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1、ANESTHESIA:OVERVIEWAnesthesia is the use of medications and close monitoring to provide comfort and maintain vital life functions during surgery or other medical procedures.Anesthesia is concerned not only with the administration of anesthesia for surgery but also with many other areas of patient ca

2、re,including critical care medicine,management of chronic pain,and respiratory therapy.Anesthesia:reversible,drug-induced loss of sensation in the entire body or in a part of itLocal anesthetic agents:agents that block sensory andmotor nerve conduction to produce temporary loss ofsensation without a

3、 loss of consciousnessGeneral anesthetics:CNS depressants with action that canbe induced and terminated more rapidly than sedative hypnoticsPreanesthetic medication:may include sedatives,opioids,tranquilizers and anticholinergic agentsWhat determines the type of anesthesia used?Your medical history.

4、The results of your physical exam.This is done to evaluate your current health and identify any potential risks or complications that may affect your anesthesia care.The results of tests such as blood tests or an electrocardiogramThe reason for your surgery and the type of surgery.Physical status cl

5、assification of the American society of AnestheriologistclassPhysical status1Patient has no organic physiologic,biochemical,or psychiatric disturbance2Patient has mild to moderate systemic disturbances that or may not be related to the disorder requiring surgery(eg,essential hypertension,diabetes me

6、llitus)3Patient has severe systemic disturbances that may or may not be related to the disorder requiring surgery(eg,heart disease that limits activity,poorly controlled essential hypertension)4Patient has severe systemic disturbance that is lifethreatening with or without surgery(eg,congestive hear

7、t failure,persistent angine pectoris)5Patient is moribund and has little chance for survival,but surgery is to be performed as a last resort(resuscitative effort)(eg,uncontrolled hemorrhage,as from a ruptured abdominal aneurysm)EPatient requires emergency operationAnesthesia is divided into four bas

8、ic categories:general anesthesia regional anesthesia local anesthesia sedation Today we just learnToday we just learn General anesthesiaGeneral anesthesia There are several drugs and gases that can be combined or used alone to produce general anesthesia.When anesthetics reach the bloodstream,the dru

9、gs that affect the brain pass through other blood vessels and organs so they are often affected too.Therefore,patients must be carefully monitored.General anesthesia is used for more extensive procedures or for procedures that arent amenable to regional anesthesia.The medications used in general ane

10、sthesia are given intravenously or by inhalation.The drugs circulate in your bloodstream to all areas of your body,including your brain.It results in amnesia,paralysis and analgesia.They can suppress all of your protective reflexes,such as coughing,gagging and even breathing.Consequently,a general a

11、nesthetic requires the use of a mask or breathing tube during the surgery.Inhaled General AnestheticsNitrous oxide Halothane Enflurane Isoflurane Sevoflurane Desflurane Xenon(rarely used)Anesthesia MachineIV General Anesthetics and Sedative AgentsThiopental Methohexital Propofol Etomidate Ketamine D

12、iazepam Midazolam Lorazepam These drugs quickly reach the brain and their effect is dependent on several factors including the volume in which the drug is distributed in the body,the fat-solubility of the drug,and how quickly the body eliminates the drug.It is not completely clear exactly how genera

13、l anesthetics work at a cellular level,but it is speculated that general anesthetics affect the spinal cord(resulting in immobility),the brain-stem reticular activating system(resulting in unconsciousness)and the cerebral cortex(seen as changes in electrical activity on an electroencephalogram).Four

14、 stages of Anesthesia and increasing depth of CNS depression1.Analgesia:awareness of pain without amnesia2.Excitement:delirium and excited with amnesia3.Surgical anesthesia:unconscious,no pain reflexes,regular respiration and BP maintained4.Medullary depression:severe respiratory and CVdepression;de

15、ath without CV and respiratory supportSTAGE RESPIRATION EYES PUPILREFLEXONE-AnalgesiaRegular small volumeCentral smallTwo-excitementirregularDivergent largeEyelash absentThree-anesthesiaPlane IRegular large volumeCentral smallEyelid absent and conjunctival depressedPlane IIRegular large volumeCentra

16、l mediumCorneal depressedPlane IIIRegular becoming diaphragmatic,small volumeCentral mediumLaryngeal depressedPlane IVIrreg diaphragmatic small volumeCentral largeCarinal depressedFour-overdoseapneaCentral full dilatationCardiac depressedCurved(Macintosh)1.The tip of the blade is advance into the sp

17、ace between the base of the tongue and the pharyngeal surface of the epiglottis.2.Move the blade forward and upward to elevate the epiglottis and expose the glottic opening.Straight(Jackson-Wisconsin)or Straight with curved tip(Miller)1.The tip of the blade is passed beneath the laryngeal surface of

18、 the epiglottis 2.Same with curve bladeAnesthesia Monitors monitoring of heart rate(ECG),oxygen saturation(pulse oximetry)blood pressure(NIBP&IBP arterial)inspired and expired gases(for oxygen,nitrous oxide,carbon dioxide,and volatile agents)monitoring of temperaturecentral venous pressurecerebral a

19、ctivity(EEG)neuromuscular activity(peripheral nerve stimulation monitoring)urine outputblood sugar levels buildup of exhaled inhalational anesthetics MONITORSBlood pressure monitoringNIBP using automated device;size of cuff should cover 2/3 of arm.Too wide cuff can produce false low BP while too sma

20、ll cuff can cause false high BP.IBP via arterial line to determine real time BP ECGLead II aids in recognition of changes in cardiac rhythm and Lead V aids in recognition of ischemia.It can also show changes that may suggest electrolyte imbalance.Pulse oximetryReads oxygen saturation of blood via sp

21、ectrophotometry.High levels of carbon monoxide can cause false high saturation values while color dyes on nails can cause false low saturation values.Capnography/End tidal carbon dioxideCarbon dioxide levels in blood reflects the dead space ventilation.Reading can also aid in verifying correct place

22、ment of the ET tube,presence of spontaneous respiration,presence of airway obstruction.Thermometer Prevention of hypothermia can improve anesthesia outcome.Probes for esophageal,rectal,bladder,skin&tympanic membrane are available.An important property of anesthetics is reversibility.When the surgery

23、 is over,the anesthesiologist would shut off the anesthetic and have the patient wake up from the anesthetic-induced sleep.Once the anesthetic gas is turned off,the blood stream brings the gas back to the lungs where it is eliminated.The more soluble the gas is in blood,the longer it takes to elimin

24、ate.Nitrous oxide and desflurane are the shortest-acting anesthetic gases because they are the least soluble in blood.Muscle RelaxantsSuccinylcholine(Anectine)-depolarizingVecuronium(Norcuron)non depolarizing intermediate actingRocuronium(Esmeron)non depolarizing intermediate actingPancuronium(Pavul

25、on)non depolarizing long actingAtracurium(Tracrium)-non depolarizing intermediate actingPipecuronium Rapacuronium Mivacurium Cisatracurium Curare,the active ingredient of which is tubocurarine Metocurine Gallamine Adverse effects of muscle relaxants Succinylcholine may cause hyperkalemia if given to

26、 burn patients,or paralysed(quadraplegic,paraplegic)patients.Succinylcholine may also trigger malignant hyperthermia in susceptible patients.Neuromuscular blockade can not be reversedOpioidsMorphine Diamorphine,(diacetyl morphine,also known as heroin)Codeine,(methyl morphine)Fentanyl(Sublimaze,Durog

27、esic)Alfentanil Sufentanil Remifentanil Meperidine,also called pethidine(Demerol)Methadone Oxycodone(Oxycontin)Naloxone,chemically similar to some analgesics;not a painkiller and reverses the effects of morphine-like agents.Nalbuphine(Nubain)Butorphanol(Stadol)Side effects of OpioidsAnalgesiaRespira

28、tory depressionIleus/delayed gastric motilityNausea&vomiting Hypotension Pruritus What happens during recovery from anesthesia?PACU/Recovery RoomDrowsiness and Respiratory DepressionNumbness&Residual muscle relaxantHypothermia&ShiveringNausea&VomitingPain&AgitationUnstable vital signs and Hypotension Tomorrow Begins Today!Thank you