Free and total catecholamines in critical illness.

Area of Science:

• Biochemistry
• Neuroscience
• Critical Care Medicine

Background:

• Circulating catecholamines, including norepinephrine (NE), epinephrine (E), and dopamine (DA), play crucial roles in physiological stress responses.
• Understanding catecholamine dynamics in critically ill patients is essential for managing conditions like traumatic brain injury (TBI) and vascular brain injury (VBI).

Purpose of the Study:

• To investigate the magnitude of free and total catecholamine responses in patients experiencing severe physiological stress.
• To determine the ratio of free to total catecholamines and its relationship with neurological dysfunction.

Main Methods:

• Measured circulating free and total NE, E, and DA in four patient groups: TBI, VBI, polysystem trauma, and general ICU patients.
• Assessed the proportion of free catecholamines and correlated levels with the Glasgow Coma Scale (GCS) score.

Main Results:

• Significant three- to sevenfold elevations in free and total NE and E were observed in all patient groups.
• The ratio of free to total NE and E remained constant across a wide range of concentrations.
• Free epinephrine proportion was elevated (30.1-33.5% vs. normal 16.2%), while free norepinephrine proportion remained unchanged (43.0%). Dopamine levels were generally normal.
• Inverse correlations were found between GCS scores and levels of free and total NE, E, and DA in TBI and VBI patients.

Conclusions:

• During intense and prolonged catecholamine release, the proportion of free catecholamines is maintained.
• Total and free catecholamine concentrations are directly proportional to the severity of neurological dysfunction as indicated by GCS scores.