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Anaesthesia

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Local Anesthesia & Central Neuraxial Blockade

Question
54 out of 132
 

Spinal anaesthesia is usually given at: (LQ)



A L1 – L2
B L2 – L4

C L5
D L5 – S1

Ans. B

L2 – L4

Spinal anesthesia is usually performed at the level of the L3 or L4 vertebrae in the adult patient, because the spinal needle is introduced below the level at which the spinal cord ends.

Spinal Anesthesia

A. ANATOMY

Spinal anesthetics have their effects at the spinal cord, which originates at the foramen magnum of the skull and the brainstem and extends caudally to the conus medullaris. The distal termination varies from about the level of the 3rd lumbar vertebrae (L3) in infants to the lower border of L1 in adults.

The spinal cord is surrounded by three membranes (from central to peripheral): the pia mater, arachnoid mater, and dura mater. It is believed that the arachnoid mater is responsible for up to 90% of the resistance to drug migration in and out of the CSF.

Inside the subarachnoid space are the CSF, spinal nerves, a network of trabeculae between the two membranes, and blood vessels supplying the spinal cord. Although the spinal cord ends at about L1 in adults, the subarachnoid space continues to about the second sacral vertebrae (S2).

Posterior to the epidural space is the ligamentum flavum, which extends from the foramen magnum to the sacral hiatus. Immediately posterior to the ligamentum flavum are the lamina and spinous processes of the vertebral bodies or the interspinous ligaments. Posterior to these structures is the supraspinous ligament, which joins the vertebral spines.

Anatomic landmarks most important to performance of spinal anesthesia are the iliac crests, the midline of the back, and the vertebral spinous processes. Palpation of the midline of the back identifies the spinous processes and vertebral interspaces in most patients but may be difficult in obese patients.

A line drawn between the upper borders of the iliac crests across the midline of the back identifies the approximate level of L4 or the L4-L5 interspace.

Spinal anesthesia is usually performed at the level of the L3 or L4 vertebrae in the adult patient, because the spinal needle is introduced below the level at which the spinal cord ends.

B. INDICATIONS

Operations below the umbilicus, such as hernia repairs, gynecologic or urologic procedures, and any lower extremity surgeries

Patients with congestive heart failure, except those with stenotic valvular heart disease or hypertrophic cardiomyopathy

Cesarean section

C. CONTRAINDICATIONS

Absolute Contraindications

Patient refusal or inability to cooperate and remain still

Coagulation defects, including intraoperative anticoagulation

Infection at the injection site

Other Contraindications

Sepsis

Neurologic disease, particularly involving the spinal cord, such as myelitis

Intracranial hypertension

Severe spinal or spinal cord deformity

Spinal cord tumor

Stenotic heart valve lesions

Severe hypertrophic cardiomyopathy

Lack of anesthesiologist experience

EQUIPMENT

Patient monitors: ECG, pulse oximeter, blood pressure cuff

Resuscitation equipment, including oxygen, bag and mask, and suction

Sterile gloves and mask: Some institutions may require sterile gown.

Patient must have intravenous access for intravenous fluid and medication delivery.

Sterile prep equipment: Betadine or non-iodine (for patients with iodine allergy) scrub

Spinal needle of small gauge (24-26 gauge)

Sterile drape with fenestration or sterile towel drapes

Local anesthetic for infiltration of the skin and subcutaneous tissues

Small (3-5 mL) syringe for local anesthetic for skin infiltration with small (25 or 30 gauge) needle

3- to 5-mL syringe (usually glass) for spinal anesthetic agent, with markings for 0.2 mL increments on the barrel

Anesthetic for subarachnoid injection

Additives for subarachnoid injection, such as epinephrine, Duramorph, fentanyl

Bandage

Local Anesthesia & Central Neuraxial Blockade Flashcard List

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