adult population is not different from that after general anesthesia. The pain is usually mild, localized in the low back, rarely radiates to the lower extremities, and has a duration of only a few days. The risk factors for development of back pain include the lithotomy position, multiple attempts at block placement, duration of surgery longer than 2.5 hours, body mass index ≥32 kg/m, and a history of back pain. However, there is no permanent worsening of preexisting back pain after neuraxial anesthesia. The back pain has been attributed to tears in the ligaments, fascia, or bone with localized bleeding; immobility of the spine; relaxation of the paraspinal muscles under anesthesia; flattening of the normal lumbar convexity; and stretching and straining of the lumbosacral ligaments and joint capsules. The addition of an anti-inflammatory drug to the local anesthetic used for skin infiltration may decrease the incidence and severity of back pain. The use of spinal or epidural anesthesia in the adult, non-obstetric and obstetric populations should depend on the advantages offered by the technique and not on the occurrence of back pain after the procedure. Additional studies are needed to confirm the efficacy of epidural dexamethasone, or other steroids, or the addition of an anti-inflammatory drug to the local anesthetic infiltration for the prevention of back pain after neuraxial anesthesia. Future studies should involve a physician with expertise in the evaluation of chronic low back pain to help identify the cause of the back pain and institute appropriate treatment(s).

A dose-ranging study of 0.5% bupivacaine or ropivacaine on the success and duration of the ultrasound-guided, nerve-stimulator-assisted sciatic nerve block: a double-blind, randomized clinical trial.

BACKGROUND AND OBJECTIVES: Before bifurcation, the sciatic nerve is composed of 2 component nerves encased in a common investing extraneural layer (CIEL). We examined the effect of various volumes injected beneath the CIEL on the success and duration of sciatic nerve block. METHODS: Ultrasound-guided nerve-stimulator-assisted sciatic nerve blocks were performed on 142 subjects. Subjects were randomized into 14 groups (0.5% ropivacaine or bupivacaine) with epinephrine 1:300,000 in volumes ranging from 2.5 to 30 mL. Successful block was defined as a complete sensory and motor block at 60 minutes. The minimum threshold current, time to complete block, duration of sensory and motor block, postoperative pain, and analgesic requirements were recorded. RESULTS: The mean threshold current external to the CIEL was 0.52 (0.15) mA compared to 0.19 (0.09) mA beneath the CIEL (P < 0.001). Successful block was achieved in 30 of 40 subjects that received 5 mL or less of ropivacaine or bupivacaine compared with 97 of 99 that received 10 mL or greater volume (P = 0.006). Injection volumes greater than or equal to 10 mL produced complete sensory and motor block within 30 minutes. Volumes greater than 10 mL did not extend the duration of the sensory or motor block. Injection volumes of 2.5 and 5 mL were associated with delayed onset and decreased block duration and a greater fraction of subjects experiencing pain behind the knee. CONCLUSIONS: Injecting 10 mL of 0.5% bupivacaine or ropivacaine below the CIEL produces comparable onset and duration of sensory and motor blockade as volumes as large as 30 mL.

Ambulatory anesthesia in an adult patient with corrected hypoplastic left heart syndrome.

With recent advancements in clinical science, an increasing number of patients with congenital heart defects are surviving into adulthood and presenting for noncardiac surgeries. We describe one such example of a 26-year-old patient with corrected hypoplastic left heart syndrome presenting for knee arthroscopy and performed under general anesthesia with preoperative ultrasound guided saphenous nerve block. In this case, we review the anesthetic implications of corrected single ventricle physiology, anesthetic implications, as well as discuss the technique and role of saphenous nerve block in patients undergoing knee arthroscopy.