Clinical Implication of General Anaesthetics Agents

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IMPLICATIONS OF ANESTHESIOLOGY:

IMPLICATIONS OF ANESTHESIOLOGY Dr Lokendra Sharma Professor Department of Pharmacology SMS Medical College Jaipur Dr Adhokshaj Joshi Assistant Professor Department of Anasthesia SMS Medical College Jaipur

OBJECTIVES:

OBJECTIVES During your short exposure to this specialty we hope to give you some idea of the true scope of anesthesia; It encompasses many areas of medicine as well as clinical physiology and pharmacology. Anesthesiologists learn to use technical and analytical skills to look after patients in many situations – some are routine and others very challenging. Anesthesiologists must also hone their humanitarian skills, since patients coming to the OR are often at their most vulnerable.

Goals and objectives:

Goals and objectives Academic and Clinical skills: Preoperative evaluation, preparation and clinical skills Airway and ventilation Fluid and volume resuscitation, electrolyte balance and acid-base Pharmacology of anesthetic drugs Principles of general anesthesia Principles of regional anesthesia Pain management Monitoring in anesthesia Intra operative management and problems Post operative management

Preoperative evaluation and Clinical skills:

Students should be able to: Obtain a relevant medical, surgical and anesthetic history and perform a focused pre-operative examination on the patient. ( Airway assessment, and awareness of factors predisposing to difficult intubation are of particular importance.). Have some understanding of the indications for both routine and special pre-operative investigations. Understand the basis of an anesthetic plan Preoperative evaluation and Clinical skills

Setup ? :

Setup ?

Airway and ventilation :

Airway and ventilation Know the anatomy of the airway and basic airway assessment. Be familiar with the various techniques of airway management and equipment involved in routine and difficult intubation. Review basic respiratory physiology in the context of anesthesia. Be familiar with the principles of manual and mechanical ventilation.

Fluid and electrolyte balance:

Fluid and electrolyte balance Know the main principles of: Fluid replacement and volume resuscitation (crystalloid, colloid, blood transfusion) Electrolyte and acid-base balance

Pharmacology of anesthetic drugs :

Pharmacology of anesthetic drugs Have a basic knowledge of the pharmacokinetic and pharmacodynamic principles of drugs commonly involved in anesthesia including: Intravenous agents (sedative/ hypnotics, narcotics, muscle relaxants) Volatile agents. Local anesthetics

Principles of general Anesthesia:

Principles of general Anesthesia Understand the principles of general anesthesia and the delivery of volatile anesthetics. Have a basic understanding of the structure, function and safety features of the anesthesia machine.

Regional anesthesia and Pain management:

Regional anesthesia and Pain management Be familiar with the concept of local and regional anesthesia and commonly used local anesthetic agents. Be familiar with perioperative pain management techniques and drugs.

Intraoperative Monitoring:

Intraoperative Monitoring

Monitoring In anesthesia:

Monitoring In anesthesia Be familiar with the major monitoring standards and be able to interpret basic information gained from the monitoring of: Blood pressure Pulse oximetry ECG Capnography Ventilation (parameters, spirometry) Temperature Invasive pressure monitoring ( CVP, arterial line)

(1) ECG:

(1) ECG

(2) SpO2:

(2) SpO 2

(3) Blood Pressure:

(3) Blood Pressure

Intraoperative monitoring: (3) BP:

Intraoperative monitoring : (3) BP IBP : (invasive arterial blood pressure monitoring) It is beat to beat monitoring of ABP via an arterial cannula. Indicated in: major surgeries, during deliberate hypotensive anesthesia, during the use of inotropes, cardiac surgery, in surgeries involving extreme hemodynamic changes/instability eg. pheochromocytoma, repeated ABG sampling.

(4) Capnography (CO2):

(4) Capnography (CO2)

(A) Correct Position of ETT:

(A) Correct Position of ETT

(B) Respiratory Monitoring:

(B) Respiratory Monitoring Respiratory Monitors : O2 Saturation. Capnography EtCO2. Airway pressure. ABG samples.

Intra and post operative management:

Intra and post operative management Gain an appreciation for the basic management of common intra-operative problems such as: Hypoxia, hypercarbia, Hyper/hypotension, cardiac arrhythmias, High and low airway pressure alarm. Have an understanding of the requirements for safe emergence from general anesthesia and common problems and complications in the PORR. Post –op nausea and vomiting, pain etc.

Questions : General Anesthetics:

Questions : General Anesthetics

Q1.State which stage of anesthesia each of the following descriptions refers to? Delirium; violent behavior; increased blood pressure; increased respiratory rate; irregular breathing rate and volume; amnesia; retching and vomiting with stimulation; disconjugate gaze:

Q1.State which stage of anesthesia each of the following descriptions refers to? Delirium; violent behavior; increased blood pressure; increased respiratory rate; irregular breathing rate and volume; amnesia; retching and vomiting with stimulation; disconjugate gaze Stage II (excitement)

Q2.Depression of vasomotor center; depression of respiratory center; death may occur:

Q2.Depression of vasomotor center; depression of respiratory center; death may occur Stage IV ( medullary depression) Q3.Eye movements cease; fixed pupils; regular respiration; relaxation of skeletal muscles Stage III (surgical anesthesia) Q4.Loss of pain sensation; patient is conscious; no amnesia in early part of this stage Stage I (analgesia)

Q5.Give examples of inhaled anesthetics::

Q5.Give examples of inhaled anesthetics: Halothane; nitrous oxide; isoflurane; enflurane; sevoflurane; desflurane; methoxyflurane Q6.With regard to inhaled anesthetics, what does MAC stand for? Minimum alveolar concentration. Note: this is not to be confused with monitored anesthesia care also commonly referred to as MAC, which is a combination of regional anesthesia, sedation, and analgesia.

Q7.What is MAC in regard to inhaled anesthetics?:

Q7.What is MAC in regard to inhaled anesthetics? The concentration of inhaled anesthetic required to stop movement in 50% of patients given a standardized skin incision; a measure of potency for inhaled anesthetics

Q8.For potent inhaled anesthetics, is the MAC small or large?:

Q8.For potent inhaled anesthetics, is the MAC small or large? Small (inverse of the MAC is used as an index of potency for inhaled anesthetics) Q9.Which inhaled anesthetic has the largest MAC? Nitrous oxide (>100%) Q10.Which inhaled anesthetic has the smallest MAC? Halothane (0.75%)

Q11.As lipid solubility of an inhaled anesthetic increases, what happens to the concentration of inhaled anesthetic needed to produce anesthesia does it increase or decrease?:

Q11.As lipid solubility of an inhaled anesthetic increases, what happens to the concentration of inhaled anesthetic needed to produce anesthesia does it increase or decrease? It decreases.

Q12.What is the blood/gas partition coefficient?:

Q12.What is the blood/gas partition coefficient? The ratio of the total amount of gas in the blood relative to the gas equilibrium phase. It refers to an inhaled anesthetic’s solubility in the blood. Q13.If an inhaled anesthetic has a high blood/gas partition coefficient, will times of induction and recovery be increased or decreased? It will be increased because the time to increase arterial tension is longer.

Q 14.Give an example of an inhaled anesthetic with a low blood/gas partition coefficient (low blood solubility)::

Q 14.Give an example of an inhaled anesthetic with a low blood/gas partition coefficient (low blood solubility): Nitrous oxide (0.5); desflurane (0.4) Q 15.Give an example of an inhaled anesthetic with a high blood/gas partition coefficient (high blood solubility): Halothane (2.3); enflurane (1.8) Q 16.Which inhaled anesthetic, halothane or nitrous oxide, will take longer to change the depth of anesthesia when the concentration of the inhaled anesthetic has been changed? Halothane

Q17.Are MAC values additive?:

Q17.Are MAC values additive? Yes Q18.Are MAC values higher or lower in elderly patients? Ans :They are lower, thus elderly patients generally require lower concentrations of inhaled anesthetics. Q19.Are MAC values higher or lower when opioid analgesics and/or sedative hypnotics are used concomitantly? Ans :They are lower.

Q 20.Do inhaled anesthetics increase or decrease the response to Pco2 levels?:

Q 20.Do inhaled anesthetics increase or decrease the response to Pco2 levels? Ans :Decrease Q 21. Do inhaled anesthetics increase or decrease cerebral vascular flow? Ans: Increase Q 22. Do inhaled anesthetics increase or decrease intracranial pressure? Ans: Increase Q 23.Do inhaled anesthetics relax or strengthen uterine smooth muscle contractions? Ans: Relax (except methoxyflurane when briefly inhaled, therefore, can be used during childbirth)

Q 24.Which of the inhaled anesthetics is not a halogenated hydrocarbon?:

Q 24.Which of the inhaled anesthetics is not a halogenated hydrocarbon? Nitrous oxide Q 25. Are the inhaled halogenated hydrocarbon anesthetics volatile or nonvolatile gases? Volatile gases Q 26.Which inhaled anesthetic is associated with malignant hyperthermia? Halothane Q 27.What characterizes malignant hyperthermia? Hyperthermia; muscle rigidity; acidosis; hypertension; hyperkalemia

Q 28a.Should a patient with a family history positive for malignant hyperthermia be concerned?:

Q 28a.Should a patient with a family history positive for malignant hyperthermia be concerned? Yes, because a genetic defect in ryanodine receptors may be inherited. Q 28b.What drug is given to treat malignant hyperthermia? Dantrolene

Q 29.Which inhaled anesthetic is associated with increased bronchiolar secretions?:

Q 29.Which inhaled anesthetic is associated with increased bronchiolar secretions? Isoflurane Q.30.Which inhaled anesthetic is associated with hepatitis? Halothane Q 31.Halothane is not hepatotoxic in what patient population? Pediatric patients Q 32.Which inhaled anesthetic is the least hepatotoxic? Ans: Nitrous oxide

Q 33.Which inhaled anesthetic is associated with increased bronchiolar spasms?:

Q 33.Which inhaled anesthetic is associated with increased bronchiolar spasms? Isoflurane Q 34.Which inhaled anesthetic relaxes bronchial smooth muscle? Halothane Q 35.Which inhaled anesthetic is associated with cardiac arrhythmias? Halothane Q 36.Which inhaled anesthetics increase heart rate (via reflex secondary to vasodilation)? Isoflurane; desflurane

Q 37.Which inhaled anesthetics decrease heart rate?:

Q 37.Which inhaled anesthetics decrease heart rate? Halothane; enflurane; sevoflurane Q 38.Which inhaled anesthetic decreases renal and hepatic blood flow? Halothane Q.39 Give examples of intravenous (IV) anesthetics: Propofol; fentanyl; ketamine; midazolam; thiopental; etomidate Q 40.Which of the previously mentioned IV anesthetics is a barbiturate? Thiopental

Q 41.Which of the previously mentioned IV anesthetics is a benzodiazepine?:

Q 41.Which of the previously mentioned IV anesthetics is a benzodiazepine? Midazolam Q 42. Which of the previously mentioned IV anesthetics is an opioid? Fentanyl Q 43. Is thiopental used for induction, maintenance, or both? Induction Q 44.Pharmacodynamically, how does recovery occur with the rapid-acting barbiturates? Rapid redistribution from the central nervous system (CNS) to peripheral tissues

Q 45. State whether thiopental increases, decreases, or does not change each of the following physiologic effects::

Q 45. State whether thiopental increases, decreases, or does not change each of the following physiologic effects: Cerebral blood flow No change Respiratory function Decreases Blood pressure Decreases

Q 46. Why should caution be taken when administering thiopental to asthmatic patients?:

Q 46. Why should caution be taken when administering thiopental to asthmatic patients? May cause laryngospasm Q 47.Midazolam offers which type of amnesia making it useful for monitored anesthesia care? Anterograde amnesia Q 48.What is the antidote for midazolam-induced respiratory depression? Flumazenil, which is also the antidote for any benzodiazepine overdose

Q 49.What adverse drug reaction may be caused by fentanyl when given intravenously?:

Q 49.What adverse drug reaction may be caused by fentanyl when given intravenously? Chest wall rigidity Q 50.Does propofol have good analgesic properties? No

Q 51.About which allergies should a patient be questioned before administration of propofol?:

Q 51.About which allergies should a patient be questioned before administration of propofol? Egg and soybeans. Propofol is prepared as a lipid emulsion using egg and soybean lecithin. T his gives propofol its white color and can cause allergic reactions in patients with sensitivities to these substances. Q 52.Does propofol increase or decrease blood pressure? It decreases blood pressure Q 53. Is propofol used for induction, maintenance, or both? It is used for both.

Q 54. Which IV anesthetic causes dissociative anesthesia?:

Q 54. Which IV anesthetic causes dissociative anesthesia? Ans: Ketamine Q 55.What is dissociative anesthesia? The patient is unconscious and feels no pain, yet appears awake. Eyes may open and the swallowing reflex is present, but the patient is sedated, immobile, and usually amnestic. Hallucinations and delirium are common.

Q 56.Which anesthetic has antiemetic properties?:

Q 56.Which anesthetic has antiemetic properties? Propofol Q 57.Which IV anesthetic is a cardiovascular stimulant (increases blood pressure and cardiac output)? Ketamine Q 58. Which IV anesthetic causes vivid dreams and hallucinations? Ketamine

Q 59.Does ketamine increase or decrease cerebral blood flow?:

Q 59.Does ketamine increase or decrease cerebral blood flow? Increase Q 60.What is the most cardiac-stable IV anesthetic agent? Etomidate Q 61 Total intravenous anesthesia (TIVA) ? Ans: It is a technique of general anesthesia which uses a combination of agents given exclusively by the intravenous route without the use of inhalation agents

Q 62 a Total intravenous anesthesia (TIVA) ?:

Q 62 a Total intravenous anesthesia (TIVA) ? TIVA offers several potential advantages .: Reduced incidence of post-operative nausea and vomiting Reduced atmospheric pollution, more predictable and rapid recovery Greater hemodynamic stability Preservation of hypoxic pulmonary vasoconstriction Reduction in intracerebral pressure and reduced risk of organ toxicity.

Q 62 b Total intravenous anesthesia (TIVA) Why Popular ?:

Q 62 b Total intravenous anesthesia (TIVA) Why Popular ? Firstly, the PK & PD properties of drugs such as Propofol and newer short-acting opioids, which make them suitable for intravenous administration. Secondly, new concepts in pharmacokinetic modeling coupled with advances in the technology of infusion pumps which allow the use of algorithms such as Target Controlled Infusion

Q 62 c Specific indications of TIVA:

Q 62 c Specific indications of TIVA A stress-free awake extubation free of laryngospasm is required. Malignant hyperthermia risk  Long QT syndrome (QTc ≥ 500 ms)  ‘Tubeless’ ENT and thoracic surgery  Patients with anticipated difficult intubation/extubation  Neurosurgery—to limit intracranial volume 

Q 63 Specific indications of TIVA:

Q 63 Specific indications of TIVA Surgery requiring neurophysiological monitoring Myasthenia gravis/neuromuscular disorders, and situations where NMBs are of disadvantage  Anaesthesia in non-theatre environments Transfer of an anaesthetised patient between environments Daycare surgery Trainee teaching Patient choice

Q 64 TCI ?:

Q 64 TCI ? Technique of infusing IV drugs to achieve a user-defined predicted (“target”) drug concentration in a specific body compartment or tissue of interest 

Q 65 What is the role of TCI in TIVA ?:

Q 65 What is the role of TCI in TIVA ? Highly effective drug synergy allows the choice of high propofol/low remifentanil effect-site concentrations. The use of a low propofol/high remifentanil combination allows more rapid recovery but is associated with apnoea and the need for assisted ventilation.   Q 66 Problems with TIVA ? Awareness Morbid obesity Analgesia and hyperalgesia Propofol infusion syndrome

Q 67 a Remimazolam ? :

Q 67 a Remimazolam ? Remimazolam is an ultra-short-acting intravenous benzodiazepine sedative/anesthetic that has already shown positive results in clinical Phase III trials. In the human body, remimazolam is rapidly metabolized to an inactive metabolite by tissue esterases and not metabolized by cytochrome-dependent hepatic pathways.

Q 67 b Remimazolam:

Q 67 b Remimazolam It acts on GABA receptors like midazolam organ-independent metabolism like remifentanil –Liver and renal friendly.propensity for apnoea is low. Remimazolam BDZ or opiod -It is a BDZ. Mech of action of Remimazolam -GABA agonist(GABA alpha). Metabolism of Remimazolam - Ester dependant hydrolysis. Specific antagonist - Flumazenil

Q 68 Possibility of Remimazolam in TIVA-:

Q 68 Possibility of Remimazolam in TIVA -  Like propofol, remimazolam is a GABA agonist and produces dose-dependent and measurable hypnosis. Its unique metabolism (ester-dependent hydrolysis) would ensure that accumulation will not occur after prolonged infusion. It is also reversed by flumazenil. 

Q 69 What are Possible clinical uses (Remimazolam) ? :

Q 69 What are Possible clinical uses ( Remimazolam ) ? Single dose for premedication Bolus followed by supplemental doses for procedural sedation. Intravenous anesthetic along with an opioid (as part of TIVA). Intensive care unit (ICU) sedation

Q 70 Xenon ?:

Q 70 Xenon ? Xenon inhibits the plasma membrane Ca 2+ pump,   an action similar to that of volatile anesthetics, which may be responsible for an increase in neuronal Ca 2+ concentrations and altered excitability. Xenon seems to inhibit the nociceptive responsiveness of spinal dorsal horn neurons an effect that may be mediated by inhibition of  N   -methyl-D- aspartate receptors.

Q 71 what are the Advantages of Xenon:

Q 71 what are the Advantages of Xenon  Rapid induction and emergence Asufficient analgesic and hypnotic effect in a mixture with 30% oxygen The absence of metabolism, undisturbed ventilation and pulmonary function Lack of triggering of malignant hyperthermia,CVS stability

Q 72 Propofol ?:

Q 72 Propofol ? It is currently the only intravenously active hypnotic agent suitable for the induction & maintenance of anesthesia. Rapid recovery of consciousness and psychomotor function Enhanced recovery speed Anti-emetic effect Lower incidence of post-operative nausea and vomiting

Q 73 Continuous flow (Boyle’s) anaesthetic machine ?:

Q 73 Continuous flow (Boyle’s) anaesthetic machine ? Anaesthetic Machine (Boyle’s equipment) The anaesthetic machine Gas source- either piped gas or supplied in cylinders Flow meter Vaporisers Delivery System or circuit

Q 74 Inhalational agent which reduces arterial pressure and HR :

Q 74 Inhalational agent which reduces arterial pressure and HR Ans :HALOTHANE Q .75 Inhalational agent which causes centrally mediated sympathetic activation leading to a rise in BP&HR Ans :DESFLURANE Q .76 Inhalational agent which decreases the ventilator response to hypoxia? Ans :Nitrous oxide Q .77 Inhalational agent causing max airway irritation. Ans: DESFLURANE. Q .78 Inhalational agent which cause least increase in cerebral blood flow? Ans : Nitrous oxide

Q 79 IV anesthetic with antiemetic action. :

Q 79 IV anesthetic with antiemetic action. Ans: PROPOFOL. Q 80 IV agent with minimal CVS and respiratory depressant effects. Ans: ETOMIDATE. Q:81 IV agent causing increased cerebral oxygen consumption. Ans KETAMINE. Q:82 IV induction agent of choice in LSCS. Ans :THIOPENTONE. Q:83 IV agent of choice in asthmatic patient Ans :KETAMINE.

Q 84 Propofol infusion syndrome:

Q 84 Propofol infusion syndrome Long Term Infusion(>48 Hrs) Dose(>5mg/Kg/Hr)-rhabdomyolysis, metabolic Acidosis hemodynamic Instability Hepatomegaly multiorgan Failure

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