Grey's Anatomy (ABC) has recently presented a series of episodes that has examined the management of a situation of mass casualty. However, in a plot twist that has been milked for a couple weeks, our heroine, Dr. Meredith Grey, had been pushed into the Pacific Ocean after skillfully tying off a major vessel in a trauma patient, tourniquet unnecessary. After rescue from drowning by her dashing suitor, Dr. Derek 'McDreamy' Shepherd, she now presents to good old Seattle Grace... hypothermic and unresponsive. What ever shall we do?
Remember, a moist, cold Meredith isn't dead... until she's warm and dead.
Are there any recommendations for how to remove a drowning victim out of the water?
It has been suggested that patients be lifted in the prone position.
Immersion in water results in an increase in cardiac output due to decreased resistance to flow. Removing a person from water in an upright position can cause venous pooling from circulatory collapse that is attributed to deaths seen within minutes of rescue in responsive patients.
What measures should be done at the scene of a drowning victim?
Wet clothing should be removed and the patient wrapped in thick blankets.
Don't waste time rewarming patient.
Transfer patient to facility that has available extracorporeal rewarming.
Intubate the patient if unconscious.
Continuous chest compressions should be applied for cardiopulmonary arrest.
Protect C-spine
What about defibrillation at the scene?
When the myocardium is cold, this will be ineffective...
What factors have favorable outcomes with near drowning?
Submersion less than 5 minutes
Heart beat that is restored immediately
Immersion in ice cold water (less than 5 degrees C)
Buoyancy devices decrease aspiration risk
What factors have possible complications?
Fresh water causes more V/Q mismatch than salt water
River water causes potential risk of infection (leptospirosis)
Shallow water raises possibility of fractures
What is hypothermia?
Core body temperature below 35 degrees C
Mild: 32-35 degrees C (89.6-95.0 F)
Moderate: 28-32 degrees C (82.4-89.6 F)
Severe: <28 degrees C (<82.4 F)
What is primary hypothermia?
Decrease in core temperature from environmental stress
What is secondary hypothermia?
Unintentional hypothermia from abnormal thermoregulation.
Risk factors include age, hypothyroidism, hypoadrenalism, trauma, hypoglycemia, anesthetics.
Below what temperature is shivering abolished?
Somewhere between 30-33 degrees C.
What happens to the cardiac conduction system with moderate to severe hypothermia?
Below 30 degrees C atrial fibrillation, bradycardia, and ventricular dysrhythmias become common.
Below 25 degrees C asystole occurs.
What is the eponym attributed to hypothermia-related gastric erosions?
Wischnevsky's ulcers
What does mild, postoperative hypothermia do to surgical wound infection rates?
-1.9 degrees C core hypothermia triples the incidence of SSIs and increases the hospital stay by 20%
What is the mortality rate for trauma patients with moderate primary hypothermia?
Approximately 20%
Does intentional hypothermia (32-33 degrees C) protect against severe traumatic brain injury?
No. A multicenter randomized clinical trial for GCS 3-7 patients showed no difference in mortality (28% vs. 27%) and greater hospital days and complications when comparing 48hrs of intentional hypothermia with normothermia.
Does intentional hypothermia protect against complications of cardiac arrest?
Yes. A prospective multicenter randomized clinical trial of patients in ventricular fibrillation found cooled patients had better neurologic outcomes (55% vs 39%), lower mortality (41% vs 55%), but higher rates of bleeding, sepsis, and pneumonia.
What is the triad of death?
Acidosis, Hypothermia, and Coagulopathy
How does hypothermia cause coagulopathy?
1. Decrease in clotting factor enzymatic function
2. Qualitative platelet dysfunction
What is passive external rewarming?
Allowing the ambient air to spontaneously warm the patient.
What is active external rewarming?
Placing blankets, heating pads, bair huggers, or applying heat lamps on the patient
Immersing the patient in warm water
What are methods of active core rewarming?
Heated intravenous fluids
Heated bladder, gastric, or colonic lavage
Heated peritoneal or thoracic lavage
Heated humidified inhaled air
Extracorporeal circulatory rewarming
What maximum temperatures are safe for intravenous rewarming?
Blood heated to 42 degrees C
Crystalloids heated to 65 degrees C
What are methods of extracorporeal circulatory rewarming?
1. Cardiopulmonary bypass
2. CAVR - continuous arteriovenous rewarming
What is a limitation of cardiopulmonary bypass?
The need for systemic anticoagulation
What does CAVR involve?
Connecting the patient to a counter-current heat exchange circuit but relying on the intrinsic cardiac pump
How much effort does it take to warm a 70kg patient by 1 degree C?
Using 41 degree C humidified inspired air - more than 6 hours
Using 44 degree C body cavity lavage - 14 L of fluid
Using 40 degree C extracorporeal rewarming - 10 times faster than lavage
What is the pathophysiology of "rewarming shock"?
Peripheral rewarming results in peripheral vasodilatation. In the absence of adequate volume resuscitation this will result in decreased cardiac output.
What is "afterdrop"?
A decrease in core central temperature after cold peripheral blood returns to circulation secondary to vasodilation from rewarming measures.
Late... SG
Sources:
Harries M. Near drowning. BMJ 2003; 327: 1336-1338.
Jurkovich GJ. Environmental Cold-Induced Injury. Surg Clin N Am 2007; 87: 247-267.
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