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temperature regulation under anesthesia.ppt
- 2. Temperature regulation &its anesthetic implications Dr Tanveer Alam Khan Department of Anesthesiology Shaukat Khanum Memorial Cancer Hospital & Research Centre 29th September 2017
- 3. Learning Objectives • Introduction •Techniques of measuring temperature • What happens in anesthesia ? • Maintaining normothermia • Hypothermia and its complications • Malignant hyperthermia • Take home message Objectives introduction Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 4. Introduction: Thermoregulation: is the abilityof an organism to keep its body temperature within certain boundaries’ Body temperature is usually maintained near a constant level of 36.5–37.5 °C (97.7– 99.5 °F) through thermoregulation Hypothermia it is defined as a body core temperature below 36.0 °C (95.0 °F) Hyperthermia 37.5 or 38.3 °C (99.5 or 100.9 °F Hyperpyrexia >40.0 or 41.0 °C (104.0 or 105.8 °F) . Objectives introduction Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 5. Temperature monitoring • CoreSites – Pulmonary artery – Distal esophagus – Nasopharynx – Tympanic membrane thermocouple • Other generally-reliable sites – Mouth – Axilla – Bladder • Sub-optimal – Forehead skin – Infrared “tympanic” – Infrared “temporal artery” – Rectal Objectives introduction Anesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 7. Thermoregulation Processing of thermoregulatoryinformation: • Afferent input cold signal-Aδ fiber warm signal-C fiber • Central control Hypothalmus • The inter-threshold range (core temperatures that do not trigger autonomic thermoregulatory responses) is only 0.2℃ • Efferent responses Major autonomic defenses against heat: sweating cutaneous vasodilation Major autonomic defenses against cold: cutaneous vasoconstriction , nonshivering thermogenesis , shivering Objectives introduction Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 8. Anesthesia and thermoregulation •General anesthesia removes a pt’s ability to regulate body temperature through behavior, so that autonomic defenses alone are available to respond to changes in temperature • Inter-threshold range is increased from 0.2 to 4℃ (20 times), so anesthetized pts are poikilothermic - with body temperatures determined by the environment Objectives introduction Anesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 9. Anesthesia and thermoregulation Phase1 redistribution in 1 hour Phase 2 gradual decline 2 to 4 hours Phaase 3 steady state Thermal plateau> 4 hours Objectives introduction Anesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 10. Anesthesia and thermoregulation Objectivesintroduction Anesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message PHASE 1 Heat redistribution decreases 0.5-1.5℃ during 1st hr Heat redistribution decreases core temperature, but mean body temperature and body heat content remain unchanged
- 11. Anesthesia and thermoregulation Phase2 Slow linear reduction decreases in a slow linear fashion for 2-3hrs Simply because heat loss >metabolic heat production 90% heat loss through skin surface by radiation and convection Objectives introduction Anesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 12. Anesthesia and thermoregulation Phase3 : thermal plateau • After 3-5 hrs, core temperature stops decreasing • It may simply reflect a steady state of heat loss=heat production • If a pt is sufficiently hypothermic, plateau phase means activation of vasoconstriction to reestablish the normal core-to-peripheral temperature gradient • Separation of core and peripheral compartments Objectives introduction Anesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 13. Anesthesia and thermoregulation Objectivesintroduction Anesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message 35 36 37 38 Threshold (°C) Control Spinal Sweating Vasoconstriction Shivering 35 36 37 38 Threshold (°C) Control Spinal Sweating Vasoconstriction Shivering Regional anesthesia impairs both central and peripheral thermoregulation Central regulatory inhibition Increased inter-threshold range Peripheral sympathetic and motor block Incorrect perceiving of skin temperature Behavioral inhibition Hypothermia fails to trigger cold sensation Hypothermia Comparable to general anesthesia but Worst when general and regional combined
- 14. Hypothermia Complications • Wound infection •Decrease Coagulopathy • Drug metabolism • Increases morbid myocardial outcomes • Promotes bleeding and increases transfusion requirement • Thermal discomfort • Postop recovery time Potential benefits • Neuroprotective by dec CMRO2 (7% 1C) & dec in ICP • Decrease free radical formation Objectives introduction Anesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 15. Hypothermia management • Prewarming • Operative room condition • Airway heating and humidification • Fluid warming • Cutaneous warming / forced air warming • More layers don't really help much ! • Fluid warming +Forced air warming are enough to maintain core body temperature intraoperatively Objectives introduction Anesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 16. Malignant Hyperthermia “It isa biochemical chain reaction response triggered by commonly used general anesthetics and the paralyzing agent succinylcholine, within the skeletal muscles of susceptible individuals” –MHAUS.org Has autosomal dominant inheritance Incidence of 1-5 : 100,000, < 5% mortality rate Objectives introduction Anesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 17. Pathopysiology Alteration in theCa induced ca release via the ryanodine receptor channel (RYR1) or! impairment in the ability of the sarcoplasmic reticulum to sequester calcium via the ca transporter After trigger agent is administered, there is a sudden and prolonged release of ca which causes - Massive muscle contraction - Lactic acid production - Increased body temperature Objectives introduction Anesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 18. Malignant Hyperthermia Objectives introductionAnesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 19. Malignant Hyperthermia Trigggering agents Volatilegaseous inhalation: Isoflurane Sevoflurane Desoflurane Haloflurane Enflurane Methoxyflurane Succinylcholine: Suxamethonium decamethonium Non triggering agents Propofol Ketamine Nitrous oxide All local anesthetics All narcotics Non depolarizing muscle relaxants: •Vecuronium •Rocuronium •pancuronium Objectives introduction Anesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 20. Malignant Hyperthermia • Callfor help (let surgeon know) • Turn off potential triggering agents • Administer dantrolene 2.5 mg/kg every five minutes • Cool patient to 38C • Monitor and correct blood gases, electrolytes and glucose • Dantrolene stops the calcium released by binding to the ryanodine receptor and blocking the opening of the channel therefore stopping the release of calcium. It has little effect on heart and smooth muscles as the ryanodine receptors differ in these tissues (RYR2). •Objectives introduction Anesthesia and Thermoregulation Hypothermia/ Hyperthermia Malignant hyperthermia Take home message
- 21. Take home message •Body maintains normothermia by thermoregulation • Anesthesia cause hypothermia in three different phases rapid > slow >plateau • Hypothermia can leads to serious complication like increase bleeding ,increase transfusion requirement , decrease metabolism ,increase risk for infection ,increase hospital admission duration • Hypothermia can be neuroprotective • Hypothermia can be controlled efficiently. • Malignant hyperthermia is an anesthetic emergency ,can be predict during preoperative history, always call for senior help, manageable inside OR with help of dentroline and needs post op ICU/HDU postoperatively after discharge Introduction Obesity Bariatric surgery Peri-operative management Take home message
- 22. References • Brown, DJ;Brugger, H; Boyd, J; Paal, P (Nov 15, 2012). "Accidental hypothermia.". The New England Journal of Medicine. Laupland KB (July 2009). "Fever in the critically ill medical patient". Crit. Care Med. Brown, DJ; Brugger, H; Boyd, J; Paal, P (Nov 15, 2012). "Accidental hypothermia.". The New England Journal of Medicine • Thermoregulation: Physiological and Clinical Considerations during Sedation and General Anesthesia • Marcos D´ıaz, DDS* and Daniel E. Becker, DDS ` *Private Practice, Advanced Aesthetic Center for Oral and Maxillofacial Surgery, Weston, Florida, Professor of Life and Health Sciences, Sinclair Community College, and `Associate Director of Education, General Dental Practice Residency, Miami Valley Hospital, Dayton, Ohio Introduction Obesity Bariatric surgery Peri-operative management Take home message
- 23. Few BCQs ,shallwe? Introduction Obesity Bariatric surgery Peri-operative management Take home message
- 24. Q:1 • The followingare physical processes by which heat is lost from the body.Which sequence reflects the order of these processes from greatest to least percentage of total heat loss? • A. Convection and conduction, evaporation, radiation • B. Convection an d conduction, radiation, evaporation • C. Evaporation, radiation, conduction and convection • D. Radiation, conduction an d convection, evaporation • E. Radiation, evaporation, conduction and convection Introduction Obesity Bariatric surgery Peri-operative management Take home message
- 25. Q:2 Following in ductionof general anesthesia, a decline in body temperature occurs in 3 phases. Which of the following statements accurately describe these phases? A. During phase1, core temperature declines as heat is redistributed from core tissues to peripheral tissues. B. During phase 2, core temperature declines as heat is lost from the body. C. During phase 3, core temperature declines rapidly as mechanisms for thermoregulation commence to fail. D. A and B are correct. E. A, B, and C are correct Introduction Obesity Bariatric surgery Peri-operative management Take home message
- 26. Q:3 Introduction Obesity Bariatricsurgery Peri-operative management Take home message
- 27.