Lecture 4 - IV Anesthetics Flashcards Preview

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Flashcards in Lecture 4 - IV Anesthetics Deck (23):
1

Name the IV Anesthetics


what are the three goals of a balanced anesthetic technique?

Propofol

Ketamine

Etomidate

Dexmedetomidine

Benzodiazepines

Barbituates


Balanced technique: Amnesia, Analgesia, Muscle Relaxation. Not acheived By IV anesthetics alone; must use combination of drugs

2

Propofol
- mechanisms
- considerations upon administration of the drug

mechanism: Potentiation of chloride current mediated through the GABA Type A receptor complex; increases this conductance therefore further inhibiting the post synaptic cell and inhibiting AP

Considerations: have to use with sterile technique; Must use within 6 hours after opening; Do not give to persons with egg allergies

3

Propofol
- pharmacokinetics (lipid solubility, metabolism, excretion, redistribution)

Highly lipid soluble
Rapid onset
Rapidly metabolized by the liver
Excreted by the Kidneys
Redistribution -- wake up 8-10 minutes after induction bolus

4

Propofol --
CNS effects
CVD effects
Respiratory effects
GI

CNS -- AMNESIA with NO ANALGESIA properties.
deceased CNS blood flow and metabolic rate
Decreases ICP
Anticonvulsant
Neuro protective

CVD -- Vasodilation; Decreased systemic blood pressure

Respiratory -- Depressant; suppresses upper airway reflexes

Anti-emetic



5

propofol Side effects;

what is propofol Infusion syndrome?

Pain on injection;

Propofol Infusion Syndrome: ---
lactic acidosis via an unclear mechanism
Reversible in early stages

6

propofol Clinical uses:

• Induction of anesthesia --- but NOT ANALGESIA

• Maintenance of anesthesia --- As an infusion , in combination with volatile anesthetics and opioids (balanced anesthesia regimen) or with opioids and benzodiazepines (total intravenous anesthesia technique)

• Sedation -- Repeated boluses and/or intravenous infusion for procedure like endoscopy, MRI, dental extractions etc

7

Ketamine --
mechanism --
Pharmacokinetics (solubility, onset, duration, metabolism, excretion)

Mechanism: Antagonist of the NMDA Receptor (+some direct mu related activity). inhibits the effects of glycine and glutamine; inhibiting the Action potential


lipid soluble, low protein binding
Rapid onset, relatively short duration
Metabolized in the liver to Nor ketamine ( less potent)
Excreted in the urine
Wake up is due to redistribution



8

Ketamine effects:
CNS
CVD
Resp

CNS Effects -- Dissociative Anesthesia, + ANALGESIA, increased Cerebral blood flow and metabolitic rate, can produce seizure like activity (Not used for neurosurgery)

CVD - Sympathetic stimulation; Increased BP, HR, C.

Resp -- No effect on rate; (apnea with rapid infusion); bronchodilator (good for asthmatics); Can increasd salivary and bronchail secretions (therefore given with glycopyrolate)

9

Ketamine --
Primary side effect:
how can this be managed?

Emergency Delerium; Nightmares hallucinations (decreased with benzos)

10

Clinical Uses of ketamine
how is it administered

• Induction of anesthesia:
IV or IM

Maintenance:
Sedation:
Post op pain

11

Etomidate
Mechanism
Pharmacokinetics (BBB penetrance; peak onset; protein binding; metabolism; excretion)

Mechanism of action: (similar to propofol) -- potentiates GABA receptor conductance

Pharamacokinetics -- rapid BBB penetrance; peak onset of 1 minute; 76% bound to albumin; Metabolism by ester hydrolysis; excreted in urine and bile

12

Etomidate effects
- CVD
- resp
- CNS
- endocrine

CVD -- minmial changes in BP, HR; good for patients who are cardiovascularly unstable

Resp -- Minimal depressant effect

CNS - cerebral vasoconstriction; decreased blood flow and metabolic rate

Endo -- Adrenocortical suppression due to 11 beta hydroxylase inhibition

13

Etomidate

best clinical use

• Clinical Uses:
• Induction of anesthesia --- mostly for patients with cardiovascular issues

14

Dexmedetomidine -
Mechanism
Pharmacokinetics

Mechanism: Agonist of Alpha2 receptors in the pons; decreases NE secretion

Pharmacokintics: Water soluble; short term sedation?

15

Dexmedetomidine effects
CNS
CVD
RESP

CNS -- Analgesia, Sedation; no effect on cerebral metabolic rate

CVD -- Depression; brady cardia, hypotension

Resp System -- Minimal depressant effect

16

Dexmedetomidine
clinical use

§ Sedation:
• Short-term sedation of intubated and ventilated patients in the ICU
• Radiological procedures, MRI and interventional radiology


general -- loading dose followed by infusion

17

Benzodiazepines
name them;
Mechanism
Pharmacokinetics
(differences in metabolism)

Midazolam, Diazepam, Lorazepam (Ativan)
Mechanism of action -
Enhance affinity of the GABA receptor for GABA
HOWEVER There is a specific binding site

Pharmacokinetics
§ Highly protein bound to albumin
§ Highly lipid soluble
§ Hepatic metabolism:

Midazolam -- metabolite is inactive
Diazepam -- 2 metabolites are both active; patients have a "hangover" -- not a preferred drug


18

Benzodiazepines
effects

CNS
RESP
CVD

a negative side effect

CNS: Sedation, hypnosis, anterograde amnesia
Anticonvulsant

RESP: minmal resp depression

CVD -- slight decrease in systemic vascular resistsnace and BP

Pain with injeciton with Diazepam (like propofol) ---

19

Benzodiazepines
how is it adminstered
best clinical use ?

Pre-operative Medication --
• Midazolam -- can be given IV, PO, Rectally, Intranasal
• Diezepam -- PO

20

Barbituates

name a few
Mechanism
Pharmacokinetics --

Thiopental, Methohexital

Mechanism: GABA receptor potentiation

Pharmacokinetics -- Metabolized in the liver, excreted in the urine; enhanced effects with alcohol

21

Barbituates

CNS effects - (general effects; which one can activate epileptic foci)
CVD
RESP

CNS effects: Sedation, anesthesia
NO ANALGESIA
↓CBF, ↓ICP,
↓CMRO2 ;
Methohexital activates epileptic foci

Cardiovascular system:
• Peripheral vasodilatation with modest ↓ in BP


Respiratory system:
Respiratory depressant effect: ↓minute ventilation, tidal volume and respiratory rate
↓ventilatory responses to hypercapnia and hypoxia

22

Barbituates

- consideration take when giving bolus through a line? (why?)
a primary side effect
exacerbation of what disease?

Precipitation when mixed with acidic drugs in an IV line, due to its Alkaline pH

• Pain, intense vasoconstriction and gangrene on intra-arterial injection

• Exacerbation of acute intermittent porphyria;

23

Barbituates
clinical uses?

(BUT NOT USED ANYMORE)
Induction of anesthesia:

Neuroprotection:
Treatment of raised intracranial pressure
Treatment of focal cerebral ischemia