7. Anesthesia for Patients W/ CV Dz

Question 1

How can we reduce the risk of anesthesia with an animal with cardiovascular disease?

Answer 1

Accurate dz - Identify cardiac dz and know relevant pathophysiology
Treat reversible risk factors
Know CV therapy and possible interactions with anesthetics
Continue administering prescribed drugs
Use anesthetic protocol: that does NOT aggravate the hemodynamic effects of the CV condition
Understand adverse hemodynamic effects of sx

Question 2

What influences the risk vs benefit calculation?

Answer 2

monitoring and supportive care
organized planning inc chances of favorable outcome
and minimized anesthesia time

Question 3

How do we monitor and give supportive care in patients with CV Dz?

Answer 3

preoxygenation
IV access (mandatory)
Anticipate and prepare for complications - CV support drugs (dobutamine, ephedrine)
Inc vigilance of patient monitoring
Have 1 person dedicated to monitor patient - ECG, arterial BP (doppler, oscillometric), pulse oximetry (SpO2), capnography
Provide supportive care -a void hypothermia

Question 4

What is the pharmacokinetic effects of CV disease?

Answer 4

• Poor peripheral perfusion - Lower drug bioavailability after IM, SC
• Reduced drug volume of distribution -Greater sensitivity to injectable anesthetics
• Slower circulation time -Slower response after IV injection
• Reduced Cardiac Output -Increased rate of inhalation anesthetic uptake
• Increased V/Q mismatch - Slower onset and response to altered concentrations of inhalation anesthetics
• Reduced renal perfusion and hepatic blood flow

Question 5

What are the effects of anesthetics?

Answer 5

• Alteration of systemic vascular resistance - Vasodilation: Inhalants, acepromazine, propofol, alfaxalone
• Vasoconstriction: dexmedetomidine, ketamine
• Alteration in heart rate and rhythm
• Tachycardia: Anticholinergics, ketamine
• Bradycardia: opioids, alpha-2
• Impairment of calcium utilization
• Inhalants
• Development of intracellular acidosis
• Respiratory depression (propofol, alfaxalone, opioids,..)

Question 6

What are the goals for anesthesia

Answer 6

pre-anes exam: assess patient baseline values
maintain a stable CV system - maintain a normal HR, avoid further depression of myocardial func, cardiac output and O delivery, avoid alterations of arterial BP and avoid inc myocardial workload
Avoid inc in SNS tone
Choose anes. protocol adequate for cardiac condition
Keep anesthesia time as short as possible

Question 7

What does adequate and inadequate sedation cause?

Answer 7

• Adequate sedation for appropriate immobilization is often heavy and requires drugs with
  unfavorable cardiovascular effects
• Inadequate sedation increase patient stress: increase in catecholamines -> increased myocardial
  O2 demand -> increased risk of arrhythmias
• Fewer options for monitoring and support

Question 8

What is the dynamic left ventricular outflow tract obstruction?

Answer 8

• Ejection of blood from left ventricle can be impeded
• Mitral valve is displaced against the inner wall of ventricle and
  septum -> partially obstructing the passage
• Effects of DLVOTO are greater when:
  § Heart rate and myocardial contractility are increased
  § Left ventricular diastolic volume and afterload are decreased
• In humans, this is associated with an increased risk of sudden death.

Question 9

What are the hemodynamic goals in a patient with HCM?

Answer 9

do not inc myocardial contractility
avoid inc in myocardial O consumption
Maintain normal (low) HR, avoid tachycardia
Maintain or inc systemic vascular resistance
Avoid drugs dec afterload (will worsen DLVOTO)

Question 10

What are some HCM anesthetic implications?

Answer 10

• Avoid stress (catecholamine release)
• Administer 50-100mg Gabapentin 2-3 h beforehand
• Tx should be administered the day of GA (Beta blocker or Ca++ channel blocker)
• Pre-oxygenate
• Avoid anticholinergics (atropine/glycopyrrolate)
• Avoid ketamine (sympathomimetic effects)

Question 11

For cats with HCM, which sedatives could we use?

Answer 11

Opioids:
* Minimal effects on myocardial contractility, preload/ afterload
* Minimal sedation in cats, euphoria
Dexmedetmidine:
* Controversial, use low doses (5-7μg/kg)
* Beneficial in cats with DLVOTO: may eliminate outflow tract obstruction
Midazolam:
* Minimal cardiovascular depression
* Paradoxical agitation, useful as an adjuvant
Acepromazine:
* Vasodilation resulting in augmentation of DLVOTO and hypotension
Alfaxalone

Question 12

With fractious cats, which end of the dosing should we go?

Answer 12

high end with fractious cats