Mod VII: EPIDURAL ANESTHESIA Flashcards by Olivier Mba

When a local anesthetic (may also add opioid, epi, bicarb) is injected into the epidural space, initially blocking spinal nerve roots and then diffusing into the subarachnoid space creating a conduction blockade of the spinal nerves, this technique is known as:

Epidural Anesthesia (EA)

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_{Epidural Anesthesia (EA)}

Placement of a flexible catheter into the epidural space via needle, remains in place for

the anesthetic and dosing is intermittent/continuous

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_{Epidural Anesthesia}

Indications for EA

Sole anesthetic for operations below the umbilicus

^{Lower extremities (esp. hip and knee)}

^Pelvis

^Perineum

^{Lower abdomen}

^{Obstetrical procedures (very popular in this population)}

Adjunct anesthetic or post-op pain control

^{Upper and lower abdominal procedures}

^{Thoracic procedures}

Treatment of Acute / Chronic pain

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_{Epidural Anesthesia (EA)}

Advantages: (compared to GA)

Similar to spinal anesthesia!!!

Awake patient, reflexes

Decreased stress response

Decreased cost

Early ambulation, eating, less PONV

Decreased blood loss

Postoperative analgesia

Flexibility

Increased patient satisfaction

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_{Epidural Anesthesia (EA)}

Disadvantages

Technically more difficult to place

Takes longer to set up than SAB or GA

Less dense block than SAB

Catheter may migrate from epidural space

Less reliable (higher failure rate or patchy block)

Greater chance for LA toxicity

Infection

Epidural hematoma

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_{Epidural Anesthesia (EA)}

Absolute Contraindications

Inadequate resuscitation drugs or equipment

Patient refusal or uncooperative

Uncorrected coagulopathies

Infection at site of injection

Septicemia

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_{Epidural Anesthesia (EA)}

Relative Contraindications

Hypovolemia

Fixed CO states

Anatomical deformities of spine

Neurological disease

Increased ICP

Chronic back pain

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_{Epidural Technique}

Most components are very similar to spinal administration - including:

Patient position, prep, drape, local

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_{Epidural Technique}

Major difference in technique between epidural and spinal are:

Introduction of tuohy needle

Identification of epidural space

Threading the catheter

Removal of tuohy needle

Test dose of catheter

Securing catheter for dosing

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_{Epidural Technique}

Technique for dentification of epidural space

Loss of resistance technique

(to be demonstrated in lab)

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_{Epidural Anesthesia (EA)}

Dosing Techniques

Test Dose

LA solutions should be injected in increments of 3-5 ml every 3-5 minutes (always aspirate prior to injecting) and titrate to desired anesthetic level

Block should set up in about 20 min.

When block recedes 1-2 dermatone levels, re-dose with 30-50% of initial dose to maintain initial level of anesthesia (if continuous infusion, increase rate or concentration)

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_{Epidural Anesthesia (EA) - Dosing Techniques}

How should LA solutions be injected?

In increments of 3-5 ml every 3-5 minutes

Always aspirate prior to injecting

Titrate to desired anesthetic level

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_{Epidural Anesthesia (EA) - Dosing Techniques}

Block should set up in about

20 min.

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_{Epidural Anesthesia (EA) - Dosing Techniques}

What could you do When block recedes 1-2 dermatone levels in order to maintain initial level of anesthesia ?

Re-dose with 30-50% of initial dose to maintain initial level of anesthesia

If continuous infusion, increase rate or concentration

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_{Epidural Anesthesia - Assessment of block}

Three classes of nerves blocked:

Autonomic nervous system

Sensory nerves

Motor nerves

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_{Epidural Anesthesia - Assessment of block}

Dermatomes

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_{Epidural Anesthesia (EA)}

Factors influencing spread of LA in the epidural space

Injection site (Most important determinant)

Drug Volume

Drug Dose

Drug concentration

Patient position

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_{Factors influencing spread of LA in the epidural space}

Injection site - Epidural anesthesia produces a segmental block that spreads in which directions from site of injection?

Caudally & Cranially

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_{Factors influencing spread of LA in the epidural space}

Caudal spread (or is it caudal injection?!) of LA restricted to which dermatomes?

Sacral and lower lumbar dermatomes

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_{Factors influencing spread of LA in the epidural space}

Under which condition can Caudal spread (or is it caudal injection?!) of LA reach Lower thoracic levels? what’s a possible disadvantage of this approach?

Larger volumes (30ml)

Block is “patchy” and short lived

_{Factors influencing spread of LA in the epidural space}

Which dermatomal levels can be reached with Lumbar site injection/spread?

Midthoracic levels (T4-T6) with 20ml

_{Factors influencing spread of LA in the epidural space}

Lumbar site injection/spread can reach caudally with only what volume of LA?

only 10mL of LA

_{Factors influencing spread of LA in the epidural space}

Thoracic injection/spread

Produces a symmetric segmental block

With mid to upper thoracic injection sites, reduce dose by 30-50% to prevent excessive cephalad spread

Not feasible to produce surgical anesthesia in lower lumbar region with this site

_{Factors influencing spread of LA in the epidural space}

With mid to upper thoracic injection sites, reduce dose by what % ? - why?

30-50%

To prevent excessive cephalad spread

_{Factors influencing spread of LA in the epidural space} Thoracic injection/spread Not feasible to produce surgical anesthesia in which region?

**Lower lumbar region**

_{Factors influencing spread of LA in the epidural space} Drug Volume - Increase the volume, what happens?

...

_{Factors influencing spread of LA in the epidural space} Drug Volume - Suggested volumes of LA per spinal segment spread (how many interspaces you need LA to spread) - Cervical & Thoracic epidural vs Lumbar epidural?

Cervical & Thoracic epidural = 0.7-1.0 ml per segment (~10ml) Lumbar epidural = 1-2 ml per segment (~15-20ml)

_{Epidural Anesthesia} Factors influencing spread of LA in the epidural space

Drug Dose Drug concentration Patient position

_{Epidural Anesthesia} Factors influencing duration

**Local anesthetic drug (principle determinant of duration)** ^{Common LA used (Table 56-6)} ^{Shortest duration: chloroprocaine} ^{Intermediate duration: lidocaine, mepivacaine} ^{Longest duration: bupivacaine, ropivacaine, etidocaine} ^{LA’s exhibit different effects of intensity and duration of sensory and motor block} ^{Etidocaine : most intense motor block vs. sensory} ^{Bupivacaine: more intense sensory block vs. motor} **Dose (concentration)** ^{Increasing dose = increased duration and intensity} **Addition of epinephrine, sodium bicarbonate**

_{Factors influencing duration - Local anesthetic drugs} Common LA used

(Table 56-6)

_{Factors influencing duration - Local anesthetic drugs} Shortest duration:

**Chloroprocaine**

_{Factors influencing duration - Local anesthetic drugs} Intermediate duration:

**Lidocaine, Mepivacaine**

_{Factors influencing duration - Local anesthetic drugs} Longest duration:

Bupivacaine - Ropivacaine - Etidocaine

_{Factors influencing duration - Local anesthetic drugs} LA’s exhibit different effects of intensity and duration of sensory and motor block - most intense motor block vs. sensory

**Etidocaine**

_{Factors influencing duration - Local anesthetic drugs} LA’s exhibit different effects of intensity and duration of sensory and motor block - more intense sensory block vs. motor

**Bupivacaine**

_{Epidural Anesthesia} Effect of adding opioids

Provides intense visceral analgesia without affecting motor or sympathetic function Associated with Side effects

_{Epidural Anesthesia} Common opioids drugs added to epidural anesthesia with dose, time of onset and DOA

**Fentanyl** ^{[50-100 mcg]} ^{(rapid onset 5 min, DOA 2-4 hrs)} **Duramorph (PF Morphine)** ^{[2-5 mg]} ^{(slow onset .5- 1 hr, DOA 6-24 hrs)} **Sufentanil** ^{[20-30 mcg]} ^{(rapid onset 5 min, DOA 2-4 hrs)}

_{Epidural Anesthesia} Cardiovascular Physiology

Similar to Spinal Anesthesia With less magnitude

_{Epidural Anesthesia} Treating hypotension:

IVF administration Ephedrine 5-10 mg IV bolus Phenylephrine 50-100 mcg IV bolus

_{Epidural Anesthesia (EA)} Problem Solving During Placement of Epidural

Pain upon insertion Malpositioned epidural needle ^{CSF flow} ^Blood Unable to advance epidural needle

_{Epidural Anesthesia (EA)} Signs and Symptoms of Subarachnoid injection

CSF flows from tuohy needle or epidural catheter Hypotension Bradycardia (not Tachycardia) Spinal anesthesia Increasing anxiety Numbness or tingling in arms, hands, fingers Dyspnea Cardiovascular collapse Loss of consciousness Seizure Coma

_{Epidural Anesthesia (EA)} Signs and symptoms of intravascular injection

Hypertension (at first, if dose contains epi) Hypotension Tachycardia (at first, if dose contains epi) Bradycardia - Tinnitus - Dizziness Circumoral numbness - Metallic taste in mouth Increasing anxiety - Numbness or tingling in arms, hands, fingers Dyspnea - Cardiovascular collapse - Loss of consciousness Seizure - Coma - Death

_{Epidural Anesthesia (EA)} Signs and symptoms of High epidural block

...

_{Epidural Anesthesia (EA)} Treatment of High epidural block or Subarachnoid injection

**Call for assistance!!!** **Airway** =\> Intubate **Breathing** =\> Positive pressure ventilation with 100% FIO2 **Circulation** =\> Treat hypotension and bradycardia =\> IV fluids, ephedrine, phenylephrine, epinephrine, norepinephrine, atropine

_{Epidural Anesthesia (EA)} Complications and Treatment - Similar to

Spinal anesthesia (backache, systemic toxicity, total spinal, neurologic injury, spinal hematoma)

_{Epidural Anesthesia (EA) - Complications and Treatment} Complications a/w dura puncture:

**PDPH**

_{Epidural Anesthesia (EA) - Complications and Treatment} Treatment of PDPH

Supine Fluids Analgesics Caffeine Abdominal binder prior to ambulating

_{Epidural Anesthesia (EA) - Complications and Treatment} Epidural blood patch

Forms a clot over meningeal hole, preventing further CSF leak 10 to 20 ml autologous blood aseptically injected into epidural space at or near interspace where meningeal puncture occurred Produces relief in 85-95% of pt within 1-24 hrs Side effects include back pain and radicular pain Prophylactic blood patch is effective in preventing PDPH in patients after accidental dura puncture during attempt at EA