The Real Anaesthesia Handbook PDF

N.O’R. K.L.  I d ci This is a compilation of the questions we were asked on EMS and the Anaesthesia rotation. Whenever figures or equations are mentioned, it is good to know them. We have not included the main adverse effects of the various drugs/drug cla...

N.O’R. K.L.  I d ci This is a compilation of the questions we were asked on EMS and the Anaesthesia rotation. Whenever figures or equations are mentioned, it is good to know them. We have not included the main adverse effects of the various drugs/drug classes, mostly more specific things to consider when using them. Where possible, we have stressed the questions that are commonly answered incorrectly, and the correct answers. Towards the end there are brief special case examples, the TPR values they work off and also the basics of filling in the anesthetic chart. Disclaimer: while we have gone to every effort to make sure absolutely all information in this document is correct, we cannot guarantee it. Please feel free to add to this document and re-upload it. Ga Va e ET – end tidal. ETCO is CO exhaled. Normal. to – to lower this increase RR and tidal vol. can allow this to build up near end of op to stimulate spontaneous breathing. Fi – fractional/fresh inspired – (CO should be but is just above because of CO in dead space gets rebreathed. When increased more its due most often to low of O flow but could be exhausted calcium carbonate in circle or rebreathing Tidal volume – size of breath. - ml/kg. so start ventilator at this vol at bpm and adjusts according to CO readings Minute ventilation – RR X tidal volume B dP e e Most accurate parameter here is mean arterial pressure (MAP MAP Cardiac output x systemic vascular resistance Measured best with central arterial line so with this want MAP but can also be measured oscilometrically but it over estimates a bit so want it. Renal autoregulation is lost at systolic pressures mmHg Myocardial perfusion is inadequate if diastolic pressure mmHg Brain autoregulation lost and mmHg Invasive blood pressure: arterial catheter in dorsal pedal artery (dogs or facial artery in horses. Catheter opening facing blood flow. A pressure bag of heparinized saline ( mmHG is used to fill a non-compliant narrow length of tubing with a column of heparin saline. The transducer is then placed at the level of the left ventricle. The transducer works by measuring the change in electrical resistance through a thin membrane. This membrane is in contact with the column of heparin saline and therefore it moves in accordance with pressure exerted by the force of contraction (that is to say blood pressure , changing resistance and giving a numerical figure for blood pressure. If it is below the level of the left ventricle, systolic pressures are falsely increased as gravity is acting on the water column. Once the line is filled with water, it must be “zeroed” at atmospheric pressure. This involves opening the way tap to the atmosphere and zeroing. This gives us an accurate reading of blood pressures, as blood pressure is measured relative to gravity (Jo – “think of it as zeroing a bowl before putting flower into it”. If there are air bubbles or blood clots in the line, or the tubing is too compliant, we get “damping” of the readings – ie pressures are over estimated. Flush system periodically to prevent this. Blood Pressure Cardiac Output x Systemic Vascular Resistance - very good to know this equation, if asked. Cardiac Output HR x Stroke Volume Stroke Volume End Diastolic Volume – End systolic Volume Therefore Blood Pressure Hr x (end diastolic volume - end systolic volume x SVR. Stroke volume is the volume of blood pumped out of the heart when the ventricles contract. To increase stroke volume:. Inc preload: give CSL fluid bolus, usually at ml/kg.. Inc contractility: dobutamine. Dec afterload: ACP → vasodilation → decreased systemic vascular resistance → the heart can pump more blood out with each contraction as there is less resistance. An epidural often decreases blood pressure as the sympathetic trunk is located either side of the spinal column, the anaesthetic used can spread out to the trunk blocking it → sympathetic tone decreases → vasodilation ( a parasympathetic action → hypotension. There will also be a paradoxical bradycardia with this as a normal sympathetic reflex tachycardia to vasodilation, cannot occur because signals travelling through the sympathetic system are blocked by the epidural. Alpha agonists increase SVR by causing peripheral vasoconstriction. This can be good if the animal is likely to be hypotensive during surgery. List of steps to take when blood pressure decreases intraoperatively: Claire made this list, she loves to ask it and talk about it. Must be followed in this order.. If it decreases due to the animal being too deep, decrease the iso. Vasodilation is the most important side effect of iso, they ask you this all the time.. If it is due to bradycardia, give an anticholinergic ie atropine or glycopyrrolate.  Atropine can cross the BBB and can cause seizures. Glyccopyrolate does not so it is used more. As these Atropine should not be given to a horse with colic as the anticholinergic effects cause GIT stasis which will worsen the colic.. If due to hypovolaemia give fluids, less than dehydration can’t be seen, so can presume that animals are often bit dehydrated. But in an animal with hypoproteinaemia there will not be enough colloid osmotic pressure to hold the fluid in the vascular compartment (potentially leading to pulmonary and cerebral oedema , it will leak out and result in oedema. In this case you would give both colloid (to increase onchotic pressure in the vascular compartment and chystalloid (because choloids are being infused, this will hopefully now be held in the vascular compartment fluids, each at maintenance dose. So a dog that’s a bit dehydrated and vasodilated due to iso will be susceptible to having low blood pressure.. If the volume is okay, give dobutamine (positive ionotrope working on b receptors , this increases contractility. But will cause arrythimias at high doses, so bare in mind for patients that already have arrythmias. Do not say that dobutamine increases heart rate, it does not. Dobutamine CRI is one of the few CRI’s that does not require a loading dose, due to its T / being only a matter of seconds.. Worst case scenario give adrenaline (vasoconstrictor. But this will drive the blood pressure and heart rate through the roof. Also worry about cutting off the blood supply to vital organs at very high doses e.g. spleen can cause splenic entrapment in a horse A h ia Heart Blocks: First Degree Block: transmission through the AV node is slower → prolonged interval between P wave and QRS complex. Second degree Block: Some impulses are conducted from the atria to the ventricles but some are not. Type and type. Can be brought on by Alpha- -agonists. ○ Type : “Wenkeback Periodicity”. P-R interval gradually increases until there is a blocked beat, this is then followed by a sinus beat. The cycle then repeats itself. This is a “physiological normal arrythimia” seen in GIT surgeries where the vagus Nerve is stimulated → increased parasympathetic tone. Also seen in young fit racehorses as they have a high vegal tone. Will disappear if they are trotted or often at induction because the horse is nervous. ○ Type : P-r interval is consistent but the occassional P-waves fails to conduct a QRS complex. This is commonly due to disease of the AV nerve fibres. Third Degree Block: none of the P waves conduct to the ventricle, thus the atria and ventricles beat independently of each other. P wave formation is due to the SA node. A ventricular pacemaker → ventricular escape rhythm. The escape rhythm is keeping the animal alive in this situation, don’t mess around with it. Ventricular Premature Contraction (VPC : due to an ectopic focus in the ventricles firing off before the SA node has generated its next impulse. Identified on ECG by: QRS widened due to slow conduction through the ventricles. Lack of a preceeding P wave for the QRS. When a VPC occurs before the ventricles have time to fill up properly (ie at this exact moment they are said to have a low end diastolic volume , you get a pulse deficit( the heart can be seen and heard to beat but there is no peripheral pulse to match this beat O ge Sa a i : Pulse-ox/ SP This is how much the hemoglobin is saturated with oxygen, not the blood as a whole, the importance of which is below. Should be or over. Must be as this correlates with SAO (arterial blood ox saturation of , which below this is severe hypoxemia. Low values: as a result of low partial pressure of oxygen, due to Too little oxygen being pumped into the fresh gas, this should be indicated on the Fi reading on the machine. Upper airway blockage eg kinked ET tube  Pulmonary disease- this stops oxygen from crossing the blood-gas barrier. V/Q mismatch: You will asked this during an equine surgery. In an equine surgery when the horse is in dorsal recumbency, gravity forces more blood to flow into region of the lungs closest to the ground (these are the dorsal lung lobes, when the horse is standing. This causes atalectasis of the alveoli. The situation that arises is: there is now more blood going to an area where gas exchange is not occuring → this is V/Q mismatch (V:Q ratio approaching. SPO decreases as the hemoglobin going to these regions of the lungs is not picking up and hence hemoglobin saturation is falling. Low V:Q ratio- an area of the lungs is being over perfused and under ventilated. CO builds up in these areas quickly. High V:Q ratio – an area is being over ventilated and under perfused. CO is low in these areas. Pulse ox falsely high readings: Anaemia: by definition there are decreased numbers of RBCs, so there is less O being delivered to the tissues around the body. However, the Hb in the RBCs that are left i a a ed. Therefore when the pulse-ox reads these, it sees that these RBCs are saturated with O but it doesn’t account for the fact that are very few of them. High concentration of MetHb. Due to onion or fertilizer poisoning, mucous membranes appear brown. Alpha- -agonists → peripheral vasoconstriction → makes it difficult for a pulse ox to read values when it is on the tongue of some dogs. Ca ga h This is a major topic ETCO end -tidal CO (this is the measure of ventilation , this is the amount of the CO being expired by the animal and should reflect the CO partial pressure at the alveoli. ETCO Range:. - KPa A high ETCO is caused by hypercarbia, d e h e ia i.I i ca ed b h ia h ae ia a he de i a i f he e The reason they ask this is to see if students will say either of the former. To treat hypoventilation use IPPV (increasing resp rate and/or tidal volume , decrease gas anesthetic agent Increased ETCO : ▪ Rebreathing-nb indicator here is that the trace does not return to baseline between exhalations. Co high levels in the fresh gas ▪ Increased metabolic rate due to - being too in too light a plane of anaesthesia, seizure or malignant hyperthermia ▪ Hypoventilation- most likely cause ▪ Endobronchial intubation- inc’d PaCO , dec’d PaO. This is because oxygen is only getting into that bronchus and CO is only being blown off the area supplied by that bronchus. Effects of hypercapnia Cerebral vasodilation, splanchnic vasoconstriction, myocardial depression (masked by hypertension/bounding pulse, tachycardia, tachypnoea. These can easily be confused with the animal being too light Later: oozing wounds, tachycardia with arrhythmias and CARDIAC ARREST Decreased ETCO : ▪ Dec’d cardiac output- when sudden cardiac arrest occurs, the heart stops perfusing the lungs, therefore the blood stops off-loading CO into the alveoli. Seen on capnogram usually as consecutive decreasing waves and a then a flat line. This formation is also seen with pulmonary embolism. ▪ Hyperventilation ▪ hypothermia ▪ Decreased metabolic rate ▪ Et tube problem- disconnection or leak ETCO detects problems with equipment also: ▪ ET tube in oesophagus – CO just flat line or tiny bumps from gastric CO ▪ ET tube not patent ▪ Loose connection ▪ Soda lime exhausted. → rebreathing CO , capnogram doesn’t go back to flatline for inspiration ▪ High ETCO in Circle System: one way valves not working. Often because they are stuck due to buildup of moisture  ▪ High ETCO in Non-rebreathing systems: fresh gas flow not high enough. ▪ Ca di ge ic ci a i : this is seen in the CO capnogram. You see small peaks in the CO spikes. This is caused by ventricles of the heart filling, creating waves in lung tissue altering CO levels. The peak in curve is expiration and the low is inspiration. ▪ Pe i i e H e ca ea this is where the ETCO is allowed to build up over an extended period of time. It is different to the above in that this is done while the animal is still under GA, the aim is stimulate the sympathetic nervous system causing increased heart rate and blood pressure. CO is also allowed to build up towards the end of surgery to stimulate spontaneous breathing. If a complex forms on the capnograph out of synch, it is usually due to the animal breathing on its own against the machine or it can also be due to someone pressing on the belly causing the animal to exhale. Increased PIP will be seen. While hypercarbia is Seen at an ETCO. , in this scenario the animal is allowed go well above mmHg CO. A ae he ic Ga e MAC is the concentration of gases at which of patients will react to noxious stimuli. The mac of Iso is.. Vasodilation caused by ISO is especially strong in the horse. A lot of times during surgery, the ETiso will be below MAC, this is because many animals in UCDVH are induced with MAC sparing drugs like opioids and Alpha- -agonists. Also bare in mind that make only refers to of animals. If an animal is getting light under anaesthesia, turn up gas at vapouriser and also turn up oxygen flow as the iso vapour is carried into the alveoli in the oxygen → faster delivery. In the vapouriser, there is a chamber where the gas is completely saturated with isoflurane. When the vapouriser setting is turned up, a higher of the carrier gas (usually oxygen is diverted into this chamber. As a higher percentage of the carrier gas is now saturated by isoflurane, the animal will inhale more isoflourane. May want top up of propofol before this. Depends on what stage of op you are at, near end may just top up propofol and leave iso alone, but at start of op increase both.  D g M hi e- Vomiting caused by morphine is because it makes the animal feel nauseous. If there is risk of morphine causing vomiting, premed the animal with pethidine or methadone. When the animal has been induced, they can no longer consciously feel nauseous, so morphine can then be given in a CRI for example without the risk of vomiting. It can also be given after a painful operation without risk of vomiting because the pain prevents vomiting. Rapid injection → histamine release Pure mu agonist so can lead to excitement before sedation - for this reason, in a horse that is getting a premed of morphine (or any pure mu agonist and an alpha agonist, give the alpha agonist first to cause sedation and prevent excitement caused by the opioid. Morphine is a cheap drug Me had e- ▪ Less cardiovascular effects, use on patients with cardio problems ▪ Panting can be seen after injection, this is most relevant to brachycephalics recovering. They usually work away with methadone when brachycephalics are getting anaesthetized but it is a good thing to know. ▪ Not as good a sedation as morphine or pethidine. ▪ Methadone and morphine have the same doses. Pe hidi e ▪ Analgesia is as good as methadone but has greater sedation ▪ Analgesia lasts around mins, ▪ Anticholinergic effects so it can increase heart rate. Only opioid like this. (discovered by accident while researching anticholinergic drugs ▪ D gi e IV , leads to massive histamine release. IM route only. Wi be a ed hi ▪ Expensive ▪ Lasts - hrs, morphine and methadone are hours. ▪ Does not cause vomiting like other opioids  B ha - Good sedation but poor analgesia. The dose required to bring about analgesia is much higher than that for sedation. At these high doses you get increased adverse effects like: respiratory depression. Short acting Used in colics because it is short acting and also treats visceral pain well in the horse. If this doesn t improve the horse significantly, it is indicative of a surgical colic. Fe a : given as bolus can stop animal breathing. Hypoventilation. Good way to bring down a tachycardia intra-operatively. This is sometimes used in CRI’s over methadone as the dose range is higher. ACP ▪ Not to be used in cardiovascular compromised patients, cases with blood loss, shock, dehydration or colics. - vasodilation ▪ Long acting sedation → better recovery, as the animal is still slightly sedated during recovery. ▪ In a dog with mitral valve regurgitation, decreased cardiac output caused by bradycardia cannot be increased by increasing stroke volume (i.e. Contractility because this will worsen the regurgitation. A low dose of ACP will cause some vasodilation, leading to decreased systemic vascular resistance → decreased afterload (and therefore increased stroke volume. ▪ Avoid in brachcephalics, boxers(certain English lines, European and American lines haven’t the issue , giant breed dogs, epileptics and stallions ▪ Remember: this has been shown to decrease peri-operative mortality in horses. A ha Ag i ▪ Cause laryngeal collapse, do not use in an upper airway exam. ▪ Cause a horse to urinate loads under GA, this is why you note how much urine is in the horse’s catheter bag during surgery. Nb to replace fluids lost. ▪ Colic: don t use romifidine because it covers up the pain for too long, use xylazine instead. ▪ Don’t use atropine after medetomidine (vasoconstriction bradycardia because heart will be pumping against constricted vessels which could lead to arrhythmias ▪ Only licensed sedatives in farm animals, specifically xylazine and detomidine in cattle (ACP and Diazepam are not allowed to be given to food producing animals. ▪ Although licenced, they are very dangerous in sheep and goats. They cause massive  vasoconstriction and bronchoconstriction, leading to pulmonary oedema. Ke a i e A direct negative ionotrope but stimulates the CNS → increased sympathetic nervous system tone therefore cardiac effects mirror sympathetic nervous system outflow. (increased BP, increased HR, increased C/O. In very sick animals these sympathetic effects may not be see as catacholamines could be depleted. Often Used as a CRI in spinal surgeries in UCDVH, good to put in a plan for a spinal surgery. P f Induction and CRI NO analgesia Hypotension from vasodilation and decrease heart contractility – NO compensation (resets baroreceptors mg/kg (alfaxalone mg/kg both come in mg/ml concentration. Highly protein bound – NB in hypoprotonemic patients - need to decrease dose because more free active drug in circulation. Draw up mg/kg, give half over - seconds to effect. If need more give mg/kg. Propofol twitches. Post induction apnea and vasodilation/hypotension worse if inject to fast IV Good in a bitch having a caesarian, as the effects are short lasting so pups won’t be sedated when they are extracted. A fa a e ▪ Poor analgesia ▪ Onset min, duration ten minutes ▪ Fewer CVS effects than propofol ▪ Expensive D i gI d c i while induction agents are being administered, you must go through your “A,B,C”: Airway- intubate the patient and inflate cuff, make sure there is no leak, ensure ET tubes have been leak tested prior to intubation Breathing – is there apnoea or not? Look at animal, reservoir bag and capnography. Circulation- while induction agent is being administered, have your finger on the femoral pulse, making sure it is still present. Next step- “begin monitoring” You will be asked to verbalise all these points  An icholinergic An im carinic Dr g A i e A i e ha e, ml vials, g/ml D e - g/kg IV, IM or SC Ac in - min after IV administration and lasts up to min Effec Prevents or treats bradycardia (it increases heart rate , reduces saliva and bronchial secretion, dilates pupil. Small IV doses may produce transient bradycardia due to a weak peripheral muscarinic agonist effect. Increases anatomical dead space in lungs by causing bronchodilation. U e Canine sick sinus syndrome; sinus bradycardia; to prevent or treat vagal bradycardia (from high dose morphine, fentanyl ; in reversal of N.M.B. to prevent muscarinic effects of anticholinesterases (e.g. neostigmine ; as an antisialagogue in pigs; to treat organophosphate toxicity. Gl cop rrola e R bi ml vials,. mg/ml D e. mg/kg IV Ac Slower onset than atropine. Longer duration of action. Effec Does not cross the BBB, so no central or ophthalmic effects are seen (mydriasis, delayed awakening from GA U e As atropine ADVANTAGES DISADVANTAGES Reduce saliva G A Increase arrhythmias (tachycardia and increased Bronchodilation myocardial oxygen demand Prevent or treat vagal Increase metabolic rate and VO bradycardia Makes saliva more viscid and likely to block small Increase gastric pH G A airways Rapid onset of action A G Increases anatomical dead space Do not use: pre-existing tachycardia, glaucoma, giant breeds of dog, horses (vision disturbances, ileus, alveolar collapse or cattle (viscid saliva Sig ha a h e i igh de GA Rapid nystagmus (except ketamine, nystagmus will remain even if horse is at the appropriate depth Lacrimation Increased BP Increased muscle tone at the neck and withers ( Claire says you can check the muscle tone of the jaw, Jo says you cannot. Give the appropriate answer for whoever is asking. A sluggish palpebral is normal in the horse, as the horse is generally maintained at a slightly lighter plane of anaesthesia. MAP above mmHg to prevent myopathy. Myopathy is more of a concern in draught horses. Lactate  should be less than. When recovering a horse that has had an op on one of the limbs, recover with the sore leg uppermost. Sig fd g igh de GA Jaw tone increased HR and RR rapidly increase Palpebral response Level of iso being exhaled can be measured in UCD If a dog moves during surgery, you give them a top up of induction agent first, then turn up gas. Turning up gas on its own takes too long. Sig fb i e igh de GA Muscle tone, as per the horse Eyes: Eye reflexes disappear early in a bovine. At proper anaesthetic depth, the eyes rotate ventrally and there is negative palpebral. Because these are the first to go at induction, if a bovine shows these reflexes in surgery, it means they are very close to waking up. This is a good time to panic. F id - times maintenance – - ml/kg/hr Awake –. ml/kg/hr, Asleep – ml/kg/hr Gelofusine – succinylated gelatin in NaCl solution, colloid , half life - hours, volume expansion - hours A e he ic ga e Positive pressure ventilation decreases venous return and blood pressure. In normal breathing inhalation occurs my negative pressure in the thorax, this allows blood to flow through the vena cava and back into the heart. With IPPV there is positive pressure in the thorax at the time of inspiration, this occludes the vena cava venous return decreased preload decreased stroke volume decreased C/O Ni ide Concentrating/second gas effect at start of anesthesia, must keep fresh gas oxygen above. Diffusion hypoxia at the end of anesthesia (keep O flow for - min after turning off anesthetic agent. Collects in gas filled cavities so  avoid in GDV, ileus, pneumothorax Ve i a i Barotrauma Volotrauma Tidal vol – - ml/kg, usually operate at the lower end of this scale. Peak inspiratory pressure (PIP - cmH O, never above. If an animal is having a thoracotomy or it is a horse where V/Q mismatch is likely, they may set a Peak End Expiratory Pressure (PEEP , this will stop atelectasis of the lungs at the end of expiration. It is usually c. cmH O If hypercarbia occurs, you will be asked what to do: you say you need to increase ventilation: either tidal volume, or resp rate usually. Most of the machines in UCDVH are pressure controlled, if you increase the PIP by cmH O you will increase tidal volume. Can increase RR at the same time. Lea e achi e o Occlude end of breathing tube at patient end o Close APL valve o Press O flush to until reach - units on gauge or until al creases gone from the bag (if gauge not present/broke o Watch gauge/bag for sec to see any drop in pressure o Open APL and sqeeze bag and watch one way valve leaflets to see if working. Non rebreathing systems All non re-breathing systems are designed so that alveolar gas should not be re-breathed. Thus, they require specific gas flows. These systems are more expensive to run and result in considerable atmospheric pollution. As the Bain, Magill and Lack have expiratory valves they are not suitable for patients under kg. The Ayre’s T-Piece has no valves. The advantages of non re-breathing systems include: ▪ The patient receives f e h ga a each b ea h – thus they receive altered vapouriser settings immediately. ▪ There is no need to alter the fresh gas flow during the course of anaesthesia ▪ nitrous oxide may be used safely ▪ The Ayre’s T Piece i i ab e f a a ie g ▪ The Ayre’s T-Piece and the Bain may the used for IPPV at lower gas flows(decrease FGF in IPPV because you can control the respiratory rate and the length of the expiratory pause –NB , however the Magill and the Lack require very high flows if used for IPPV ▪ During spontaneous ventilation the Magill and the Lack require a lower gas flow as they allow some re-breathing of anatomical dead space gas. ▪ Mini lack not efficient for IPPV (to high a FGF, lose rebreathing benefit – v efficient for spontaneous breathing as it recycles anatomical dead space gas (approx. third tidal vol this is great – same as fresh gas, as gas exchange does not occur in the anatomical dead space but it is warm and moist ▪ Bain – works just like T – piece just coaxial set up. - kg animal up as kg animals cant exhale properly with FGF directly flowing towards there mouth. Leak testing bain must test both tubes independently as leak in inner FG tube causes rebreathing CO. Very  efficient during IPPV but requires a high fresh gas flow in animal is breathing spontaneously. Cannot be used in large dogs at it requires a flow of oxygen so high that the oxygen machines cannot keep up. ▪ Humphreys breathing system combines a mini lack and a T piece so you can use T piece for IPPV and lack on spontaneous breathing – better efficiency. F e h ga f e i ed b e b ea hi g e d i g a e b ea hi g I i Nece a ea he e fig e f he e a Ayre’s T-piece Minute Volume x. - approx: ml/kg/min Bain Minute Volume x. to approx: - ml/kg/min Magill and Lack Minute Volume x. - approx: - ml/kg/min Reservoir bags – - X tidal volume, better overestimate than under estimate Circle breathing system (rebreathing/low flow anesthesia o In large dog best because saves on oxygen and anesthetic because non-rebreathing would waste too much. o Denitrification prior to maintenance of anesthesia – As the dog is full of atmospheric air ( Nitrogen at this point, the nitrogen needs to be cleared from the system, otherwise it dilutes the oxygen and iso in the blood. If there is nitrogen in the blood still, it will take forever for desired concentrations of blood iso to be reached, i.e. “the time constant is increased” ( that is another way of saying that there will be a delay in increasing or decreasing anaesthetic depth from the time the vapouriser setting was changed. Start anesthesia with ml/kg O to remove nitrogen for - minutes then drop to - ml/kg of oxygen o Soda lime reacts with CO – produces water and heat (exothermic RXN. This reaction needs water to occur. Soda lime must never get dehydrated. o Dehydrated soda lime (forget to turn off oxygen flow for weekend dehydrated soda lime then reacts with halogenated gas anesthetics creating carbon monoxide – will kill first patient Monday morning. Will have no decrease in SPO or change in CRT – looks perfect then just dies. o For animals over kg, unless IPPV is being used. This is because the inspiratory and expiratory valves, along with the soda lime lead to increased resistance that a small animal cannot overcome without the aid of a ventilator. o Oxygen flow only needed to replace O used in metabolism – g h for first few minutes then g h o Keeps the animal warmer, as they are breathing is air that is warmed and moistened. A lot to be said in the anesthesia world for warmed, moist gas. A big dog can even get hyperthermia from a circle set up. o Apparatus dead space is defined as any area in the equipment where inspiratory and expiratory gases meet. Using this definition, the Y-piece is the only apparatus dead space in the circle breathing system. Contrast used in CT - used to show increased blood flow to a tissue e.g. tumour, inflamed tissue. Done by CT scan first without contrast, then IV contrast and compare on screen from vessels increased in size.  Ca e ha eed ecia a e i Ne a e- hypothermia and hypoglycemia. Also more fluid so drugs have a higher volume of distribution T B eed - Hypothermia and hypoglycaemia (especially prevalent in Yorkshire Terriers. A more accurate way of dosing would be by surface area. E i e ic – avoid ACP, as it lowers seizure threshold. B achce ha ic – avoid ACP - Excess sedation in brachycephalic dogs – can get airway obstruction from relaxation of pharynx Od ca diac a ie – alfaxalone better CVS effects than propofol, less hypotension Ca i h HCM Stroke volume is very small because ventricular lumen is decreased. Do not want a tachycardia as this decreases filling time and cardiac output is decreased even more. Alpha- -agonsists are good due to bradycardic effect. Small dose of ketamine, as it increases heart rate and blood pressure. Ge h d – Lower hepatic enzyme activity so decreased rate of clearing of some drugs. Don’t use thipoentone as it will take the dog forever to wake up. He a ic Ca e- Hypoalbuminaemia leads to ascites and increased amount of free drug (active part in the plasma. Need to give colloids and chrsytalloids in order to keep fluid in the vascular compartment, often at less than x maintenance incase the patient gets overloaded, manifests itself as pulmonary oedema. Metabolism of certain drugs (propofol and diazepam most relevant here is slowed down. Head I j – don’t use ketamine it increases intracranial pressure and intraocular pressure. Can use propofol or thiopentone as both decrease ICP Vici D g – Use alpha because of its reliability La E a f D g – avoid alpha (to sedation will relax larynx and look paralyzed Butorphonol(opioid given with low dose acp good – short duration, no effect on larynx C ici g H e – avoid ACP (vasodilation. Short acting alpha best – xylazine and opioid for premed Induction - Ketamine (reduced dose: direct negative inotropic effect, if animal is exhausted and hasbeen colicing for an extended time: catecholamines depleted GGE or diazepam Maintenance – inhalant /- lidocaine CRI Avoid anticholinergics in - Pre-existing tachycardia, Glaucoma, Giant breeds of dog, Horses and cattle, AVOID their use with alpha agonists (increases heart rate, increases intra ocular pressure. Dries up saliva, Atropine in horses causes madriasis – so animal can’t focus- they panic, Also can cause colic in horse due to GI stasis Case example H e ac i e G de Re ie e f TPLO ge b he i e hea h P e ed: ACP would need a high dose to get good enough sedation (high dose plus long action with no reversal agent so not chosen. Medetomidine was chosen because of better sedation with reversal agent available. Methadone with medetomidine because is full mu opioid. (morphine could cause vomiting, pethidine shorter acting but both better sedation Induce: propofol fine just be aware of possible complications (hypotention/bradycardia Maintenance: Iso Analgesia – local nerve block with bupivacaine(long duration- hrs mixed with alpha – dexmedetomidine (vasoconstriction? extends it to - hrs. block femoral and sciatic nerves. Could have done epidural but get decreased sympathetic nerves(vasodilation and get a bit of difficulty with bladder. Don’t urinate properly may need expression/catherisation. Opioid for analgesia aswell B e Xf e GI c e a d bi af e H f ii g P e ed don’t want vomiting so low dose ACP (anti emetic and pethidine (no vomiting side effects, anticholinergic effects, don’t get gastric sphincter contraction for good sedation I d ci really important to intubate ASAP so want fast induction agent – propofol fastest (always beware in sick hypoproteinemic patients GDV – - Decreased tidal vol - Hypoventilation – hypercapnia - Reperfusion toxemia is a concern. Can get pulmonary oedema from the toxemia - V:Q mismatch a concern from compressed lungs. Assess this by comparing alveolar O (get this via calculation with arterial O got from blood gas. A V:Q ratio of means ok, no mismatch. - Want to use drugs with as little CVS affects as possible - Premed – fentanyl, induce with propofol and diazepam. Diazepam no CVS effects and means you can reduce propofol dose (reducing cvs vasodilation - Maintenance – sevo (first case Iv seen it used in Random Bits - Animals don’t feel pain in GIT from cutting/biopsies etc. only pain they feel is distention. Appendices: Normal TPR Values: worth knowing these figures, if you’re asked and you don’t know, you will be subjected to them harping on about their importance. Jo gave us these figures in a tutorial. Dog: - BPM - RR - degrees Celcius Cat: (very relaxed – (stressed BPM - RR -. degrees Celsius Horse: HR - RR - Temp - (fever at. Cows: HR - RR - Temp - Pigs: HR - RR - Temp - – Sheep: HR -  RR - Temp. – Goats: HR - RR -. –  Filling out the Chart: In this example, if you want to write in figures for : , use the column with the blue line, not the red one. Write the figures sideways. Basics of filling in a chart: There is some other stuff but this much will get you by for the first time you have to fill in the chart. You will have to ask the anesthetists how much induction agent (mg they gave the animal, as full dose is not usually required. Fill in what size ET tube was used. If you forget to do this, you can do it at extubation. Start filling in all your parameters when animal has been induced. Using the above picture: if the animal was induced at : , you would start filling your parameters into the column with the blue line going through it, not the first column on the page. “Start of Anaesthesia” – when the animal is induced “Start of Surgery” – when the first incision is made “End of Surgery” – when the last suture is finished “End of Anaesthesia” – When the isoflourane is turned off When a bolus injection is given, it is noted on the left hand side of the chart e.g. “Fentanyl bolus ug I/V” They use a number key system where each note has a corresponding number. This number is then written into the appropriate column for the time it was made. See picture of chart below: the study drug was given at minutes past the hour. Other things that are noted: (this is not an exhaustive list o When the animal was moved to the O.R. o Any change in position during surgery o Any starting or stopping of a CRI during surgery o Any fluid boluses given. Type of fluid and ml/kg o Any important anaesthetic event e.g. “ ml of blood lost”. Use small writing for notes as there is limited space on the chart. If a new CRI is started, in the space for fluids and CRIs(bottom of chart write what the CRI is, what the concentration it is and (ml/h. e.g. Fentanyl CRI ( ug/ml (ml/h. It is the ml/h measurement you take, this is read off the fluid pump being used for the CRI.