Overcooling (hypothermia) – decrease in internal body temperature to 35 °C and below as a result of prevalence of a thermolysis over heat production. At an initial stage the shiver, increase of breath and heartbeat, a spasm of peripheral vessels, a disorientation, drowsiness, apathy is observed. In the subsequent oppression of activity of all bodies and systems is noted, at aggravation of a state there comes the coma and death. Overcooling is diagnosed on the basis of clinical yielded, results of measurement of basic temperature, as additional methods tool and laboratory researches are appointed. Treatment includes active and passive warming, medicamentous therapy, resuscitation actions.
Overcooling – a pathological state which can pose hazard to life of the patient. Statistically, in the USA because of a hypothermia annually perishes about 700, in Great Britain – 300, in Canada – 100 people. Experts consider that the real quantity of death from overcooling are higher as this state is not always diagnosed. Pathology is widespread everywhere, meets in northern more often and midlatitudes, the quantity of cases increases in cold season. The risk of development of a hypothermia increases at representatives of extreme age groups – babies and children of younger age, elderly and old men. In sparsely populated zones overcooling usually arises because of insufficient readiness to stay in the existing weather conditions. In the cities the victims of a hypothermia the homeless and persons who are in state of intoxication after alcohol intake become more often.
The hypothermia develops owing to the increased loss of heat which does not manage to be compensated due to heat production strengthening by an organism. Heatlosses result from carrying out, convection and evaporation. Carrying out is called direct transfer of heat from a body to the environment, convection – loss is warm at the movement of water or air in close proximity to the surface of a body, evaporation – allocation of heat with water during the sweating, breath. Distinguish four main reasons for overcooling:
- Lack of heat production. It is observed at premature children, people of senile age, patients with alimentary dystrophy, exhaustion against the background of severe injuries, sharp and chronic diseases. It is found at some hormonal frustration – a gipokortitsizm, a gipopituitarizm and hypofunction of a thyroid gland.
- Increase in heatlosses. It is noted at expansion of vessels owing to intoxication (most often – alcoholic), reception of medicines. Develops at long stay in dry cold, immersion in cold or cool water. Is defined at some skin pathologies, for example, an ichthyosis, psoriasis and eksfoliativny dermatitis. Sometimes becomes result of medical actions (when performing long surgeries, massive transfusion of cold solutions).
- Thermoregulation violations. Come to light at some diseases and traumatic damages of the central and peripheral nervous system which are followed by touch frustration (for example, at damage of large nervous trunks, paralyzes against the background of a stroke, a craniocereberal or spinal trauma, especially – high, a multiple sclerosis, tumors of TsNS, Parkinson's disease). Can arise under the influence of some toxins and medicines.
- Within critical conditions. Can be defined at a polytrauma, massive blood loss of various genesis, sharp pancreatitis, septic states, extensive burns, uraemia, diabetic ketoacidosis. It is provoked by the thermal control violations increased by chreskozhny losses of water, behavioural violations and other reasons.
Often pathology has a polietiologichesky origin. For example, at old men and bed patients at insufficient leaving the age or caused by thermoregulation violation lack of production of heat, low temperature indoors, chronic diseases matter. The most essential external factors are the ambient temperature, humidity and wind force. At stay on air without the movement at a zero temperature death comes within 10-12 hours, under similar conditions in water – in half an hour.
Influence of wind pays off on the basis of a vetro-holodovy index, there are special tables made taking into account this indicator, reflecting danger of overcooling or freezing injury under these or those weather conditions. Despite increase in risk of development of a hypothermia in process of fall of temperature, the greatest number of cases at healthy people, on observations of traumatologists, is connected with stay on the street in the conditions of low positive, but not negative temperatures that can speak insufficient vigilance, unpreparedness to environmental conditions.
Overcooling is the two-phasic process including compensation stage arising in attempt of an organism to modify violation of thermal balance, and the decompensation stage developing at failure of mechanisms of temperature regulation. In a stage of compensation the reactions of an organism directed to decrease in heatlosses and increase in production of heat are activated. The patient changes behavior (finds the shelter, puts on warm clothes, includes a heater, uses blankets and so forth). Due to narrowing of peripheral vessels and decrease in sweating losses of heat through skin decrease. The blood-groove in internals amplifies, there are involuntary reductions of muscles (a muscular shiver) providing increase in heat production. The diuresis increases. There is an emission of hormones which participate in the stressful reactions increasing protective abilities of an organism in extreme circumstances.
At inefficiency of adaptive mechanisms and further decrease in body temperature the central mechanisms of thermoregulation are broken, heat production becomes in-coordinate and inefficient. The central temperature falls below 35 °C, there are poykilotermichesky reactions, the vicious circles aggravating a condition of the patient are formed. Because of reduction of temperature intensity of fabric exchange decreases that leads to further fall of temperature and decrease in metabolism. Narrowing of peripheral vessels is replaced by their expansion that involves increase in heatlosses which provoke further dilatation of vessels.
Because of violation of activity of the nervous centers the muscular shiver stops that exponentiates temperature drop of a body and further oppression of the central mechanisms of regulation of activity of muscles. The hypothermia of the central nervous system is the reason of decrease in brain activity, consciousness violations, drowsiness, apathy as a result develop. Active actions become impossible, the patient fades that reduces chances of rescue. There comes the condition of the seeming pacification, pseudo-comfort which in the subsequent passes into a coma and comes to the end with death of the patient.
There are several classifications of overcooling. As expressiveness of manifestations not always coincides with weight of a hypothermia, for assessment of reversibility of process overcooling is systematized sometimes taking into account the central body temperature. According to such division there are four stages of pathology: three reversible (easy – 32-33 °C, moderated – 28-32 °C, heavy – 24-28 °C) and one irreversible (extremely heavy – less than 24 °C). However in clinical practice use the classification made on the basis of the prevailing compensatory reactions and including three extents of overcooling more often:
- Easy or adynamic (32-34 °C). Is followed by activation of mechanisms of heat generation, narrowing of peripheral vessels, stressful stimulation of sympathetic nervous system.
- Average or soporozny (29-32 °C). It is shown by exhaustion of compensatory mechanisms, delay of metabolism in TsNS, diskoordinatsiy work of the cortical and subcrustal nervous centers, oppression of the respiratory and warm center in a medulla, considerable deterioration or the termination of a blood-groove in peripheral vessels, it is possible – freezing injuries.
- Heavy or coma (it is below 31 °C). It is characterized by failure of mechanisms of compensation, heavy violations of exchange and serious disorders of work of brain structures, violations of work of the carrying-out system of heart, defeat of peripheral fabrics up to frosting.
At easy degree there is a fever, a muscular shiver, integuments become pale, get a cyanotic shade. "Goose-pimples" and typical violations of the speech come to light. Unsharply expressed bradycardia is noted. HELL usually without changes or is slightly raised, breath is speeded up. In the beginning the patient actively moves, undertakes measures for rescue. At continuation of action of cold of the patient becomes sluggish, apathetic. The speech, thought processes and reactions to external influences are slowed down. Superficial freezing injuries are found in certain patients.
At average degree further aggravation of bradycardia, insignificant decrease HELL and an urezheniye of breath till 8-12 respiratory movements in a minute is defined. Cyanosis of integuments amplifies, becomes especially expressed in a nose, ears, disteel departments of extremities, the probability of developing of freezing injuries increases. The amount of the emitted urine decreases because of decrease in a kidney blood-groove. The muscular shiver stops, muscles grow numb, the patient accepts the compelled pose – rounds a back, bends hands and legs, leads them to a trunk. The expressed drowsiness passes into a hypothermal dream and further into a coma, reaction to external irritants is significantly weakened, often comes to light only at painful influences. Pupils are expanded, react to light.
At heavy degree the expressed cyanosis of skin, an intensive muscular okocheneniye is found. Pulse rate decreases till 20-30 . in min., arrhythmias are defined, fibrillation is possible. Rare superficial breath is replaced periodic (A biota or Cheyn-Stokes). The office of urine stops because of development of a sharp renal failure. The patient is in a condition of a deep coma, reactions to all types of irritants are absent, weak reaction of pupils to light is possible. The repeating generalized spasms with an interval before half an hour are observed. Deep widespread freezing injuries come to light, the frosting of peripheral parts of the body (fingers, brushes, feet, parts of the face) extending in the proximal direction is possible. At decrease in the central temperature below 20 °C respiratory standstill, the termination of warm activity is defined.
In the early period emergence of fibrillation, hypostasis of a brain, hypostasis of lungs is possible. The sharp renal failure is quite often diagnosed. The probability of infectious complications increases, including – pneumonia, a surgical wound infection. Sometimes mistakes when warming become the reason of negative consequences, overheating because of failure of mechanisms of thermoregulation, falling HELL and cardiac arrest owing to reflex expansion of vessels at too bystry rise in temperature can be observed. At deep freezing injury amputation of an extremity can be required. At a number of patients in the remote period neurologic violations come to light.
The diagnosis is established on the basis of external survey, data of the anamnesis (at heavy overcooling data are established according to the eyewitnesses who found the victim, or employees of an ambulance crew) and results of measurement of body temperature. Measurement reflects superficial temperature in an axillary hollow and is not reliable criterion of existence or lack of overcooling. Measurement is taken rektalno, by means of the esophageal probe or in a nasopharynx, considering that rectal temperature can differ a little from basic, and the readings taken in a gullet can be doubtful because of the previous therapy warm air.
In modern clinical practice use the special electronic thermometers equipped with the probe, calibrated in the range of the lowered temperatures. Measurement of temperature of a fresh portion of urine is possible. An optimal variant is carrying out several measurements in different places. It is necessary to consider that falling of basic temperature is lower than critical indicators, lack of heartbeat and breath cannot be considered as the evidence of death of the patient (the survival case is described at a temperature of 9 °C, and also recovery after the termination of warm activity within 3 hours) because of the action of a hypothermia which is slowing down development of irreversible processes in fabrics. Death is verified only in the absence of life signs after warming.
For confirmation of the diagnosis along with measurement of temperature appoint the ECG on which Osborn's wave comes to light. The list of other laboratory and tool researches at suspicion of this pathology includes OAK, OAM, definition of urea, creatinine, glucose, electrolytes, the acid and main state and pH of blood, a koagulogramma, measurement HELL and an hourly diuresis, a pulsoksimetriya, a thorax X-ray analysis. At injuries of the musculoskeletal device carry out a X-ray analysis of the corresponding segment, at a possible internal injury appoint ultrasonography, KT or MPT, according to indications make a laparoscopy and other researches.
treatment should be carried out only under the supervision of a doctor. Self-treatment is unacceptable!!!
Treatment is performed by experts in the sphere of traumatology and resuscitation. Therapeutic tactics is defined by hypothermia degree, character and weight of violations of activity of an organism. In all cases it is necessary to stop urgently impact of cold, to hold events for passive warming. The patient with easy degree appoint warm drink (sweet tea), a heat bath, hot-water bottles, avoiding use of excessively heated liquids. At superficial freezing injuries apply the warming bandages extremities.
At average and heavy degree the intensive complex therapy including etiotropny, pathogenetic and symptomatic actions is necessary. Etiotropny treatment assumes passive (blankets, warm dry clothes) and active (a heat bath, applying of hot-water bottles to places of passing of large vessels) warming. Active warming is carried out, applying liquid which temperature exceeds the victim's temperature no more than on 10 °C. After increase in rectal temperature to 33-34 °C the procedure is stopped in order to avoid possible overheating against the background of yet not restored system of thermoregulation.
Along with the listed ways warming of lungs by the supply of damp air or oxygen mix which is warmed up to 42-44 °C, intravenous injections of warm solutions is effective. At resistance to the listed methods carry out a mediastinalny unleavened wheat cake, extracorporal warming of blood (a hemodialysis, kardiopulmonalny, veno-venous and arteriovenozny shunting), washings of a stomach, a bladder, a rectum, a pleural cavity warm solutions, however these techniques are accompanied by risk of development of complications therefore are not applied as a part of standard therapy.
Actions for restoration of activity of respiratory and cardiovascular systems, corrections of exchange violations are the cornerstone of pathogenetic treatment. Carry out release of airways, carry out IVL. If necessary make a defibrillation. Carry out infusional injections of a dextran, salt solutions, glucose solution with vitamins and insulin, according to indications – transfusions of plasma and plasma substitutes. Within symptomatic therapy appoint medicines for normalization of a mocheotdeleniye, increase HELL, elimination of a pain syndrome, prevention of hypostasis of lungs and a brain, correction of the existing somatic pathology. When determining the plan of medicamentous correction of a condition of the patient consider that medicines in the conditions of the expressed hypothermia can be ineffective or have unpredictable effect and have to be applied after sufficient warming. Carry out treatment of freezing injuries.
Forecast and prevention
The forecast usually (except for especially hard cases) more depends on the accompanying pathology, than on weight of overcooling. Mortality among healthy people is low. In the presence of severe injuries and somatic diseases lethality indicators sharply increase. Characteristic of this state is the possibility of restoration after the long termination of activity of vitals caused by safety effect of cooling. Preventive actions provide the choice of clothes and planning of activity out of warm shelters taking into account weather conditions, correction of the pathological states which are risk factors, providing optimum temperature condition in rooms, especially at accommodation in them of the people having predisposition to development of a hypothermia.