Podcast
Questions and Answers
What does the 'D' in the lesion definition stand for?
What does the 'D' in the lesion definition stand for?
Which of the following factors is NOT included in the problem classification of lesions?
Which of the following factors is NOT included in the problem classification of lesions?
What should be used alongside Type 1 clinical reasoning as mentioned in the conclusion?
What should be used alongside Type 1 clinical reasoning as mentioned in the conclusion?
Which aspect of clinical reasoning is emphasized as taking time?
Which aspect of clinical reasoning is emphasized as taking time?
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What is the primary focus of the differential list example provided?
What is the primary focus of the differential list example provided?
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What characterizes Type 1 clinical reasoning?
What characterizes Type 1 clinical reasoning?
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In which scenario is Type 2 clinical reasoning most beneficial?
In which scenario is Type 2 clinical reasoning most beneficial?
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What is a potential drawback of Type 1 clinical reasoning?
What is a potential drawback of Type 1 clinical reasoning?
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Which of the following descriptions applies to Type 2 reasoning?
Which of the following descriptions applies to Type 2 reasoning?
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What is the primary goal during the recovery phase after anesthesia?
What is the primary goal during the recovery phase after anesthesia?
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What does Type 1 clinical reasoning rely heavily on?
What does Type 1 clinical reasoning rely heavily on?
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Which factor is NOT a common cause of recovery delay after anesthesia?
Which factor is NOT a common cause of recovery delay after anesthesia?
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What should be done if a patient exhibits signs of emergence delirium?
What should be done if a patient exhibits signs of emergence delirium?
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Which cognitive load is associated with Type 2 clinical reasoning?
Which cognitive load is associated with Type 2 clinical reasoning?
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Which statement best differentiates Type 1 and Type 2 reasoning?
Which statement best differentiates Type 1 and Type 2 reasoning?
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Which drug is NOT typically used in the maintenance of anesthesia?
Which drug is NOT typically used in the maintenance of anesthesia?
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What is the primary goal of Type 2 clinical reasoning?
What is the primary goal of Type 2 clinical reasoning?
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What characterizes the state of emergence delirium in a recovering patient?
What characterizes the state of emergence delirium in a recovering patient?
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During extubation, which action is considered crucial for monitoring the patient?
During extubation, which action is considered crucial for monitoring the patient?
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Which step is NOT generally part of the recovery checklist after anesthesia?
Which step is NOT generally part of the recovery checklist after anesthesia?
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What does pharmacodynamics primarily study?
What does pharmacodynamics primarily study?
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What characterizes Type A adverse drug reactions?
What characterizes Type A adverse drug reactions?
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How is the minimum effective concentration (MEC) defined?
How is the minimum effective concentration (MEC) defined?
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If a drug is below the therapeutic range, what is likely to occur?
If a drug is below the therapeutic range, what is likely to occur?
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What distinguishes Type B adverse drug reactions from Type A?
What distinguishes Type B adverse drug reactions from Type A?
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What is indicated by the therapeutic range of a drug?
What is indicated by the therapeutic range of a drug?
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Which of the following best describes a Type A adverse drug reaction?
Which of the following best describes a Type A adverse drug reaction?
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In the context of pharmacology, what does suboptimal effect mean?
In the context of pharmacology, what does suboptimal effect mean?
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Why is it important to understand the therapeutic range of a drug?
Why is it important to understand the therapeutic range of a drug?
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What is the primary characteristic of general anaesthesia?
What is the primary characteristic of general anaesthesia?
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Which of the following is NOT a component of the ideal anaesthetic agent?
Which of the following is NOT a component of the ideal anaesthetic agent?
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What does the term analgesia refer to in the context of anaesthesia?
What does the term analgesia refer to in the context of anaesthesia?
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Which fraction of general anaesthesia does 'balanced anaesthesia' primarily address?
Which fraction of general anaesthesia does 'balanced anaesthesia' primarily address?
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How is nociception defined under general anaesthesia?
How is nociception defined under general anaesthesia?
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Which of the following represents regional anaesthesia?
Which of the following represents regional anaesthesia?
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Which is a crucial aspect of monitoring in veterinary anaesthesia?
Which is a crucial aspect of monitoring in veterinary anaesthesia?
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What is the role of premedication in anaesthesia?
What is the role of premedication in anaesthesia?
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Which of the following is a common complication during veterinary anaesthesia?
Which of the following is a common complication during veterinary anaesthesia?
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How does nitrous oxide facilitate the induction of a second gas during anesthesia?
How does nitrous oxide facilitate the induction of a second gas during anesthesia?
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What is the primary effect of diffusion hypoxia upon the discontinuation of nitrous oxide?
What is the primary effect of diffusion hypoxia upon the discontinuation of nitrous oxide?
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What immediate action should be taken to counteract diffusion hypoxia during recovery?
What immediate action should be taken to counteract diffusion hypoxia during recovery?
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What are common sources of leakage that can cause exposure to nitrous oxide?
What are common sources of leakage that can cause exposure to nitrous oxide?
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What short-term effects can chronic exposure to nitrous oxide induce?
What short-term effects can chronic exposure to nitrous oxide induce?
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Which mitigation strategy is effective in managing nitrous oxide exposure?
Which mitigation strategy is effective in managing nitrous oxide exposure?
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Among the anesthetics mentioned, which one has the highest Global Warming Potential Index?
Among the anesthetics mentioned, which one has the highest Global Warming Potential Index?
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Which anesthetic is associated with ozone layer destruction as indicated in the content?
Which anesthetic is associated with ozone layer destruction as indicated in the content?
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Study Notes
Clinical Reasoning
- Clinical reasoning is the process by which veterinary surgeons integrate a multitude of clinical and contextual factors to make decisions about the diagnoses, treatment options, and prognoses of their patients.
- Learning objectives include identifying different forms of clinical reasoning and their applications in veterinary practice, understanding inductive reasoning, and developing a strategy for engaging with practitioners to improve their clinical reasoning.
Learning Objectives
- Identify different forms of clinical reasoning and their application in veterinary contexts.
- Understand and describe the process of inductive reasoning.
- Develop a strategy to engage practitioners in developing their own clinical reasoning.
What is Clinical Reasoning?
- Clinical reasoning is the process by which veterinary surgeons integrate a multitude of clinical and contextual factors to make decisions about the diagnoses, treatment options, and prognoses of their patients.
The Process
- Starts with a presenting case.
- Ends (hopefully) with a successful treatment.
How do we get clinical reasoning skills?
- Difficult to teach (experience is crucial).
- Experience is essential.
- Practicing and gaining experience is vital.
- Guidance is helpful.
- Vets are skilled upon graduation, though practice is required.
Types of Clinical Reasoning
- Type 1 ("Pattern Recognition"):
- Non-analytical
- Fast and cost-effective (if diagnosis is correct).
- Relies on past experience.
- Effective with common disorders
- Weaker in novices.
- Type 2 ("First Principles"):
- Analytical
- Time-consuming and resource-intensive.
- Use when confirming a presumptive diagnosis.
- Involves deductive, inductive, and abductive reasoning.
Type 1 Clinical Reasoning
- Non-analytic
- Rapid and cost-effective (if correct).
- Relies on past experience ("pattern recognition")
- Weaker in novices
- Well-suited for common disorders
- Involves recognizing patterns of clinical signs and illness scripts
Type 2 Clinical Reasoning
- Analytic
- Time-consuming and resource-intensive to investigate
- Used to double-check presumptive diagnoses (based on pattern recognition)
- Includes deductive, inductive, and abductive reasoning
Type 1 vs Type 2 Reasoning example
- Rectal temperature of 40.8°C:
- Type 1: May lead to presumptive diagnosis of bacterial infection
- Type 2: Might investigate further for other potential causes (viral, autoimmune, neoplastic)
Inductive Reasoning
- Broad generalizations
- Tentative hypotheses
- Exploratory
- Seeks appropriate information
- Structured approach
Key Questions
- What is the problem? Define and refine the problem.
- Which system is involved, and how is it involved? Define and refine the system.
- Where within the system is the problem located? Define the location.
- What is the lesion? Define the lesion.
The Minimum Database
- Essential initial tests often include haematology, serum biochemistry, and urinalysis.
- Critical thinking and careful analysis are necessary.
- Avoid "fishing" for answers without a clear reason.
Problem List
- Create a problem list to clarify clinical issues and avoid critical signs being missed.
Define and Refine the Problem
- What's the actual problem? Examples: Vomiting, fits, red urine.
- Owner vs. Veterinarian Perceptions: Differences in understandings of the issue.
Define and Refine the System
- What systems are causing relevant clinical signs? Identify the issues causing the sign(s)
- Primary problem (structural)
- Secondary problem (functional)
- Why does this matter?
- Diagnoses, diagnostic tools, treatment considerations may differ.
- Consideration of Local vs Systemic factors
Define the Location (Within the System)
- Where, within the system, is the problem located?
- Examples: Vomiting (upper or lower GIT).
- Relevance of Endoscopy.
Define the Lesion
- Identify the nature of the underlying problem (e.g., vascular, inflammatory, anomaly, infection, metabolic, neoplastic, or degenerative).
Example of Differentials List
- Possible causes of issues like gastric lesions, spinal cord lesions, or hematuria.
Conclusion
- Use both Type 1 and Type 2 clinical reasoning skills.
- Pattern recognition is valuable, but critical thinking is important.
- Learning takes time and practice.
Inhalational Agents
- Gaseous and volatile agents have different practical administration methods.
- Important pharmacokinetic terms (saturated vapour pressure, minimum alveolar concentration, blood gas partition coefficient, and second gas effect) are defined and explained.
- The speed of uptake and elimination is affected by several factors which are clinically relevant.
- Agents in use in contemporary veterinary practice, and associated safety considerations for use of inhalational agents (including scavenging), are described.
Inhalational Anaesthetic Agents
- Volatile anaesthetic drugs are administered by inhalation.
- Vapours or gases, for example: Isoflurane, Sevoflurane, and Desflurane
- Gases: for example Nitrous Oxide
- Indications: induction and maintenance of anaesthesia.
Inhalational Agents' Properties
- Saturated Vapor Pressure (SVP): pressure exerted by vapour on surroundings in closed container at equilibrium at a certain temperature.
- Solubility: Measured as a partition coefficient, a capacity of a solvent to dissolve anaesthetic gas, relative to the gas phase, at equilibrium.
- Blood/Gas Partition Coefficient: High= more drug dissolved in blood before equilibrium, Intermediate = Isoflurane, Low= N2O, sevoflurane, desflurane.
- Oil/Gas Partition Coefficient: an index of anaesthetic potency.
- Unconsciousness, Hypnosis, Amnesia, and Muscle Relaxation produced. The use of the drug leads to a reversible state of unresponsiveness in the CNS, haemodynamic and endocrine responses to noxious stimuli.
- Mechanism of action: Multiple theories for the mechanism of action for inhalational agents exist which are not fully understood, for example, protein. and lipid theory.
Minimum Alveolar Concentration (MAC)
- Minimum alveolar concentration (MAC) is the minimum alveolar concentration of an anaesthetic agent at which 50% of patients fail to respond. Often expressed as a percentage
- Isoflurane is more potent than sevoflurane, as a lower MAC is required.
- MAC values for different species vary.
- 1.3 X MAC prevents movement in 95% of animals, 1.5 X MAC surgical anesthesia, but there can be side effects, 1X MAC or less is usually used.
- Balanced anesthesia can be used which decreases the MAC required
- Factors influencing MAC: species, age (e.g., neonates and geriatric patients), concurrent CNS depressant drugs, severe hypoxaemia and hypercapnia, hypothermia, hypotension, and haemorrhage.
MAC in different species
- Provides values for different species such as dog, cat, horse, cow, sheep, goat, pig, chicken, rabbit, ferret, and rat for Isoflurane, Sevoflurane, Desflurane, & N2O
Effect of Different Factors on MAC
- Factors influencing MAC include species, age, concurrent CNS depressant drugs, hypoxaemia, hypercapnia, hypothermia, hypotension, and haemorrhage.
Vaporiser
- Vaporisers convert from liquid anaesthetic into its vapour form
- Allows controlled amount of the vapour to fresh gas flow
- Controls the concentration of the anaesthetic
- Annual service is essential
End Tidal Concentration of Inhalants
- Shows measurement of end tidal concentration.
- This is an example of how inhalant concentrations are monitored in practice
Pharmacokinetics (Uptake)
- Inhalational agents move down a pressure gradient (high to low) until equilibrium is reached.
- Depth of anaesthesia depends on the partial pressure of the anaesthetic in the brain (Pbrain).
- Alveolar partial pressure of inhaled anaesthetic agents is important to control.
Pharmacokinetics (Elimination & Recovery)
- Elimination rate depends on Pbrain and the return of consciousness
- Metabolism (primarily in the liver, via cytochrome P450 enzymes) is minimal for modern inhalational agents, although it varies.
- Prolonged general anaesthesia can lead to accumulation of in-halants in fat → slow recovery.
- Potentially lost from breathing circuits or in the patient (open cavities)
- Adsorption or degradation by CO2 absorber
Factors Affecting Uptake & Elimination of Inhalational Agents
- Inhalational agent, vaporization/dial setting, fresh gas flow, volume of breathing system, alveolar ventilation, dead space ventilation, and 2nd gas effect, Blood/tissue solubility, Cardiac Output, and Alveolar- venous blood-tissue partial pressure gradient
Uptake & Elimination
Graphical representations of uptake and elimination processes.
Pharmacodynamic: Cardiovascular System
- Decrease in myocardial contractility
- Peripheral vasodilation
- Attenuation of baroreflex
- Variable effect on heart rate (species & agent dependent)
- Impaired cardiac conduction
- Dose-dependent effects
- Hypotension
- Decrease in cardiac output
Pharmacodynamic: Cerebral
- Reversible, dose-related CNS unresponsiveness to noxious stimulation (general anaesthesia).
- Decrease in cerebral metabolic rate
- Increase in cerebral blood flow (CBF): vasodilation
- Increase in intracranial pressure (ICP)
Pharmacodynamic: Respiratory
- Decrease in alveolar ventilation
- Decrease in response to hypercapnia and hypoxaemia
- Respiratory muscle relaxation
- Dose-dependent increase in respiratory rate (RR) and decrease in tidal volume (TV)
- Airway irritation
- Bronchodilation
- Depression of hypoxic pulmonary vasoconstriction
Pharmacodynamic: Hepatobiliary System
- Decrease in hepatic function
- Hepatocellular injury
- Cytochrome P450 inhibition
- Sevoflurane→ Compound A (hepatotoxic) formed with interaction of CO2 absorbants (minimal level)
Pharmacodynamic: Renal
- Decrease in glomerular filtration rate (GFR) and renal blood flow (CO decrease, hypotension, and splanchnic vasoconstriction)
- Mild, reversible, dose-related
- Nephrotoxicity (Sevoflurane)
- Fluoride metabolites
- Compound A (from degradation by CO2 absorbents)
Pharmacodynamic: Miscellaneous
- Muscles: myorelaxation, malignant hyperthermia (Pigs, humans, horses, dogs).
- Uterus: decrease in contractility and blood flow
- Immune system: depression
- Inhibition of insulin secretion
Nitrous Oxide
- Properties: low potency, rapid onset action, low blood-gas partition coefficient.
- Effect: analgesia, minimal cardiovascular effects, mild myocardial depression, increase in cerebral blood flow and intracranial pressure
- Interference with DNA and myelin synthesis; and has teratogenic effects on bone marrow and neurological systems.
Second Gas Effect
- The acceleration of the increase in the concentration of alveolar anaesthetic agents, for example, nitrous oxide with other agents administered.
- This speeds up the induction of anesthesia.
Diffusion Hypoxia (Third Gas Effect or Fink Effect)
- During recovery, when nitrous oxide is discontinued; the low solubility of nitrous oxide causes a rapid shift from blood to alveoli, resulting in a sudden decrease in the alveolar concentration of nitrous oxide, thus decreasing PaCO2; thereby increasing the respiratory drive and causing hypoxia.
- To treat this, administer 100% oxygen on recovery.
Health & Safety
- Sources of issues: vaporiser filling, leaks (airway, machine, breathing system, ventilator, scavenging devices & connection tubing), patient exhalation.
- Short-term exposure: headache, fatigue, nausea, depression, irritability, chronic exposure → mutagenic, carcinogenic, or teratogenic effects.
- Mitigation: daily leak testing, minimum safe FGF, flush breathing system, avoid facemasks and chamber, ventilation of operating rooms and recovery rooms, key-indexed vaporizer filling systems, and monitoring for trace concentrations, training & education
Injected Anaesthetic Agents
- Describe the various ways in which injectable anaesthetic agents are used in contemporary veterinary anaesthesia.
- Explain the factors affecting the speed of induction.
- Discuss the various techniques for delivering drugs, including intravenous routes in domestic animals.
- Describe the pharmacology of injectable anaesthetic agents, incorporating their physical properties and agent-specific considerations.
- Outline methods of providing muscle relaxation during general anaesthesia.
The Ideal Anaesthetic Agent
- Rapid onset / recovery
- High lipid solubility
- Minimal side effects
- Minimal environmental pollution
- Inexpensive
- Stable in storage and solution
- Non-cumulative
- Good bioavailability by any route of administration
- Provide analgesia and muscle relaxation
Injectable Agents
- Propofol, Alfazalone, Ketamine, and Etomidate are all used for induction and maintenance of anaesthesia.
- Propofol, Alfaxalone, Ketamine, and Etomidate are commonly used drugs for induction and maintenance of anaesthesia.
- Ketamine may be used with Opioid, Alpha-2 adrenoceptor agonist, for co-induction of anaesthesia.
- Venous access is recommended (off the needle injection).
- IM administration in exotics, zoo animals, and small patients is suitable.
Total Intra-Venous Anaesthesia (TIVA)
- Use injectable agents to induce and maintain anaesthesia, including intermittent boluses or constant rate infusion (CRI).
- Adjust infusion rate over time to avoid accumulation and prolonged recoveries.
Total intravenous anesthesia (TIVA) indications
- For patient movement to different rooms/areas
- Field anaesthesia
- Disbudding
- Severe cardiovascular pathologies
- Raised ICP
- Bronchoscopy/thoracotomies
Partial Intra-Venous Anaesthesia (PIVA)
- Co-administration of injectable & inhalational anaesthetics to maintain anaesthesia.
- Examples: ketamine, Alpha-2 adrenoceptor agonists (e.g., fentanyl, remifentanil... ), and lidocaine
- Balanced anaesthesia: decrease in inhalational anaesthetic needs → decreased side effects
- Goal: provide analgesia and muscle relaxation
Rate of Induction
- Dose, speed of injection
- Cardiac output
- Lipid solubility
- Degree of protein binding
- Rate of metabolism& excretion
Induction Agents Pharmacokinetics
- IV administration of a single bolus of agent initially elevates concentration in the blood
- Redistribution is rapid to highly perfused organs (heart, brain, kidneys)
- Redistribution to less perfused tissues (muscle, fat) results in slow release.
- Hepatic metabolism and renal excretion.
Propofol
- Hypnotic alkyl phenol
- Lipid water macroemulsion (e.g., propofol, soybean oil, glycerol, egg lecithin, and sodium hydroxide)
- Licensed in dogs and cats
- Concentration: 1%.
- Induction & maintenance of anaesthesia
- Status epilepticus
- Fish & reptile anaesthesia
- Various formulations exist
Propofol Formulations
- Preservative Free: Support bacterial growth; discard at the end of the day
- Preservative-containing: Use preservative (benzyl alcohol); lasts 28 days; no CRI required (toxicity)
Propofol
- Intravenous administration, occasionally painful.
- High protein binding to albumin and RBCs
- Rapid onset of action (~60-90s), due to high lipid solubility.
- Redistribution to various tissues occurs relatively rapidly.
- Equilibration between CNS & plasma takes ~2 minutes.
- Induction & recovery typically smooth and uncomplicated for most species (exceptions exist, e.g., horses.
- Extrapyramidal signs (propofol twitches, focal or muscle fasciculation, paddling, nystagmus) can sometimes occur.
- Dosing varies for premedicated animals (1-4mg/kg). Always calculate drug dose before administration.
- Consider the use of adjunctive agents that decrease the required dose of propofol (e.g., alpha2 agonists).
Mechanism of Action (Propofol)
- Hypnotic agent enhancing GABA function
- Binds to β subunits of the GABA receptor → GABA dissociation from the receptor → prolonged opening of Cl- channels via hyperpolarisation of post-synaptic neurons
- Inhibition of NMDA receptors
Propofol in cats
- Slower hepatic metabolism (deficiency in glucuronidation enzymes).
- Feline haemoglobin (Hb) is susceptible to oxidative injury with repeated daily administration.
- Minimal clinically significant haematological changes with repeated low-dose propofol administration.
Propofol in cats (Evaluation of Benzyl Alcohol Preservative)
- Propofol emulsion with 2% benzyl alcohol preservative evaluated in cats in phases 1 and 2 for anaesthesia.
- No clinically relevant differences were observed between preservative-containing and preservative-free propofol samples.
Alfazalone
- Synthetic neuroactive steroid
- Insoluble in water (Cyclodextrin)
- Preservatives (last 28 days)
- Licensed for IV administrations for dogs, cats, & rabbits
- Concentration: 10mg/ml
- Induction and maintenance of anaesthesia
- Sedation is not licensed.
- Suitable for immersion anaesthesia in amphibians, reptiles & fish.
Mechanism of Action (Alfaxalone)
- Enhances the inhibitory effect of GABA on the GABAA receptor.
- High doses act as a GABA agonist causing the opening of Cl- channels.
Alfazalone
- IV, IM, and SC administration. Painful sometimes.
- Quick induction after 30-60mins (IV).
- Dose premedicated animal: 1-2 mg/kg.
- IM sedation/anaesthesia (7-10 mins, commonly).
- Alpha 2 agonists, opioids, and midazolam decrease induction dose.
- Smooth induction without excitement.
- Recovery quality similar to propofol.
- Prolonged recoveries if long infusions.
- Possible excitement (paddling, rigidity, vocalization), especially if the drug is used alone.
- Rapid hepatic metabolism.
Alfazalone Pharmacodynamic
- Dose-dependent cardiovascular depression.
- Vasodilation and hypotension.
- Myocardial depression.
- Tachycardia from baroreflex stimulation.
- Decrease in intracranial pressure (ICP).
- Dose-dependent respiratory depression
- Post-induction apnoea
- Myorelaxation in some cases
Ketamine
- Phencyclidine derivative.
- Licensed for, dogs, cats, horses, cattle, sheep, goats, and pigs, plus exotics and wildlife.
- IV, IM, and SC. Painful during intramuscular (IM) injection
- Aqueous solution: Acidic PH.
- 10% solution is most used.
- Induction (+ other agent(s)).
- Analgesia.
- Sedation (for aggressive/painful patients.)
- No reversal.
Ketamine
- Bolus, and CRI administration.
- Induction dose: 0.5-3 mg/kg (IM) for sedation, ~2.5-5 mg/kg (IV) is needed for more extensive procedures in exotics.
- Pain: 10-20mcg/kg/min for intra-operative and 2-5mcg/kg/min for post-operative pain
- Hepatic metabolism (Norketamine as the active metabolite)
- Norketamine and Ketamine (excreted unchanged in urine)
- In dogs and horses, Norketamine is further metabolized into inactive compounds, excreted in urine and bile.
Ketamine Mechanism of Action
- Non-competitive NMDA receptor antagonist.
- Prevents glutamate binding to receptor.
- Effects on neural activity, memory, learning, and processing.
Ketamine Pharmacodynamic
- SNS stimulation
- Increased HR, SVR, and Cardiac output
- Negative inotropic effect
- Minimal respiratory depression
- Apneustic breathing patterns.
- Bronchodilation
- Apnoea post-induction
- Muscle rigidity.
- Muscle tone
- Ocular, laryngeal, pharyngeal, pinnal & pedal reflexes are maintained
- Dissociative state.
- Catalepsy
- Inhibition of thalamocortical pathways
- Stimulation of Limbic and reticular system.
- Analgesia (acute and especially chronic pain)
- Anti-inflammatory actions, ↑ICP
- Cerebroprotective.
- Refractory seizures
Etomidate
- Imidazole derivative
- Not licensed for animals in UK commonly.
- ≠ formulations available.
- Pain on injection (propylene glycol + hyperosmolar to plasma).
- Damage to RBCs (tissue irritation/necrosis with propylene glycol).
- Etomidate-Lipuro(lipid emulsion) is an alternative that doesn't cause pain on injection and does not cause tissue irritation.
- No tissue irritation.
- No pain on injection
- Induction (with premed +/- co-induction)
- 1-3 mg/Kg IV
Etomidate
- Rapid induction and recovery (poor quality).
- Metabolism (hepatic & plasma esterases).
- Inactive metabolites excreted in urine, bile, and feces.
- Low-dose: GABAA enhancer.
- High-dose: GABAA agonist.
Etomidate Pharmacodynamic
- Minimal cardiovascular depression (no significant change in HR, SV, CO, or BP, but is often seen).
- Mild respiratory depression (dose-dependent).
- Adrenocortical suppression due to inhibition of 11β-hydroxylase → cortisol reduction
- No CRI is typically used.
- Poor muscle relaxation (myoclonus/hypertonus).
Co-Induction
- Administration of two or more drugs together for induction/anaesthesia.
- Drug synergism.
- Dose-sparing effect (reduced side effects).
- Cost-sparing.
- Increased cardiovascular stability.
- Helpful properties of the non-induction agents (muscle relaxation, analgesia).
- Examples of co-induction drugs: midazolam, ketamine, lidocaine, and fentanyl.
To Obtain Additional Myorelaxation
- Central muscle relaxation: depress internuncial transmission at the spinal cord and brainstem
- Examples: Guaifenesin (GGE), benzodiazepines
- Peripheral muscle relaxation: neuromuscular junction (acetylcholine receptors)
- Examples: neuromuscular blocking agents (NMDA), depolarising agent(s), non-depolarising agent(s).
Problem Wounds and Drains
- Understanding strategies for dealing with infected wounds.
- Understanding the consequences of improper treatment for infected wounds.
- Managing foreign bodies & internally penetrating wounds
- Distinguishing active and passive drain types
- Identifying scenarios needing surgical drainage
- Describing chest and abdominal wound drainage methods
Factors Affecting Wound Healing
- Patient: poor nutrition/malnutrition, concurrent diseases, immunosuppressive drugs/chemotherapy, cat vs. dog, wound interference
- Wound: blood supply, infection/contamination, tissue viability/fluid accumulation, movement/pressure/skin tension, neoplasia
Problem Wounds
- Disrupted wounds
- Pressure wounds
- Wounds in areas of movement & pressure
Factors Leading to Disrupted Wounds
- Wound tension
- Infection
- Haematoma/seroma
- Suturing nonviable tissue
- Wound molestation
Dehiscence
- Wound separation or rupture.
Halsted's Principles
- Gentle tissue handling
- Meticulous haemostasis
- Preservation of blood supply
- Strict aseptic technique
- Tension-free closure
- Accurate tissue apposition
- Eliminate dead space
Pressure Wounds
- Decubital ulcers
- Bony prominences (greater trochanter, tuber coxae, acromion, ischial tuberosity, lateral humeral/tibial condyle, lateral malleolus, sides of digit 5, olecranon, calcaneal tuberosity, sternum).
- Repeated trauma (sitting/lying)
- Prolonged recumbency (neurological, spinal, or multi-orthopedic patients)
- Bandage-induced pressure sores
Prevention of Decubital Ulcers
- Turn recumbent dogs every 1–4 hours.
- Meticulous nursing/skin care (keep wound bed clean and dry, padded).
- Treat underlying conditions to prevent recumbency.
- Relieve pressure (e.g., donut dressings, splints).
Prevention of Bandage Sores
- Proper bandage placement and monitoring.
- Prevent slipping.
- Not overtight.
- Careful padding over bony prominences.
- Less is more.
- Care with rigid fixation (casting/splinting.)
- Place opposite healing wound.
- Awareness of swelling.
- Use bivalve casts.
- Regularly check
Movement and Pressure
- Wounds over joints: tension, compression, and shearing forces.
- Meticulous attention to closure.
- Casting/splinting.
- Paw pad wounds: compression with weight bearing, suture pull-through, spread with weight bearing pulls wound edges apart, bandaging, and splinting.
- Tension-relieving sutures.
- Large diameter monofilament sutures can be helpful.
- Sock/bandaging for protection during walks/activity.
Chronic Wounds—Movement and Pressure
- Axillary and inguinal wounds
- Collar wounds
- Shearing movement with ambulation
- Meticulous closure
- Debride and close
- Resect and close
- Reconstructive flaps
Infected Wounds
- Inhibits wound healing
- Chronic/recurrent wounds
- Causes wound dehiscence
- Surface contaminants may not reflect infective agents.
- Deep tissue culture evaluation is necessary.
- Nature of wounding
- Punctures from a bite,
- Underlying issues
- Foreign bodies
- Grass seeds, surgical implants, bone sequestra, debris/contaminants
Nature of Wounding
- More energy applied to tissues → increase in vascular damage
- Less blood supply → less O2, fewer plasma proteins
- Slower inflammation response → prolonged inflammation & more likely to cause infections in damaged tissues.
- Shearing creates dead space
- Penetrating foreign bodies create dead space with avascular surface exposure for bacteria
Trauma, Contamination, and Infection
- Illustrates the interplay between wound layers (skin, subcutaneous tissue, muscle) and the presence of dead space.
- Immune response is limited; proteins and O2 cannot penetrate well.
- Wounds frequently heal by granulation; sometimes, pus is a result and antibiotics should be considered.
- Chronic draining sinuses, devitalized tissue, and foreign bodies are considered factors that increase the risk of infection or incomplete healing.
Approach to a Draining Tract
- Diagnostics
- Radiographs: Plain or contrast
- Impression smear
- Bacteriology/C+S: Culture & sensitivity testing
- CT/MRI
- Surgical exploration of the tract +/- probing is recommended.
- Identify and remove the cause.
- Choose to heal via secondary intention or excision.
- Tissue samples (anaerobic & aerobic)
- Thoroughly lavage the area.
- Empirical antibiotics.
- Modify antibiotic usage as culture results develop.
Penetrating Wounds—Cat Bite Abscess
- Cat bite abscess
- Commonly associated with puncture wounds, or crush injury
- Rapidly occurring swelling
- Often present with systemic signs, e.g., pyrexia, anorexia, malaise, and/or peripheral lameness.
- Localized/systemic signs are considered to differ for wounds in aggressive/timid patients.
- Important to differentiate from other causes of similar presentation (e.g., upper respiratory tract infections, dental disease, and foreign body ingestion)
Cat Bite Abscess—Treatments
- Presented before abscessation: no need to open it.
- Antibiotics.
- Pain relief (NSAIDs if hydrated).
- Presentation with abscessation
- Antibiotics
- Lance, drain, flush, place drain (if needed, beware of dead space).
- Pain relief (NSAIDs if hydrated).
- Bacteria (Pasteurella, Staph, and Strep - aerobes + anaerobes)
- Broad-spectrum antibiotics (e.g., amoxy-clav, clindamycin, cephalosporins)
Oropharyngeal Penetrating Trauma – Stick Injuries
- Acute presentation (within 7 days)
- Oral pain, dysphagia, dyspnea, submandibular or cervical swelling, abscesses, and pain during mouth opening.
- Pyrexia.
- Injury observed or knowledge of stick catching/carrying.
- Chronic presentation (> 7 days)
- More common in presentation
- Systemically well (most common presentation).
- Recurrent cervical or submandibular swelling/discharging sinus
Oropharyngeal Stick Injuries—Treatment
- Acute
- Oral cavity and pharynx examination.
- Foreign material retrieval.
- Cervical and thoracic radiographs.
- Assess for signs of infection.
- Explore the tract surgically → avoid chronic fistula formation.
- Inspect dorsal esophagus for tears.
- Chronic
- Recurrent cervical swellings/discharging sinuses.
- Original wound may be unknown.
- Meticulous exploration/debridement of diseased tissue and removal of foreign matter.
Surgical Drains
- Tissue apposition and obliteration of dead space.
- Remove fluid that supports bacterial growth.
- Relieving pressure to allow for tissue perfusion
- Remove inflammatory mediators, bacteria, necrotic tissue, foreign material.
- Drain itself incites an inflammatory response
- Open drains (passive)
- Penrose drain.
- Capillary action.
- Gravity dependent.
- High surface area to volume ratio.
- Fenestration contraindicated.
- Closed suction drains (active)
- Tubing & suction device/vacuum.
- Fenestrations
- Less risk of contamination
- More effective fluid removal.
- Reduced risk of ascending infection.
- Easily portable
- Does not require a lot of dressing.
- Can collect and record fluid
- Constant suction decreases occlusion
- Loss of vacuum; occlusion by clots; premature removal by clients is often necessary to consider.
Placing a Penrose Drain
- Proximal end: deep in the wound; use a stab incision adjacent to wound.
- Distal end: secured to skin using a single suture.
- Cover with a dressing.
- Avoid exiting through the wound incision.
- Avoid using for wound flushing.
Activating Suction
- Wait 4–6 hours post-op before activating.
- Compress the grenade to open the port.
- Close the port (cap/clamp tubing)
- Release compression → negative pressure.
- Use an adhesive dressing for the exit site.
- Use a shirt/stockinette/bandage to protect tubing/grenade.
Maintaining an Active Suction Drain
- Regularly monitor and record fluid quantity.
- Empty drain when half-full.
- Monitor the strength of suction; it decreases as the grenade fills (and reaches 20–30% capacity).
- Remove when fluid production reduces to <2-4 ml/kg/24 hours.
Drain Removal
- Passive drain removal:
- Slowed or unchanged fluid production (likely 2–5 days).
- Cut end to prevent contamination, then withdraw.
- Anchor suture is cut before removal.
- Active drain removal:
- < 2-4 ml/kg/24 hours of fluid production.
- Gently remove drain with cutting finger trap.
- Ensure complete drain removal, and leave exit hole to heal by secondary intention.
Ingress/Egress Placement and Removal
- Used in inguinal or axillary regions.
- Reduce bacterial contamination into drain.
- Remove ‘dirty’ end using gloved hands.
- Pull the full drain out by the remaining part sticking out.
- Pull drain out from that end.
Chest Drains
- Intermittent or continuous drainage.
- Remove when fluid production slows.
- Administer IV antibiotics if an infection is suspected.
- Take precautions for patient sterility (nosocomial infection)
- Take precaution to prevent patient interference.
Chest Drainage—Thoracocentesis
- Intermittent drainage (every 4-6 hrs.) can be helpful for small-volume fluid removal.
Chest Tube Placement
- A neurovascular bundle is important to recognize when performing a chest tube placement.
- Skin incision needs to be above the 9th or 10th intercostal space.
- Subcutaneous tunnel should be created to allow for the positioning of the J wire to be placed.
- A small bore catheter over J wire.
Abdominal Drainage
- Palliative drainage for ascites (intermittent abdominocentesis).
- Open drainage is considered with septic peritonitis.
- Closed suction drain is often used (Jackson-Pratt).
- Drains frequently get blocked or walled off.
Small Bore Chest Tube
- Video tutorials can be helpful for small bore chest tube placement.
- Mila Pneumothorax Catheter Placement is a good introductory reference resource.
Step-by-Step Chest Tube Placement
- Search for appropriate videos using specific key words (e.g., “step-by-step chest tube placement video" or "chest tube placement procedure veterinary")
Introduction to Pharmacology
- RCVS Day One Competences 7 and 23
- Prescribing & dispensing meds safely & responsibly (according to legislation & guidelines).
- Developing appropriate treatment plans and administering treatments considering resources and public health considerations.
What is Pharmacological?
- Drug is a chemical or substance given to a living organism to produce a biological effect.
Lecture Learning Objectives
- Be aware of various ways to name medications.
- Drugs are known by their International Non-proprietary Name (INN), also known as the generic name, assigned by the World Health Organization (WHO).
- Drug companies may also use a brand name, known as the proprietary name.
Lecture Learning Objectives
- Identify and use the active ingredients as the primary term of reference when describing a veterinary medicine, such as:
- Metacam (meloxicam)
- Frontline (fipronil.)
- Cerenia (maropitant)
- Alfasan (alfaxalone).
Introduction to Pharmacology
- RCVS Day One Competence 7
- Prescribing and dispensing medicines correctly and responsibly
- Develop appropriate treatment plans and administer treatments in the interests of the patient, considering available resources and public health/environmental considerations.
- Order to help achieve competence, read pre-reads prior to each lecture, this will help you better understand tricky topics rather than spending time on the easy parts of the lecture.
What is Pharmacology?
- It's the study of drugs and their effects on the body.
- It helps understand how to safely and effectively use drugs to treat patients.
What is a Drug?
- It's any chemical or substance that produces a biological effect in a living organism.
Learning Objectives
- Be aware of the various ways of naming medications.
- Identify and use the active ingredient as the primary reference when describing a veterinary medicine.
- Understand groupings of medicines into classes related to structure and properties.
- Describe a veterinary medicine in terms of physical characteristics.
- Give examples of excipients and understand their role in medication formulation.
- Understand the process of medication development, including drug discovery drivers, costs, and timetables.
Learning Objective 1
- Be aware of the various ways of naming medicines.
Naming Medicines
- Drugs are known by their International Non-proprietary Name (INN), a generic name assigned by the WHO.
- Drug companies sometimes use a brand/proprietary name to package & sell products.
Learning Objective 2
- Identify and use the active ingredient as the primary reference when describing a veterinary medicine.
Active Ingredient Identification
- Active ingredient is also known as the generic name.
- The active ingredient, no matter the brand name, is the same.
Learning Objective 3
- Understand the grouping of medicines into classes related to structure & properties
Drug Grouping & Related Properties
- Drugs can be grouped by their physicochemical properties (chemical nature), the related mechanism of action, or the clinical outcome, which helps us with prescribing.
Learning Objective 4
- Describe a veterinary medicine in terms of its physical characteristics.
Physical Characteristics
- Description of the physical properties of the drug, e.g., tablets, capsules, injections, spot-ons, suspensions, iv infusions, drenches, creams & ointments, and their suitability for particular conditions.
Learning Objective 5
- Give examples of excipients and understand their role in medication formulation
Excipients
- Substances added to medications to improve attributes such as absorption, palatability, stability, and manufacturability, e.g., fillers, lubricants, flavorings, and preservatives.
Learning Objective 6
- Understand in principle the process of medicinal development
Medicinal Development
- Process of developing a drug from initial discovery to commercialization, involving phases such as preclinical development, clinical trials (Phase I-IV), regulatory approval, & post-marketing surveillance; also highlighting factors such as the costs and timelines (often >$2 billion and 10-15 years) involved in the drug development process.
Developing Prescribing Skills
- Framework for prescribing, which includes assessing patient, identifying treatment options, providing patient information, and making a prescription.
- Key Prescribing Skills, including a method to review a prescription, which factors should be considered in the management of patients and choosing the correct combination of drugs are detailed.
Prescribing Information: Summary of Product Characteristics
- Website (e.g., VMD) provides summary information (including uses, dosage, administration, and warnings) for veterinary products.
Introduction to Pharmacology
- RCVS Day One Competence 7 (prescribing and dispensing medicines safely & responsibly).
- RCVS Day One Competence 23 (developing appropriate treatment plans and administering treatments in a patient-centered and responsible way; considering resources, public health, and environmental factors).
Learning Objectives
- Be aware of the various ways
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Description
This quiz explores various aspects of clinical reasoning in anesthesia, particularly focusing on Type 1 and Type 2 reasoning. Participants will answer questions regarding lesion classification, cognitive loads, and scenarios during the recovery phase after anesthesia. Test your understanding of clinical practices related to anesthesia management.
