A number of physiological factors can influence the intra-ocular pressure of patients with normal, healthy eyes leading to the misinterpretation of tonometric findings. The influence and duration of four commonly encountered factors--drinking water, coffee, alcohol, and exercise--were investigated employing a non-contact tonometer. Drinking 1 litre of water increased the IOP for up to 140 min with a mean maximum increase of 4.4 mmHg. A similar change was induced by coffee, the increase lasting up to 95 min and displaying a mean maximum increase of 4.0 mmHg. The intra-ocular pressure fell with alcohol consumption by a maximum of 3.7 mmHg, regaining pre-test values in all subjects after 65 min. Vigorous exercise produced an immediate fall in mean intra-ocular pressure of 4.3 mmHg, initial pressure being restored in all subjects after 65 min. The impact of such factors upon normal physiology are discussed together with the implications for routine tonometry.

SUMMARY EEG was monitored at bilateral scalp sites outside the operative field during hypotensive aneurysm surgery in 21 patients. Mean arterial blood pressure at axillary level was 50-60 mm Hg (average 55 mm) for 1.9-5.3 hours (average 3.6). Four new deficits were noted immediately post-operatively, all related to the operated site: these were attributable to intra-operative rupture with forced vascular clipping, vasospasm, or edema. In no instance was hypotension solely responsible for a new deficit. EEG showed persistent slowing in relation to surgery in only 1 patient, where aneurysmal rupture led to severe hypotension, forced clipping of 1 posterior cerebral artery, and subsequent brain stem infarction. In the 3 other patients with fresh focal postoperative deficits, no persistent intraoperative EEG changes were observed. EEG monitoring did not detect ischemia in these 3 patients because 1) hypotension was moderate and did not perse cause new deficit, and 2) EEG electrodes did not survey the area at maximal risk, namely the operative field. EEG scalp electrodes near but outside the operative site do not seem useful for monitoring cerebral function in the region of aneurysm surgery. Epidural or cortical electrodes in the operative field may prove to be more useful.Stroke Vol 10, No 3, 1979RUPTURE OF an intracranial aneurysm during surgery remains a threat even in the era of microsurgery. Profound controlled hypotension reduces the risk of rupture and aids dissection. 1 Hypotension "defuses" the aneurysm by markedly decreasing wall tension. As one reduces cerebral perfusion pressure, however, the lower limit of autoregulation is approached, and risks of cerebral ischemia increase. This is particularly true when subarachnoid hemorrhage or surgical manipulation has already compromised autoregulation. Therefore, reliable techniques are needed for monitoring the CNS response to lowered blood pressure during aneurysm surgery.Since the electroencephalogram (EEG) continuously assesses certain aspects of electrophysiologic function of the brain, this test seemed potentially useful for monitoring hypotension during aneurysm surgery. EEG monitoring during carotid endarterectomy during cardiopulmonary bypass can likewise warn of cerebral ischemia during hypotension. In a series of 75 patients undergoing cardiopulmonary bypass, intraoperative EEG accurately predicted postoperative neuropsychiatric deficits and in several instances ischemic EEG changes were reversed by raising mean arterial blood pressure." Therefore, we have studied the clinical usefulness of intraoperative EEG as a monitor of the CNS response to induced hypotension during aneurysm surgery. Methods PatientsTwenty-one patients undergoing aneurysm surgery were studied. Characteristics of these patients are

SUMMARY A study of 10 patients with brachial plexus trauma was performed to determine whether the diagnostic accuracy of sensory evoked potentials (SEPs) may be improved by using stimulation of multiple peripheral nerves (median, radial, musculocutaneous and ulnar peripheral nerves: median (C6-T1), radial (C6), musculocutaneous (C5), and ulnar (C8-Tl). In addition, the relative advantages of SEPs and peripheral electrophysiological studies were considered. MethodsThe median, ulnar and superficial radial nerves were stimulated at the wrist on both sides and in two patients the musculocutaneous nerve was stimulated in the forearm.Stimuli were delivered at 2Hz by a TECA constant voltage isolated nerve stimulator with a pulse duration of 0-1 ms. The stimulus intensity was adjusted to produce a small twitch in the thenar or hypothenar muscles (median and ulnar) or to be three times sensory threshold in the case of superficial radial and musculocutaneous nerves.Gold disc 9 mm recording electrodes were attached to the skin using Grass electrode paste and tape. Electrodes were placed over Erb's point, the spinous process of the second and seventh cervical vertebrae, and the contralateral somatosensory cortex. These were referred to a common mid-frontal site (Fz). Signals were amplified and averaged by a DISA (model 1500) system with the high and low pass filters set at 2 Hz and 2 kHz for the scalp responses and 20 Hz and 2 kHz for the cervical and Erb's 1014 Protected by copyright. on 11 May 2018 by guest.