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Exertional heat illness
CORRESPONDENCE
COMMENTARY
CORRESPONDENCE Exertional heat illness Sir—A M W Porter (Feb 12, p 569)1 describes a typical case of exertional heat illness (EHI), which led to the death of a young British officer-cadet. He rightly raises several points of concern in that context. In analysing events associated with the initial collapse of the cadet, Porter efficiently tackles issues concerning the protocols of the Royal Army Medical Corps, military tactics in marching laden foot soldiers in the battlefield, and the attitude of instructors and platoon commanders towards cadets lagging behind squads during field training. However, the points relating to the pathophysiology of the condition and its intervention deserve some critical discussion because they represent the focus of the impact’s seriousness on such individuals worldwide, not only in the British army. While the irrelevance of dehydration is rightly pointed out, the emphasis on occlusive clothing hindering sweat evaporation as a primary cause of collapse from EHI is an oversimplification. Also, it is true that the preoccupation of medical officers and instructors with water intake is a dangerous distraction from the real issue. But so is Porter’s statement on cooling. It is surprising that external cooling still occupies a central position in the management of heat illnesses, when it is known to have adverse effects on skin circulation, which is the main mechanism of coresurface heat dissipation. Citing a 1967 reference2 Porter adopts, and recommends, an outdated management approach. The Royal Military Academy in Britain may have been correct in not adopting the mechanical approach we, in Mecca, Saudi Arabia, used to practise for many years; that is exposing the patient to vigorous cooling procedures. Immediate vigorous cooling will result in shivering, which will aggravate core temperature load. Sympathetic nervous system impulses are known to cause the smooth muscles of the tunica media of the skin arterioles to constrict in response to several factors, especially hypovolaemia and hypotension. Hypothalamic signals inhibit these impulses, thereby facilitating
1992
vasodilation and sweating. Excessive external cooling of heatstroke patients causes shivering, even if their core temperature is over 40°C, and they do not sweat. Although Porter does not specify how the core temperature (42°C) was measured, presumably it was via the rectum. Rectal temperature (RT) is becoming increasingly criticised as the main criterion of recovery to be targeted during treatment of heatstroke.3 Measurement of tympanic membrane temperature is more accurate in reflecting that of the hypothalamus than RT. Porter may be right in criticising the statement ascribed to the British army’s legal representative that “no one can call off a march in Kosovo”, but if it were to address the issue on an international scale, the statement could very well withstand scrutiny. As for Mecca pilgrims it is true that no one can call off the Hajj march in Mecca. Several armies, worldwide, may also face a similar situation, where laden foot soldiers may have to alternate fast marching with running for a distance. This is the case, for instance, in open plains such as Middle Eastern deserts, particularly if air raids pose a constant threat to uncovered ground troops. I have worked with pilgrims doing the annual Hajj rituals in Mecca who develop heat illness, and have established several facts that have led to novel approaches to its management. Among these is the cold intravenous infusion method, which has proved effective as a method of choice for treating people with mild heat exhaustion,4 as well as acute heatstroke.5 This method is practical for use in scattered field stations; convenient for Hajj and, probably also, in military situations. Amin Kashmeery Biomedical Ethics Programme, Oxford Academy for Advanced Studies, Oxford OX4 1UT, UK (e-mail: [email protected]) 1
2
3
Porter AMW. The death of a British officercadet from heat illness. Lancet 2000; 355: 569–71. Shibolet S, Coll R, Gilat T, et al. Heatstroke: is clinical picture and mechanism in 36 cases. Q J Med 1967; 36: 525–48. Ash CJ, Cook JR, McMurry TA, et al. The
4
5
use of rectal temperature to monitor heatstroke. Mo Med 1992; 89: 283–88. Kashmeery AMS. Physiological studies on heat exhaustion victims among Mecca Pilgrims: response to relevant hormones, and effect of cold iv infusion on recovery. Acta Medica Austriaca 1995; 1/2: 16–22. Kashmeery AMS. Cold iv infusion vs body cooling unit in heatstroke treatment. Int J Health Sciences 1995; 6: 195–200.
Sir—Research into exertional heat stroke (EHS) has been carried out at the Heller Institute of Medical Research, Tel Hashomer, Israel, for over 40 years, so based on our cumulative experience, we would like to make a few comments about some of the issues that A M W Porter1 has addressed. We were quite surprised at the apparently high incidence of EHS in the British army. We believe that there is no contradiction between the vigorous demands required in military training, and the safeguarding of the soldier’s life. Motivation is very important in the military, and soliders tend to exert themselves to the limit of their physiological ability. Therefore, commanding officers should be aware of their subordinate’s ability, monitor them during training, and recognise potential risk factors for heat stroke. During the 1950s, the incidence of EHS in the Israel Defense Forces (IDF) was high, but due to actions taken by the IDF Medical Corps, that incidence has been reduced.2,3 Among the actions taken are the routine education of soldiers, commanders, and instructors regarding prevention, recognition, and treatment of EHS. Strict regulations concerning graded training prorammes, work–rest cycles during exercise under different heat loads, rehydration routine, and monitoring medical status of soldiers participating in vigorous physical activity have been implemented.3,4 An inquiry is held after every incidence of EHS, and commanders are considered responsible for any mishap occurring in their unit. Soldiers surviving EHS undergo a standard heat-tolerance test 6–8 weeks after their injury.4 A normal thermoregulatory response results in the return of the soldier to training. If the thermoregulatory response is abnormal (about 5% of the cases), the
THE LANCET • Vol 355 • June 3, 2000
For personal use only. Not to be reproduced without permission of The Lancet.
COMMENTARY
CORRESPONDENCE Exertional heat illness Sir—A M W Porter (Feb 12, p 569)1 describes a typical case of exertional heat illness (EHI), which led to the death of a young British officer-cadet. He rightly raises several points of concern in that context. In analysing events associated with the initial collapse of the cadet, Porter efficiently tackles issues concerning the protocols of the Royal Army Medical Corps, military tactics in marching laden foot soldiers in the battlefield, and the attitude of instructors and platoon commanders towards cadets lagging behind squads during field training. However, the points relating to the pathophysiology of the condition and its intervention deserve some critical discussion because they represent the focus of the impact’s seriousness on such individuals worldwide, not only in the British army. While the irrelevance of dehydration is rightly pointed out, the emphasis on occlusive clothing hindering sweat evaporation as a primary cause of collapse from EHI is an oversimplification. Also, it is true that the preoccupation of medical officers and instructors with water intake is a dangerous distraction from the real issue. But so is Porter’s statement on cooling. It is surprising that external cooling still occupies a central position in the management of heat illnesses, when it is known to have adverse effects on skin circulation, which is the main mechanism of coresurface heat dissipation. Citing a 1967 reference2 Porter adopts, and recommends, an outdated management approach. The Royal Military Academy in Britain may have been correct in not adopting the mechanical approach we, in Mecca, Saudi Arabia, used to practise for many years; that is exposing the patient to vigorous cooling procedures. Immediate vigorous cooling will result in shivering, which will aggravate core temperature load. Sympathetic nervous system impulses are known to cause the smooth muscles of the tunica media of the skin arterioles to constrict in response to several factors, especially hypovolaemia and hypotension. Hypothalamic signals inhibit these impulses, thereby facilitating
1992
vasodilation and sweating. Excessive external cooling of heatstroke patients causes shivering, even if their core temperature is over 40°C, and they do not sweat. Although Porter does not specify how the core temperature (42°C) was measured, presumably it was via the rectum. Rectal temperature (RT) is becoming increasingly criticised as the main criterion of recovery to be targeted during treatment of heatstroke.3 Measurement of tympanic membrane temperature is more accurate in reflecting that of the hypothalamus than RT. Porter may be right in criticising the statement ascribed to the British army’s legal representative that “no one can call off a march in Kosovo”, but if it were to address the issue on an international scale, the statement could very well withstand scrutiny. As for Mecca pilgrims it is true that no one can call off the Hajj march in Mecca. Several armies, worldwide, may also face a similar situation, where laden foot soldiers may have to alternate fast marching with running for a distance. This is the case, for instance, in open plains such as Middle Eastern deserts, particularly if air raids pose a constant threat to uncovered ground troops. I have worked with pilgrims doing the annual Hajj rituals in Mecca who develop heat illness, and have established several facts that have led to novel approaches to its management. Among these is the cold intravenous infusion method, which has proved effective as a method of choice for treating people with mild heat exhaustion,4 as well as acute heatstroke.5 This method is practical for use in scattered field stations; convenient for Hajj and, probably also, in military situations. Amin Kashmeery Biomedical Ethics Programme, Oxford Academy for Advanced Studies, Oxford OX4 1UT, UK (e-mail: [email protected]) 1
2
3
Porter AMW. The death of a British officercadet from heat illness. Lancet 2000; 355: 569–71. Shibolet S, Coll R, Gilat T, et al. Heatstroke: is clinical picture and mechanism in 36 cases. Q J Med 1967; 36: 525–48. Ash CJ, Cook JR, McMurry TA, et al. The
4
5
use of rectal temperature to monitor heatstroke. Mo Med 1992; 89: 283–88. Kashmeery AMS. Physiological studies on heat exhaustion victims among Mecca Pilgrims: response to relevant hormones, and effect of cold iv infusion on recovery. Acta Medica Austriaca 1995; 1/2: 16–22. Kashmeery AMS. Cold iv infusion vs body cooling unit in heatstroke treatment. Int J Health Sciences 1995; 6: 195–200.
Sir—Research into exertional heat stroke (EHS) has been carried out at the Heller Institute of Medical Research, Tel Hashomer, Israel, for over 40 years, so based on our cumulative experience, we would like to make a few comments about some of the issues that A M W Porter1 has addressed. We were quite surprised at the apparently high incidence of EHS in the British army. We believe that there is no contradiction between the vigorous demands required in military training, and the safeguarding of the soldier’s life. Motivation is very important in the military, and soliders tend to exert themselves to the limit of their physiological ability. Therefore, commanding officers should be aware of their subordinate’s ability, monitor them during training, and recognise potential risk factors for heat stroke. During the 1950s, the incidence of EHS in the Israel Defense Forces (IDF) was high, but due to actions taken by the IDF Medical Corps, that incidence has been reduced.2,3 Among the actions taken are the routine education of soldiers, commanders, and instructors regarding prevention, recognition, and treatment of EHS. Strict regulations concerning graded training prorammes, work–rest cycles during exercise under different heat loads, rehydration routine, and monitoring medical status of soldiers participating in vigorous physical activity have been implemented.3,4 An inquiry is held after every incidence of EHS, and commanders are considered responsible for any mishap occurring in their unit. Soldiers surviving EHS undergo a standard heat-tolerance test 6–8 weeks after their injury.4 A normal thermoregulatory response results in the return of the soldier to training. If the thermoregulatory response is abnormal (about 5% of the cases), the
THE LANCET • Vol 355 • June 3, 2000
For personal use only. Not to be reproduced without permission of The Lancet.