Die Zuverlässigkeit der pulsoximetrischen Überwachung der arteriellen Sauerstoffsättigung bei zentralisierten und hypothermen Patienten

Clinical relevance of impaired consciousness in accidental hypothermia: a Japanese multicenter retrospective study

Aim

This study aimed to investigate the association between level of impaired consciousness and severe hypothermia (<28°C) and to evaluate the association between level of impaired consciousness and inhospital mortality among accidental hypothermia patients.

Methods

This was a multicenter retrospective study using the J‐Point registry database, which includes data regarding patients whose core body temperature was 35.0°C or less and who were treated as accidental hypothermia in emergency departments between April 1, 2011 and March 31, 2016. We estimated adjusted odds ratios of the level of impaired consciousness for severe hypothermia less than 28°C and inhospital mortality using a logistic regression model.

Results

The study included 505 of 572 patients in the J‐Point registry. Relative to mildly impaired consciousness (Glasgow Coma Scale [GCS] 13–15), the adjusted odds ratios for severe hypothermia less than 28°C were: moderate (GCS 9–12), 3.26 (95% confidence interval [CI], 1.69–6.25); and severe (GCS < 9), 4.68 (95% CI, 2.40–9.14). Relative to mildly impaired consciousness (GCS 13–15), the adjusted odds ratios for inhospital mortality were: moderate (GCS9–12), 1.65 (95% CI, 0.95–2.88); and severe (GCS < 9), 2.10 (95% CI, 1.17–3.78).

Conclusion

The level of impaired consciousness in patients with accidental hypothermia was associated with severe hypothermia and inhospital mortality.

Accidental hypothermia

Accidental hypothermia causes profound changes to the body's physiology. After an initial burst of agitation (e.g., 36-37°C), vital functions will slow down with further cooling, until they vanish (e.g. <20-25°C). Thus, a deeply hypothermic person may appear dead, but may still be able to be resuscitated if treated correctly. The hospital use of minimally invasive rewarming for nonarrested, otherwise healthy patients with primary hypothermia and stable vital signs has the potential to substantially decrease morbidity and mortality for these patients. Extracorporeal life support (ECLS) has revolutionized the management of hypothermic cardiac arrest, with survival rates approaching 100%. Hypothermic patients with risk factors for imminent cardiac arrest (i.e., temperature <28°C, ventricular arrhythmia, systolic blood pressure <90 mmHg), and those who have already arrested, should be transferred directly to an ECLS center. Cardiac arrest patients should receive continuous cardiopulmonary resuscitation (CPR) during transfer. If prolonged transport is required or terrain is difficult, mechanic CPR can be helpful. Intermittent CPR may be appropriate in hypothermic arrest when continuous CPR is impossible. Modern postresuscitation care should be implemented following hypothermic arrest. Structured protocols should be in place to optimize prehospital triage, transport, and treatment as well as in-hospital management, including detailed criteria and protocols for the use of ECLS and postresuscitation care.

Prehospital resuscitation of the buried avalanche victim

In North America and Europe, approximately 150 people die of avalanches per year, and fatalities are presumed to be many times higher in developing countries. Four factors are decisive for survival: grade of burial, duration of burial, presence of an air pocket and a free airway, and severity of trauma. According to Swiss data, the overall mortality rate with avalanche burial is 23%, but it largely depends on the grade of burial. While the mortality rate is 52.4% in completely buried (head below the snow) victims in the Swiss population, it is only 4.2% in partially buried (head free) victims. Additionally, survival in completely buried victims drops to 30% within the first 35 min, initially due to death from lethal trauma, followed by asphyxia in 20-35 min. Thereafter, survival decreases more gradually and victims who are not fatally injured and are able to breath under the snow slowly succumb to hypoxia, hypercapnia, and hypothermia. In the absence of fatal injuries, rescue strategies depend on the duration of burial and the victim's core temperature. With a burial time<35 min, survival depends on preventing asphyxia by rapid extrication, adequate airway management, and cardiopulmonary resuscitation. With a burial time>35 min, tackling hypothermia is of utmost importance. Therefore, gentle extrication and continuous core temperature and electrocardiogram monitoring are recommended. Pulseless victims with a patent airway and a core temperature<32°C should receive uninterrupted cardiopulmonary resuscitation and be transported to a hospital with extracorporeal rewarming facilities.

Reflection and transmission pulse oximetry during compromised peripheral perfusion

The performance of a reflection pulse oximeter and a transmission pulse oximeter was assessed during open-heart surgery when cardiac output, peripheral temperature, pulse pressure, and systolic pressure were low and vascular resistance was high. Before and after extracorporeal circulation (ECC) there was no difference in ability of the sensors to obtain readings and no difference in the accuracy of those readings. During partial ECC, especially after coronary artery bypass grafting, the reflection sensor gave readings earlier and at a lower pulse pressure. In addition, the transmission sensor failed to give any readings for 2 patients on partial ECC, for whom the reflection sensor did give readings. The accuracy of heart rate (HR) data was comparable for both sensors before ECC; however, during partial ECC, the reflection sensor tended to give values closer to the electrocardiographic HR. The accuracy of saturation data given by the reflection oximeter was comparable to that of the transmission oximeter. It is concluded that the accuracy of the saturation and HR data provided by the two methods of pulse oximetry are comparable, but that the reflection sensor is more likely to obtain readings under conditions of poorer peripheral circulation.