In Reply:--We appreciate Kempen's interest in our study and enjoyed reading his anecdotal report. We believe that his case is not unusual and presents several patient care issues that may be associated with the development of ulnar neuropathies.
Improper anesthetic care and patient malpositioning have been implicated as causative factors in the development of ulnar neuropathies since reports by Budinger and Garriques in the 1890s. These factors likely play an etiologic role for this problem in some surgical patients. However, other determinants may contribute to the development of postoperative ulnar neuropathies. In a series of 12 inpatients with a newly acquired ulnar neuropathy, Wadsworth and Williams determined that external compression of an ulnar nerve during surgery was contributory in only two patients. At the Mayo Clinic, a number of nonsurgical patients experience ulnar neuropathies during inpatient and outpatient treatment. We are investigating the incidence and outcomes of these neuropathies. Although our investigation is not complete, it is clear that both surgical and medical patients may experience ulnar neuropathies during or after an episode of care.
Many factors may be associated with the development of ulnar neuropathy. Although the final pathologic event usually is nerve ischemia or trauma (e.g., myelin sheath or nerve fiber disruption). etiologic mechanisms may include external nerve compression or stretch, generalized or site-specific hypoperfusion, or metabolic/genetic predisposition to neuropathy. [4,5].
Typically, anesthesia-related ulnar nerve injury is thought to be associated with external nerve compression or stretch caused by malpositioning. Although this implication may be true for some patients. three considerations suggest that other factors may contribute. First, we found several patient-related characteristics to be associated with these ulnar neuropathies. Second, a high incidence of contralateral ulnar nerve conduction dysfunction in patients with postoperative ulnar neuropathies suggests that many of these patients likely have abnormal ulnar nerves before their anesthetics but are asymptomatic. These patients may experience ulnar neuropathic symptoms during the perioperative period. Third, many patients do not notice or complain of ulnar neuropathic symptoms until more than 24 h after their surgical procedures. [3,6]We suggested several reasons for this in our report; one may be the use of postoperative sedatives in patients resting for prolonged periods in a supine position, a reason similar to that noted by Kempen.
Mark A. Warner, M.D.; Associate Professor of Anesthesiology.
Mary E. Warner, M.D.; Assistant Professor of Anesthesiology; Mayo Clinic; Rochester, Minnesota 55905.
John T. Martin, M.D.; Professor Emeritus; Department of Anesthesiology; Medical College of Ohio at Toledo; 3000 Arlington Avenue; Toledo, Ohio 43614.
(Accepted for publication on March 21, 1995.)