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6209 results in Emergency Medicine

Page 108 of 311

  • 8 - ECG in Hypothermia

  • Edited by Sylweriusz Kosiński, Tomasz Darocha, Jerzy Sadowski, Rafał Drwiła
  • Book:
    Hypothermia: Clinical Aspects Of Body Cooling
    Published by:
    Jagiellonian University Press
    Published online:
    03 January 2018
    Print publication:
    01 December 2016, pp 75-80

  • Summary

    Hypothermia is defined as a drop of core temperature (usually measured in oesophagus or rectum) below 35°C. Impact of hypothermia onto electrical conduction system of heart was first described in 1892. The first observations concerning changes in ECG of a patient in accidental hypothermia date back to 1938. Hypothermia is associated with presence of characteristic changes in ECG, depending on hypothermia stage.

    Motion artefacts related to shivering and tremors are characteristic of mild hypothermia (Figure 1) together with sinus bradycardia resulting from compensatory stimulation of sympathetic nervous system.

    Prolonged exposure to low temperature significantly impairs both electric as well as mechanic activity of the heart. As a result of catecholamines release, advanced stages of hypothermia are distinguished by decreased peripheral vascular resistance and noticeable drop in cardiac output. Prolonging of action potential duration and decrease in conduction velocity in conduction system of the heart are related to delay in activation/inactivation of cellular ionic (sodium, potassium and calcium) currents. Hypothermia causes prolonging of both depolarisation duration as well as repolarisation of sinus node cells. Decrease of body temperature below 32°C causes substantial reduction of conduction velocity. In such situation, serious sinus bradycardia develops, with PR and QT/QTc intervals prolongation as well as prolongations of P wave, QRS and T wave durations (Figure 2). There is a non-linear relationship between reduced heart rate and decrease in core temperature. Prolongation of QT/QTc interval is caused both by delayed ventricular repolarisation and well as presence of so-called Osborn wave (J wave). In some patients, reduction of conduction velocity in atrio-ventricular node leads to development of conduction blocks.

    Osborn wave (J wave) is certainly the most evident anomaly in ECG of hypothermic patients. Occurrence of the wave in hypothermic patients was first recorded in 1938 (Tomasjewski), but the full description of of the phenomenon was published in 1951 by J. Osborn (hence eponym). Osborn wave is a positive deflection appearing at junction between QRS complex and ST segment, resembling “camel hump” (Figure 3).

  • 4 - Measurement of Patient's Body Temperature

    • By Jacek Majkowski, “Heat for Life” Foundation, Cracow, Poland, Tomasz Sanak, Department of Battlefield Medicine, Military Institute of Medicine, Warsaw, Poland
  • Edited by Sylweriusz Kosiński, Tomasz Darocha, Jerzy Sadowski, Rafał Drwiła
  • Book:
    Hypothermia: Clinical Aspects Of Body Cooling
    Published by:
    Jagiellonian University Press
    Published online:
    03 January 2018
    Print publication:
    01 December 2016, pp 43-52

  • Summary

    A bit of history

    The first medical thermometer, based on Gallileo's concept, was crafted by Sanctorius of Padua. The relevant information was published in 1612. Yet the person who popularised the use of temperature measurement of patients was a German physician, Carl Wunderlich. After having performed more than a million of measurements on 25,000 patients, he calculated the average temperature of a healthy person to be 37°C, and defined “fever” as body temperature exceeding 38°C.

    Temperature scales

    In Poland, as in many countries, Celsius scale is used in medical measurements. The other legally approved temperature scale in Poland is Kelvin. As Kelvin scale is base unit of SI system, the term “degree” does not apply to it. So, in order to express relationship between the two scales we can say: “Temperature 0 degrees Celsius is 273.15 Kelvin.” The difference stems from the fact that in Celsius scale 0 was set as a point of freezing of water, whilst in Kelvin scale 0 is absolute zero – theoretically lowest possible temperature.

    There are only five countries in the world where Fahrenheit scale is used instead of Celsius: The Bahamas, Belize, Cayman Islands, Palau and… United States of America. It is rumoured that German scientist Fahrenheit accepted as 0 in his scale the lowest temperature of winter season 1708/1709 in his hometown Gdańsk (–17.8°C). Similar scale to Fahrenheit, with 0 at absolute zero, is Rankine scale. Romer, Delisle, Newton and Réaumur scales are nowadays almost extinct. Yet, in 1841 there were at least 18 temperature scales!

    Temperature measurements

    Temperature cannot be measured directly like length or weight. A sensor which changes its physical properties must be used, for instance:

  • • change of volume of liquid (classic glass thermometers, e.g. containing mercury);

  • • change in resistance (thermistor and resistance temperature detector – RTD);

  • • generation of electric voltage in place of contact of two metals (thermocouple);

  • • change of colour (liquid crystal thermometer);

  • • deformation of bimetals (thermostat);

  • • emission of heat radiation (pyrometer, infrared sensor – IR);

  • • change of parameters of semiconductor contactors (integrated circuit – IC).

  • 21 - Accidental Hypothermia: the Need for the International Hypothermia Registry

    • By Beat H. Walpoth, Division of Cardiovascular Surgery, University Hospitals of Geneva, Switzerland, Marie Meyer, Dept. of Anesthesia, University Hospital, Lausanne, Switzerland, Christophe Gaudet-Blavignac, Division of Medical Information Sciences, University Hospitals of Geneva, Switzerland, Philippe Baumann, Division of Medical Information Sciences, University Hospitals of Geneva, Switzerland, Pierre Gilquin, Division of Medical Information Sciences, University Hospitals of Geneva, Switzerland, Christian Lovis, Division of Medical Information Sciences, University Hospitals of Geneva, Switzerland
  • Edited by Sylweriusz Kosiński, Tomasz Darocha, Jerzy Sadowski, Rafał Drwiła
  • Book:
    Hypothermia: Clinical Aspects Of Body Cooling
    Published by:
    Jagiellonian University Press
    Published online:
    03 January 2018
    Print publication:
    01 December 2016, pp 179-182

  • Summary

    Accidental hypothermia can be of multiple aetiologies and is often related to an accident in a cold environment and contrasts with urban hypothermia. People living in the cold such as workers, fishermen and military personnel are at risk. More recently there is an increase in unprepared lay people practicing leisure activities such as winter sports, thus exposing themselves to hypothermia in case of an accident. Most of the cases concern mild hypothermia which does not need hospitalization or medical assistance. In contrast, deep hypothermia, with or without cardiac arrest, is rare and carries a high mortality in healthy adults and children [1, 2, 3].

    Induced hypothermia which has been used for cardiac surgery as well as therapeutic hypothermia used for brain ischaemia, are medically indicated and highly monitored and therefore cannot be compared to accidental hypothermia. Patients with induced hypothermia may reach the same degree (< 28°C) but are in controlled narcosis and are normally cooled down and rewarmed by Cardiopulmonary Bypass (CPB) [4]. Therapeutic hypothermia cools the patient to mild hypothermia (32–34°C) to enhance a better and faster functional brain recovery [5].

    The concept of applying the technique of CPB rewarming, as used in induced deep hypothermic cardiac arrest, to victims of accidental hypothermia with temperatures below 28°C and cardio-respiratory arrest was initiated successfully by Prof. Ueli Althaus at the University Hospital Insel in Bern, Switzerland over 30 years ago [6]. Since that time our team and other Swiss universities started to use this method and we published a multi-centre study showing a long-term sequelae-free survival rate of 47% after rewarming of 32 deep accidental hypothermic patients in cardiac arrest using cardiopulmonary bypass (CPB) [7]. Due to the fact that many patients died from post-rewarming complications, we and others have shown the beneficial effect of using extra-corporeal life support (ECLS) such as prolonged ECMO use after rewarming for cardiovascular and pulmonary dysfunctions [8, 9].

Page 108 of 311