Minimal effects on ex vivo coagulation during mild therapeutic hypothermia in post cardiac arrest patients.

OBJECTIVES: Mild therapeutic hypothermia (MTH) is being used to improve neurological outcome and survival in patients successfully resuscitated after cardiac arrest. The impact on coagulation may be difficult to assess since most coagulation parameters are measured at 37°C and not at actual body core temperature. Therefore we investigated the effects of MTH both at body core (target) temperature of 32°C and at 37°C. METHODS: Patients admitted at the ICU after cardiac arrest treated with MTH. Baseline blood samples, measured at 37°C were taken directly at arrival. The second and third samples were drawn within 1h and 24h after reaching target temperature and were measured at 32°C and 37°C. A final sample was drawn when the patient returned to normotemperature (measured at 37°C). Clotting time (CT) and maximum clotting formation (MCF) were measured with thromboelastometry. RESULTS: Upon reaching target temperature (32°C) Extem and Intem CT were increased compared to baseline with 57s (49-75) to 65s (59-72) and 165s (144-183) to 193s (167-212) respectively (median with IQR; P<0.05), with a further significant increase after 24h of hypothermia with 68s (57-80) and 221s (196-266). Samples analyzed at 32°C showed a significant longer CT of 12s in Extem and 33s in Intem compared to 37°C. MCF was not affected by MTH or adjustment of temperature. CONCLUSION: The mild effect of MTH on coagulation parameters remains unidentified when measured at 37°C. Although measurements at 32°C differ from those at 37°C, this does not appear to be of clinical relevance as all values were still within the reference range.

The effect of audible alarms on anaesthesiologists' response times to adverse events in a simulated anaesthesia environment: a randomised trial.

Alarms are ubiquitous in anaesthetic practice, but their net effect on anaesthesiologists' performance and patient safety is debated. In this study, 27 anaesthesiologists performed two simulation sessions in random order; one session was programmed to include an alarm condition, with a standard, frequent, clearly audible alarm sound. During these sessions, adverse events were simulated and anaesthesiologists' response times to these events were recorded. Perceived workload was assessed with the NASA Task Load Index. Response times to adverse events and perceived workload were similar in both groups. Pooled response times to atrial fibrillation and desaturation were fast, with a median (range [IQR]) of 8 (4-14 [1-41]) s and 9 (6-16 [1-44]) s, respectively. Pooled response times to an ST segment elevation on the ECG and an obstructed intravenous line were significantly slower, with median (IQR[range]) times of 34 (21-76[4-300]) s and 227 (95-399 [2-600]) s, respectively (p < 0.001). This study shows that in a simulated anaesthesia environment, response times to adverse events are similar in the absence or presence of an audible alarm, and that response times to various critical events differ.

Intra-operative monitoring--many alarms with minor impact.

Alarms are key components of peri-operative monitoring devices, but a high false-alarm rate may lead to desensitisation and neglect. The objective of this study was to quantify the number of alarms and assess the value of these alarms during moderate-risk surgery. For this purpose, we analysed documentation of anaesthesia workstations during 38 surgical procedures. Alarms were classified on technical validity and clinical relevance. The median (IQR [range]) alarm density per procedure was 20.8 (14.5-34.2 [3.7-85.6]) alarms.h⁻¹ (1 alarm every 2.9 min) and increased during induction and emergence of anaesthesia, with up to one alarm per 0.99 min during these periods (p < 0.001). Sixty-four per cent of all alarms were clinically irrelevant, whereas 5% of all alarms required immediate intervention. The positive predictive value of an alarm during induction and emergence was 20% (95% CI 16-24%) and 11% (95% CI 8-14%), respectively. This study shows that peri-operative alarms are frequently irrelevant, with a low predictive value for an emerging event requiring clinical intervention.