ANESTHETIC TECHNIQUES USING OPIOIDS1. Sedation and Analgesia - IV boluses of fentanyl = 1-3 µg/kg, Infusion rates 0.01 -0.05 µg/kg/minute - Morphine is slow in onset and does not allow rapidtitration to effect - Meperidine (50–100 mg IV) produces variable degreesof pain relief Plasma opioid concentration (ng/ml) required for total intravenous anesthesia Fentanyl Sufentanil AlfentanilPredominant agent 15–30 5–10 400–800Major surgery 4–10 1–3 200–400Minor surgery 3–6 0.25–1 50–200Spontaneous ventilation 1–3 <0.4 <200Analgesia 1–2 0.2–0.4 50–150
2. Balanced Anesthesia - reduce preoperative pain and anxiety, decreasesomatic and autonomic responses to airway manipulations,improve hemodynamic stability, lower requirements for inhaledanesthetics, and provide immediate postoperative analgesia• Choice of Opioid - ideal opioid rapid titration, prevent unwantedresponses to noxious stimuli, require little supplementation,not depress cardiovascular function, permit the return ofadequate spontaneous ventilation in a timely manner,postoperative analgesia with minimal side effects
3. Total Intravenous Anesthesia - doses for total intravenous anesthesia Loading Dose Maintenance Additional (µg/kg) Infusion Rate BolusesFentanyl 4–20 2–10 µg/kg/hr 25–100 µg - Midazolam-opioid combinations provide completeanesthesia4. Opioid-Based (High-Dose Opioid) Anesthesia - \"stress-free\" anesthetic method for cardiac surgery - plasma fentanyl concentrations (10–30 ng/mL) providestable hemodynamics throughout the induction/intubationrange f-rCoomnt0i.n1utoous1.i0nfµugs/kiogn/ms ionfutfeentanyl for cardiac surgery(25–50-µfgo/krgp) ecodmiabtrinicedhewairtth sisuorfgleurryan(5e0(–01.20%0 –µ0g./4kg%) )or fentanyl
5. Other Applications of Opioids - Transdermal Drug Delivery - Transmucosal Drug Delivery - Oral Controlled-Release MedicationsDosing data for agonist-antagonist opioids and morphine Equianalgesic Duration of Oral: IM IM Dose (mg) Analgesia (hr) Efficacy RatioMorphine 10 4–5 1:6Buprenorphine 0.3–0.4 >6 1:2Butorphanol 2 3–4 —Nalbuphine 10 3–6 1:4–5Pentazocine 40 3 1:3
OTHER OPIOID AGONISTS1. Codeine (methylmorphine) - half as potent as morphine - high oral-parenteral potency ratio (2:3) - plasma half-life of 2 to 3 hours - mild - moderate analgesic - strong cough-suppressant - Intravenous codeine produces profound hypotension2. Heroin (diacetylmorphine) - twice as potent as morphine - 4- 5-hour duration of action
3. Methadone - equivalent potency but longer duration of action thanmorphine - prevention of opioid withdrawal symptoms, treatmentof chronic pain. - plasma half-life very long and variable ( 13-100hrs). - require dosing every 4-8 hrs to maintain analgesiceffects4. Tramadol (synthetic 4-phenyl-piperidine analog of codeine) - one fifth to one tenth as potent as morphine - less respiratory depression non-opioid receptor-mediated actions - minimal effects on GI motor function - adverse effect; Seizures
5. Pentazocine - κ-receptor stimulation - one half to one fourth as potent as morphine - prolonged use of pentazocine can lead to physicaldependence - inhibits gastric emptying - postoperative nausea and vomiting6. Nalbuphine - antagonist at μ-receptor - agonist at κ- and δ-receptors - onset 5-10 mins, long duration (3-6 hrs) long plasmaelimination half-life (5 hrs) - Conscious sedation during MAC recommended with acmogm/kbgi)nation of nalbuphine (0.05–0.2 mg/kg) and midazolam (0.05titrate-dRedsotsoersatoifonnaolfbuspphoinntean(2e.o5ums gveInVtielavteiroyn 2ustinog3smmianlul tes)results in less pain than naloxone (0.08 mg IV every 2 to 3minutes)
Respiratory depressant effects of agonist- antagonists compared with morphineDrug Correlation of Respiratory Depression with DoseMorphine Increases proportionally with doseBuprenorphine Ceiling effect at 0.15–1.2 mg in adultsButorphanol Ceiling effect at 30–60 µg • kg-1Nalbuphine Ceiling effect at 30 mg in adultsPentazocine Ceiling effect suggested (30-70mg), but difficult to study because of psychotomimetic effects
Hemodynamic effects of agonist-antagonist compounds compared with morphineDrug Cardiac Workload BP HR PAP ↓ =↓ =↓Morphine ↓ ↓ ↓? =↑ =↑Buprenorphine ↓ = =↓ = ↑ ↑↑Butorphanol ↑Nalbuphine ↓Pentazocine ↑
Naloxone - opioid antagonists - reduce or reverse opioid-induced nausea and vomiting,pruritus, urinary retention, rigidity, biliary spasm - side effects; increases HR,BP - complications; pulmonary edema - Reversal of Respiratory Depression - dose ranged from 0.4-0.8 mg IV or intratracheal - Most often, 1.0–2.0 µg/kg titrated in boluses of 0.5–1.0µg/kg every 2 to 3 minutes will restore adequate spontaneousventilation - rapid onset (1-2 mins), short half-life and duration ~30-60 minsof nalo-x\"Roneenatrocorteivzeartsioenl\"ooncgceurr-ascmtionrgeofprieoiqdusently after the use - treatment of postanesthetic apnea in infants
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