This is a summary table from UptoDate. There is a much much more detailed segment on this but this will get the ball rolling for many of your questions.
Initial management of hypothermia: Rapid overview of emergency management
GeneralDefinition: core temperature lower than 35°C (95°F)
Mild: 32 to 35°C (90 to 95°F)Moderate: 28 to 32°C (82 to 90°F)Severe: below 28°C (82°F)In patients who are not completely alert and oriented, measure core temperature with a low-reading, digital temperature probe if available. Measure esophageal temperature in patients with tracheal tube or supraglottic airway in place.* Standard oral thermometers do not read below 34°C (93°F).Consider hypothermia secondary to other conditions (eg, infection, hypoglycemia, adrenal insufficiency, hypothyroidism, overdose, trauma). Older adults are at higher risk. Hypothermia with associated comorbidities or trauma is considered more severe.Clinical aspectsPhysical examination
Vital signs
Mild hypothermia: tachypnea, tachycardia, hyperventilationModerate hypothermia: expect bradycardia (tachycardia suggests hypoglycemia, hypovolemia, or overdose), hypotension, hypoventilationSevere hypothermia: hypotension, cardiovascular collapseNeurological examination
Mild hypothermia: ataxia, dysarthria, impaired judgement; suspect CNS pathology if patient comatoseModerate hypothermia: CNS depressionSevere hypothermia: areflexia, comaLaboratory evaluationFor patients with moderate or severe hypothermia, studies to obtain include: fingerstick glucose, coagulation studies, CBC, basic electrolytes, BUN and creatinine, serum lactate, electrocardiogram, plain chest radiograph. Additional studies may be needed.
Clinical coagulopathy may be present despite normal measured coagulation timesIncreased hematocrit may reflect hemoconcentrationMay see low bicarbonate, suggesting anion-gap acidosis; if so, obtain venous or arterial blood gasElectrocardiogram
Rhythm abnormalities (atrial fibrillation, sinus bradycardia) may be presentIntervals (PR, QRS, and QTc) may be prolongedOsborn J waves are characteristic of hypothermia (but can occur with other conditions)
Occur at junction of QRS and ST segments, most prominent in V2 to V5Distortion of the earliest phase of membrane depolarizationComputer may misinterpret as ischemic injury patternTreatmentEndotracheal intubation may be necessary in obtunded or unconscious patients and those with bronchorrheaTreat hypotension with warmed, isotonic crystalloid (40 to 42°C) initially, vasopressors (norepinephrine preferred) if necessaryAvoid rough movements and activity, which may induce ventricular fibrillationRewarming techniques are based on degree of hypothermia
Mild hypothermia
Remove wet clothing, cover with warm blankets, keep room temperature at approximately 28°C (82°F).Provide active external rewarming, with forced air warming systems if available. Warmed blankets, heating pads, radiant heat sources can also be used. Avoid burning skin.Moderate hypothermia
Provide active external rewarming as described above.Give warmed IV fluids (40 to 42°C) and warmed humidified oxygen as adjuncts (these are not primary rewarming methods).Beware of afterdrop, a drop in core temperature caused by return of cold blood from the extremities to the core circulation. Rewarm trunk first to minimize afterdrop.Severe hypothermia: active external rewarming and active internal rewarming (active core rewarming)
Perform interventions for moderate hypothermia.For hemodynamically stable patients, rewarm with endovascular temperature catheter whenever available.For hemodynamically unstable patients, rewarm with ECMO (preferred approach) or CPB if possible. If ECMO or CPB not available, can perform continuous venovenous rewarming, hemodialysis, continuous arteriovenous rewarming.If other interventions unavailable, may perform peritoneal or pleural irrigation with warmed, isotonic saline (40 to 42°C).Treatment of arrhythmias
Arrhythmias may persist until patient rewarmedIgnore atrial arrhythmias with slow ventricular responseVentricular fibrillation is common rhythm
Electrical defibrillation may be attempted but is rarely successful until core temperature is above 30°C.Initiate CPR in all patients with cardiac arrest; do not perform chest compressions if an organized rhythm is present on the cardiac monitor.*
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