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Laboratory Animal Science (Subject) / Anaesthesia and introduction to surgical techniques (Lesson)
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- 3 forms of aneasthesia General:– State of total loss of consciousness, resulting from administrationof anaesthetic drugs (narcotics, anaesthetics) that depress thefunction of the brain.Local:– Loss of sensation in a small area of the body, produced byinjecting local anaesthetic drugs, which block nerve conduction.Regional:– Loss of sensation in a region of the body, produced by injectinglocal anaesthetic drugs to all the nerves supplying that region(e.g. epidural anaesthesia).
- triad of aneasthesia Classical triad of anaesthesia:1. reversible loss of consciousness2. Analgesia (unresponsive to a painful stimulus)3. Muscle relaxation induced by the administration of anaesthetic drugs (narcotics) narcotics must cross the blood-brain barrier 2 routes: by injectionby inhalation
- Pre-surgical preparations Animal is fit for the procedure acclimatised to the environment (1-2 weeks after transport) trained to accept the handling (injection, sampling) fasting to prevent vomiting (not rodents or rabbits) should be weighed→ used for drug dose calculations Equipment Instruments and consumables (gloves, swabs, drapes) available and sterile Anasthetic machine, monitoring equipment, operating light (shadowless light source), heat pads, post-surgical care equipment Prepared facility and personnel
- Aims of premedication (aneasthesia) 1. decrease fear, facilitates handling, aid stress-free induction2. reduce the amount of other anaesthetic drugs3. assist smooth recovery from anaesthesia4. reduce salivary, bronchial secretions and bradycardia5. reduce post-operative pain --> Atropins/Tranquillizers/sedatives
- Inhalation anaesthesia (pro/con) Iso/Sevoflurane combined with N2O, O2 or air Pro 1) easy ability to adjust depth of anaesthesia2) rapid speed of induction and recovery3) ability to ventilation Disadvantages: 1) complex and expensive equipment2) requires considerable skills
- Injection anaesthesia (pro/con) Ketamin/Xylazin e.g. 4.25 mL NaCl 0.9% + 0.6 mL Ketamin (10%) + 0.125 mL Medetomidin 0.1% Pro 1) simple to administer2) minimum amount of equipment Disadvantages:1) not controllable2) long recovery time Indications1) Induction of inhalation anaesthesia (intubation)2) short-time anaeshesia3) maintainance anaeshesia using top-up injections orintravenous infusions
- Narcotic stages in small laboratory rodents slight aneasthesia Uncoordinated movementHind body in lateral positionHead restLoss of lid reflexes (eye) Deep aneasthesia Loss of movementsMuscle relaxationLoss of pedal reflex Surgical anaesthesia Asphyxia Cardiopulmonal failure
- Postoperative care / analgesia individual housing until full recovery• heat supply– Infrared heat lamp– Heating blankets• keep the airways open• administration of analgetics– Opiods (Buprenorphine)– NSAID (Carprofen)– Metamizole (Novalgin®)
- Sources of pathogens endogenous:– animal‘s skin– mucous membranes– bowelexogenous:– surgical team– instruments, equipment etc.
- Principles of aseptic technique = Methods used to minimize contamination of the surgical site bycontrolling the potential source of contamination 1. Atmosphere: dust and airborne particles--> minimise air movement, high standard of cleanliness in a room used only for OP 2. Surgical team: abides hygiene rules (outer clothing, protective wear, scrubbing) 3. Instrument and equipment: sterilsed and kept on steril tray/drape, kept sterile through prcedure 4. Skin of the animal: clipping machine, cleaned with swabs and disinfected with iodine/alcohol solution 5. Drape to cover all area exept the surgical site The use of prophylactic antibiotics is not a substitute for goodaseptic technique!
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- Define Haemostasis Risk of excess bleeding• Apply digital pressure using a swab• Artery forceps or clips• Ligation using absorbable suture material• Coagulation of the vessel using cautery
- Goals of aneasthesia/surgery Achieve asepsis and avoid post-operative infections• Minimize inflammation by using good techniques and appropriateinstruments• Minimize bleeding by careful surgery• Produce good wound apposition by using suitable suture material andpatterns• Provide good post-operative care and minimize recovery time Will result in improved science and better experimental data Contribute to improved animal welfare
- Suture material absorbable:vicryl, Polydioxanone (PDS), polyglycolic acid (PGA) forall internal sutures non-absorbable:nylon, polypropylene, supramide for skin sutures has tobe removed either monofilament (single-stranded) or polyfilament (several thin stands woven togheter)