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Key Points  The role of the anesthesiologist has expanded to become the perioperative physician.  The specialties of critical care medicine and pain.

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Presentation on theme: "Key Points  The role of the anesthesiologist has expanded to become the perioperative physician.  The specialties of critical care medicine and pain."— Presentation transcript:


2 Key Points  The role of the anesthesiologist has expanded to become the perioperative physician.  The specialties of critical care medicine and pain medicine have grown out of the expanded field of anesthesiology.  New and improved airway and intubation devices, such as the laryngeal mask airway and the video laryngoscope, have led to improved management and control of routine and difficult airways.

3 Anesthesia  Embodies control of three great concerns of humankind: consciousness, pain, and movement.  Combines the administration of anesthesia with the perioperative management of the patient's concerns, pain management, and critical illness.  The fields of surgery and anesthesiology are truly collaborative and continue to evolve together, enabling the care of sicker patients and rapid recovery from outpatient and minimally invasive procedures.

4 History of Anesthesia  Along with infection control and blood transfusion, anesthesia has enabled surgery to occupy its fundamental place in medicine.  Ether  Nitrous oxide  Chloroform  Cocaine  Barbituates  Halothane, enflurane, isoflurane, sevoflurane  Depolarizing vs non-depolarizing paralytics

5 Pharmacology  The relationship between the dose of a drug and its plasma or tissue concentration.  It is what the body does to the drug. It relates to absorption, distribution, metabolism, and elimination.  The route of administration, metabolism, protein binding, and tissue distribution all affect the pharmacokinetics of a particular drug.

6 Pharmacokinetics  Administration of a drug affects its pharmacokinetics, as there will be different rates of drug entry into the circulation.  Distribution is the delivery of a drug from the systemic circulation to the tissues.  Molecular size of the drug, capillary permeability, polarity, and lipid solubility.  Plasma protein and tissue binding.  The fluid volume in which a drug distributes is termed the volume of distribution (Vd).  Metabolism is the permanent breakdown of original compounds into smaller metabolites.

7 Pharmacodynamics  Pharmacodynamics, or how the plasma concentration of a drug translates into its effect on the body, depends on biologic variability, receptor physiology, and clinical evaluations of the actual drug.  An agonist is a drug that causes a response.  A full agonist produces the full tissue response, and a partial agonist provokes less than the maximum response induced by a full agonist.  An antagonist is a drug that does not provoke a response itself, but blocks agonist-mediated responses.  An additive effect means that a second drug acts with the first drug and will produce an effect that is equal to the algebraic summation of both drugs.  A synergistic effect means that two drugs interact to produce an effect that is greater than expected from the two drugs' algebraic summation.

8 Pharmacodynamics  The potency of a drug is the dose required to produce a given effect.  The efficacy of any therapeutic agent is its power to produce a desired effect.  Dose-response curves show the relationship between the dose of a drug administered and the pharmacologic effect of the drug.  The effective dose (ED 50 ) would have the desired effect in 50% of the general population.  The lethal dose (LD 50 ) of a drug produces death in 50% of animals to which it is given.  The ratio of the lethal dose and effective dose, LD 50 /ED 50, is the therapeutic index.

9 Table 47-1 Anesthetic Agents, Their Actions, and Their Clinical Uses

10 Local Anesthetics  Local anesthetics are divided into two groups based on their chemical structure: the amides and the esters.  Lidocaine, bupivacaine, mepivacaine, prilocaine, and ropivacaine have in common an amide  Lidocaine has a more rapid onset and is shorter acting than bupivacaine; however, both are widely used for tissue infiltration, regional nerve blocks, and spinal and epidural anesthesia.  Cocaine, procaine, chloroprocaine, tetracaine, and benzocaine have an ester linkage  The common characteristic of all local anesthetics is a reversible block of the transmission of neural impulses when placed on or near a nerve membrane.  Local anesthetics block nerve conduction by stabilizing sodium channels in their closed state, preventing action potentials from propagating along the nerve.

11 Local Anesthetic Toxicity  CNS – tinnitus, slurred speech, seizures, and unconsciousness  CV - hypotension, increased P-R intervals, bradycardia, and cardiac arrest  Bupivacaine 3 mg/kg  Lidocaine 5 mg/kg  Epinephrine is a vasoconstrictor, reduces local bleeding, and keeps local anesthetic in the nerve proximity for a longer period of time.  Onset of the nerve block is faster  Quality of the block is improved  Duration is longer  Less local anesthetic absorbed in bloodstream – reducing toxicity

12 Spinal Anesthesia  Injected directly into the dural sac surrounding the spinal cord  Possible complications include hypotension, especially if the patient is not adequately prehydrated  High spinal block requires immediate airway management  Spinal headache is related to the diameter and configuration of the spinal needle, and can be reduced to approximately 1%

13 Epidural Anesthesia  Local anesthetics are injected into the epidural space surrounding the dural sac of the spinal cord  Achieves analgesia from the sensory block, muscle relaxation from blockade of the motor nerves, and hypotension from blockade of the sympathetic nerves as they exit the spinal cord  Provides only two of the three major components of anesthesia—analgesia and muscle relaxation  Anxiolysis, amnesia, or sedation must be attained by supplemental IV administration of other drugs  Complications are similar to those of spinal anesthesia

14 General Anesthesia  A triad of three major and separate effects: unconsciousness (and amnesia), analgesia, and muscle relaxation  A combination of IV and inhaled drugs

15 Intravenous agents  IV agents that produce unconsciousness and amnesia are frequently used for the induction of general anesthesia.  They include barbiturates, benzodiazepines, propofol, etomidate, ketamine.  Barbiturates are anticonvulsant & decrease cerebral metabolism  Propofol has short duration and rapid recovery  Benzos reduce anxiety and produce amnesia  Etomidate has rapid induction and awakening  Ketamine produces analgesia and amnesia

16 Analgesia  Narcotic  Non-narcotic  Toradol  Ketamine

17 Neuromuscular Blocking Agents  Depolarizing – Succinylcholine  Rapid onset and offset  Non-depolarizing  Pancuronium – long acting  Rocuronium, vecuronium, cis-atracuronium – intermediate  Reversed by neostigmine, edrophonium, pyridostigmine

18 Inhalational Agents  Provide all three characteristics of general anesthesia: unconsciousness, analgesia, and muscle relaxation  A dose-dependent reduction in mean arterial blood pressure  Minimum alveolar concentration (MAC) is a measure of anesthetic potency  The ED 50 of an inhaled agent  The higher the MAC, the less potent an agent is

19 Intraoperative Management

20 Pre-op evaluation  The detailed medical history  The physical examination is targeted primarily at the CNS, cardiovascular system, lungs, and upper airway  Concurrent medications  Preoperative laboratory data and specific testing for elective surgery should be patient- and situation- specific

21 Risk Assessment  An integral part of the preoperative visit is for the anesthesiologist to assess patient risk.  Risk assessment encompasses two major questions: (a) Is the patient in optimal medical condition for surgery? and (b) Are the anticipated benefits of surgery greater than the surgical and anesthetic risks associated with the procedure?  Research into factors that correlate with the development of postoperative morbidity and mortality has recently gained great interest

22 Risk Assessment  Table 47-6 American Society of Anesthesiologists Physical Status Classification System  P1 A normal healthy patient  P2 A patient with mild systemic disease  P3 A patient with severe systemic disease  P4 A patient with severe systemic disease that is a constant threat to life  P5 A moribund patient who is not expected to survive without the operation  P6 A declared brain-dead patient whose organs are being removed for donor purposes

23 Mallampati Classification

24 Comorbidities  Ascertain the patient's severity, progression, and functional limitations induced by ischemic heart disease or pre-existing CAD  Infection, noxious particles, and gases can exacerbate COPD  However, anesthetic techniques have improved, and it has been shown that patients with severe lung disease can safely undergo anesthesia  Virtually all anesthetic drugs and techniques are associated with decreases in renal blood flow, the glomerular filtration rate, and urine output

25 Comorbidities  The patient with liver disease requires an understanding of the many physiologic functions of the liver: synthesis of albumin, coagulation factors, metabolism of drugs  may influence the selection of volatile anesthetics  The three metabolic and endocrine conditions that are most prevalent in patients undergoing surgery are diabetes mellitus, hypothyroidism, and obesity  Patients with diabetes are at an increased risk for perioperative myocardial ischemia, stroke, renal dysfunction or failure, and increased mortality  Increased wound infections and impairment of wound healing also is associated with the pre-existence of diabetes in patients undergoing surgery

26 Airway Mgmt Algorithm



29 Malignant Hyperthermia  MH is a life-threatening, acute disorder, developing during or after general anesthesia  genetic predisposition  Triggering agents include all volatile anesthetics and the depolarizing muscle relaxant succinylcholine  The classic MH crisis entails a hypermetabolic state, tachycardia, and the elevation of end-tidal CO 2 in the face of constant minute ventilation  Respiratory and metabolic acidosis and muscle rigidity follow, as well as rhabdomyolysis, arrhythmias, hyperkalemia, and sudden cardiac arrest  A rise in temperature is often a late sign of MH

30 Malignant Hyperthermia  Treatment must be aggressive and begin as soon as a case of MH is suspected  Stop all volatile anesthetics and give 100% O 2  Hyperventilate the patient up to three times the calculated minute volume  Begin infusion of dantrolene sodium 2.5mg/kg IV  Repeat as necessary to titrate for clinical signs  Continue dantrolene for atleast 24 hours  Give bicarbonate to treat acidosis if dantrolene ineffective  Treat hyperkalemia with insulin, glucose, and calcium  Avoid calcium channel blockers reat hyperkalemia with insulin, glucose, and calcium  Continue to monitor core temperature  Call MH hotline

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