Middle latency auditory evoked potentials in intensive care patients and normal controls

Area of Science:

• Neuroscience
• Clinical Neurophysiology
• Intensive Care Medicine

Background:

• Evoked potentials are used in intensive care units (ICUs) to objectively measure coma parameters.
• Auditory brainstem evoked potentials aid in localizing brainstem dysfunction in comatose patients.
• Middle latency auditory evoked potentials (MLAEPs) are thought to reflect subcortical auditory pathways and the primary auditory cortex.

Purpose of the Study:

• To measure MLAEPs in normal hearing adults and intensive care unit (ICU) patients.
• To analyze the influence of biological variables on MLAEP parameters in ICU patients.
• To evaluate the potential of MLAEPs in monitoring comatose patients.

Main Methods:

• MLAEPs were recorded from 40 healthy adults and 102 ICU patients.
• Latencies, amplitudes, and amplitude ratios of MLAEPs were calculated.
• The effects of sex, age, temperature, blood gases (PO2, PCO2), renal/hepatic function, mean arterial pressure, and sedation were assessed.

Main Results:

• Right-sided auditory stimulation yielded shorter latencies and higher amplitudes than left-sided stimulation in controls.
• MLAEPs varied significantly with sex but not significantly with age.
• Temperature affected wave V latency and Na-Pa amplitude; Na-Pa amplitude correlated significantly with PO2. Sedation increased latencies and decreased amplitudes.

Conclusions:

• MLAEPs demonstrate sensitivity to biological variables like sex, temperature, and oxygenation in ICU patients.
• Sedation significantly impacts MLAEP measures, necessitating careful interpretation.
• Combining early auditory evoked potentials (AEPs) with MLAEPs may offer a valuable tool for monitoring comatose patients throughout their ICU stay.