Central Neural Blockade

Hasan Arafat5rd Year Medicine Student

An Najah National University

RELATED ANATOMYVertebral Column, Spinal Cord and Spinal Roots

EPIDURAL ANESTHESIA

Definition

• The injection of a local anesthetic into the extradural (epidural) space

• The space extends from the craniocervical junction at C1 to the sacrococcygeal membrane just above the lower border of S2

• Virtually, it’s safe to inject an anesthetic at any level– Thoracic area -> abdomen– Lumbar-> pelvis and lower limb

Technique

• The epidural space is located using the “loss of resistance” method

• The needle is inserted through skin and advanced horizontally until the spinal ligaments (resistant, hard area) are entered

Touhy Needle

Technique (Cont’d)

• The needle tip is removed and an air/saline filled syringe is attached

• If the tip of the needle is in the spinal ligament, it would be difficult to inject into it

• The needle is advanced slowly while pressing and injecting

• As the needle traverses the ligamentum flavum, resistance drops, marking entry into the epidural space

Notes

• A single injection of anesthetic is enough for short procedures

• In longer operations, a catheter is inserted to provide continuous anesthesia and analgesia

Drugs Used in Epidural Anestheisa

• Lidocaine• Concentration: 1.5-2% soln.• Dose: 15-30 mL• Onset: 10-15 min.• Duration: 1.5 hours

• Bupivacaine• Concentration: 0.5% soln.• Dose: 15-25 mL• Onset: 15-20 min.• Duration: 3-5 hours

Note: Epinephrine can be used with both drugs †

Indications

• Surgical procedures in the abdomen, pelvis or lower limb

• Relief of acute pain (labor, post-op pain). A LA or opioids can be used

• Relief of chronic pain (sciatica, CA)• Relief of post-dural puncture headache using

an epidural blood patch

Contraindications

Absolute• Patient refusal• Full anticoagulation or

coagulopathy• Sepsis (systemic/local)• Uncorrectable hypovolemia• Severe fixed cardiac output

state (severe aortic stenosis)• Allergy to LA• Absence of resuscitation

equipment

Relative• Neurological disease in the

lower limbs• Vertebral column deformity• Cardiac disease• Elevated ICP

Complications

• High risk of LA toxicity• Total spinal shock• Post-dural puncture headache• Systemic toxicity• Backache• Broken Catheter

SPINAL ANESTHESIA

Definition

• Injection of a local anesthetic in the subarachnoid space

• Puncture for spinal anesthesia is done below the level of L2 and above S1 †

Drugs Used in Spinal Anesthesia

• Lidocaine 2% and Bupivacaine 0.5% †• Add dextrose ‡• Epinephrine can be added

Operation Site Concentration

Perineum 1-1.5 mL

Lower limbs 2-2.5 mL

Lower abdomen 2.5-3 mL

Above the umbilicus 3-4 mL

Physiological Effects of Spinal Anesthesia

• Nerve Fibers: finer nerves are blocked in the following order:

Autonomic-> temperature -> pain -> touch -> deep pressure -> somatic motor fibers Recovery: reversed

• CVS: – hypotension

Sympathetic blockade -> venous and arterial vasodilation -> pooling of blood in lower limbs -> reduced venous return -> reduced cardiac output -> hypotension

Hypotension sympathetic Blockade∝– BradycardiaUnopposed vagal tone †, Frank-Starling law ‡, hypotension

Physiological Effects of Spinal Anesthesia

• Respiratory effects:• Inspiratory muscles are barely affected †• No effect on pulmonary function or gas exchange• Respiratory arrest: high levels of drug leading to brain

ischemia due to hypotension

• GIT • Increased secretions• Relaxation of sphincters• Hyperperistalsis can cause N/V• Mucosal damage‡

Physiological Effects of Spinal Anesthesia

• Renal Effect• Non-significant, minimal reduction in renal blood flow

and urinary retention

• Reduction of Stress Response to Surgery• Reduced catecholamines, anti-diuretics and

hyperglycemic response

Factors Increasing the Level of Spinal Block

• Dosage• Increased intra-abdominal pressure and

pregnancy |• Site and rate of administration †• Position (lateral, head down) and coughing• Barbotage• Baricity ‡

Indications & Contraindications

• Same as those for epidural• Except that it’s not used for the relief of

chronic pain or post-dural puncture headache

Complications of Spinal Anesthesia

Intra-operative• Failure• Broken needle• N/V• Bradycardia• Hypotension• Cardiac arrest• Total Spinal• Hypothermia

Post-operative• PDPH• Backache• CN VI palsy• Urinary Retention• Meningitis• Neurological sequalae• Spinal hematoma

RELATED CONDITIONSTSA, PDPH and CES

TSA

• Cause: spread of the LA to the cervical area and brain stem

• S/Sx: profound hypotension, bradycardia, N/V, LOC, dilated pupils, apnea

• Rx: – EARLY RECOGNITION!– IV colloids and vassopressors– Intubation and mechanical ventilationNote: the patient is still awake, so sedate.

PDPH

• Cause: decreased CSF pressure secondary to leak, leading to traction on the meninges and CN’s

• S/Sx: intense headache (frontal/occipital) and neck pain worse in upright position, diplopia and blurred vision.

• Usually 24-72 hours post puncture• Higher incident in women, less in elderly and

when smaller needles are used

PDPH, Rx

Preventive• Using smaller needles• Inserting the needle bevel

parallel to fibers• Maintain adequate

hydration

Curative• In 80%, no treatment is

needed• Keep the patient flat in bed

and give analgesics• Epidural blood patch• Epidural fibrin glue from the

meninges

CES

• Cause: trauma from puncture, spinal or epidural hematoma, abscess or ischemia

• S/Sx: refer to your neurology text• Rx:– EARLY RECOGNITION!– Decompression of hematoma (elimination of the cause)

• Complications: chronic adhesive arachnoiditisNote: the syndrome, as well as its complications are

extremely rare

Read About These

• Differences between spinal and epidural anesthesia

• Combined spinal-epidural anesthesia• Difference between epidural anesthesia and

analgesia

References

• Anesthesia for Medical Students, 1st edition• Clinical Anesthesia Lecture Notes, 4th edition• Toronto Notes 2016, 32nd edition• Netter’s Clinical Anatomy, 3rd edition• Nucleus Medical Media Channel, YouTube