Types of anaesthesia.pptx DRZWEYANANAING

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1. Types of anaesthesia Capt. ZWE YAN NAING PG 2 nd year M.MedSc (O&G)

2. DEFINITION Anesthesia is an artificially induced state of  partial or total loss  of sensation, occurring with or without loss of  consciousness.

3. CLASSIFICATION OF ANETHESIA General anesthesia Regional anesthesia

4. General anesthesia A reversible state of central nervous system depression resulting in loss of response to and perception of external stimuli.

5. Triad of General anaesthesia Hypnosis Analgesia Muscle relaxation

6. STAGES OF GENERAL ANESTHESIA Stage I : This  is  also  known  as  induction,  it  is  the  period  between  the  administration  of  induction  agents  and  loss  of  consciousness .  Stage II: It   is  known  as  excitement  stage,  it  is  from  loss  of  consciousness  to  loss  of  eyelid  reflexes.  During  this  stage  patients respiration and heart rate may become irregular .  Stage III: It  is  known  as  Surgical  anesthesia,  respiratory  depression, skeletal muscle relax occurs.  Stage IV: It  also  known  as  Over  dose,  occur  when  too much  anesthetic  medication  given.  Resulting  in  cessation  of  respiratory and potential cardiovascular collapse

7. Pre-medication Serve to calm the patient, relieve the pain and protect against undesirable effects of anesthetics or the surgical procedure ▫ Antacids (neutralize stomach acidity) ▫ H2 blockers like famotidine (Reduce gastric acidity) ▫ Anticholinergics like glycopyrrolate (Prevent bradycardia and secretion of fluids) ▫

8. Antiemetics like ondansetron (Prevent aspiration of stomach contents and postsurgical nausea and vomiting and) ▫ Antihistamine like diphenhydramine (Prevent allergic reactions) ▫ Benzodiazepines like diazepam (Relieve anxiety) ▫ Opioids like fentanyl (Provide analgesia) ▫ Neuromuscular blockers (Facilitate intubation and relaxation

9. Intravenous anaesthetics thiopentone Propofol Etomidate Benzodiazepines Ketamine

10. IV sedative/hypnotic used in the induction or maintenance of anesthesia  Widely used and has replaced thiopental as first choice for anesthesia induction and sedation, because it does not cause postanesthetic nausea and vomiting  The induction of anesthesia occurs within 30–40 seconds of administration  Supplementation with narcotics for analgesia is required  Propofol decreases blood pressure without depressing the myocardium  It also reduces intracranial pressure due to systemic vasodilation PROPOFOL

11. BARBITURATES The barbiturates are not significantly analgesic, require some type of supplementary analgesic administration during anesthesia to avoid objectionable changes in blood pressure and autonomic function  Can cause apnea, coughing, chest wall spasm, laryngospasm, and bronchospasm  Thiopenta l ◦ Potent anesthetic but a weak analgesic ◦ Ultrashort-acting barbiturate ◦ Has minor effects on the cardiovascular system, but it may contribute to severe hypotension in patients with hypovolemia or shock. All barbiturates

12. BENZODIAZEPINES  Used in conjunction with anesthetics to sedate the patient  Midazolam  Diazepam  Lorazepam  Facilitate amnesia while causing sedation  Enhance the inhibitory effects of various neurotransmitters, particularly GABA  Minimal cardiovascular depressant effect  Potential respiratory depressants  Can induce a temporary form of anterograde amnesia in which the patient retains memory of past events, but new information is not transferred into long-term memory ◦ Important treatment information should be repeated to the patient after the effects of the drug have worn off

13. OPIOIDS Commonly used with anesthetics due to their analgesic property  The choice of opioid used perioperatively is based primarily on the duration of action needed  Fentanyl, remifentanil ◦ Induce analgesia more rapidly than morphine ◦ Administered intravenously, epidurally , intrathecally  Not good amnesics  Can cause hypotension, respiratory depression, muscle rigidity and postanesthetic nausea and vomiting  Opioid effects can be antagonized by naloxone

14. KETAMINE A short-acting nonbarbiturate anesthetic  Used for short procedures  Induces a dissociated state in which the patient is unconscious (but may appear to be awake) and does not feel pain  This dissociative anesthesia provides sedation, amnesia, and immobility  Interacts with the N-methyl-D-aspartate receptor  Stimulates the central sympathetic outflow, which, in turn, causes stimulation of the heart with increased blood pressure and CO ◦ Beneficial in patients with hypovolemic or cardiogenic shock and in patients with asthma) ◦ Not used in hypertensive or stroke patients  Causes post-operative hallucinations

15. MUSCLE RELAXANTS Used to stop reflexes to facilitate tracheal intubation, and to provide muscle relaxation as needed for certain types of surgery  Mechanism of action is blockade of the nicotinic acetylcholine receptors in the neuromuscular junction  Include pancuronium , rocuronium , succinylcholine, and vecuronium

16. Inhalational anaesthetics Nitrous oxide Isoflurane Sevoflurane Desflurane Halothane

17. Mechanism of action Anesthetics increase the sensitivity of GABA receptors to the neurotransmitter GABA prolonging the inhibitory chloride ion current after GABA release, reducing the postsynaptic neurons excitability ◦ Anesthetics increase the activity of the inhibitory glycine receptors in the spinal motor neuron ◦ Anesthetics block excitatory postsynaptic nicotinic currents

18. Potency of inhaled anesthetic is defined as the minimum alveolar concentration (MAC)  MAC: the concentration of anesthetic gas needed to eliminate movement among 50% of patients  Expressed as the percentage of gas in a mixture required to achieve the effect  The smaller MAC is the more potent the drug

19. NITROUS OXIDE Non-irritating and a potent analgesic but a weak general anesthetic  Nitrous oxide is frequently employed at concentrations of 30–50% in combination with oxygen for analgesia, particularly in dental surgery .  Nitrous oxide at 80 percent (without adjunct agents) cannot produce surgical anesthesia  Combined with other, more potent agents to attain pain-free anesthesia  Mechanism of action is unresolved, might involve activity on GABAA and NMDA receptors  Least hepatotoxic of all inhaled anesthetics

20. ISOFLURANE Undergoes little metabolism, not toxic to the liver or kidney  Does not induce cardiac arrhythmias  Produces dose-dependent hypotension due to peripheral vasodilation

21. SEVOFLURANE Low pungency, allowing rapid induction without irritating the airway, making it suitable for inhalation induction in pediatric patients  Replacing halothane for this purpose  Metabolized by the liver, and compounds formed in the anesthesia circuit may be nephrotoxic

22. DESFLURANE Provides very rapid onset and recovery due to its low blood solubility, the lowest of all the volatile anesthetics  Popular anesthetic for outpatient surgery  Irritating to the airway and can cause laryngospasm, coughing, and excessive secretions,  Degradation is minimal, tissue toxicity is rare

23. HALOTHANE Potent anesthetic, weak analgesic.  Administered with nitrous oxide, opioids or local anesthetics  Being replaced by other agents due to its adverse effects Adverse effects ◦ Cardiac effects: Vagomimetic effects, bradycardia, can cause cardiac arrhythmias ◦ Malignant hyperthermia:  Rare and life threatening condition  Uncontrolled increase in skeletal muscle oxidative metabolism, which overwhelms the body’s capacity to supply oxygen, remove carbon dioxide, and regulate body temperature  If untreated would cause circulatory collapse and death  Treatment: Dantrolene administration

24. RECOVERY Postoperatively, the anesthetic admixture is withdrawn, and the patient is monitored for the return of consciousness  If skeletal muscle relaxants have not been fully metabolized, reversal agents may be used  The anesthesiologist continues to monitor the patient for full recovery, with normal physiologic functions

25. REGIONAL ANASETHESIA Topical Anesthesia Infiltration Anesthesia Peripheral nerve block Anesthesia Spinal Anesthesia Epidural Anesthesia

26. TOPICAL ANAESTHESIA Anaesthesia of mucous membranes of nose, mouth, throat, tracheobronchial tree, esophagus and genitourinary tract can be produced By direct application of aqueous solution of salts of LA or by suspension of poorly soluble LA Tetracaine , lidocaine, cocaine are typically used Cocaine is only used in nose, throat, eat where it uniquely produces vasoconstriction as well as anaesthesia

27. INFILTRATION ANAESTHESIA Injecting LA directly into the tissue without taking into consideration the course of cutaneous nerves It can be so superficial as to only include skin; and can also include deeper structure Duration of action can be almost doubled by adding epinephrine (5 microgm /kg) which also decreases peak plasma levels of LA Epinephrine containing solution should not be injected into tissues supplied by end arteries eg . Fingers, toes, ear and penis

28. NERVE BLOCK ANAESTHESIA Inj. of LA solution about individual nerves or plexuses produces even greater area of anaesthesia It also anesthetizes somatic nerves, producing skeletal muscle relaxation The areas of sensory and motor block usually start several cms distal to the site of inj.

29. Brachial plexus block  useful in upper extremity procedures Intercostal block  effective for anterior abdominal wall Cervical plexus block  appropriate for surgery of neck Sciatic and femoral nerve block  useful for surgeries distal to the knee Pudental block - perineum Other useful nerve blocks are given at wrist, ankle, individual nerves

30. SPINAL ANAESTHESIA Follows the inj. of LA into CSF in the subarachnoid space Ability to produce anaesthesia for considerable part of the body With a dose that produces negligible plasma levels, have made it one of the most popular techniques Clinically most important effect of sympathetic blockage of spinal anaesthesia is on CVS

31. Vasodialation (venous > arterial)  venous pooling Venous return can be increased by modest 10-15 degrees by head down tilt or by elevating the legs Patients are also adm. bolus fluids before spinal anaesthesia in order to compensate for hypotension Drugs with preferential veno constrictive and chronotropic properties are used

32. Drugs most commonly used are lidocaine, bupivacaine Choice of drug depends chiefly upon desired duration of action For short procedures  Lidocaine Intermediate to long  Bupivacaine Long  Tetracaine Most important pharmacological characters include the amount, volume of drug injected

33. Epinephrine is added to increase the duration of intensity of block Baricity of LA will determine the direction of its migration Hyperbaric solution  settle in dependent part of the sac Hypobaric solution  goes in the opposite direction Isobaric solution  stays in the vicinity

34. Complications: Neurological sequalae can result from introduction of foreign substances into subarachnoid space Infection, hematoma, mechanical trauma High conc. Of LA can cause irreversible block Several reports of transit or longer lasting neurological deficit following lidocaine (5%) are reported

35. Most common feature following spinal anaesthesia is postural headache It should be thoroughly investigated to exclude serious complications like meningitis Spinal anaesthesia is safe and effective anaesthesia for lower abdomen, extremity and perineum

36. EPIDURAL ANAESTHESIA Injecting LA into epidural space Can be performed in sacral hiatus (caudal anaesthesia), lumbar, thoracic, cervical region of spine Its popularity is because of catheters that can be placed into epidural space allowing either continuous or bolus administration of LA Choice of drug is determined by duration of its action required

37. Used in labor and post –op anaesthesia Lidocaine (2%) is most frequently used intermediate acting Bupivacaine is used for long duration anaesthesia Chloroprocaine (2/3 %) provides rapid onset and very short duration of action Duration of action prolonged and systemic toxicity is decreased by addition of Epinephrine

38. OPIATE ANAESTHESIA Spinally administered opioids by themselves do not produce sufficient anaesthesia Hence have found greater use in treatment of post op and chronic pain For post op anaesthesia  spinally morphine (0.2-0.5 mg) usually provides 8-16 hrs of anaesthesia Epidurally , morphine (2-6 mg) is used For cancer pain  repeated doses of epidural LA can provide anaesthesia for several months duration But, after regular usage tolerance does develop

39. LOCAL ANAESTHETICS Amides (lidocaine) and esters (procaine )  Cause loss of sensation and, in higher concentrations, motor activity in a limited area of the body  Applied or injected to block nerve conduction of sensory impulses from the periphery to the CNS

40. Mechanism : ◦ Local anesthesia is induced when propagation of action potentials is prevented, so that sensation cannot be transmitted from the source of stimulation to the brain ◦ Work by blocking sodium ion channels to prevent the transient increase in permeability of the nerve membrane to sodium that is required for an action potential to occur

41. Lidocaine  Bupivacaine  Procaine  Ropivacaine  Tetracaine  Mepivacaine

42. Local anesthetics cause vasodilation, which leads to rapid diffusion away from the site of action and results in a short duration of action  Adding the vasoconstrictor epinephrine to the local anesthetic, the rate of local anesthetic diffusion and absorption is decreased  This both minimizes systemic toxicity and increases the duration of action

43. TOPICAL ANAESTHETICS They are applied directly to the skin or mucous membranes  Benzocaine is the major drug in this group  Lidocaine and tetracaine ca be used topically  They are used to relieve or prevent pain from minor burns, irritation, itching  They are also used to numb an area before an injection is given.  Expected adverse effects involve skin irritation and hypersensitivity reactions

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