Accidental Hypothermia Thanks to Kyle Mclaughlin for help with his experiences, cases, and knowledge. As opposed to therapeutic hypothermia… Not too uncommon around these parts - In fact, Dr. McLaughlin has a few stories he’ll be able to share with us as we go along.. Weather records in Canada: mount logan -77.5, snag, yukon -63, fort vermillion, ab -61.1, Calgary -45 Accidental Hypothermia

The Basics Clinical Questions Treatment We only have an hour so I’ll keep it brief wherever possible. There will be a handout (made by Kyle) that I will send out. Also, any further questions and I’m happy to provide you with the references. I also have a short video from the USC series for anyone who is interested.

Who gets hypothermia? You’ll find a whole table in Rosen’s about this but just keep in mind the basics: Essentially: Extremes of age, intoxication/behavioural, and co-morbids Old people because: chronic disease (which interfere with heat production and conservation), medications, social isolation, older homes, Young because: larger SA to V ration, relatively smaller subcutaneous tissue layer, inefficient shivering Neonates: no behavioural defense, Etoh/Behavioural: name says it. They lack the behavioural mechanism to leave the cold or bundle up. Decrease heat production Increase heat loss Impaired thermoregulation Other miscellaneous states…

Case: 25 M Ice climber… Temp: 31 degrees Kyle, I’d like you to give the history on this guy right up to the point where EMS get his initial temp….that will lead into the first question about classification and the subsequent questions about differential and expected symptoms at given temps. After that we’ll give more info 25 yo Ice climber at Johnston Canyon- ground level fall and submerged under ice this past Nov. unable to free self from under ice but able to find air pockets and under water caves to breath in. Made decision to leave one-way caves twice back under the ice. Partially submerged for 20-25 minutes. Breaks a small hole in ice and passerby's descend a rope from 5 meters up - patient flops on top of ice. EMS arrive and bystanders have covered patient in jackets. Patient altered and not shivering. EMS strip him down, place in bag and crack neonate warming pads. By the time he arrives in Banff- rectal temp 31, shivering, alert, GCS 15, in rapid A. Fib. Warmed to 37 over 5 hours with bear hugger and warm fluids. Still in A. Fib with rate 150-160 Asymptomatic. Cardioverted to normal sinus. Home after Psych has seen for expected PTSD. Key points: Management at scene- directing EMS to remove cold clothes and actively warm if not shivering. -arrhythmias: most will resolve with warming, expect any type, Osborne J waves are classic.

How would you classify this pt’s hypothermia? 31 degrees C

Mild: Core temp. 32 to 35ºC Moderate: Core temp Mild: Core temp. 32 to 35ºC Moderate: Core temp. 28 to 32ºC Severe: Core temp. below 28ºC This may help in terms of standardizing your lingo but also correlates with their clinical presentation

Mild: 34 - amnesia and dysarthria begin 33 - ataxia and apathy develop Moderate: 32 - stupor 31 - shivering stops 30 - dysrhythmias, CO drops, insulin ineffective Severe: 28 - high risk for VF 27 - lose reflexes and voluntary movement 26 - major A/B disturbance Profound: 19 - flat EEG 18 - asystole Slide of the degrees celcius with corresponding clinical presentation: In more simplified terms: In the mild phase, the body is compensating for the heat loss by producing/conserving more heat In the moderate phase, protective/compensatory measures begin to fail and clinical signs begin to develop In the Severe phase, the patient is grossly unstable In the Profound phase, the patient is dead

Pretend there is no history of exposure…why else could this patient be hypothermic? DIFFERENTIAL DIAGNOSIS — In addition to hypothermia from environmental exposure, many medical conditions can result in hypothermia, including hypothyroidism, adrenal insufficiency, sepsis, neuromuscular disease, malnutrition, thiamine deficiency, and hypoglycemia. Ethanol abuse and carbon monoxide intoxication have been implicated in some cases of hypothermia [13]. Certain medications directly or indirectly cause hypothermia, either by impairing thermoregulatory mechanisms, decreasing awareness of cold, or clouding judgment. The most common medications that impair thermoregulation are anxiolytics, antidepressants, antimanics, antipsychotics, and opioids. Medications that can impair a patient's ability to compensate for a low ambient temperature include oral antihyperglycemics, beta-blockers, alpha-adrenergic agonists (eg, clonidine), and general anesthetic agents [11]. The differential diagnosis of hypothermia is summarized in the table (table 2) [9,14-19]. Risk factors associated with death from accidental hypothermia include ethanol use, homelessness, psychiatric disease, and older age [3,20]. Frostbite and local cold-related injury are discussed in detail elsewhere. (See "Frostbite".)

Differential Diagnosis Increased Heat Loss Impaired Heat Regulation Decreased Heat Production Big Ones: sepsis, trauma, drugs, cns, bgl, hypoT, exposure Increased Loss: Environmental exposure, induced vasodilation (drugs, etoh, toxins), skin (burn, psoriasis), iatrogenic (crrt, bypass, emergent delivery) Decreased Production:Endocrinologic disease (hypopit/adren/thyroid), insufficient fuel (bgl, malnutrition), neuromucular (old, impaired shiver, inactive) Impaired Regulation:Peripheral (spinal cord injury, neuropathy, DM), central (cva, sah, parkinson, hypothalamic, MS, drugs Drugs: Intoxicants, anxiolytics, antidepressants, antimanic agents, antipsychotics, opioids, oral antihyperglycemics, beta blockers Other:Sepsis Pancreatitis Carcinomatosis Uremia Vascular insufficiency Trauma

What mechanisms contribute to heat loss in our patient? 4 mechanisms: evaporation, conduction, convection, radiation

Evaporation, radiation, conduction, convection…. We’re not going to cover these but it’s an important general principle in the treatment of our patient! Body temperature reflects the balance between heat production and heat loss. Heat is generated by cellular metabolism (most prominently in the heart and liver) and lost by the skin and lungs via the following processes [10]: * Evaporation - Vaporization of water through both insensible losses and sweat * Radiation - Emission of infrared electromagnetic energy (COVER the patient) * Conduction - Direct transfer of heat to an adjacent, cooler object (REMOVE wet clothing) * Convection - Direct transfer of heat to convective air currents Most heat loss is through radiation (55-65%) Conduction is minimal but can increase by 5 times if wet clothing…. Convection/conduction are 15% but also keep in mind that wind chill increases convective losses So we’ve discussed classifying cold, mechanisms of heat loss, but how does the cold actually affect the body

How is the cold affecting this patient. At the body level How is the cold affecting this patient? At the body level? At the organ system level?

Increase HR Progressive bradycardia Ventricular Arrhythmias Asystole Pulse is at 50% at 28 degrees Bradycardia is a result of decreased pacemaker activity (and the rest of the conduction system) Virtually any atrial or ventricular dysrhythmia is possible in mod/sever hypothermia pH, electrolyte, oxygen changes also affect conduction

Given the information on the previous slide… Given the information on the previous slide….get everybody to draw their rhythm strip for a pt. at the following temperatures 34: normal intervals, rate increased, ?baseline shiver seen… 32: bradycardia, may start to see osborn waves, possible AF, some widening of intervals 28: severely bradicardic (50%) with prolonged intervals, bigger osborns, possibly VF 18: asystolic Slow, with osborn waves, increase pr, qrs, qt Now get them to draw J wave.

35 degrees: sinus tachycardia

32 degrees: slow, PAC, ?small osborn’s in V4 and V5

26. 5: slow at 50, prominent osborn waves, prolonged QT 26.5: slow at 50, prominent osborn waves, prolonged QT? (supposed to 540), borderline pr

18 degrees: asystole

The J Wave What you need to know: gets larger as the hypothermia gets worse Not pathognomonic….SAH, normal, HyperCa Not prognostic Most prominent in V2-V5

Cold diuresis Reduced renal flow Slide of organ system changes Reduced by 50% at 27 degrees What to keep in mind for the kidney: the patient is likely dry

Progressive depression perfusion maintained until 25 degrees 19 degrees flat EEG

Initial stimulation Progressive decrease CO2 retention and Acidosis Can also get viscous bronchorrhea, decreased ciliary motion, non-cardiogenic pulm. Edema.

Case continued…. Kyle, I’d like you to continue the case and provide information up until he arrives in your department….this will bridge into the discussion of how they’d like to measure the temperature, what labs they’d like and a short slide on abnormal labs then into rewarming 25 yo Ice climber at Johnston Canyon- ground level fall and submerged under ice this past Nov. unable to free self from under ice but able to find air pockets and under water caves to breath in. Made decision to leave one-way caves twice back under the ice. Partially submerged for 20-25 minutes. Breaks a small hole in ice and passerby's descend a rope from 5 meters up - patient flops on top of ice. EMS arrive and bystanders have covered patient in jackets. Patient altered and not shivering. EMS strip him down, place in bag and crack neonate warming pads. By the time he arrives in Banff- rectal temp 31, shivering, alert, GCS 15, in rapid A. Fib. Warmed to 37 over 5 hours with bear hugger and warm fluids. Still in A. Fib with rate 150-160 Asymptomatic. Cardioverted to normal sinus. Home after Psych has seen for expected PTSD. Key points: Management at scene- directing EMS to remove cold clothes and actively warm if not shivering. -arrhythmias: most will resolve with warming, expect any type, Osborne J waves are classic.

What is the most accurate method of measuring his temperature? Classically taught that rectal temperature is the gold standard - what does the evidence say?

Rectal temperature (insert to 15 cm) - Rectal temperature (insert to 15 cm) - ? Accurately reflect brain/heart temperature - Influenced by adjacent frozen stool - lags behind core temperature changes Oral - Often do not measure below 34 degrees C. Tympanic - accurately reflect hypothalamus if true tympanic Axilla - easily affected by external factors Esophogeal (insert to 24 cm) -can be affected by warm airway temperature in tubed patient No studies comparing these modalities in accidental hypothermia. I would say that should use either rectal or esophogeal but have a low threshold to switch if it doesn’t match your clinical picture. Now you’ve confirmed the temperature, what investigations do you want? (you already have the ekg)

Blood Work Chemstrip Electrolytes Creatinine, BUN Hg, WBC, Plt Lactate EKG ABG Other: CK, fibrinogen, INR, cortisol, thyroid Easy to see how hypothermia can affect values on the ABG….do you need to correct for it? Does it even matter? What are your goal parameters? Get group to write out what gas readings they expect of pt at 32 degrees: uncompensated NAG metabolic acidosis Blood gas analyzers warm blood to 37 degrees which increase PP of dissolved gases = higher readings of co2 and 02 and a lower pH Goal is an uncorrected pH at 7.4 and an uncorrected pCO2 at 40

Blood Work Chemstrip: -Insulin ineffective below 30 degrees -persistent elevation despite rewarming signals secondary cause Hct: -Increases 2% for every drop by 1 degree C -Beware of the hypothermic patient with a normal/low hematocrit ABG: -Historically controversial -Use uncorrected values Vipond had a cool case of a Gi Bleed/found down alcoholic who was slowly approaching room temperature- had rectal temp of 28, Low GCS. Tubed, blood given, actively warmed non invasively and did well. Key points: Other medical reasons to be hypothermic Easy to see how hypothermia can affect values on the ABG….do you need to correct for it? Does it even matter? What are your goal parameters? Get group to write out what gas readings they expect of pt at 32 degrees: uncompensated NAG metabolic acidosis Blood gas analyzers warm blood to 37 degrees which increase PP of dissolved gases = higher readings of co2 and 02 and a lower pH Goal is an uncorrected pH at 7.4 and an uncorrected pCO2 at 40

How can you rewarm him?

Passive External Rewarming (PER) Providing blankets Moving to a warm environment Heated IV fluids/oral fluids **pt must be able to produce their own heat ***slow rise in temperature For this method to work, the pt must be able to produce their own heat! If the patient is fully alert, may supplement with oral warmed fluids

Active External Rewarming Applying heat to the skin: Warm blankets Bear Hugger Immersion warming Brokeback Hug? **?body to body contact? Giesbrecht GG, Sessler DI, Mekjavic LB, et al: Treatment of mild immersion hypothermia by direct body-to-body contact. J Appl Physiol 1994; 76:2373. “the rewarming contribution of body-to-body contact appears limited” Downsides to immersion: can’t do cpr, can’t monitor…

Active Internal Rewarming Peritoneal dialysis • Bladder, gastric, or colonic lavage • Heated intravenous fluids • Heated humidified oxygen • Thoracic cavity lavage • Extracorporeal blood rewarming • Hemodialysis

Place 1L NS in 650 W microwave Recipe: Warmed NS Place 1L NS in 650 W microwave Cook on high for 120s, turning and shaking it once at midcycle Agitate before infusion Under ideal circumstances, keep saline in a standard warming device. When large amounts of saline are required for such procedures as peritoneal lavage, warm 1-L saline bags rapidly in a standard microwave oven.[68] Although devices will vary, a 650-W microwave has been demonstrated to warm 1 L of room temperature non–dextrose-containing saline from 21.1?C to 38.3?C (70?F–101?F) in 120 seconds on the high setting. At midcycle (i.e., after 60 sec), interrupt with agitation, and repeat agitation at end-cycle before infusion.

Inhaled warmed O2 Use warmed air at 45 degrees celcius Up to 2 degrees/hr* CAN WE DO THIS IN OUR ER? OR DO WE HAVE TO TALK WITH ICU??? - question for kyle. Using 40 degrees into ET tube. Warmed alveolar blood returns to heart, warming the myocardium Also warms contiguous structures in the mediastinum by conduction Also presents major source of heat loss Advantages: can use it in conjunction with other methods, cheap, non-invasive Disadvantage: not as effective as pl, tl, or bath rewarming Should be used routinely

Peritoneal Lavage Use Arrow peritoneal lavage kit Up to 3 degrees C/hour Place the patient in the supine position with a Foley catheter and nasogastric tube in place. After infiltrating with lidocaine, make an infraumbilical stab incision with a No. 11 blade scalpel, and place an 18-gauge needle into the peritoneal cavity directed toward the pelvis at a 45?. Insert a standard flexible J-wire through the needle, and then remove the needle. Pass the 8-French dialysis catheter over the wire with a twisting motion, and then remove the wire. 4 degrees per hour if combined with warmed nebulized inhaled O2 Advantages: also dialyzes toxin Contraindications: previous abdo surgery, coagulopathy Peritoneal dialysis is appropriate therapy in a severely hypothermic patient. In practice, however, it is often omitted if other measures appear to be successful

GI and bladder rewarming 1.5-2.0 degrees/hour Easy to use, relatively non-invasive BUT, typically need to be tubed and need either an NG or foley Use a large-diameter 32- to 40-French lavage tube with normal saline solution warmed to 40?C to 45?C Gastric: Instill 200- to 300-mL aliquots of fluid into the stomach before removal by gravity drainage. Bladder irrigation: the optimal volume is not known but avoid bladder distention (100- to 200-mL aliquots should be sufficient). The amount of time that the irrigant should be left before removal is not known, but rapid exchanges with a dwell time of 1 to 2 minutes is suggested.

Thoracic Cavity Lavage Typically used in shock patients when no CPB is available Place two large-bore thoracostomy tubes (e.g., 36- to 38-Fr in 70-kg adults) in one hemithorax. Infuse one chest tube with 3-L bags of heated normal saline (40?C–41?C using a high-flow fluid infuser (level 1) Collect the effluent with an autotransfusion thoracostomy drainage set (e.g., Pleur-evac) Or use a y type connector (similar to gastric lavage), and instill 200-300 ml aliquots with a 2 minute dwell time follwed by suction at 20mm Hg Place one tube anterior and high and the other posterior and low Up to 6 or 7 degrees/hour reported

Cardiac Bypass Need to consult CV surgery Up to 2 degrees/5 mins Advantage: rapid rate and optimal circulation/perfusion Disadvantage: delays in getting team/equipment ready, expense, it’s a surgical procedure Indications: Cardiopulmonary bypass is indicated in the following situations: (1) cardiac arrest or hemodynamic instability with a temperature less than 32?C (<89.6?F) (2) no response to less invasive techniques, (3) completely frozen extremities, or (4) rhabdomyolysis with severe hyperkalemia.[2] A 47% long-term survival rate was obtained in a Swiss study of 32 young, otherwise healthy individuals including mountain climbers, hikers, and victims of suicide attempts. Cardiopulmonary bypass is unlikely to confer similar benefit in older, poorly conditioned populations with underlying chronic diseases.[88]

Hemodialysis Up to 4.5 degrees/hour Consider if also has ingested a dialyzable toxin??

Comparison of Rewarming Rates The optimal rewarming rate remains unclear and varies with each case. Standard rewarming rates are a 0.5?C/hr to 2.0?C/hr (0.9?F/hr–3.6?F/hr) rise in temperature in the otherwise stable patient Avoid overtreating and overutilizing invasive techniques in an otherwise stable hypothermic patient. In patients with severe underlying problems such as hypoglycemia, hyperglycemia, sepsis, adrenal crisis, drug overdose, or hypothyroidism, treat these conditions appropriately in addition to treating the hypothermia because long-term outcome may depend more on treatment of the underlying illness than on treating the hypothermia.

Case Continued Kyle, finish off by letting us know how you rewarmed this particular patient. If you can, instead of making it go smoothly, pretend this patient has some afterdrop.

Why has this patient become more hypothermic despite your warming measures? Afterdrop

Approach to rewarming Mild Hypothermia Passive External Rewarming +/- Active External Rewarming In PER - non-invasive. Involves minimizing heat loss while allowing the patient to produce their own heat Cons: pt. must be able to generate heat (glucose, euvolemic, etc) Could also institute active rewarming if: failure to warm, endocrine/trauma/tox/ or other secondary cause of the hypothermia In Shock/arrest: ecmo if able, consider thoracotomy if not able along with everything else Stable:

Approach to rewarming Moderate Hypothermia Active External Rewarming Active Internal Rewarming Still going to do PER but AER is the mainstay of treatment. Will also try more active internal warming (IV NS warmed, humidified ventilation, ?dialysis)

Approach to Rewarming Severe Hypothermia Level 1 callout If Stable, treat as moderate but be prepared for ecmo If Unstable, ACLS and prepare for ecmo

ACLS guidelines? BLS: -prevent heat loss, rewarm -mild AH = passive rewarming -moderate AH = AER -Severe + Stable = AER or AIR -Severe + Unstable = bypass or AIR -Do not withhold ABC’s to rewarm ACLS: -If in VF or pulseless VT, attempt defibrillation -“Might be reasonable to perform further defibs -“Might be reasonalbe to administer vasopressor” New animal studies in the last 10 years have shown improved ROSC with vasopressors but not anti-arrhythmics

Cold and Dead? “Patients with severe accidental hypothermia and cardiac arrest may benefit from resuscitation even in cases of prolonged downtime and prolonged cpr” ACLS guidelines here Specific times to stop: signs of death, evidence about potassium There are countless case reports in the literature about patients with severe, prolonged hypothermia that roll into the ED without any cardiopulmonary activity and survive, often without any morbidity after being re-warmed. This has let to the popular mantra, “they’re not dead until they’re cold and dead”. It’s hard to ignore these miraculous recoveries especially since many accidental hypothermia cases are young, previously healthy individuals. But there are times when it’s quite obvious that our patients are dead and cold rather than cold and dead… Unfortunately, most guidelines are vague when it comes to providing direction in this difficult situation. ACLS says: “Patients with severe accidental hypothermia and cardiac arrest may benefit from resuscitation even in cases of prolonged downtime and prolonged cpr” So, when can we stop resuscitation …when is it futile?

The Obvious: -Decapitation -Non-compressible chest -Ice in mouth and nose -DNR order The Unreliable: -rigor or livor mortis -fixed pupils -tissue deterioration Is anything else prognostic of death?

Rosens: “Significant predictors of outcome” Rosens: “Significant predictors of outcome” asphyxia, prehospital arrest, low or no BP, high BUN, need for intubation in ER Literature: Mt. Hood: only survivors had signs of life on scene, temps were above 20 degrees, K < 7 Mair et al. 1994: K > 10, pH < 6.5, Others: fibrinogen <50mg/dL, ammonia >250mmol/L Mair et al. Prognostic markers in patients with severe accidental hypothermia and cardiocirculatory arrest. Resuscitation; 27:47-54, 1994 Schaller et al. Hyperkalemia: a prognostic factor However, no validated prognostic indicators available….

Next: Frostbite

Frostbite

Case: In minor ER 63 M Pernio/Chilblains: mild cold injury usually after repetitive cold exposure 24 hrs after exposure Face, dorsum of hands and feet, pretibial areas Often young females, raynauds, lupus, apa, Feel burning, itching, erythema, mild edema Plaques, bluish-red nodules, and ulcerations

Pernio Local, inflammatory, bluish-red lesions Caused by prolonged vasoconstriction Gentle drying and massaging. Red/blue/purplish, either single or multiple. Intense burning/itching Vasoconstriction leading to hypoxemia and then vessel wall inflammation Preventative measures are the best treatment Might also try nifedipine which has been shown to decrease pain, recurrence, and length of time for lesions to disappear

Immersion Injury (Trench Foot) -again, prolonged exposure to to wet cold at temperatures above freezing (typically 0 to 15 degrees celcius) -develops slowly over days 3 phases: Pre-hyperemic phase - feet white, not painful, minimal swelling, pulses weak Hyperemic - erythematous, swollen, painful, pulses strong but crt is slow May or may not have Post-hyperemic phase - chronic, cold sensitivity, dull aches/anesthesias, hyperhydrosis Cool, pale feet that are numb/tingle Later feet are cyanotic, cold and edematous After warming, the skin remains erythematous, dry, and painful Bullae, ulceration, and liquefaction/gangrene can develop without treatment Immersion Injury (Trench Foot)

Cold Injury Non-Freezing Pernio Immersion Injury Cold Urticaria Frostnip Frostbite Cold injuries can be divided grossly into freezing and non-freezing injuries, each of which has several distinct entities of its own. How would you tell the difference between frostbite and frostnip?

Frostnip Reversible and superficial No tissue loss Pale and discomfort and tingling Only time will tell the difference between frostnip and frostbite.

Case: 27 F Car broke down on a rural road Case: 27 F Car broke down on a rural road. Decided to walk out While walking through wooded area, she gets lost, at one point ending up knee deep in a stream. She wanders through the forest for 12 hours lost. Eventually she is spotted by a hunter who calls EMS. You get this history on the patch phone and EMS wants to know how they should treat her. Vitals stable. Temp normal - just the extremities you see on the next page: * Get the patient to a warm environment as soon as possible. Whenever possible pad or splint the affected area to minimize injury en route. * Remove wet clothing. * Avoid walking on frostbitten feet; this can increase tissue damage. * Do not rewarm frostbitten tissue if there is a possibility of refreezing before reaching definitive care. This may result in worse tissue damage. * If prehospital warming is attempted, options include placing the affected area in warm (not hot) water or warming it using body heat (eg, placing frostbitten fingers in the axillae). * Do not rub frostbitten areas in an attempt to rewarm them; this can cause further tissue damage. * Avoid the use of stoves or fires to rewarm frostbitten tissue. Such tissue may be insensate and burns can result [7,24,30].

She also forgot to shave her legs that day… How did her legs get this bad - what does the cold do to cause these injuries?

Frostbite Thanks to Mark Bromley for slide As temperature cools, vasoconstriction and endothelial leakage begin to occur When skin temperature hits -4, the skin begins to freeze (extracellularly first). Then either water exits the cell to maintain equilibrium or may even freeze in the cell (if fast cooling) Skin freezing also exerts pressure on surrounding cells (and in combination with vasoconstriciton) blood flow becomes static first at the capillary level. This leads to ischemia and necrosis Underlying response to all these changes include free radical formation, prostaglandin and thromboxame production and generalyzed inflammation

Classification 1st Degree: central area of pallor with surrounding edema 2nd Degree: blisters containing clear or white fluid surrounded by edema (usually within 24 hours) 3rd Degree: hemorrhagic blisters progressing to black eschar over weeks 4th Degree: extends to muscle and bone. Complete tissue necrosis

Treatment Remove wet clothing Rapid rewarming with warm water (40 degrees) Analgesia!! NSAID’s? Td DO NOT: -warm if re-freezing is possible -massage -ambulate on frozen extremities unless no other option -use dry heat Reperfusion is extremely painful - IV meds often required for deep frostbite NSAID’s: physiologic sense. Limited evidence. Not very much downside. Give if no contraindications. Ibuprofen….or could consider ketorolac. Td is reported complication of frostbite (tetanus complicating frostbite, Chan TY) How would you go about thawing the limb?

Treatment Thawing: 40 degrees Until part feels soft, erythema present Usually requires 10-30 minutes Active motion by patient

Treatment Post-thaw: Elevate Sterile, bulky dressing Aloe Vera? Blisters? TPA? Heparin? Abx? Hyperbaric O2?, Pentoxifylline? Dressing: dry after bath before dressing, non-occlusive, aseptic, non-adherent layer first, pledgets between digits, AloeVera: Appears to limit thromboxane and prostaglandins. Limited evidence but benign therapy. Recommended. (Treatment of experimental frostbite with pentoxifylline and aloe vera cream Miller MB study AND Frostbite, methods to minimize tissue loss McCauley RL). Give q6 hours Blisters: controversial: all broken blisters debrided. No good evidence for intact blisters - only expert opinion. Could consider apirating large hemorrhagic bullae (esp. over joints) and leaving smaller whiter ones? TPA: some physiologic sense, since frostbite is associated with stasis/vascular thrombosis. However, evidence is limited to small retrospective studies. Consider if likely life altering, no contraindications, within 24 hours. (An open label study to evaluate the saftey and efficacy of TPA in treatment of sever frostbite AND Reduction of the incidence of amputation and frostbite injury with TPA - both studies showed decrease amputation rates. Second study also showed improved perfusion. However both studies had small numbers - 19 and 34 respectively) Heparin: no evidence that it improves outcomes Abx: controversial. Most would give abx at first sign of infx. Should cover for staph, streptococci, and pseudomonas coverage HBO: case reports have shown improved microcirculation and improved symptoms. Not yet though Pentoxifylline: animal studies promising (increased tissue survival). Need more information. Maybe in severe cases

Treatment Surgery? Admission? Consult surgery and admit for all but minor cases?? Most frostbite injuries will be left to convalesce and declare themselves before operative treatment is considered Many cases of frostbite are either psychiatric or homeless patients who are going to need to be admitted anyway. But for those who have minor injuries with good pain control - could follow-up with the wound care/burn clinic

Summary Spectrum of freezing and non-freezing injuries Treat by rapid rewarming Aloe, ibuprofen, and Td (others are controversial)