Electrophysiological tests in intensive care

Abstract

Neuromuscular complications encountered in intensive care can be due to peripheral nerves (polyneuropathies), muscles (myopathies), neuromuscular end-plate (transmission deficit) or a combination of these. Neurophysiopathological tests that enable us to diagnose and maybe differentiate between these causes are essentially electroneurographs and electromyographs. These assess, either directly or indirectly, the integrity of the peripheral system, both sensory (centripetal afferent pathways) and motor (lower motor neurones, neuromuscular junction, muscle membrane and contractile substrate). Electrical activity in the muscle is measured using a special device (an electromyograph) comprising preamplifiers, a computer with special programmes and algorithms for analysing, digitalizing, amplifying and filtering the recorded signal and a monitor on which to visualize the on-line trace. The machine also has speakers. These serve to recognize and identify the physiological events being recorded as they make such unusual, individual sounds. An electric stimulator with constant current can be used to stimulate branches of superficial nerves (motor, sensory or mixed) so that electric conduction speed can be studied and the sensory or motor response analysed. The results can be saved on a hard disc or on any magnetic or digital support, viewed off-line or even printed.