Lesson 7: RAAS

Lesson 7: Renin-Angiotensin-Aldosterone System (RAAS)

• Essential for cardiovascular homeostasis

• ACE inhibitors (ACEi) and Angiotensin Receptor Blockers (ARBs) manage hypertension

Modulation of the Autonomic Nervous System (ANS) by Anesthetic Agents

• Isoflurane, sevoflurane, desflurane modify ANS affecting consciousness and immobility

• Propofol is the most common IV induction drug, has CNS, respiratory, and cardiovascular depressant effects

• Ketamine, etomidate, midazolam: careful use to avoid side effects

ACE Inhibitors

• Widely prescribed for hypertension, CHF, and LV dysfunction

• Main effects:

  • Decrease angiotensin generation

  • Lower left ventricular afterload

  • Fall in plasma aldosterone levels

  • Increased bradykinin levels cause dry cough

  • Risk of angioedema

  • Profound hypotension risk during anesthesia

Angiotensin Receptor Blockers (ARBs)

• Selective for AT1 receptors, generally fewer side effects than ACE inhibitors

• Similar effectiveness to ACEis for blood pressure moderation and heart failure

• Provide renal protection without the side effect of dry cough

Volatile Anesthetic Agents

• Enhance GABA function, depressive effects on CNS

• Common effects:

  • Decreased BP, CO, CI, SVR

  • Myocardial depression and vasodilation

  • Impacts on respiratory drive and cerebral blood flow regulation

IV Anesthetic Agents

• Propofol: reduces BP, causes bronchodilation, potential hemodynamic instability

• Etomidate: cerebral vasoconstriction, minimal cardiovascular changes

• Ketamine: good cardiovascular stability, analgesic properties, possible side effects like hallucinations

• Midazolam: depresses airway reflexes, reduces BP and SVR

Local Anesthetics

• Interrupt conduction of electrical impulses, provide anesthesia

• Bind to Na+ channels, halting action potential propagation

• Key agents: Lidocaine (Class 1B antiarrhythmic), bupivacaine, ropivacaine

• Unique properties of cocaine: enhances endothelin, inhibits nitric oxide production