Lecture 2/10 Flashcards
The four goals of anesthesia:
“A controlled reversible state of
- Amnesia (w/ loss of consciousness)
- Analgesia
- Akinesia (skeletal muscle relaxation)
- Autonomic and sensory reflex blockade”
Define general anesthesia:
”- State of reversible coma intentionally induced by drugs where the pt is not arousable even with painful stimuli
- requires intervention to support patency of the airway”
What is balanced anesthesia?
“General anesthesia + several agents that can be mix of inhalational and IV meds:
- potent inhalational agent
- nitrous oxide
- neuromuscular blocking agents
- opioids
- benzodiazepines
- IV anesthetics for induction (sedative/hypnotics)”
What is regional anesthesia?
- Basically, the use of local anesthetics to numb a particular region of the body, and it can be supplemented with sedation
What are combined techniques?
- Use of regional anesthesia combined with general anesthesia w/ the goal of using a lower dose of general
What is sedation?
”- Pt remains arousable through use of IV agents for analgesia, anxiolysis, and amnesia
- Surgeon usually provides local anesthesia or a regional block has been done”
What is another term for sedation?
- MAC: Monitored Anesthetic Care
What is ASA I?
- No medical problems
What is ASA II?
- One or more systemic diseases under good control which do not limit function
What is ASA III?
- One or more systemic diseases which are not in perfect control or limit function to some extent
What is ASA IV?
- A systemic condition which is a constant threat to life
What is ASA V?
- Expected to die within a day; surgery is an act of desperation
What is ASA VI?
- Dead patient organ harvesting
What does the E at the end of an ASA status mean?
- Emergency
What are the steps of a generic general anesthesia plan?
”- Anesthesia preoperative eval, consent, and counseling
- IV
- Premedications ( benzodiazepine)
- OR: attach monitors and preoxygenate
- IV induction (combo of IV anesthetics/opioids)
- Neuromuscular Blocking Agent
- Intubation
- Maintenance of anesthetic (combo gas and IV drugs)
- Emergence (reversal agents if necessary)
- Extubation
- Recovery”
What are some reasons for delayed emergence?
”- Normal variation in elimination of antibiotics
- Relative overdose of anesthesia
- Hypoxia, extreme hypercarbia
- Shock/poor perfusion
- Hypoglycemia or other electrolyte disturbances
- Hypothermia
- Increased ICP/Stroke/Air or fat embolism
- Hysteria”
What are the different types of IV anesthetics?
- Sedative-hypnotics, opioids, dissociative anesthetics
What are 4 kinds of IV induction agents?
- Barbiturates, etomidate, propofol, benzodiazepines
What class drug is thiopental?
- Barbiturate
Does thiopental cross the BBB?
- Yes, and rapidly
True or false: thiopental take a long time to take effect
- False, it is short acting, but the elimination half life is several hours
Does thiopental cause apnea?
- Yes
What are some considerations for cerebral perfusion regarding thiopental?
- It reduces CMRO2 (cerebral metabolic rate) and CBF (cerebral blood flow)
What is etomidate?
- Carboxylated imidazole
What are the pros of etomidate?
- Minimal CV effects
What are the cons of etomidate?
”- Might cause adrenocortical suppression
- Myoclonic movements
- Nausea/vomiting”
What’s the most popular induction agent and why?
”- Propofol
- Has the least residual sedation
- It’s easier to store in carts”
What is propofol, and what class of drugs is it similar to?
- Phenol derivative; similar effects to barbiturates but also has anti-emetic effects
What are benzodiazepines used for?
- Anxiolytic/amnestic effects for preop and intraop sedation
What’s the most popular benzodiazepine and why?
”- Midazolam
- Has a short half life
- Water soluble”
What’s the specific antagonist for all benzodiazepines?
- Flumazenil
True of false: Opioids can be used as induction agents at high doses?
- True, due to their CV stability
What are some side effects of opioids?
”- Respiratory depression
- chest wall rigidity
- pruritis
- nausea/vomiting
- urinary retention
- sedation”
What are some common synthetic opioids?
”- Fentanyl
- Sufentanil
- Remifentanil”
What’s a specific antagonist for opioids?
- Naloxone
What’s the difference between fentanyl and morphine?
”- Fentanyl is 100x more potent
- More lipophilic and crosses BBB faster
- More rapid onset and short duration of action”
What is the effect of fentanyl on blood pressure?
- No vasodilation or myocardial depression, no hypotension
What is the effect of morphine on blood pressure?
- Hypotension via the release of histamine
What street drug is ketamine related to?
- PCP
What is ketamine used for?
- Analgesia and dissociation
What are the side effects of ketamine?
- Nightmares (which can be avoided with benzos) and sympathomimetic effects
What are some qualities of an ideal anesthetic gas?
”- low blood solubility
- minimal metabolism
- compatible w/ Epi
- doesn’t irritate the airway
- doesn’t cause myocardial depression”
What is a partition coefficient?
”- Describes blood solubility of inhalational anesthetic
- Distribution ratio between 2 phases at equilibrium”
What is a blood:gas partition coefficient?
- it is the distribution ratio between blood and gas phases because blood is an inactive reservoir for anesthetic
What is the order of blood: gas partition coefficient from least to greatest of the inhalational anesthetics?
Des < N2O < Sevo < Iso < (Hal)
What is the order of anesthetic gas metabolism from greatest to least?
Hal > Sevo > Iso > Des
What is the minimum alveolar concentration?
MAC is the steady state concentration of an inhalational agent that maintains immobility in 50% of subjects exposed to a noxious stimulus
True or false: MAC values are not additive.
False, they are additive
What is a MAC Awake?
0.35 - 0.4 MAC (50% can be awakened)
What level MAC will cause 95% of patients to ignore incisions?
1.5 MAC
What is MAC-BAR?
1.5 - 2 MAC (50% blocked autonomic reflexes at incision)
Which inhalational anesthetics are bronchodilators?
All of them
Which inhalational anesthetics have greater bronchodilatory effects?
Sevo and Hal
Which inhalational anesthetics are the least irritating
Sevo and Hal
What effect do inhalational agents have on TV and RR
- Decreased TV, increased RR (decrease in minute vent)
How do inhalational agents affect MAP
- MAP decreases (dose dependent) but newer agents decrease SVR
How does halothane predispose to ventricular arrhythmias?
- Sensitizes myocardium to catecholamines
What is stage 1 of anesthesia
Analgesia
What is stage 2 of anesthesia
Excitement (delirium)
What is stage 3 of anesthesia
Surgical anesthesia
What is stage 4 of anesthesia
Medullary depression
What factors affect delivery of inhalational agents from machine to alveoli?
”- inspired concentration
- minute vent”
What factors affect delivery of inhalational agents from lungs to blood?
”- Blood: gas partition coefficient
- Cardiac output”
What factors affect delivery of inhalational agents from blood to brain?
”- Brain: blood partition coefficient
- cerebral blood flow”
What is malignant hyperthermia?
”- altered calcium metabolism/membrane physiology
- treated w/ dantrolene”
