1 / 57

Intravenous Anesthesia

Intravenous Anesthesia. Prof. Ahmed Elsaied. What is Anesthesia?. Sensory Absence of intraoperative pain Cognitive: Absence of intraoperative awareness Absence of recall of intraoperative events Motor: Absence of movement Adequate muscular relaxation Autonomic:

wrouse
Download Presentation

Intravenous Anesthesia

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Intravenous Anesthesia Prof. Ahmed Elsaied

  2. What is Anesthesia? • Sensory • Absence of intraoperative pain • Cognitive: • Absence of intraoperative awareness • Absence of recall of intraoperative events • Motor: • Absence of movement • Adequate muscular relaxation • Autonomic: • Absence of hemodynamic response • Absence of tearing, flushing, sweating

  3. What is Balanced Anesthesia? • Use specific drugs for each component • Sensory • N20, opioids, ketamine for analgesia • Cognitive: • Produce amnesia, and preferably unconsciousness, with N2O, .25-.5 MAC of an inhaled agent, or an IV hypnotic (propofol, midazolam, diazepam, thiopental) • Motor: • Muscle relaxants as needed • Autonomic: • If sensory and cognitive components are adequate, usually no additional medication will be needed for autonomic stability. If some is needed, often a beta blocker +/- vasodilator is used.

  4. What is Balanced Anesthesia? • Garbage Anesthesia (everything but the kitchen sink) • LOT2 (Little Of This, Little of That) • Mixed Technique • The Usual

  5. MAC Reduction Lang et al, Anesthesiology 85, 721-728, 1996

  6. Bolus Dose Equivalents • Fentanyl 100 mg (1.5 mg/kg) • Remifentanil 35 mg (0.5 mg/kg) • Alfentanil 500 mg (7 mg/kg) • Sufentanil 12 mg (0.2 mg/kg)

  7. What is the role of N2O? • Excellent analgesic in sub-MAC doses • MAC is around 110%. • MACasleep tends to be about 60% of MAC. • MACasleep for N2O is 68-73% • Well tolerated by most patients. • At N2O concentrations of 70%, there may be no need for additional drugs to ensure lack of awareness. • Has the fastest elimination of any hypnotic agent used in anesthesia. • If you want your patients to wake up quickly, keep them within N2O of being awake!

  8. Simple Combinations • Morphine • 10 mg iv 3-5 minutes prior to induction • Additional 5 mg 45 minutes before the end of the procedure, if it lasts longer than 2 hours • Propofol • 2-3 mg/kg on induction • N2O • 70% • Sevoflurane • 0.3-0.6% • Relaxant of choice

  9. Simple Combinations • Fentanyl • 75-150 on induction • 25-50 mg now and then during the case • Propofol • 2-3 mg/kg on induction • N2O • 70% • Sevoflurane • 0.3-0.6% • Relaxant of choice

  10. Setting up drug infusions • Check out your infusion pump as thoroughly as you check out your anesthesia machine. • Is your drug dilution correct? • Is the syringe adequately held? • Is the syringe plunger properly held in the clamp? • Are your infusion units correct? • Is the weight correct (for calculator pumps)? • Has the dead space been taken out of the line? • Have the batteries been checked? • Think of the check out as though you were going to infuse sodium nitroprusside.

  11. Setting up drug infusions • Always infuse drug through a t-piece connected at the IV catheter site. • Typical IV tubing contains 5-8 mls of dead space between injection ports and catheter. • Connecting the infusion at the convenient injection port may result in patients receiving 5-8 mls of remifentanil if the IV rate is increased or other drugs are flushed through the line. • After an unintentional bolus there will be a period of no drug administration while the tubing again fills with remifentanil.

  12. 50% Effect Site Decrement Time

  13. 20% Effect Site Decrement Time

  14. 80% Effect Site Decrement Time

  15. Continuous Infusions: Propofol • 2-3 mg/kg bolus on induction • Relaxant of choice • Titrate propofol infusion from 75-140 mg/kg/min during case • In last 45 minutes, stay from 50-100 mg/kg/min • N2O 70% • Crack open vaporizor as needed for BP control

  16. Propofol Induction 100 90 80 Dose as fraction of dose in a 20 year old 70 60 50 20 40 60 80 Age

  17. Propofol/opioid vs Isoflurane/opioid

  18. Propofol/opioid vs Isoflurane/opioid

  19. Continuous Infusions:Fentanyl • Initial Bolus: 150 mg • Infusion 1: 2 mg/min for 6 hours • Infusion 2: 1 mg/min • End: 90 minutes prior to anticipated extubation

  20. Continuous Infusions:Alfentanil • Initial Bolus: 1000 mg • Infusion: 50 mg/min • End: 45 minutes prior to anticipated extubation

  21. Continuous Infusions:Sufentanil • Initial Bolus: 16 mg • Infusion 1: 1 mg/min for 6 hours • Infusion 2: 0.5 mg/min • End: 30 minutes prior to anticipated extubation

  22. Observations • Of these, sufentanil works the best, fentanyl works the poorest • Fentanyl accumulates the most, which can be a problem with continuous infusions • Must remain vigilant for signs of light anesthesia • Change in heart rate is often the first sign. • If the patient is light, give a 2-3 cc bolus of propofol

  23. Remifentanil vs. other opioids 100 remifentanil • Rapid rise to steady state 80 60 alfentanil Percent of steady-state effect site opioid concentration 40 sufentanil 20 fentanyl 0 0 10 20 30 40 50 60 Minutes since beginning of continuous infusion Shafer SL, ASA Refresher Course, Chapter 19, 1996

  24. Remifentanil vs. other opioids 100 10 Percent of peak plasma opioid concentration fentanyl 1 sufentanil alfentanil remifentanil 0.1 360 480 600 240 0 120 Minutes since bolus injection Minto et al, Anesthesiology, in press

  25. Remifentanil vs. other opioids 100 sufentanil 80 fentanyl 60 Percent of peak effect site opioid concentration 40 alfentanil 20 remifentanil 0 4 6 8 10 0 2 Minutes since bolus injection Minto et al, Anesthesiology, in press

  26. Remifentanil vs. other opioids • Recovery from remifentanil is unlike that seen with any other opioid • The time to a given decrease in effect site concentration is constant over time • no accumulation 60 fentanyl 40 20% decrease alfentanil 20 sufentanil 0 remifentanil 120 fentanyl 90 alfentanil Minutes required for a given percent decrease in effect site concentration 60 50% decrease sufentanil 30 remifentanil 0 300 fentanyl 240 alfentanil 180 80% decrease 120 sufentanil 60 remifentanil 0 0 120 240 360 480 600 Minutes since beginning of infusion Shafer SL, ASA Refresher Course, Chapter 19, 1996

  27. 20% effect sitedecrement curves 60 fentanyl 40 Minutes required alfentanil 20 sufentanil remifentanil 0 240 360 480 600 0 120 Minutes since beginning of infusion Shafer SL, ASA Refresher Course, Chapter 19, 1996

  28. 50% effect sitedecrement curves Minutes required Minutes since beginning of infusion Shafer SL, ASA Refresher Course, Chapter 19, 1996

  29. 80% effect sitedecrement curves Minutes required Minutes since beginning of infusion Shafer SL, ASA Refresher Course, Chapter 19, 1996

  30. 6 5 4 3 2 1 0 Remifentanil/Propofol Induction g/ml) m Target Propofol Concentration ( 0 5 10 15 20 25 30 35 40 Remifentanil Concentration (ng/ml) S=success (no response to skin incision) F=failure (response to skin incision) Fragen et al, data on file with Glaxo Pharmaceuticals

  31. 25 1.0 mg/kg/min 20 15 Remifentanil concentration (ng/ml) 0.5 mg/kg/min 10 Rigidity Apnea 5 Ventilatory Depression 1.0 mg/kg 0 6 8 10 0 2 4 Minutes

  32. Induction Technique:Remifentanil 1.0 mg/kg/min 25 • Hypnotic and relaxant 30-90 seconds prior to starting remifentanil infusion. • Intubate 90-120 seconds after starting remifentanil infusion. • Decrease infusion rate after intubation. 1.0 m g/kg/min 20 15 Remifentanil concentration (ng/ml) Intubate { 10 Rigidity Relaxant { Apnea 5 Hypnotic { Ventilatory Depression 0 -2 0 2 4 6 8 10 Minutes

  33. Induction Technique:Remifentanil 1.0 mg/kg bolus • Hypnotic and relaxant just before remifentanil bolus. • Intubate 60-90 seconds after remifentanil bolus. • Suitable for rapid sequence. 25 20 15 Remifentanil concentration (ng/ml) Intubate { 10 Rigidity Relaxant { Apnea 5 Hypnotic { Ventilatory Depression 1.0 m g/kg 0 -2 0 2 4 6 8 10 Minutes

  34. Induction Technique:Remifentanil 0.5 mg/kg/min • Start remifentanil infusion. • Give hypnotic 30-90 seconds after starting infusion, followed by relaxant • Slower, gentler technique. 25 20 15 Remifentanil concentration (ng/ml) 0.5 m g/kg/min Intubate 10 { Rigidity Relaxant { Apnea 5 Hypnotic { Ventilatory Depression 0 -2 0 2 4 6 8 10 Minutes

  35. Maintenance Infusion Rates • 1.0 mg/kg/min • Profound analgesia • 0.5 mg/kg/min • Paralysis required • 0.25 mg/kg/min • Ventilation required • > 50% MAC reduction • 0.1 mg/kg/min • May be satisfactoryfor spontaneous ventilation

  36. Potential Risk:Infusion interruption • Reports of nearly catastrophic events associated with abrupt termination of remifentanil infusions. • Few other drugs in anesthesia where so little time exists between infusion interruption and severe complications. • Need to have an alternative plan ready: • Propofol bolus • Turn on / turn up inhalational anesthetic • Fentanyl bolus • Need to have next syringe made up and ready to go. • Spending 2 minutes changing syringe might be too long during light anesthetics

  37. Propofol/Alfentanil Interaction 400 • Adapted from Vuyk et al, Anesthesiology 83:8-22, 1995 • Characterizes the concentrations for • intubation • maintenance • on emergence • Concentrations are 50% response level Intubation 300 Maintenance 200 Alfentanil Concentration (ng/ml) Emergence 100 0 0 2 4 6 8 10 Propofol Concentration (mg/ml)

  38. Opioid/Hypnotic Interactions • Vuyk, et al: Pharmacodynamic Interaction of Propofol and Alfentanil • Anesthesiology 83:8-22, 1995 • Stanski and Shafer: Quantifying Anesthetic Drug Interaction: Implications for Drug Dosing • Anesthesiology 83:1-5, 1995

  39. “Optimal” Propofol/Alfentanil • Infusion rates for propofol and alfentanil • Propofol levels during maintenance and at emergence from anesthesia • Alfentanil concentrations during maintenance and at emergence • Time from ending the infusion to awakening from anesthesia • The percent decrease in concentration required for emergence from anesthesia Stanski and Shafer: Anesthesiology 83:1-5, 1995

  40. Propofol/Opioid Technique Stanski and Shafer: Anesthesiology 83:1-5, 1995 Shafer SL, ASA Refresher Course, Chapter 19, 1996

  41. Propofol/OpioidTime to Awakening Alfentanil Technique Remifentanil Technique 20 15 10 5 0 0 120 240 360 480 600 120 240 360 480 600 Time (Minutes) Time (Minutes) Shafer SL, ASA Refresher Course, Chapter 19, 1996

  42. Propofol/OpioidInfusion rates Alfentanil Technique Remifentanil Technique 400 300 Remifentanil (ng/kg/min) Alfentanil (ng/kg/min) 200 Propofol (mg/kg/min) 100 Propofol (mg/kg/min) 0 0 120 240 360 480 600 120 240 360 480 600 Time (Minutes) Time (Minutes) Shafer SL, ASA Refresher Course, Chapter 19, 1996

  43. Propofol/OpioidPropofol Levels (mg/ml) Alfentanil Technique Remifentanil Technique 6 4 Maintenance Maintenance 2 Emergence Emergence 0 0 120 240 360 480 600 120 240 360 480 600 Time (Minutes) Time (Minutes) Shafer SL, ASA Refresher Course, Chapter 19, 1996

  44. Propofol/OpioidPercent Decrease on Emergence Alfentanil Technique Remifentanil Technique 100 75 Remifentanil Propofol 50 Propofol 25 Alfentanil 0 0 120 240 360 480 600 120 240 360 480 600 Time (Minutes) Time (Minutes) Shafer SL, ASA Refresher Course, Chapter 19, 1996

  45. Propofol/Remifentanil TIVA • Remifentanil: • 0.25 mg/kg/min • Propofol: • 80 mg/kg/min • Requires controlled ventilation Shafer SL, ASA Refresher Course, Chapter 19, 1996 • Little tolerance for interruption of remifentanil or propofol infusion

  46. Easy Propofol - Remifentanil • Add 1 mg of remifentanil to your 50 cc propofol syringe • Remifentanil concentration will be 20 mg/ml • Approach gives a bit less remi than in prior slide • Use with 70% N2O, or increase propofol dose to 100-120 mg/kg/min

  47. Easy Propofol - Ketamine • Add 50 mg of ketamine to your 50 cc propofol syringe • The ketamine takes the place of the nitrous oxide • Propofol effectively blunts the psychotomimetic effects to ketamine

  48. The ASPECT Data Base • Aspect Medical System • Inventor of the “Bispectral Index” • mysteriously called the “BIS” • Validating Bispectral Index as a measure of anesthetic depth • Movement in response to noxious stimulation - in > 300 patients undergoing surgery • Recall, Sedation, Eyelash reflex - in >100 volunteers

  49. The ASPECT Data Base • Patient trials (movement): • Thiopental • Propofol • Fentanyl/Alfentanil/Sufentanil • Isoflurane • Nitrous Oxide • Volunteer trials (recall, sedation, eyelash): • Propofol • Isoflurane • Alfentanil • Midazolam

  50. Recall vs. Heart Rate and Blood Pressure

More Related