Lecture 17: Anesthetic Management of Patients with CV Disease

What are our anesthetic concerns with a cardiac patient?

• Heart failure and death

• Fluid overload

• Arrhythmias

• Making the disease worse?

• Is a heart murmur automatically associated with ↑ anesthetic risk?

What are the general effects of CV disease?

• Altered cardiac output

• Poor perfusion → brain, kidney, liver, etc.

• Increased ventilation/perfusion inequality

• Respiratory compromise → heart failure etc.

What important physiologic factors are affected by several anesthetic drugs leading to altered blood flow?

• BP = CO x systemic vascular resistance (SVR)

• CO = HR x stroke volume (SV)

What anesthetic drug classes affect SVR, HR, and SV?

• SVR affected by alpha2 agonist, inhalants, acepromazine

• HR affected by alpha2 agonists, NMDA antagonists

• SV affected by alpha2 agonists

Why does increasing preload not always mean increasing CO?

a failing heart may not tolerate an increased fluid load → congestion

What evidence found on PE should you be paying attention to when suspecting cardiac disease?

Presence gallop rhythm ***:

• Gallop in cats — hypertrophic cardiomyopathy

• Gallop in dogs — dilated cardiomyopathy, degenerative valve disease, PDA (machinery)

Vascular Exam:

• bounding pulses

• poor pulses

• jugular venous distension associated with right-sided heart dysfunction

What diagnostic can be useful in a cardiac patient, but DOES NOT take the place of other diagnostic tools and does not add significantly to clarifying anesthetic risk?

NT-proBNP

If ___________ is present the cardiac patient should NOT be anesthetized unless condition requiring therapy/surgery is life threatening.

pulmonary edema

Anesthetic risk of a cardiac patient is reduced if?

• Cardiac disease accurately diagnosed

• There is adequate preoperative preparation

• Reasonable anesthetic plan used

• Excellent monitoring and response is available

What preoperative care should be performed in a cardiac patient?

• Consider cardiac medications, benefits? Risks? - ******Pimobendan****, ACE inhibitors or other BP meds??

• Pre-hospital preparation (Gabapentin, trazodone)

• Avoid stress, be prepared and have a plan

• Opioids!

• Monitor patient closely at all times!!

• Pre-oxygenate if able

How should a cardiac patient be induced?

• Prevent stress, easy/smooth intubation

• Monitor early!!

• Start with lower dose and give at a slower rate

• Know the disease and be prepared, arrhythmias etc.

• Mask/chamber inductions should be avoided

How should a cardiac patient be maintained under anesthesia?

• Use drugs that are short acting and titratable

• Use reversible drugs if possible

• Multimodal anesthesia/analgesia

How should fluid therapy be handled in a cardiac patient?

• If a patient is hypovolemic, then use a balanced electrolyte solution (ex. LRS), but avoid IVF boluses.

• If a patient has a normal hydration status, fluids may not be needed or use a much lower rate such as 1-3 ml/kg/hr

• Use supportive BP meds such as Dobutamine/Dopamine etc.

What monitoring is important in a cardiac patient?

• Even more important for these guys: ECG, BP, SPO2, Capnography, temperature

• Important to treat hypotension according to the patient’s disease and awake condition

• BP=CO x SVR cardioprotective treatment

What aspects of recovery from anesthesia are important in a cardiac patient?

• Greatest risk due to pain, hypoventilation, hypothermia → stress!

• Monitor/Observe!!! Treat problems early.

• Multimodal analgesic plan → consider cold compresses and local analgesia. Caution with NSAIDs?

• Oxygen supplementation

• Keep the recovery room quiet & calm!! Avoid stress!!

What are the patients with impaired CV?

• Cardiomyopathies: Hypertrophic, Restrictive, Dilated

• Pericardial tamponade

• Valvular heart disease: Mitral valve insufficiency

What is the goal of anesthesia of a MMVD patient?

maintain forward flow and minimize regurgitation of blood flow

What is preoperative preparation aimed at in a MMVD patient?

Preoperative preparation aimed at reducing the regurgitant fraction of SV and controlling pulmonary edema. Treat as long as possible prior to anesthesia…

• pimobendan*

• ACE inhibitors, diuretics

• Minimize anxiety and stress (gabapentin etc prehospital)

• Opioids!!

What drugs should be avoided in MMVD patients?

• Avoid alpha2-agonists if ACVIM stage B2 or higher

• Avoid IV fluid overload

What should be avoided in a cat with HCM?

ketamine, telazol, and stress

How do you handle anesthesia for the HCM patient?

• Maintain preload to aid cardiac filling→ Hydration, anti-vomiting etc.

• Increase afterload: Vasodilation will augment outflow tract obstruction (SAM, LVOT)

• Avoid increases in contractility: Dopamine and dobutamine should be avoided…

• Avoid tachycardia: Increases in HR and contractility can cause dynamic outflow obstruction from the heart. Avoid anticholinergics?

• Avoid things that ↑ myocardial oxygen consumption– make the heart work harder (Ex. Hypothermia →shivering)

How is anesthesia managed in canine DCM patients?

• Maintain or increase HR in order to maintain CO

• Avoid afterload increases

• Management is similar to MV/TV regurgitation

How is anesthesia managed in pericardial tamponade and constrictive pericarditis cases?

• Impaired CO secondary to reduced preload

• Pericardiocentesis recommended prior to anesthesia - Can be done under mild sedation + local anesthetic

• Pretreat with fluids!!!

What are heartworm patients more prone to?

• Patient more prone arrhythmias under anesthesia and/or decreased CO if large number of worms

• Pulmonary hypertension

How is anesthesia handled in patients with pulmonary hypertension?

Postpone elective procedures until pulmonary arterial pressure lowered (and primary underlying respiratory disease stabilized).

During anesthesia:

• Inhalants relax vascular smooth muscle

• Maintain preload

What is the aim of the anesthetist in cases of traumatic myocarditis with ventricular arrhythmias developing 12-24 hrs later?

• Avoid tachycardia

• Avoid factors reducing myocardial oxygenation

• Treat arrhythmias

How is anesthesia handled in patients with hypertension?

• Delay anesthesia until BP under control if possible

• Maintain blood pressure during anesthesia

• Be aware of comorbidities!

Anesthetizing patients with cardiac disease can be safe with:

• proper preparation

• accurate diagnosis

• multimodal protocols

• careful monitoring

• knowledge to treat problems