A.22 Flashcards
Intravenous anesthetics. Perioperative medication
Propofol,
Etomidate,
Ketamine,
Dexmedetomidine,
-Barbiturates: No analgesia: Thiopental
-Benzodiazepines: Midazolam
-Opiods: Fentanyl,
-Parasympatholytic: Atropine,
-Perioperative medication: Metoclopramide, Antacid drugs, Antihistamines, analgestics
Propofol
MOA: Glycine gated Cl- channels agonist, GABAA agonist→ Cl- influx;
Effect: causes decreased level of conciousness and amnesia;
IND: induction & maintenance of anesthesia, Outpatient anesthesia, Antiemetic effect (treat postoperative vomiting and nausea), a component of TIVA, sedation in mechanically ventilated patients in ICU;
Kinetics: short context-sensitive half-time, high protein binding, short acting (5-10min), rapid onset (30sec) and recovry, hepatic metabolism by conjugation;
SEs: hypotension (potent vasodilator effect), metabolic acidosis (→propofol infusion syndrome- after long application in higher doses it can cause disturbances in lipid metabolism), Pain at injection site, cardiac + respiratory depressant, Overdose can cause death; Extra: Fospropofol- water soluble used in ICU
Etomidate
MOA: GABAA agonist→ Cl- influx;
IND: Only for induction of anesthesia in patients with limited cardiac or respiratory reserve (e.g. hypovolemic patients);
SEs: Pain at injection site, nausea + vomiting, supress normal stress-induced adrenal cortisol for hours (↓cortisol);
Kinetics: short acting, rapid onset, preserves cardiovascular + respiratory stability
Dexmedetomidine
MOA: α2 agonist (at presynaptic neuron, inhibit release of NE);
IND: short term sedation of intubated and ventilated patients in ICU, HTN;
Kinetics: analgestic, sedative/anxiolytic and stress relieving effects, improves perioperative hemodynamic stability;
SEs: bradycardia, hypotension (possible reflex HTN as well due to weak α1 activation in periphery); ContraIND: hypotensive patients
Thiopental
MOA: GABAA agonist→ Cl- influx;
IND: induction of anesthesia, Anesthesia for short surgical procedures;
Kinetics: ultra-short acting, rapid onset (<1min), hepatic metabolism (enzyme inducer), slow recovery due to accumulation in tissues→ long T1/2 (may produce “hangover”);
SEs: hypotension, negative inotropic, peripheral vasodilation, inhibition of baroreflex, Apnea, coughing, ↑HR, cardiac + respiratory depressant, cerebral vasoconstriction (→ ↓cerebral blood flow, volume, ICP)
Midazolam
MOA: GABAA agonist→ Cl- influx;
IND: not real anesthetic (→effect is not narcosis, but deep sleep), preoperative sedation, induction of anesthesia, outpatient anesthesia (e.g. colonoscopy); Kinetics: short acting, slow onset;
SEs: cardiovascular +respiratory depression, antidote- Flumazenil;
Dosage: 0.1-0.2mg/kg i.v
Fentanyl
MOA: synthetic strong μ-OR agonist, analgestic agent; IND: induction and maintenance of anesthesia, management of pain (e.g. cancer patients);
Kinetics: acts as long as it is infused;
SEs: strong CNS depressant, respiratory depression (reversed with naloxone)
Atropine
MOA: strong and effective non-selective M-ACh-R antagonist;
IND: reduces salivation and bronchial secretions before surgery, decreases vagal tone due to administration of inhaled narcotics;
SEs: general anti-M SEs (dry eyes, blurred vision, hallucination, delirium, urinary retention, constipation, decreased secretions);
Dosage: 0.3-1.0mg
Metoclopramide
MOA: DA D2-R antagonist;
IND: anti-emetic effect (high doses required) prevents emesis after anesthesia and chemotherapy-induced emesis, Prokinetic agent (low doses required) → GERD, gastroparesis;
Effect: central effect (→inhibition of D2 receptor in area postrema results in anti-emetic action + anti-nausea), peripheral effect (→↓DA→ ↑ACh release +effect →prokinetic effect mediated by ACh);
SEs: drug induced parkinsonism, extrapyramidal symptoms, hyperprolactinemia, QT prolongation
Antacids
weak bases that neutralize gastric acid by reacting with protons in the lumen of the gut (antacid + water→increasing pH)
Mg(OH)2
Chemistry: Mg(OH)2 + 2HCl → MgCl2 + 2H2O;
Kinetics: slow onset, poorly absorbed from bowel;
SEs: diarrhea (unabsorbed Mg salt), hypermagnesemia (bardycardia, hypotension)
Al(OH)3
Chemistry: Al(OH)3 + 3HCl → AlCl3 + H2O + CO2; Kinetics: slow onset, poorly absorbed from bowel; Effect: protects mucosa→ AlCl3 is a gel-like substance; SEs: constipation, increased Al absorption→ encephalopathy
Antihistamines
GI protective agents: H2R blockers, proton pump inhibitors
Analgestics
pioids (fentanyl, morphine, hydromorphone) + NSAIDs
Outpatient anesthesia
Also known as ambulatory anesthesia, outpatient anesthesia is administered for minor procedures where an overnight stay is not anticipated.
Balanced anesthesia
Combination of different drugs to achieve the goals of surgical anesthesia and decrease the SEs of individual agents. Preoperative- sedation=analgesia, Intraoperative- neuromuscular blocking agents (e.g. I.V propofol / etomidate / thiopental + isoflurane / sevoflurane / desflurane)
TIVA
Total intravenous anesthesia. Hypnosis→ analgesia→ muscle relaxation
Dissociative anesthesia
patient remains conscious but has marked analgesia, amnesia and catatonia (lack of movement and communication)
Context-sensitive half-time
Is the time that required for blood or plasma concentrations of anesthetic agents to decrease by 50% after discontinuation of intravenous anesthetics infusion.
Protein binding: as a general rule, drugs that have low protein binding can penetrate tissue better, while drugs that have high protein binding can stay longer in circulation
