Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Job Classification

In most duration tables, five job classifications are displayed. These job classifications are based on the amount of physical effort required to perform the work. The classifications correspond to the Strength Factor classifications described in the United States Department of Labor's Dictionary of Occupational Titles. The following definitions are quoted directly from that publication.

Sedentary Work Exerting up to 10 pounds (4.5 kg) of force occasionally and/or a negligible amount of force frequently or constantly to lift, carry, push, pull, or otherwise move objects, including the human body. Sedentary work involves sitting most of the time, but may involve walking or standing for brief periods of time. Jobs are sedentary if walking and standing are required only occasionally and other sedentary criteria are met.

Light Work Exerting up to 20 pounds (9.1 kg) of force occasionally and/or up to 10 pounds (4.5 kg) of force frequently, and/or negligible amount of force constantly to move objects. Physical demand requirements are in excess of those for Sedentary Work. Light Work usually requires walking or standing to a significant degree. However, if the use of the arm and/or leg controls requires exertion of forces greater than that for Sedentary Work and the worker sits most the time, the job is rated Light Work.

Medium Work Exerting up to 50 (22.7 kg) pounds of force occasionally, and/or up to 25 pounds (11.3 kg) of force frequently, and/or up to 10 pounds (4.5 kg) of forces constantly to move objects.

Heavy Work Exerting up to 100 pounds (45.4 kg) of force occasionally, and/or up to 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Very Heavy Work Exerting in excess of 100 pounds (45.4 kg) of force occasionally, and/or in excess of 50 pounds (22.7 kg) of force frequently, and/or in excess of 20 pounds (9.1 kg) of force constantly to move objects.

Heat Exhaustion


Related Terms

  • Heat Prostration

Differential Diagnosis

  • Drug-induced fluid loss
  • Fever from infection
  • Heatstroke
  • Hypothalamic infarct
  • Malignant hyperthermia

Specialists

  • Emergency Medicine Physician
  • Internal Medicine Physician

Comorbid Conditions

Factors Influencing Duration

The severity of the heat exhaustion, certain pre-existing medical conditions, work conditions (ambient temperature), and the individual's job requirements influence the length of disability.

Medical Codes

ICD-9-CM:
992.3 - Effects of Heat and Light, Heat Exhaustion, Anhydrotic; Heat Prostration Due to Water Depletion
992.4 - Effects of Heat and Light, Heat Exhaustion Due to Salt Depletion
992.5 - Effects of Heat and Light, Heat Exhaustion, Unspecified; Heat Prostration NOS

Overview

Heat exhaustion is an acute heat-related illness characterized by dehydration and elevated body temperature. It occurs when the body can no longer adequately cool itself due to extreme environmental conditions or excess heat production, as during exercise.

This heat illness and other heat syndromes, such as heat stroke, occur most frequently when the air temperature rises above 90° F (32.2° C) and humidity is greater than 60%. Heat exhaustion is seen most frequently during the first few days of a heat wave. This is because the body's cooling mechanism takes about 7 to 14 days to adapt to high environmental temperatures. Until adaptation takes place, the body is inefficient at cooling and can easily become overheated and dehydrated when exposed to high temperatures for an extended period of time.

Heat exhaustion can progress quickly to a more serious form of heat illness called heat stroke. Heat stroke occurs in two forms. One is exertional heat stroke, which typically occurs in healthy, younger individuals exercising at ambient temperatures above 90° F (32.2° C). The other is nonexertional heat stroke, which usually occurs either at rest or during ordinary activities in older individuals with pre-existing chronic illnesses, especially heart disease.

Incidence and Prevalence: In an average year in the US, about 175 to 200 individuals die from heat-related disorders, including heat stroke; this number increases to over 1,500 during heat waves (Kunihiro).

Source: Medical Disability Advisor



Causation and Known Risk Factors

Heat exhaustion with water depletion can occur in any individual who fails to take in enough fluids or is taking a medication to rid the body of water (diuretic). Other circumstances that can increase the risk of heat exhaustion include exercising in a hot environment, lack of air conditioning or proper ventilation, inappropriate clothing (e.g., occlusive, heavy, or vapor-impermeable), decreased fluid intake, certain pre-existing illnesses, use of diuretics, and spending extended time in hot, enclosed environments (e.g., inside tents or autos in the sun, in hot tubs, or in saunas).

Heat-related illnesses occur with equal frequency in males and females. Infants and the elderly are more prone to heat exhaustion as a result of inadequate body temperature regulation (thermoregulatory) mechanisms. Geographically, heat exhaustion and other heat-related illnesses occur most frequently in areas with high air temperatures.

Source: Medical Disability Advisor



Diagnosis

History: The individual usually reports recent exposure to a temperature above 90° F (32.2° C) or participated in prolonged or heavy physical activity at a somewhat lower temperature. Individual may complain of headache, dizziness, weakness, thirst, fatigue, loss of appetite, or nausea and vomiting.

Physical exam: Individual appears flushed and warm and perspires heavily. He or she may be anxious or confused. An elevated temperature and a rapid respiratory rate are present.

Tests: A complete blood count (CBC) and measurement of the serum sodium, potassium, chloride, and bicarbonate (electrolytes) should be obtained.

Source: Medical Disability Advisor



Treatment

Therapy consists of moving the individual to cooler surroundings and providing rest and rehydration with fluids containing sodium and potassium. Ideally, the individual should be treated at an emergency department or urgent care clinic. If such a facility is not available, administration of sports drinks and even soda drinks can help replace fluids. Fluid replacement should be given slowly and continued for at least 6 to 9 hours or until adequate hydration is achieved. Blood pressure, pulse, temperature, and urine output are monitored to assess the severity of illness and guide fluid replacement. In severe cases, hospitalization is required for administration of intravenous fluids. Cool washcloths or ice packs may be placed on the neck, groin, or armpits to hasten cooling. Rest and fluid replacement should continue for at least 24 hours.

Source: Medical Disability Advisor



Prognosis

With prompt treatment, individuals with heat exhaustion should have full recovery with no residual effects.

Source: Medical Disability Advisor



Complications

Heat exhaustion can quickly progress to heat stroke, which is associated with low blood pressure, shock, organ dysfunction, and even death.

Source: Medical Disability Advisor



Ability to Work (Return to Work Considerations)

Individuals should avoid activity in the heat for approximately 24 to 48 hours following heat exhaustion.

The Occupational Safety and Health Administration (OSHA) and National Institute of Occupational Safety and Health (NIOSH) have published guidelines regarding work accommodations to prevent heat-related illness. In general, recommendations include scheduling heavy work for the coolest part of the day, taking frequent rest breaks in cool areas, providing adequate amounts of cool water for workers, and assigned those at greatest risk of heat-related illnesses to light duty (the obese, the elderly, and those not acclimated to the heat or on medication).

Source: Medical Disability Advisor



Failure to Recover

If an individual fails to recover within the expected maximum duration period, the reader may wish to consider the following questions to better understand the specifics of an individual's medical case.

Regarding diagnosis:

  • Has individual been exposed to air temperature over 90° F (32.2° C) with humidity greater than 60%?
  • Did individual fail to drink adequate amounts of fluid? Is individual taking diuretics?
  • Was individual wearing inappropriate clothing?
  • Does individual have inadequate thermoregulatory mechanisms?
  • Does individual complain of a headache, dizziness, fatigue, or weakness? Is there increased thirst, loss of appetite, or nausea and vomiting? Does individual appear warm and flushed? Is individual perspiring heavily? Is individual anxious or confused?
  • Was body temperature elevated? Were rapid respirations evident?
  • Was a CBC and electrolyte test performed?

Regarding treatment:

  • "In the field" was individual moved to cooler surroundings? Were sports drinks given? Were ice packs to the neck or groin used to facilitate cooling?
  • Was individual then taken to the emergency room? Was IV fluid replacement needed?
  • Was it necessary to hospitalize individual?

Regarding prognosis:

  • Can individual's employer accommodate any necessary restrictions?
  • Does individual have any conditions that may affect ability to recover?
  • Did individual have any complications such as heat stroke associated with low blood pressure, shock, or organ dysfunction?

Source: Medical Disability Advisor



References

Cited

Kunihiro, Amy, and James Foster. "Heat Exhaustion and Heatstroke." eMedicine. Ed. Dan Danzl. 17 Sep. 2004. Medscape. 30 Oct. 2004 <http://emedicine.com/emerg/topic236.htm>.

Source: Medical Disability Advisor






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