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.
