TECHNICAL AND INTERPRETIVE PROBLEMS OF PERIPHERAL-NERVE STIMULATION IN MONITORING NEUROMUSCULAR BLOCKADE IN THE INTENSIVE-CARE UNIT

OBJECTIVE: To review the literature and provide an overview of the tec hnical and interpretive problems associated with peripheral nerve stim ulation in monitoring neuromuscular blockade in the intensive care uni t. DATA SOURCES: A computerized search on MEDLINE from 1985 through 19 94 was performed to identify English-language comparative studies, abs tracts, and review articles pertaining to peripheral nerve stimulation , brain-of-four monitoring, and neuromuscular blockade in the critical care setting. STUDY SELECTION AND DATA EXTRACTION: Relevant studies i n humans were selected and information was extracted on the use of per ipheral nerve monitoring in the critically iu. DATA SYNTHESIS: Use of peripheral nerve stimulation is complicated in the intensive care unit . Problems may occur with the patient, the device, as well as operator technique, all of which may lead to errors in interpretation of the d epth of paralysis. The critically ill patient has changing comorbid di sease states and total body water composition, which may impair the ac curacy or reproducibility of measurements. Technical problems relate t o the operation of the device, electrode placement, and suboptimal del ivery of the desired current. Difficulties in performing peripheral ne rve stimulation and interassessor variability contribute to errors of interpretation. CONCLUSIONS: These difficulties compromise the precisi on, accuracy, and reliability of the peripheral nerve stimulator as a tool for monitoring neuromuscular blockade in the critically ill. Peri pheral nerve stimulation should be used in conjunction with clinical p arameters to make decisions regarding dose adjustments. Doses should b e reduced as much as possible to provide the minimum depth of paralysi s that is clinically appropriate. Technical directions and training pr ograms for peripheral nerve stimulation should be developed, and desig nated individuals should be trained in its application. Large, prospec tive, controlled studies are necessary to evaluate the incidence of pr olonged paralysis or motor neuropathy with administration of neuromusc ular blocking agents in patients whose dose is adjusted on the basis o f peripheral nerve stimulation.