European Resuscitation Council Guidelines for Resuscitation ... - CPR

18 de 0ctubre de 2010 www.elsuapdetodos.com1336 C.D. Deakin et al. / Resuscitation 81 (2010) 1305–1352How to cool?. The practical application of therapeutichypothermia is divided into three phases: induction, maintenance,and rewarming. 715 External and/or internal cooling techniques canbe used to initiate cooling. An infusion of 30 ml kg −1 of 4 ◦ C salineor Hartmann’s solution decreases core temperature by approximately1.5 ◦ C 629,633,638,706,707,711,716–727 and this technique can beused initiate cooling prehospital. 511,728–731Other methods of inducing and/or maintaining hypothermiainclude:• Simple ice packs and/or wet towels are inexpensive; however,these methods may be more time consuming for nursing staff,may result in greater temperature fluctuations, and do not enablecontrolled rewarming. 633,638,669,705,709,710,725,726,732–734 Ice coldfluids alone cannot be used to maintain hypothermia, 719 but eventhe addition of simple ice packs may control the temperatureadequately. 725• Cooling blankets or pads. 727,735–740• Transnasal evaporative cooling. 740a• Water or air circulating blankets. 629,630,632,706,707,712,713,727,741–744• Water circulating gel-coated pads. 629,711,720,721,727,738,743,745• Intravascular heat exchanger, placed usually in the femoral orsubclavian veins. 629,630,713,714,718,724,727,732,733,742,746–748• Cardiopulmonary bypass. 749In most cases, it is easy to cool patients initially after ROSCbecause the temperature normally decreases within this firsthour. 498,698 Initial cooling is facilitated by neuromuscular blockadeand sedation, which will prevent shivering. 750 Magnesiumsulphate, a naturally occurring NMDA receptor antagonist, thatreduces the shivering threshold slightly, can also be given to reducethe shivering threshold. 715,751In the maintenance phase, a cooling method with effectivetemperature monitoring that avoids temperature fluctuations ispreferred. This is best achieved with external or internal coolingdevices that include continuous temperature feedback to achievea set target temperature. The temperature is typically monitoredfrom a thermistor placed in the bladder and/or oesophagus. 715 Asyet, there are no data indicating that any specific cooling techniqueincreases survival when compared with any other cooling technique;however, internal devices enable more precise temperaturecontrol compared with external techniques. 727Plasma electrolyte concentrations, effective intravascular volumeand metabolic rate can change rapidly during rewarming, asthey do during cooling. Thus, rewarming must be achieved slowly:the optimal rate is not known, but the consensus is currently about0.25–0.5 ◦ C of warming per hour. 713When to cool?. Animal data indicate that earlier coolingafter ROSC produces better outcomes. 752 Ultimately, startingcooling during cardiac arrest may be most beneficial—animaldata indicate that this may facilitate ROSC. 753,754 Several clinicalstudies have shown that hypothermia can be initiatedprehospital, 510,728,729,731,740,740a but, as yet, there are no humandata proving that time target temperature produces better outcomes.One registry-based case series of 986 comatose post-cardiacarrest patients suggested that time to initiation of cooling was notassociated with improved neurological outcome post-discharge. 665A case series of 49 consecutive comatose post-cardiac arrestpatients intravascularly cooled after out-of-hospital cardiac arrestalso documented that time to target temperature was not an independentpredictor of neurologic outcome. 748Physiological effects and complications of hypothermia. Thewell-recognised physiological effects of hypothermia need to bemanaged carefully 715 :• Shivering will increase metabolic and heat production, thusreducing cooling rates—strategies to reduce shivering are discussedabove.• Mild hypothermia increases systemic vascular resistance, causesarrhythmias (usually bradycardia). 714• It causes a diuresis and electrolyte abnormalities suchas hypophosphatemia, hypokalemia, hypomagesemia andhypocalcemia. 715,755• Hypothermia decreases insulin sensitivity and insulin secretion,hyperglycemia, 669 which will need treatment with insulin (seeglucose control).• Mild hypothermia impairs coagulation and increases bleedingalthough this has not be confirmed in many clinical studies. 629,704In one registry study an increased rate of minor bleeding occurredwith the combination of coronary angiography and therapeutichypothermia, but this combination of interventions was the alsothe best predictor of good outcome. 665• Hypothermia can impair the immune system and increase infectionrates. 715,734,736• The serum amylase concentration is commonly increased duringhypothermia but the significance of this unclear.• The clearance of sedative drugs and neuromuscular blockers isreduced by up to 30% at a core temperature of 34 ◦ C. 756Contraindications to hypothermia. Generally recognised contraindicationsto therapeutic hypothermia, but which are notapplied universally, include: severe systemic infection, establishedmultiple organ failure, and pre-existing medical coagulopathy(fibrinolytic therapy is not a contraindication to therapeutichypothermia).Other therapiesNeuroprotective drugs (coenzyme Q10, 737 thiopental, 757glucocorticoids, 758,759 nimodipine, 760,761 lidoflazine, 762 ordiazepam 452 ) used alone, or as an adjunct to therapeutic hypothermia,have not been demonstrated to increase neurologically intactsurvival when included in the post-arrest treatment of cardiacarrest. There is also insufficient evidence to support the routineuse of high-volume haemofiltration 763 to improve neurologicaloutcome in patients with ROSC after cardiac arrest.PrognosticationTwo thirds of those dying after admission to ICU following outof-hospitalcardiac arrest die from neurological injury; this has beenshown both with 245 and without 640 therapeutic hypothermia. Aquarter of those dying after admission to ICU following in-hospitalcardiac arrest die from neurological injury. A means of predictingneurological outcome that can be applied to individual patientsimmediately after ROSC is required. Many studies have focused onprediction of poor long term outcome (vegetative state or death),based on clinical or test findings that indicate irreversible braininjury, to enable clinicians to limit care or withdraw organ support.The implications of these prognostic tests are such that theyshould have 100% specificity or zero false positive rate (FPR), i.e.,proportion of individuals who eventually have a ‘good’ long-termoutcome despite the prediction of a poor outcome. This topic ofprognostication after cardiac arrest is controversial because: (1)many studies are confounded by self-fulfilling prophecy (treatmentis rarely continued for long enough in sufficient patientsto enable a true estimate of the false positive rate for any givenprognosticator); (2) many studies include so few patients thateven if the FPR is 0%, the upper limit of the 95% confidence intervalmay be high; and (3) most prognostication studies have beenundertaken before implementation of therapeutic hypothermiawww.elsuapdetodos.com