Chapter 14  ·  Module 3  ·  Visual Summary

Central Nervous System and Cardiovascular Effects

Cerebral blood flow, intracranial pressure, seizure risk, and cardiovascular profiles of inhalational agents

Central Nervous System Effects

All Volatile Agents

Central Nervous System Effects — Comparative Summary

Agent Cerebral Blood Flow Cerebral Metabolic Rate Intracranial Pressure Seizure Risk
Halothane Increases (most) Decreases Increases (most) None
Isoflurane Increases (modest) Decreases (burst suppression at high dose) Increases (modest; blunted by hyperventilation) None (antiepileptiform at high dose)
Sevoflurane Increases (modest) Decreases Increases (modest) Rare spike activity — not clinically epileptogenic
Desflurane Increases (intermediate) Decreases Increases (intermediate) None
Enflurane Increases Decreases Increases YES — contraindicated in seizure disorders
Nitrous oxide Modest increase Slight increase Modest increase None (mild anticonvulsant)

Key tension: All volatile agents reduce cerebral metabolic rate (protective) but also dilate cerebral vessels (raises intracranial blood volume). Hyperventilation counteracts vasodilation. Propofol does neither — preferred in elevated intracranial pressure states.

Monro-Kellie doctrine: Cranial vault is fixed volume. Brain + cerebrospinal fluid + blood = constant. Any increase in intracranial blood volume raises intracranial pressure when compliance is reduced (mass lesion, edema, hydrocephalus).

Cardiovascular Effects

Cardiovascular Profile

Halothane

  • Blood pressure: myocardial depression (reduces cardiac output)
  • Heart rate: bradycardia (sinoatrial node suppression)
  • Catecholamine sensitization: YES → ventricular arrhythmias with epinephrine
  • Worst tolerated in impaired myocardial function

Cardiovascular Profile

Isoflurane / Sevoflurane

  • Blood pressure: peripheral vasodilation (systemic vascular resistance reduced)
  • Heart rate: maintained or mildly increased (reflex tachycardia)
  • Cardiac output: relatively preserved
  • Catecholamine sensitization: NO
  • Better tolerated than halothane when myocardial function is impaired

Cardiovascular Profile

Desflurane

  • Stable concentrations: similar to isoflurane
  • Rapid increase: sympathetic surge → marked tachycardia and hypertension
  • Avoid rapid increases in coronary artery disease
  • Catecholamine sensitization: NO

Hypoxic pulmonary vasoconstriction: All volatile agents inhibit this reflex → worsens ventilation-perfusion mismatch during one-lung ventilation. Propofol does NOT inhibit hypoxic pulmonary vasoconstriction → preferred for thoracic surgery total intravenous anesthesia.