Anesthesia Lecture Notes PDF

Central Neuraxial Blockade(Conduction Anesthesia) ( Epidural and Spinal Anesthesia ) Anatomy : The vertebral Column consist of 7 cervical vertebrae, 12 thoracic, 5 lumber as well as 5 fused sacral and 4 fused coccygeal vertebrae. ( 7C , 12T , 5L , 5S & 4CC ) C.S.F is foun...

Central Neuraxial Blockade(Conduction Anesthesia) ( Epidural and Spinal Anesthesia ) Anatomy : The vertebral Column consist of 7 cervical vertebrae, 12 thoracic, 5 lumber as well as 5 fused sacral and 4 fused coccygeal vertebrae. ( 7C , 12T , 5L , 5S & 4CC ) C.S.F is found in spinal space between the pia and arachnoid layer. The epidural space is found between the connective tissue covering the vertebrae and the ligamentum flavum posteriorly and the dura mater anteriorly. Laterally it is bound by the pedicles and the intervertebral foramina. The epidural space extends from the foramen magnum, where the dura is fused from the base of skull to the sacral hiatus. Anatomic landmark for a spinal anesthesia includes the spinous processes and the iliac crests. A line drawn across the patient's back at the level of the top of the iliac crest usually crosses the vertebral column at the L4 level , the interspace palpated directly above this line is the L3-L4. What layers are passed through in spinal anesthesia? Skin, subcutaneous tissue between two spinous processes supraspinous ligament, interspinous ligament between two vertebrae, then through ligamentum flavum where increased resistance is felt. Finally, the dura mater is traversed, and subarachnoid space is accessed 6cm from skin to subarachnoid space& then CSF. 1 Lec. 2 Dr. Eman S. Salih Spinal anesthesia Spinal cord is with three meninges. The outer layer is Dura mater and the second layer is arachnoids layer, the space between the Dura mater and arachnoids is called subdural space. The third layer is Pia mater and the space between arachnoids layer and Pia mater is called subarachnoid space which is contain the C.S.F. The spinal column extended from the base of skull till the level of space between L1,L2, So the level of injection of local anesthetic is in subarachnoid space of intervertebral space between L3-L4 & lower down. Spinal anesthesia is perform for operations of lower abdomen, Inguinal regions, lower extremities, or perineum region , It is injection of local anesthetic into the subarachnoid space , The main effect results from anesthetization of anterior and posterior nerve roots, loss of neural function (autonomic activity, superficial pain, temperature sensation, vibratory position sense, motor power, touch. The advantages of spinal anesthesia: 1- It offers retention of consciousness. 2- It offers excellent muscle relaxation, Contracted bowel, And quiet breathing. 3- It is useful in presence of hepatic, renal, or metabolic diseases. 4- Relative decrease in bleeding owing to hypotension. 5- It is useful in husky, muscular patient. 6- It is useful in cesarean section. 7- It is useful in alcoholic and addictive patient. 8- It is preferable when the airways management may be more Difficult. Contraindication of spinal and epidural anesthesia absolute : …. 1. Patient refusal. 2. Sepsis with hemodynamic instability. 3. Uncorrected hypovolemia. 4. Coagulopathy Relative contraindications : … 1. Elevated intracranial pressure. 2. Prior back injury with neurologic deficit. 3. Progressive neurologic disease, such as multiple sclerosis. 4. Chronic back pain. 5. Localized infection near the site of injection. 6- Very young patient, morbid fear, and mental aberration 7- Decrease blood volume anemia, and CVD. 2 Lec. 2 Dr. Eman S. Salih Disadvantages of spinal anesthesia: (( Complications , Physiological Effect )) Hypotension due to paralysis of sympathetic nerves system And vasodilatation. Bradycardia Urenary retention. Possible interference with efficient respiratory exchange Possible difficult technique. Postoperative headache. Danger of technique: introduction of infection, injury of Nerve.. Postoperative nausea & vomiting. on circulation, it caused hypotension(treated by vasopressor drugs and I.V fluid), it resulted from interruption of preganglionic and postganglionic sympathetic nerve impulses and interruption of baroreceptor reflexes that control the blood pressure. Also, it is due to decrease peripheral vascular resistance and vasodilatation. Bradycardia is resulted from block of Accelerator impulses to heart or decrease endogenous release of norepinephrine from sympathetic nerve ending. on respiration, Paralysis of intercostal muscles¯ doesn't "cause respiratory insufficiency. If the root of phrenic nerve is not reached by the anesthetic diaphragmatic action alone should provide adequate ventilation. Patient complain from difficulty of breathing during spinal anesthesia due to lack of proprioception in abdominal and thoracic muscles. on bowel and urinary tract, Intestine being contracted and hyperactive and sphincter relaxed due to unopposed of parasympathetic activity. Morphine and atropine are minimizing this action. Equipment used for spinal anesthesia: 1- Spinal needle. 2- Syringe of 5CC for local analgesia(local infiltration of skin)at the site of lumber puncture. 3- Syringe 'for local anesthetic of spinal anesthesia. 4-Ampules of local anesthetic e.g. lidocaine. 5- Sterile towel. 6-Swabs and swab holder. 7- Rubber gloves. 8-Antiseptic solution like Hibitane. 3 Lec. 2 Dr. Eman S. Salih Duration of action affected by : 1- Type of local anesthetic, Procaine(60min), Xylocaine(90min), Tetracaine(150min), bupivacaine (150 min). 2- Quantity of local anesthetic. 3- Mixing of local anesthetic with Vasoconstrictor (Epinephrine0.2mg, or phenyl epinephrine 1-2mg). Factors influencing spread hyperbaric spinal solutions 1. Position of the patient. 2. Spinal curvature. 3. Speed of injection. 4. Barbotage. 5. Interspace chosen. 6. Volume of local anesthetic. 7. Dose of drug. 8. Specific gravity of drug. 9. Fixation. Technique of spinal anesthesia : - The patient should have a cannula. - The patient takes either lateral or sitting position and the chin touch the chest or knees in order to open the intervertebral space as much as possible. - All the equipment must be sterilized by autoclave. - After dressing the cap and the mask then antiseptic the anesthetic hands and he should wear rubber gloves , sterilize the back of patient, begin from the area of injection and outside using the swab holder. - A sterile towel draped around the bottom of back Pointing the area of injection ( space between L3- L4) BY… Feeling the Two Iliac Crests and The Line Connected Between Them Passing Through the Back. - Sometimes anesthetizing the skin at the area of injection of spinal needle (infiltration). Puncture the skin( by spinal needle) at the level of space between L3- L4, in Middle line and slightly upward direction. When you pierce the Dura, you will feel loss of resistance, then remove the satellite to see the flow of CSF which is mean the success. connect the spinal needle to syringe containing the local anesthetic e.g. Lidocaine and inject it. If blood flows with CSF, the spinal needle should be drawn and try again. - After three failure of performing spinal anesthesia, you should try another type of anesthesia. The care of patient under spinal anesthesia: Preoperatively : It is the same preparation that is required for G.A except the premedication may be heavier like opioid, sedative. 4 Lec. 2 Dr. Eman S. Salih During the operation : 1- The patient should be comfortable on the operative table. 2- Monitor the vital sign :pulse, blood pressure, adequacy of respiration and encouragement. 3- The surgeon must not describe his operation in audible voice. 4- If there is nausea or vomiting result from fall in blood pressure or surgical manipulation in upper abdominal region, it will be treated by oxygen supply, plasil and I.V fluid. 5- Test the level of anesthesia, at least during the first 5-10 minutes. 6- Respiratory insufficiency :due to phrenic nerve block, and usually the accessory muscles of respiration are used, treated by Oxygen supply by mask. 7- Hypotension may occur(systolic pressure below 80mmHg), treated by Oxygen supply by mask, I.V fluid infusion, administration of vasoconstrictive drug like Ephedrine 5-10mg I.V or phenylephrine. Postoperatively: 1- Avoidance of injury to limbs. 2- Monitoring of vital sign. 3- Prevention of postoperative headache which is due to leakage of CSF from hole in the Dura mater caused by needle. Loss of CSF result in decrease in CSF pressure. Treated by bed rest, analgesia, caffeine and hydration of 3L or more daily either orally or I.V, epidural blood patch. Epidural anesthesia : Placement of local anesthetic solution into the epidural space, most often at lumber level, Thoracic block is useful for postoperative analgesia and pain relief following trauma. Cervical block has been performed for pain therapy and for carotid artery, thyroid and arm surgery. Continuous epidural anesthesia made possible by placement of plastic catheter into the epidural space in the most common method for providing epidural anesthesia. Technique: The epidural anesthesia is instituted in a similar fashion to spinal anesthesia. Patient placed in a seated upright or lateral decubitus position, with the back flexed as much as possible. the back prepared and draped sterilely, local infiltration of the skin overlying the chosen interspace is administered. The epidural needle tip is curved to help prevent accidental puncture of the dura mater and to facilitate threading of the epidural catheter through the needle into the epidural space. The epidural space is locatable by the loss of resistance technique. First: the tough ligamentum flavum overlies the space posteriorly, providing resistance to the needle as it passes through it. 5 Lec. 2 Dr. Eman S. Salih Second: there is negative pressure in the epidural space implying negative resistance. The change in resistance, or loss of resistance locate the epidural space, and this can be sensing the loss of resistance by connecting a syringe on the hub of Tuohy needle and applying continuous gentle pressure on the plunger of the syringe as the needle is advanced through the ligaments through into the epidural space. Once the epidural space is located with Tuohy needle by the loss of resistance technique. The epidural catheter can be thread into the space. Typically, 2-5cm after the epidural catheter has been placed and the Tuohy needle has been pulled back, the epidural catheter is best secured in place by taping it to the patient's back. The test dose used for epidural catheter is 3ml of 1.5%Lidnocain with 1:200000 Epinephrine. The test dose is performed to exclude the possibility that the catheter has been accidentally placed into an epidural vein or into the subarachnoid space. Waite for 3minutes after the administration of the test dose to safely exclude these two possibilities. Difference between spinal and epidural anesthesia: 1- Both are called regional or conduction anesthesia. 2- In spinal anesthesia medicine is deposited in subarachnoid Space must commonly at lumber level. In epidural anesthesia Medicine is deposited in epidural space most commonly at Lumber level. 3- Both provide surgical anesthesia without affecting the state of consciousness of patient, skeletal relaxation, and lack of the need for manipulate the airway or mechanically ventilate the lungs. 4- Spinal anesthesia takes less time to perform and has a quicker onset, provides for intense sensory and motor anesthesia, and may be of less discomfort to the patient, when compared with epidural anesthesia. 5- Epidural anesthesia when compared with spinal-anesthesia has A decreased risk of post Dural puncture headache, allow for more controlled over the level of anesthesia and the duration of the anesthesia. It may lead to better control of the associated Hypotension due to its slower onset and provides for an Indwelling catheter that can be used for acute postoperative Pain management. Advantages of Epidural over spinal anesthesia 1. Epidural anesthesia can produce a segmental block focused on area of surgery or pain. 2. The gradual onset of sympathetic block allows time to manage associated hypotension. 3. Duration of anesthesia can be prolonged by using epidural catheter. 4. There is more flexibility in the density of the block. 5. Decreased incidence of headache. 6 Lec. 2 Dr. Eman S. Salih