Letters to the Editor: Letters & Announcements
Drs. Ben-David and Uskova (1) question the relationship between prolonged tourniquet inflation time and perioperative nerve injury, suggesting that the surgical procedure itself (or other confounding variables) may play a greater role. We agree that total knee arthroplasty is a surgical procedure more commonly associated with neurologic complications (2). However, through multivariate analysis, our recent article (3) demonstrated additional independent risk factors associated with neurologic injury, including younger age (P < 0.001, odds ratio = 0.7 per 10-yr increase in age), preoperative flexion contracture >20° (P = 0.002, odds ratio = 3.9), and prolonged tourniquet time (P < 0.001, odds ratio = 2.8 per 30-min increase in tourniquet inflation). Previous investigators have also identified similar independent risk factors, including a total tourniquet time >120 min, a preoperative valgus deformity >10°, previous laminectomy, and a preexisting neurologic deficit (2,4). Complex surgical procedures are an important consideration when addressing perioperative nerve injury. However, the role of prolonged tourniquet inflation cannot be minimized or disregarded as suggested by Drs. Ben-David and Uskova.
On the basis of these clinical investigations, we recommended that the performance of a long-lasting sciatic nerve block be carefully considered in patients at increased risk of neurologic dysfunction, including those with a preoperative flexion contracture, preoperative valgus deformity, preexisting neurologic deficit, or in whom a complex or prolonged surgical procedure (and therefore tourniquet inflation) is anticipated. We do not suggest that sciatic nerve blockade is contraindicated in all patients. Last year, we performed more than 1100 sciatic nerve blocks in patients undergoing knee replacement surgery. This is in the context of performing over 10,000 orthopedic surgical cases, many of which were complex procedures in patients with multiple comorbidities (5).
We aim to provide first rate postoperative analgesia. However, we also advocate taking into consideration all identifiable patient, surgical, and anesthetic risk factors before performing any regional technique—a practice that is designed to minimize the risk of patients (and clinicians) from drowning in the bathwater.
James R. Hebl, MD
Terese T. Horlocker, MD
Department of Anesthesiology
Mayo Clinic College of Medicine
1. Ben-David B, Uskova A. Tourniquet injuries, implied causality, babies, and bathwater [Letter]. Anesth Analg 2006;103: 1593–4.
2. Horlocker TT, Cabanela ME, Wedel DJ. Does postoperative epidural analgesia increase the risk of peroneal nerve palsy after total knee arthroplasty? Anesth Analg 1994;79:495–500.
3. Horlocker TT, Hebl JR, Gali B, et al. Anesthetic, patient, and surgical risk factors for neurologic complications after prolonged total tourniquet time during total knee arthroplasty. Anesth Analg 2006;102:950–5.
4. Idusuyi O, Morrey BF. Peroneal nerve palsy after total knee arthroplasty: assessment of predisposing and prognostic factors. J Bone Joint Surg (Am) 1996; 78:177–84.
5 Medicare Provider Analysis and Review (MEDPAR) database. Centers for Medicare and Medicaid Services (CMS). Available at www.cms.hhs.gov