Ver el código de «Therapeutic hypothermia»

==Background==
*Determination of Neurologic Prognosis is unreliable before at least 72 hours after ROSC
**Do not neuroprognosticate until 72 hours post rewarming.
*Greatest benefit in out-of-hospital V-fib, though may help in other dysrhythmias<ref>Nolan, et al. Therapeutic [[Hypothermia]]After Cardiac Arrest. Circulation. 2003; 108: 118-121.</ref>
*Two most likely mechanisms of action:
**Reduces cerebral metabolism by 6-8% per degree C
**Reduces oxygen free radical production and lipid peroxidation
*Cooling to 32-34ºC in initial studies, current studies suggest 36ºC equally beneficial<ref>Nielsen N, et al. Targeted Temperature Management at 33°C versus 36°C after Cardiac Arrest. N Engl J Med. 2013; 369:2197-2206. DOI: 10.1056/NEJMoa1310519</ref>
*Treatment should be initiated immediately after ROSC
**Patient may be cooled concurrently with cardiac catheterization
*Cooling should occur prior to CT scan if there is need for intracranial pathology workup 
*AHA recommends 12-24 hrs of cooling
*NNT of ~6
*Pediatrics<ref>Moler FW et al. Therapeutic Hypothermia after In-Hospital Cardiac Arrest in Children. N Engl J Med 2017; 376:318-329January 26, 2017.</ref><ref>Moler FW et al. Therapeutic Hypothermia after Out-of-Hospital Cardiac Arrest in Children. N Engl J Med 2015; 372:1898-1908May 14, 2015.</ref>
**Two large RTCs for TH, one in out-of-hospital and another in in-hospital arrests
**Therapeutic hypothermia does not appear to provide a survival or improved neurological benefit<ref>Mosler FW, et al. Therapeutic hypothermia after out-of-hospital cardiac arrest in children. N Eng J Med. 2015; 372:1898-1908.</ref>
***In both studies, '''no difference''' in survival, function at 12 months post-arrest, blood product use, infection rates

==Indications==
*[[Vfib]] arrest
*Other pulseless [[dysrhythmias]] (relative)

==Contraindications/Exclusions==
*>12hrs since ROSC
*Glasgow Motor score  >5
*Minimal pre-morbid cognitive status
*Unable to maintain [[shock|SBP > 90 mmHg]], with or without pressors, after CPR
*Other reason for coma
**Intracranial pathology (i.e. [[intracranial hemorrhage]], ischemic [[stroke]])
**[[Subarachnoid hemorrhage]]
**[[Sedation]]
**[[Drug overdose]]
**[[Status epilepticus]]
*[[Sepsis]] as etiology for arrest
*DNR/DNI status, terminal illness
*Uncontrollable bleeding or known [[coagulopathy|bleeding diathesis]] with active bleeding
*Significant [[trauma]] (especially intra-abdominal)
*[[Pregnancy]]
*Therapeutic hypothermia may be safe for postpartum cardiac arrest<ref>Song et al. Safely completed therapeutic hypothermia in postpartum cardiac arrest survivors. Am Jour Emer Med. June 2015. Volume 33, Issue 6, Pages 861.e5–861.e6.</ref>

==Cooling==
*Cool to 32-34ºC as soon as possible (within 4 hours)
**Strict maintenance of temperature at 36ºC may have similar benefits
*Initiate rewarming 24 hrs after target temperature was reached
*Cooling methods
**Maintain at 32-34ºC with 2 cooling blankets to sandwich the pt, with sheets covering the blankets to protect skin
**Alternatively, use heat exchange device (Icy Cath) or 4°C IVF at 30 cc/kg over 30 min
**Cooling pads on the thighs and abdomen (Arctic Sun)
**Supplement with ice packs to groin, chest, axillae, neck until 34ºC reached
*Prevention of shivering and paralysis
**Use [[benzodiazepines]]
**Paralytics only if needed, and ensure patient fully sedated

==Maintenance==
===[[Sedation]]===
*[[Fentanyl]] bolus 50 mcg IV every hour as needed for pain
*Fentanyl IV infusion NSS
*[[Propofol]] IV infusion 
*[[Lorazepam]] IV infusion
*Lorazepam bolus 1mg IV every 2 hours as needed for agitation
===Shivering===
*Prevention of shivering is important to avoid warming and needless oxygen consumption
*May require train of four monitor with goal of 1-2/4 twitches with neuromuscular blockade
*Lower doses of NMB work against shivering
*Higher doses of NMB used to paralyze the diaphragm in these scenarios:
**Need to decrease O2 consumption
**Decrease plateau pressures
**Hypoxemia is present
*Consider [[meperidine]] q2hrs<ref>Choi HA, Ko SB, Presciutti M, et al. Prevention of Shivering During Therapeutic Temperature Modulation: The Columbia Anti-Shivering Protocol. Neurocrit Care. 2011; 14(3):389-394.</ref><ref>Fox Chase Cancer Center. Therapeutic [[Hypothermia]]Protocol. University of Pennsylvania. https://www.med.upenn.edu/resuscitation/docs/protocols/FoxChaseCancerCenterTherapeuticHypothermiaOrderSetafterCardiacArrest-latestrevision8-4-11.doc</ref>:
**50mg for normal renal function
**25mg if CrCl < 30ml/min
*[[Pancuronium]] IV infusion 
**Initiate before initiating cooling. Dosing recommendations: 0.1mg/kg loading dose followed by a continuous infusion of 0.33-2 mcg/kg/minute
**Do not use in patients with renal and/or hepatic insufficiency
*Cisatracurium for renal/hepatic impairment
**0.2mg/kg IV bolus
**Followed by infusion at 1 mcg/kg/min, max of 3 mcg/kg/min
*Columbia University anti-shivering protocol
[[File:columbia shivering protocol.PNG|thumbnail]]

==Rewarming==
*If severe dysrhythmia/BP instability/bleeding develops, rewarm
*Discontinue K infusions (extracellular K increases)
*Keep paralytic and sedative until rewarmed
*Slow rewarm at 0.5°C to target of 36°C

==General Management==
===Other Concerns===
*Head of bed at 30 degrees
*Goal MAP 80 - 100 mmhg
**Titrate with [[norepinephrine]] (start 2-4 mcg/min) if EF > 50%
**Titrate with [[dobutamine]] (start 2.5-20 mcg/kg/min) if EF < 50%
**IV [[nitroglycerin]] starting at 10 mcg/min if hypertensive
*Check skin q2-6 hrs for cold injury
*Maintain normoglycemia
**Do not treat [[hyperglycemia]] aggressively, as enzymatic functions are decreased at low temperatures, and rebound hypoglycaemia possible with rewarming
*Replete K, Mg, Phos, Ca (hypothermia induced diuresis is expected)
*Common unconcerning ECG findings during cooling - Osborne wave, HR < 40 bpm
*Consider continuous EEG within 6 hrs, no later than 12 hrs after onset of cooling
*Stress dose [[steroids]] for adrenal insufficiency
*?[[Seizure]] prophylaxis

===Labs===
*ABG q6 hrs for duration of hypothermia
*CBC, Coags, BMP, Mg, Phos q6 hrs for duration of hypothermia
**Expect decreased K, Ca, Mg, Phos during, and rebound at rewarming
**Hyperglycemia as metabolism slows at low temperature and body develops insulin resistance
*[[Troponin]]s, CK-MB q6 hrs x2 days
*Lipase, LFTs (if abnormal, no need to intervene unless persistent after rewarming)
*Other - Cortisol, UA, Pan-cultures, tox screen

===[[ABG]] Interpretation===
*Rewarm ABG to 37C for analysis (controversial)
*A warmed ABG from a hypothermic patient will show a  higher PaO2, higher PaCO2, and a lower pH than that actually present in the patient’s blood ''in vivo''
**PaO2 is decreased by 5 mmHg for each degree below 37C
**PaCO2 is decreased by 2 mmHg for each degree below 37C
**Change in pH = 0.015 pH units per degree C change in temperature
***If measured pH is 7.360 at 37C, then the pH at 34C is calculated as follows: 
****pH = [7.360 + (37-34)(0.015)] = 7.405

===Monitoring===
*[[ECG]] q8 rule out ACS
*Arterial line
*Foley with temperature probe
*CVP, ScvO2

===Imaging===
*Consider head CT
*Consider CTPE study

===Other Considerations===
*GI prophylaxis
*Modify prophylactic [[heparin]] or [[LMWH]] dosing as there is hypothermic coagulopathy<ref>Wahby KA et al. Heparin dosing in critically ill patients undergoing therapeutic hypothermia following cardiac arrest. Resuscitation. 2014 Apr;85(4):533-7.</ref>
**No clear best way for monitoring of anticoagulation until further studies
**Consider modified dosing:
***Heparin 40 units IV bolus
***Followed by 7 u/kg/hr during TH with scheduled repeated coags, plus or minus heparin levels

==Disposition==
*ICU admission

==External Links==
*[http://www.acep.org/Clinical---Practice-Management/Focus-On--Therapeutic-Hypothermia/ Focus On: Therapeutic Hypothermia]
*[http://www.emrap.org/episode/august2013/therapeutic EMRAP:Therapeutic [[Hypothermia]]with Amal Mattu, MD FAAEM]

==See Also==
{{Hypothermia Cardiac Arrest Links}}

==References==
<references/>

[[Category:Critical Care]][[Category:Cardiology]]