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251 Cards in this Set
- Front
- Back
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Why starve pre op? Species specifics?
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Reduce intra abdom pressure --> dogs/cats - 4-6 hours, water removed @ premed horse - 6-12 hours, water removed @ premed cattle - 18-24 hours, water removed 12-18 hours prior to anaesthesia |
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What drug schedules are most relevant to vet med? What are the rules for these?
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S3 - same storage as S2, record purchase but not indiviual use |
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What is the function of the regulator in a anaesthetic machine?
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- reduce pressure of gas coming of out of gas supply - smooth out fluxtuation in gas |
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What is the function of the check valve in a anaesthetic machine?
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- to other cyclinders - to the environment if cyclinder removed |
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What is the function of the pressure gauge in a anaesthetic machine?
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- O2 pressure proportional to contents - nitrous oxide pressure remains constant until cyclinder empty then rapidly falls |
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What indicates that the oxygen has run out in an anaesthesia machine?
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Oxygen failure alarm - alarm sounds when oxygen supply fails |
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When oxygen supply fails when will happen in the anaesthesia machine?
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Nitrous oxide cutoff - prevents admin of hypoxic gas |
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What do some machine have that act when gas supply to patient fails? |
Emergency air intake - allows uptake of room air if gas supply fails |
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What is the function of the flowmetre in a anaesthetic machine? |
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Present in some machines: What is the function of the ratio regulator in a anaesthetic machine?
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prevents admin of hypoxic gas but not allowing ratio of nitrous oxide to oxygen to fall - O2 not allowed at less than 20% |
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What is the function of the vaporiser in a anaesthetic machine?
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Gas picks up anaesthetic agent Uncalibrated - vapour produced varies with temperature and gas flow Calibrated - gas entering vaporiser split into 2 channels --> bypass channel that doesn't contact anestheic --> gas entering chamber above liquid anaesthetic and collecting vapour |
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What connects vaporiser to anaesthetic machine?
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Back bar |
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What allows rotation of the common gas outlet? |
Cardiff swivel |
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What is the function of the oxygen flush in a anaesthetic machine? |
- bypass vaporiser and flowmeter |
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What 2 types of scavenging are available?
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Passive and active |
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How does active scavenging remove the waste gas? |
A air break required to prevent build up of negative pressure to patient |
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How does passive scavenging remove the waste gases? |
-outside of building by tube ( resistance if tube v long) - passed through activated charcoal (nitrous oxide not removed by this) |
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Basic difference between rebreathing and non-rebreathing systems of anaesthetic breathing systems
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Nonrebreathing - fresh gas is provided for each breath, high fresh gas flows MORE CONTROL OVER AMOUNT OF O2/ANAESTHEIC GAS |
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In rebreathing systems why are higher fresh gas flows required at the start of anaesthesia?
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TO MAINTAIN CONC OF ANAESTHETIC AGENT WITHIN THE BREATHING SYSTEM @ start the expired gas of animal has much lower concentration of volatile agent than the inspired gas ( as large amounts of anaesthetic taken up by animal) --> this can dilute the conc. of anaesthetic in the breathing system so higher fresh gas flows required to maintain conc. |
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In rebreathing systems when can the initial high fresh gas flows be reduced?
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Once concentration of volatile anaesthetic in expired breath is similar to inspired breath
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Why is denitrogenation required initially with rebreathing systems?
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How does denitrogenation occur in a rebreathing system?
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- open pressure relief valve --> purge N2 from system |
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Why is nitrous oxide not recommended in rebreathing systems? |
Can use but need HIGH fresh gas flows |
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After initial high FGFs in a rebreathing system the FGFs can be reduced to what?
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OR to meet the minimum requirements of the vaporiser |
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When is a rebreathing system open/closed?
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When O2 delivery exceeds the metabolic O2 req --> open pressure relief valve to allow excess gas to escape --> OPEN SYSTEM |
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What breathing systems are used in rebreathing machines?
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To and Fro |
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What breathing systems are used in non-rebreathing systems?
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- inspiratory limb (Magill, Lack, Parallel Lack) - expiratory limb (T piece, Bain) |
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What is IPPV?
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intermittent positive pressure ventilation- mechanical ventilation in which air is delivered into a person's lungs under pressure and in short bursts, to simulate intakes of breath. |
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What class of drug is acepromazine?
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Phenothiazines |
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Name the 4 drug classes of sedatives/tranquilisers
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Alpha 2 agonists (eg. xylazine) Benzodiazepines (eg. diazepam) |
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Name 2 small animal alpha 2 agonist
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Dexmedetomidine |
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What drug reverses alpha 2 agonist sedation in small animals? |
Atipamazole |
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Name 3 alpha 2 agonist in horses? |
Xylazine Detomidine Romifidine |
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Definie neuroleptic
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drug) tending to reduce nervous tension by depressing nerve functions eg. phenothiazine |
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What four receptor sites are thought to produce anaesthesia?
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- glycine - nicotinic acetylcholine - NMDA |
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What are some advantages of TIVA?
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- minimum equipment - no pollution from gases/inhaled agent - easy to admin - induction rapid and smooth - potentially cheap |
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Injectable anaesthetic agents will induce loss of consciousness is what time measurement?
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ne injection site-brain circulation time |
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What are some disadvantages of injectable agents? |
- patient body mass must be known - high doses when only agent used - self admin inadvertant |
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Once a drug is administered, how does it distribute around the body? How does this affect plasma levels? |
Redistribution --> intermediate vascular group --> rapid decrease in blood and rich tissue [drug] (CESSATION OF CLINICAL SIGNS) Redistribution continues --> poorly perfused tissue eg.fat - can become resevoir |
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Why should propofol be administered slowly?
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dose dependent - CV depression (hypotension, no compensatory tachycardia) - resp depression (bronchodilation, apnoea, cyanosis) |
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Why does propofol rapidly cross the BBB after i/v admin? Where does it act?
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Very lipid soluble GABA agonist |
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Why is there slower recovery from propofol in cats than dogs? |
Metabolised in liver to quinol sulphate and glucuronide conjugates --> cats cant glucuronidate so slower meta, risk of accumulation and toxicity in cats |
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Propofol - clinical signs? |
- good muscle relaxant - induce anaesthesia - anticonvulsant - sedation @ low doses |
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List 4 injectable anaesthetic agents?
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1. propofol 2. alfaxalone 3. ketamine 4. thiopental |
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Where does alfaxalone act? |
Moderate PPB, highly lipid soluble --> rapidly cross BBB |
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In what ways are propofol and alfaxalone similar?
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- I/v in cats and dogs - care in cats as cant glucuronidate - dose dependent CV/resp depression - repeated dose or infusion as rapidly meta - sedative @ low doses |
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In what ways do propofol and alfaxalone differ? |
- A compensatory tachycardia maintained - A not irritant extravascularly |
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When is ketamine use contraindicated? |
- glaucoma or deep corneal ulceration - high sympathetic tone (eg. stress response to injury) - epilepsy - increased intracranial pressure eg. head trauma |
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Ketamine licensed for which species? Routes of admin? |
I/v, I/m, I/p, s/c, across mucous membranes --> acidic so pain when not i/v |
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What kind of anaesthesia does ketamine produce?
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Dissociative - produces unconsciousness but maintains cranial nerve and laryngeal reflexes with increased salivation. Muscle rigidity but spontaneous movements common |
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How does ketamine affect the CV system? |
--> care in patients with cardiomyopathies or high sympathetic tone |
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How does ketamine affect the resp system? |
Transient resp depression - apneustic breathing pattern, bronchodilation, endo tube recommended |
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How does ketamine affect the head physically? |
Increased intracranial pressure, increased intraocular pressure, mydriasis |
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What 2 barbiturates are clinically important? |
Pentobarbital (long acting) (EUTHANASIA ONLY) |
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Barbiturates - what happens if large or repeated doses administered?
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Accumulation occurs when adipose tissue saturated --> redistribution cannot occur and cessation of clinical effect becomes dependent on much slower drug metabolism in liver |
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Thiopental has what effects on the CV/resp systems?
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CV depression - hypotension (due to reduced myocardial contractility and decreased systemic vascular resistance), compensatory tachycardia |
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What barbiturate is only used for euthanasia? |
Pentobarbital |
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What injectable anaesthetic is sometimes used as it produces minimal CV/resp effects and decreases adrenal gland function? |
Etomidate - not licensed in vet med, quality of induction may be poor |
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Injectable anaesthetics can be used to fully maintain (TIVA) or in part (PIVA) maintain anaesthesis. How can this be done? (4)
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- intravenous infusion - combo of injection and inhalation agents - single intramuscular injection |
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Injectable drugs chosen for maintenance of anaesthesia should have what characteristics? eg?
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Alfaxalone and propofol |
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What is the desirable effect of using guiaphenesin? |
- minimal CV side effects - dose dependent respiratory effects |
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What is the drug guiaphenesin used for?
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Central skeletal muscle relaxant - I/v admin |
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Inhalation anaesthetics are split into 2 main groups- what and give examples?
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Compressed gases (N2O, xenon) |
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Give 4 eg of volatile liquids used as inhalation anaesthetics? |
Isoflurane, sevoflurane, halothane, desflurane |
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Give 2 examples of compressed gases used as inhalation anaesthetics? |
Nitrous oxide N2O |
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What do all inhalation anaesthetics have to be administered with?
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A carrier gas eg. oxygen, medical air, helium |
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What ways can inhalation anaesthetics be administered? |
- induction chamber - face mask - nasopharyngeal insufflation - endotracheal tube (oro- or naso-tracheal) |
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What are the disadvantages of using an inhaled anaesthetic agent? |
- cost - equipment needed - pollution (personal/environment) - need to scavenge - toxic compounds |
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What are the advantages of using an inhaled anaesthetic agent? |
- airway protected by endotracheal tube - rapid induction/recovery - rapid change in anaesthetic depth - minimal hepatic metabolism |
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What are some properties of an ideal inhalation anaesthetic agent? |
1. easily vaporised 2. non-flammable or explosive 3. stable in storage 4. no reaction with anaesthetic system components, including soda lime 5. non-irritant or pungent 6. minimally metabolised and/or produces non-toxic metabolites 7. smooth induction and recovery from anaesthesia with rapid control of anaesthetic depth 8. some analgesia and muscle relaxation 9. few cardiovascular and respiratory side effects 10. no renal or hepatic toxicity 11. cheap and not requiring an expensive vaporiser 12. does not cause environmental damage |
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Describe the pharmacokinetics of inhalation agents?
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1. administered and removed from body via lungs 2. from alveoli the agent is absorbed into the blood and then the brain (effect site) 3. pressure gradient from alveoli to brain 4. redistributed into other tissues including fat |
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How does being a very fat soluble inhalation anaesthetic agent affect the animals recovery?
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Fat soluble --> slow recovery from long anaesthesia |
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How does solubility of an inhalation agent affect the speed of anaesthesia onset?
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Less soluble in blood --> faster onset |
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Rate of uptake of inhaled anaesthetic agent depends on?
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–inspired anaesthetic agent concentration –alveolar ventilation rate –uptake by blood and tissues –cardiac output |
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What is a good way of estimating the concentration of anaesthetic agent in the brain? (inhalation)
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the brain concentration approximated alveolar concentration --> can measure alveolar concentration |
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Complete the sentance Speed of induction and recovery is _____ for more soluble inhalated anaesthetic agents |
SLOWER - with soluble agents, a greater amount of inhalation agent has to dissolve into blood before it saturates the blood and can then exert a pressure on the brain |
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How and to what extent are inhalation anaesthetic agents metabolised? List the 4 volatile liquid anaesthetics in order of how metabolised they are
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Only small proportions of inhalation agents metabolised, vast majority being exhaled Degree of metabolism: Halothane 20% --> sevoflurane 2% --> isoflurane 0.2% --> desflurane 0.02 % |
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What is the minimum alveolar concentration?
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the minimum conc. required to prevent movement in response to a painful stimulus in 50% of subjects tested (inhalation agents only, with no premed or analgesia) |
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What affects the MAC of an inhalation anaesthetic agent?
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- hypo/hyperthermia - pregnancy - hypotension < 50mmHg - hyperthyroidism - PaO2 < 40mmHg - PaCO2 >> 90mmHg |
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What doesn't affect the MAC of an inhalation anaesthetic agent?
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1. duration of anaesthesia 2. sex 3. blood pH 4. moderate anaemia 5. PaO2between 40 and 500 mmHg 6. mean arterial pressure>50 mmHg 7. PaCO2between 10 and 90 mmHg |
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What is the primary desirable effect of volatile anaesthetic agents? |
- unconsciousness, amnesia (brain) - immobility (spinal cord) |
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What part of anaesthetic triad do volatile anaesthetic agents NOT PROVIDE?
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--> supplemental analgesia needed if surgery to be performed |
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N2O - how can hypoxaemia occur at the end of anaesthesia using nitrous oxide? How can it be prevented? |
- N2O rapidly diffused out of blood (as insoluble) into air spaces - dilutes the oxygen in the alveoli --> reduce O2 uptake -->> O2 supplementation for 10-15 mins after N20 turned off |
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What is the second gas effect of nitrous oxide during induction of anaesthesia?
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- this relatively increases the alveolar concentration of the remaining gases - increased the gradient between alveoli and blood so increases uptake of volatile agents FASTER ONSET OF ANAESTHESIA |
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List 5 examples of drugs that act as analgesics
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•opioids •non steroidal anti inflammatory drugs (NSAIDS) •local anaesthetics •NMDA antagonists •alpha-2 adrenoceptor agonists |
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What are the receptors for opioids? What do they do?
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•G-protein coupled receptors •inhibit adenylate cyclase (↓ cAMP) •promote opening of potassium channels (decrease neuronal excitability) •inhibit opening of voltage gated calcium channels (reduce NT release) |
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What are the pharmacodynamics of opioids?
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membrane effects •reduced neuronal excitability –due to membrane hyperpolaristion •reduced transmitter release –due to inhibition of calcium entry |
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What are the pharmacological effects of opioids?
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Sedation (and dysphoria) Cough suppression (antitussive) Emetic Reduced GI motility Miosis Histamine release (bronchoconstriction and hypotension) |
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What are the possible side effects of opioids?
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Vomiting Dose dependent resp depression Negative chronotropy Dysphoria |
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Give an example of a full agonist, partial agonist and mixed agonist/antagonist and antagonist opioid drug?
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Partial - buprenorphine Mixed agonist-antagonist - butorphanol Antagonist - naloxone |
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List 4 full Mu agonist opioids
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Methadone, morphine, fentanyl, pethidine |
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Give 2 examples of partial agonist opioids
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Butorphanol |
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Name an antagonist opioid
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Naloxon (antagonise endogenous opioids) |
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How do local anaesthetics act? |
–loss of sensory, motor and autonomic functions –reversed when agent is removed from site of action |
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What are the 2 groups of local anaesthetics?
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Amide linked LAs eg. lidocaine, bupivicaine |
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list some properties of ester linked LAs?
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•poor tissue penetration •short duration of action •allergic reactions |
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How do ester linked LAs result in allergic reactions?
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metabolism of esters produces PABA --> cause allergic reactions |
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List some properties for amide linked LAs?
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- longer duration of action - metabolites excreted in urine - allergic reactions |
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How can amide linked LAs cause allergic reactions?
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allergic reactions –methylparaben used as preservative |
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What physiochemical properties of LAs affect - onset of action - potency - duration of action |
- pKa - PPB |
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How does the environment effect the rate of onset of LAs?
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local anaesthetics are weak bases (pH 8-9) –pKa close to body pH = faster onset –acidic environment = slower onset |
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Why would a vasoconstrictor be administered along with a local anaesthetic?
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–delays onset –prolongs effect –reduces systemic absorption (LA generally cause vasodilation) keeps the LA confined to the area it was administered eg. near nerves requiring the block |
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How are amide linked LAs metabolised and excreted?
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meta by hepatic amidases and the metabolites excreted by kidneys
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How are ester linked LAs metabolised and excreted?
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broken down by plasma esterases to inactive compounds excreted by kidneys
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What is the mechanism of action of local anaesthetics?
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•Na+channel blockade •local anaesthetics bind to sodium channels –resting/inactive state •activation is prevented –no sodium influx –depolarisation prevented •action potential not propagated •no pain experienced |
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How does the LA selectively block fibres?
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Nerve fibres differ in sensitivity to LAs
- myelinated blocked before unmyelinates - Ad fibres before C fibres --> pain blocked before touch sensation |
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When can toxicity be seen with LAs?
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CNS - tremors, convulsions, resp depression CV system - vasodilation, reduced myocardial contractility Allergic reactions, tissue irritants |
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List 4 amide linked local anaesthetics
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Lidocaine Bupivicaine Mepivicaine Proxymetacaine |
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Give an example of an ester linked LA
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Procaine |
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What is an EMLA? Eg |
eg. lidocaine and prilocaine |
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Lidocaine - what prolongs its action? - how does it affect inhaled anaesthetics? - what group of LAs does lidocaine belong to? |
AMIDE LINKED - it lowers the MAC |
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Mepivicaine - what group of LAs? - how does it compare to lidocaine? |
AMIDE LINKED - less vasodilation than lidocaine - less irritant to tissue - equivalent potency - expensive |
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- onset and duration? - toxicity |
- slow onset - long duration ~8 hours - cardiac toxicity |
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- used for? - toxicity - onset and duration |
- rapid onset 10 secs, short duration 10-20 mins - conjunctival sac anaesthesia - toxic to corneal epithelium |
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Which local anaesthetic is used to anaesthetise the conjunctival sac?
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AMIDE LINKED |
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Procaine - what group of LAs? - duration? - admin |
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What LA is added to penicillin to reduce pain on injection?
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Procaine, an ester linked local anaesthetic |
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What LA can be used topically to aid venepuncture? |
EMLA - eutectic mix of local anaesthetic, apply 30-60 mins before |
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Give an example of a non-competitive NMDA antagonist?
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What effect does ketamine have at lower doses?
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Analgesia |
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Where is NMDA receptor? Involved in?
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NMDA receptor –adaptation of CNS to pain stimuli –neuropathic pain –chronic pain |
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Give an example of an opioid like substance which reduces nociceptive transmission? |
Tramadol |
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What is the difference between ester and amide linked local anaesthetics?
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Ester- short acting, poor tissue penetration, rapid meta (not in CSF), allergic reaction from PABA eg. procaine Amide - good tissue penetration, longer acting, allergic reaction from preservatives, risk of toxicity eg. lidocaine, |
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What type of analgesia do local anaesthetics produce?
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True analgesia - prevent nociception and its consequences |
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What are the advantages of local anaesthetics?
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1. only local disturbance of function 2. systemic effects limited 3. inexpensive --> affordable in farm animals |
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What complications can arise from using LAs?
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1. systemic toxicity (calculate doses) 2. neurological injury (needle/mechanical trauma, neuronal ischaemia, infection) |
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What side effects can LAs have?
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1. tissue irritancy (preservatives, volume) 2. vasoconstriction(adrenaline) 3. neuraxial anaesthesia |
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What is neuraxial anaesthesia?
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local anesthetics placed around the nerves of the central nervous system, such as spinal anesthesia (also called subarachnoid anesthesia), and epidural anesthesia. |
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Name the 6 categories of LAs?
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- local infiltration - conduction block - intra-articular - intravenous regional anaesthesia (IVRA) - neuraxial anaesthesia (extradural, intrathecal) |
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When are LAs used on the larynx?
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laryngeal desensitisation performed before tracheal intubation to reduce reflex stimulation and supress laryngeal spasm
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What LA is used to desensitise the cornea?
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TOPICAL USE |
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What LA is used cutaneously as, unlike other LAs, is well absorbed across the skin? |
EMLA - mix of prilocaine and lidocaine |
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List the locations topical LAs can be used?
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- corneal - cutaneous - tracheal - wound margins - intrapleural - urethral - peritoneal |
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Name 2 examples of local infiltration of LAs and how they are used |
Inverted L block - block nerve fibres coursing ventracaudally across left lumbar fossa, laparotomy in cattle |
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What are the advantages and disadvantages of the listed local infiltration techniques?
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Inverted L - avoids tissue distorsion, woun healing not affected, large volumes required |
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What LA can be used to facilitate placing vascular catheters, large spinal needles etc? What type of LA technique is used?
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Mepivicaine used Lidocaine in thicker skinned animals |
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When are intra-articular LAs placed?
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Non irritant LAs used in joint capsule eg. prior to and following joint surgery to attempt antinociception (lidocaine, mepivicaine) |
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What does the method of Intravenous Regional Analgesia involve? IVRA
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- tourniquet applied slowly to limb to block veins first - lidocaine solution inj to vein - analgesia present after 10 mins - surgery - tourniquet released NSAID SHOULD BE ADMINISTERED BEFORE TOURNIQUET |
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What nerves are blocked during dehorning?
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Cornual nerve block - corneal branch of temporal nerve, first and second cervical nerves (cattle) goat - corneal branches of temporal and infratrochlear nerves |
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When are paravertebtral nerve blocks most often used?
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T13, L1 and L2 --> 4th and 5th lumbar nerves produce weakness in hindlimbs so should not be affected |
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During a paravertebral nerve block, what indicates a successful block?
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- heat (affected dermatome warmer, coat stand on end) - no response to pin pricking |
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What are the advantages of a paravertebral nerve block?
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- drug away from wound margins, wont affect healing - provides analgesia of all muscle layers and peritoneum |
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What 2 types of paravertebral nerve block can be used? |
Distal |
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Facial blocks in horses - what 4 nerves can be targeted?
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Supraorbital block (anaesthetise forehead and middle portion of upper eyelid, akinesia of upper eyelid) Infraorbital block (anaesth. upper lip and nostril) Mental block ( anaesth, lower lip) |
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Auriculopalpebral block in horses - results in what?
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No Analgesia |
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Supraorbital block in horses - results in? |
LA at supraorbital foramen - anaesthetise forehead and middle portion of upper eyelid, akinesia of upper eyelid |
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Intraorbital block in horses - results in?
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LA into the formaen - also analgesia of upper incisors and gums |
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mental block in horses results in?
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LA into foramen - also analgesia of lower incisors and gums |
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What block is used to anaesthetise the globe in all species?
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Retrobulbar block |
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List 4 neuraxial anaesthesia uses in Small animals
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Brachial plexus Infraorbital Mandibular (surgery involving ipsilateral mandible and teeth) |
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NEURAXIAL ANAESTHESIA - definition |
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What 2 sites are easiest for extradural anaesthesia?
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Sacrococcygeal site |
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What drugs can be used at a sacral coccygeal extradural anaesthesia? Effects?
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Motor blockage (w/ LAs or alpha 2 agonists) - control of tenesmus |
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What is Fergusons reflex? How can it be abolished?
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Reflex- abdominal wall straining initiated on stretching of birth canal Anaesthesia of tail and perineum |
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When is a lumbosacral extradural anaesthetic used?
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LA - anaesthesia of hind limbs and abdomen Morphine - long acting analgesia without hind limb paralysis |
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What are the risks surround neuraxial anaesthesia? |
Avoid introducing infections! Damage caused to nerves in spinal canal by repeated needle penetration |
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What injectable anaestetic can prevent NMDA receptor activation?
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Ketamine |
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What are the advantages of effective preoperative pain management? |
- reduces risk of personal injury - reduced induction problems - smooths induction in horses |
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Effective intra operative pain management prevents what important 3? |
Reflex movements Nociception (sympathoadrenal outflow) |
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By not preventing nociception during surgery what can the adverse effects be?
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- dysarhythmias hypertension bleeding reduced renal blood flow reduced liver blood flow |
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Pain post op can result in what adverse affects?
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- aggrevated negative energy balance - immunosuprresion - prevents sleep - impairs ventilation |
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Effective postop pain management aids what?
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simplifies general nursing allows repositioning allows wound inspection reduced vocalisation |
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What is sensitisation?
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- central and peripheral components |
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How does peripheral sensitisation occur?
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Arachidonic acid --> COX --> PgG2 and PgH2 Arachidonic acid --> Lipoxygenase --> leukotrienes and lipoxins --> FORM SENSITISATION SOUP which increases sensitivity of peripheral nociceptos |
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What acts on arachidonic acid to cause peripheral sensitisation? |
AA --> COX --> PgH2 and PgG2 |
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What do leukotrienes and lipoxins do? |
Vascular permeability Leukocyte invocation effects --> add to sensitisation soup |
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What is in the sensitizing soup to cause peripheral sensitisation?
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leukotrienes, thromboxanes, prostaglandins, COX, serotonin, substance P, bradykinin |
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Central sensitisation - pain impulses arriving in dorsal horn initiate what changes in grey matter?
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- gene expression - axonal sprouting - NMDA receptor proliferation |
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Central sensitisation - how is post op pain enhanced in sensitisation?
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- hyperalgesia - allodynia - neuropathic pain |
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How does GA affect sensitisation and post op pain? |
GA DOES NOT PREVENT SENSITISATION OR SUPRESS POST OP PAIN
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What 4 clinical strategies can optimise a patients perioperative comfort?
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- pre emptive analgesia - polymodal pain therapy - partial intravenous anaesthesia - prolonged post operative pain therapy |
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4Ps - what is the first P?
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- analgesics before surgery - antiinflam drug pre op prevent sensitizing soup forming - LAs between surgery site and neuraxis stop pain impules so inhibits central sensitisation |
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What can block central sensitization? |
Spinal LAs, a2 agonist, some NSAIDs but especially Ketamine |
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What is the second P in the 4Ps? |
- reduced likelihood of adverse effects as lower dose of each drug used |
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Give an example of a polymodal pain therapy? |
C section in standing cow - lidocaine, a2 agonist, flunixin (NSAID) and clenbuterol |
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What is the 3rd P in the 4Ps?
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--> infusing drugs like ketamine during anaesthesia - reduced physiological depression caused by inhaled anaesthetic eg. seroflurane - improves intraop analgesia - central sensitisation is blocked --> uses anaesthetics at minimal doses to produce anaesthesia |
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What is the 4th P?
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- post op anti inflame drugs should be maintained until wound is almost healed |
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Define hypovolaemia? What can cause it?
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- haemorrhage - fluid loss eg. V and D - loss of plasma volume eg. internal - exudate |
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What can result in hypoperfusion?
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- hypovolaemia - reduced CO - blood maldistribution |
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Define dehydration?
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Reduction in water content of the body --> can lead to hypovolaemia and hypoperfusion |
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3 ways to assess dehydration |
- mucous membranes moistness - retraction of globe |
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How can hypovolaemia be assessed? |
- CRT - pulse quality - HR and BP |
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What additional tests can differentiate hypovolaemia from other causes of hypoperfusion?
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- packed cell volume - body weight - urea - electrolytes (inc if pure water deficit) - central venous pressure |
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What are the 4 aims of fluid administration? |
1. Restore circulating blood volume 2. Replace pre-existing losses 3. Supply normal maintenance requirements 4. Allow for any ongoing abnormal losses |
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What are the signs a patient has been given a fluid overload?
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oedema vomiting ascites increased resp rate nasal discharge increased urine output chemosis (eye irritation) |
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What are the signs a patient has a fluid depletion?
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pale, dry mucous membranes slow CRT poor skin elasticity cool extremities sunken eyes reduced urine output |
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What are the 3 types of fluid? |
Crystalloids Blood products |
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What are crystalloids? |
Used for short term intravascular volume expansion and replacement of interstital deficits Can be hyper- hypo or isotonic |
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What 2 solution types of crystalloids are available? What is the difference between them?
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Maintenance fluids Maintenance fluids have lower sodium load , addition of glucose or dextrose |
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Replacement solutions - composition - given when? |
- given in large volumes I/v - use when mixed electrolyte and water loss situations eg. V, D, polyuria, haemorrhage |
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List 2 examples of maintenance fluids and a use for each |
0.18% saline and 4% glucose - mainly H2O with small amounts of Na and Cl Both used to treat free water losses eg. dog trapped in hot car |
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If the maintencance fluid 0.18% saline and 4% glucose is used what else is required?
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If used for maintenance potassium is required |
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What replacement solution will increase intravascular volume for a short time? |
Short acting and must be followed with isotonic fluids to replace fluid drawn from interstitium |
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Replacement solutions - 0.9% saline features, treats what? |
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What commonly used replacement solution is indicated in electrolyte loss but must be used carefully in liver disease and cerebral oedema?
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- isotonic replacement, similar electrolyte comp to plasma, contains Na, Cl, K, Ca and lactate Care in liver disease as may not metabolise lactate effectively |
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Hartmanns solution commonly used when?
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Electrolyte loss, diabetic ketoacidosis, renal failure |
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What is the name of the replacement solution similar to Hartmanns but without lactate?
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Ringers - indicated for replacement of fluids and electrolytes, prepyloric vomiting, liver disease |
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When should using hypertonic saline be avoided? |
Dehydration, hypernatraemic, volume overload, uncontrolled haemorrhage |
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What are the uses of colloids?
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- volume expansion of the intravascular space in hypovolaemia - oncotic support in patients with hypoalbuminaemia |
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What are colloids? What do they do?
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Colloids contain large macromolecules which retain fluid within vascular space by increasing oncotic pressure, retained in the circ longer than cyrstalloids Natural colloids eg. albumin or synthetic |
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When should colloid use be avoided?
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When there are leaky capillaries |
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What effects the length of effect the colloids will have? |
Size of molecule - larger the molecule the longer it stays in the circulation |
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What are the risks of using colloids? |
Interfer with coagulation Overinfusion |
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What types of colloid are available? |
Hydroxyethylstarches (Oxyglobin- natural derived from bovine Hb, considered blood product) |
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Describe the features of gelatin based colloid and when it will be used
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- rapid effect - minimal clotting effect - used during anaesthesia |
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Describe the features of hydroxyethylstarches (colloid) and when it will be used
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- molecule weight varies with starch used eg. hetastarch larger than penta |
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What are the vit K dependent factors? |
II, VII,IX, X |
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List the 6 blood products that are used in fluid therapy
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- packed RBCs - cryoprecipitate - fresh frozen plasma - frozen plasma - oxyglobin |
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Blood products in fluid therapy- whole blood contains what? Used when? |
- use in acute blood lose |
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Blood products in fluid therapy- packed red blood cells collected how? What is required before PRBCs can be administered? |
- needs to be resuspended in 0.9% saline (avoid Hartmanns/Ringers) |
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Blood products in fluid therapy- when are packed red blood cells administered? |
- whole blood loss |
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Blood products in fluid therapy- what does fresh frozen plasma contain? When is it frozen? |
- must be frozen within 6 hours of collection |
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Blood products in fluid therapy- when is fresh frozen plasma uused? |
- animals w/ prolonged clotting times having surgery - immunoglobulin deficiencies |
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- doesn't contain factors V, VIII and von Willebrands factor or plamsa proteins |
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Blood products in fluid therapy - when is frozen plasma used? |
anticoagulant forms of rodenticide toxicity |
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contains - 20% fibrinogen, 50% factor VII, 30% factors VIII, XIII and vWF |
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When is cryoprecipitate used?
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eg. von Willebrands disease |
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When is oxyglobin used? |
To increase oxygen carrying capacity in anaemic animals |
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What 2 things can be given as fluid supplements? |
Sodium bicarbonate |
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Potassium chloride can be given during hypokalaemia. What can cause hypokalaemia?
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- renal failure promotes K loss |
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When can sodium bicarb be given with fluids? What is necessary before giving NaCO3?
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Respiratory function must be adequate to blow off CO2 |
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What replacement solutions are not appropriate to give with sodium chloride?
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Hartmanns Ringers |
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List the 5 routes of fluid admin? |
- subcut - intraperitoneal - intraosseus - intravenous |
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What can limit absorption of fluids administered via subcutaneous route?
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Only isotonic solutions |
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What routes of admin of fluids are only possible with isotonic fluids? |
Intraperitoneal |
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What is the rate of maintenance fluids? |
eg. 22kg dog = 2ml x 22 = 44ml /hour =44/60 to get ml/minute |
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For a standard giving set what is the drops per ml?
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20 drops per ml
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Intraoperative blood loss - what fluids should be given with up to 10% blood loss? 10-20%? 20% +? |
10 to 20% - colloids over 20% - product with oxygen carrying capacity |
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Ventilation definition? requires what 3? |
Bulk flow of gas into and from the alveolar space - patent airway - effective resp muscle activity - responsive neural control |
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How do we maintain the patent airway during anaesthesia?
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endotracheal intubation |
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What are the advantages of using a cuffed endotracheal tube?
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1. protect airway from foreign material 2. Permits IPPV 3. Reduces leakage of waste gases |
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What are some disadvantages of using a cuffed endotracheal tube?
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- excessive Vd - airway resistance increased if small diameter - ischaemic tracheitis can occur if cuff pressure high - upper airway functions bypassed - endocronchial intubation may occur with increasing V/Q inequalitites |
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Give a physiological difficulty with intubation
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Cats and pigs retain active laryngeal reflexes under deep anaesthesia |
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What is PaCO2? |
Partial pressure of CO2 in the artery |
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What is VA? Equation? |
VA= (Vt-Vd) R R- resp rate |
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What is the equation to determine PaCO2? |
VCO2 - vol of CO2 produced by body per unit time FiCO2 - conc of inspired CO2 |
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What can cause a reduction in VA? |
decreased Vt (anaesthetics, dec. thoracic compliance, thoracic pain) increased Vd (anaesthetics, mechanical Vd, hypovolaemia) |
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What can cause an increase in VCO2?
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Increased by surgical stimulation, pyrexia, malignant hyperthermia |
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What can cause an increase in FiCO2? |
- increased in rebreathing systems |
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What is DO2? Equation?
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DO2 = Qt x CaO2 Qt = cardiac output CaO2 = oxygen content of blood |
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Define spontaneous ventilation?
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- anaesthetist exerts no control over resp rate, tidal volume or pattern |
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Define controlled ventilation?
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- Resp rate and Vt are determined by anaesthetist - ventilation controlled manual comperssions of rebreathing bag (manual ventilation) - ventilation controlled by mechanical ventilator (mechanical ventilation) |
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Define 'sighing' an animal?
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periodic delivery of an abnormally large tidal volume to reexpand atalectic regions of lung |
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Advantages and disadvantages of spontaneous ventilation? |
+ alterations inresp pattern and rate give useful info on depth of anaesthesia + beneficial effects on CV function - hypoventilation and hypercapnia inevitable - energy for breathing supplied by animal |
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Advantages and disadvantages of intermittent positive pressure ventilation?
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+ fixed volume of anaesthetic gas reaches lungs so stable anaesthesia level + rhythmic breathing pattern sometimes required for delicate ops - Mechanical ventilators complex - Mechanical ventilators costly - May reduce cardiac output - Lung damage (pre-existing disease) - V/Q discrepancies - Respiratory alkalosis/Hypothermia |
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What are the requirements of IPPV?
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1. Cuffed endotracheal tube (uncuffedtubes cats) 2. Suitable anaesthetic breathing system 3. Means of lung inflation (mechanical or manual) 4. Method of suppressing ventilation |
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During IPPV, how can ventilation of animal be suppressed so R and Vt are determined by anaesthetist?
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-Rhythmic lung inflation -Modest hypocapnia -Anaesthetics -Potent opiods -Neuromuscular blocking agents |
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What usually is enough to suppress spontaneous efforts to breath during IPPV?
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--> if not enough NMB, potent opioids and deeper levels of anaesthesia can be administered |
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When is it essential that IPPV is used?
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or diaphragmatic hernia |
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How does spontaneous ventilation enhance cardiac output?
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--> pressure gradient created from abdomen and head to right heart which facilitates venous return in cr/caud vena cava --> ENHANCED CO |
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