Veterinary Anesthesia and Fluid Therapy

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Questions and Answers

What is indicated for fluid therapy specifically in cats with certain weight conditions?

Cats weighing less than 2 Kg (correct)

Cats weighing between 2 Kg and 6 Kg

All cats regardless of weight

Cats weighing more than 6 Kg (correct)

What is a primary concern associated with the inhalant induction and maintenance in small animals?

High volume of anesthetic required

Increased recovery time

Risk of cardiopulmonary complications (correct)

Low patient tolerance

Which procedure is generally not applicable to cats when it comes to intubation?

Endotracheal intubation (correct)

Tracheostomy

Retrograde intubation

Nasal intubation

Which factor is identified as a risk for anesthetic-related death in small animals?

Presenting with a chronic condition Signup and view all the answers

What is a common method for providing ventilation during anesthesia in small animals?

Intermittent positive pressure ventilation (IPPV) Signup and view all the answers

What is the recommended blood volume for a dog before surgery?

90 ml/kg Signup and view all the answers

Which of the following is NOT a consequence of hypothermia during surgery?

Increased metabolism Signup and view all the answers

Which intervention is recommended to prevent hypothermia during surgery?

Prewarming Signup and view all the answers

What is a clinical sign of inadequate depth of anesthesia?

Sudden changes in heart rate Signup and view all the answers

Which of the following can increase the risk of peri-anesthetic mortality?

Emergency procedures Signup and view all the answers

What should be monitored closely to prevent hypothermia during surgery?

Room temperature Signup and view all the answers

Which factor is associated with an increased likelihood of blood transfusion?

Loss exceeding 20% Signup and view all the answers

What is one of the 7 H's of anesthesia that signifies a respiratory issue?

Hypercapnia Signup and view all the answers

Which treatment option is indicated for managing regurgitation?

Perform suction and lavage with saline Signup and view all the answers

What defines hypoxaemia in terms of arterial blood oxygen levels?

PaO2 < 80 mmHg Signup and view all the answers

Which drug can be employed to treat hypertension by promoting vasodilation?

Acepromazine Signup and view all the answers

What is a common cause of hypertension during anaesthesia?

Low anaesthetic depth Signup and view all the answers

In the case of worsening haemorrhage, what compensatory response occurs in the body?

Increase in heart rate and minute volume Signup and view all the answers

What should be monitored when a patient experiences hypoxaemia?

PaO2 levels dropping below 80 mmHg Signup and view all the answers

What role does sodium bicarbonate play in treating regurgitation?

It neutralizes acidic regurgitated material Signup and view all the answers

Which method should be avoided to prevent hypercapnia?

Change the patient's position frequently Signup and view all the answers

What complication can arise from increased dead space in ventilation?

Rebreathing of CO2 Signup and view all the answers

Which of the following is a potential treatment for hypercapnia?

Manual ventilation Signup and view all the answers

What condition is indicated by a 'Shark fin' appearance in capnography?

Airway obstruction Signup and view all the answers

What is a common cause of regurgitation leading to aspiration pneumonia during anesthesia?

Inadequate fasting time Signup and view all the answers

Which factor is NOT associated with rebreathing of CO2 in ventilation?

Low tidal volume Signup and view all the answers

What is the primary physiological effect of anaesthetic drugs on the respiratory system?

Depressant effect on the respiratory centre Signup and view all the answers

Which of the following is NOT a cause of hypercapnia?

Decreased cardiac output Signup and view all the answers

What is a common consequence of inadequate ventilation during anaesthesia?

Hypoventilation and hypercapnia Signup and view all the answers

Which method can be used as an alternative to tracheal intubation in case of difficult airway management?

Tracheostomy Signup and view all the answers

Which factor can lead to a decrease in functional residual capacity during anaesthesia?

High oxygen concentrations Signup and view all the answers

What action should be taken if a patient shows signs of laryngeal spasm during intubation?

Apply a topical anaesthetic Signup and view all the answers

What is an effective initial step in managing difficult intubation?

Pre-oxygenation of the patient Signup and view all the answers

Which technical error could directly lead to hypercapnia during a procedure?

Faulty ventilatory settings Signup and view all the answers

In the context of anaesthesia, what does increased ETCO2 indicate?

Hypoventilation Signup and view all the answers

Which statement about pre-oxygenation is correct?

Decreases the risk of hypoxemia during intubation. Signup and view all the answers

Study Notes

Common Complications & Accidents in Veterinary Anaesthesia

The presentation is on common complications and accidents in veterinary anaesthesia.
The speaker, Hanna Machin, is a lecturer in Veterinary Anaesthesia at the University of Surrey.
The date of the presentation is October 4, 2024.

Learning Objectives

The objectives are to describe approaches to the prevention and management of adverse events during anaesthesia in domestic animals.
Another objective is to outline the common risk factors associated with anaesthetic-related morbidity and mortality.

Respiratory Complications: Difficult Intubation

Pre-oxygenation is crucial for difficult intubations.
Different sizes of endotracheal tubes (ET tubes) are available.
A stylet/bougie can help guide the ET tube.
Changing position during intubation may be necessary.
Assessing the anaesthetic plane is important.
Topical anaesthetics can help with laryngeal spasms in cats.
A flexible fibre-optic endoscope can be used for difficult intubations in cases with oral masses, inability to open the mouth, or fractures.
Intubation problems can involve the oesophagus, epiglottis, and trachea.
Intubation techniques involve placing the laryngoscope blade under the epiglottis, pressing down to expose the trachea, holding the laryngoscope in the non-dominant hand, and keeping the tongue between the first and second fingers.

Respiratory Complications: Difficult Intubation (Continued)

Alternative methods for securing the airways include retrograde intubation and temporal tracheostomy.
Retrograde intubation uses a guidewire and hypodermic needle.
Temporal tracheostomy involves creating a temporary opening in the trachea.

Physiology Recap

Anaesthetic drugs depress the respiratory centre, central and peripheral chemoreceptors, and intercostal muscles and diaphragm.
Other receptors, such as pain and emotional stimuli, can influence the hypothalamus.
Position and high oxygen concentrations can affect the functional residual capacity and lead to atelectasis, hypoventilation, and hypercapnia.
Hypoxaemia is potentially serious.

Respiratory Complications: Hypercapnia

Hypercapnia occurs when ETCO2 is greater than 45 mmHg.
Metabolic causes include fever, hyperthermia, malignant hyperthermia, seizures, and hyperthyroidism.
Pulmonary perfusion factors, such as increased cardiac output and blood pressure, also contribute to the risk of hypercapnia.
Alveolar ventilation can also lead to high CO2 levels through hypoventilation and rebreathing.
Technical errors like faulty CO2 absorbents, valves, or issues with fresh gas flow can result in elevated partial pressure of carbon dioxide

Respiratory Complications: Hypercapnia (Consequences)

Stimulation of the sympathetic nervous system (SNS) can result in mild tachycardia and hypertension at CO2 levels from 60-90mmHg.
At higher levels (>90 mmHg), CO2 can cause CNS and cardiovascular depression.
Symptoms of hypercapnia include vasodilation, tachycardia, central nervous system depression (leading to apnoea), respiratory acidosis and cardiac contractility impairment leading to arrhythmias and death.

Respiratory Complications: Hypercapnia (Treatment)

Treat the underlying cause.
Reduce anaesthetic depth.
Consider manual or mechanical ventilation.

Respiratory Complications: Rebreathing of CO2

Causes related to dead space in the respiratory system and/ or problems in the non-rebreathing system.
Inadequacy of fresh gas flow.
Insufficient expiratory time (High RR) are also potential causes.
Exhausting carbon dioxide, issues with the inspiratory and expiratory valves are also possible.

Respiratory Complications: Airway Obstruction

The ET tube may become occluded by mucous, blood, masses, or regurgitation, presenting as a "shark fin" appearance on the waveform.
Suction and re-intubation may be required.
Bronchoconstriction (e.g., due to asthma) can also obstruct the airway.
A kinked ET tube or obstruction in the expiratory limb of the breathing system can cause airway obstruction.

Respiratory Complications: Regurgitation

Regurgitation can lead to aspiration pneumonia.
Causes include inappropriate fasting times, drugs, hiatal hernia, gastroesophageal reflux, lighter planes of anaesthesia, and position changes.
Preventative measures include adequate fasting time, rapid sequence induction, cuffed ET tubes, proper positioning, and appropriate depth of anesthesia.

Respiratory Complications: Regurgitation (Treatment)

Head down position recommended
Performing suction and lavage with saline or tap water
Measuring the pH of regurgitated material to assess acidity.
Instilling sodium bicarbonate if material is acidic.
Careful management of sedation levels.

Respiratory Complications: Hypoxaemia

Hypoxaemia involves a low concentration of O2 in the arterial blood (PaO2 ) less than 80 mmHg (SpO2 <90%).
Hypoventilation, impaired diffusion, ventilation/perfusion (V/Q) mismatch, and right-to-left shunting can cause hypoxaemia.
Decrease inspired fraction of O2 (FiO2) values may also cause oxygen deficiency.
Equipment obstruction is a contributing factor.

Respiratory Complications: Hypoxaemia (Consequences)

Consequences include hypoxia and low O2 levels in tissues, conversion of aerobic to anaerobic metabolism (lactate), and metabolic acidosis.
Initial response often involves sympathetic nervous system (SNS) activation leading to tachycardia, increased myocardial contractility, and vasoconstriction.
Decrease in myocardial oxygen delivery can lead to arrhythmias.
Bradycardia, hypotension, and respiratory depression eventual occur.

Respiratory Complications: Hypoxaemia (Treatment)

Pre-oxygenation. mechanical ventilation, recruitment manoeuvres.
Improving cardiac output, and arterial blood pressure to improve perfusion.
Treat underlying diseases, and pain/shivering/hyperthermia.

Respiratory Complications: Hypoventilation

Hypoventilation is inadequate/insufficient ventilation during anaesthesia leading to low ETCO2 .
Factors leading to inefficient ventilation include abdominal distension, pregnancy , and laparoscopic surgery.
Pulmonary disease, and/or airways obstruction.
Neuromuscular diseases.
Drug-induced respiratory depression.
Obesity/hypothermia also play a role.

Respiratory Complications: Hypoventilation (Mismatches & More)

Alveolar hypoventilation or atelectasis
Ventilation/Perfusion (V/Q) mismatch, and shunts.
Shunt- ventilation or cardiac output problems causing a V/Q mismatch may occur.

Respiratory Complications: Hypoventilation (Treatment)

Administer oxygen.
Mechanical ventilation or manual support.
Recruitment manoeuvres may be helpful.
Adjust the depth of anesthesia.
Addressing underlying causes (e.g., pain, abdominal distension) is crucial.

Respiratory Complications: Apnoea/Respiratory Arrest

Drugs (induction agents, ketamine, opioids)
Excessive anaesthetic depth can cause apnoea.
Vagal stimulation (e.g., during intubation or visceral traction).
Weaning from a ventilator or manual ventilation.
Nerve or cardiac damage.

Respiratory Complications: Apnoea/Respiratory Arrest (Treatment)

Administer oxygen.
Immediate intubation and ventilation.
Reducing anesthetic depth.
Cardiopulmonary resuscitation (CPR).

Respiratory Complications: Tachypnoea

Tachypnoea is rapid breathing with decreased end-tidal carbon dioxide (ETCO2) and increased respiratory rate and can cause CO2 issues.
Inadequate anesthetic depth.
Nociception (pain) or increased CO2 production (e.g., hyperthermia).
Hypoxaemia.
Administration of drugs (opioids) in conscious animals.

Cardiovascular Complications: Bradycardia

Bradycardia is a slow heart rate, which decreases cardiac output and tissue perfusion.
Certain breeds are naturally predisposed to lower heart rates.
Causes include drugs (opioids, alpha 2 agonists).
Excessive anesthetic depth.
Raised intracranial pressure.
Vagal response (positioning, surgical manipulation).
Hypothermia.
Electrolyte imbalances.

Cardiovascular Complications: Bradycardia (Treatment)

Addressing the underlying cause is crucial.
Pharmacologic interventions (e.g., antagonists for drugs, anticholinergic agents).

Cardiovascular Complications: Atrio-ventricular Blocks (AV Blocks)

Grades of AV blocks are classified by differences in the heart's electrical conduction.
Treatment methods include drug reversal, anticholinergic administration, and pacemaker insertion (for 3rd degree AV block).

Cardiovascular Complications: Tachycardia

Tachycardia involves an elevated heart rate.
Causes include SNS stimulation, drugs (e.g., anticholinergics, ketamine), cardiac disease, anaemia, haemorrhage, hypovolaemia, hypotension, and hypoxaemia.
Tachycardia decreases diastolic filling.

Cardiovascular Complications: Tachycardia (Treatment)

Addressing underlying causes and administering beta-blockers (e.g., esmolol, propranolol).

Cardiovascular Complications: Ventricular Tachycardia/Fibrillation

Ventricular tachycardia and fibrillation are serious abnormal heart rhythms.
Causes include drugs and heart disease.
Treatment (for Pulseless V Tach or V Fib) involves lidocaine bolus and/or continuous infusion, defibrillation, and address the underlying cause (as with previous problems).

Cardiovascular Complications: Hypotension

Hypotension involves low mean arterial pressure (MAP).
Common causes, using the model provided include decreased systemic vascular resistance (SVR) from vasodilation, poor preload, weakened cardiac conctractiliity and reduced cardiac output.
Addressing the underlying causes, administering fluids, and using vasopressors.

Cardiovascular Complications: Hypotension (Causes, Simplified Model)

Decreased SVR (Vasodilation): Anaesthetic agents, hypothermia, sepsis, anaphylaxis, hypercapnia.
Decreased preload: dehydration, hypovolemia, 3rd spacing.
Decreased contractility: structural cardiac disease, cardiac tamponade, some inhalational agents (propofol), electrolyte imbalances (increased potassium).
Bradycardia: see bradycardia section.

Cardiovascular Complications: Hypotension (Treatment)

Address the cause based on the section where the etiology was discussed.
Administer fluids, adjust anesthetic depth, and administer appropriate drugs.

Cardiovascular Complications: Hypertension

Hypertension means elevated blood pressure.
Causes stem from increased myocardial work and demand, excessive pain/nociception, light planes of anesthesia and underlying disease (like renal insufficiency or cardiac disease).
Treatment involves addressing the cause and/or administering beta-blockers, vasodilators, or other agents as needed (as described in the corresponding section).

Haemorrhage

Haemorrhage causes a reduction in plasma volume and haemoglobin, decreasing oxygen carrying capacity of the blood and can lead to problems in body response (CO/minute volume, tissue extraction affecting hypoxaemia, lactic acidosis, hypotension).
Factors include determining bloodvolume before, during and after surgery and assessing blood loss amount through changes in PCV/TP, signs leading to tachycardia, hypotension and changes in Et CO2, and consideration of blood loss values and lactate increases.
Treatment and prevention methods involved replacing blood losses and using whole blood, packed red blood cells and/or hemoglobin-based oxygen-carrying products (as appropriate).

Hypothermia

Hypothermia involves core body temperature below 38.5°C in dogs and cats.
Anaesthetic drugs, exposure to low ambient temperatures.
Causes stem from the effects of anaesthetic drugs on the thermoregulatory center and exposure to low ambient temperatures.
Symptoms include a decrease in metabolism, prolonged recovery, vasoconstriction, increased oxygen consumption, shivering, hypoventilation, increased wound infections, impaired coagulation, and increased intraoperative blood loss.
Increased hospital stays or potentially death.

Hypothermia (Preventing/Treating)

Prevent/treat with warm fluids, close monitoring, low gas flow, and active rewarming.
Reduce or avoid alcohol-based products and minimize clipping and prewarming to maintain body temperature as appropriate.

Inadequate Depth of Anaesthesia

Clinical signs of inadequate depth include sudden increases in heart rate and arterial blood pressure.
Changes in respiratory rate/pattern, eye position/reflexes (such as dilated pupils or strong palpebral reflexes) and jaw tone.
Differentiation from nociception is essential for determining adequate anesthetic plane.
Increasing inhalants, propofol, alfaxalone, or ketamine can help increase depth of anesthetic in unresponsive cases.

The 7 H's of Anaesthesia

The presentation covers several complications including hypothermia, hyperthermia, hypercapnia, hypocapnia, hypotension, haemorrhage, and hypoxaemia/hypoxia.

Confidential Enquiry into Perioperative Small Animal Fatalities (CEPSAF)

The CEPSAF is a study examining risk factors for peri-anaesthetic mortality in small animals.
It collects data from many sedation and anaesthesia cases and focuses on ASA status, urgent/emergency and major vs. minor procedures, age and size, and details on inductions, intermittent positive pressure ventilation (IPPV), sedation, endotracheal intubation in cats, and use of fluid therapy.
The findings should be interpreted carefully.

References

Several veterinary anaesthesia and related articles and books are referenced.
These include research by various veterinary practitioners and researchers.
Key publications and references are listed for further study.

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Description

Test your knowledge on veterinary anesthesia, fluid therapy, and related concerns for small animals. This quiz covers key topics such as intubation challenges in cats, risk factors for anesthetic mortality, and the importance of maintaining proper body temperature during surgical procedures.