105 terms

Anesthesia

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Physiological parameters used to assess readiness for extubation?
- RR>8 & <30/min
- TV>5 cc/kg
- TV/RR>10
- PaO2 > 65-70 mmHg on FiO2<40%
- PaCO2 < 50mmHg
- Hemodynamic Stability
- Temp at least 35C
- NIF > -20
Volatile anesthetics are all bronchodilators except...?
Desflurane

- Irritating and may cause bronchospasm
Administered alone (ie, without narcotics), inhaled anesthetics have what affect on RR and TV?
RR Increases
TV decreases
Inhaled anesthetics are not metabolized by the body and are eliminated by ventilation, except...?
Halothane
All volatile anesthetics are capable of triggering malignant hyperthermia except...?
Nitrous Oxide
What to use for induction in Peds cases in which the child may not tolerate IV?
Volatile Anesthetics
Pros of Halothane
Cheap, nonirritating so can be used for inhalation induction
Cons of Halothane
Long time to onset/offset

Significant Myocardial Depression

Sensitizes myocardium to catecholamines

Association with Hepatitis
Pros of Isoflurane
Cheap, excellent renal, hepatic, coronary, and cerebral blood flow persevation
Cons of Isoflurane
Long time to onset/offset

Irritating so cannot be used for inhalation induction
Pros of Desflurane
Extremely rapid onset/offset
Cons of Desflurane
Expensive

Stimulates Catecholamine release

Possibly increases PONV

Requires special active-temperature controlled vaporizer due to high vapor pressure

Irritating so cannot be used for inhalation induction
Pros of Sevoflurane
Nonirritating so can be used for inhalation induction

Extremely rapid onset/offset
Cons of Sevoflurane
Expensive

Due to risk of "compound A" exposure is better to be used at flows > 2 L/min

Theoretical potential for renal toxicity for inorganic fluroide metabolites
Pros of Nitrous Oxide
Decreases volatile anesthetic requirement

Dirt Cheap

Less myocardial depression than volatile agents
Cons of Nitrous oxide
Diffuses freely into gas filled spaces (bowel, pneumothorax, middle ear, eye)

Decreases FiO2

Increases pulmonary vascular resistance
MOA of most Sedative Hynotics
Inhibitory GABA system in which increased chloride conductance leads to neuronal inhibition
Most IV induction agents bind to a specific site called "?? 1 ??" for their inhibitory effect, and they have a rapid onset due to "?? 2 ??" properties which allow them to quickly partition into the highly perfused brain and spinal cord.
1. GABAa

2.Lipophilic
IV anesthetics have a (short/long) duration of action?
Short

With their termination of effect due redistribution into less perfused tissues such as muscle and fat
What drugs are preferred for neurosurgery cases?
Barbiturates (eg, thiopental)

Decrease ICP by a decrease in cerebral oxygen consumption. Since cerebral perfusion is preserved, a desirable drug for neurosurgery.
Pros of Barbiturates (eg, thiopental)
Excellent brain protection

Stops Seizures

Cheap
Cons of Barbiturates (eg, thiopental)
Myocardial depression

Vasodilation

Histamine release

Can precipitate porphyria
Induction dose and maintenance dose of Propofol?
1.5 to 2.5 mg/kg while continuous infusion of 100 to 200 micrograms/kg/min maintains unconsciousness

Values differ for children and elderly
Pros of Propofol
Prevents nausea/vomiting

Quick recovery if used as solo anesthetic agent
Cons of Propofol
Pain on injection

Expensive

Supports bacterial growth

Myocardial depression (the most of the four)

Vasodilation

Cross reactivity with egg allergy
The ideal IV anesthetic for patients with CVD or hemodynamic instability?
Etomidate

minimal depression on CV and pulmonary function
Induction dose of Etomidate?
0.2 to 0.4 mg/kg (adults)

Causes pain on induction and myoclonus
Etomidate may prevent "?" synthesis
Cortisol
Pros of Etomidate
Least myocardial effect of IV anesthetics
Cons of Etomidate
Pain on injection

Adrenal suppression

Myoclonus

N/V
Ketamine MOA
Antagonism of the NMDA receptor channel complex
Induction dose of Ketamine?
1-2 mg/kg

Minimally depress cardiorespiratory system
How does Ketamine affect the autonomic nervous system?
Directly stimulates SNS and increases BP and heart rate

- Increasing demand on the heart is not a good choice for CAD patients
Good anesthetic choice for uncooperative patient without IV
Ketamine

- works IV, PO, PR, IM
Good anesthetic choice for hypovolemic trauma
Ketamine

- Stimulation of SNS. Often preserves airway reflexes
Pros of Ketamine
Works IV, PO, PR, IM

Stimulation of SNS (hypovolemia)
Cons of Ketamine
Dissociative anesthesia with postop dysphoria and hallucinations (decrease effects in PACU with midazolam)

Increases ICP/IOP and CMR02

Stimulation of SNS - bad with pts with compromised cardiac function, increases airway secretions
MOA of dexmedetomidine?
Selective alpha-2 adrenergic agonist - depresses central sympathetic function (sympatholytic) and produces sedation and analgesia.
Uses for Dexmedetomidine?
Used in OR for adjunct to general anesthesia

Sedation for awake fiberoptic intubation
Dosing for Dexmedetomidine
Generally given as a loading dose of 0.5-1 mcg/kg over 10 minutes, followed by an infusion of 02-0.7 mcg/kg/hr.
How does Dexmedetomidine affect respiratory?
No respiratory depression
Induction dose & Infusion rates of Midazolam (Versed)
Induction dose of 0.1-0.2 mg/kg

Infusion rates of 0.25-1 mcg/kg/min
(Drug Class?) produce respiratory, cardiovascular, and upper airway reflex depression and in the presence of hypovolemia, may cause significant hypotension
Benzodiazepines
Metabolite of Esters (eg, Procaine, Tetracaine, Chlorprocaine)?
PABA

Can cause allergic reactions
Amides are metabolized by...?
Hepatic enzymes
Amides have how many I's
At least two "i"s in their name, eg, Lidocaine, Ropivicaine, Bupivicaine
(Drug) depresses breathing principally by impairing the medullary response to CO2
Morphine

Also trigger the CTZ which may lead to nausea, and may in turn stimulate the vomiting center
How does Morphine affect GI, Urinary system, granular cells?
Decreases GI motility and propulsion

Urinary retention

Releases histamine by stimulating basophils in the lungs and mast cells in the skin
How does morphine affect the CVS?
Vascular dilation

Decrease SVR

Hypotension
How is morphine eliminated?
Long acting and renally excreted.

- active metabolite has opiate properties, therefore beware in renal failure
Demerol stimulates catecholamine release so beware in patients using...?
MAOIs
Potential effect of using Demerol with renal failure
Renally active metabolite associated with seizure activity
Most powerful?

Fentanyl/Alfentanil/Sufentanil/Remifentanil
Sufentanil (1000x morphine)
Shortest acting?

Fentanyl/Alfentanil/Sufentanil/Remifentanil
Remifentanil
Safe alternative in patients with morphine allergy?
Fentanyl/Alfentanil/Sufentanil/Remifentanil

But higher chance of chest wall rigidity
Depolarizing muscle relaxant
Succinylcholine
Cons of Succinylcholine
Increased ICP/IOP

Fasciculations and postop muscle aches

MH

Increased postassium (beware of pts with burns, crush injury, spinal cord injury, muscular dystrophy, or disuse syndromes)
(Nondepolarizing muscle relaxant) has slow onset, long duration, and tachycardia due to vagolytic effect
Pancuronium
(Nondepolarizing muscle relaxant) has slow onset, intermediate duration, hoffman (nonenzymatic) elimination so attractive choice in liver/renal disease
Cisatracurium
(Nondepolarizing muscle relaxant) has the fastest onset making it useful for rapid sequence intubation, intermediate duration
Rocuronium
Cholinergic Crisis (SLUD CB2)
Salivation
Lacrimation
Urination
Diarrhea
Ciliary constriction (miosis)
Bronchospasm
Bradycardia
(Reversal agent) shares duration of action with gylcopyrrolate
Neostigmine

Used in conjunction with Glycopyrrolate
(Reversal agent) shares duration of action with atropine
Edrophonium

Some use atropine as premed for all children since they tend to become bradycardic with intubation and produce copious drool
(Reversal agent) crosses the BBB, therefore useful for atropine overdose
Physostigmine
Given with reversal agents to block the muscarinic effects of cholinergic stimulation, also excellent for treating bradycardia and excess secretions
Anticholinergics (eg, Atropine, glycopyrrolate)
Central Anticholinergic Syndrome
Blind as a bat (blurred vision)
Red as a beet (Flushing)
Dry as a bone (Anhydrosis)
Fast as a hare (Tachycardia)
Mad as a hatter (Delerium)
Major advantages of Nitrous Oxide
No odor
Fast induction and recovery
Minimal cardioresp depression
Good analgesic
Primary use of Nitrous oxide
Minor surgery
Used in combination with GAnesthetics for GA
Toxicity/Concerns with Nitrous Oxide
Acute - N/V
Chronic - B12 deficiency
Major advantages of Halothane
Pleasant odor
Slower induction and recovery
Primary use of Halothane?
Most widely used peds anesthetic world wide.

Asthma pts (no bronchoconstriction)
Toxicity/Concerns Halothane
Slow induction/recovery

Sensitizes mycocardium to catecholamines (Vent arrhythmias)

Hepatotoxicity
Major advantages of Enflurane
Pleasant odor
Less S.E. than Halothane
Primary use of Enflurane
Adults
Toxicity/Concerns: Enflurane
Hypotension
Seizures @ high [ ]
Nephrotoxicity
Major advantages of Isoflurane
Stable Cardiac rhythm
Rapid onset/recovery
Minimal metabolism (low tox potential)
Excellent muscle relaxant
Primary use of Isoflurane
Most widely used anesthetic in adults
Toxicity/Concerns: Isoflurane
Pungent odor (not for kids)
Broncho-irritant
Major advantages of Desflurane
Rapid onset/recovery
High potency (least Soluble)
Even less metabolism
Primary use of Desflurane
Ambulatory surgery (for rapid recovery)
Toxicity/Concerns: Desflurane
Very pungent
Irritating to airways
LARYNGOSPASM
Expensive
Major advantages of Sevoflurane
Fast induction/recovery
High potency (least soluble)
Non-irritating vapor
Primary use of Sevoflurane
Outpatient anesthesia
Inhalation Induction (especially children)
Toxicity/Concerns: Methoxyflurane
Renal toxicity
List the volatile anesthetics from Fastest to slowest, Lowest to Highest potency, and High to low MAC
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Nitrous oxide
Desflurane
Sevoflurane
Enflurane
Isoflurane
Halothane
Methylfurane
Onset/Elimination/Pharmacokinetics of Barbiturates (Thiopental, Methohexital, Thiamylal)
Onset: 30-40sec

Elimination: 10-12 hrs (thiopental), 3-6 hrs (Methohexital)

Pharmacokinetics: Redistribution
Advantages of Barbiturates (eg, Thiopental, Methohexital, Thiamylal)
Rapid onset, Fast recovery

Anesthesia for short procedures
Disadvantages of Barbiturates (eg, Thiopental, Methohexital, Thiamylal)
No analgesia

Alkaline/Tissue irritant

Resp & CV depression

Low TI OD risk
Onset/Elimination/Pharmacokinetics of Benzos (eg, Diazepam, Midazolam, Lorazepam)
Onset: 3-5 min

Elimination: 20-40h (diazepam), 2-6h

Pharmacokinetics: Demethelated in the Liver (prolonged t1/2 with cirrhosis, etc)
Advantages of Benzos (eg, Diazepam, Midazolam, Lorazepam)
Relative rapid onset

Minimal Resp and CV depression
Disadvantages of Benzos
Not a good analgesic
Used for radiologic procedures in children
Ketamine
(Anesthetic) prevents N/V
Etomidate, Propofol
Disadvantages of Etomidate/Propofol
Hypotension
CV depression
Mechanical ventilation
Discoloration of urine (green)
Maintenance IV fluids
4, 2, 1 rule, or kg +40 in anyone over 20 kg

Give 1 eqv per hour
Deficit IV fluids
Hours NPO x Maintence

1/2 = 1/4 = 1/4 = -
Insensible loss IV fluid
3-15 cc/hr : Case dependent
Estimated blood loss IV Fluids
1:1 Colloid
3:1 Crystalloid
Allowable blood loss calculation
ABL= [BV x (Hcti-Hctf)]/Hcti

- BV men = 60 cc/kg
- BV women = 50 cc/kg
- BV Neonate = 90 cc/kg
- BV infants = 80 cc/kg
ASA 1-6
1. healthy patient
2. mild sys disease, no impact on daily activity
3. sev. sys disease, limits normal activity
4. sev sys disease constant threat to life (ex. unstable angina, symptomatic CHF, MI or CVA within last 6 months, combination of cardiac and renal disease)
5. moribund - likely to die next 24h w/o surgery
6. brain dead organ donor
Mallampati classification
1 -> visible tonsillar pillars, fauces, uvula, soft and hard palate
2 -> visible uvula (except tip), fauces, soft and hard palate
3 -> visible soft and hard palate and base of uvula
4 -> visible hard palate only
Post MI surgery risk
Perioperative MI mortality 20-50%
If no prior MI, risk is 0.13%
Occur 48-72 hr postop
No sx for 6 months (risk reduces to 5-6%)
Cardiac contraindication to surgery
MI <1 month
Uncompensated CHF
Severe AS or MS
Most sensitive finding of Malignant Hyperthermia
ETCO2

(pts also have coca-cola urine)
Confirm diagnosis of Malignant hypothermia?
Large difference between venous CO2 and arterial CO2