In-flight cooling after out-of-hospital cardiac arrest

Abstract

Guidelines recommend cooling to 32–34 °C for 12–24 h in comatose survivors of out-of-hospital cardiac arrest (OHCA).1Nolan J.P. Morley P.T. Hoek T.L. Hickey R.W. Therapeutic hypothermia after cardiac arrest. An advisory statement by the advancement life support task force of the International Liaison committee on resuscitation.Resuscitation. 2003; 57: 231-235Abstract Full Text Full Text PDF PubMed Scopus (441) Google Scholar Whilst the best time to start hypothermia is unknown, achieving target temperature within 4 h of successful resuscitation is thought to be desirable.2Nolan J.P. Hazinski M.F. Steen P.A. Becker L.B. Controversial topics from the 2005 International Consensus Conference on cardiopulmonary resuscitation and emergency cardiovascular care science with treatment recommendations.Resuscitation. 2005; 67: 175-179Abstract Full Text Full Text PDF PubMed Scopus (38) Google Scholar, 3Wolff B. Machill K. Schumacher D. Schulzki I. Werner D. Early achievement of mild therapeutic hypothermia and the neurologic outcome after cardiac arrest.Int J Cardiol. 2009; 133: 223-228Abstract Full Text Full Text PDF PubMed Scopus (169) Google Scholar Aeromedical retrieval of OHCA survivors from remote locations can cause delays if hypothermia is not started during transport. Cooling equipment that is light, compact and easily stowed needs to be transported on an aircraft to enable patient cooling during transfer.4Kamarainen A. Virkkunen I. Tenhunen J. Yli-Hankala A. Silfvast T. Prehospital therapeutic hypothermia for comatose survivors of cardiac arrest: a randomized controlled trial.Acta Anaesthesiol Scand. 2009; 53: 900-907Crossref PubMed Scopus (111) Google Scholar We have developed an in-flight cooling protocol using intravenous (IV) cold Hartmann's solution and chemical cooling packs. We describe the initial experience of cooling patients during retrieval by the Emergency Medical Retrieval Service (EMRS) in the west of Scotland, a rural area with over 100 islands. Healthcare is provided in remote health centres by general practitioners who do not routinely anaesthetise patients or start cooling. Over 20 months (1st June 2008–31st January 2010) 380 patients were transported by the EMRS. Seventeen patients were referred following non-traumatic OHCA. Thirteen of these remained comatose after successful resuscitation. One comatose patient died on arrival of the EMRS. Cooling was initiated at the discretion of the EMRS senior doctor in five patients during retrieval (Table 1). A delay in the availability of oesophageal temperature monitoring probes led to several patients not being cooled.Table 1Out-of-hospital cardiac arrest survivors cooled during retrieval by the Emergency Medical Retrieval Service (EMRS).CaseCooled during retrievalAgeSexInitial rhythmTime from collapse to ROSC (min)Toes − arrival EMRS (°C)Toes − arrival ICU (°C)Toes change (°C)Time from ROSC to start of cooling (h:min)Total time from ROSC to ICU (h:min)Outcome1Y67FVF1534.132.8−1.302:0004:30Survived D/C2Y64MVF536.934.5−2.502:1503:30Survived D/C3Y70FVF1036.534.9−1.602:3005:00Died ICU4Y78MVF1034.932.3−2.604:4007:00Died ICU5Y50FVF1536.035.9−0.102:2504:45Survived D/C6N62FVF6U36.0U05:3004:35Survived D/C7N62MASY30UUU05:4505:15Died in ICU8N54MVF5U37.9U03:3003:30Survived D/C9N65MVF43636.4+0.404:0003:30Survived D/C10N64FVF536.837.6+0.806:1506:00Survived D/C11N63MUU35.037.2+2.211:3011:00Survived D/C12N52MPEAU32.733.0+0.306:1506:00Died ICUROSC = return of spontaneous circulation; VF = ventricular fibrillation; ASY = asystole; PEA = pulseless electrical activity; Toes = oesophageal temperature; ICU = Intensive Care Unit; D/C = discharge; U = unknown. Open table in a new tab ROSC = return of spontaneous circulation; VF = ventricular fibrillation; ASY = asystole; PEA = pulseless electrical activity; Toes = oesophageal temperature; ICU = Intensive Care Unit; D/C = discharge; U = unknown. Fluids cooled in a fridge (4 °C) were transported in an insulated cool box with activated chemical ice pack. Fluids remained cold (<6 °C) for up to 3 h during transport. On arrival of the EMRS, the patient was sedated, paralysed and intubated, and controlled ventilation started. The patient was then cooled by IV infusion of 30 ml/kg of cold Hartmann's. Ice packs were activated and placed in the axillae and groin. The time interval between successful resuscitation and the patient being retrieved and flown to an Intensive Care Unit (ICU) was at least 3.5 h. Cooled patients had a mean decrease in body temperature during retrieval compared to patients not cooled (−1.6 °C vs. +0.9 °C, p = 0.005) and a lower body temperature on ICU arrival (34.1 °C vs. 36.4 °C, p = 0.05). Two of the 5 cooled patients achieved target temperature (<34 °C) before ICU arrival. No complications of in-flight cooling were reported. We have shown that a simple, cheap, effective means of initiating mild therapeutic hypothermia in OHCA survivors during retrieval from remote and rural locations is feasible and reduces delays in initiating therapeutic hypothermia. Greater awareness amongst retrieval teams and use of cooling during retrieval of comatose OHCA survivors could be beneficial.5Suffoletto B.P. Salcido D.D. Menegazzi J.J. Use of prehospital-induced hypothermia after out-of-hospital cardiac arrest: a survey of the National Association of Emergency Medical Services Physicians.Prehosp Emerg Care. 2008; 12: 52-56Crossref PubMed Scopus (36) Google Scholar Further research is warranted to determine whether cooling post-OHCA patients during retrieval from remote locations would confer additional benefit to survival and neurological outcome. The authors declare that there are no conflict of interest.