This Spinal Anesthesia course will teach you the steps of spinal anesthesia. View the full course for free here: [ Ссылка ]

SURGICAL OBJECTIVES
Spinal anesthesia is a type of neuraxial anesthesia that is able to provide effective anesthesia and analgesia for a large number of indications. It involves placement of local anesthetic into the subarachnoid space — at the level of the mid-to-low lumbar spine — to anesthetize the nerve roots exiting the cord at or below that level. It is commonly used for surgical procedures involving the lower abdomen, pelvis, perineum and lower extremities. It is also used in spinal surgery. When used in isolation, in combination with epidural anesthesia, or in combination with general anesthesia, spinal anesthesia can reduce postsurgical patient morbidity.

Complicating factors:
Accurate injection into the subarachnoid space is essential to provide the desired level of anesthesia and to avoid damage to surrounding structures. Spinal cord trauma is more likely if using higher-level interspaces, especially in obese patients. Previous spinal surgery may make dural puncture difficult and the spread of anesthetic may be restricted by scar tissue. The distortion of landmarks used in the procedure, such as through previous spinal trauma, can also complicate spinal injection.

Contraindications:
Absolute contraindications to subarachnoid injection are an elevated intracranial pressure (ICP), such as due to an intracranial mass or bleed; infection at the site of needle introduction (which may cause meningitis); patient allergy to any of the drugs used, and severe, uncorrected hypovolemia. The hypotension commonly caused by spinal anesthesia — due to a decrease in systemic vascular resistance (SVR) (from a reduction in sympathetic tone) and/or a reduction in cardiac output (CO) — is greatly exacerbated in hypovolemic states. This can cause cardiorespiratory compromise and cardiac arrest. Spinal anesthesia is also contraindicated when the operation is expected to take longer than the duration of the block or result in blood loss such that the development of severe hypovolemia is likely. Relative contraindications to spinal anesthesia are preexisting neurological disease (such as multiple sclerosis), dehydration or hypovolemia (which should be corrected), hypotension (such as seen in severe sepsis), and thrombocytopenia or coagulopathy (due to the risk of hematoma). Patients with fixed cardiac output states, such as in severe mitral and aortic stenosis, should also be approached with caution as they may be unable to compensate for changes in heart rate or vascular capacitance.

APPROACHES
A midline approach is by far the most common and allows the easiest access to the subarachnoid space. A paramedian approach (typically 1 cm either side of the midline) can be used in patients with very narrow vertebral interspaces or who have difficulties with spinal flexion. For extremely difficult cases, the Taylor approach can be used: the needle is inserted 1 cm medial and caudal to the posterior superior iliac spine (PSIS) and advanced cephalad at 55 degrees with medial orientation. This approach is much more difficult but is independent of spinal flexion.

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