Comprehensive Guide to Anesthesia: Types, Techniques, and Applications"
- 1. ANESTHESIA
- 2. INTRODUCTION- • The word anesthesia is coined from two Greek words: "an" meaning "without" and "aesthesis“ meaning "sensation". • Anesthesia refers to the practice of administering medications either by injection or by inhalation (breathing in) that block the feeling of pain and other sensations, or that produce a deep state of unconsciousness that eliminates all sensations, which allows medical and surgical procedures to be undertaken without causing undue distress or discomfort.
- 4. ANESTHETICS- The drugs that brings about a reversible loss of conciousnessand all sensation. ESSENTIAL COMPONENTS OF ANESTHESIA- • Analgesia • Hypnosis • Muscles relaxation • Depression of reflexes TYPES OF ANESTHESIA- • Anesthetic drugs are the agents that produces anesthesia or bring about reversible loss of sensation . Two types a) General anesthetics b) Local & regional anesthetics.
- 5. GENERAL ANESTHESIA- • General anesthesia refers to inhibition of sensory, motor and sympathetic nerve transmission at the level of the brain, resulting in unconsciousness and lack of sensation. • General anesthesia – for surgical procedure to render the patient unaware /unresponsive to the painful stimuli • Drugs producing General Anesthesia – are called General Anesthetics GENERAL ANESTHETICS- • General Anesthetics are the drugs which produce reversible loss of all sensation and consciousness, or simply, a drug that brings about a reversible loss of consciousness • These drugs are generally administered by an anesthesiologist in order to induce or maintain general anesthesia to facilitate surgery • General anesthetics are – mainly inhalation or intravenous
- 6. PATHWAY OF GENERAL ANESTHESIA- Gas mixture ↓ Alveoli in lungs ↓ Arterial blood ↓ Brain and other tissues ↓ venous blood CLASSIFICATION OF GENERAL ANESTHESIA- Inhalation: 1. Gas: Nitrous Oxide 2. Volatile liquids: Cyclopropane - Ether - Halothane - Enflurane - Isoflurane - Desflurane - Sevoflurane Intravenous route: 1. Inducing Agent 2. Slower acting Agents -Thiopentone sodium - Benzodiazepines- Diazepam,Lorazepam,midazolam -Propofol -dissociative anesthetics- Ketamine -Etomidate - Opioid analgesics- fentanyl
- 7. NITROUS OXIDE (N2O)- • Colorless, odorless gas neither flammable and nor explosive , cheap and commonly used anesthetics. • fast onset and recovery. • Nitrous oxide (N₂O), commonly known as "laughing gas,". • It is often administered in combination with other anesthetic agents to enhance patient comfort during surgical procedures- 70% N2O +25-30% O2+0.2-2% (Halothene). Mechanism of Action: Nitrous oxide works by modulating neurotransmitter systems, primarily affecting opioid receptors, NMDA receptors, and GABA receptors, leading to its sedative and analgesic effects. Administration: It is typically delivered through a mask or nasal cannula, where it is inhaled along with oxygen. INDICATION- During dental surgery obstetrics Post operative ADVERSE EFFECT- Nausea dizziness bradycardia hypoventilation diffusion hypoxia hallucination headache hyperthermia ADVANTAGES- Rapid onset ,non irritating ,minimal effect on respiration, heart rate ,blood pressure ,hepatoxicity. DISADVANTAGES- Less potent ,poor muscles relaxant property ,risk of air embolism
- 8. CYCLOPROPANE- • Colour less and non irrtating gas. • Highly iflammable and markedly reduces respiratory rate. • uses are as N2O but causes dose dependant hypotension. • Least effect on liver and kidney. VOLATILE LIQUIDS: ETHER- Colorless ,highly volatile liquid ,inflammable and explosive , often given by open drop method. Cheap and safe. INDICATION- for maintenance of anesthesia. ADVERSE EFFECT- Hypersensitivity convulsion ECG changes Apnea Vomiting Cardiotoxicity ADVANTAGES- potent , inexpensive ,good analgesic action , good muscles relaxants ,no risk hepatotoxicity DISADVANTAGES- inflammable , slow induction ,highly irritant ,produce post operative nausea and vomiting
- 9. HALOTHENE- • colorless, non-flammable liquid that is vaporized for inhalation. • It has a relatively low blood-gas partition coefficient, which allows for rapid onset and offset of anesthesia. Mechanism of Action: Halothane acts primarily by enhancing inhibitory neurotransmission and inhibiting excitatory neurotransmission in the central nervous system. This leads to sedation and muscle relaxation. Administration: Halothane is delivered via a vaporizer that mixes it with oxygen and other gases. It can be used for both induction and maintenance of anesthesia. Side Effects: cardiovascular depression respiratory depression, decreased blood pressure halothane hepatitis ADVANTAGES- non irrtant , non inflammable ,postoperative nausea and vomiting DISADVANTAGES- poor muscles relaxants and analgesics effect , depress respiratory and myocardial function.
- 10. ENFLURANE- • Enflurane is a colorless, non-flammable liquid that is vaporized for inhalation. • It has a moderate blood-gas partition coefficient, allowing for relatively rapid induction and recovery. • Better muscles relaxants than halothene. • Bronchodilation similar to halothene. ISOFLURANE- • Administered through a special vaporizer. • 1.5% - 3% induces anesthesia in 7-10 min and 1-2% for maintenance. • increase heart rate and decrease blood pressure. • low toxicity. • safer in in patient with myocardial infarction • respiratory depression.
- 11. DESFLURANE- • Out patient surgery post operative cognition and motor impairment is short lived. • rest similar to isoflurane. SEVOFLURANE- • Plesant and can be administered via face mask. • No problem in induction ,good acceptability ,even by paediatrics patients. • Degraded by soda lime not recommended for used in closed circuit. • for both out- patient and inpatient surgery. • very costly. • rest similar to isoflurane. • Adverse effect - respiratory depression.
- 12. Intravenous Agent- used in combination with inhaled anesthetics to : • maintain general anesthesia. • provide sedation. • protect the brain. THIOPENTONE SODIUM- ( 3-5mg /kg as 2.5% solution) - • Thiopentone sodium, also known as thiopental, is a barbiturate used primarily as an anesthetic agent . • highly lipophilic barbiturate, which allows for rapid onset of action when administered intravenously. Mechanism of Action- It works by enhancing the effects of the neurotransmitter GABA (gamma- aminobutyric acid) at the GABA-A receptor, leading to increased inhibitory neurotransmission in the central nervous system. Side Effects: respiratory depression cardiovascular depression hypotension. Thiopentone can also cause venous irritation at the injection site. laryngospasm
- 13. PROPOFOL- • Effects similar to barbiturates. • Propofol acts quickly, typically inducing anesthesia within 30 seconds. • enhances GABA-A receptor activity, resulting in increased inhibitory neurotransmission, which leads to sedation and anesthesia. Uses: • General Anesthesia. • Sedation. ETOMIDATE - • Minimal cardiovascular effect. • potential adrenocortical supression(0.2-0.5mg/kg).
- 14. KETAMINE- • Ketamine is a dissociative anesthetic used medically for induction and maintenance of anesthesia. • It is also used as a treatment for depression and in pain management. • Ketamine is an NMDA receptor antagonist which accounts for most of its psychoactive effects.It also has effects on opioid receptors and enhances GABA activity, contributing to its anesthetic and analgesic properties. • patients may feel detached from their environment . • Duration of action: : Intramuscular: 0.5–2 hours; Insufflation: 45–60 min; By mouth: 1–6+ hours; • Elimination half-life: : Ketamine: 2.5–3 hours; Norketamine: 12 hours; • Excretion: Urine: 91%; Feces: 3%; • Metabolism: Liver, intestine (oral). • Common side effects include: - Hallucinations or vivid dreams during recovery - Dizziness - Nausea
- 15. FENTANYL- • Fentanyl is a potent synthetic opioid commonly used in anesthesia for its analgesic properties. • It works by binding to the mu-opioid receptors in the brain and spinal cord, leading to significant analgesia and sedation. • It also modulates pain pathways and can reduce the perception of pain. • Fentanyl can be administered via various routes, including: - Intravenous (IV) for rapid onset in anesthesia - Transdermal patches for chronic pain management - Intranasal, oral, and sublingual The effects of fentanyl are relatively short-lived (30 to 60 minutes) when given IV. BALANCED ANESTHESIA-It is combination of intravenous and inhaled anesthetic agents. first intravenous then inhaled anesthetic agents are used.like inducing agent thiopentone sodium maintained by inhaled anesthetics and supplemented by benzidiazepines.
- 16. PRE-ANESTHETIC 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 atropine and glycopyrrolate (Prevent bradycardia and secretion of fluids) Antiemetics like ondansetron (Prevent aspiration of stomach contents and postsurgical nausea and vomiting and) • Antihistamine (Prevent allergic reactions) • Benzodiazepines like diazepam (Relieve anxiety) • Opioids like fentanyl (Provide analgesia) • Neuromuscular blockers (Facilitate intubation and relaxation)
- 17. LOCAL ANESTHESIA- • Local anesthesia - reversible inhibition of impulse generation and propagation in nerves. • In sensory nerves, such an effect is desired when painful procedures must be performed, e.g., surgical or dental operations • Drugs producing Local Anesthesia – are called Local Anesthetics e.g. Procaine, Lidocaine and Bupivacaine etc. • Local anesthesia inhibits sensory perception within a specific location on the body, such as a tooth or the urinary bladder. • Regional Anesthesia : Regional anesthesia renders a larger area of the body insensate by blocking transmission of nerve impulses between a part of the body and the spinal cord. • Two frequently used types of regional anesthesia are - -spinal anesthesia Spinal Anesthesia: it is achieved by injection 1.8 ml of 5% lignocaine solution into the subarachnoid space through a lumber puncture. Other drugs which can be used are cinchocaine, procaine and amethocaine. • It can cause serious hypotension. - epidural anesthesia.
- 18. CLASSIFICATION /DOSE/ ROUTE OF LOCAL ANESTHESIA-