Neuraxial Anesthesia Flashcards
What is Neuraxial Anesthesia?
Spinal
Epidural
Caudal (mostly peds)
Why use Neuraxial Anesthesia?
- -Alternative to general anesthesia
- -Can be used in conjunction with GA
- -Post-operative analgesia (may use lower opioid use with and decreases incidence of atelectasis, hypoventilation, and aspiration pneumonia)
- -Management of acute or chronic pain
What are some advantages of using spinal anesthesia?
- Simple
- Predictable
- Fully conscious patient
- Analgesia into the post-op period
- Ideal for lower abdomen, pelvis/ perineum, and lower extremities
- Reduces risk of DVT*
- Use small dose of LA, less toxicity
What are some disadvantages of Spinal Anesthesia?
---Sympathetic blockade 100% of the time (B fiber causes this) Hypotension --Intense motor blockade May last for hours post-op --Surgeons complain “It takes to long”
What are the Absolute contraindications?***
—Patient refusal (if you do this, it is assault and battery)
—Severe psychiatric disease
May not cooperate
—Cardiovascular disease
Severe aortic/mitral stenosis and septal hypertrophy
—Severe hypovolemia
Can be corrected before the spinal
—CNS disease
MS or nerve injury
Herpetic infections
Increased ICP- brain herniation
—Blood clotting anomalies
Anticoagulant therapy
ASRA guidelines
—-Infection at the site
Septicemia or bacteremia
—Allergy to LA
Ester LA
Reaction to the preservatives
What are the Relative contraindications?**
---HIV Associated with neurological manifestations ---Surgery of unknown duration ----Untreated chronic HTN Unstable BP after spinal Greater drop in BP than normal pt ---Procedures above the abdomen ---Obesity ----Deformities of the spinal column (depends what kind of deformities) ----Chronic HA or backache ----Bloody tap ----Multiple attempts ----Minor abnormalities in blood clotting ASA therapy Small dose of heparin Check coags before spinal insertion and document Platelet count
What are the pros and cons for doing a neuroaxial block on the sick elderly patient??***
—PROs
Possibility of less post-operative delirium
—-CONs
Hypotension, bradycardia
Rebound HTN, tachycardia = Fluid & pressors
What are some things to watch out for in the obstetric patient and neuroaxial block??***
Decreased M&M
Less effects on mother and fetus
When doing a neuroaxial block, make sure the patient understands and accepts risk, what is the most important thing that must be documented??**
Document the informed consent*
How many Cervical vertebral are there?
7 cervical
How many Thoracic vertebral are there?
12 thoracic
How many Lumbar vertebral are there?
5 lumbar
How many Scaral vertebra are there?
5 sacral (fused) vertebra
What are the vertebral bodies connect by?
The vertebral bodies are connected by the intervertebral disks
The spinal column forms what shape??***
Spinal column forms a DOUBLE C**
Ligamentous elements provide structural support, long with muscles help maintain shape. Ventrally (Motor) how is the spinal column supported?
Ventrally –Motor
Vertebral bodies and intervertebral disks are connected + supported by anterior and posterior longitudinal ligaments
Ligamentous elements provide structural support, long with muscles help maintain shape. Dorsally (Sensory) how is the spinal column supported?
Ligamentum flavum = LF
Interspinous ligament = ISL
Supraspinous ligament = SSL
What space is in between the ligamentum flavum and dura mater?***
Epidural space (potential)
What space is in between the Dura mater and the Arachnoid mater?***
Spinal subdural space (potential)
What space is in between the Arachnoid mater and the Pia mater?***
CSF (subarachonoid space)
What covers the spinal column?
The meninges
Where does the spinal cord extend too?
Extends from foramen magnum to L1 in adults
L3 in children
Anterior & posterior nerve roots at each spinal level join one another and exit where?
Anterior & posterior nerve roots at each spinal level join one another and exit the intervertebral foramina forming spinal nerves from C1 to S5
The single anterior spinal artery supplies how much of the spinal cord?**
–Single anterior spinal artery
Formed from vertebral artery at the base of the skull
–Course down the anterior surface of the cord
–Supplies the anterior 2/3 of the cord *
The Paired posterior spinal arteries supply how much o the spinal cord??***
- -Arise from the posterior inferior cerebellar arteries
- -Course down along the dorsal surface of the SC medial to the dorsal nerve roots
- -Supplies the posterior 1/3 of the cord *
Artery of Adamkiewics supplies what???***
Artery of Adamkiewics (Radicularis Magna) Blood supply to Anterior, lower 2/3 of the spinal cord- Injury due to ischemia- Anterior Spinal Artery Syndrome ***
What is the principal site of action for neuraxial blockade?
Principal site of action for neuraxial blockade is the nerve root
LA bathes the nerve roots in subarachnoid space or epidural space
Blockade of anterior nerve root fibers prevents what?
Blockade of anterior nerve root fibers prevents efferent motor and autonomic outflow
Blockade of neural transmission (conduction) in the posterior nerve root fibers interrupts what two things?
Blockade of neural transmission (conduction) in the posterior nerve root fibers interrupts somatic and visceral sensation
Sensory blockade blocks what two things?
Sensory blockade – somatic + visceral
Smaller and myelinated fibers are generally more easily blocked than larger unmyelinated fibers. Why?
Smaller and myelinated fibers are generally more easily blocked than larger unmyelinated fibers
- –Because the concentration of LA decreases the further away from the injection site, called the phenomenon of differential blockade
- —Sympathetic blockade 2 segments higher than sensory blockade which is 2 segments higher than motor blockade
What is the Dermatome Sensory blockade rule of two mean?*****
Level of block is determine by the sensory
Sympathetic is two levels about the sensory and motor is two levels below the sensory
What is the oder of nerve fiber blockage??***
—B fibers-Autonomic, sympathetic efferent
—C and A Delta Temperature, Touch
–A Gamma- muscle tone
–A Beta- small motor, pressure
–A Alpha- Large Motor, Proprioception
This is the order for motor blockade
Due to the small size ,autonomic fibers are blocked quickly what can happen because of this?*****
In terms of Sympathectomy and BP?
- –Due to small size autonomic fibers are blocked quickly
- –Sympathectomy is accentuated in the hypovolemic pt
- –Drop in BP is the earliest sign that the spinal is working
- –A rapid drop in BP may cause nausea and dizziness
- –Treat quickly
Temperature and Light touch is innervated by which fibers??**
Innervated by the unmyelinated C and myelinated A-delta fibers**
Loss of these follows autonomic blockade
How do we assess the C and A-delta fibers?
Alcohol sponge
Loss of temperature correlates with sensory loss
Motor impairment and touch are innervated by which fibers??**
Myelinated A-beta & A-gamma**
—Loss of motor & touch follows loss of light touch and temperature discrimination
—-Differential block
Motor block is 2 dermatones below sensory block
–Use a sharpened device or pinch method to assess level
—DO NOT USE A NEEDLE**
Profound Motor Block is innervated by which fibers?**
Myelinated A-alpha***
- -Motor block and loss of propioception
- –Pt’s will feel legs are still in the air after being prepped
- —Make sure pt knows that this is normal and it will wear off
Where do you assess the level of profound motor block??**
Assess block (this is for the motor response?) S1-2- dorsiflex his feet L4-5- flex his toes L2-3- raise his knees* (if they cant raise their knees, you have a L2-3 block) T6-T12- lift shoulders off the bed (if they cant do this, you have a T6-12 block)
S2-5 is the desired level of block for what??**
S2-5***
Saddle block
No affect on the ANS
Surgical anesthesia limited to perineum, perianal, & genitalia
T10 is the desired level of block for what??*****
T10 (umbilicus)*** Low spinal Blocks S1-5 & L1-5 Produce vasodilation, lower BP Good for GYN, vaginal delivery, lower extremity surgery, TURP, & cysto
T4 is the desired level of block for what?**
T4 (nipple)*** High spinal Used for upper abdominal surgery Can feel traction Can cause vasodilation and block cardioaccelator fibers (c-section)
C8 is the desired level of block for what???***
C8 (little finger)*** Total spinal Difficulty breathing Can lead to respiratory & cardiac arrest (should not want this)** (you’ll have cardiac accelerators)
What are the CV manifestations of a neuraxial blockage?
CV:
↓ BP, ↓ HR, ↓ Contractility – all proportionate to the level of sympathectomy
—-Vasomotor tone arises from T5-L1 – innervates arterial and venous smooth muscle
Vasodilation
Decreased venous return to heart
May decrease SVR
—-REMEMBER the cardiac accelerator fibers that arise from T1-T4
How do you prevent the CV manifestations of a neuraxial blockage?**
CV effects prevention: Loading fluid bolus 10-20ml/kg * LUD (pregnancy) Trendelenbug Medications:** ATROPINE EPHEDRINE OR PHENYLEPHRINE EPINEPHRINE
What are the pulmonary manifestations of a neuraxial blockade?
Pulmonary:
—Usually minimal effects
Small decrease in VC due to loss of abdominal muscle contribution
–Diaphragm innervations C3-4-5
Even with total spinal phrenic nerve may not be blocked
Apnea should resolve after resuscitation
—BEWARE in patients with limited respiratory reserve
Accessory muscles NEEDED
What are the GU manifestations of a neuraxial blockade?
GU:
- –Little effect on renal BF
- -Loss of control of bladder function = urinary retention with bladder distention
What are the GI manifestations of Neuraxial Blockade?
GI:
—Sympathetic outflow originates T5-L1
Vagal tone dominance = small contracted gut with active peristalsis
–Hepatic blood flow decreases with MAP
What are the metabolic and endocrine manifestations of the neuraxial blockade?
Metabolic & Endocrine:
- –Surgery causes neuroendocrine response
- Neuraxial anesthesia can partially supress or totally block responses
- Decreases catecholamine release
- May reduce perioperative arrhythmias and ischemia
Neuraxial Blockade and Anticoagulation
Warfarin
Oral Anticoagulants (Warfarin)
Check PT/INR
Stopped 4-5 days prior
If only one dose was given within 24 hours of block – it is safe to proceed
Epidural removal in low dose warfarin (5 mg/d)
Neuraxial Blockade and Antiplatelet Agents
ASA & NSAIDs***
Antiplatelet Drugs ***
ASA & NSAIDS – do not increase risk of spinal hematoma
Ticlid = 14 day, Plavix = 7 days, Rheopro = 48 hours, Integrilin 8 hours
Neuraxial Blockade and Anticoagulation
Heparin
Standard Heparin
Minidose SQ not contraindicated
If getting heparin intraop – block must be done 1 hour prior at least
Check PTT
Neuraxial Blockade and Anticoagulation
Lovenox
LMWH (Lovenox)
Concern with epidural removal (1 hour prior to med or 10 hours after )
INR is <1.5
Neuraxial Blockade and Anticoagulation & Antiplatelet Agents
Fibrinolytic/Thrombolytic Therapy
Fibrinolytic/Thrombolytic Therapy
Avoid neuraxial anesthesia
Neuraxial Blockade and Anticoagulation & Antiplatelet Agents
Herbal Medication**
Herbal Medication
Feverfew, garlic, ginkgo or ginseng, glucosamine* and chondroitin** (similar to aspirin, see these last two in the elder generation)
No single evidence
One report of subarachnoid hemorrhage patient taking ginkgo