ANAESTHESIA-INTRAVENOUS

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ANAESTHESIA-INTRAVENOUS

  1. 1. - Nithin Kumar
  2. 2. Classification Inducing agents:-Thiopentone sodium,-Methohexitone sodium,-Propofol,-Etomidate. Slower acting drugs: Benzodiazepines-Diazepam,Lorazepam,Midazolam. Dissociative anesthesia-Ketamine. Opioid analgesia-Fentanyl.
  3. 3. Mechanism: Major targets are GABAA receptor gatedCl-channel.(Many inhalationanesthetics, barbiturates, benzodiazepines andpropofol) NMDA receptors are type of glutamatereceptor.(N2O,Ketamine)
  4. 4. Inducing agents: Drugs which on i.v. injection produce loss ofconsciousness in approximately 11 seconds. Used because of rapidity of onset of action. Then maintain by inhalational agents. Supplemented with analgesics and muscle relaxants.
  5. 5. Thiopentone sodium: An ultra-short-acting barbiturate usedcommonly in the induction phase. Injected i.v. (3-5mg/kg) produces unconsciousness in15-20 seconds. Consciousness regained in 6-10 min. Disposal mainly by hepatic metabolism (eliminationt1/2 is 7-12hrs).
  6. 6.  Poor analgesic effect. Weak muscle relaxant. Respiratory depression is transient and severe in largedoses. Does not sensitizes the heart to adrenaline, cardiacarrhythmia are rare. Indications:- Minor surgery that are less painful.
  7. 7. Adverse effects: Laryngospasm-relived by atropine premedication. Fall in BP. Shivering and delirium. Acute intermittent porphyria-C/I.Other uses: Rapid control of convulsions. Narco analysis.
  8. 8. Methohexitone sodium: short-acting and has a rapid onset ofaction. Three times more potent and similar inits effects to thiopentone sod. Has a quicker and briefer action(5-8 min). Indication:-For oral surgery and dentistry. A/E:-Excitement during induction and recoveryperiod.
  9. 9. Propofol-Milk of amnesia Short-acting for both induction as well asmaintenance. An oily liquid employed as a 1% emulsion. Unconsciousness occurs 15-45 sec and lasts 5-10 min. Propofol is highly protein-bound and is metabolizedby conjugation in the liver. Intermittent injection or continuous infusion used fortotal i.v. anesthesia when supplemented by fentanyl. Most suited for out patient surgery.
  10. 10. Adverse effect: Fall in BP and bradycardia. Pain on injection. Dystonia and myoclonic movements are common. Propofol has reportedly induced priapism in someindividuals.Other uses: In sub-anesthetic doses, it is the drug of choice forsedating intubated patients in ICU.
  11. 11. Etomidate: Short-acting induction anesthesia. Has a briefer duration of action (4-8 min) thanthiopentone. Etomidate is highly protein bound and metabolised byhepatic and plasma esterases to inactive products. Onset of action: 30–60 seconds. Peak effect: 1 minute.Indications: As sedative, for short procedures such as reduction ofdislocated joints and cardioversion.
  12. 12. Slower acting drugs:Benzodiazepines: Used for induction, maintenance and supplementinganesthesia as well as for conscious sedation. In larger doses injected i.v. produce sedation, amnesiaand unconsciousness in 5-10mins. If no anesthetic or opioid is given, the patient becomesresponsive in 1hr. But, amnesia for 2-3hrs. Poor analgesics. Opioid or N2O is added, if the procedure is painful.Indication-in endoscopies, cardiaccatheterization, angiographies, regional anesthesia,fracture setting.
  13. 13.  Action is rapidly reversed by flumazenil 0.5-2mg i.v.Diazepam: 0.2-0.5mg/kg , slow undiluted injection in a running i.v. This technique reduces burning sensation in vein andincidence of thrombophlebitis.Lorazepam: Potent, slower-acting, less irritating than diazepam. Amnesia is more profound. (Dose : 0.04 mg/kg)Midazolam: Water-soluble, shorter acting drug used for sedation ofintubated patients. (Dose : 1-2.5mg i.v.) In other critical care anesthesia as 0.02-0.1mg/kg/hrcontinuous i.v. infusion.
  14. 14. Ketamine: Related to phencyclidine-dissociative anesthesia. DA-characterised by profoundanalgesia, immobility, amnesia, feeling of dissociationfrom ones own body. Site of action-Cortical and sub cortical areas. Act by inhibiting NMDA receptors. Dose of 1-3mg/kg i.v. produces the above effects withina minute & recovery after 10-15 mins, but remainsamnesic for 1-2hr. Metabolized in the liver and has anelimination t1/2 3-4hrs.
  15. 15. Indications: Head and neck surgeries, asthmatics, Shortsurgeries, Burn dressings. Combined with diazepam used inangiographies, catheterization, and trauma surgeries.Adverse effects:-Heart rate, Cardiac output, BP increased.-Delirium, hallucination, involuntary movementsduring recovery.Contraindication:-HT,IHD.-Increased ICP.
  16. 16. Fentanyl: Short-acting, opioid analgesic related to pethidine. Has rapid onset and short duration of action about30-50 min. Strong agonist at the μ-opioid receptors. Used to supplement anesthetics in balancedanesthesia. Also used in neurolept analgesia in combination withdroperidol.
  17. 17. Indications: Combined with BDZs, used forendoscopic, angiographic, cardiac catheterization, burndressing and other minor procedures. used most often in operating rooms and intensive careunits.Adverse effects: Nausea, vomiting and itching oftenoccurs during recovery. Marked respiratory depression. Slight fall in BP.
  18. 18. Dexmedetomidine: An α2 agonist with sedative and analgesiceffect. Has a half life of 2-3hrs. Metabolized in liver and excreted mainly as inactiveurine metabolites. Adverse effects:-Hypotension and bradycardia.
  19. 19. AnestheticI.VDurationminsAnalgesia MusclerelaxationOthersThiopental 5 - 10 --- --- RespiratorydepressionPropofol 5-10 --- --- RespiratorydepressionKetamine 5-10 +++ --- HallucinationsMidazolam 5-20 --- +++ AmnesiaFentanyl 5-10 +++ --- Respiratorydepression
  20. 20. Balanced anesthesia: Modern anesthesia involves a combination of i.v.(forinduction) and inhalational anesthesia(formaintenance). Sometimes volatile(sevoflurane) isused for induction. Muscle relaxant-facilitate intubation. Local anesthetics-tissue infiltration, peripheral nerveblock. Potent opioid analgesic & CV drugs(β blocker, cachannel blocker)used to control autonomic responsesto noxious surgical stimuli.
  21. 21. Conscious sedation: This technique refers to drug induction alleviation ofanxiety & pain in combination with an altered level ofconsciousness associated with the use of smallestdoses of sedative medication. Pt.retains ability to maintain patent airway &responsive to verbal comments. Drugs-diazepam,midazolam,propofol.
  22. 22. Neuroleptanalgesia Method of i.v. anesthesia which combines the use ofneuroleptic drug with an opioid analgesic. Subject is conscious & able to co-operate duringsurgery. most favoured combination- droperidol + fentanyl After administering nitrous oxide with oxygenneuroleptanalgesia can be converted toneuroleptanesthesia. C/I - patients receiving MAO inhibitors, abuse drugsor alcohol, with Parkinson disease.
  23. 23. Complications During Anesthesia:-Respiratory depression,-Cardiac arrhythmias,-Fall in BP,-Acid pneumonitis,-Laryngospasm and asphyxia,-Awareness,-Delirium and convulsions.
  24. 24.  After anesthesia:-Nausea and vomiting,-Persisting sedation,-Pneumonia,-Atelectasis,-Nerve palsy,-Emergence delirium,-Organ toxicity.

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