Administration routes for anesthesia Aurora Brønstad Veterinarian - PhD Administration routes for anesthesia Administration of anesthesia General anesthesia Local anesthesia • Injection • Injection • Inhalation • Spray – (mammals) • Topical Liniment • Absorption over gills • Gel – (fish) • Cream Percutan absorption • • Plaster – (fish larvae) Administration routes for anesthesia Injection Anesthesia Administration routes for anesthesia Injection anesthesia Advantages: Inexpensive equipment: syringes and needles Anesthetic DemDemands limited knowledge of aanatomy and technical skills. drug Disadvantages: administered Easy to overdose by syringe Limited possibilities to rreverse effect Long awakening process – and often long induction-time Locally irritating Administration routes for anesthesia Injection anesthesia Routes of administration A: intravenous (i.v.), B: intramuscular (i.m.) C: intraperitoneal (i.p.) D: subcutaneous(s.c.) Administration routes for anesthesia Injection anesthesia Routes of administration A: intravenous (i.v.), B: intramuscular (i.m.) C: intraperitoneal (i.p.) D: subcutaneous(s.c.) Administration routes for anesthesia EC 50 Injection routes and concentration in blood 12 10 8 iv 6 im EC50 sc 4 2 Concentration in blood Concentration 0 0 1 2 3 4 5 6 7 Time Administration routes for anesthesia Injection anesthesia – maximum injection volume 200 g rat Adm.route Max volume Comments s.c. (under skin) 5 ml Large volumes, slowly injected i.m. (in a muscle) 0.2 ml Divided on several places i.p. up to 10 ml Isotone solutions (intra peritoneal) only for large volumes i.v. 2 ml use 1-2 min Administration routes for anesthesia Calculate maximum injections volumes • Rat 200 g • Ketamine: 60 mg/kg i.m. – Use Ketalar Ò 50 mg/ml • What is the injected volume for this drug? • What are the recommendations? Administration routes for anesthesia Intravenous access Injection anesthesia in tail vein • Place the animal in an incubator – (32-34ºC) for 20 min – Cause dilatation of the vein • Use lamp to transluce the tail and vein through the cleft and to maintain heating of tail • Dim the light in the room to enhance contrast • Insert a vein catheter (yellow 24G) in tail vein • Fix vein catheter to tail with adhesive tape Administration routes for anesthesia Inhalation anesthesia Anesthetic drug administered through the airways Administration routes for anesthesia Anesthesia gas is Vaporizer inhaled, absorbed in lungs and distributed to the brain Flowmeter Fresh gas Administration routes for anesthesia Inhalation anesthesia - Induction The old way “OPEN JAR” – Animal is placed in a chamber with a piece of cotton drenched in an anesthesia solution Advantages: Cheap Disadvantages: Hard to control depth of anesthesia Irritating for airways Leak to surroundings/Health safety issues Administration routes for anesthesia Inhalation anesthesia - Induction The old way “OPEN JAR” – For very short procedures (<min), Temp = 20 °C pressure 1 atm, 1 ml liquid isoflurane evaporate to 182 ml – 0,11 ml liquid isoflurane in 500 ml jar will give a isoflurane concentration of 4% witch is safe for induction – After induction the animal must be removed and will recover within 60 seconds Administration routes for anesthesia Induction: Anesthesia chamber • Induction in chamber is safer and better controlled if chamber is connected to a anesthesia machine Administration routes for anesthesia Intubation Administration routes for anesthesia Anesthesia machines Advantages Reliable in use Supply a known concentration of oxygen and anesthesia gas. Easy to regulate depth of anesthesia Stable anesthesia over longer time-period Can be linked to respirator Disadvantages Expensive Demands technical knowledge and experience to operate Maintenance Administration routes for anesthesia Maintenance of gas anesthesia • After induction of anesthesia - maintenance anesthesia by use of mask or tube connected to anesthesia machine provide a stable and reliable anesthesia Administration routes for anesthesia Anesthesia fish Administration routes for anesthesia Gas anesthesia: Health and safety issues Organize the workday so you can take a Short break every hour. Do some stretching. Rise from your chair and leave the room. Get some fresh air and daylight. Drink a small glass of water every hour. Make sure you get a proper lunch break during the day. Do not work alone, or have someone check in on you regularly AddressedAdministration in Health routes for Hazard anesthesia lecture !! Alternative to gas anesthesia • Gas anesthesia is among alternatives closest to the ideal anesthetic. However there are occasions where gas anesthesia cannot be used, mainly due to health-environment-safety issues • As an alternative: • Use a short acting injection anaesthesia like propofol iv. • Propofol is not accumulating in tissue fat and therefore it gives a shorter recovery when infusion is stopped. • Induction using Hypnorm: 0,5 - 1,0 ml/kg i.p. After establishing i.v. access a bolus dose of 2.6-3-3 mg/kg (0,26-0.33 ml/kg Propovet® 10mg/ml) is given intravenously and then maintained by infusion rate: 40-60 mg/kg/h (4-6 ml/kg/h) i.v. using a syringe pump. Administration routes for anesthesia Use of neuromuscular blockers • Agents that block neuromuscular transmission are used to abolish muscle tone during anesthesia in man and animals. • Commonly used in human medicine • Special care is necessary when such pharmacological compounds are used systemically because they specifically block neuromuscular transmission causing paralysis, yet have no significant central effects and will not therefore induce analgesia, unconsciousness or even sedation. • If administered to a conscious animal they would not prevent it feeling pain and the animal would be in a helpless state of paralysis. • Anesthetic protocol has to be well documented Administration routes for anesthesia Acta Anaesthesiol Scand. 2004 Oct;48(9):1144-54. BACKGROUND: Neuromuscular blockade should, for ethical reasons, not be allowed in animal experiments unless the use is strongly motivated. Beforehand, the anaesthetic protocol must be documented without muscle relaxation in the species studied. Documentation is difficult to obtain from the scientific literature. When focusing on cardiac function over time, in particular, the ideal anaesthetic protocol should cause no or minor alterations in cardiac variables. Administration routes for anesthesia Choice of anesthesia product • Scientific and animal-welfare considerations: • The anesthesia products’ potential interaction with the research-protocol • Ability to give satisfying degree of anesthesia • Other factors • Reliability in use with other equipment • Competence and Skills • Costs Administration routes for anesthesia .