General Anesthesia Flashcards
General Anesthesia definition
associated with what physical effects?
Three Goals
clinical state of induced loss of consciousness or total insensibility in a reversible manner
associated with DECREASED RESPIRATION and DECREASED BP
Triad - asleep, pain free, still
Ideal Anesthetic agent effects? (6)
unconsciousness amnesia analgesia skeletal muscle relaxation Areflexia good minute-to-minute control
5 Adjuvant or Pre-anesthetic drug classes
anxiety - benzo's allergic rxn prevention - anti-histamine nausea/vomiting - anti-emetics analgesia - opioids prevent bradycardia/secretion - atropine
FOUR Major Consideration prior to anesthesia
FAMILY HX OF MALIGNANT HYPERTHERMIA
CARDIOVASCULAR PROBLEMS
RESPIRATORY DISEASE
MED/FOOD ALLERGIES
4 Phases of General Anesthesia
Induction
Maintenance
Emergence
Recovery
Brain Stages of General Anesthesia
Analgesia
Excitement
Surgical Anesthesia
Medullary Depression
Goal is to pass excitement stage as quickly as possible
Two Major Sub-types of General Anesthetics
Inhalable - gases or vapors - primarily for MAINTENANCE
I.V. or Fixed - primarily for INDUCTION
Three General MOA of General Anesthetics
Induce NEURONAL HYPERPOLARIZATION
Increase FIRING THRESHOLD
Inhibit SYNAPTIC TRANSMISSION and RESPONSE TO NEUROTRANSMITTERS
Factors that determine uptake and distribution of inhaled anesthetic (6)
anesthetic concentration pulmonary ventilation rate solubility pulmonary blood flow arteriovenous concentration gradient Elimination
Anesthetic Concentration in Inspired Air
INCREASE IN CONCENTRATION = INCREASE PARTIAL PRESSURE IN LUNG = FASTER ACCUMULATION OF ANESTHETIC IN BLOOD
Pulmonary Ventilation Rate
Partial pressure of anesthetics WITH HIGHER SOLUBILITY are affected
Increased ALVEOLAR VENTILATION = MORE GAS MOLECULES/TIME = FASTER anesthesia onset
Solubility of anesthetic in blood
Blood gas partition co-efficient - LOWER = LESS SOLUBLE = MORE RAPID RISE in partial pressure in blood = FASTER EQUILIBRATION with brain = FASTER INDUCTION
Solubility of anesthetic in lipid
Brain:blood partition coefficient
MORE LIPID SOLUBLE = MORE POTENCY
Pulmonary Blood Flow and Cardiac Output affects on anesthesia
HIGH BLOOD FLOW = SLOWER ONSET - d/t increased distribution to other tissues
LOW BLOOD FLOW = FASTER ONSET
Elimination affects on anesthesia
LESS SOLUBLE = FASTER ELIMINATION
Minimum alveolar concentration MAC
concentration of anesthetic in inspired air at equilibrium when there is NO RESPONSE TO NOXIOUS STIMULUS
lower MAC = MORE POTENT ANESTHETIC
High lipid solubility = lower mac = MORE POTENT
MAC values are _____
additive WITH INHALED ANESTHETICS
Gaseous Anesthetic
Nitrous Oxide
Volatile Anesthetics (3)
Isoflurane
Desflurane
Sevoflurane
Nitrous Oxide characteristics
Major limitation?
almost ideal
LOW BLOOD/GAS COEFFICIENT
GOOD ANALGESIA
SAFE
INCOMPLETE ANESTHETIC - potency is low - MAC value is 110%
2nd Gas Effect with N2O
REDUCES INDUCTION TIME for primary agent
DECREASES CONCENTRATION REQUIREMENT of primary agent
DECREASES TOXICITY of primary agent
Disadvantages of N2O
LACK OF POTENCY
DIFFUSION HYPOXIA - with abrupt discontinuation
Uses of N2O
CANNOT BE USED AS SOLE ANESTHETIC AGENT
Halothane Characteristics (4)
PROTOTYPE HALOGENATED AGENT
SLOWER RECOVERY
DECREASED CO AND HYPOTENSION
HEPATOTOXIC
Enflurane Important Notes
CNS STIMULATION EFFECTS - convulsive patterns, EEG changes
Isoflurane Important Notes (4)
TYPICALLY USED FOR MAINTENANCE
relatively potent
pungency limits mask induction use
LOWER TOXICITY
Desflurane Important Notes (3)
FASTEST ONSET AND RECOVERY
LOWEST BLOOD/GAS COEFFICIENT = excellent MINUTE-TO-MINUTE CONTROL
LESS POTENT
Sevoflurane Important Notes (4)
Newest
RAPID ONSET AND RECOVERY
VERY POTENT
EXCELLENT CONTROLLABILITY - d/t low solubility/high potency
LOW AIRWAY IRRITATION - suitable for mask induction
Intravenous Anesthetics used primarily for ______
INDUCTION
Thiopental Important Notes (5)
BARBITURATE - CNS DEPRESSANT
one of the most commonly used INDUCTION AGENTS
NOT USED AS SOLE ANESTHETIC
NO ANALGESIA
REDISTRIBUTES TO OTHER TISSUES - fat tissue - CAN ACCUMULATE
Propofol Important Notes (3)
Newer drug
ONE OF THE MOST FREQUENTLY USED IV ANESTHETICS
CONTINUOUS IV DRIP unlike thiopental
EXCELLENT QUALITY OF RECOVERY
Ketamine Important Notes
Contraindicated in?
DISSOCIATIVE ANESTHESIA - intense analgesia, catalepsy, and AMNESIA
EMERGENCE PHENOMENON - unpleasant dreams, hallucinations, disorientation
Contraindicated in patients with PSYCH HISTORY
Midazolam
Clinical uses
good for SEDATION, AMNESIA, ANXIOLYTIC PROPERTIES
sedation for painful procedures
induction agent
substitute for thiopental/propofol in high risk pts
