Internal Medicine Correlations and Clinical Scenarios (CCS) USMLE Step 3

CASE 9: Drowning and Hypothermia

Setting: ED

CC: “We found him in the water off side of the boat.”

VS: BP: 92/60 mm Hg; P: 45 beats/minute; T: 88°F; R: 32 breaths/minute

HPI: A 52-year-old man was at a party on his boat when he was noticed missing. The boat was on the dock in only about 12 feet of water. The patient has been drinking alcohol for several hours before what seemed to be slipping off the side of the boat and falling into the water. It is not clear how long he was in the water before his friends called 911.

PMHx/Medications: none

What is the cause of death in hypothermia?

a. Seizure

b. Arrhythmia

c. Rhabdomyolysis

Answer b. Arrhythmia

The cardiac conduction system is made extremely irritable by hypothermia. The ECG will show bradycardia or “Osborn J waves,” which look similar to ST-segment elevation. Although hypothermia decreases cerebral functioning, it does not cause seizures. Hypothermia causes coma. Cold can cause muscle breakdown and rhabdomyolysis, but this is not as common a cause of death as interfering with cardiac conduction.

Orders:

Image Oxygen

Image Oximeter

Image ABG

Image Chest x-ray

Image ECG

PE:

Image General: lethargic, intoxicated and short of breath

Image Neurologic: incomplete examination

Image Chest: rhonchi bilaterally

Image Cardiovascular: no murmurs

Saltwater

• The osmolarity is 2700 mOsm/kg.

• It draws water into the lungs from the vasculature.

• It washes away surfactant.

Freshwater

• High volume causes hemolysis.

• It creates hypotonic blood.

• It washes away surfactant.

Move the clock forward only 1 to 2 minutes to get the results of oximeter.

Hypothermia: Lethargy + Dyspnea = Endotracheal Intubation

Hypothermia

• Decreases oxygen consumption

• Decreases CO2 production

• Protects heart and brain from hypoxia

• Slows heart rate (diving reflex)

Report:

Image Oximeter: 88% saturation

Orders:

Image Endotracheal intubation

Image Transfer to ICU

Image Warmed, humidified air

Image External rewarming: blankets, heating pads, warm IV fluids

Image CHEM-7, CBC

Image Urine toxicology screen, alcohol level

Most drowning and hypothermia deaths

• Are related to intoxication

• Happen in less than 12 feet of water

Report:

Image ABG: pH 7.32; PCO2 48 mm Hg; PO2 55 mm Hg

Image Chest x-ray: ARDS, atelectasis

Image ECG: Osborn J waves (Figure 11-5)

Remember that on CCS, the tests are considered done instantly, so even though the report is available after rewarming has started with warm IV fluids, blankets, and heating pads, the ECG does not reflect the use of these treatments yet.

image

Figure 11-5. Electrocardiogram (ECG) strip from a patient with a temperature of 25°C (77°F) showing atrial fibrillation with a slow ventricular response, muscle tremor artifact, and Osborn (J) wave (arrow). (Reproduced with permission from Tintinalli JE, et al. Tintinalli’s Emergency Medicine, A Comprehensive Study Guide, 7th ed. New York: McGraw-Hill; 2011.)

Atelectasis

• It causes the loss of airway volume.

• It can be caused by loss of surfactant.

• The small airways collapse first.

Ineffective Therapies in Drowning

• Steroids

• Antibiotics

Move the clock forward 10 minutes to see the effect of rewarming and mechanical ventilation. Both of these will have an immediate effect.

PE:

Image VS: BP: 104/64 mm Hg; P: 58 beats/minute; T: 94°F; R: 24 breaths/minute

Image Neurological: The patient is much more alert.

Image Chest: rales/rhonchi diffusely bilaterally

Both saltwater and freshwater create noncardiogenic pulmonary edema.

Reports:

Image CHEM-7, CBC: BUN 24 g/dL (increased); hematocrit 50% (increased)

Image Urine toxicology screen: negative

Image Alcohol level: 340 mg/mL (legally “drunk” >100 mg/mL)

Saltwater aspiration draws free water into the lungs.

• Hemoconcentration raises hematocrit concentration.

• BUN level is increased (pre-renal azotemia).

• Decreased volume increases antidiuretic hormone (ADH).

• ADH stimulates urea transporters in the kidney.

• More urea is absorbed.

As you move the clock forward, there is no way to predict the amount of recoverability of the neurological status of the patient. The benefit of rewarming will become clear right away, but the degree of recovery from the hypoxia of drowning is impossible to predict.

Orders:

Image Vital signs

Image ECG

On CCS, the end notice—“This case will end in 5 minutes of real time”—is the same no matter how well or badly you manage the patient. This can be very disconcerting because you do not know precisely how you did. The closest thing you will get to feedback is the “Interval History.”

Reports:

Image VS: BP: 112/74 mm Hg; P: 68 beats/minute; T: 98°F; R: 18 breaths/minute

The patient is more alert.

ECG: normal sinus rhythm at 68 beats/minute; resolution of J waves

There is no maximum rate of rewarming.



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