What medical problems with torpor have been noted on Earth and how do we mediate them with the limited resources carried into space?

There are several potential complications associated with Torpor. The most significant risks are increased risk of bleeding and increased risk of infection. In addition, TH can adversely affect several other physiologic processes. It should be noted that all of the complications listed below are rare, and can be completely corrected through autonomous systems and monitoring of crewmembers if needed.

1. Torpor induces a mild coagulopathy (increased risk of bleeding). With body temperatures below 35ºC, clotting factors operate more slowly and platelets function less effectively. As a result, some bleeding is seen in up to 20% of patients treated with TH, although bleeding that needs to be treated with medication is rarely seen even in trauma patients and blood transfusions are rarely required.

No treatment is required for mild coagulopathy. Even mild bleeding from the nose and IV sites will still stop without treatment. The treatment for heavy bleeding associated with trauma would be the addition of clotting factors through the IV line and increasing the crew member’s blood volume with both IV fluids and blood products. Since the crewmembers will already have an IV line the process would require someone to just defrost and hook-up the needed product. Clotting factors and blood can be frozen for as long as 10 years. After thawing blood products are only usable for 42 days.

2. Torpor can impair white blood cell function. The incidence of significant infections is likely to increase if hypothermia is maintained longer than 24 hours. While an increase in infection rates has been noted in several studies, these infections have not been associated with any increased mortality (risk of death) and are usually easily treated.

Preventing the infection from occurring is the best and easiest method. This includes using improved sterile techniques for IV placement and care and for utilizing improving technology in antimicrobial IV equipment. IV antibiotics antibiotic are used if an infection does occur, and are easily administered in space.

3. Hypothermia slows heart conduction and can cause irregular heart beat patterns called arrhythmias, including bradycardia and QT interval prolongation. A heart rate in the 40’s is common at 33ºC, but does not require intervention if the blood pressure is in the normal range. Multiple studies show that TH is not associated with an increased need for medications to increase blood pressure. This would indicate that most cases of hypotension (low blood pressure) in TH patients are due to either injuries or shock and not Torpor itself.

Treatments for hypotension include increasing IV fluids to increase blood volume and the use of medications called “pressors” to artificially increase blood pressure, both of which can be performed easily in space.

4. Hyperglycemia (high blood sugar) due to insulin resistance has been noted during TH. IV Insulin may be needed in severely hyperglycemic patients.

5. Hypothermia leads to a “cold diuresis,” which in turn can cause hypovolemia (low blood volume), hypokalemia (low potassium), hypomagnesaemia (low magnesium), and hypophosphatemia (low phosphates). In addition, temperature fluctuations during the induction of TH and rewarming can cause potassium to move between the extracellular and intracellular compartments. Therefore, careful monitoring of volume status and measurement of basic electrolytes approximately every three to four hours during temperature manipulation should be done. This can easily be corrected with IV fluids.