Anesthesia and the neurosurgical patient: Part III--acute spinal cord injury.

In Part III of a continuing series on neuroanesthesia, the author explores the anesthetic considerations for acute spinal cord injuries. Because of the complexity and severity of physiologic disturbances seen in patients who have such injuries, the nurse anesthetist needs an understanding of the type of injury and the surgical procedure to be performed before the proper anesthetic care can be given. The annual incidence of spinal cord injuries involves some 11,200 people. Of that total, 4,200 die before reaching the hospital and another 1,150 die during hospitalization.' About 4,000 traumatic paraplegics are added to the national number each year. However, developments in medical management have steadily decreased mortality since 1942 when the mortality rate was 60% in the first three months after injury. The leading cause of death in cases of spinal cord trauma is respiratory failure. 2 Spinal cord anatomy In reviewing the anatomy of the spinal cord, one can categorize the spinal column into three broad anatomical categories. The first is referred to as the vertebral unit. It includes the bony column as well as the spine's ligaments and muscles. This unit is responsible for the mechanical stability and mobility of the spinal 358 column. The 26 separate vertebral bones (including 7 cervicals, 12 thoracics, 5 lumbars, the sacrum and the coccyx) provide protection for the underlying spinal cord. Strong annulus fibrous discs provide stability of the synarthroses between the vertebral bodies. The ligamentous structures including the interspinous ligaments and ligament of flavum (sometimes referred to as the yellow ligament) provide further stability. The second unit is the cord unit which consists of the spinal cord with its associated nerve roots as well as its membranous coverings and the dura. The spinal cord is an extension of the brain stem, suspended by means of a series of nerve roots and ligaments confined by an inelastic fibrous membrane called the dura. The dura mater ex tends to the level of the second sacral segment where it ends in a blind sac. The spinal cord itself ends between lumbar segment I and 2. The space between the vertebral column and the spinal dura is known as the epidural or extradural space. It contains a network of blood vessels, adipose, and areolar connective tissue. The subdural space is located between the inner surface of the dura and the underlying arachnoid membrane. The innermost layer of the meninges is the pia …