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Biomedical subjects

A Van Poznak

Publications and source records attributed to A Van Poznak.

17 recordsLinked to original sources
PubMed1997

Effects of nitrous oxide on electrocorticography during epilepsy surgery.

Interictal spikes on intraoperative electrocorticography during epilepsy are used to tailor resections. There have been a few systematic quantitative studies of anesthetic effects on these interictal discharges, and none on the effects of nitrous oxide (N2O). We calculated spike rates on ECoG on and off N2O in 18 epilepsy surgery patients with subdural strips and grids, analyzing the most active recording contract. In a blinded analyses ten patients had fewer spikes on N2O, while eight patients had more spikes on N2O. The mean spike rates did not differ (41/min on N2O and 40/min off N2O). Spike rate on and off N2O were compared using the non-parametric Wilcoxon matched pairs test. These rates were not significantly different. Our study indicates that N2O in doses employed dose not effect interictal spikes and this agent may be used during epilepsy surgery without concerns about suppression of epileptiform activity.

Electroencephalography↗
PubMed1983

Prevention of air embolism with positive end expiratory pressure.

Pulmonary air embolism is recognized as a possible complication of neurosurgical procedures performed with the patient in the sitting position. A variety of preventive and therapeutic modalities have been proposed in the literature. We have used a consistent regimen consisting of precordial Doppler monitoring, measurement of end expiratory CO2, the semireclining position, and positive end expiratory pressure (PEEP). A right atrial catheter was not used. This approach has given good results in 81 patients; there was significant air embolism in only 1 case (1.2%). We believe that PEEP is as important in the prevention as it is in the treatment of pulmonary air embolism. By flexibly adjusting the level of PEEP, one may recreate the hemodynamic equivalent of the prone position, thereby eliminating the risk of venous air embolism and simultaneously the need for right heart catheterization.

Adolescent↗
PubMed1979

Myokymia and impaired muscular relaxation with continuous motor unit activity.

We have studied two cases of the syndrome of myokymia and impaired muscular relaxation with continuous motor unit activity. Both patients complained of muscle twitching, weakness, stiffness, and hyperhydrosis during their illness. Myokymia was present over the entire body in both. On repetitive testing of muscle strength each patient showed initial fatigue followed by increasing strength as he continued his efforts. Both patinets improved on phenytoin therapy at high blood levels. Nerve conduction velocities were decreased. Electromyograms showed continuous electrical activity at rest which persisted during sleep and spinal anaesthesia but was diminished by curare. Intravital staining with methylene blue in one case demonstrated sprouting and beading of motor nerve terminals with multiple innervation of muscle fibres. The neurophysiological and pathological findings in these two cases indicate an abnormality of peripheral nerve in this disorder.

Adult↗
PubMed1978

Evaluation of continuous monitoring of tissue pH in cats.

An improved continuous tissue pH monitoring system, designed for human subcutaneous fetal scalp tissue, was evaluated in 10 cats for total of 60 hours. Respiratory acidosis was induced with and without hypoxia to model the pathology of human clinical fetal distress. Arterial and venous pH were sampled every 15 minutes and the values were compared to those from the pH monitor system. The values paralleled arterial and venous blood pH, with correlation coefficients up to 0.98 under various pathologic acidotic conditions.

Animals↗