Introduction to Anesthesia

Definition & Origin

  • Anesthesia = “no sensation” (Greek: an-“without” + aesthesis-“sensation”).
  • Modern use began in 18421842; now a distinct medical specialty focused on patient safety.

Anesthesiology Scope

  • Relief of pain and comprehensive peri-operative care (before, during, after surgery).
  • Anesthetic Care Team: anesthesiologist (physician), nurse anesthetist, other qualified HCPs.

Fundamental Concepts

  • Goal: absence/abolition of sensation while maintaining safety.
  • Anesthetist must master physiology, pharmacology, and monitoring principles.

Areas of Practice

  • Clinical anesthesia: Operating Room, pre-op clinic, Post-Anesthesia Care Unit (PACU), imaging suites, cardiac catheterization lab.
  • Pain management: acute & chronic services.
  • Critical care (ICU) and Emergency Department.

Peri-operative Roles

  • Pre-operative: history, physical exam, risk stratification, choose anesthetic plan.
  • Intra-operative: continuous monitoring (HR, rhythm, respiration, BP, temperature, fluid balance); adjust depth of anesthesia; treat complications.
  • Post-operative (PACU): supervise emergence, ensure stabilization, arrange transfer.

Types of Anesthesia

  • General: reversible loss of consciousness & body-wide sensation.
  • Regional: numbs a larger body region while patient may stay awake (spinal, epidural, peripheral nerve block).
  • Local: numbs a small, specific area; patient conscious.
  • Monitored Anesthesia Care (MAC): conscious sedation with full physiologic monitoring.

General Anesthesia Components

  • Hypnotic → unconsciousness.
  • Analgesia → pain relief.
  • Muscle relaxation → immobility.
  • Amnesia → loss of memory.

Delivery Routes & Principal Agents

  • Inhalational: gases (nitrous oxide) & volatile liquids (halothane, isoflurane, desflurane, sevoflurane). Delivered via facemask, laryngeal mask, or endotracheal tube; anesthesia machine regulates flow.
  • Intravenous: propofol, thiopental, ketamine, midazolam, etomidate. Ideal IV agent = rapid onset, rapid clearance, minimal cardiovascular effects.
  • Balanced/combined techniques and Total Intravenous Anesthesia (TIVA) possible.

Regional & Local Anesthetics

  • Mechanism: reversible peripheral nerve conduction block without CNS depression; patient remains awake.
  • Ester group: cocaine, procaine.
  • Amide group: lidocaine, bupivacaine, ropivacaine.

Ideal Anesthetist Attributes

  • Continuous vigilance: monitors patient, equipment, surgical field simultaneously.
  • Rapid decision-making, communication, teamwork, empathy.
  • Commitment to delivering the safest anesthesia possible.