HYPOTHERMIAHYPOTHERMIA

HYPOTHERMIAHYPOTHERMIA Fall in temperature

Decrease in body metabolism

Decreased oxygen requirement of body

tissues & organs

HYPOTHERMIAHYPOTHERMIA Fall in temperature

Decrease in body metabolism

Decreased oxygen requirement of body

tissues & organs

E.g.1.In dog O2 requirement decreased to 50%

at 30◦c & 65% at 25◦c.

2.Metabolic rate of isolated slices of heart was reduced by 90% at 10◦c.

3.Potassium arrested heart at 37◦c utilizes 4 times glycogen and produces 3

times lactic acid as by heart at 17◦c.

E.g.1.In dog O2 requirement decreased to 50%

at 30◦c & 65% at 25◦c.

2.Metabolic rate of isolated slices of heart was reduced by 90% at 10◦c.

3.Potassium arrested heart at 37◦c utilizes 4 times glycogen and produces 3

times lactic acid as by heart at 17◦c.

• However O2 consumption varies for different organs at a particular temperature.

Conclusion;- vital organs (liver, brain, heart) can survive at low temperature for considerable period when deprived of all or a portion of blood supply.

• However O2 consumption varies for different organs at a particular temperature.

Conclusion;- vital organs (liver, brain, heart) can survive at low temperature for considerable period when deprived of all or a portion of blood supply.

Level of hypothermia;Level of hypothermia;

• In Small lab. animals recovery rate was 80%-100% just above freezing point with cardiac & respiratory arrest for 1 hr.

• Dog survived cooling to 1.5◦c on pump oxygenator

• In Small lab. animals recovery rate was 80%-100% just above freezing point with cardiac & respiratory arrest for 1 hr.

• Dog survived cooling to 1.5◦c on pump oxygenator

• For induction of quick hypothermia shivering is to be controlled by deep anesthesia or light anesthesia with tranquilization.

• Moderate hypothermia in dog produced rectilinear decrease in anesthetic dose (MAC) for cyclopropane , diethyl ether, fluroxene, halothane, & methoxyflourane.

• Reduces concentration of anesthetic required to produce apnea.

• For induction of quick hypothermia shivering is to be controlled by deep anesthesia or light anesthesia with tranquilization.

• Moderate hypothermia in dog produced rectilinear decrease in anesthetic dose (MAC) for cyclopropane , diethyl ether, fluroxene, halothane, & methoxyflourane.

• Reduces concentration of anesthetic required to produce apnea.

Methods of producing whole body Methods of producing whole body hypothermiahypothermia

1) Surface cooling.

2) Body cavity cooling.

3)Extracarporeal method.

1) Surface cooling.

2) Body cavity cooling.

3)Extracarporeal method.

• 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.

Below 28◦c no anesthetic only ventilation required.

Cooling stopped when approx. ⅔ of desired temp. fall is accomplished

Body cavity cooling:- pouring cold saline water into open thoracic cavity.

• 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.

Below 28◦c no anesthetic only ventilation required.

Cooling stopped when approx. ⅔ of desired temp. fall is accomplished

Body cavity cooling:- pouring cold saline water into open thoracic cavity.

• 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.

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.

• 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.

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.

Adv:- Best control over body temp. & quick

rewarming.

Disadv:- Hemolysis.

Interference with blood coagulation.

Thrombosis.

Adv:- Best control over body temp. & quick

rewarming.

Disadv:- Hemolysis.

Interference with blood coagulation.

Thrombosis.

UsesUses:-:-

Surgery of heart, great vessels, brain & spinal cord.

Treatment of shock, stroke, cerebral & spinal contusion preventing brain damage from severe hypoxic episode.

Removal of heartworms & repair of cardiac anomalies in dog.

Surgery of heart, great vessels, brain & spinal cord.

Treatment of shock, stroke, cerebral & spinal contusion preventing brain damage from severe hypoxic episode.

Removal of heartworms & repair of cardiac anomalies in dog.

Limitations of hypothermic anesthesiaLimitations of hypothermic anesthesia

1) cardiac crisis;-

Fall of B.P may be drastic due to decreased cardiac output & H.R and increased peripheral resistance.

In dog cardiac crisis occur b/w 23 & 15◦c characterised by intense bradycardia, ventricular extra- systoles & ventricular fibrillation.

Hypercapnia , Acidemia,& myocardial

hypoxia also lead to ventricular fibrillation , Prevented by adequate ventilation or by some cardioplegic solutions.

1) cardiac crisis;-

Fall of B.P may be drastic due to decreased cardiac output & H.R and increased peripheral resistance.

In dog cardiac crisis occur b/w 23 & 15◦c characterised by intense bradycardia, ventricular extra- systoles & ventricular fibrillation.

Hypercapnia , Acidemia,& myocardial

hypoxia also lead to ventricular fibrillation , Prevented by adequate ventilation or by some cardioplegic solutions.

Prolonged PR interval , ↑ST interval ,spreading of QRS complex (ECG)

2) Prolongation of clotting time.3) Reduced platelet count.4) Decreased Hb conc.5)Decreased WBC count.6) Decreased MCHC.7) Prolonged hypothermia can lead to CV

colapse, depletion of cerebral energy stores.

Prolonged PR interval , ↑ST interval ,spreading of QRS complex (ECG)

2) Prolongation of clotting time.3) Reduced platelet count.4) Decreased Hb conc.5)Decreased WBC count.6) Decreased MCHC.7) Prolonged hypothermia can lead to CV

colapse, depletion of cerebral energy stores.

8) Damage to liver , kidney & adrenal glands in dog at 25◦c for hours.

8) Damage to liver , kidney & adrenal glands in dog at 25◦c for hours.

Induction of hypothermia in dog

Phenothiazine tranquilizer given I/V as preanaesthetic

Thiobarbiturate (G.A); Endotracheal catheter is inserted

Inhalant anesthetic for maintenance Slow I/V drip of RL / Dextrose 5% & muscle

relaxant given

Controlled respiration is started

Placement/ positioning

Animal positioned in sink /bathtub/container with head above water

Electronic thermometer is placed in esophagus @ heart level & rectum

Electrodes of ECG machine attached to feet – constant monitoring required

Ice water used for rapid cooling

Dog is removed from bath before reaching of desired temp.

After removed, place in inactive heating pad during operative period

Rewarming started at start of surgical wound closure

RewarminRewarming:-g:-First – placing pads/blankets with

circulating warm water or air

Supplement – warm water bottles and bags

Warm s/c or i/v fluids approx. 98-99ºF

Water filled balloons or latex gloves used instead of bottles

Towels or blankets warmed in dryer and wrapped around patient to trap heat

Rewarm water bottle frequently

Cautions

Electric heating pad should not be used◦Severe thermal skin burn may occur◦Skin sloughing can be serious complications

ELECTRONARCOSISELECTRONARCOSIS

• PrinciplePrinciple:- electric stimulation of brain activate opiate or non-opiate pain controlling pathway or both thus producing analgesia.

• Clinical trials in vety practice first performed by

Sir Frederic Hobday in England in 1932.

• Used in situations requiring prolonged anesthesia.

• PrinciplePrinciple:- electric stimulation of brain activate opiate or non-opiate pain controlling pathway or both thus producing analgesia.

• Clinical trials in vety practice first performed by

Sir Frederic Hobday in England in 1932.

• Used in situations requiring prolonged anesthesia.

• Electrodes operating at A.C (35-50 mAmp & 40V) or D.C or in combination are applied to head.

• Individual variations are adjusted.

• Characterized by convulsions on induction , profuse salivation & hyperthermia.

• Clotting time , ESR , Hb conc. , PCV , total WBC count or DLC do not differ much.

• B.P rises sharply & then gradually falls to near normal level.

• Electrodes operating at A.C (35-50 mAmp & 40V) or D.C or in combination are applied to head.

• Individual variations are adjusted.

• Characterized by convulsions on induction , profuse salivation & hyperthermia.

• Clotting time , ESR , Hb conc. , PCV , total WBC count or DLC do not differ much.

• B.P rises sharply & then gradually falls to near normal level.

• No effect on oxygen content of blood.

• Glucose level rises.

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.

• Photo motor reflexes are probably best means to determine depth.

• No effect on oxygen content of blood.

• Glucose level rises.

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.

• Photo motor reflexes are probably best means to determine depth.

• Quick recovery following removal of current by slight stimulus & animal resumes all normal activities.

Merits:-Merits:- Economy and immediate recovery

• Quick recovery following removal of current by slight stimulus & animal resumes all normal activities.

Merits:-Merits:- Economy and immediate recovery

Demerits:-Demerits:-

Brain lesions demonstrated.

Skin burns.

Severe stress.

Non-availability of suitable equipments and standardized technique in clinical application.

Demerits:-Demerits:-

Brain lesions demonstrated.

Skin burns.

Severe stress.

Non-availability of suitable equipments and standardized technique in clinical application.

AcupunctureAcupuncture analgesia analgesia

Acus – needle; Punctura – to prick

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.

Used increasingly in man & animals for producing analgesia.

Used in conjunction with Western treatments- surgery or pharmacological therapy

History:-Existed in India 7000 years ago

Huang Ti Nei Ching (Yellow emperors classic of internal medicine) – oldest document

Integral part of Traditional Chinese Medicine- used more than 2500 years to treat diseases and relieve pain

1921 – Ban in China

1960s – Maoists regime – reintroduction

Acupuncture pointsAcupuncture points

Points are called ‘Xue’ – means ‘cave’ or ‘hole’.

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.

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.

Acupoints differ in their physiological behavior, electrical response,& therapeutic role.

Reflect various organs on surface of body.Small as a pin head.Referred as areas of hypersensitivity &

lowered electric resistance.Located on imaginary horizontal lines k/as

MERIDIANS which have internal connections with the organs from which they get their name.

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.

365 classic points located along the meridians.

Acc. to Chinese vital energy “chi” flow through these pathways.

Exact location of points is important – small deviations nullify the response (classic theory)

Acupuncture points are cutaneous areas with high conc. Of nerves ,mast cells, capillaries ,and venules & lower electrical resistance than surrounding areas

Point location:- Point location:-

Located in small hollow or depression on skin surface

Are tender compared with surrounding area & response (discomfort) elicited with deep palpation

Subjective roughness or stickiness appreciated when brushed slightly with finger

Clinically used points in most species are believed to be 3 – 15 mm below skin surface

Each point has sp. functions and indications for use

Stimulation of site specific acupoints induces spatially restricted analgesia.

• Each point has sp. functions and indications for use.

• Stimulation of site specific acupoints induces spatially restricted analgesia

Yang organs (hollow organs of the body)

ST = StomachSI = Small intestine

LIV = Large intestineGB = Gall bladder; bile ducts

BL= Urinary bladder; ureter & urethraTH = Triple heater

• Yin organs (solid organs of the body)

LIV = LiverSP = Spleen / Pancreas

KI = KidneyHT= HeartLU= Lungs

PC = Pericardium

Mechanism of action Comprehensive mechanism theory

(Pomeranx & Stux) :-3 mechanisms to A/analgesia1. A/ needles stimulate type 1 & 11

afferent nerves or A-∂ fibres send impulses to AL-tract of spinal cord Pain blocked presynaptically by release

of enkephalin & dynorphin

Prevent pain messages from ascending in the spinothalamic tract

2 A/ stimulate mid-brain structures by activating cells in periaqueductal gray matter & raphae nucleus

send descending signals through DL-tract

release of monoamines NE & serotonin in spinal cord

Nts. inhibit pain presynaptically & postsynaptically by reducing transmission of signals through spinothalamic tract

3. Stimulation of pituitary-hypothalamic complex

systemic release of β-endorphin into

blood stream from pituitary gland accompanied by release of ACTH

Types of acupuncture

1. Dry needle acupuncture (invasive methods - a/needle, electro-acupuncture chronic intradermal needle insertion),

2. Wet needle acupuncture (aquapuncture / non invasive – Aquapressure, Transcutaneous electrical stimulation (TENS), Moxibustion & various stimulating

patch and pellets)

Electrical stimulation or electro-acupuncture

Developed as alternative to manual stimulation of acupuncture points

Advantages◦Less painful than manual stimulation◦Requires less practitioner time spent with

patient◦Provides better analgesia

Facilitates standardization

Can be used in balanced anaesthesia to reduce the dose of sedatives/ analgesic & anaesthetics

Good analgesia in high risk patients without producing CNS & resp. depression ,bradycardia, hypotension

Excellent postoperative pain relief.

Fast postoperative recovery of appetite & gut and bladder function.

Fast postoperative wound healing with minimal infection.

In c-section no depressive effects on the fetus.

Suitable for prolonged surgery (up to 10 hrs).

Simple & inexpensive, less hemorrhage.

Electroacupuncture with high-frequency stimulation (100-200 Hz)◦Rapid onset analgesia; cannot be blocked by

naloxone◦Mediated by NE, serotonin & dynorphins

Low-frequency (2-4 Hz) & medium-frequency stimulation (15-30 Hz)◦Analgesic effect reversed by naloxone◦Mediated by enkephalin & endorphins◦Tendency to accumulate; last at least 1 hr after

treatment ceases

Disadvantages:-

Needs very good restraint

Long induction period (10-40 min )

Variable degree of analgesia

Maintenance of sensation to touch ,pressure & traction

Poor relaxation of abdominal muscles (cause ballooning of viscera )

Nausea ,vomiting & shock

Maintenance of reflexes to sight , sound & fear in conscious animals

Intrathoracic surgery can’t be performed

Types of operations performed under EAA in dogs

caesarian section OH Abdominal laprotomy Gastric & intestinal surgery Nephrectomy Splenectomy Umbilical hernioplasty Removal of mammary & skin tumors Ear cropping Craniotomy Open reduction & repair of long bone fractures

Types of operations performed under EAA in horse/cattle/sheep/pig

Castration

Orchidopexy

Reposition of prolapsed uterus

Surgery of anal & vaginal region

Relief of dystokia Surgery of esophagus & rumen

Repair of naval & umbilical hernia Surgery on bladder & urethra Orthopedic surgery

Equipment needed:-

1. Acupuncture needles -22-26 gauze for LA 26-30 gauze for SA• Inserted at acupoints to correct depth, taped &

sutured firmly at position & connected in pairs to the output socket of an acupuncture electro-stimulator.

• Each pair of electrode should be on same side of the spinal cord

2. Acupuncture stimulators:- shd have the following characteristics;

strength ,portability ,battery operated ,output for atleast 6-8 electrodes

3. A handheld unit – to locate & stimulate acupuncture & trigger points using 10 Hz ,1-25 v , &1-50 mA.

4. A multiple electronic acupunctoscope Detects acupuncture& auricular points

Points to be considered while selecting acupoints for surgery;

Points shd be near to operative site & shd lie on meridian traversing the area.

Certain points not needled in pregnant animals bcoz of possible risk of abortion.

All asceptic precautions shd be taken.

Penetration of needle to small blood vessels not of significance.