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 Which influence the selection of the anesthetics are  Liver & kidney – target organs for toxic effects by the release of Fluoride, Bromide & other metabolites by halogenated compounds can affect this organ.  Respiratory system – if Inhalational anesthetics.  CVS – hypotensive effect by most anesthetic agents  Nervous system - neurological disorders 4

 A drug that brings about a reversible loss of consciousness.  to induce or maintain general anesthesia to facilitate surgery. 5

6 Anesthesia : Condition of reversible unconsciousness and absence of response to otherwise painful stimuli. 1. Unconsciousness 2. Analgesia 3. Immobility 4. Amnesia

 * GENERAL  * LOCAL  General anesthetics are given either as inhaled or intravenous agents.  They primarily have CNS effects  Local agents are injected at the operative site to block nerve conduction

 There are four stages:  Stage 1 - analgesia- reduced sensation of pain; the patient remains conscious and conversational  Stage 11 - excitement- delirium and combative behaviour ensue; there is an increase in blood pressure and respiratory rate.

 Stage surgical anesthesia- the patient is unconscious and regular respiration returns; there is muscle relaxation and decreased vasomotor response to painful stimuli  Stage iv - medullary paralysis- respiratory drive decreases and vasomotor output diminishes; death may quickly ensue

10 APPROACHES FOR TESTING DEPTH OF ANAESTHESIA - B- Blinking of eyelids on striking the eyelashes. - Swallowing - Regularity and depth of respiration. - Increase in respiratory rate and B.P. - Tightness of jaw muscles. Above responses fade on deepening of the anesthesia.

 The time from administration of a general anesthetic to the achievement of surgical anesthesia.  Induction is dependent on how fast the anesthetic reaches the CNS  RECOVERY IS THE REVERSE OF INDUCTION and it is dependent on how quickly the anesthetic is removed from the CNS

 Solubility  Pulmonary ventilation  Partial pressure of the inhaled agent  Alveolar blood flow  Arteriovenous concentration gradients

 HALOTHANE  ENFLURANE  ISOFLURANE  SEVOFLURANE  NITROUS OXIDE  There potency is defined base on the concept of minimum alveolar concentration ( MAC)

 Minimum alveolar concentration(MAC)is defined as the alveolar concentration at one atmosphere that produces immobility in 50% of patients exposed to a painful stimulus  The greater the MAC of an agent, the greater the concentration needed to provide anesthesia. Thus an agent with high MAC has low potency ( e.g.. Nitrous oxide)  MAC of any inhaled agent can be reduced using it in conjunction with analgesia such as opiods or sedative hypnotics

 The first of the halogenated volatile anesthetics to be developed.  Clinical use: it is used in the pediatric population because of its pleasant odor and lack of hepatotoxicity.  MAC: 0.75%

 It sensitizes the myocardium to the effect of catecholamines ( thus increasing the risk of arrhythmia).  Decrease heart rate and cardiac output and leads to lowered BP and peripheral resistance.  Toxicity: halothane hepatitis  Malignant hyperthermia.

 A potentially fatal reaction to any of the inhaled anesthetics, which results in hyperthermia, metabolic acidosis, tachycardia and accelerated muscle contraction  Treatment : Dantrolene and stop the offending agent

 Rapid induction and recovery, less potent than halothane  Fewer arrhythmias  Greater muscle relaxation  Proconvulsant 18

 Contraindications/Precautions  CI in renal failure. This anesthetic is not used in patients with kidney failure.  malignant hyperthermia susceptibility  seizure disorder  intracranial hypertension 19

 Rapid recovery  Good muscle relaxation  Stable cardiac output  Very less effect on heart  No rise in ICP.  One of the best Inhalational agent.. › Isoflurane maintains CO and coronary function better than other agents used in pts with ischemic heart disease. 20

 1. odorless and non-explosive gas.  2. Anesthetic action.  Good analgesia  Safe, non irritating  Rapid induction due to low solubility.  Rapid onset and recovery Negative points:  No muscle relaxation  Incomplete anesthesia,  Must be used in combination.. Toxicity: bone marrow depression with prolonged administration.  High concentrations may cause neuropathies 21

THIOPENTONE  Potent anesthesia  High lipid solubility  Rapid entry into brain  Decreased cerebral blood flow  Rapid onset of action  Short surgical procedures 22

Thiopentone Negative points:  Poor analgesia  Little muscle relaxation  Laryngospasm 23

 Good analgesia  Dissociative anesthetic.  Cardiovascular stimulant  Causes disorientation, hallucinations..  Increases cerebral blood flow. 24

 Ketamine affects the senses, and produces a dissociative anesthesia (catatonia, amnesia, analgesia) in which the patient may appear awake and reactive, but cannot respond to sensory stimuli.  These properties make it especially useful during warfare medical treatment.  Used in Trauma and emergency Surgical Procedures  also used in high-risk geriatric patients and in shock cases, because it also provides cardiac stimulation. 25

 Good analgesia  Mostly used with other CNS depressants during anesthesia  Because opiods rarely affect the cardiovascular system, they are particularly useful for cardiac surgery  Can cause resp. depression and muscle rigidity.. 26

 nonbarbiturate hypnotic agent and the most recently developed intravenous anesthetic.  Its rapid induction and short duration of action identical to thiopental.  Recovery occurs more quickly and with much less nausea and vomiting 27

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 Rapidly metabolized in the liver and excreted in the urine, so it can be used for long durations of anesthesia, unlike thiopental.  Hence, Propofol is rapidly replacing thiopental as an intravenous induction agent. 29

 Ultra short acting non-barbiturate hypnotic  No analgesic properties  Used for induction followed by other agents  Produces postoperative nausea & vomiting  Lowers plasma cortisol levels 30

There are two classes determined by their bonding the lipophilic portion of the molecule with the hydrophilic components- either an ester or amide bond.

NAME THE ESTER ANESTHETICS NAME THE AMIDE ANESTHETICS  COCAINE  BENZOCAINE  PROCAINE  TETRACAINE  LIDOCAINE  MEPIVACAINE  BUPIVACAINE  PRILOCAINE

 Block Na channels by binding to specific receptors on inner portion of the channel.  First loss of pain, then temp, touch, pressure at the last. 33

 Using epinephrine mixed with local anesthetics causes vasoconstriction, which decreases clearance of the agent, increases duration of action, and decreases the total required dosage. 34

 Short local procedures  Spinal anesthesia  Minor surgical procedures 35

 Severe CVS toxicity – Bupivacaine  Hypertension & arrhythmias – cocaine  CNS excitation  Seizures 36