WARM ANAESTHESIA GREETINGS

1. WARM ANAESTHESIA GREETINGS Dr . S.PARTHASARATHY MD., DA., DNB Dip. Diab. DCA, Dip. Software statistics PhD (physio)Mahatma Gandhi medical college and research institute , puducherry – India

2. Why temperature?? • Start with some tempo? • No • Temperature is a vital sign!!

3. History • 1776 – John hunter first measured temperature • 1895 – Harvey cushing measured temperature in anaesthesia

4. Skin and core • Skin temperature – surface of the skin • Core temperature – temperature of blood in Main pulmonary artery. Skin usually less than core

5. Normal 37*C± 0.2 • Core – nasopharygeal, • distal esophagus, • tympanic, • Rectal • bladder , axillay and oral also • All other skin surface – skin temperature

6. Normal regulation • Sensors: Cells through out the body ,abdomen and thoracic tissues, ↓ • Anterior hypothalamus: ↓ • Posterior hypothalamus ↓ Effector organs

7. Cold – A delta fibres • Warm – C fibres Vasoconstriction – AV shunts Nutrition? BP ?

8. Cold warm • Behavioural behavioural • Vasoconstriction vasodilation • Shivering sweating • Nonshivering.Th. anaest. Normal anaest -----------I-----------I-------I------------I-------------- 33 37 39

9. Heat loss • Radiation – infra red • Convection – movement of air • Conduction –contact loss • Evaporation – as water vapour

10. Nonshivering thermogenesis • Non-shivering thermogenesis usually occurs in brown adipose tissue (brown fat) that is present in human infants (between scapulae) • uncouples oxidative phosphorylation, and the energy is dissipated as heat rather than producing ATP from ADP

11. Hypothermia • Anything below 36.7 !! • But -- clinically below 35 • Severe -- when below 32

12. Feel of the cold

13. Hypo – what does it do?? • ↓ liver blood flow • ↓ renal blood flow • ↑ blood viscosity • Shift of ODC • Adrenergic surge • Drug metabolism altered

14. Hypo – what does it do?? • ↓ Cerebral blood flow • ↓ heart rate. • ↑ contractility • ↓ Cardiac output • Defib – ineffective • ↓ ADH – cold diuresis • pH measurement ?? Corrected.

15. Periop Hypo – what does it do?? • Wound infection is more • Bleeding more • Recovery delayed- Anaesth. and Relaxants more action • Mortality and cardiac events more. • Shivering and its problems

16. Some advantages • But it does give better outcomes in neuro protection • Intracranial aneurysm surgery • It is useful in cardiac anaesthesia

17. Operating room – what does it do?? • Cold environment, IV fluids • Laminar flow • Regional anaes. - vasodilation • Body cavities washed with NS. • Anaesthesia widens gap and relaxants inhibit shivering • With the exception of Ketamineall general anaesthetics impair thermoregulation

18. I unit blood or • 1 litre crystalloid administered at room temp. • ↓ core temp by 0.25* C

19. Hypothermia during GA develops with a characteristic pattern • An initial rapid decrease in core temperature core-to-peripheral redistribution of body heat. • Then - slow, linear reduction in core temperature that results simply from heat loss exceeding heat production. • core temperature stabilizes and subsequently remains virtually unchanged. This plateau phase

20. Regional • Prevents vosoconstriction and shiverring • Cold receptors – concentrated in the legs • Hypothermic patient feeling warm sometimes – clinical paradox.

21. Incidence of hypo-- 60% ?? • Prevention Radiant heat lamps. Warm blankets. Warm OR Closed circuit. Warm IV fluids. Forced air circulation –the best

22. Humidifiers • Heat and Moisture Exchangers ( HMEs) • Oesophageal RewarmersThese devices consist of a double lumen esophageal tube through which water is circulated at upto 42°C

23. Blankets- IV warmer- warmed IVF

24. shivering • involuntary contractions of muscles, in response to the chilling effect of low temperatures. • Shivering may also occur at the onset of a fever when the body's heat balance is disturbed.

25. Tonic phase 4-8 cycles/min. • Clonic phase. 5-7 Hz • Clonic phase may resemble fits. • Incidence 40% • Clonic more common after inh. Agents • Nonthermoregulatory tremors in labour.

26. shivering • ↑ IOT • ↑ ICT • ↑ O2 consumption • Hence a big no in IHD patients.

27. Shivering – treatment • Clonidine 75 µg • Pethidine 25 mg • Tramadol 50 mg • Ondansetron 4 mg IV • Others like doxapram, ketanserin,physostigmine,magsulf used. • Hence the mechanism of shivering!!

28. After cold, we move to hot

29. Hyperthermia • Atropine,ether, allergy, mismatched blood • infection, inflammation • Blood in 4th ventricle. Atropine and sweating!! To cool, • Refrigerated IV fluids. • Endovascular cooling with heat exchange catheters

30. Malignant hyperthermia!! • is a rare life-threatening condition • triggered by exposure to IAS • skeletal muscle oxidative metabolism, which overwhelms the body's capacity to supply oxygen, remove carbon dioxide, and regulate body temperature, eventually leading to circulatory collapse and death if not treated quickly.

31. Symptoms • Autosomal dominant • Males more • 1:20,000 • Masseter spasm and ↑ ETCO2 • Tachycardia, tachypnoea, arrythmias, unstable BP, hyperkalemia ,myoglobinuria renal failure • coma

32. C O D S C U P- pneumonic • Circuit • Oxygen • Dantrolene 3 mg/kg , Azumolene is a 30-fold more water-soluble analogue of dantrolene • Supportive measures,Soda bicarb • Cold washes • Urine – mannitol, frusemide. • Potassium disturbance

33. Preop check up • Family history. • ↑ CPK • Positive muscle biopsy • Avoid IAS

34. Probes • Thermistors are made from certain metal oxides whose resistance decreases with increasing temperature. • resistance falls off with increasing temperature

35. Thermocouples are based on the effect that the junction between two different metals produces a voltage which increases with temperature. • clear advantage of a higher upper temperature limit, up to several thousand degrees Celsius.

36. Indications of temp. monitoring • Adults – surgery more than 30 minutes • All children. • Major iv shifts • Nasopharygeal or axillary is ok

37. Carry home message • Temperature is a vital sign. • Hypo and hyperthermia has significant dangerous repercussions in anaesthesia • Are we monitoring? • Are we taking precautions? • Are we noting morbidity??

38. Thank you