Hypothermic Anesthesia

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Hypothermic Anesthesia

  1. 2. HYPOTHERMIA <ul><li>HYPOTHERMIA </li></ul><ul><li>Fall in temperature </li></ul><ul><li>Decrease in body metabolism </li></ul><ul><li>Decreased oxygen requirement of body tissues & organs </li></ul>
  2. 3. <ul><li>E.g. </li></ul><ul><li>In dog O2 requirement decreased to 50% at 30◦c & 65% at 25◦c. </li></ul><ul><li>Metabolic rate of isolated slices of heart was reduced by 90% at 10◦c. </li></ul><ul><li>Potassium arrested heart at 37◦c utilizes </li></ul><ul><li>4 times glycogen and produces 3 times lactic acid as by heart at 17◦c. </li></ul>
  3. 4. <ul><li>However O2 consumption varies for different organs at a particular temperature. </li></ul><ul><li>Conclusion ;- vital organs (liver, brain, heart) can survive at low temperature for considerable period when deprived of all or a portion of blood supply. </li></ul>
  4. 5. Level of hypothermia; <ul><li>In Small lab. animals recovery rate was 80%-100% just above freezing point with cardiac & respiratory arrest for 1 hr. </li></ul><ul><li>Dog survived cooling to 1.5◦c on pump oxygenator </li></ul>
  5. 6. <ul><li>For induction of quick hypothermia shivering is to be controlled by deep anesthesia or light anesthesia with tranquilization. </li></ul><ul><li>Moderate hypothermia in dog produced rectilinear decrease in anesthetic dose (MAC) for cyclopropane , diethyl ether, fluroxene, halothane, & methoxyflourane. </li></ul><ul><li>Reduces concentration of anesthetic required to produce apnea. </li></ul>
  6. 7. Methods of producing whole body hypothermia <ul><li>1) Surface cooling. </li></ul><ul><li>2) Body cavity cooling. </li></ul><ul><li>3)Extracarporeal method. </li></ul>
  7. 8. <ul><li>Surface cooling :- animal directly imersed in ice cold water or kept in cold matress. It needs hyperventilation to keep blood pH (7.2-7.4) on alkaline side to prevent cardiac arrhythmias & fibrillation. </li></ul><ul><li>Below 28◦c no anesthetic only ventilation required. </li></ul><ul><li>Cooling stopped when approx. ⅔ of desired temp. fall is accomplished </li></ul><ul><li>Body cavity cooling :- pouring cold saline water into open thoracic cavity. </li></ul>
  8. 9. <ul><li>Extracorporeal method :- running blood from a cannulated artery via a heat exchanger with tap water as a cooling medium with the help of a pump. </li></ul><ul><li>Used to lower brain temp. below that of general body temp. by cannulating carotid artery to 14◦c while body temp. remains at 31-32◦c. </li></ul>
  9. 10. <ul><li>Adv: - </li></ul><ul><li>Best control over body temp. & quick rewarming. </li></ul><ul><li>Disadv:- </li></ul><ul><li>Hemolysis. </li></ul><ul><li>Interference with blood coagulation. </li></ul><ul><li>Thrombosis. </li></ul>
  10. 11. Uses :- <ul><li>Surgery of heart, great vessels, brain & spinal cord. </li></ul><ul><li>Treatment of shock, stroke, cerebral & spinal contusion preventing brain damage from severe hypoxic episode. </li></ul><ul><li>Removal of heartworms & repair of cardiac anomalies in dog. </li></ul>
  11. 12. Limitations of hypothermic anesthesia <ul><li>1) cardiac crisis ;- </li></ul><ul><li>Fall of B.P may be drastic due to decreased cardiac output & H.R and increased peripheral resistance. </li></ul><ul><li>In dog cardiac crisis occur b/w 23 & 15◦c characterised by intense bradycardia , ventricular extra- systoles & ventricular fibrillation . </li></ul><ul><li>Hypercapnia , Acidemia,& myocardial hypoxia also lead to ventricular fibrillation , Prevented by adequate ventilation or by some cardioplegic solutions. </li></ul>
  12. 13. <ul><li>Prolonged PR interval , ↑ST interval ,spreading of QRS complex (ECG) </li></ul><ul><li>2) Prolongation of clotting time. </li></ul><ul><li>3) Reduced platelet count. </li></ul><ul><li>4) Decreased Hb conc. </li></ul><ul><li>5)Decreased WBC count. </li></ul><ul><li>6) Decreased MCHC. </li></ul><ul><li>7) Prolonged hypothermia can lead to CV colapse, depletion of cerebral energy stores. </li></ul>
  13. 14. <ul><li>8) Damage to liver , kidney & adrenal glands in dog at 25◦c for hours. </li></ul>
  14. 15. <ul><li>Induction of hypothermia in dog </li></ul><ul><li>Phenothiazine tranquilizer given I/V as preanaesthetic </li></ul><ul><li>Thiobarbiturate (G.A); Endotracheal catheter is inserted </li></ul><ul><li>Inhalant anesthetic for maintenance </li></ul><ul><li>Slow I/V drip of RL / Dextrose 5% & muscle relaxant given </li></ul><ul><li>Controlled respiration is started </li></ul>
  15. 16. <ul><li>Placement/ positioning </li></ul><ul><li>Animal positioned in sink /bathtub/container with head above water </li></ul><ul><li>Electronic thermometer is placed in esophagus @ heart level & rectum </li></ul><ul><li>Electrodes of ECG machine attached to feet – constant monitoring required </li></ul><ul><li>Ice water used for rapid cooling </li></ul>
  16. 17. <ul><li>Dog is removed from bath before reaching of desired temp. </li></ul><ul><li>After removed, place in inactive heating pad during operative period </li></ul><ul><li>Rewarming started at start of surgical wound closure </li></ul>
  17. 18. <ul><li>Rewarmin g:- </li></ul><ul><li>First – placing pads/blankets with circulating warm water or air </li></ul><ul><li>Supplement – warm water bottles and bags </li></ul><ul><li>Warm s/c or i/v fluids approx. 98-99ºF </li></ul><ul><li>Water filled balloons or latex gloves used instead of bottles </li></ul><ul><li>Towels or blankets warmed in dryer and wrapped around patient to trap heat </li></ul><ul><li>Rewarm water bottle frequently </li></ul>
  18. 19. <ul><li>Cautions </li></ul><ul><li>Electric heating pad should not be used </li></ul><ul><ul><li>Severe thermal skin burn may occur </li></ul></ul><ul><ul><li>Skin sloughing can be serious complications </li></ul></ul>
  19. 20. ELECTRONARCOSIS <ul><li>Principle :- electric stimulation of brain activate opiate or non-opiate pain controlling pathway or both thus producing analgesia. </li></ul><ul><li>Clinical trials in vety practice first performed by </li></ul><ul><li>Sir Frederic Hobday in England in 1932. </li></ul><ul><li>Used in situations requiring prolonged anesthesia. </li></ul>
  20. 21. <ul><li>Electrodes operating at A.C (35-50 mAmp & 40V) or D.C or in combination are applied to head. </li></ul><ul><li>Individual variations are adjusted. </li></ul><ul><li>Characterized by convulsions on induction , profuse salivation & hyperthermia. </li></ul><ul><li>Clotting time , ESR , Hb conc. , PCV , total WBC count or DLC do not differ much. </li></ul><ul><li>B.P rises sharply & then gradually falls to near normal level. </li></ul>
  21. 22. <ul><li>No effect on oxygen content of blood. </li></ul><ul><li>Glucose level rises. </li></ul><ul><li>Difficult to assess depth of anesthesia. Muscle relaxation may vary from adequate to poor and surgical pain may cause body movements in apparently unconscious animal. </li></ul><ul><li>Photo motor reflexes are probably best means to determine depth. </li></ul>
  22. 23. <ul><li>Quick recovery following removal of current by slight stimulus & animal resumes all normal activities. </li></ul><ul><li>Merits:- </li></ul><ul><li>Economy and immediate recovery </li></ul>
  23. 24. <ul><li>Demerits:- </li></ul><ul><li>Brain lesions demonstrated. </li></ul><ul><li>Skin burns. </li></ul><ul><li>Severe stress. </li></ul><ul><li>Non-availability of suitable equipments and standardized technique in clinical application. </li></ul>
  24. 25. Acupuncture analgesia <ul><li>Acus – needle; Punctura – to prick </li></ul><ul><li>Current meaning – any type of stimulation (Acupressure, moxibustion, heat, cold, ultrasound, aquapuncture, electro stimulation, implantation and laser) at acupuncture points to produce analgesia or to cure certain diseases. </li></ul><ul><li>Used increasingly in man & animals for producing analgesia. </li></ul>
  25. 26. <ul><li>Used in conjunction with Western treatments- surgery or pharmacological therapy </li></ul><ul><li>History :- </li></ul><ul><li>Existed in India 7000 years ago </li></ul><ul><li>Huang Ti Nei Ching (Yellow emperors classic of internal medicine) – oldest document </li></ul><ul><li>Integral part of Traditional Chinese Medicine- used more than 2500 years to treat diseases and relieve pain </li></ul><ul><li>1921 – Ban in China </li></ul><ul><li>1960s – Maoists regime – reintroduction </li></ul>
  26. 27. <ul><li>Acupuncture points </li></ul><ul><li>Points are called ‘ Xue’ – means ‘cave’ or ‘hole’. </li></ul><ul><li>Eastern countries- specify points different names describing their location or function e.g. ‘wei shu’ means point associated with stomach & is used for gastric diseases but are confusing. </li></ul><ul><li>Western acupuncture practitioners – identify points by number and capital letter abbr. of the meridian to which they belong e.g. BL/UB, LI, ST, SP, GB, etc. </li></ul>
  27. 28. <ul><li>Acupoints differ in their physiological behavior, electrical response,& therapeutic role. </li></ul><ul><li>Reflect various organs on surface of body. </li></ul><ul><li>Small as a pin head. </li></ul><ul><li>Referred as areas of hypersensitivity & lowered electric resistance. </li></ul><ul><li>Located on imaginary horizontal lines k/as MERIDIANS which have internal connections with the organs from which they get their name. </li></ul><ul><li>12 organ meridians like LU, LI, ST, SP, H, SI, UB/BL, K, P, TW, GB, LIV & 2 non-organ meridians GOV(governor vessel) and COV(conception vessel) in large animals. </li></ul>
  28. 29. <ul><li>365 classic points located along the meridians. </li></ul><ul><li>Acc. to Chinese vital energy “chi” flow through these pathways. </li></ul><ul><li>Exact location of points is important – small deviations nullify the response (classic theory) </li></ul><ul><li>Acupuncture points are cutaneous areas with high conc. Of nerves ,mast cells, capillaries ,and venules & lower electrical resistance than surrounding areas </li></ul>
  29. 32. Point location:- <ul><li>Located in small hollow or depression on skin surface </li></ul><ul><li>Are tender compared with surrounding area & response (discomfort) elicited with deep palpation </li></ul><ul><li>Subjective roughness or stickiness appreciated when brushed slightly with finger </li></ul><ul><li>Clinically used points in most species are believed to be 3 – 15 mm below skin surface </li></ul>
  30. 33. <ul><li>Each point has sp. functions and indications for use </li></ul><ul><li>Stimulation of site specific acupoints induces spatially restricted analgesia. </li></ul><ul><li>Each point has sp. functions and indications for use. </li></ul><ul><li>Stimulation of site specific acupoints induces spatially restricted analgesia </li></ul>
  31. 34. <ul><li>Yang organs (hollow organs of the body) </li></ul><ul><li>ST = Stomach </li></ul><ul><li>SI = Small intestine </li></ul><ul><li>LIV = Large intestine </li></ul><ul><li>GB = Gall bladder; bile ducts </li></ul><ul><li>BL= Urinary bladder; ureter & urethra </li></ul><ul><li>TH = Triple heater </li></ul>
  32. 35. <ul><li>Yin organs (solid organs of the body) </li></ul><ul><li>LIV = Liver </li></ul><ul><li>SP = Spleen / Pancreas </li></ul><ul><li>KI = Kidney </li></ul><ul><li>HT= Heart </li></ul><ul><li>LU= Lungs </li></ul><ul><li>PC = Pericardium </li></ul>
  33. 36. <ul><li>Mechanism of action </li></ul><ul><li>Comprehensive mechanism theory (Pomeranx & Stux) :- </li></ul><ul><li>3 mechanisms to A/analgesia </li></ul><ul><li>1. A/ needles stimulate type 1 & 11 afferent nerves or A-∂ fibres </li></ul><ul><li> </li></ul><ul><li>send impulses to AL-tract of spinal cord </li></ul><ul><li> </li></ul><ul><li>Pain blocked presynaptically by release of enkephalin & dynorphin </li></ul><ul><li> </li></ul>
  34. 37. <ul><li>Prevent pain messages from ascending in the spinothalamic tract </li></ul><ul><li>2 A/ stimulate mid-brain structures by activating cells in periaqueductal gray matter & raphae nucleus </li></ul><ul><li> </li></ul><ul><li>send descending signals through DL-tract release of monoamines NE & serotonin in spinal cord </li></ul><ul><li> </li></ul>
  35. 38. <ul><li>Nts. inhibit pain presynaptically & postsynaptically by reducing transmission of signals through spinothalamic tract </li></ul><ul><li>3. Stimulation of pituitary-hypothalamic complex </li></ul><ul><li> </li></ul><ul><li>systemic release of β -endorphin into blood stream from pituitary gland accompanied by release of ACTH </li></ul>
  36. 39. <ul><li>Types of acupuncture </li></ul><ul><li>1. Dry needle acupuncture (invasive methods - a/needle, electro-acupuncture chronic intradermal needle insertion), </li></ul><ul><li>2. Wet needle acupuncture (aquapuncture / non invasive – Aquapressure, Transcutaneous electrical stimulation (TENS), Moxibustion & various stimulating patch and pellets) </li></ul>
  37. 40. <ul><li>Electrical stimulation or electro-acupuncture </li></ul><ul><li>Developed as alternative to manual stimulation of acupuncture points </li></ul><ul><li>Advantages </li></ul><ul><ul><li>Less painful than manual stimulation </li></ul></ul><ul><ul><li>Requires less practitioner time spent with patient </li></ul></ul><ul><ul><li>Provides better analgesia </li></ul></ul><ul><li>Facilitates standardization </li></ul><ul><li>Can be used in balanced anaesthesia to reduce the dose of sedatives/ analgesic & anaesthetics </li></ul>
  38. 41. <ul><li>Good analgesia in high risk patients without producing CNS & resp. depression ,bradycardia, hypotension </li></ul><ul><li>Excellent postoperative pain relief. </li></ul><ul><li>Fast postoperative recovery of appetite & gut and bladder function. </li></ul><ul><li>Fast postoperative wound healing with minimal infection. </li></ul><ul><li>In c-section no depressive effects on the fetus. </li></ul><ul><li>Suitable for prolonged surgery (up to 10 hrs). </li></ul><ul><li>Simple & inexpensive, less hemorrhage. </li></ul>
  39. 42. <ul><li>Electroacupuncture with high-frequency stimulation (100-200 Hz) </li></ul><ul><ul><li>Rapid onset analgesia; cannot be blocked by naloxone </li></ul></ul><ul><ul><li>Mediated by NE, serotonin & dynorphins </li></ul></ul><ul><li>Low-frequency (2-4 Hz) & medium-frequency stimulation (15-30 Hz) </li></ul><ul><ul><li>Analgesic effect reversed by naloxone </li></ul></ul><ul><ul><li>Mediated by enkephalin & endorphins </li></ul></ul><ul><ul><li>Tendency to accumulate; last at least 1 hr after treatment ceases </li></ul></ul>
  40. 43. <ul><li>Disadvantages :- </li></ul><ul><li>Needs very good restraint </li></ul><ul><li>Long induction period (10-40 min ) </li></ul><ul><li>Variable degree of analgesia </li></ul><ul><li>Maintenance of sensation to touch ,pressure & traction </li></ul><ul><li>Poor relaxation of abdominal muscles (cause ballooning of viscera ) </li></ul><ul><li>Nausea ,vomiting & shock </li></ul>
  41. 44. <ul><li>Maintenance of reflexes to sight , sound & fear in conscious animals </li></ul><ul><li>Intrathoracic surgery can’t be performed </li></ul>
  42. 45. <ul><li>Types of operations performed under EAA in dogs </li></ul><ul><li>caesarian section </li></ul><ul><li>OH </li></ul><ul><li>Abdominal laprotomy </li></ul><ul><li>Gastric & intestinal surgery </li></ul><ul><li>Nephrectomy </li></ul><ul><li>Splenectomy </li></ul><ul><li>Umbilical hernioplasty </li></ul><ul><li>Removal of mammary & skin tumors </li></ul><ul><li>Ear cropping </li></ul><ul><li>Craniotomy </li></ul><ul><li>Open reduction & repair of long bone fractures </li></ul>
  43. 46. <ul><li>Types of operations performed under EAA in horse/cattle/sheep/pig </li></ul><ul><li>Castration </li></ul><ul><li>Orchidopexy </li></ul><ul><li>Reposition of prolapsed uterus </li></ul><ul><li>Surgery of anal & vaginal region </li></ul><ul><li>Relief of dystokia </li></ul><ul><li>Surgery of esophagus & rumen </li></ul><ul><li>Repair of naval & umbilical hernia </li></ul><ul><li>Surgery on bladder & urethra </li></ul><ul><li>Orthopedic surgery </li></ul>
  44. 47. <ul><li>Equipment needed:- </li></ul><ul><li>1. Acupuncture needles -22-26 gauze for LA </li></ul><ul><li>26-30 gauze for SA </li></ul><ul><li>Inserted at acupoints to correct depth, taped & sutured firmly at position & connected in pairs to the output socket of an acupuncture electro-stimulator. </li></ul><ul><li>Each pair of electrode should be on same side of the spinal cord </li></ul><ul><li>2 . Acupuncture stimulators:- shd have the following characteristics; </li></ul><ul><li>strength ,portability ,battery operated ,output for atleast 6-8 electrodes </li></ul><ul><li>3. A handheld unit – to locate & stimulate acupuncture & trigger points using 10 Hz ,1-25 v , &1-50 mA. </li></ul><ul><li>4 . A multiple electronic acupunctoscope </li></ul><ul><li>Detects acupuncture& auricular points </li></ul>
  45. 56. <ul><li>Points to be considered while selecting acupoints for surgery; </li></ul><ul><li>Points shd be near to operative site & shd lie on meridian traversing the area. </li></ul><ul><li>Certain points not needled in pregnant animals bcoz of possible risk of abortion. </li></ul><ul><li>All asceptic precautions shd be taken. </li></ul><ul><li>Penetration of needle to small blood vessels not of significance. </li></ul>

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