Anesthesia
- 2. • Greek word meaning absence of sensation an for "without" and esthesia for "sensibility". • Animal can not feel pain when anesthesia is induced • Anaesthetic is the substance used to induce anesthesia Principles of anesthesia • Depresses activity of CNS, patient can not perceive pain Anesthesia
- 4. A brief History of Anesthesia • Ether was first used as anaesthetic (1846) • Un till 1846, people used alcohol, opium, cannabis and even concussion and asphyxiation. • Horace Wells used nitrous oxide as anesthethetic for the first time. • James Simpson introduced chloroform in 1847. • Cyclopropane in1929 • Halothane in 1965 and revolutionized inhalant anesthesia.
- 5. Reasons for Anesthesia • Alleviate pain • Immobilize patient • Protect patient from injury • Prevent injury to surgeon • Prevent injury to assistant
- 6. Classification of Anesthesia General Anesthesia Local Anesthesia Regional• Injectable (Ketamine, Propofol) • Inhalant (Isoflurane, Sevoflurane) • Injectable • Topical/Spray • Infiltration Lignocaine Maintenance Anesthesia = Top up Requires anesthetic working station
- 7. Routes Of Administration Local – application on surface - Infiltration at the site Regional – injection over main nerve trunk General – Intravenous or intramuscular injection - inhalation Routes of drug administration is always written on the vial
- 8. Preanestetic - given before general Induction anesthesia to - restrain - reduce anxiety - Smooth induction - smooth recovery - Reduce dose of General anaesthetic e.g. Xylazine, Triflupromazine Local – e.g. Lignocaine HCL General - Thiopentone Sod, Ketamine, Propofol= Induction Anesthetics
- 9. Preanestetic •Anticholinergics •Tranquilizers •Sedatives •Analgesics/Opiod(Morphine) •Combinations
- 10. Anticholinergics: 1. Atropine. • Decreases respiratory, oropharyngeal and eye secretions • Counteracts bradycardia induced by Xylazine • Dose rate (pre-anesthetic) • → 0.065 mg/kg IV, IM, SQ Contraindication :- As atropine dilate the pupil, if animal is placed directly in sun light retina may get damage. ( Tell Owner to observe the Dogs) Rabbits is refractory to atropine due to enzyme atropinase
- 11. 2. Glycopyrolate: • Decrease Respiratory, Oropharyngeal, GIT, Eye secretion etc. • Longer duration than atropine • Dose: 0.01mg/kg • Used commonly in L.A Tranquilizers •Relieve anxiety •To quiet patient •Physical Examination •Transportation • Prevent Licking wounds • Chewing bandages/splints • Antiemetic e.g. car sickness
- 12. Agents • Chlorpromazine • Promazine • Triflupromazine • Acepromazine -ACE Hypotensive: Aggressive fluid therapy Epinephrine contraindicated Doses •Dog 0.03-1 mg/kg •Cat 0.03-1 mg/kg •Horse 0.02-0.05 mg/kg Acepromazine
- 13. Tranquilizers continued.. 2. Benzodiazepines (Diazepam) • Muscle relaxant property • Anticonvulsant • Given with ketamine (mixture) 1:2 • Calming effect Dose Dog /cat • 0.1-0.5 mg /kg Horse • Dose: 0.05- 0.2 mg/kg IV Cattle Dose: 0.5-1.0 mg/kg IM 0.2 mg/kg IV
- 14. Opioids/Analgesics • Not commonly used except in human medicine under the prescription of the Doctor Except in wild animal restraint as dart gun. • Fentanyl patch: in dog Etorphine: • X 80-1000 Morphine • IM--Hand held syringe or dart • Animal remains on feet can be approached Nalorphine (Antagonist)
- 15. Sedatives Alpha2 agonist Drugs •Xylazine: Yohimbine as antagonist •Medetomidine: Tolazoline as antagonist •Detomidine •Dexmedetomidine •Romifidine Actions •Analgesia •Sedation •Anxiolysis •Muscle relaxation •Anticonvulsant
- 16. Xylazine: • Used mostly as preanestetic in small animals. • Never use in Cats • Causes bradycardia which can be counteracted by atropine • Causes vomitions in dogs and cats Doses Dog/cat : (1 mg/kg) Horse (1.1 mg/kg) Cattle (0.1 mg/kg)/ 1/10th of the Horse Administer Anticholinergics before administration in dogs and cat
- 18. Anesthetic Combinations 1. Combinations of : - Ketamine (50mg/ml) – 5 ml - Diazepam (5mg/ml) - 0.5 ml - Siquil (20mg/ml) – 1 ml Given IV @ 1 ml per 4.5 kg body weight In a syringe Used at NAH Chubachu, Thimphu Or refer the HSI protocol chart
- 19. 2. Vets beyond borders (VBB). Pre-anesthetics – combination of - Xylazine (20mg/ml) @ 1ml/10kg (max 2ml only) (Pups < 6 months @ 0.03ml/kg - Atropine Sulphate (0.6mg/ml) @0.2ml/10kg Induction by IV injection - Diazepam (5mg/ml) 0.5ml - Ketamine (50mg/ml)0.5ml 1ml of mix/10kg
- 20. Site for General Anesthesia - dogs Recurrent tarsal vein Cephalic vein
- 21. Drugs and Dosages Weight × dose rate ÷ concentration = Total volume needed • The Concentration of the drug has to be found out from the drug vial while dose rate has to be known by you. • Concentration of the drug is always in mg/ml and not in %. • Always convert the % (If given in %) into mg/ml to calculate the dosage of the drug. • Remember 1000mg/ml= 100%
- 22. Activity • Dog wt. = 20 kg • Dose rate of drug = 0.2 mg/kg • Concentration of drug in vial = (2%) 1. Calculate the volume of the drug to be given? 2. Calculate the quantity of Fasinex 250 mg tablet for sheep weighing 75 kg at the dose rate of 10mg/kg bwt?