High level of extracellular potassium and its correlates after severe head injury: relationship to high intracranial pressure

Reinert, M; Khaldi, A; Zauner, A; Doppenberg, E; Choi, S; Bullock, R (2000). High level of extracellular potassium and its correlates after severe head injury: relationship to high intracranial pressure. Journal of neurosurgery, 93(5), pp. 800-7. Charlottesville, Va.: American Association of Neurological Surgeons 10.3171/jns.2000.93.5.0800

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OBJECT: Disturbed ionic and neurotransmitter homeostasis are now recognized as probably the most important mechanisms contributing to the development of secondary brain swelling after traumatic brain injury (TBI). Evidence obtained in animal models indicates that posttraumatic neuronal excitation by excitatory amino acids leads to an increase in extracellular potassium, probably due to ion channel activation. The purpose of this study was therefore to measure dialysate potassium in severely head injured patients and to correlate these results with measurements of intracranial pressure (ICP), patient outcome, and levels of dialysate glutamate and lactate, and cerebral blood flow (CBF) to determine the role of ischemia in this posttraumatic ion dysfunction. METHODS: Eighty-five patients with severe TBI (Glasgow Coma Scale Score < 8) were treated according to an intensive ICP management-focused protocol. All patients underwent intracerebral microdialyis. Dialysate potassium levels were analyzed using flame photometry, and dialysate glutamate and dialysate lactate levels were measured using high-performance liquid chromatography and an enzyme-linked amperometric method in 72 and 84 patients, respectively. Cerebral blood flow studies (stable xenon computerized tomography scanning) were performed in 59 patients. In approximately 20% of the patients, dialysate potassium values were increased (dialysate potassium > 1.8 mM) for 3 hours or more. A mean amount of dialysate potassium greater than 2 mM throughout the entire monitoring period was associated with ICP above 30 mm Hg and fatal outcome, as were progressively rising levels of dialysate potassium. The presence of dialysate potassium correlated positively with dialysate glutamate (p < 0.0001) and lactate (p < 0.0001) levels. Dialysate potassium was significantly inversely correlated with reduced CBF (p = 0.019). CONCLUSIONS: Dialysate potassium was increased after TBI in 20% of measurements. High levels of dialysate potassium were associated with increased ICP and poor outcome. The simultaneous increase in dialysate potassium, together with dialysate glutamate and lactate, supports the concept that glutamate induces ionic flux and consequently increases ICP, which the authors speculate may be due to astrocytic swelling. Reduced CBF was also significantly correlated with increased levels of dialysate potassium. This may be due to either cell swelling or altered vasoreactivity in cerebral blood vessels caused by higher levels of potassium after trauma. Additional studies in which potassium-sensitive microelectrodes are used are needed to validate these ionic events more clearly.

Item Type:	Journal Article (Original Article)
Division/Institute:	04 Faculty of Medicine > Department of Head Organs and Neurology (DKNS) > Clinic of Neurosurgery
UniBE Contributor:	Reinert, Michael
ISSN:	0022-3085
ISBN:	11059661
Publisher:	American Association of Neurological Surgeons
Language:	English
Submitter:	Factscience Import
Date Deposited:	04 Oct 2013 15:02
Last Modified:	05 Dec 2022 14:19
Publisher DOI:	10.3171/jns.2000.93.5.0800
PubMed ID:	11059661
Web of Science ID:	000090033800011
URI:	https://boris.unibe.ch/id/eprint/27041 (FactScience: 101381)