Anesthesia Past Paper PDF

# ANESTHESIA ## Introduction ### Topics To Be Covered: 1. Pre anesthetic evaluation 2. Monitoring in anesthesia 3. Anesthesia machine 4. Anesthesia circuit 5. Airway 6. Inhalational anesthetic agents 7. Intravenous anesthetic agents 8. Neuromuscular blocker 9. Local anesthetic (regional anesthesi...

# ANESTHESIA ## Introduction ### Topics To Be Covered: 1. Pre anesthetic evaluation 2. Monitoring in anesthesia 3. Anesthesia machine 4. Anesthesia circuit 5. Airway 6. Inhalational anesthetic agents 7. Intravenous anesthetic agents 8. Neuromuscular blocker 9. Local anesthetic (regional anesthesia) 10. Central neural blockade (spinal and epidural anesthesia) 11. Oxygen therapy 12. Perioperative fluids 13. CPCR (cardiopulmonary cerebral resuscitation) ## General Anesthesia (GA) ### Components of General Anesthesia: * Loss of consciousness * Loss of Reflex Response * Amnesia * Analgesia * Muscle Relaxation ### Balanced Anesthesia: * The term is given by Dr. John Lundy and Ralph Milton Waters. * We give multiple drugs in the titrated ways that provide different components of Anesthesia. ### Steps of General Anesthesia: 1. Induction - Loss of Consciousness 2. Maintenance - Maintenance of unconsciousness 3. Reversal - Regain of consciousness. * Induction and maintenance can be done by both intravenous and inhalational agents. * Preoxygenation with 100% O₂ in a spontaneously breathing patient for 3-5 minutes is performed before induction depending on the requirement of the patient. It is usually performed to prevent hypoxia during induction. ### Important Information: * **TIVA (Total Intravenous Anesthesia)** If induction and maintenance is done using intravenous agents it is known as TIVA. Most commonly used agent is **Propofol**. ## Pre-Anesthetic Evaluation ### Focused History: * Two important information is obtained that helps in planning of the anesthesia in the patient. * Previous anesthesia exposure * Comorbidities in the patient * Medical and surgical histories * General examination * Systemic examination * Airway Evaluation * Routine investigations - depending upon the comorbidities and the type of surgery in the patient. ### ASA Grading (AMERICAN SOCIETY OF ANESTHESIOLOGY) * ASA grade I to VI - Elective surgery * ASA grade I to VI - Emergency surgery ### ASA Grading: 1. No comorbidity 2. Controlled comorbidity (Pte mild systemic disease) 3. Comorbidity with moderate limitation (pte severe) 4. Comorbidity is being a constant threat on life. These patients are never taken for elective surgery unless the benefit of the surgery is more than the risk of the surgery performed. 5. Surgery is the only option for survival 6. Comatose/Brain dead patients (for organ transplant) ### Important Information * Patients with cardiovascular comorbidities for non-cardiovascular surgeries - Goldman grading system. ### Airway Evaluation * History of previous anesthesia exposure and during that any airway mishap. * Physical evaluation of airway * Mouth opening is assessed. * Atlantooccipital joint movement * Neck joint movement * Mentohyoid/mentothyroid distance * Neck circumference * Mallampati grading ### Mallampati Grading: * Pre-anesthetic evaluation of airway. * Predicts the difficulty in intubation. * Predicts the difficulty in ventilation. ### Important Information: * Class III and IV is considered difficult in intubation. ### Previous Year's Questions: * Preoperative assessment of oral cavity for endotracheal intubation in an adult is done by? * Mallampatti score * Cormack lehane * ASA grading * AHA grading * (Fmge 2018) ### CormackLehane Grading * It is laryngoscopic view of glottic opening. * It is not a Pre-Anesthetic Evaluation of airway. * Difficulty in intubation can be classified according to the view during direct Laryngoscopy into 4 grades. * Grade 3 and 4 are considered to be difficult intubation. ### Preanesthetic Order: * Written informed consent regarding surgery and anesthesia. * Nil per oral prior to surgery. * Adults * 8 hours - Full fatty meals * 6 hours - Semisolid foods * 2 hours - Clear fluids * Pediatrics * 8 hours - Full fatty meals * 6 hours - Formulae Milk/semisolid foods * 4 hours - Breast Milk * 2 hours - Clear fluids (If 1hr in option choose it ) * Orders regarding previous medications: * Oral Antihypertensives - Continued till day of Surgery. * Oral Hypoglycemic drugs * Minor/Moderate Surgery - Omit the last dose. * Major Surgery - Omit the last dose and put the patient on Insulin to maintain the blood glucose level. * Antipsychotics, Antidepressants, Antiepileptics - continued till the day of surgery, except * Tricyclic Antidepressants - Stop 3 Weeks prior to surgery. * Lithium - Stop 24-48 hours prior to Surgery. * Thyroid medications - continued till the day of surgery. ### Important Information: * **Anti-Coagulants** * Aspirin - Continue till day of surgery. * Clopidogrel - Stop 5-7 days prior. * **Important Information:** For general anesthesia it is 5 days, and regional anesthesia it is 7 days prior to the surgery. If not specific 5 days is considered a better option. * Ticlopidine - Stop 14 days prior. * LMWH - Stop 12-24hours prior. * Warfarin - Stop 3-4 days prior. * Unfractionated Heparin - Stop 6 hours prior to surgery. * **Important Information:** For coronary stenting. * Bare metal stent - gap of one month before elective surgery. * Medicated stent - gap of one year before elective surgery. * Steroids - Continue with the peri-operative supplementation, but this has three contraindications and steroids need to be stopped. * Diabetes * Active infections * Immunodeficiency * Herbal medications - stop 6-8 weeks prior. * Hormone replacement therapy - stop 6-8 weeks prior (Oral contraceptive pills need not to be stopped). * Apart from these drugs, rest of the drugs can be continued till the day of surgery. ## Pre-Operative Medications: * Depending upon the requirement of the patient and type of surgery. * **To alley anxiety:** Anxiolytics are used, for e.g., Benzodiazepines (midazolam, diazepam, lorazepam). * **To decrease pain/analgesia** * **To decrease reflex response** * **To decrease secretions** * **Anti-aspiration prophylaxis** * Anticholinergics * To decrease secretion - Glycopyrrolate * Sedation - scopolamine * To descrease reflexes/vagolytics - Atropine ### Previous Year's Questions: * Purpose of glycopyrrolate before GA? * Decrease laryngeal secretions * Muscle relaxation * Prevents aspiration * Provides analgesia * (AIIMS May 2018) ### Preoperative Antibiotics Prophylaxis recommendation * 1 hour prior to surgical incision is the best time to give antibiotic prophylaxis. ## Monitoring in Anesthesia ### According to ASA guidelines: * **Standard I say, presence of registered anesthesiologist is mandatory.** * **Standard II say, that continuous monitoring of oxygenation, ventilation, metabolism and temperature of the patient.** ### FIVE MANDATORY MONITORS: * **ECG-Lead II and V5 are the most important leads.** ### Important Information: * **Lead II for Arrhythmia** * **VS for Myocardial Infarction** * **Non-Invasive Blood pressure monitoring (NIBP)-mandatory in every surgery ** * **Invasive blood pressure monitoring is attached in certain surgical cases where massive blood loss is expected like neuro surgery, tumor removal etc.** * **Pulse oximetry - SPO₂ probe, measures oxygen saturation of arterial blood** * **Capnography - graph of expired CO₂ vs time.** * **Temperature (core temperature).** ### Desirable Monitors: * **Bispectral Index monitoring (BIS)- depth of anesthesia** * **Neuromuscular monitoring - adequacy of neuromuscular blockade** ### Other monitors are attached when required: * CVP monitor * PAP monitor * Echo * Transesophageal cardiography (TEE) - Best perioperative cvs monitoring & mat sesitive monitur to diagnose Air lembolism * **CAPNOGRAPHY** - mast sesitive monitur tu diagnose Air lembolism. * Graphical representation of expired CO₂ vs Time * (00:55:19) ### Important Information: * **CO₂ production** - due to metabolism * **CO₂ carried**- by circulation * **CO₂ exchange** - by ventilation ### Differential Diagnosis of flat capnogram: * Accidental extubation * Circuit disconnection * Stoppage of mechanical ventilation - ventilation stops showing flat capnograph * Absolute/complete bronchospasm * Cardiac arrest * Oesophageal intubation ### Normal graph: * Et CO₂ → 35-45 mmHg ### Important Information: * Et CO₂ value should be between 35-45 mmHg * **There are four phases** * Phase I - Dead space ventilation * Phase II - Dead space + Alveolar Ventilation * Phase III - Alveolar Ventilation (plateau) * Phase IV - Inspiration **Phase I:** anatomical dead space **Phase II:** alveolar gas begins to mix with the dead space gas. **Phase III:**elimination of CO₂ from the alveoli **Phase IV:** ### Increased Et CO₂ * Hypermetabolism (fever, malignant hyperthermia, shivering) * Hypoventilation ### Decreased Et CO₂ * Hypometabolism (hypothermia, anesthesia) * Hyperventilation * Hypoperfusion (embolism, shock) ### Abnormal graphs of Capnography: * **Refer Table 1.1** ### Use of Capnograph during CPCR: * **Cardiopulmonary cerebral Resuscitation** * Confirmation of airway device * Adequacy of chest compression. ### Important Information: * **Et CO₂ mmHg:** * >20 mmHg if the compression is adequate. * <10mmHg compression is not adequate. * **Indication of return of spontaneous circulation.** ### PULSE OXIMETER: * Measures pulse rate and estimates the oxygen saturation of hemoglobin on a non-invasive continues basis. ### Important Information: * 0 indicate patient is in coma * 100 indicate full awareness. * Desirable intra op value is in between 40 to 60. ### Previous Year's Questions: * Depth of anesthesia is best measured by? * BIS? BSI * MAC * TOF * Post tetanic potentiation * (NEET JAN 2019) ### TEMPERATURE MONITORING: * Core temperature is monitored. ### NEURO-MUSCULAR MONITORING: * Indicates adequacy of muscle paralysis. * Most common nerve used - Ulnar nerve. * Most common electrical stimulus used - Train of four stimulus. ### CVP MONITOR: * Central venous pressure monitoring. * Tip of the catheter is left between SVC and Right atrium. * Monitors the right atrial pressure of the heart. ### Important Information: * **Swan-Ganz catheter/Pulmonary artery catheter** - tip has a balloon, which is wedged in pulmonary capillaries. It measures the left atrial pressure of the heart. ### Table 1.1 Abnormal graphs of Capnography 1. **CO₂ value gradually decreasing**. **Hyperventilation** 2. **Intra op sudden drop of CO₂. Air Embolism(due to decrease in perfusion)** 3. **CO₂ retains and graph ↑↑ in Hypoventilation** 4. **Graph ↑↑ in Height due to the hyper metabolic state. Malignant hyperthermia (Et CO₂ becomes double or triple)** 5. **Base line is elevated. CO₂ Rebreathing. Can occur due to: CO₂ absorber has expired. Mixing of inspiratory and expiratory gases due to incompetence of the valves.** 6. **Upsloping of phase III [SHARK FIN PATTERN]. Due to Partial obstruction. Can occur due to: Bronchospasm. ET tube partial obstruction. COPD. Bronchial asthma.** 7. **Return of spontaneous ventilation (repeat the dose of NMB)** ## ANESTHESIA MACHINE * 1st machine - Dr. Edmund Boyle's (Boyle's machine) * Receives gas from compressed source. * Mixes the gas in known concentration and flow. * Delivers to the patient at a pressure which patient can tolerate. ### It has two parts: #### 1. Electrical Component: * Master switch * Power backup * Power failure indicator * Electrical sockets * Circuit breaker #### 2. Mechanical/pneumatic component: ##### High pressure system: * Hanger Yoke Assembly System * Cylinder pressure indicator/ Bourdon's pressure gauge * First pressure regulator ##### Intermediate pressure system: * Pipeline connection inletDISS * Pipeline pressure indicator * Second pressure regulator * Piping * Emergency oxygen flush * Gas pressure failure alarm * Flow control valve ##### Low pressure system: * Flowmeters * Vaporizer * Back bar - vaporizer and flow meter attached * Hypoxia guard * Common gas outlet ### High Pressure System: * Hanger Yoke Assembly - Gas cylinders are mounted in this. ### Cylinders: * Valve screwed to cylinder * Shoulder * Body and shoulder are color coded. * Label (most important) * Color coding * Pin index system - prevents incorrect attachment of the cylinders * Size - A to HH ### Important Information: * **Type E** is most common cylinder size attached to anesthesia machine. ### Intermediate Pressure System: * Pipeline supply * Piping * Pipeline inlet (DISS) * Pipeline pressure indicator - Normal pressure: 55-60 psi ### Low Pressure System: * Everything output from flow control valve. * **Flowmeters** * Flowmeters are of 2 types: * Mechanical flowmeters (glass flowmeters) * Electronic flowmeters * **Mechanical flowmeters** * **Flow Control Valve** * **Thorpes tube** * **Rotameter** * **Pipeline inlet connection:** - Prevents incorrect attachment of pipeline to system * **DISS - Diameter Index Safety System.** * **Oxygen cylinder:** - 2000 psi. **N₂O cylinder :** - 760psi. * **Emergency O₂ Flush** (Intermediate pressure): On a press of button. 35-75 liters of O₂ per minute at 55 to 60 psi will come out. * **Oxygen pressure failure indicator:** O₂ pressure falls below 30 psi, alarm is activated. * **Flow control valve - color coded** ### Arrangement of flowmeter: * Direction of one part of the machine to other is described as downstream/upstream. ### Important Information: * **Downstream**: From cylinder towards common gas outlet. * **Upstream**: From common gas outlet towards cylinder. * O₂ flowmeter should always be downstream to N₂O flowmeter and air flowmeter. ### Vaporizers: * It is a device which stores potent agent in liquid form and vaporize it and add to O₂ and N₂O/air. ### Important Information: * **Color coding for vaporizer:** * Halothane - Red * Isoflurane - Purple * Sevoflurane - Yellow * Desflurane - blue * **Common Gas Outlet:** Breathing system is attached to common gas outlet for final flow of gas out of anesthesia machine. Pressure is kept between 5-8 psi, which is tolerable for human lungs. * **Hypoxia guard**: Safeguards which prevent O₂ concentration to fall below required limit. * **There are 3 hypoxia guards:** 1. Basal O₂ flow of machine - Master switch starts a minimum O₂ flow from machine when it is turned on (25-250ml/min). 2. Link 25 system - N₂O flow control valve is mechanically linked to O₂ flow control valve. 3. O₂ safety alarms - If O₂ concentration falls below certain limit, alarm gets activated. ## ANESTHESIA CIRCUIT: * It is a system which connects anesthesia machine to the patient. * **There are two types:** * Semi closed/Mapleson system * Closed/circle system ### Mapelson System: * Total 6 circuits A to F. * A, B, C, D is adult circuits. * E and F are pediatric circuits. ### Pediatric Circuits: * **Mapleson E Circuit/Ayre's T - piece (inverted T - shaped circuit)** * This circuit is used in pediatric patients. * Bagless and valveless circuit. * This is a useless system because this system has not interpretation for the tidal volume used. * It can be used for spontaneous ventilation but cannot be used for controlled ventilation. * **Mapleson F circuit** * Also, k/a Jackson Rees modification of Ayre's T-piece circuit. * Also, k/a Jackson Rees circuit. * In this system, a bag is attached toward the expiratory end, thus movement of bag is informing about the tidal volume generated by child patient. * Can be used both for spontaneous ventilation and controlled ventilation. ### Refer Table 3.1: * **FGF - Fresh Gas Flow** * **MV - Minute Ventilation** * **For adult in spontaneous ventilation A > D > B = C** * **For adults in controlled ventilation D > B = C > A** * **Thus, for adults** * **Bain's circuit:** - Modified Mapleson D. Also known as Coaxial Mapleson D. Inspiratory limb - Inner. Expiratory limb - Outer. Best for controlled ventilation, second best for spontaneous ventilation. * **Lack's circuit:** - Modified Mapleson A. Also known as coaxial Mapleson A. * **Circle System (CLOSED CIRCUIT)**: - Inspiratory limb and expiratory limb are separate. Unidirectional valve is attached. CO₂ absorber is attached. Circle system is unidirectional flow system with carbon dioxide absorption. ## Drugs For General Anesthesia ### Important Information: * **Advantages of silica:** * Gives hardness to soda lime * Added to prevent dust formation ### Important Information: * For induction we seldom use desflurane because of its irritant property - causes Bronchospasm and Laryngospasm. * Sevoflurane is inhalational induction agent of choice. * Sevoflurane and Desflurane - Both good for day care surgery since they give fast recovery ### Inhalational anesthetic agents: * Commonly used inhalational agents: * **Inorganic Gas:** * N₂O - it is less potent, used as carrier gas. * **Volatile liquids:** * Halothane * Isoflurane * Sevoflurane * Desflurane * **Volatile agents not in clinical use:** * Methoxyflurane - most nephrotoxic * Enflurane - causes epilepsy * **Inert gas:** * Xenon - carrier gas. but due to high cost, currently not in use. ### Important Information: * **MAC - Minimal Alveolar Concentration of the vapor/ anesthetic agent to prevent movement (Motor Response) in 50% of subject in response to surgical stimulus.** * ↑↑ MAC = Potency ↑↑ * MAC = Potency ↑↑ * Least MAC is of Halothane so most potent. ### Blood gas partition co- efficient or blood gas solubility: | | Halothane | Isoflurane | Sevoflurane | Desflurane | |-------|-----------|-----------|-----------|-----------| | | 2.25 | 1.3 | 0.63 | 0.42 | | | | | | | | | | | | | | | | | | | * Fastest speed of induction and recovery * Blood gas partition coefficient * Speed of Induction * Speed of Recovery * Low blood gas partition coefficient - Faster speed of induction and recovery (Vice Versa). ### Refer Table 5.2: | Smell of Agents | Halothane | Isoflurane | Sevoflurane | Desflurane | |---|---|---|---|---| | Smell of Agents | Fruity smell | Little bit irritant | Sweet smell | Imitant (max) | | | Used both for induction & maintenance | Only used for maintenance | Induction & maintenance | Inhalational induction agent of choice | | | | | | | |---|---|---|---|---| | **For maintenance** | | | Isoflurane > sevoflurane | | | | | | (Best is Desflurune) | | ### Pharmacodynamic properties: #### CNS Effects: | CNS Effects | Halothane | Isoflurane | Sevoflurane | Desflurane | |---|---|---|---|---| | | | | | | | | ↓ Cerebral metabolic O₂, ↓ CBF, ↓ ICP | ↓ Cerebral metabolic O₂, ↓ CBF, ↓ ICP | ↓ Cerebral metabolic O₂, ↓ CBF, ↓ ICP | ↓ Cerebral metabolic O₂, ↓ CBF, ↓ ICP | | | | | | | | | CBF increase (maximum) | CBF increase | BF increase | BF increase | | | ↓EEG | ↓EEG | ↓EEG | ↓EEG | ### Important Information: * There is cerebral metabolic O₂ requirement in all. * Inhalational agent are uncouplers of brain. They dilate the cerebral blood vessel - ↑ Cerebral Blood Flow (CBF). * In IV Anesthetic Agent it is opposite. ↓ Cerebral Metabolic O₂ - ↓ CBF. * All inhalational Agent cause ↑ICP (intra cranial pressure). * Halothane not used for Neurosurgery. Rest of the Inhalational agents can be used. * **Best Agent of Neurosurgery - Desflurane** * 2 best agent for Neurosurgery - isoflurane ### Previous Year's Questions: * Maximum airway irritation caused by? * Desflurane * Enflurane * Sevoflurane * Halothane * (NEET Jan 2019) * Which of the following inhalational agents is the induction agent of choice in children? * Methoxyflurane * Sevoflurane * Desflurane * Isoflurane * (Fmge 2018) ### Important Information: * Least cardio depressant - desflurane > sevoflurane > isoflurane. * Best agent for CVS surgery - Desflurane. * Agent most commonly used for CVS surgery - Isoflurane because desflurane is not commonly available. * Sevoflurane not used for prolonged hours. ### Previous Year's Questions: * Which of the following drug is used for hypotensive anesthesia? * Isoflurane * Nitroglycerine * Both 1 and 2 * Dantrolene * (Fmge June 2018) ### Effects on Respiratory system: * All of the inhalational agents are respiratory depressants. * Blunts hypoxic/hypercapnic drive. * All are bronchodilator. * Best bronchodilator - Halothane. * Sevoflurane is also very good bronchodilator, so mostly used in developed countries. ### Effects on liver: * **Refer Table 5.3** ### Important Information: * For liver surgery Desflurane > isoflurane ### Previous Year's Questions: * On repeated use, which of the following inhalational antiesthetic agents can cause hepatitis? * Isoflurane * Halothane * Sevoflurane * Ether * (FMGE June 2019) ### Effects on kidney: | Effects on Kidney | Halothane | Isoflurane | Sevoflurane | Desflurane | |---|---|---|---|---| | | No effect | No effect | Compound - A (Nephrotoxic) | No effect | ### Components of GA: <start_of_image> Areas of the body affected by general anesthesia: * **LOC - Loss of Consciousness** * **LORR - Loss of Reflex Response** * **Amnesia** * **Muscle Relaxation (membrane stabilizing effect)** * **Analgesia** | | LOC | LORR | Amnesia | Muscle Relaxation | Analgesia | |---|---|---|---|---|---| | | Yes | Yes | Yes | Yes | No | | | Yes | Yes | Yes | Yes | No | | | Yes | Yes | Yes | Yes | No | | | Yes | Yes | Yes | Yes | No | ### All halogenated Inhalational Agent: * Lignocaine ### Mechanism: * When a person having gene receives these drugs it gets activated and it stimulates SR which causes massive outflow of calcium inside the cell activating CGMP pathway and this increases the metabolism of our body by 2-3 times. ### Clinical features: * It presents with: * **Hypercapnia** [of 9602] * **Hyperthermia** * **Increased BP** * **Increased HR** * **Arrhythmias** * All occurs due to hypermetabolism and results in cell lysis. And further cause myoglobinuria, acidosis, renal failure, hyperkalemia. ### Management: * Discontinue the triggering Agent. * **Intravenous Dantrolene**: Central Muscle Relaxant. Stops release of Ca++. * **Side Effect**: Respiratory insufficiency and muscle weakness. * **Symptomatic Management** * **Anesthesia safe in Malignant Hyperthermia - TIVA (Total Intravenous Anesthesia) ** * **Propofol - Agent of choice** ### Important Information: * **Skeletal muscle relaxation : desflurane > sevoflurane > isoflurane> halothane.** * **All Inhalational agents provide good muscle relaxation but none of them provide analgesia.** ### Previous Year's Questions: * A patient in OT was given anesthesia (isoflurane, halothane etc) and suddenly developed lung collapse and hypotension. What is the reason for it? * ARDS * Pleural effusion. * Pulmonary oedema * Pneumothorax * (FMGE June 2021) ### Malignant Hyperthermia (MH): * Inhalational agent predisposes to this condition, but IV agents are safe in it. * **Pharmacogenetic Disease** - AD form is expressed. * **Drugs triggering it:** * Succinyl Choline ### Carrier Gas: * **N₂O** * MAC - 104, least potent * Blood gas solubility - 0.45 * **CVS unstable** * sympathetic stimulation * dependent enzyme * ↓ BP * ↑ HR * Peripheral neuropathy. * Megaloblastic anemia * Bone marrow depression ### Important Information: * **Xenon**: * MAC - 70, more potent than N₂O. * 0.11-0.19 (fastest). * **CVS stable** * **Not metabolically inert** * **Environmental pollutant** * **Expands air containing cavity.** ### Important Information: * **All inhalational / Intravenous Agent - Acts on GABA receptor except:** * Xenon * N₂O * Ketamine * N-methyl-D-Aspartate * These three act on NMDA receptor so all are very good analgesics. ### Important Information: * For neuro surgery or patient with history of epilepsy - Avoid ketamine. ### Intravenous Anesthetic Agents: * They are divided into two groups: * Opioids * Non-opioids #### Opioids: * Only used for analgesic property in GA because of side effect * Prolonged Respiratory Depression * CVS stability * Can be used as sole anesthetic only for major CVS compromised patient. * **It includes:** * Morphine * Fentanyl * Sufentanyl * Alfentanil * Remifentanil - BEST - Unique metabolism, by non specific esterase - Ultrashort acting, 3-5 mins half life #### Non Opioids: * **Refer Table 5.4** ### Important Information: * For cvs combromised pt. - All opioids * Non opiods only - Etomidate ### Effect on CNS: | CNS Effects | Thiopentone | Propofol | Etomidate | Ketamine | | | | | | | | | ↓CMRO₂, ↓CBF, ↓ICP | | ↓CMRO₂, ↓CBF, ↓ICP | Sympatho mimetic, ↑CMRO₂, ↑CBF, ↑ICP, ↑EEG | ### Previous Year's Questions: * Drugs does not cause cardiac depression? * Propofol * Ketamine * Etomidate * Thiopentone * (NEET Jan 2019) ### Effect on respiratory system: * **Bronchospastic:** All are Bronchodilator. * **Ketamine - Best Bronchodilator** * **Hepatic/Renal:** no effect on hepatic and renal system, though all drugs are metabolized by them. * **Only propofol has extrahepatic extrarenal route of metabolism.** In case of liver and kidney dysfunctions, propofol can be preferred comparing to rest of the IV anesthetic drugs. ### Agent of choice: * **Refer Table 5.6** ### Previous Year's Questions: * Which of the following is used for day care surgery? * Ketamine * Thiopentone * Propofol * Etomidate * (FMGE Dec 2020) ### Contraindication of use of Intravenous anesthetic Agent: * Refer Table 5.7 ### Previous Year's Questions: * Which of the following is contraindicated in acute intermittent porphyria? * Sodium Thiopentone * Propofol * Ketamine * Etomidate * (FMGE Aug 2020) ### Previous Year's Questions: * Intravenous agent does not causes pain? * Methohexital * Propofol * Ketamine * Etomidate * (NEET Jan 2019) ### Side effects: * **Refer Table 5.8** ### Previous Year's Questions: * Which of the following anesthetic agents causes postoperative delirium and hallucinations? * Ketamine * Propofol * Thiopentone * Etomidate * (FMGE Dec 2020) ### Important Information: * EEG normally after Locs - ↓ B₂B, sympathetic stimulation. * In submarimal MAC - ↑ B₂B. * As age ↑, MAC ↓ by 6% per decade; infants have higher MAC * In Pg-MAC decreases. * Refer Table 5.1 - INHALATIONAL ANESTHETIC AGENTS ### Important Information: * All halogenated Inhalational Agent: Lignocaine * **Mechanism:** When a person having gene receives these drugs it gets activated and it stimulates SR which causes massive outflow of calcium inside the cell activating CGMP pathway and this increases the metabolism of our body by 2-3 times. ### Clinical features: * **It presents with:** * Hypercapnia [of 9602] * Hyperthermia * Increased BP * Increased HR * Arrhythmias * All occurs due to hypermetabolism and results in cell lysis. And further cause myoglobinuria, acidosis, renal failure, hyperkalemia. ### Management: * Discontinue the triggering Agent. * **Intravenous Dantrolene:** Central Muscle Relaxant. Stops release of Ca++. * **Side Effects:** - Respiratory insufficiency and muscle weakness. * **Symptomatic Management** * **Anesthesia safe in Malignant Hyperthermia - TIVA (Total Intravenous Anesthesia)** * **Propofol- Agent of choice** ### Important Information: * Skeletal muscle relaxation: desflurane> sevoflurane> isoflurane> halothane. * All Inhalational agents provide good muscle relaxation but none of them provide analgesia. ### Previous Year's Questions: * A patient in OT was given anesthesia (isoflurane, halothane etc) and suddenly developed lung collapse and hypotension. What is the reason for it? * ARDS * Pleural effusion. * Pulmonary edema * Pneumothorax * (FMGE June 2021) ### Malignant Hyperthermia (MH) * Inhalational agent predisposes to this condition, but IV agents are safe in it. * Pharmacogenetic Disease - AD form is expressed. * Drugs triggering it: * Succinyl Choline ### Carrier Gas: * **N₂O** * MAC - 104, least potent * Blood gas solubility - 0.45 * **CVS unstable** * sympathetic stimulation * dependent enzyme * ↓ BP * ↑ HR * Peripheral neuropathy. * Megaloblastic anemia * Bone marrow depression ### Important Information: * **Xenon** - MAC - 70, more potent than N₂O. 0.11-0.19 (fastest). * **CVS stable**. * **Not metabolically inert**. * **Environmental pollutant** * Expands air containing cavity. ### Important Information: * All inhalational/ Intravenous Agent - Acts on GABA receptor except: * Xenon * N₂O * Ketamine * N-methyl-D-Aspartate * These three act on NMDA receptor so all are very good analgesics. ### Important Information: * For neuro surgery or patient with history of epilepsy - Avoid ketamine. ### Intravenous Anesthetic Agents: * They are divided into two groups: * Opioids * Non-opioids #### Opioids * Only used for analgesic property in GA because of side effect * Prolonged Respiratory Depression * CVS stability * Can be used as sole anesthetic only for major CVS compromised patient. * It includes: * Morphine * Fentanyl * Sufentanyl * Alfentanil * Remifentanil - BEST - Unique metabolism, by non specific esterase - Ultrashort acting, 3-5 mins half life #### Non Opioids: * Refer Table 5.4 ### Effect on CNS: | | Thiopentone | Propofol | Etomidate | Ketamine | |---|---|---|---|---| | | ↓CMRO₂, ↓CBF, ↓ICP | | ↓CMRO₂, ↓CBF, ↓ICP | Sympatho mimetic, ↑CMRO₂, ↑CBF, ↑ICP, ↑EEG | ### Important Information: * For cvs combromised pt