CH 4. General Anesthsia

4.1 History and Contemporary Use

Pros and cons of injected vs inhaled anesthetics

  • Injected: Acts quick, but hard to determine dosage

  • Inhaled: easier to control level of anesthesia but long time to reach 3rd stage (surgical anesthesia)

Goal: tune out all sensation for patient

Purpose: used in detailed surgical procedures

Requirements for General Anesthesia

  • Safe, Transient, and Predictable

  • Unconscious, amnesia, inhibit reflexes and skeletal muscle

Stages of General Anesthesia

  • Analgesic

  • excitement (move thru fast)

  • surgical anesthesia

  • medullary paralysis (Too much = bad)

PROTOCOL

  • Start with small dose of injected

  • swap to inhaled from sleep to end of procedure

  • stop inhaled ASAP

Balanced Anesthesia

  • combination of injected, inhaled, and other drugs for patients; 2 or MORE

4.2 Mechanism of Action & Clinical Implications

What is mechanism of anesthetic on brain for unconsciousness

  • bind to receptors to increase inhibition effects or decrease excitation

Purpose of adjuvant drugs for patient comfort before and after anesthesia

  • increase sedation and reduce nausea

Clinical implications for patients recovering from general anesthesia in PT

  • mindful of muscle soreness and cognitive deficits

Mechanism of anesthetics

  • alter lipid bilayer AND/OR

  • alter receptors of neurotransmitters (GABA)

    • increase inhibition (GABA)

    • decrease excitation (Opioid)

Adjuvants Purpose

  • relax patients before surgery

  • reduce nausea, vomiting

Neuromuscular Junction Blockers

  • Paralyze muscles to prevent complication

  • why use NMJ blockers instead of higher dose of general anesthesia? —> using too much anesthesia is not safe so NMJ blockers help to reduce dose

  • why as PT we need to know about pt on NMJ —> cause post op soreness (succinylcholine)

  • Rare case unable to metabolize and remain paralyzed

    • Cholinesterase inhibitor (increase acetylcholine)

    • Sugammadex (inactivate drug)

Dissociative Anesthesia

  • Patient looks awake but dissociated

  • Drugs: Ketamine OR Antipsychotic + Opioid

  • Emergency surgeries, dressing change, diagnostic procedure (colonscopy)

Post-OP effects of anesthesia

  • Co-morbidities (heart failure, Parkinson’s, Alzheimers) can get worse with anesthesia