test 2 GP B

Question 1

Epidural Anesthesia history

Answer 1

Popularized epidural anesthesia in the 1950’s
Touhy Needle introduced in 1949
Lidocaine available in 1950’s
By the 1960’s it was popular amongst the obstetric population

Question 2

epidural technique and safety

Answer 2

Neuraxial techniques have proven to be safe when well managed
There is still a risk of complications: ranges from self limited back soreness to debilitating permanent neurological deficits and even death
Practitioners must: have expert knowledge of anatomy; pharmacology and toxic dosages of agents

Question 3

Epidural Anesthesia - today

Answer 3

Today neuraxial blocks are widely used for labor analgesia; caesarian section; orthopedic procedures; perioperative analgesia and chronic pain management

These blocks provide alternatives to general anesthesia or be used simultaneously with general or afterward for postoperative analgesia

Question 4

Epidural - Benefits of neuraxial blocks - Reduces incidence of?

Answer 4

venous thrombosis & pulmonary embolism
cardiac complications in high-risk patients
bleeding & transfusion requirements & vascular graft occlusion
pneumonia & respiratory depression following upper abdominal or thoracic surgery in patients with chronic lung disease
earlier return of Gastrointestinal function

Question 5

Epidural - Block benefits Rationale: (Proposed Mechanisms)

Answer 5

avoidance of larger doses of anesthetics and opioids
amelioration of the hypercoagulable state
sympathectomy-mediated increases in tissue blood flow
improved oxygenation from decreased splinting
enhanced peristalsis
suppression of neuroendocrine stress response to surgery
In patients with CAD, a decreased stress response results in less perioperative ischemia and reduced M & M
Reduction of parenteral opioid requirements – decrease atelectasis, hypoventilation, aspiration pneumonia and reduction of ileus duration
Postoperative epidural analgesia reduces time to extubating; preserves immunity thus reduces cancer spread according to some studies

Question 6

Epidural Blocks in the Obstetric Patient

Answer 6

Epidural anesthesia is widely used for analgesia in women in labor and during vaginal delivery
Caesarean section- most commonly performed under epidural or spinal anesthesia- both blocks allow a mother to remain awake for the birth of her child
Studies also show Blocks = less maternal M & M than GETA (largely d/t incidence of aspiration and failed intubation)

Question 7

Definition of Epidural Anesthesia

Answer 7

It is the reversible chemical blockade of neuronal transmission produced by the injection of a LA drug into the epidural space

It interrupts transmission of sensory, autonomic, and motor nerve fiber transmission in the anterior and posterior nerve roots

Question 8

Disadvantages of Epidural

Answer 8

Time consuming to perform
May require 10-20 minutes to establish a level
Sympathetic blockade
Surgeon complains “It takes to long”

Question 9

Advantages of epidural

Answer 9

Predictable
Pt can remain fully conscious
Analgesia can be extended into the post-operative period
Can provide a segmental blockade
Ideal for lower abdomen, pelvis/perineum, or lower extremities
Reduce risk of thrombosis

Question 10

Anatomy spinal cord

Answer 10

Question 11

Vertebral column is made up of 33 Vertebrae

Answer 11

Cervical: 7 (C1-C7)
Thoracic: 12 (T1-T12)
Lumbar: 5 (L1-L5)
Sacral: 5 fused (S1-S5)
Coccygeal: 4 fused to form coccyx

Vertebrae differ in shape and size at the various levels
1st cervical vertebra (atlas)- lacks a body and has unique articulations with the base of the skull
2nd cervical vertebra (axis)- has atypical articular surfaces
All 12 thoracic vertebrae- articulate with their corresponding rib
Lumbar vertebrae- have large anterior cylindrical body
When all stacked vertically the hollow rings become the spinal canal (where the cord and its coverings sit)
Individual vertebral bodies are connected by intervertebral disks

Question 12

Spinal Ligaments- (superficial to deep)

Answer 12

Interspinous ligament
Ligamentum flavum
Posterior longitudinal ligament
Anterior longitudinal ligament

Question 13

spinal cord anatomy cont. what it contains; 3 layers; where is CSF?

Answer 13

Spinal canal contains the cord with coverings (meninges) fatty tissue, and venous plexus
Meninges- 3 layers: pia mater, arachnoid mater and dura mater (contiguous with cranial counterparts)
Pia mater- closely adherent to the spinal cord
Arachnoid mater- closely adherent to the thicker and denser dura mater
CSF- contained between the pia and arachnoid mater in the subarachnoid space

Question 14

The Spinal Cord cont. anatomy - epidural space?

Answer 14

Epidural space (potential space)- within the spinal canal bounded by the dura and the ligamentum flavum
Extends from the foramen magnum to the level of L1 in adults
In children the spinal cord ends at L3 and moves up with age
Lower spinal nerves form the cauda equine (horse’s tail)

*Performing lumbar (subarachnoid) puncture below L1 in adults and L3 in children usually avoids potential needle trauma to the cord; damage to the cauda equine unlikely*

Question 15

epidural Mechanism of Action

Answer 15

Interruption of efferent autonomic transmission at the spinal nerve roots =
Sympathetic Blockade
The physiological responses of neuraxial blockade =
decreased sympathetic tone/ unopposed parasympathetic tone
Sign and Symptoms:
drop in BP
decrease in HR
arterial vasodilation- decreased SVR

Question 16

Clinical Considerations
As a primary anesthetic, neuraxial blocks are most useful:

Answer 16

As a primary anesthetic, neuraxial blocks are most useful:
lower abdominal
inguinal
urogenital
rectal
lower extremity surgeries
Upper abdominal procedures such as gastrectomy have been performed with spinal or epidural anesthesia- can be difficult to safely achieve adequate sensory level for patient comfort

Question 17

epidural Pre-op Preparation

Answer 17

Discuss plan with the surgeon
Good choice for pt.’s with coexisting pulmonary disease
Discuss the proposed surgery and explain the epidural technique in detail
Interview must be unhurried
Answer all questions
Do not coerce the patient into an epidural anesthetic
Do a full pre-operative assessment and interview

Question 18

Informed consent
epidural?
and Preop meds

Answer 18

Informed consent

Make sure you document that you have discussed the advantages & disadvantages of the anesthetic
Discuss risk
GA is plan B
Document
Pre-op meds
Pt should be NPO
Do not over sedate the patient
OB patients are not sedated
Midazolam (titrate to effect)
Opioids

Question 19

Epidural Indications

Answer 19

An epidural can be employed as a component of a “balanced” regional/general anesthetic
Pt has a full stomach
Upper airway anomalies
Urological procedures
TURP
Lower limb surgery
Post-op pain relief
Obstetrics

Question 20

Absolute contraindications epidural

Answer 20

Patient refusal
Severe psychiatric disease
Aortic/mitral stenosis or asymmetric septal hypertrophy
Preexisting CNS disease
Herpetic infection
Increased ICP
Coagulopathy
Infection at the site
Septicemia or bacteremia
Allergy to LA

Question 21

Absolute contraindications spinal

Answer 21

Patient refusal
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

Question 22

Relative contraindications to epidural

Answer 22

HIV infections
Surgery of unknown duration
Untreated chronic HTN
Surgical procedures above the umbilicus
Obesity/ deformities of the spinal column
Chronic HA or backache
Multiple attempts
Minor blood clotting abnormalities
ASA or mini heparin doses
Check coags

Question 23

Relative contraindications spinal

Answer 23

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
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

Question 24

Patient Preparation Epidural

Answer 24

Baseline VS & Pt must have an IV
Standard monitors
BP & ECG
Pulse-ox & Stethoscope
Suction
Equipment to provide positive pressure ventilation
O2 & ambu-bag
Mask & airway equipment
Supportive meds
Versed & Succinylcholine
Ephedrine, atropine, & IV fluids (Resuscitation drugs)

Question 25

Patient Preparation Epidural

Answer 25

Baseline VS & Pt must have an IV Standard monitors BP & ECG Pulse-ox & Stethoscope Suction Equipment to provide positive pressure ventilation O2 & ambu-bag Mask & airway equipment Supportive meds Versed & Succinylcholine Ephedrine, atropine, & IV fluids (Resuscitation drugs)

Question 26

Procedure Epidural technique

Answer 26

Can be done in the sitting or lateral position Make sure the patient is on an adjustable bed Make sure someone is there to support the patient Not the spouse or family member Inform the patient of what to expect throughout the procedure Make sure pt. has an IV, monitors, and O2 Palpate the back Superior aspects of the iliac crest and the spinous process L4 or L4-5 May be difficult to palpate in the obese patient Use the largest and most superficial interspace you can find L2-3 Set up equipment Sterile technique Draw up the LA to be used for the skin wheal in a 3 ml plastic syringe Draw 2-3 ml of preservative free saline into the 5 ml glass syringe Check integrity of epidural catheter Loading and maintenance dose should be drawn up in separate syringes Cleanse the patient skin Place fenestrated drape over the proposed site of injection Full or half drape Make sure you remove all chemicals from the injection site ID the spinous process of L3-4 Midline approach Loss of resistance technique Raise a skin wheal with the 27-gauge needle Raise a small intradermal skin wheal of LA Recheck overall position of the patient Grasp the Touhy needle with stylet, between the thumb and index finger of your dominant hand and place it over the middle of your thumbnail and through the skin wheal As you advance through the ligaments you will notice an increase in resistance as you pass the ligamentum flavum Ligamentum flavum is normally 4 cm from the skin Remove the stylet and attach the 5ml glass syringe Loss of resistance technique Air vs saline

Question 27

Midline approach epidural layers:

Answer 27

Technique: Midline Approach Layers you will penetrate with needle: Skin Subcutaneous tissue and fat Supraspinous ligament Interspinous ligament Ligamentum flavum Epidural space

Question 28

Paramedian Approach - epidural layers and technique for paramidian

Answer 28

Technique: Paramedian Approach Layers you will penetrate with needle: Skin Subcutaneous tissue and fat Paraspinous muscle Ligamentum flavum Epidural space Technique: Make a skin wheal 1-2 cm lateral to the midline directly opposite the upper edge of the spinous process below the selected interspace Direct needle medially and cephalad additional technique: epidural : Once you have identified the epidural space: Gently aspirate to verify you are not in the subarachnoid space or intravascular Test dose One shot technique or insert an epidural catheter

Question 29

Equipment Epidural - **Touhy Needle**

Answer 29

Epidural needle 3.5 inches long 17-18 gauge Has an inner stylet that prevents occluding the lumen with tissue Rounded tip to prevent puncture of the dura and easier to thread the catheter

Question 30

Equipment epidural **Epidural Catheter**

Answer 30

1st marking= 5 cm Each marking after that is 1 cm 2nd double marking= 10 cm Thick mark is 11 cm (tip of needle) When inserted to this point you are at the tip of the needle in the epidural space 3rd triple mark= 15 cm Single hole at the end vs multiple ports on its distal side

Question 31

Skin to epidural space

Answer 31

4-6 cm in 60% of patients 2-4 cm in 25% of patients 6-8 cm in 10% of patients \>8 cm in 5% of patients Will usually leave 3-4 cm of catheter in the epidural space

Question 32

Dr Havenstein’s Anecdotes: Epidural

Answer 32

When advancing the catheter the patient may feel transient paresthesia's May not aspirate CSF in the needle but the catheter may puncture dura and you will get CSF Be careful when removing the needle after the catheter is placed An antibacterial filter is attached to the end of the catheter

Question 33

Epidural Test dose

Answer 33

A negative aspiration does not ensure you are not in a vessel or the subarachnoid space Test dose 3 ml of 1.5-2% Lidocaine with 1:200,000 epinephrine This dose will only produce a T10 block if injected in the CSF 1.5% is 15mg per ml 45; and 1:200,000 epi is 5mcg per ml = 15 mcg of epi

Question 34

Epidural test dose symptoms

Answer 34

Observe the patient Ask the patient to report symptoms “feeling different, ringing in the ears or metallic taste in the mouth” Intravascular injection Increase in HR of 15-20 bpm for 2-3 minutes Systemic toxicity- numb tongue, dizziness, ringing in the ears Subarachnoid injection (3-5 minutes) Immediate onset of sensory and motor block in the buttocks and lower extremities (T10 block) Subdural Produce a high block

Question 35

if epidural test dose is negative

Answer 35

Administer the pre-calculated volume in 3-5 ml increments every 60 seconds Tape the catheter in place Document the marking of the catheter at the skin

Question 36

Evaluation of epidural

Answer 36

Onset is slower than a spinal After repositioning evaluate patient for 10-30 minutes Evaluate BP, ECG, and pulse ox Measure BP every minute for the first 3-5 minutes then every 2-3 minutes until the block is set Determine the level of blockade every 2-3 minutes with an alcohol sponge and then a sharpened device until the level is set. Check level every 30-45 minutes

Question 37

Distribution of Local Anesthetics Epidural

Answer 37

The distribution of the LA in the epidural space is dependent on the **volume i**njected Positioning will not aide in distribution of the local (per book but it helps in clinical) \*The primary objective of the epidural is to block the afferent fibers located in the dorsal roots

Question 38

Site of Action of Local epidural

Answer 38

Ultimate target are the spinal nerves & roots The dura serves as a barrier to diffusion of Local Most is absorbed into the circulatory system some will stay in the epidural space and the rest will enter the spinal nerves and nerve roots The Local will spread horizontally and longitudinally once in the epidural space Blockade of fibers occurs quickly Blockade is 2 dermatomes higher than sensory Effects accentuated in the hypovolemic patient A quick drop in BP may be an early sign that a “spinal” is setting up Rapid decrease in BP- nausea or dizziness Cardioaccelator fibers

Question 39

physiology Temperature & Light Touch

Answer 39

Unmyelinated C & myelinated A-delta fibers Follows autonomic blockade Alcohol sponge Correlates with sensory loss May report lower extremity feels warm

Question 40

Initial Motor Impairment & Touch

Answer 40

Myelinated A-beta & A-gamma Onset of motor weakness and impaired perception of strong tactile stimulation Follows loss of temperature and touch (sharpened device)

Question 41

Profound Motor & Proprioception

Answer 41

Myelinated A-alpha fibers Profound motor block develops with loss of proprioception Feel “Phantom Limb” Assess motor block Dorsiflex feet (S1-S2) Flex toes (L4-L5) Raise knees (L2-3) Lift shoulders of the bed (T6-T12) Assess motor block if there then they cant do action

Question 42

Desired Level of Block epidural

Answer 42

Will be determined by the **_volume and concentration_** of drug and the level of the epidural catheter placement Injection of 10-15 ml of LA into the epidural space in the lumbar area will produce a T7-9 level in the average sized patient

Question 43

**Inadequate Block epidural**

Answer 43

The concentration or volume of the drug may have been too weak to penetrate spinal nerves If the block does not reach the desired level, you can give a top off dose One-half of the initial volume can be reinjected Wait 10-15 minutes before reinjection

Question 44

Dosing Epidural

Answer 44

Volume is the key factor in the height of the block The guideline for dosing an epidural in adults is 1–2 ml per segment to be blocked. Adjust the guideline for shorter patients (\< 5 ft. 2 in.) or taller patients (\> 6 ft. 2 in.). Example: T10 block from L3-4 injection: 6-12 ml of local anesthetic.

Question 45

Local anesthetic epidural

Answer 45

The type, volume, and total dose administered will vary with the level and duration of block desired LA drugs reversibly interrupt nerve impulse conduction by interfering with sodium ion conductance The membrane is unable to depolarize, preventing propagation of impulses

Question 46

Local anesthetic Epidural potency

Answer 46

Potency Equal to lipid solubility Higher lipid soluble, the more readily it penetrates neuronal membranes Better able to penetrate A-alpha motor fibers

Question 47

Local Anesthetic Epidural ## Footnote Rate of onset

Answer 47

Rate of onset Determined by pKa Weak bases pKa near physiologic ph will move more readily into nerve membranes The neutral (non-ionized) form is most readily able to penetrate the neuronal membrane

Question 48

Local anesthetic: duration of action

Answer 48

Determined by potency and protein binding Highly protein bound agents are less available for systemic absorption

Question 49

Local anesthetic - most common

Answer 49

Bupivacaine Ropivacaine Lidocaine Mepivacaine 2-chloroprocaine

Question 50

Distribution and Uptake of Local anesthetic (LA)

Answer 50

The spinal nerves in the epidural space are larger and covered by arachnoid and dura matter It takes 6-8 times the dose (mass) of LA to accomplish the same blockade as a spinal Epidural veins

Question 51

What factors influence the level and duration of action? LA

Answer 51

Volume, dose, and concentration Larger **volume** injected into the epidural space the greater vertical spread Increase in **dose** will produce intense analgesia and prolonged duration of action Increase in **concentration** will produce a faster onset and more intense block

Question 52

Why do we use Epinephrine 1:200,000

Answer 52

Marker for intravascular injection Prolong duration of action of Locals

Question 53

What factors influence the level and duration of action? LA

Answer 53

Level and rate of injection The closer the injection site is to the spinal nerve to be blocked, the more rapid the onset of analgesia Slowly titrate LA into the epidural space (3-5 ml increments) Patients can complain of HA Will not detect intravascular injection Patient position Does not really affect it (According to texts, but in clinical practice it DOES affect it) Age Extremes of age does not affect spread Older patients require half the dose as younger patient Height does not affect the dose Weight Where may be a larger cephalad spread in the obese patient May need to decrease the dose in the obese patient Pregnancy Need a lower dose due to the engorgement of epidural veins Hormones They need 1/3 the dose of LA than the normal person

Question 54

Re-dosing the Epidural

Answer 54

During the anesthetic do not allow the level of blockade to recede If the pt. has an adequate level but not a solid block Redose with a top-up dose or 20% of the initial volume Will increase intensity of the block but not the height of the block If the level has regressed 1-2 dermatomes Redose with ½ to 1/3 of the initial volume

Question 55

**Complication S/S of Local Anesthetic toxicity CNS**

Answer 55

CNS: numbness of the lips & tongue, dizziness, lightheadedness, visual & auditory disturbance, disorientation, drowsiness, and convulsions

Question 56

**Complication S/S of Local Anesthetic toxicity - CV**

Answer 56

CV: ECG changes, cardiovascular depression, cardiac arrest

Question 57

How do we treat local anesthetic toxicity?

Answer 57

Treatment of LA toxicity Listen to the patient!!!! Supportive care Seizure: Manage airway, Propofol, Benzodiazepine Goal is to interrupt seizure activity Assure airway patency CV Collapse ACLS Atropine and epinephrine Cardiopulmonary bypass Intravenous lipids **Lipid Rescue** If patient exhibits s/s of LA toxicity Get help Initial focus Airway Seizure control BLS/ACLS Infuse 20% Lipid Emulsion Avoid vasopressin, Ca+ channel blocker, B-blockers, or LA Get bypass machine ready

Question 58

Spinal history, definition, goal

Answer 58

First performed in the late 1890’s Definition It is the reversible chemical blockade of neuronal transmission produced by injection of a LA into the CSF contained in the subarachnoid space Goal Render patient insensitive to surgical stimuli while producing minimal physiologic alteration

Question 59

Advantages spinal

Answer 59

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

Question 60

Disadvantages spinal

Answer 60

**Sympathetic blockade 100%** of the time Hypotension Intense motor blockade May last for hours post-op Surgeons complain “It takes to long”

Question 61

Pre spinal considerations

Answer 61

Discuss your plan for a spinal anesthetic with the surgeon Good choice for procedures of the mid to lower abdomen and lower extremity Good choice for pt.'s with pulmonary disease Level should not exceed T4 Discuss the surgical procedure and your choice of anesthetic to the patient Conduct an unhurried interview Full pre-op assessment Airway Many pt.'s concerned about being awake Allay fears Do not coerce your pt. into a spinal Age is not a limiting factor Not a good choice for major intra-abdominal procedures Balanced regional/general anesthetic Full stomach Retain protective airway reflexes Airway anomalies Urological procedures TURP Obstetrics Vaginal of cesarean delivery Does not affect major organ function

Question 62

Spinal Monitors needed for procedure

Answer 62

Document baseline VS Document labs on the chart Must monitor the pt. during the placement of any regional anesthetic BP, ECG, Pulse-ox OB patient- FHR Oxygen by N/C Pt must have an IV Airway equipment Suction, Resuscitation equipment & Supportive meds going to only do in OR cant waste time

Question 63

spinal site

Answer 63

One of four intervertebral spaces L2-S1 Popular site L2-3 or L3-4 Place patient on an adjustable bed Explain procedure to the patient IV, monitors, O2, & resuscitation equipment Lateral or sitting position Pt condition Practitioner preference

Question 64

Lateral position for spinal

Answer 64

Comfortable for the pt., easiest to maintain, and minimizes chances of fainting If doing block for an extremity and using a hyperbaric solution, place the operative site down Make sure the hips & shoulders are at the edge of the table and perpendicular

Question 65

Sitting Position for Insertion spinal

Answer 65

Sitting position is commonly used It ensures maximum anterior flexion of the spinal column It is easier to ID the midline and assess anatomical angles It preserves the natural alignment and curvature of the spine

Question 66

Spinal technique part 1

Answer 66

Draw the Local to be used for a skin wheal into a 3ml syringe (1% lidocaine) Draw the Local for the CSF into a 5ml syringe Cleanse the patient’s skin over the planned injection site with disinfectant Place the drape over the site of injection Remove all chemicals from the site of injection ID L2-3 interspace

Question 67

Spinal technique approach midline - layers

Answer 67

Layers you will penetrate with needle: Skin Subcutaneous fat Supraspinous ligament Interspinous ligament Ligamentum flavum Dura mater Subdural space Arachnoid mater Subarachnoid space- CSF

Question 68

Spinal technique approach Paramedian - layers

Answer 68

Paramedian Approach Layers you will penetrate with needle: Skin Subcutaneous fat Paraspinous muscle Ligamentum flavum Dura mater Subdural space Arachnoid mater Subarachnoid space- CSF

Question 69

How to evaluate spinal block

Answer 69

Begin to assess blockade immediately Evaluate BP, ECG, pulse-ox, and respiration Assess BP every 3-5 minutes until block is set Play close attention to mentation Determine the progress of the block every minute First with an alcohol sponge Then with a sharp device (tongue blade) Once level is achieved assess every 30-45 minutes Determine dermatome level May adjust the horizontal angle of the table to increase or stop the spread of the Local

Question 70

Spinal autonomic blockade response

Answer 70

Autonomic Blockade 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

Question 71

spinal- temperature and light touch

Answer 71

Temperature and Light Touch Innervated by the unmyelinated C and myelinated A-delta fibers Loss of these follows autonomic blockade How to assess these fibers? Alcohol sponge Loss of temperature correlates with sensory loss

Question 72

spinal- Motor impairment and touch

Answer 72

Motor Impairment and Touch Myelinated A-beta & A-gamma Loss of motor & touch follows loss of light touch and temperature discrimination Differential block Motor block is 2 dermatomes below sensory block Use a sharpened device or pinch method to assess level DO NOT USE A NEEDLE

Question 73

Spinal profound motor block

Answer 73

Profound Motor Block Myelinated A-alpha Motor block and loss of proprioception 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 Assess block S1-2- dorsiflex his feet L4-5- flex his toes L2-3- raise his knees T6-T12- lift shoulders off the bed

Question 74

spinal - Desired level of block S2-5

Answer 74

Desired level of block S2-5 Saddle block No affect on the ANS Surgical anesthesia limited to perineum, perianal, & genitalia

Question 75

spinal- Desired level of block T10

Answer 75

T10 (umbilicus) Low spinal Blocks S1-5 & L1-5 Produce vasodilation, lower BP Good for GYN, vaginal delivery, lower extremity surgery, TURP, & cysto

Question 76

spinal - Desired Level of Block Continued T4

Answer 76

T4 (nipple) High spinal Used for upper abdominal surgery Can feel traction Can cause vasodilation and block cardioaccelator fibers

Question 77

Spinal- Desired Level of Block C8

Answer 77

C8 (little finger) Total spinal Difficulty breathing Can lead to respiratory & cardiac arrest

Question 78

Equipment - spinal needle

Answer 78

Spinal Needles Single use Has a stylet to prevent occluding lumen Most are 3-3.5 inches (7.5-9cm) long In obese pt.'s you may need a longer needle (5 inches) Classified as cutting or spreading Quincke, Whitacre, & Sprotte

Question 79

Equipment- needle gauge

Answer 79

Needle gauge Smaller gauge allows less CSF leak, difficult to insert, aspirate CSF, & inject medication (25-26 gauge) Larger gauge improves tactile feel, higher risk of PDPH (20-22 gauge) Most clinicians will use the 25-26 gauge needle placed through an introducer

Question 80

spinal pharm - lidocaine

Answer 80

Lidocaine 2ml ampule of 5% (50mg/ml) solution premixed with 7.5% dextrose- hyperbaric Risk of “Cauda equina syndrome” with this mixture

Question 81

Spinal pharm procaine

Answer 81

Procaine 2ml ampule of 10% (100mg/ml) solution Short duration, low potency Solutions of greater than 5% concentration are linked to neurotoxicity

Question 82

Spinal pharm tetracaine

Answer 82

Tetracaine 2ml ampule of 1% (10mg/ml) Provides a more profound motor block

Question 83

Spinal pharm Bupivacaine

Answer 83

Bupivacaine 2ml ampule of 0.75% (7.5mg/ml) with 8.25% dextrose- packaged hyperbaric Onset of 3-5 minutes Less motor block than tetracaine

Question 84

Pharm pic of the spinal local anesthetics

Answer 84

Question 85

What if I add vasoconstrictors to my spinal?

Answer 85

Vasoconstrictors When added to LA it will constrict the blood vessels at the site and slow absorption of the LA They can produce analgesia It will prolong the duration of action of ester LA (procaine, tetracaine) Does not prolong the action of bupivacaine Does prolong the action of lidocaine Does not affect the spread of the block

Question 86

Spinal pharm - epinephrine

Answer 86

Epinephrine Alpha-1 adrenergic agonist Can produce analgesia when placed directly on the spinal cord

Question 87

Spinal pharm phenylephrine

Answer 87

Phenylephrine Pure alpha-adrenergic agonist Not as popular

Question 88

Spinal intrathecal opioids?

Answer 88

Intrathecal Opioids Will not produce surgical analgesia Does provide better anesthesia when combined with LA

Question 89

Spinal intrathecal opioid fentanyl pharm

Answer 89

Fentanyl Dose- 15-25 mcg Higher doses produce respiratory depression, itching, and urinary retention Onset 5-10 minutes Duration 2-4 hours

Question 90

Spinal intrathecal opioid sufentanyl pharm dose

Answer 90

Sufentanyl Not commonly used Dose 2-4 mcg

Question 91

Spinal intrathecal opioid meperidine pharm dose

Answer 91

Meperidine Preservative free 5-50mg of 5% solution

Question 92

spinal intrathecal opioid morphine pharm dose, duration, onset

Answer 92

Morphine (preservative-free) Most commonly used Onset of 60-90 minutes Dose 0.1-0.5mg Provide profound analgesia for 18-27 hours

Question 93

Physiology How does a spinal work?

Answer 93

It temporarily interrupts transmission of impulses along sensory, autonomic, and motor nerve fibers located in the anterior and posterior nerve roots Primary site of action Spinal nerve root and dorsal root ganglia

Question 94

The 3 most important factors in determining distribution of Local Anesthetics

Answer 94

Baricity of the LA Position of the patient during and just after injection Dose of the anesthetic injected

Question 95

**Baricity spinal physiology**

Answer 95

It is the density of the LA at a specific temperature divided by the density of the CSF at the same temperature \*\*\*Density of CSF 1.004-1.008\*\*\* This determines where the LA will distribute

Question 96

Hyperbaric Spinal physiology what is density, which direction, position changes

Answer 96

Hyperbaric (moves down sinks) Solution that has a density greater than the CSF (\>1.008) Dextrose is used to make solution hyperbaric Most commonly used Allows us to inject at the lumbar area then place pt. in slight Trendelenburg position and allow the LA to move cephalad to bathe the upper lumbar and thoracic nerve roots Sitting the pt. after injection of LA for 3-5 minutes after injection confines the LA to the lower lumbar and sacral roots (saddle block)

Question 97

Hypobaric spinal physiology - density, direction, amount

Answer 97

Hypobaric ( rise goes up ) Solution that has a density less than the CSF where injected (\<1.008) It will float up to the least dependent area within the spinal cord Diluted with preservative free sterile water Very dilute solutions require a larger volume of LA to deliver an effective mass of drugs 5-10mL

Question 98

Isobaric spinal physiology

Answer 98

Isobaric Limited clinical application They do not spread with position change and are ideal when repositioning is required Difficult to obtain a high level

Question 99

Does patient position matter-spinal LA?

Answer 99

Patient Position Plays a significant role following injection of the LA Most evident with hyperbaric solutions Normally the level is fixed in 5-10 minutes

Question 100

Cardiovascular complications - spinal

Answer 100

Cardiovascular Blockade of sympathetic fibers Blockade of cardioaccelator fibers Causes hypotension and bradycardia BP is decreased by 15-20% in most healthy pt.'s

Question 101

with cardiovascular complication how do we treat hypotension? spinal

Answer 101

How to treat hypotension? Try to prevent it Preload Prophylactic administration of 1-2L of crystalloid Supplementary O2 In pt.'s with essential HTN Treat drops in BP aggressively Treatment Slight head down position- Trendelenburg Bolus of crystalloid Ephedrine 5-10mg IV

Question 102

What is PDPH? complication

Answer 102

Spinal ## Footnote PDPH (spinal headache)- Post-Dural puncture headache (PDPH) Cephalgia that is occipital and radiates to the frontal or orbital regions Cervical muscle spasms Symptoms are postural Get worse when the pt.'s head is elevated Nausea, vomiting, photophobia, tinnitus, dizziness, and cranial nerve palsies Caused by Dural puncture and continuous leak of CSF Reduces CSF pressure

Question 103

Treatment of PDPH

Answer 103

Treatment of PDPH Will resolve within 5-7 days Conservative therapy for 24 hours Bed rest, hydration, analgesics, and IV caffeine Epidural blood patch Autologous blood is injected into the epidural space (like 20cc?) Blood will move in the cephalad direction so inject one interspace below The injected blood will increase subarachnoid and epidural pressure and form a clot sealing the dural tear

Question 104

Local anesthetics Amides vs Esters

Answer 104

LA classified according to chemical structure All LA are weak bases Chemical structure amine group on one end connect to aromatic ring on the other and amine group on one side Amine end is hydrophilic and aromatic end is lipophilic **Amides** Link between intermediate chain and aromatic ring; Metabolized in liver Metabolized by microsomal P-450 enzymes; Rate of metabolism prilocaine\>lidocaine\>mepivacaine\>ropivacaine\>bupivacaine **Esters** Ester link between intermediate chain and aromatic ring Metabolized by pseudocholinesterase; Hydrolysis is very rapid Procaine and benzocaine is metabolized by PABA CSF lacks esterase enzymes so termination of action of ester depends on redistribution to bloodstream

Question 105

What are the amides that I should know?

Answer 105

Amides ( two Is) Bupivacaine Lidocaine Ropivacaine Etidocaine Mepivacaine

Question 106

What are the esters I should know LA

Answer 106

Esters Cocaine Procaine Tetracaine

Question 107

Amides vs Esters LA- cont. what part is hydrophilic what part is lipophilic? what happens at nerve membrane

Answer 107

**Amides** Hydrophilic ring is soluble in water Solution remains on ether side of the nerve membrane Dentist **Esters** Aromatic end is lipophilic Nerve cells made of lipid bilayer Anesthetic molecule penetrate through nerve membrane

Question 108

Allergy and metabolism LA ester vs amide

Answer 108

Allergy or cross-sensitivity occurs with ester linkage Esters metabolized to metabolite PABA Esters rapidly metabolized in plasma by cholinesterase Amides slowly destroyed by liver microsomal P450 enzymes

Question 109

Local anesthetic long winded method of action

Answer 109

Nerve fibers classified according to their size, conduction velocity and function Large nerve size+ myelin sheath=fast conduction velocity Myelin-electrical insulation of nerve fibers and rapid impulse transmission Transmission of electrical impulses along nerve membrane=signal transduction along nerve fibers Resting membrane potential -60-70 mV by active transport and passive diffusion of ions Na+/K+ pump; Transport of 3 Na+ ions out of the cells for every 2 K+ into cells Na+ channels are membrane bound proteins that composed of one large alpha subunit and two smaller beta subunits LA bind a specific region of alpha subunit and inhibits voltage gated sodium channel, preventing channel activation, inhibiting Na+ influx=membrane depolarization Action potential can no longer be generated and impulse propagation is abolished Conduction is blocked and anesthesia is created Sensitivity of nerve fibers to LA is determined by axonal diameter, myelination and other factors Onset of action of LA depends on lipid solubility and pKa pKa is pH at which fraction of ionized and nonionized drug is equal Less potent less lipid-soluble agent have faster onset then more potent more lipid-soluble agents **SUMMARY** Summary of Method of Action Membrane stabilizing medications Slow down speed of AP/stop AP generation Inhibit Na+ influx in the neuronal cells Bind to Na+ channels DOA correlates with potency and lipid solubility

Question 110

5 Factors Affecting Local Anesthesia Action

Answer 110

_Lipid solubility_ Increasing lipid solubility leads to faster nerve penetration, block sodium channels and speeds up onset of action _Influence of pH_ Lower pKa (7.6-7.8) faster acting-lidocaine and mepivacaine Higher pKa (8.1-8.9) slower acting –procaine, tetracaine and bupivacaine _Vasoconstrictors_ Epinephrine; Prolongs block, increases intensity and decreases absorption; Antagonizes vasodilating effect of LA _Opioids_ Synergistic analgesia Spinal anesthesia attenuation of C-fibers _Alpha 2 adrenergic agonists_ Clonidine inhibitory effect on peripheral nerve conduction Analgesia via supraspinal and spinal adrenergic receptors

Question 111

**Pharmacokinetics LA-**

Answer 111

Absorption Mucous membranes minimal barrier Systemic absorption depends on the blood flow Rate of systemic absorption related to vascularity IV\>tracheal\>intercostal\>paracervical\>epidural\>brachial plexus\>sciatic\>subcutaneous Addition of epi or phenylephrine=vasoconstriction Decreased absorption reduces the peak concentration of LA in blood, enhances quality of analgesia, prolongs DOA and limits toxicity Distribution Depends on organ uptake Determined by: Tissue perfusion Tissue blood partition coefficient Tissue mass

Question 112

LA rate of systemic absorption

Answer 112

IV\>tracheal\>intercostal\>paracervical\> epidural\>brachial plexus\>sciatic\>subcutaneous

Question 113

local anesthetic Effects on the Organ Systems (Neurological)

Answer 113

Effects on the Organ Systems Neurological CNS is vulnerable to LA toxicity Early sx: circumoral numbness, tongue paresthesia, dizziness, tinnitus, blurred vision Late sx: clonic-tonic seizures Excitatory sx: restlessness, agitation, nervousness Highly lipid soluble LA produce seizures at lower blood concentration

Question 114

Local anesthetic Effects on the Organ Systems (Respiratory)

Answer 114

Respiratory Relax bronchial smooth muscles Phrenic nerve paralysis Depression of hypoxic drive

Question 115

LA effects on the organ system (cardiovascular)

Answer 115

Cardiovascular Depress myocardial automaticity Unintentional IV injection of bupivacaine may produce severe CV toxicity Left ventricular depression, AV block, arrhythmias Decreased cardiac excitability and contractility Decrease conduction rate Increased refractory rate Hypotension

Question 116

Local Anesthesia Toxicity

Answer 116

Toxicity is the peak circulation levels of LA Important to calculate max dose- I am asked all the time what is the max Please reference your max doses in your text books Related to absorption from the site Light headiness, tinnitus, seizure, CV collapse Rate of absorption, distribution and metabolism Absorption depends on speed of administration and level of doses Distribution allows absorption to occur in 3 phases Highly vascular tissue (lungs and kidneys) then less vascular tissue (muscle and fat), then drug is metabolized Metabolism involves chemical structure as we have already discussed

Question 117

\*\*\*Must know max doses of LAs\*\*\*

Answer 117

Question 118

Key concepts LA

Answer 118

Na channels Sensitivity of nerve fibers Onset of action Duration of action Rate of systemic absorption Metabolism of esters and amides CNS is vulnerable to LA Major CV toxicity requires 3 times the local anesthetic concentration in blood as that requires to produce seizures

Question 119

Choice of Local Anesthetics 3 most important factors of distribution of LA

Answer 119

**Baricity** Position of the patient during and after injection **Dose** of the anesthetic injected Remember baricity, dose, volume, specific gravity Position during after injection **Height** Spinal column anatomy Decrease CSF volume-increased intraabdominal pressure

Question 120

LA spinal pic choice

Answer 120

Question 121

Epidural vs spinal pic

Answer 121