Cardiovascular Physiology and Treatment

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

What should be the first step in treatment for a hypotensive patient with a fluid deficit?

Administer a fluid bolus based on estimated deficit. (correct)

Start constant rate infusions immediately.

Assess the patient’s age and comorbidities.

Double the constant rate infusion rate.

How should the rate of norepinephrine infusion be adjusted if a patient's blood pressure does not improve after 5 minutes?

Double the rate to enhance blood pressure response. (correct)

Stop the infusion and reassess the patient.

Keep the rate the same and monitor for additional signs.

Decrease the rate by half to minimize side effects.

What is the free water deficit for a 20 kg dog estimated to be 7% dehydrated?

2 L free water deficit.

1 L free water deficit.

0.7 L free water deficit.

1.4 L free water deficit. (correct)

When initiating treatment for hypotension in patients, which factor should influence the approach taken?

Patient's comorbidities and age. Signup and view all the answers

If a patient's blood pressure improves after a bolus but declines later, what is the next recommended step?

Consider giving another bolus of fluids. Signup and view all the answers

What is the definition of tachycardia in small breed dogs?

HR > 180 Signup and view all the answers

What is one of the first steps in treating tachycardia under general anesthesia?

Assess anesthetic depth Signup and view all the answers

How does the intravascular volume affect blood pressure?

Increased intravascular volume increases blood pressure Signup and view all the answers

What should be suspected when a patient is moderately tachycardic and hypotensive?

Hypovolemia/dehydration Signup and view all the answers

What is the effect of larger breed dogs on tolerance to higher heart rates?

Larger breed dogs have a lower baseline functional heart rate Signup and view all the answers

What was the initial dose of propofol required for induction of anesthesia?

3.1 mg/kg Signup and view all the answers

What is one method used to correct hypoventilation in animals under general anesthesia?

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

What was the depth of anesthesia immediately after induction?

Lighter side Signup and view all the answers

What does the administration of ephedrine primarily aim to address?

Hypotension Signup and view all the answers

What should be prioritized to ensure adequate oxygen delivery during anesthesia?

Maximizing intravascular volume Signup and view all the answers

What role does vascular resistance play in blood pressure?

Increased vascular resistance results in higher blood pressure Signup and view all the answers

Which receptor does acepromazine antagonize?

Alpha-1 adrenergic Signup and view all the answers

What kind of effects does dexmedetomidine have on the cardiovascular system?

Vasodilation and reduced heart rate Signup and view all the answers

What is the minimum systolic blood pressure (SBP) for adequate end-organ perfusion?

90 mmHg Signup and view all the answers

What complication is the most commonly reported from general anesthesia in dogs and cats?

Hypotension Signup and view all the answers

How is the treatment threshold for hypotension often affected?

Measurement techniques underestimate it. Signup and view all the answers

What is the primary goal of monitoring cardiovascular stability during anesthesia?

Ensuring adequate oxygen delivery to tissues Signup and view all the answers

What is the standard definition of bradycardia in dogs?

HR < 50-80 beats per minute depending on size Signup and view all the answers

Which medications are typically used for treating bradycardia?

Atropine and Glycopyrrolate Signup and view all the answers

How is cardiac output calculated?

Heart rate multiplied by stroke volume Signup and view all the answers

What should be done in cases of hypotensive patients with bradycardia?

Assess depth of anesthesia and adjust as needed Signup and view all the answers

Which is NOT a factor that influences heart rate variability among different dog breeds?

Increased physical activity level Signup and view all the answers

What is a common characteristic of pediatric patients regarding cardiovascular stability?

Reliance on heart rate for cardiac function Signup and view all the answers

What might indicate the need for treating bradycardia in a patient?

Hypotensive status Signup and view all the answers

What is a potential complication of hypotension during anesthesia?

Increased all‐cause mortality 1 year post anesthetic event Signup and view all the answers

How does vasoconstriction affect blood pressure and perfusion?

It can improve blood pressure but may impair perfusion in some circumstances. Signup and view all the answers

What is the recommended starting dose for a beta agonist at 5 kg?

0.05 mcg/kg/min Signup and view all the answers

What intervention may be necessary for cats experiencing hypotension under general anesthesia?

Support with a syringe driver Signup and view all the answers

What statistical outcome is associated with cats experiencing hypotension during anesthesia?

They have 2.6x increased odds of death. Signup and view all the answers

What condition does hypotension NOT commonly lead to in humans post-anesthesia?

Sepsis Signup and view all the answers

What should be adjusted every 3-5 minutes when administering a beta agonist for hypotension?

The dosage of the beta agonist Signup and view all the answers

During the presentation of a healthy 26 kg Golden for surgery, which parameter was abnormal?

Respiratory rate Signup and view all the answers

Study Notes

Cardiovascular Consequences

Oxygen Delivery to Tissues (DO2) is calculated by multiplying Cardiac Output (CO) by Arterial Oxygen Content (CaO2).
Cardiac Output is determined by heart rate (HR) and stroke volume.
Bradycardia: Heart rate below the normal range for the species and breed.
- Dogs: HR < 50-80 bpm, with smaller breeds having a higher baseline.
- Cats: HR < 110-120 bpm.
Tachycardia: Heart rate above the normal range for the species and breed.
- Dogs: HR > 140-180 bpm, with smaller breeds tolerating higher heart rates.
- Cats: HR > 200-220 bpm.

Bradycardia / Bradyarrhythmias - Treatment

Treat bradycardia in hypotensive patients, patients with certain cardiac diseases, and pediatric patients.
Identify the cause of bradycardia before treating.
Consider adjusting anesthetic depth and ensure adequate oxygenation.
Anticholinergics can be administered to increase heart rate.
- Atropine: 0.02-0.04 mg/kg IV/IM, lasts 30-40 minutes.
- Glycopyrrolate: 0.005-0.01 mg/kg IV/IM, lasts 45-60 minutes.

Tachycardia / Tachyarrythmias under GA - Treatment

Evaluate anesthetic depth and ensure optimal analgesia.
Address hypoventilation by initiating IPPV if EtCO2 is elevated (e.g., > 60 mmHg).
Moderate tachycardia might not require intervention if adequate perfusion is maintained.
Moderate to severe tachycardia with hypotension requires immediate attention:
- Evaluate for hypovolemia and consider a fluid bolus (e.g., 10 ml/kg over 10 minutes).
- Reduce or discontinue sympathomimetic drugs (e.g., dobutamine, ephedrine).
- Consider beta-blockers (e.g., esmolol) or opioids.

Blood Pressure and Anesthesia

Blood pressure is an easily measured indicator of cardiovascular function during anesthesia.
Maintaining adequate oxygen delivery to tissues under anesthesia is the primary goal.
Blood pressure is proportional to both cardiac output (CO) and vascular resistance (VR).
Hypotension is the most common anesthetic-related complication.
Regional vascular resistance dictates organ perfusion. Vasoconstriction can improve blood pressure but compromise perfusion in some organs.

Hypotension as an Adverse Effect

Hypotension is associated with increased morbidity and mortality in human patients.
Cats that experience hypotension under general anesthesia have a 2.6 times higher risk of death.
Hypotension can lead to acute kidney injury (AKI), even in healthy adults.
Treatment of hypotension requires addressing the underlying cause.
Norepinephrine can be administered as a continuous rate infusion (CRI) to support blood pressure.

Case Example: Hypotension Management

A 26 kg Golden Retriever undergoing elective OHE exhibits hypotension after general anesthesia induction.
Initial Assessment: 1st oscillatory BP 109/60 (71) mmHg, HR 77, RR 7-9 bpm.
Treatment: Ephedrine 0.1 mg/kg IV was administered.
Monitoring: Blood pressure and heart rate are closely monitored.
Treatment Options: Repeated ephedrine boluses, ephedrine CRI, or norepinephrine CRI can be considered.

Acepromazine and Hypotension

Acepromazine is an alpha-1 adrenergic receptor antagonist, reducing venous tone and exacerbating blood volume shifts.
Acepromazine can contribute to hypotension by decreasing preload and cardiac output.

Dexmedetomidine and Hypotension

Dexmedetomidine is an alpha-2 agonist with both peripheral and central effects.
Peripheral effects: Vasoconstriction and reflex bradycardia.
Central effects: Reduced sympathetic tone, leading to decreased heart rate, vascular tone, and contractility.

Hypotension in Anesthesia: Summary

Blood pressure is a key indicator of cardiovascular health under general anesthesia.
Maintaining adequate perfusion is critical.
Hypotension is a common complication with associated risks.
Treatment strategies should target the primary cause of hypotension.
Fluid boluses are indicated for volume deficits, but not as preventative measures.
Interventions should be individualized based on patient factors (e.g., age, comorbidities).

Volume Deficits

Patients with dehydration may require fluid boluses in addition to maintenance intravenous fluids (IVF).
Example: 20 kg dog with a 7% free water deficit.
Initial fluid bolus: 20 ml/kg (400 ml) over 10-15 minutes.
Re-evaluate blood pressure and heart rate after the bolus.
Repeat boluses or consider vasopressors if necessary.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

This quiz covers crucial aspects of cardiovascular physiology, including oxygen delivery to tissues and heart rate variations such as bradycardia and tachycardia in dogs and cats. It also discusses the treatment approaches for bradycardia, including the use of anticholinergics. Test your knowledge on cardiovascular health in veterinary medicine.