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Somatosensory evoked potentials in intracranial hypertension: analysis of the effects of hypoxia

1991; American Association of Neurological Surgeons; Volume: 75; Issue: 1 Linguagem: Inglês

10.3171/jns.1991.75.1.0108

1933-0693

Paul Eldridge, Daniel Hope, Patrick M. Yeoman, I. Farquhar, Michael Mitchell, Sharon A. Clarke, N. J. Smith,

Optical Imaging and Spectroscopy Techniques

✓ The loss of somatosensory evoked potentials (SSEP's) was investigated in a feline model of intracranial hypertension. Threshold values of cerebral perfusion pressure (CPP) and cerebral blood flow (CBF) required for maintenance of SSEP's are defined using a mathematical model. The model describes loss of amplitude of SSEP's using the form of a dose-response curve. Amplitude of the SSEP's declined to 50% of control values at a CBF of 15 ml/100 gm/min and a CPP of 20 mm Hg in the normoxic animal; in the presence of mild hypoxia (8 to 9 kPa), a significant increase in these values to 18 ml/100 gm/min and 32 mm Hg, respectively, occurred. No reliable changes in latency or central conduction time were demonstrated. It is concluded that, given adequate oxygenation, evoked electrical activity is lost at too low a level of CPP for this parameter to be useful in clinical monitoring. However, even mild hypoxia, when combined with intracranial hypertension, produces a major risk to neuronal integrity.