Anaesthesia Presentation PDF

What is anaesthesia? Anesthesia = no feeling Analgesia =no pain Hypnosis =loss of Consciousness Amnesia =loss of memory Muscle Relaxant =skeletal muscle paralysis (that include the main muscle of respiration The diaphragm which is the last muscle to be paralyzed an first mu...

What is anaesthesia? Anesthesia = no feeling Analgesia =no pain Hypnosis =loss of Consciousness Amnesia =loss of memory Muscle Relaxant =skeletal muscle paralysis (that include the main muscle of respiration The diaphragm which is the last muscle to be paralyzed an first muscle to recover). Philosophy of anesthesia in general 1- Analgesia (ALONE) =Local analgesic techniques 2- Analgesia Hypnosis=G.A. 3- Analgesia+ Hypnosis +Amnesia=G.A G.A. could be with either 1- spontaneous respiration The Target Of Anaesthetic (In general) Analgesia = No pain -The hypothalms.ex.Narcotic Agent like (pethidine, Morphine) Hypnosis=loss of consciousness, CNS/Brain stem ascending and descending Reticular formation ex. Thiopentone(2.5%) Amnesia=loss of memory ,CNS/cereperal cortex,ex.minor Tranquilizer Family;diazepam Muscle relaxation= the motor end plate, ACH recepters ex. depolarizing muscle relaxant(scoline), Non-depolarizing muscle relaxant (pavilion) some drugs have more then site of action; Ex.Narcotic Analgesia--- analgesia ,but at a higher doses causes analgesia Anaesthesia A. It can involve a simple local anesthetic injection which numbs a small part of the body, such as a finger or around a tooth. The drugs used in local anesthesia work by blocking the signals that pass along your nerves to your brain. When the drugs wear off, you start to feel normal sensations again. B.It can also involve using powerful drugs which cause unconsciousness or ‘general anesthesia’. These drugs also affect the function of the heart, lungs and circulation. As a result, general anesthesia is only given under the close supervision of an anesthetist, who is trained to consider the best way to give an effective anesthetic while keeping safe and well Stages G.A. of anesthesia They divided the system into four stages: The risk of anesthesia Anesthesia is generally safe. But there can be risks, especially with general anesthesia, including: 1-Heart rhythm or breathing problems 2-allergic reaction to the anesthesia 3-Delirium after general anesthesia. Delirium makes people confused. They may be unclear about what is happening to them. Some people over the age of 60 have delirium for several days after surgery. It can also happen to children when they first wake up from anesthesia. 4-Awareness when someone is under general anesthesia. This usually means that the person hears sounds. But sometimes they can feel pain. This is rare. Types of anaesthesia 1- General anesthesia General anesthesia is a state of controlled unconsciousness during which you feel nothing. You will have no memory of what happens while you are anaesthetized. A general anesthesia is required for a very wide range of operations. This  Anesthetic drugs are injected into a vein, or anesthetic gases are given to you to breathe. These drugs stop the brain from responding to sensory messages travelling from nerves in the body. Anesthetic unconsciousness is different from a natural sleep. You can not be woken from an anesthesia until the drugs are stopped and their effects wear off. While you are unconscious, the team in theatre look after you with great care. Your anesthetist stays near to you all the time. 2 -Local anesthesia A local anesthetic numbs a small part of the body where you are having the operation is used when nerves can be easily reached by drops, sprays, ointments or injections. You stay conscious, but free from pain. Common examples of surgery using local anesthetic are having teeth removed and some common operations on the eye. 3 -Regional anaesthesia  4 -Spinal and epidural anaesthesia Spinals and epidurals are the most common types of regional anesthetics. These injections can be used for operations on the lower body, such as caesarean section, bladder operations or repl5 Other types of regional anaesthesia 5- Other types of regional anesthetics involve an injection placed near to a nerve or group of nerves, for example in the arm or leg. This is often called a ‘nerve block’ and can allow you to have the operation without a general anesthesia. Nerve blocks are also useful for pain relief after the operation, as the area will stay numb for a number of hours. Acing hip. You stay conscious, but free from pain. 6 - Sedation Sedation involves using small amounts of anesthetic drugs to produce a ‘sleep-like’ state. There are different levels of sedation. Commonly, sedation will make you feel drowsy and relaxed about what is happening. You may sleep for a period but the person giving your sedation will speak with you  You may remember everything, something or nothing after sedation. However, sedation does not guarantee that you will have no memory of the operation. Only a general anesthetic can do that. 6- combination Anesthetic techniques can often be used together. For example, a regional anesthetic may be given for pain relief after an operation for which you have had a general anesthetic. What are the types of local analgesic techniques available The general anesthetic allows you to remain unconscious and in common remember practice nothing. 1-Surface analgesia Act on nerve ending ex. At skin-analgesia (Ethyl chloride), ice 2-nerve block ; act by blocking small nerves ex. pudendal n. block during vaginal delivery for prim gravida ex 2% xylocaine injected locally for removal of small lipoma from skin 3-nerve trunk block ;big nerve blocked ex 2% xylocaine injected to block axillary nerves for some limp surgeries Like removal of foreign body seated 4-nerve plexus block ; ex. analgesia at plexus level at the formation of nerve trunks. Ex surgery for upper limp as whole/ex wound excision hummers for external fixation because of comminuted fracture. 5-Epidural block ; the nerve blocked outside the dura ex.painless labour. 6- subdural block(spinal); the analgesic drug is injected at the puncturing at dura ex. Appendectomy 7-beer,block ;i.v. xylocaine for upper and lower limber surgeries 8-Acupuncture...unknown mechanism What are the desirable components of anesthesia? 1- Immobility in response to noxious stimuli. 2-Anxiolysis. 3-Amnesia. 4-Analgesia. 5-Unconsiousness. 6-Muscle relaxation. 7-loss of autonomic reflexes. What are the effects of G.A.at low doses? 1-Amenesia. 2-Euphoria. 3-Analgesia. 4-Hypnosis. 5- Excitation. 6-hyperreflexia. What are the effects of G.A.at high doses? 1-deep sedation. 2-musle relaxation. 3-Diminish motor response. 4-diminish autonomic response. 5-myocardial protection from ischemia. 6-cardiovascular/respiratory depression. 7-Hypothermia 8- nausia and vomiting. 9-death. What are the phases of G.A.? Classification stages of anesthesia? 1-stage 1 / decrease awareness of pain and amnesia 2-stage2 /delirium, excitation, enhanced reflexes irregular respiratory 3-stage 3 /unconsciousness, no pain reflexes, regular respiration, maintained B.P. 4-stage4 /respiratory &cardiovascular depression requiring ventilation What are the chatarstics of G.A.? 1-Rapid onset (within seconds) 2-Rapid wake (wit in minutes) 4-destibution determined duration of action Pre-anesthetic medications 1-Benzodiazepines. (midazolam, diazepam) Reduce anxiety. 2-Barbiturate. (pentothal sodium) Sedation 3-Antihistamine (diphenhydramine) Prevent allergic reaction Characteristic of AN IDEAL ANESTHETIC 1-Rapid& pleasant induction. 2-rapid changes in depth of anesthesia. 3-Adequate muscle relaxant. 4-Wide margin of safety. 5-Abcence of toxic\adverse effect. 6-No emergency problem. (no single agent yet identified as ideal anesthetic agent.) ANESTHETIC UPTAKE&DISTRIBUTION 1-vessel rich group(VRG) CNS& visceral organs High blood flow about75%&low capacity 2-muscle group(MG) Skin muscle, moderate blood flow &high capacity. 3-Fat group(FG) Low blood flow and high capacity. 4-vessel poor group(VPG) Low blood flow and low capacity DEAD SPACE(VD) VENTILATION FLOW WHICH IS NOT FACED BY BLOOD FLOW FOR EXCHANGE (NO O2 EXCHANGE) VD ABOUT 150 ML(NORMALLY) Flo2 -=fraction of inspired O2 concentration =about 21% in air. Ventaletion\blood flow ratio is ratio between air flow with O2 to blood perfusion by right cardiac output. If ratio less then 1= shunt = decrease Pa (arterial oxygenation) O2 If ratio MORE then 1= D.S. = decrease Pa O2 (arterial oxygenation)