Patient assessment

A patient suspected of hypothermia requires special treatment. Evaluation of hypothermia severity and prevention of iatrogenic cardiac arrest are crucial. The gold standard measurement for core temperature is measurement in lower 1/3 of oesophagus, what can be problematic in conscious patients retaining vomiting reflex [1]. Methods of temperature measurement have been described in Chapter 4 of this book.

If a prehospital rescue team possess no appropriate thermometer an approximate assessment should be performed with Swiss Staging System devised for this purpose [2] – Table 1.

The original Swiss classification published in 2003 has been updated [2].

Searching for presence of breath and pulse should take at least 1 minute [3]. Difficulties in diagnosis result from breath becoming significantly slow and shallow, and from bradycardia with low systemic blood pressure. Wrong diagnosis of cardiac arrest and erroneous commencement of CPR may lead to ventricular fibrillation (VF) [4]. ECG displayed on monitor may be helpful – VF or asystole require instant commencement of resuscitation. Presence of organised rhythm necessitates verification of spontaneous circulation. In absence of palpable pulse, capnography (distinctive “wavy” capnogram suggests presence of circulation) or ultrasonography may be used [1].

Freezing of body tissues makes chest compressions impossible, evident fatal injuries such as decapitation, major crush injuries of the trunk etc. and unequivocal asphyxiation preceding hypothermia (burial, drowning in warm water) are situations where no indications for resuscitation exist. In all other patients in whom hypothermia occurred with patent airways, regardless of body temperature, the rule “nobody is dead until warm and dead” should be applied [1, 3].

Management of basic body functions

Circulatory system

In the natural course of cooling of the heart, cardiac arrest occurs in asystole [4]. Hypothermic heart, however, is very prone to VF as a result of various, even very slight stimuli: mechanical (rough transportation, ambulation, resuscitation), changes in pH (excessively aggressive ventilation), changes of temperature (afterdrop). It is most likely a result of non-uniform prolongation of action potential in various areas of myocardium (refraction dispersion) and forming of looped impulse circuit (reentry) [4, 5].