AccidentalHypothermia[意外低温](PPT-79).ppt

Accidental Hypothermia Franois Dufresne McGill Emergency Medicine May 2nd 2001 The Case of Tommy 23h10 Call from MD working in James Bay Male, 27 y.o. Unresponsive. Found in snow, cross-country skiing Normal Airway. Breathing. O2 sat. Femoral pulse + (35) BP. GCS=3 TR = 28C. IV. Monitor. Mask with 100% O2 The Case of Tommy Friend told MD: PMH. Rx. drugs. EtOH Major foot deformity Looks like fell in ski and could not return home by himself MD has some questions for you The Case of Tommy Should he intubate? Are there risks to precipitate dysrythmias? Cold myocardium prone to arythmias? How should he rewarm the patient? Danger of afterdrop? He wants an ABG but should he ask for the blood to be warmed to normal T for analysisor it doesnt matter? Answer: Youll call him back The Case of Tommy MD calls you back 30 minutes later Pt in cardiac arrest : V.fib. Now 27C 3 shocks Epinephrine + re-shock Having Amiodarone prepared How long should he do CPR and rescussitation? Anything wrong ?Answer ? Introduction Maritime / War litterature Hannibal experience in 218 B.C Hannibal against Rome Introduction EtOH Mental illness Homelessness Province of Quebec Cold Plan Definitions Physiology Pathophysiology Labs findings : ABG, ECG Rewarming methods Afterdrop ACLS 2000 guidelines Definitions Primary VS Secondary Primary Normal thermoregulation Overwhelming cold exposure Secondary Abnormal thermogenesis Multiple causes Definitions Hypothermia : 32C) Increase metabolic rate Maximum shivering thermogenesis Amnesia / dysarthria / ataxia Loss of coordination Tachycardic, tachypneic Normal BP Moderate (28 32C) Stupor No shivering Bradycardic / A.fib BP RR Pupils dilated ( 90% CO2 production can by 65% Possible anaerobic metabolism Rewarming rate : 0.5C - 2.0C /h Method of choice for mild hypothermia Adjunt for moderate hypothermia Rewarming methods : Active external rewarming Heat to body surfaces Heating blankets (fluid filled) Air blankets Radiant warmers Immersion in hot bath Water bottles / Heating pads Less effective than internal rewarming if vasoconstricted + Active external rewarming Concern about afterdrop. Rewarming rates : 1C 2.5C / h Circulatory problem may be by applying devices to trunk only. Very few prospective controlled study comparing methods. Forced Air Blankets ED patients Moderate to severe hypothermia ( electrical heating Rates 1.5C/h with electical heating No afterdrop both groups Greif R and al, Resistive heating is more effective than metallic-foil insulation in an experimental model of accidental hypothermia: a randomized controlled trial. Ann Emerg Med. April 2000; 35: 337-345. Rewarming methods : Active internal (core) rewarming Warm iv fluids Warm, humid oxygen Peritoneal lavage Gastric / Esophageal lavage Bladder / Rectal lavage Pleural / Mediastinal lavage Microwaves (Diathermy) Extracorporeal circulatory rewarming Warm iv fluids Up to 45C shown to be safe 65C fluid studied in dogs Journal of Trauma 1993 (8 dogs) American Journal of Surgery 1996 (10 dogs) Through IVC Safe. No Complications 2.9C/h compared to 1.25C/h (J Trauma) 3.7C/h compared to 1.75C/h (Am J Surg) Warm iv fluids SalineNot RL Long tubulure = lost of heat Can use microwave for saline (No D5W) Annals of EM, 1984 and 1985 1L of NS to 39C : 2 minutes at high power. No microwave rewarming for PRBC Hemolysis Hemoglobinuria Transfusion reaction Warm, humidified O2 42C-46C Prevent heat loss Negligible heat gain Very important in management of hypothermic patient: Up to 30% of heat production lost through airway. Gastric/Oesophageal/ Bladder/Rectal lavage Not shown to be better than external rewarming. Limited surface area Limited heat exchange Limited utility (!) Recommend as last resort when other modalities not available. Peritoneal lavage Fluid at 40-45C Up to 12 L/h KCl free Hepatic rewarming Renal support when dialysate is used 2C-4C / h C.I. Abdominal trauma Acute abdomen Free intra-abdominal air Peritoneal lavage Almost all studies before 1980 Almost all animal studies Critical Care Medicine 1988 11 dogs Comparing peritoneal/pleural lavage and heated aerosol inhalation Peritoneal and pleural lavage equivalent 6C/h/m2 Heated inhalation alone : little heat gain Pleural lavage Closed-thoracic lavage Continuous thoracic cavity lavage Two large (38F) ipsilateral chest tubes 1: 2nd or 3rd anterior intercostal space, midclavicular. 2: 5th or 6th intercostal space, posterior axillary line. NS or tap water 42C Rewarms heart + greater vessels Hall KN and al. Closed thoracic cavity lavage in the treatment of severe hypothermia in human beings. Ann Emerg Med, Feb 1990;19:204-206. Mediastinal lavage Requires certain expertise Limited clinical experience Case reports Internal cardiac massage 8C / h Douglas D. Brunette, Hypothermic cardiac arrest: An 11 year review of ED management and outcome. Am J Emerg Med 2000; 18:418-422. Extracorporeal blood rewarming techniques Hemodialysis Arteriovenous rewarming Venovenous rewarming Cardiopulmonary bypass Extracorporeal blood rewarming - Hemodialysis : renal dysfunction - AV depends on the pts BP - CPB is the Gold Standard . - CPB improves long term survival and neurologic outcome. - 15 of 32 long term survivors and none had neurologic deficits (7 years later). B.H. Walpoth and al. Outcome of survivors of accidental deep hypothermia and circulatory arrest treated with extracorporeal blood warming, N Engl J Med, 1997;337:1500-5 Diathermy Ultrasonic waves Microwaves Short waves Few studies Radio wave regional hyperthermia: Experience with Tx of tumors. Not widespread because of dosages in human poorly defined. Diathermy Prospective Radio Wave vs. Peritoneal lavage 6 dogs Rate of rewarming 3x for Radio wave. J.D. White and al. Controlled comparison of Radio Wave regional hyperthermia and peritoneal lavage rewarming after immersion hypthermia, J Trauma, 1985; (25)10: 989-993. The Afterdrop Phenomenon Continued fall in deep core T during the initial period of rewarming. First described by James Currie in 1798 Theory of Burton and Edholm (1955): Attributed to peripheral vasodilatation Return of cold blood to central circulation Cooling of myocardium Accepted theory until mid 80s Burton, A.C., and O.G. Edholm. Man in Cold Environment. London: Arnold, 1955, p.216. Paul Webb, An alternative explanation. J. Appl. Physiol. 1986 Fall of T during active rewarming: Up to 2C 10 30 min Used calorimeter, rectal, esophageal and tympanic probes. Heat loss calculation Webb, Paul. Afterdrop of body temperature during rewarming: an alternative explanation. J.Appl.Physiol. 60(2): 385-390, 1986. 2 mecanisms for afterdrop Convection mecanism Return of cold blood from periphery Minimal is any contribution Conduction mecanism Thermal gradient principal Heat flow principal Webb, Paul. Afterdrop of body temperature during rewarming: an alternative explanation. J.Appl.Physiol. 60(2): 385-390, 1986. Skin/Tissues Blood vessel Environement Heat transfer Conduction Mecanism Heat transfer Afterdrop: an alternative explanation Active external rewarming increase threat of further cooling of the heartas much as thought before. Correlated by many other papers Savard, G.K., K.E. Cooper, W.L. Veale, and T.J. Malkinson. Peripheral blood flow during rewarming from mild hypothermia in humans. J. Appl. Physiol. 58(1): 4-13, 1985. Romet, Tiit T. Mechanism of afterdrop after cold water immersion. J.Appl.Physiol. 65(4): 1535-1538, 1988. The Alcatraz/San Francisco Swim Study San Francisco Baycontest Swims from Alcatraz Island to shore No wetsuits or protective clothing Water T = 12C (53F) Outside : T = 10C 3 Km 11 subjects for study 23 y.o to 70 y.o (!) Measured T after contest. Thomas J. Nuckton and al. Hypothermia and afterdrop following open water swimming: The Alcatrax/San Francisco Swim Study. Am J Emerg Med 2000; 18:703-707. Afterdrop conclusion Rectal T lags behing esophageal T and is often than esophageal and pulmonary T. Think about it but you can probably not prevent it. Issue with active external rewarming Other concerns about external rewarming: Acidosis Hypotension Management: ED issues Intubation General be