According to the American Society of Regional Anesthesia and Pain Medicine, spinal block is an anesthetic technique involving the insertion of a needle, sometimes attached to a plastic catheter, into the subarachnoid space surrounding the spinal cord. For most patients, spinal block is associated with a reduced risk of death and disability compared to general anesthesia. Compared to epidural anesthesia, which utilizes the same procedure to penetrate the dural rather than the subarachnoid space, spinal anesthesia works faster, requires less medication and offers more complete control over sensory and motor responses.
Pain Control
According to anesthesiogist Wayne Kleinman, M.D., in the 2006 edition of "Clinical Anesthesiology," the spinal block has emerged as the anesthetic of choice for cesarean deliveries, as well as some urologic and orthopedic procedures. Spinal blocks use anesthetics, drugs that block transmission of pain signals, and sometimes analgesics, narcotic drugs that send pleasure signals intended to cancel out pain signals. Nerve fibers that carry information about pain, temperature and fine touch are the most susceptible to anesthetic agents. Fibers that control movements and sense pressure are the last to go. Thus, by varying the dose, an anesthesiologist can modulate the depth of anesthesia---an important benefit in procedures where the surgeon needs to assess response to the repair.
Sympathetic Nervous System Blockade
In addition to controlling pain signals, spinal block also stops signals from sympathetic nervous system, sometimes called the adrenergic nervous system. For most people, the result is decreased tone in the blood vessels of the extremities and decreased blood return to the heart. According to anesthesiologist John S. McDonald, M.D., expanding the patient's blood volume with one to two liters of saline solution prior to inducing the block and tilting the operating table slightly towards the patient's head is sufficient to prevent complications in most patients. However, some patients may still require adrenaline-related drugs in order to maintain blood pressure and heart rate.
Back Pain
As spinal block wears off over the course of four to six hours, some patients experience back pain, either at the injection site or on the neck. Neck pain accompanied by headache occurs in 1 to 2 percent of spinal block patients, says Kleinman. These so-called puncture headaches are attributed to slow leaks of cerebral-spinal fluid into the dural space. A blood patch--injection of a small amount of the patient's own blood into the dural space--provides immediate relief for patients. Other patients may experience mild to moderate pain at the injection site. Back pain accompanied by signs of infection, that does not improve over the course of a day or two or that actually seems to get worse requires additional evaluation to rule out complications of spinal block, such as abscess and hematoma.
References
- "Clinical Anesthesiology, 4th edition;" G.E. Morgan et al. (eds); 2006
- "Williams' Obstetrics, 23rd edition;" F.G. Cunningham et al. (eds.); 2010
- American Society for Regional Anesthesia and Pain Medicine: Regional Anesthesia for Surgery
