WORK-RELATED HEAT STRESS Mustafa Khogali Dec.2006 INTRODUCTION Is our climatic environment a threat to our physiological adaptation? Animals are better suited! Humans attained sophisticated control But? Both are suited to risk of HEAT ILLNESS? Evolution of Thermo.Reg.Sys ↑ H. Elimination V H. Conservation Survival► Maintenance of B.T 37˚C B.T. EQUILIBRIUM a. b. Two Physiologic Mechanisms: Cardiopulmonary Sweating ↓ Evaporation ↑SKBF 1. Factors Influencing H. S. Climate / Env. Conditions. Demands of work. Clothing. Personal characteristics. FACTORS MODIFYING HEAT TOLERANCE Physiological or pathological changes that alters body’s heat production or heat loss capacity modify tolerance of hot environment: 1. Physical Fitness (Exercise) 2. State of Hydration 3. State of Acclimation 4. Endotoxins 5. Age 6. Drugs 7. Others HEAT STRESS Are there safe limits?? Wide variability in Human TL. Complexity of H.Exchange. H.S.INDICES Rational: S=M±C±R-E EMPIRICAL : Subjective/Objective. ET WBGT P4SR WBGT a) OUTDOOR = WBGT = 0.7 WB + 0.2 GT + 0.DB b) INDOOR = WBGT = 0.7 WB + 0.3 GT PERMISSIBLE HEAT EXPOSURE THRESHOLD LIMIT VALUES (WBGT °C) WORK-REST CYCLE (% OF EACH HOUR) LIGHT WORK LOAD MODERATE LIGHT CONTINUOUS WORK 30.0 26.7 25.0 75 : 25 30.6 28.0 25.9 50 : 50 31.4 29.4 27.9 25 : 75 32.2 31.1 30.0 ADAPTED FROM ACGIH: THRESHOLD LIMIT VALUES FOR CHEMICAL AND PHYSICAL AGENTS AND BIOLOGICAL EXPOSURE INDICES, 1992-1993, CINCINNATI, 1992, THE CONFERENCE. * LIGHT = 200 Kcal/hr or less; Kcal/hr Moderate = 201-300 Kcal/hr; Heavy = above 300 HEAT STRESS: PRINCIPAL SYSTEMIC RESPONSES 1. Sweating 4. CNS 2. Cardiovascular Status 5. Hematology 3. Metabolic status Hormone 6. MEASUREMENT OF BODY T ORAL To RECTAL Tr TYMPANIC Tt ESOPHAGEAL Te Skin Ts 1. HEAT DISORDERS H.Syncopy H.Cramps H.Exhaustion H.Stroke 2. H.Induced Illnesses T67 EFFECTS OF HEAT AND LIGHT T67.0 HEAT STROKE AND SUN STROKE T67.1 HEAT SYNCOPE T67.2 HEAT CRAMP T67.3 HEAT EXHAUSTION, ANHYDROTIC T67.4 HEAT EXHAUSTION DUE TO SALT DEPLETION T67.5 HEAT EXHAUSTION, UNSPECIFIED T67.6 HEAT FATIGUE, TRANSIENT T67.7 HEAT OEDEMA T67.8 OTHER EFFECTS OF HEAT AND LIGHT T67.9 EFFECTS OF HEAT AND LIGHT, UNSPECIFIED DEFINITION: ( CLASSIC TRIAD ) Heat stroke is a state of thermoregulatory failure characterised by: (A) CNS Dysfunction: (Poor limb coordination, delerium, convulsions, grand mal seizures and coma). (B) Generalised Anhidrosis: (C) A Rectal Temperature Above 40.6 °C INTERACTING MECHANISM AND OUTCOME IN HEAT STROKE PATIENTS AGE, DRUGS CHRONIC DISEASES ENVIRONMENT METABOLISM V V HEAT AGAIN V V VASODILATION V SWEATING T FLUID LOSS V ACIDOSIS HYPOXIA V RHABDO-MYOLSIS V V V V SHOCK RISE IN BODY CORE TEMPRATURE V V MYOCARDIAL ACUTE RENAL DYSFUNCTION FAILURE CESSATION OF SWEATING DIC CIRCULATORY FAILURE CNS HOST FACTORS REPORTED TO INCREASE RISK OF HEAT STROKE Lack of acclimitization Obesity Lack of physical fitness Fatigue Lack of sleep Dehydration Febrile Illness Acute and convalescent infections Fever following immunization Conditions affecting sweating Skin diseases Acute or chronic alcoholism Chronic diseases; e.g. diabetes, cardiovascular disease Lesions of hypothalamus, brainstem, and cervical part of the spinal cord Potassium deficiency Sustained output of muscular metabolic heat Increased susceptibility due to biological variability MANAGEMENT OF HEAT STROKE CRITICAL MANAGEMENT STRATEGIES Recognition of Hyperthermia Rapid Effective Cooling Supportive Care Observation of H.R. Complications of Tissue Injury COOLING MODALITIES 1. Ice water immersion 2. Evaporation cooling (FANS) 3. Ice packs 4. Lavage: peritoneal, rectal, gastric 5. Alcohol sponge bath 6. Cardiopulmonary by pass OBJECTIONSTO ICE WATER IMMERSION 1. Intense peripheral vaso constriction 2. Induction of shivering 3. Extreme discomfort of patient 4. Discomfort of medical attendance 5. Difficulty: Cardiopulmonary resuscitation 6. Difficulty: Monitoring vital signs 7. Unpleasant and unhygienic conditions ALTERNATIVE METHOD Evaporative cooling from warm skin M.B.C.U. Groups at Risk WORKERS : In hot industries. : Outdoor occupations. : Who wear protective clothing ELDERLY : Those with chr.diseases. EXERCISING CHILD MAKKAH PILGRIMS (In hot season) Occup.H.Exposure OUTDOOR: Agric./Farming;construction Cane sugar cutting Oil and gas drilling Fire fighting etc. OCC.H.EXPOSURE--2 INDOOR: Bakeries Forging/Foundries Engine room Steel/Iron/Glass manufacture Laundries etc. Thermal Problems in Sport Outdoor sport activities Mass Participation (Marathons) (Aerobic Capacity imp) MAKKAH PILGRIMAGE H.Illness alert prog. (HIAP) Strategies based on triad of Prev. Primary Secondary Tertiary PRIM.PREV. Adequate/Eff.Eng.Design ↓ Comfortable cooling Good ventilation ↓Workload Education/Awareness SECOND.PREV. a) b) Preselection/Acclimation PE Med Ex.►Employees Preplac.Med Ex.► Sport Appropriate Adm.Management (Work-rest cycle + Fluids) Information to Physician Detailed Job Description:* Length/Duration of work * Shift system * Freq./duration of rest * Env.T Pre.Placement Exam a) Medical History Occupational History Past History of H.R.I Behav.habits b) Physical Exam Tert.Prev. Diag.H.I. Syndromes Facilities Training Diff.Categories Protocol of Management WORK PRACTICE ENV.ASSESSMENT. PROG.OF ACCLIMATIZATION. ADEQUATE WATER SUPPLY. FIRST AID TRAINING. GENERAL TRAINING FOR HEALTH SAFETY. ADAPTIVE WORK SCHEDULE. WORK-REST REGIMEN PREPLACEMENT/PERIODICAL MED.EXAM. OBSERVATION/MONITORING BY TRAINED PERSON. Alert Programs I. Permissible Heat Exposure TLV Alert Danger 0 0 II. Thermal Limit 1- Oral temperature Increase ˚c 1.5 2- Skin temperature Increase ˚c 3.0 4.0 2.5 Alert Programs Alert Danger Headache Dizziness Feeling of fatigue Insecure galt To = 38 ˚c Confusion Fast pulse To = 38.5 ˚c Disorientation Collapse Peculiar behaviour Loss of consciousness wanders around To = 40.0 ˚c III. Heat Illnesses 1. Heat Exhaustion 2. Heat Stroke To = 39.5 ˚c H. S. Training Rev. of H. S. Disorders. Risk factors of HRD. Recognition of signs or symptoms. Prev. measures to be used. Fluid replacement options. Expectations. Conclusions a. Prevention of Heat illness in both occupational and sport is crucial since they potentially lethal. b. Appreciation of Heat illness: Physician/Administrator/ Param industrial & military/Organizers. c. Principles of Prev and Management - All members of community Conclusions d. Success achieved through: Awareness and education. Acclimatization (Matching Activity α T+H). Liberal Water Replacement. Use of Proper clothing. Appropriate history of medical exam. Adoption of Heat Alert Prog.