ANESTHESIAOVERVIEW

ANESTHESIA:OVERVIEW,Anesthesia 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 care, 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 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 agents,What determines the type of anesthesia used?,Your medical history. 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 classification of the American society of Anestheriologist,Anesthesia is divided into four basic categories: general anesthesia regional anesthesia local anesthesia sedation,Today we just learn General anesthesia,There are several drugs and gases that can be combined or used alone to produce general anesthesia. When anesthetics reach the bloodstream, the drugs 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 anesthesia 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 anesthetic requires the use of a mask or breathing tube during the surgery.,Inhaled General Anesthetics,Nitrous oxide Halothane Enflurane Isoflurane Sevoflurane Desflurane Xenon (rarely used),Anesthesia Machine,IV General Anesthetics and Sedative Agents,Thiopental Methohexital Propofol Etomidate Ketamine Diazepam 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 general 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 stages of Anesthesia and increasing depth of CNS depression,1. 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; death without CV and respiratory support,Curved (Macintosh)1.The tip of the blade is advance into the space 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 the epiglottis 2. Same with curve blade,Anesthesia 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 activity (EEG)neuromuscular activity (peripheral nerve stimulation monitoring)urine outputblood sugar levels buildup of exhaled inhalational anesthetics,MONITORS,Blood pressure monitoringNIBP using automated device; size of cuff should cover 2/3 of arm. Too wide cuff can produce false low BP while too small 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 spectrophotometry. 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 placement 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 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 eliminate. Nitrous oxide and desflurane are the shortest-acting anesthetic gases because they are the least soluble in blood.,Muscle Relaxants,Succinylcholine (Anectine) - depolarizingVecuronium (Norcuron) non depolarizing intermediate actingRocuronium (Esmeron) non depolarizing intermediate actingPancuronium (Pavulon) 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 burn patients, or paralysed (quadraplegic, paraplegic) patients. Succinylcholine may also trigger malignant hyperthermia in susceptible patients.Neuromuscular blockade can not be reversed,Opioids,Morphine Diamorphine, (diacetyl morphine, also known a