Electroencephalogram silence ratio for early outcome prognosis in severe head trauma.

OBJECTIVE: To introduce the electroencephalogram silence-ratio (ESR) as a variable derived from mathematically processed electroencephalogram for early outcome prognosis in patients with severe head trauma and to comparatively assess sensitivity, specificity and predictive value vs. somatosensory evoked potentials and brainstem auditory evoked potentials. DESIGN: Prospective, interventional study. SETTING: Intensive care unit of a university hospital. PATIENTS: A total of 32 adults with severe acute head trauma (Glasgow Coma Scale score < or = 8). METHODS AND MAIN RESULTS: In all patients, electroencephalographic recording was continuously performed by frontomastoid electrode montage for 24-96 hrs after admission to the ICU. The data were subsequently computed by fast Fourier analysis and the ESR (intervals of suppression as periods >240 msecs during which the electroencephalographic voltage did not exceed 5 microV) was displayed and recorded on a computer for further evaluation. Somatosensory evoked potentials and brainstem auditory evoked potentials were elicited during the first 2 days after admission. Outcome evaluation was performed 6 months after trauma using the Glasgow Outcome Scale and the Rappaport Disability Rating Scale. After careful artifact exclusion, the ESR depicted the highest sensitivity, specificity, and positive predictive value compared with evoked potentials. Even a highly significant correlation between outcome and ESR was found (p < .0001). CONCLUSION: The ESR is a valuable variable showing a high reliability with respect to outcome prediction in severe head trauma with a higher predictive value than short latency somatosensory evoked potentials. Evidence exists that the ESR provides at least partial information regarding adequate cerebral oxygen delivery.

Functional recovery despite prolonged bilateral loss of somatosensory evoked potentials: report on two patients.

A bilateral loss of short latency somatosensory evoked potentials (SSEPs) after head trauma or non-traumatic brain damage is normally associated with a deleterious neurological outcome. An adequate recovery in reported in two deeply comatose patients with head trauma or severe hypertensive encephalopathy despite prolonged bilateral loss of SSEPs over days, found in repeated recordings. Hence, a bilateral loss of SSEPs should not be considered alone for prediction of outcome in cerebral injury.

Effects of hypertonic-hyperoncotic infusion on the human atrial natriuretic factor in a standardized clinical trial.

Hypertonic-hyperoncotic solutions (HHT) are presently being utilized to resuscitate patients in shock. However, so far, the effects of HHT on human atrial natriuretic factor (hANF) have not yet been investigated in a clinical trial. The effects of HHT on hANF were studied in a standardized preoperative and clinical setting in patients undergoing aneurysmectomy. Twenty-three conscious patients were included in two groups: 11 HHT and 12 HES (HHT: 7.5% NaCl/10% HES 200; HES: .9% NaCl/10% HES 200). Stepwise infusion of 50 mL was titrated preoperatively according to individual Frank-Starling relationships. Central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) were determined before, during and after volume application. hANF, cGMP were also measured before and 1, 10, 30, 60, and 120 min after administration. The volumes necessary to produce the same volume status were: 213.6 +/- 63.6 mL of HHT, 409.9 +/- 136.2 mL of HES (p < .001). The sodium load was 273.9 +/- 81.5 mmol of [HHT], 63.1 +/- 21.0 mmol of [HES] (p < .001).(ABSTRACT TRUNCATED AT 250 WORDS)

[The performance of respirator alarms during simulated critical events in CMV/IPPV artificial respiration]. / Alarmverhalten von Respiratoren bei definiert auslösbaren Störfällen unter CMV/IPPV-Beatmung.

Alarm systems of ventilators enhance detection of possible critical events during artificial ventilation. Due to their significance, in some countries the alarm detection of ventilators is regulated by federal law. Up to now, no recommendations for the adjustment of alarm limits exist and only a few detailed investigations of the accuracy of alarm detection are available. METHODS. The response of four commercially available ventilators (Servoventilator 900C, Siemens, Inc.; Bennett 7200a, Hoyer, Inc.; Veolar, Hamilton, Inc.; EVITA, Dräger, Inc.) to critical events during artificial ventilation of a test lung were evaluated. We measured the alarm time (the time between event creation and alarm response) of ten different simulated critical events including disconnection, differentisized leaks, failure of the gas supply, and obstruction at different places in the artificial airway. DISCUSSION. All respirators were able to recognise severe critical situations such as hose disconnection, failure of gas supply, and total airway obstruction within a short time (< 15 s). The recognition of small airway leaks was more difficult for the ventilators even when the alarm thresholds were close. The alarm detection of the EVITA (software 10.0 or less) under conditions of partial airway obstruction may be a source of risk for the patient as the machine continued supplying inspiration with pressure-limited ventilation even when the pressure threshold was reached.