8/5/2012 Workshop Objectives: Understand the concepts of general anesthesia and Monitoring of Anesthesia sedation and the effects of drugs on different body systems Understand monitoring equipment, its limits and proper NOHA ABOU- MADI , D V M , MSC , DIPL ACZM use A A Z A K CONFERENCE SEPTEMBER 2012 Critically assess, identify and correct external factors that SYRACUSE, NY may affect the success of a procedure at induction, during the procedure and recovery Monitor vital parameters, recognize normal changes and problems that need corrections Identify life-threatening emergencies for the animal and the staff Provide excellent care for the anesthetized patient Concepts of general anesthesia, Terminology … sedation and the effects of drugs on different body systems Anesthesia vs. chemical “immobilization” Sedation and general anesthesia Most commonly used anesthetic agents Immobilization: old terminology, still misused Route of absorption: Tranquilization Intravenous (intraosseous), intramuscular, subcutaneous, oral, transmucosal, transdermal, and inhalation (gas) Sedation Some drugs can only be given by one route (propofol: IV) General anesthesia Analgesics (pain killers) Drug delivery stress level Restraint: none, operative conditioning, manual restraint, chutes Administration: oral, hand-injection, stick-pole, remote delivery systems, inhalation 1 8/5/2012 Chute Squeeze cages Remote Administration Devices Use of helicopter and land crew www.thabamanzi.co.za Tranquilizers and sedatives Tranquilizers and sedatives Depress the central nervous system Tranquilizers: phenothiazines (acepromazine), butyrophenones (azaperone, haloperidol): produce Alleviate fear and anxiety of indifference Fear increased cathecolamines irregular heart beats Increased dose tend to increase side effects but no loss of when exposed some drugs consciousness Usually not pain killers (except for xylazine, Sedatives: benzodiazepines (midazolam, zolazepam), medetomidine) thiazine (medetomidine, xylazine), barbiturates: Increased stimulation reverse calming effects produce state of sleep (a.k.a. hypnotics) Keep environment quiet Increased dose produce more profound CNS depression (~ anesthesia) Allow for sufficient time to have peak effect Reversals (antagonists): thiazines, benzodiazepines, Additive / synergetic effect with other anesthetics butyrophenones (antipyramydal effects) 2 8/5/2012 Analgesics also used in anesthetic protocols Induction and maintenance of general anesthesia Opioids: Injectable drugs: morphine, butorphanol (1-2 x morphine), buprenorphine (4-50 x Ketamine, tiletamine (telazol) morphine, dose dependent), fentanyl (75-100 x morphine) Propofol Super - Opioids: carfentanil (10,000 x morphine), etorphine (1000-3000 x Barbiturates morphine), thiofentanyl Single injection or constant rate infusion (CRI) Variable effect on receptors (agonist, antagonist, mixed WARNING: the combination of butorphanol, agonist-antagonists) medetomidine, and midazolam causes heavy In combination can cause neuroleptanalgesia or sedation neuroleptanesthesia Reversals: naloxone (short acting), naltrexone, diprenorphine Induction and maintenance of general anesthesia Other drugs Inhalant anesthetic agents Muscle relaxants Isoflurane Guaifenesin (glyceryl guaiacolate) Sevoflurane Neuromuscular blocking agents Succinylcholine Desflurane Gallamine, atracurium, vecuronium Reversable or not www.mallardmedical.net Tusko Effects of drugs on the animal’s system Effects of drugs on the animal’s system Respiratory system: Gastro-intestinal effects: Depression: decreased effort, slowed rate, increased secretions (obstruction) Vomiting, regurgitation, defecation, diarrhea, constipation, ileus Apnea (respiratory arrest) Kidney function: Decreased swallowing and potential for aspiration pneumonia Decreased blood flow to kidneys decreased excretion of wastes, Cardiovascular system: decreased excretion of drugs (incl. anesthesia), injury from lack of Depression: decreased heart performance and rate, dilation of blood oxygen to cells vessels May cause permanent damage if renal function is already Stimulation: increased heart performance and rate, constriction of blood vessels compromised Decreased blood flow to any and every organ injury to cells and Liver function: compromised function (reversible or not) Decreased blood flow: decreased ability to detoxify (incl. drugs), Musculo-skeletal system: metabolize and excrete drugs Muscle relaxation (excitement from lack of coordination, respiratory depression) Increased enzymatic action: increased metabolism of certain drugs 3 8/5/2012 Effects of drugs on the animal’s system Species specific anatomy and physiology Acid-base balance and electrolytes disturbances Mammals: 4 070 species Secondary to effects on other systems (muscle, GI, kidney) Aves: 10 000 species Nervous system: Reptiles: 6 000 species Depression: ataxia, decreased alertness (decreased ability to prevent drowning, erratic running and impact; inability to Amphibians: 4 000 species evade cage mates and engage in appropriate social response) Fish: 20 000 species Stimulation: seizure, increased muscle activity (ketamine, tiletamine) Invertebrates: > 10 millions species Eyes: Increased pressure inside eye Decreased function of eye lids and potential of exposure and trauma to cornea and retina The best piece of equipment Understand monitoring equipment Limitations and proper use Intmath.com Be prepared for the unexpected OXYGENATION Close monitoring of the To ensure adequate oxygen animal concentration in the inspired Equipment and drugs ready gas and the blood during all to use anesthetics Antagonist Inspired gas: concentration of Emergency drug dosages oxygen in the patient breathing calculated (drawn up?) system shall be measured by an Water / ice oxygen analyzer Oxygen Endotracheal tubes Blood oxygenation Emergency drugs and material Pulse oximetry: calibrated for Fluids humans; many mechanical challenges Bandage material Arterial blood gases: temperature dependent Surgical pack 4 8/5/2012 VENTILATION VENTILATION To ensure adequate ventilation To ensure adequate ventilation of the patient of the patient Qualitative clinical signs: Qualitative clinical signs: Chest excursion, observation of the reservoir breathing bag and Chest excursion, observation of the auscultation of breath sounds reservoir breathing bag and Continual monitoring for the auscultation of breath sounds presence of expired carbon dioxide when patient is intubated: Its correct positioning must be verified by clinical assessment Identification of carbon dioxide in the expired gas: continual end-tidal carbon dioxide analysis: capnography (can depend on blood pressure and lung perfusion) CIRCULATION BODY TEMPERATURE To ensure the adequacy of the To aid in the maintenance of appropriate body patient’s circulatory function temperature during all anesthetics during all anesthetics. Electrocardiogram continuously Rectal temperature probe displayed (only indicates electrical Esophageal temperature probe activity of the heart) Infrared temperature probe Arterial blood pressure Indirect (cuff and doppler) – variation in diameter of legs Direct (intra-arterial catheter) - invasive Palpation of a pulse, auscultation of heart sounds DEPTH OF ANESTHESIA Avoid Unexpected Awareness Loss of righting reflex Jaw tone Position of the eye Ear twitch Loss of palpebral reflex Loss of pedal withdrawal reflex Respiration and circulation Corneal reflex 5 8/5/2012 ASA Physical Status Classification ASA Physical Status 1 - A normal healthy patient ASA Physical Status 2 - A patient with mild systemic disease ASA Physical Status 3 - A patient with severe systemic Critically assess, identify and disease correct external factors that may ASA Physical Status 4 - A patient with severe systemic disease that is a constant threat to life affect the success of a procedure at ASA Physical Status 5 - A moribund patient who is induction, during the procedure not expected to survive without the operation ASA Physical Status 6 - A declared brain-dead patient and recovery whose organs are being removed for donor purposes Planning Physical restraint or general anesthesia? What is the procedure? Is this an emergency? Is the animal tractable? Will the immobilization allow for the procedure? Is the animal trained? Address all safety issues (animal and staff) Make sure the equipment is working (maintenance Do you have access to an animal trained in a squeeze and testing prior to procedure) cage? Training of staff (on going and review) Is the animal small enough to capture (net/hand)? How large is the enclosure or the cage? Planning Planning Determine Pay special attention to animals environmental conditions recently transported or never Temperature immobilized before now Humidity Discuss the behavior of the Time of the day animal and its exhibit mates Intensity of the wind Assess location of immobilization, procedure, if applicable recovery Decide whether it is best to keep the animal with its Determine if method of confinement is safe exhibit mates or isolating it for induction Can the animal be observed post-capture? At all time, decrease sensory stimuli to animal 6 8/5/2012 Planning Pre – Anesthetic Preparation … Meeting before procedure Assignment of tasks Complete the procedure Debriefing post-procedure Pre-anesthetic considerations Which species is involved? Determine the