Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
75 Cards in this Set
- Front
- Back
Central blocks……why
|
Decr. incidence of DVT, PE, bleeding, pneumonia/resp. depression
Decr. incidence of cardiac complications, vascular graft occlusions Decr. stress response Sympathectomy= decr. SNS output Earlier return of gastric function Decr in PONV Decr incidence of post-op ileus Decr need for post-op narcotics |
|
Anatomy
|
33 vertebrae
31 paired spinal nerves Cervical and Lumbar regions convex ventrally Lumbar region is the highest point when lying flat (L3) Thoracic and Sacral regions convex dorsally Lowest point T5-T6 Vertebral column 26-27 inches long Spinal cord 17-18 inches long |
|
Anatomy
|
C1=atlas; lacks a body and attaches to skull
C2=Axis, is felt just below the occipital protuberance. C7 = cervicothoracic junction Most prominent midline structure at base of neck A line drawn between the lower borders of the scapula crosses the vertebral axis of approx. T7 A line drawn between both iliac crests usually represents L4-L5. |
|
Vertebral body
|
structural base of the vertebra
|
|
Paired pedicules
|
Attached directly to the vertebral body dorsally
|
|
Laminae:
|
Join the pedicules to form an oval space called the vertebral foramen
|
|
Vertebral foramen
|
Creates the spinal canal which houses the spinal cord, its covering and vascular supply
|
|
Intervertebral foramen
|
Created by the notching of 2 adjacent pedicles. Corresponding spinal nerve travel through each foramen
|
|
Midline spinous process
|
(arises b/t laminae) marks the midline of the spine’s surface (posteriorly)
|
|
Transverse spinous process
|
@ junction of lamina and pedicle
Processes serves as area of attachment for muscles/ligaments |
|
Supraspinous ligament
|
Most posterior(closest to skin) ligament. Connects vertebral spines
|
|
Epidural space
|
Potential space between the ligamentum flavum and the dura mater.
Starts at the foramen magnum ends at the sacrococcygeal membrane of the sacral hiatus. Contains nerve roots that exit from intervertebral foramina to peripheral locations Also contains fat, lymphatics and large network of veins (Batson’s plexus) much easier to get toxicity because of all the vasculature (especially really lipid soluble drugs) |
|
Dura mater
|
tough outermost layer; extension of cranial dura ends @ S2 where it fuses with filum terminale
“Sub” dural space (not clinically useful…however |
|
Arachnoid mater
|
delicate non-vascular layer closely attaching to dura mater
“Sub” arachnoid space is b/t here and pia |
|
Pia mater
|
immediately overlaying the spinal cord
Highly vascular layer Ends at filum terminale which anchors cord to the sacrum |
|
Spinal canal is the widest here and the vertebrae body is the smallest. The spinal processes are horizontal.
|
Cervical vertebrae
|
|
Sacral Hiatus
|
Defect in the roof of the dorsal aspect of the caudal end.
|
|
Coccyx
|
Represents fusion of three or four rudimentary vertebrae and has no anesthetic significance.
|
|
Spinal cord Extends from
|
foramen magnum to L3 in the newborn and moves up with age to ~L1.
|
|
The terminal end of the spinal cord
|
conus medullaris.
|
|
Dura mater
|
Outermost layer; dural sac extends to S2
|
|
Arachnoid
|
middle layer; also ends at S2
|
|
Pia mater
|
clings to spinal cord; ends at filum terminale
|
|
nerve roots.
31 pairs |
Each nerve root is composed of multiple rootlets
Area that a group of rootlets comes out to form a single spinal nerve is called a cord segment The area of skin (periphery) the spinal nerve and cord segment innervate is called a dermatome |
|
Cauda equina
|
Distal end of the spinal cord (below L1) where it branches off into terminal strands. These strands are bathed in CSF and enclosed within the dural sac.
|
|
BLOOD SUPPLY TO SPINAL CORD
|
2 posterior spinal Arteries
Responsible for ~ 25% of blood supply to the cord Primarily supply posterior portion of cord Receive chief blood supply from cerebral arterial system and many collaterals. Segmental arterial injury is unlikely because of collaterals. Filum is what anchors the cord. 1 anterior spinal artery: Responsible for ~75% of total blood supply to cord Primary supplier of anterolateral cord Supplied by many radicular arteries; poor collaterals Artery of Adamkiewicz or arteria radicularis magna. Single segmental branch of the aorta that supplies nearly all of the flow to the lower thoracic and lumbar segments. Injury renders this entire section at risk for ischemia. Artery of Adamkiewicz is typically unilateral and most often occurs near T8-T12 on the left side. |
|
Signs of absorption
|
one of first signs are confusion from the hyponatremia
|
|
Bladder perforation
|
one of the signs for that is excruciating shoulder pain
|
|
Contraindications
Controversial Absolute |
Pt refusal
Infection at site of puncture Hypovolemic shock Severe hemorrhage Severe idiopathic coagulopathy ^ ICP Indeterminate neurologic disease Aortic stenosis |
|
RELATIVE C/I FOR EPIDURAL SPINAL
|
Pre-existing neuropathies
Medical anticoagulation Heart valve dx (other than AS) Dementia Demyelinating dx (MS) Previous major spinal surgery |
|
NYSORA guidelines
|
NSAIDS (including ASA) are not contraindications
LMWH: hold 12hr. Before & 2 hr after catheter removal if epidural vein punctured: hold heparin for 2 hr. and LMWH for 24 hr GIIa/IIIb inhibitors held for 4 weeks post epidural Stop clopidogrel 7 days pre and ticlopidine 14 days pre |
|
Needles
|
Needles are either sharp or blunt at the tip, with either end injection or side injection.
|
|
Quincke-Babcock
|
It has a med bevel length with sharp edges, a sharp point and end injection. Usually typical 22g. This is a cutting needle. (turn bevel to the side) it will spread instead of cut.
|
|
Whitacre, Sprotte needle
|
“pencil point” rounded bevel, no cutting edges and side injection. Typical 24g needle in kits.
|
|
Tuohy needle
|
epidural needle 16-18g, 3 inches long, bevel tip and gentle curve to prevent dura puncture.
|
|
Paramedian approach
|
Useful in elderly or others with calcified interspinous ligament or difficulty flexing spine
Identify correct level as before Palpate spinous process Insert needle 1 cm lateral to this point and direct toward middle of interspace Ligamentum flavum is usually 1st ligament encountered using this technique |
|
Specific Gravity
|
Frame of reference for specific gravity is CSF 1.003-1.008.
Hyperbaric agent= Heavier than CSF SG > 1.008 Hypobaric agent=Lighter CSF SG < 1.003 Isobaric agent= Close to CSF stays where injected |
|
Hyperbaric Technique
|
Outcome is dependent on position of patient during and immediately after injection. Saddle block vs supine vs lateral. 3-5 minutes.
Cephalad spread can increase with raising the patients legs or trendelenburg position. Neck flexion can somewhat protect progression into cervical levels. |
|
Isobaric Technique
|
Tetracaine, lidocaine, bupivacaine can all be mixed with CSF.
Can also use lower conc. Of local which will make isobaric Solution remains near injection site decreasing high blocks and sympathetic block. |
|
Intra-abdominal pressure
|
Indirect affect on final level of local injected.
Causes changes in the contour of the subarachnoid space and total volume of CSF. Ex. Ascites, obesity, tumors, pregnancy. Changes from direct pressure in addition to decrease venous return and “backflow” into epidural veins. Large epidural veins occupy space. All of this can cause a more proximal spread. |
|
Pregnancy
|
Uterus causes increased intra-abdominal pressure and increased volume in the epidural venous plexus.
This results in smaller and tighter epidural and subarachnoid spaces. Higher spread |
|
Obesity
|
Overlying adipose tissue. Difficult to identify landmarks.
May need longer needle. 4” or 6” Paramedian approach is difficult. Increased intra-abdominal pressure. |
|
Age
|
Spinal and epidural spaces are thought to become smaller and less compliant.
Stenosis, scarring and calcification of tissues Require decreased dosages. |
|
Physiologic changes associated with spinal anesthesia:
Cardiovascular |
Sympathetic denervation results in cardiovascular changes based on the degree of sympathetomy.
Block height determines extent of sympathetic blockade Sympathetic chain originates from the thoracic and lumbar spinal cord. Arterial and venodilation BOTH occur to produce hypotension |
|
Total sympathectom
|
: increase in volume of the capacitance vessels, and a decrease in venous return to the heart. Decrease in preload equals hypotension.
|
|
Partial sympathectomy
|
T8 block usually allows physiologic compensation with vasoconstriction, mediated by sympathetic fibers above the block.
|
|
Cardiac accelerator fibers
|
sympathetic efferents (T1-T4). Increase heartrate when stimulated. High central blockade, unopposed vagal activity leads to bradycardia.
|
|
PULMONARY COMPLICATIONS TO CENTRAL BLOCK
|
Primary influence secondary to motor blockage of intercostal muscles and abdominal muscles.
TV is unchanged Phrenic (diaphragm) block is rare. C3-C5. Concentration is usually not enough to fully block A alpha nerves. (BIG). Apnea is usually related to hypoperfusion of brainstem resp centers from hypotension |
|
URINARY COMPLICATIONS FROM CENTRAL BLOCKS
|
Renal blood flow is maintained due to autoregulation
Muscle tone in the bladder is eliminated and urinary retention is common. S2-4 blockage is often last to resolve. |
|
GI COMPLICATIONS FROM CENTRAL BLOCKS
|
N/V
Unopposed parasympathetic activity Hypotension |
|
METABOLIC AND ENDOCRINE COMPLICATIONS FROM CENTRAL BLOCKS
|
Sympathetic activation from pain and surgery leads to many hormonal and metabolic responses.
Regional anesthesia can block the sympathetic responses that cause hypertension, myocardial stress and hyperglycemia. |
|
Complications
|
Pain with injection
Backache Headache Urinary retention Meningitis Vascular injury Nerve injury (cauda equina syndrome; TNS) High spinal If there is vascular injury is what would cause paralysis, they were anticoagulated, bleeding causes a hematoma and causes ischemia and the spinal nerves die. Emergent situation, immediate surgery to evacuate that hematoma. Key here is identification. You will see decreased sensory and motor function won’t return normally. Loss of bowel or organ ability to urinate. |
|
Backache
|
Needle insertion can cause hyperemia, local tissue irritation, reflex spasm of muscles.
Soreness can last for 10-14 days Patients with herniated disks or chronic back pain may have concerns. |
|
Headache
|
Spinal headache related to dural puncture and leakage of CSF leading to a decrease in CSF pressure.
This causes a downward traction on the structures of the CNS. Headache is postural. Worse when upright. Typically starting within 6-12 hours after puncture. Higher incidence in females, skinnier, and younger people |
|
Postdural puncture headachePDPH
Treatment includes |
Fluids/hydration
Oral analgesics Abdominal binder Caffeine (oral or intravenous) Bedrest/supine Try to treat medically first. Caffeine increases the production of CSF. You can’t do a spinal on a patient with an infection. You need to treat them medically. So if they have a temp you can’t do a spinal. |
|
Urinary retention
|
Blockage of S2-4 is associated with loss of bladder tone and inhibition of the voiding reflex.
Common in males. Long cases may need foley or straight cath at the end of case to prevent neurogenic bladder. Bladder distension can cause hypertension and tachycardia. |
|
Meningitis
|
Chemical (aseptic) Used to be a problem when needles were reused and cleansed with caustic substances.
Can be a problem if betadine is not removed from back before dural puncture |
|
Vascular injury
|
Epidural hematoma: Bleeding from epidural venous plexus.
Any spinal anesthetic that does not resolve within a reasonable amt of time or suddenly progresses after initial affects have worn off should be investigated. Early diagnosis is key. CT or MRI Emergency decompressive laminectomy. |
|
High spinal anesthesia
|
Severe hypotension
Profound bradycardia (Cardioaccelerators T1-T4) Respiratory insufficiency Hypoperfusion to medulla |
|
TREATMENT OF HIGH SPINAL
|
Support airway and circulation
Assist ventilation with 100% O2. Intubation to protect airway Fluids, pressors Head up does not decrease spinal at this point and can increase hypotension. Ephedrine is a good choice May need epinephrine |
|
Epidural anesthesia
|
Local diffuses through the intervertebral foramen to nerve roots and through meninges to CSF
Require diffusion from site of injection need more volume Unlike spinal anesthesia, which is all or none block, epidurals can provide analgesia with minimal block or full motor block |
|
ANATOMY OF THE EPIDURAL SPACE
|
Epidural space is bounded by the dura ventrally and the ligamentum flavum dorsally.
It extends from the foramen magnum to the sacral hiatus. Widest point at L2 The space is filled with loose connective tissue that surrounds the epidural veins. Epidural venous plexus Obstruction to venous return involving the vena cava will cause engorgement of the azygos system and enlargement of epidural venous system (OB pt during contraction) Stay midline No arteries in the epidural space, but main collateral flow to the anterior spinal artery crosses close to lateral area. Diffusion of meds from point of injection produces epidural anesthesia. Large spinal nerves L5 and S1 are the most difficult nerves to block in the epidural space. Epidural anesthesia requires a tenfold increase in dose of local anesthesic to fill the potential epidural space. Onset is slower secondary to diffusion across membranes. Segmental anesthesia: A band of anesthesia is produced, extending upward and downward from the injection point. |
|
Segmental spread depends largely on the volume of the local.
|
5ml may produce a narrow band of 3-5 dermatomes where 20ml volume will produce anesthesia from upper thoracic area to sacrum.
|
|
MARKS ON THE TOUHY
|
9 marks. Each one alternating is 1 cm. So 9 cm. You see 5 spaces, then you will say that you have loss of resistance at 4. (9-5 = 4). The longer fatter mark is 12, you need 12 before the catheter even leaves the needle. So add the 4 to 5 and that is where you want to leave the catheter against the skin.
|
|
Test dose
|
3 ml 1.5% Lido with epinephrine 1:200,000 (5 mcg per cc of epinephrine)
Intravascular injection will cause heart rate to increase by 20% within 30-60 seconds, circumoral numbness, ringing in ears Subarachnoid injection produces signs of spinal anesthesia within 3 minutes |
|
EPIDURAL ANESTHESIA EFFECTS THE
|
nerve roots and dorsal ganglia outside the dura. Also diffuse across the dura to the spinal cord
|
|
The dose of the local anesthetic is a function of the
|
volume injected and the conc of the solution
Ex. A higher volume of a lower concentration will result in a higher sensory level with less motor block. A lower volume of a higher concentration will result in a lower but denser sensory and motor block. |
|
EPIDURAL COMPLICATIONS
|
Similar to spinal complications
Wet tap: Epidural needle punctures the dura. 17g needle makes a big hole. HA in 40%-80% of patients Infection: Sterile tech. Signs of meningitis( Nuchal rigidity, fever, chilling) Epidural abscess or hematoma- requires immediate surgical intervention. |
|
Neuraxial opioids
|
Opioid receptors present in spinal cord
Modulate A-delta & C-fibers Improves perioperative analgesia Works synergistically with local; enhances analgesia without increasing motor or sympathetic blockade Reduces supraspinal effects of systemic opioids Causes dose dependent pruritis, nausea & urinary retention |
|
Morphine
(EPIDURAL) |
H2O soluble
Delayed onset; won’t see immediate effect Look for delayed respiratory depression 6-12hrs post injmorphine is more of a rostral spread. ection |
|
Fentanyl
(EPIDURAL) |
See more immediate effect; decr intraoperative need for opioids/volatile agent
Early respiratory depression 2-4 hours Absorption into nerve rootlets; vascular system, cord . The fentanyl doesn’t spread as much because it is lipid soluble |
|
Spinal opioids:
Morphine |
Prolonged spinal analgesia 6-18 hrs
Not useful for intraoperative relief due to hydrophilic nature Late onset of respiratory depression |
|
Spinal opioids
Fentanyl |
Useful for analgesia after injection
More rapid uptake With appropriate dose (10-25 mcq’s) little incidence of resp depression (if seen is early not delayed |
|
Caudal anesthesia
|
Most common regional in pediatrics
Most commonly used for surg of the lower extremities, perineum and lower abdomen. |
|
CAUDAL ANESTHESIA PROCEDURE
|
Patient is placed lateral or prone. Watch airway.
Identify landmarks. Sacral cornua should be easily palpable just above gluteal crease Feel for sacral hiatus. (located about 5 cm from the tip of the coccyx between the sacral cornua.) Feels like soft area between sacral cornua Sterile prep and remove betadine. Skin wheel if awake 22g jelco needle Introduce needle ~ 70 degrees angle to skin through the sacrococcygeal ligament. You do have to put a little pressure on this it’s tough. Firm but non vigorous pressure needed Once through ligament drop needle to 45 degree angle and advance slightly < 4 cm Remove needle , aspirate and inject. Often confirm with injection of small amount of air 1cc/kg (0.175-0.25% bupivacaine) |