Environmental



Environmental





Some basic environmental facts:



  • When we speak of elevation (high altitude), we generally mean > 8,000 ft above sea level, although high altitude is anything > 5,000 ft.


  • A person gets colder faster in water.


  • Hypothermia is also a summertime problem.


  • Hyperthermia has a myriad of causes besides environmental.


  • When unable to explain neurologic problems or constitutional symptoms, think CO.


5.1 Altitude (AMS, HAPE, HACE)

Am J Emerg Med 1985;3:217; Emerg Med Clin N Am 1984;2:503; Nejm 2001;345:107

Cause: Being above altitude (8,000-10,000 ft above sea level) with or without appropriate acclimatization. To prevent: “Climb high, sleep low.” (Aviat Space Environ Med 1976;47:512; N Z Med J 1998;111:168)

Epidem: Getting to altitude is easier today than in the past, even extreme altitude (18,000 ft above sea level) is attainable at a cost.

Pathophys:



  • Hypoxia is the problem, with the partial pressure of O2 decreasing as we attain higher elevations. Initial hyperventilation—due to decreased PaO2—is blunted by an ensuing respiratory alkalosis. Peripheral vasoconstriction leads to central
    venous pooling, which causes a diuresis and increasing osmolality. Pulmonary hypertensive tendencies (Adv Exp Med Biol 1999;474:93) will be exacerbated by altitude due to the global pulmonary hypoxia, and perhaps pulmonary vasoconstrictors such as endothelin-1 (Circ 1999;99:2665). Cerebral blood flow will increase in an attempt to increase oxygen flow to the brain, yet this increase in cerebral blood volume may lead to an increase in intracranial pressure. Perhaps this is due to edema and ischemia (J Appl Physiol 1995;79:375). Cerebral blood flow is important in high altitude cerebral edema, but probably not the significant physiologic problem in Acute Mountain Sickness (J Appl Physiol 1999;86:1578).


  • Acclimatization may offset some of the problems with attaining altitude, but this is not always certain. Climb high, sleep low—with no more than 2,000 to 2,500 ft increase being allowed in altitude on a single day.


  • The three major problems with altitude are acute mountain sickness (AMS), high altitude pulmonary edema (HAPE) (Wilderness Environ Med 1999;10:88), and high altitude cerebral edema (HACE) (Wilderness Environ Med 1999;10:97).

Sx:



  • AMS: Headache, fatigue, nausea, vomiting, anorexia.


  • HAPE: Same as AMS with cough and dyspnea on exertion.


  • HACE: Same as AMS and HAPE with change in mental status.

Si:


Crs: Rapid physiologic decline in all categories unless rapid diagnosis and treatment.









Table 5.1 AMS Self Assessment























































































Headache

0

None at all

1

A mild headache

2

Moderate headache

3

Severe headache, incapacitating


Gastrointestinal symptoms

0

Good appetite

1

Poor appetite or nausea

2

Moderate nausea or vomiting

3

Severe, incapacitating nausea and vomiting


Fatigue and/or weakness

0

Not tired or weak

1

Mild fatigue/weakness

2

Moderate fatigue/weakness

3

Severe fatigue/weakness, incapacitating


Dizziness/lightheadedness

0

None

1

Mild

2

Moderate

3

Severe, incapacitating


Difficulty sleeping

0

Slept as well as usual

1

Did not sleep as well as usual

2

Woke many times, poor night’s sleep

3

Could not sleep at all


Total


(Score of 3 or more consistent with AMS)


Cmplc: AMS may progress to HAPE or HACE or both, and symptoms may worsen with use of ethanol, respiratory depressants, inadequate fluid intake, and overexertion.

Diff Dx: Hypothermia, dehydration, drug side-effect or OD (specifically CO poisoning), infection, PE, CVA, diabetic reaction, or simply fatigue or bronchitis.

Scoring System: Lake Louise AMS Scoring System (Hypoxia and Molecular Med 1993;66:272; Aviat Space Environ Med 1995:963). See Table 5.1.

Lab: None for mild episodes.

More severe episodes, begin treatment and gather the following: metabolic profile, glucoscan, ABG, CO level, CBC with
diff, CXR, EKG, UA with pan culture if ID evaluation considered, head CT without contrast if CNS insult considered, ethanol level or urine toxic screen, if drugs of abuse considered.

N.B. Low resting SaO2 is a risk factor for developing AMS and HAPE (Aviat Space Environ Med 1998;69:1182).

Emergency Management:


Mild AMS will resolve with some descent (1,000 ft), further evaluation per patient symptoms. All other cases should do the following:


HAPE:



  • Loop diuretics such as furosemide 60-80 mg iv, paucity of data.



  • Nifedipine 10 mg po, data equivocal (Med Sci Sports Exerc 1999;31:S23).


  • Hydralazine10 mg iv or phentolamine, data equivocal (Int J Sports Med 1992;13:S68)


  • Consider CPAP (Chest 2003;123:49).


  • Whether narcotics facilitate splanchnic pooling is equivocal, and if using for anxiolysis and wish to avoid inducing hypotension, narcotic of choice would be fentanyl 25 µg iv in an adult every 10 min—obviously use with caution in those with respiratory distress.

HACE:



  • Consider mannitol and loop diuretics—data equivocal.

Prevention:



  • Acetazolamide, Dexamethasone, good hiking habits, Salemterol Inhaler 125 µg q 12 hr (Nejm 2002;364:1631)


5.2 Electrical Injury

Emerg Med Clin N Am 1992;10:211; Ann EM 1993;22:378; J Emerg Med 1999;17:977; 2000;18:181; 2000;18:27

Cause: Children playing around electrical sockets or broken electrical cord; non-grounded tools; lack of appropriate barrier secondary to material breakdown, sweat, or water.

Epidem: 3-5% of burn center admissions, 1000 deaths/yr (Ann EM 1993;22:378)

Pathophys: More than 1000 volts is significant to humans, with as little as 20 mAmps causing significant morbidity if alternating current. Ohm’s law: amperage = voltage/resistance. The electrical injury can cause conduction problems in nerve or cardiac cells, as well as thermal destruction.

Sx: Tingling in body part in contact, inability to relax grip, shortness of breath, localized pain.


Si: Tissue destruction, respiratory distress, arrhythmias, mental status changes, paralysis, or sudden death.

Crs: Variable

Cmplc: Sudden death from delivery of current on ventricular repolarization phase—analogous to R on T phenomenon. Children who bite electrical cords may have delayed labial artery hemorrhage resulting from sloughing mucosa as underlying tissues heal—delay may be as much as 2 wk.

Lab:

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Jul 21, 2016 | Posted by in EMERGENCY MEDICINE | Comments Off on Environmental

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