Pharmacology & Anesthesia: IV Anesthesia
Propofol
Basics
- Mechanism: GABA Receptor Agonist
- Timing:
- Onset of Action: 10-60 Seconds
- Duration: 3-10 Minutes
- Advantages:
- Minimal ICP Elevation (Actually Decreases ICP & Intraocular Pressure)
- Rapid Onset
- Antiemetic (Decreased Risk of PONV)
- Antipruritic
- Anticonvulsant
IV Dosing
- Procedural Sedation:
- Bolus: 0.5-1.0 mg/kg
- Repeat 0.25-0.5 mg/kg Every 1-3 Minutes as Needed
- Continuous (ICU) Sedation: 1-60 mcg/kg/min
Side Effects
- Significant Cardiovascular Effects (Bradycardia & Hypotension)
- Respiratory Depression
- Metabolic Acidosis
- Burning Pain with Infusion – Prevent with Lidocaine
- Propofol-Related Infusion Syndrome (PRIS)
- Peripheral & Cardiac Muscle Injury
- Higher Risk at Doses Ove 4-5 mg/kg/hour
- Presentation:
- Metabolic Acidosis
- Refractory Bradycardia & Arrhythmia
- Progressive Myocardial Failure
- Cardiovascular Collapse
- Rhabdomyolysis
- Hyperlipidemia
- Hypertriglyceridemia
- Acute Kidney Injury
- Hepatomegaly
- Monitoring: Daily Creatinine Kinase (CK), Triglyceride Levels or Lactate
- Treatment: Stop Infusion
Possible Contraindications
- Hypersensitivity
- Egg or Soy Allergy
- *Can Cross Placental Barrier but Still Used in Pregnancy (Category B)
Etomidate
Basics
- Mechanism: GABA Receptor Agonist
- Timing:
- Onset of Action: 30-60 Seconds
- Duration: 2-5 Minutes
- Advantages:
- Least Cardiovascular Side Effects
IV Dosing
- Induction: 0.3 mg/kg Over 30-60 Seconds for Induction Only
- For General Anesthesia or RSI
- Not Given by Continuous Infusion
- Procedural Sedation:
- Initial Bolus: 0.1-0.2 mg/kg
- Repeat Dosing: 0.05 mg/kg Every 3-5 Minutes as Needed
Side Effects
- Transient Adrenocortical Suppression if Given by Continuous Infusion
- Injection Site Pain
- Nausea & Vomiting
Possible Contraindications
- Hypersensitivity
Ketamine
Basics
- Mechanism: Noncompetitive NMDA Receptor Antagonist
- Timing:
- Onset of Action: 30 Seconds
- Duration: 5-10 Minutes
- Advantages:
- Provides Analgesia
- No Clinically Significant Respiratory Depression – Appropriate for Extubated Patients Requiring Sedation
IV Dosing
- Acute Agitation:
- Bolus: 1-2 mg/kg Over 30-60 Seconds
- Repeat 0.5-1.0 mg/kg After 5-10 Minutes if Needed
- Procedural Sedation:
- Bolus: 1-2 mg/kg Over 1-2 Minutes
- Repeat 0.5-1.0 mg/kg After 5-10 Minutes if Needed
- Continuous (ICU) Sedation:
- Bolus: 0.1-0.5 mg/kg
- Infusion: 0.2-0.5 mg/kg/Hour
Side Effects
- Catecholamine Release (Tachycardia, Hypertension, Increased Myocardial O2 Consumption)
- Increased Airway Secretions
- Hallucinations – Often Given with a Benzodiazepine to Avoid
- *Historical Dogma of Increased Cerebral Blood Flow/ICP & Contraindication in Head Injury Now Questioned
Possible Contraindications
- Hypersensitivity
- Severe Cardiac Decompensation:
- Myocardial Infarction (MI)
- Unstable Angina
- Space Occupying Lesions of Brain – Debated
Dexmedetomidine (Precedex)
Basics
- Mechanism: CNS Alpha-2 Receptor Agonist
- Timing:
- Onset of Action: 5-10 Minutes
- Duration: 1-2 Hours
- Advantages:
- Provides Some Analgesia
- No Clinically Significant Respiratory Depression – Appropriate for Extubated Patients Requiring Sedation
- Disadvantages:
- Not Appropriate as an Induction Agent
- Does Not Provide Reliable Amnesia
IV Dosing
- Procedural Sedation:
- Bolus: 0.5-1.0 mcg/kg Over 10 Minutes
- Infusion: 0.2-1.0 mcg/kg/Hour
- Continuous (ICU) Sedation:
- Bolus: 0.1-0.5 mg/kg
- Infusion: 0.2-1.5 mcg/kg/Hour (No Clinical Efficacy > 1.5 mcg)
Side Effects
- Hemodynamic Effects:
- Bradycardia or Tachycardia
- Hypotension or Hypertension
- Atrial Fibrillation
- Nausea & Vomiting
Contraindications
- None