Neurological research
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Neurological research · Sep 1998
Influence of isoflurane anesthesia on motor evoked potentials elicited by transcortical, brainstem, and spinal root stimulation.
Electrical stimulation over the motor cortex, base of the skull, and cervical spine motor roots was performed in 9 male rats (410 +/- 86 g) before and after induction with isoflurane at 1 MAC concentration. The mean latency and amplitude of descending spinal evoked potential (DSEP) from spinal cord and motor evoked potentials (MEPs) from forearm muscles obtained after motor cortex, brainstem, and cervical root stimulations were calculated and compared. The electrical current intensity to elicit the MEPs after cortical, brainstem, and spinal roots stimulation were 23.4 +/- 7.6, 7.0 +/- 3.1, and 1.4 +/- 0.8 mA, respectively. ⋯ The amplitudes were 189 +/- 141, 672 +/- 354, and 765 +/- 389 microV for cortical, brainstem, and cervical root stimulations. The inhalation anesthesia isoflurane at 1 MAC (1.2%) completely abolished the cortical and brainstem MEPs within minutes, while the MEPs elicited by direct stimulation of the cervical spinal roots remained unchanged. Our results indicate synaptic-dependent MEPs elicited at motor cortex or brainstem levels are highly sensitive to isoflurane anesthesia.
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Neurological research · Sep 1998
Intracranial pressure waveform analysis: computation of pressure transmission and waveform shape indicators.
We studied transmission of arterial blood pressure to intracranial pressure by observing how the two pressure waveforms varied from baseline conditions to after postural change or jugular compression. Such experiments may lead to pressure waveform-based estimates of intracranial compliance. Using a single database of arterial blood pressure, central venous pressure, and intracranial pressure waveforms collected during baseline, jugular compresison, and head-elevated conditions from six Yucatan minipigs, we computed several numerical indicators of waveform shape to find an estimator of intracranial compliance. ⋯ The lack of statistically significant results may be due to the nature of the composites and/or the small sample size (n = 6). However, we hope this study stimulates further investigation of both central venous pressure-to-intracranial pressure (in addition to arterial blood pressure-to-intracranial pressure) transfer and automated computation of intracranial pressure waveform systolic slope. Such research may lead to noninvasively determined estimators of intracranial compliance.