Spinal Anesthesia – Flashcards
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What is spinal anesthesia?
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Injection of local anesthetic into the subarachnoid space that produces a rapid response in the patient
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What is another name for spinal anesthesia?
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Subarachnoid block
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What type of procedures is spinal anesthesia used during?
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Can be used for surgical procedures from the chest down such as lower abdomen, perineum, and lower extremity surgeries.
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What is the preferred anesthetics for cesarean delivery?
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Spinal anesthesia because it reduces morbidity and mortality because general anesthesia can cause uterine placental insufficiency and reduce blood flow to the baby
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What are the absolute contraindications for spinal anesthesia?
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1. Patient refusal 2. Increased intracranial pressure 3. Active coagulopathy 4. Inability to position 5. Infection at the site of injection
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What is the number one, most important contraindication for spinal anesthesia?
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Patient refusal
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What are some relative contraindications for spinal anesthesia?
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1. Systemic infection 2. Hemodynamic profile that odes not tolerate a decrease in systemic vascular resistance such as shock or aortic stenosis
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What happens to a patient with severe aortic stenosis receiving spinal anesthesia?
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Decrease SVR leads to decrease CO leads to worsening hypotension than MI
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How many total spinal nerves does an adult patient have?
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30 spinal nerves
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How many vertebra does an adult patient have?
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33
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Where is the inferior angle of the scapula located?
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T6-T7
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Where is the Superior iliac crest landmark on the vertebral column?
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Across the L4 body or the L4-L5 interspace
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What is the anatomical location of the epidural insertion?
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The superior aspect of the iliac crest
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How many cervical spinal nerves are there?
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8 spinal nerves for 7 vertbrae. All other vertebrae have one nerve per one vertebrae
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What is another name for the end of your spinal cord?
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Conus medullaris
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Where is the spinal cord normally end in the adult patient?
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L1
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What is cauda equina syndrome typically secondary to?
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Lidocaine this is why you don't use lidocaine often in spinal anesthesia
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What side of the spinal column is responsible for sensory?
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The dorsal portion carries the sensory fibers
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What side of the spinal column is responsible for motor?
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The ventral portion carriers the motor signal
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What are the neurotransmitters for the pain pathway?
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1. Substance P 2. Glutamate
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Where does fast pain cross over in the body? Slow pain?
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Fast pain= A delta crosses over in the medulla Slow pain= C fibers crosses over at the level of spinal cord in the gray matter
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What portions of the brain help to suppress pain?
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1. Raphe nucleus 2. Periadequatal grey
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Where are the sacral cornu?
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The sacral cornu are bony prominences on either side of the sacral hiatus that help aid the placement of caudal anesthesia. This is common in pediatric anesthesia and sometimes in adult hemmordiectomy
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What is the high point of the spinal vertebra when the patient is supine?
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C3 and L3
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What are the low points of the spinal vertebra when the patient is supine?
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T6 ; S2
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Describe the orienation of the spinous process of the vertebra?
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Lumbar ; cervical spinous process: relatively straight posterior and horizontal orientation Thoracic- pointing caudally or oblique orientation
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How many total vertebrae does an adult patient have?
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33
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How many total spinal nerves does a patient have?
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30
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How many thoracic vertebrae are there?
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12 (T1-T12)
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How many cerivcal vertebrae are there?
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7 (C1-C7)
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How many lumber vertebrae are there?
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5 vertebrae
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How many sacral vertebrae are there?
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5 fused together (in adults)
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How many coccyx vertebrae are there?
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4 fused together (in adults)
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What is the name for the first cervical vertebrae?
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Atlas (trick to remember this: the atlas carries the weight of the world (head) on its shoulders
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What is the name for the second cervical vertebrae?
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Axis
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Why is important to understand that the blood vessels are located in the lateral aspect of the epidural space?
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You need to know where is the blood vessels are located in order to avoid placing your spinal needle into the blood vessel
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What are the two different approaches for spinal anesthesia?
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1. median 2. paramedian
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How does the ligamentum flavum feel?
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It feels grainy sort of like sand
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How many ligaments are in the vertebral column?
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5
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Where do patients spinal cords typically end?
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30% T12 60% L1 10% L3
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Why do you use the superior iliac crest as the landmark for spinal anesthesia?
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Because it lines up with the area between L4 ; L5 where the spinal cord is not located.
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What is tuffiers line?
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A line drawn across the superior iliac crest that cross the body of L4 or the interspace of L4-L5. Ideal site of spinal anesthesia
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What are the spinal nerves in the subarachnoid space covered by?
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A thin layer of pia mater
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Where do local anesthetics work for spinal anesthesia?
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On the spinal nerves
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What are the common local anesthetics used for spinal anesthesia?
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1. Bupivacaine 2. Lidocaine 3. Tetracaine 4. Procaine
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What are some historical complications associated with lidocaine use for epidural anesthesia?
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1. Cauda equina syndrome 2. Transient radicular irritation ***this will manifest in leg, back, or buttock pain. Can reduce risk by using low dose, current recommendation of max dose of lidocaine is 60mg
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What type of cases require tourinquet?
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Knee surgeries
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What are the different doses for tetracaine?
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Lower extremity procedure = 6-10 mg Intra-abdominal procedure = 12-15 mg Pelvic procedure = 12 mg
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What are the different bupivacaine doses: c-section, ortho, and intra abdominal?
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C-section= 10-12.5 mg Orthopedic cases= 12-15 mg Intra-abdominal procedures =15-18 mg
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What is the benefit of adding a vasoconstrictor to spinal anesthesia?
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It prolongs the blockade by reducing blood flow preventing the local anesthetic moving away from site of action
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What is the benefit of adding opioids to spinal anesthesia?
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Intensify the block
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What kind of effect does local anesthetics and opioids have in the intrathecal space?
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Synergistic effects that contributes to the effectiveness of the blockade via the mu receptor
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What is the problem with morphine administration during spinal anesthesia?
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It can result in delayed respiratory depression due to its hydrophillic nature. This causes a long duration of action due to low spinal cord distribution volumes and slow clearance to the plasma
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What is the dose of morphine to adminster when giving spinal anesthesia?
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0.1-0.5mg
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What happens when you increase the dose of morphine in spinal anesthesia?
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Increase dose= increase side effects 1. N/V 2. Pruritus 3. Respiratory depression
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What is the benefit of using fentanyl and sufentanyl in spinal anesthesia?
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1. Lipophillic agents 2. Rapid spread in the spinal cord 3. Due to rapid rostral spread- can possible lead to early resp depression unlike morphine's delay 4. Small dose intensifies block but does not prolong it 5. Reduce LA dose 6. Faster sensory and motor recovery
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What is sufentanyl in spinal anesthesia most frequently used during?
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Labor and C-sections
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What is the dose of spinal sufentaynl for labor?
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2.5-7.5mcg
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What is the dose of spinal sufentaynl for c section?
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In combination with low dose bupivaine 2.5-10mcg
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What are the most common side effects of intrathecal opioids?
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1. Respiratory depression 2. Pruritus 3. N/V
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What are the two types of vasoconstrictors used in conjugation with local anesthetics in spinal anesthesia?
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1. Epinephrine (0.2-0.3mg) or epi wash 2. Neosynphrine (2-5mg) or neo wash
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What is the benefit of adding alpha 2 adrenergic agonist to local anesthetics for spinal anesthesia?
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Intensifies and prolongs sensory and motor blockade
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What are the common side effects of adding alpha 2 adrenergic agonists to local anesthetics for spinal anesthesia?
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1. hypotension 2. Bradycardia 3. sedation
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What factors can effect the uptake of local anesthetics in the neural space?
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1. Concentration of LA in the CSF 2. Suface area of the neural tissue 3. Lipid content of the nerve 4. Blood flow of the nerve
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How does concentration of local anesthetics effect uptake in the neural space?
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The higher the concentration, the better the effect
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How does blood flow affect the uptake of LA in the neural space?
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The greater the blood flow the less effective/length of block
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How does the surface area of the neural tissue affect the uptake of LA in the neural space?
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Smaller the surface area= better effect
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What are the primary nerve fibers for pain transmission?
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1. A delta 2. C fibers
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What fibers are affected by anesthetic blockade first?
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1. C fibers (slow pain & touch) 2. A delta (fast pain) 3. A alpha (motor)
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What functions are C fibers and A delta fibers responsible for?
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1. pain 2. Temperature 3. Touch
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Describe the location of nerve fibers within a nerve bundle.
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1. B fibers 2. C fibers 3. A-delta 4. A-gamma 5. A-beta 6. A-alpha
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What travels with pain on C fibers and A delta fibers?
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Temperature
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What are B fibers responsible for?
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Sympathetic
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What are A-gamma fibers responsible for?
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Motor tone
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What are A-beta fibers responsible for?
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Touch and pressure
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What are A-alpha fibers responsible for?
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Motor function & proprioception
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Describe the zones of differential blockade?
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Site of injection will be T6. There will be a motor blockade two levels lower ( T8) & there will be sympathetic blockade 2-6 levels higher than the sensory level. Sensory blockade will be at level of injection.
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What is the first fiber that recovers first after spinal anesthesia?
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A-alpha (motor functions)... nerve fibers return in reverse order (motor is the last to leave and first to return, etc.
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How are neural local anesthetics injections eliminated?
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They are eliminate via vascular absorption not via the kidney/liver from the body
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What changes with age effect spinal anesthesia?
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1. Neural nerves become vulnerable to local anesthetics 2. Number of myelinated nerves decrease 3. Conduction velocity in motor nerves decrease 4. CSF volumes decreases 5. Specific gravity of CSF increases
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Describe what you would expect to see in an elderly patient receiving spinal anesthesia.
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1. Faster onset 2. Higher level of blockade 3. Longer lasting anesthesia
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Can height affect spinal anesthesia?
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In extreme cases, length of the spinal column may affect the spread of local anesthetic
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Does weight of the patient affect the spread of local anesthetics during spinal anesthesia?
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High BMI as a result of a large abdominal mass will decrease the volume of CSF thusly spread of local anesthetic will increase
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What conditions will decrease the amount of CSF a patient would have?
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1. Morbid Obesity 2. ascites 3. Anything that compresses on the spinal column
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What is the normal CSF volume in an adult patient?
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150mL
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What does the graph attach reveal?
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The higher the volume of CSF the lower the spread of local anesthetics
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What are the safest injection site of spinal anesthesia?
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L4-L5
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Describe the spread of local anesthetics between L4-L5 & L2-L3?
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Spread of local anesthetic at L2-L3 is higher than L4-L5
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Is spinal injections sites higher than L3 recommeneded?
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No
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What does most studies suggestion about injecting spinal anesthesia above L3?
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Injections L3 and higher are at increased risk for causing neural damage
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What happens if the opening of the whitacre needle is placed toward the cranium?
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It causes a higher sensory level blockade and a longer duration of action
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What should you use in conjunction with a needle that is smaller than 22 G?
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Always use a transducer because they are so small you don't want to risk getting a needle stuck in their back if it breaks off
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What is barbotage?
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Aspiration CSF before injecting LA, mix the LA and CSF in the syringe, ; than injecting back into the spinal column.
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Is barbotage effective?
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It is found to be not effective
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How does the dose of Local anesthetic affect the spread of the local anesthetic?
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Larger doses of local anesthetic increase the spread of the medication
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What is density?
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Density is a physical characteristic expressed as weight in gram of 1 mL of a solution at a specified room temperature
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What is baricity?
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The relationship between the density of a local anesthetic and the density of the CSF
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What is an isobaric local anesthetic?
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Local anesthetic has the same density or specific gravity of CSF " stays where you put it"
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What is an hypobaric local anesthetic?
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Local anesthetic that has a density or specific gravity that is less than CSF "Floats up" because its lighter than CSF
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What is a hyperbaric local anesthetic?
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Local anesthetic that has a density or specific gravity that is greater than CSF "sinks" because its heavier than CSF
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What is isobaric local anesthetics mixed with?
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Normal saline
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What are hypobaric local anesthetics mixed with?
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Sterile water
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What are hyberbaric local anesthetics mixed with?
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dextrose
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What spinal level does sympathectomy occur at?
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T1-T4
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What are cardiovascular signs of spinal anesthesia?
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1. hypotension 2. Sympathectomy (arterial and venous dilation) 3. Possible bradycardia
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What do you want to do before performing spinal anesthesia?
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Administered crystalloids to your patient to help pretreat some of the potential cardiovascular side effects such as hypotension
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Why do you not want glucose in IV fluids such as dextrose during spinal anesthesia?
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The increase in glucose will cause the patient to urinate a lot, resulting in decrease in fluid volume status
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What is the drug of choice is a patient has severe bradycardia intraoperatively?
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Edephrine
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What is the drug of choice when a patient has symptomatic bradycardia during a procedure?
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Mixed alpha and beta agonist
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During spinal anesthesia, a patient experiences hypotension but has a normal or elevated heart rate, what drug would you want to administer?
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Phenylephrine (neo) which is an alpha agonist. This causes an increase in SVR without increasing HR
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During spinal anesthesia, a patient experiences hypotension with bradycardia, what drug would you administer?
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Ephedrine because it's a mixed alpha and beta agonist that will increase PVR and HR
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A patient becomes hypotension during subarachnoid anesthesia and received ephedrine. 10 mins past and the patient is now several hypertensive, what would you do?
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Manage the hypertension with vasodilators, narcotics, and anxiolytics
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How can you tell if epedrine and phenylephrine are working?
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First look for heart rate increase, blood pressure increase should follow
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Describe the respiratory complications often associated with subarachnoid anesthesia?
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Pulmonary alterations in healthy patients have little clinical significance. If the anesthesia is a high spinal some muscle paralyze can occur (abdominal than intercostal). If the phrenic nerves are paralyzed and loss of accessory muscle of ventilation occurs there will be an increases potential for hypoxia
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Where are the phrenic nerves?
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C3-C5
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What can happen to functional residual capacity during high spinal anesthesia?
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Functional residual capacity can decrease due to paralysis of abdominal muscles
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Describe the thermoregulatory considerations for patients receiving spinal anesthesia?
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1. Shivering due to peripheral vasodilation 2. Spinals impair central thermoregulation
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What do you need to do before performing spinal anesthesia?
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1. Prepare and monitor patient 2. Review history (anticoagulants and antiplatelet medications) 3. Ensure informed consent was completed 4. Prepare drugs and equipment 5. Always have general anesthesia set up
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Dermatome level for peri-anal surgery.
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S2-S5 aka saddle block
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Dermatome level for foot and ankle surgery.
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L2
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Dermatome level for knee surgery
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L1 ***used for lower limb amputation
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Dermatome level of thigh tourniquet procedure.
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T10
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Dermatome level for vaginal delivery and uterine procedures such as TURP.
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T10
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Dermatome level for urological & lower abdominal procedures.
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T6
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Dermatome level for upper abdominal surgery.
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T4
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What are different positions you can place patient in for spinal anesthesia?
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1. sitting 2. Lateral 3. jack-knife
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Describe how to place a patient in the sitting position for spinal anesthesia.
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1. Hang leges over the side of the bed 2. Have patient hug a pillow 3. Put patient feet up on a stool 4. Assistant must keep patient from swaying by standing in front of them 5. Have patient curve there back in a C formation
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What is the benefit of the C position during spinal anesthesia?
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It helps to palpate the spinous processes
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How do you place a patient in the lateral position for spinal anesthesia?
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1. Patient is placed parallel to the edge of the bed 2. Have the patients arms to the side and legs flexed up to the abdomen 3. Have patient flex forehead down toward the knees
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What are the layers that the needle will go through when performing spinal anesthesia via median?
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1. Skin 2. Subcutaneous fat 3. Supraspinous ligament 4. Interspinous ligament 5. Ligamentum flavum 6. Dura Mater 7. Subdural space 8. Arachnoid Mater 9. Subarachnoid space
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What layers does the needle travel through during spinal anesthesia utilizing a paramedian approach?
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Same layers as it does through the median approach except the supraspinous ligmant and interspinous ligament
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What layers did you transverse if you hear a pop during a spinal anesthesia?
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1. Ligamentum flavum 2. dura
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What does hyperbaric solution look like when mixed with CSF?
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You will notice a swirling in the solution... isobaric and hypobaric will remain clear in apperance
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What is the difference between paramedian and median approaches to spinal anesthesia?
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1. Paramedian you approach it in a lateral direction 2. Paramedian does not cross the interspinous and superspinous ligament
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What layers does the needle travel through during spinal anesthesia utilizing a paramedian approach?
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Same layers as it does through the median approach except the supraspinous ligmant and interspinous ligament
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What do you do if the spinal needle is already deeply inserted and it feels like it is in the right spot but there is no CSF what will you do?
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1. Rotate the needle 90 degrees and wait for 10 to 15 seconds, repeat as needed 2. Inset the stylet and remove it 3. Try to aspirate at different rotating angles 4. If troubleshooting does work, withdraw needle, check patient position, and try again
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If blood in the spinal needle/syringe a normal finding?
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Maybe. There may be some blood from the epidural space present in the needle. This should clear within a few drops of CSF. If blood continues to drip after this the position of the needle must be changes because it is most likely in an epidural vein
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What do you do if the spinal needles causes pain in the patients leg?
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DO NOT inject anything. Withdraw the needle and redirect it more medially
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What do you do if the needle hits the bone?
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1. Reposition the patient 2. Change the needle because the tip may be damaged from contact with the bone 3. Try a different interspace or paramedian technique 4. Pt with spinal stenosis are at increase risk of spinal hematoma; if you are not able to find the subarachnoid space, change the anesthesia method; do not be stubborn
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What are you probably hitting if the needle hits the bone early in the procedure during spinal anesthesia?
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Spinous process; correct this by pointing the needle slight caudad
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What bone are you probably making contact with if the needle hits bone late in the spinal anesthesia procedure?
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The lamina
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What would you do if you are hitting the lamina late in the procedure during spinal anesthesia?
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Point the needle slightly cephalad
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What are the reason for backaches during spinal anesthesia?
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1. Needle trauma 2. Local anesthetic irritation 3. Ligametous strain secondary to muscle relaxation
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What causes a postdural puncture headache?
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This is due to an accidental dural puncture. After the dura was punctured, the hole did not close up and CSF slowly was leaking out. When CSF continues to leak out, there is not enough CSF around the brain causing compression & cranial nerve traction, resulting in headache
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Describe the headache associated with postdural puncture?
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1. Headache is worse when patient is upright 2. Pain radiates to neck "stiff neck" 3. Nausea and vomiting
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What is a wet tap?
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The accidental dural puncture
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What are some other signs and symptoms due to accidental dural puncture resulting in low CSF?
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1.Headache 2. Diplopia (CN 6) 3. Tinnitus (CNS 8) 4. Seizure
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Why does diplopia occur with accidental dural punctures?
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Traction on cranial nerve 6 caused by low CSF result in failure of the affect eye to abduct resulting in diplopia
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Why are seizures a possibility after accidental dural puncture?
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Due to cerebral vasospasm caused by cerebral hypotension from dural puncture
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What are the two most common sign and symptoms associated with postdural headache?
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1. Nausea (60%) 2. Neck stiffness
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What is the etiology of postdural headache?
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Loss of CSF volume exceeding CSF production ? cerebral vasodilation ? pain
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What are some risk factors for postdural headache?
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1. Younger patients 2. Women 3. History of prior post dural headache 4. Multiple dural punctures 5. Needle design and size (whitarch good)
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What is the treatment options of postdural headaches?
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1. Patient to remain supine 2. NSAIDS 3. Narcotics 4. Methylaxanthine derivatives (Caffeine) 5. Blood patch
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What is a blood patch useful for treating?
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Postdural puncture headaches and symptoms associated with this
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How is a blood patch performed?
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20ml of blood is removed from the patients arm. With the patient in the lateral position the epidural space is located with a Tuohy needle at the level of the dural puncture or a intervertbral space lower. A few mls of the patient blood is injected. The blood will then clot and hopefully occulde the perforation, preventing further CSF leak
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Do you perform a test dose in spinal anesthesia?
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No only with epidural anesthesia
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Is the risk of systemic toxicity high or low with spinal anesthesia?
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It is very rare with spinal anesthesia because drug doses are low. This is a more common issue among epidural anesthesia.
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Why is a test dose performed with epidural anesthesia?
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To avoid systemic toxicity associated with epidural anesthesia
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What spinal nerve innervate the lung?
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T2-T5
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What is total spinal anesthesia?
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When sensory and motor function is lost high in the spinal cord resulting in profound hypotension, bradycardia, and possibly respiratory arrest
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What are some complications/side effects of spinal anesthesia?
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1. backache 2. Post dural puncture headache 3. Total spinal anesthesia 4. Cauda equina sydrome 5. Transient neurologic symptoms 6. Spinal hematoma
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What is transient neuologic symptoms associated with?
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Lidocaine use during spinal anesthesia that result in pain in the legs or buttocks after spinal anesthesia.
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What spinal anesthesia complications are associated with lidocaine use?
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1. Cauda equina syndrome 2. Transient neurological symptoms
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What is cauda equina syndrome?
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Caused by the pooling of toxic concentrations of undiluted lidocaine around the dependent cauda equina nerve roots. This can result in low back pain, weakness, and sensory deficits including bowel and bladder dysfunction.
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What are some other names for spinal anesthesia?
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1. Intrathecal anesthesia 2. Subarachnoid anesthesia
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Where is the end point of the spinal cord for most adults?
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L1
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What is the end point of the spinal cord for children?
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L3
