Five properties of general analgesia
- 1. Unconsciousness (no response to command)
- 2. Amnesia (no recall)
- 3. Blunting of protective reflexes
- 4. Reduced mm tone
"balanced analgesia" - no one ring to rule them all.
Inhaled anesthetics in B/G order.
Hint: NO DSI En Hell
NO DSI En Hell NO
Des-flurane, Sevo-flurane, Iso-flurane, En-flurane, Halothane
Describe the 4 stages of analgesia
- 1. Analgesia: conscious, increased pain tolerance
- 2. Excitement: disinhibition, unresponsive to command
- 3. Surgical anesthesia: patient is still, unresponsive
- 4. Medullary depression: CV and Resp depression, fatal
Explain why agents with low solubility will produce faster induction and recovery.
- 1. Analgesic effect is determined by the volatility of the gas (partial pressure), its ability to come out of solution into a gaseous form.
- 2. More soluble a compound is, the less volatile it is, less likely it is to come out of solution. Thus the more time it will spend in solution than affecting CNS.
How is adequacy of anesthesia measured?
Partial pressure of the agent in CNS; estimated by exhaled gas (an estimation of alveolar blood, brain).
high B/G (blood gas coefficent) = high solubility = low acting.
High B/G = high solubility = low acting
Define minimum alveolar concentration (MAC)
Alveolar concentration of agent at which 50% of patients do not move. A way to gauge dosage. (Expressed as a percent of atm pressure).
Explain these factors in affecting induction:
1. Solubility of agent
2. Anesthetic concentration
4. Cardiac Output
5. Venous concentration
- 1. See previous
- 2 & 3. Common sense
- 4. High CO, low rise, take agent away much quickly.
- 5. High venous concentration, fast rise, less taken away in the periphery.
Describe the physiologic effects of analgesics in terms of sympathetic tone, CV, respiratory, brain, kidney, and liver.
- Cellular metabolism decreases
- Sympathetic done decreases
- CV- decreases contractility, rate (either way)
- Respiratory - TV decreases, RR increases
- Brain- increase in bloodflow
- Kidney- GFR decreases
- Liver- flow decreases
Describe the manifestation of malignant hyperthermia.
Hypermetabolic response: increased temperature, acidosis, hyperkalemia, hypercarbia
Describes the PK of intravenous anesthetics
Drug effects proportional to concentration. Large doses-> prolonged effects. Rapid increase in concentration-> rapid effects.
Effect of IV anesthetics on cerebral blood flow.
Decreased cerebral blood flow.
One of the most commonly used IV anesthetics and is metabolized by the liver.
This IV anesthetic produces dissociative anesthesia (lack emotional response to pain); what is its effect on cerebral bloodflow?
Ketamine-increases cerebral bloodflow.