Anesthesiologists use spinal blocks to interrupt pain sensations from the abdomen and legs during gynecologic, urologic, obstetric and some gastrointestinal surgeries. To perform a spinal block, an anesthesiologist injects medications below the spinal column directly into the spinal fluid. A spinal block is different from an epidural block, although both involve injections near the spine. As with all types of anesthesia, a spinal block produces side effects that are usually mild and short-lived.
Malaise
Spinal anesthesia affects the autonomic nerves that control heart rate and blood pressure, as well as the sensory nerves that control pain; light, touch and temperature sensations; and the motor nerves that control movement. In the case of the autonomic nerves, the result is decreased heart rate and blood pressure. The effect on blood pressure is most pronounced below the level of the block, so blood tends to pool in the legs. According to anesthesiologist Wayne Kleinman, M.D., this can often be managed intraoperatively by loading the patient with 1 to 2 liters of intravenous saline, increasing blood volume, and tilting the operating table towards the patient's head, enlisting the help of gravity in returning blood to the heart. After surgery, however, patients often feel weak, lethargic or not quite themselves. This malaise may be accompanied by nausea, particularly when narcotics such as morphine are used either intraoperatively or for post-operative pain control.
Back and Head Pain
As the spinal block starts to taper off over the course of two to six hours, many patients find they have new pain in the back or the head. Back pain usually manifests as mild pain and tenderness originating from the site where the spinal needle was inserted. If the pain gets worse instead of better or is associated with redness or discharge, patients should notify their doctors immediately because these can be signs of infection or other problems. Spinal headache results when the puncture created by the spinal needle fails to close on its own, allowing a persistent leak of small amounts of cerebrospinal fluid. According to the American Society of Regional Anesthesia and Pain Medicine, spinal headache usually presents three to five days post-operatively and is characterized by a positional head and neck pain that resolves when the patient lies flat. In the case of severe headaches, an anesthesiologist can repair the leak by injecting a small amount of the patient's own blood into the space near the original puncture. Most cases of back pain and headache resolve on their own.
Problems With Urination
In the first few hours after a spinal block, many people experience the urgent need to urinate, but find they are unable to do so. A straight catheter, while uncomfortable, provides immediate relief and prevents complications such as bladder rupture. Young, healthy people typically reacquire the ability to void over the course of a day. In rare cases, says the American Society of Anesthesiologists, it may take several days to reacquire bladder function. Older people and people who had difficulty urinating prior to surgery, such as those with prostate problems, are particularly susceptible to this side effect. Management involves placement of an indwelling catheter--such as a Foley--prior to discharge, followed by a follow-up appointment in a few days to remove the catheter. While short-term maintenance of an indwelling catheter requires little instruction, it does increase the risk of urinary tract infections, so a doctor will usually give patients several chances to void on their own before placing the device.
References
- "Clinical Anesthesiology, 4th Edition"; G. E. Morgan et al. (editors); 2005
- American Society of Regional Anesthesia and Pain Medicine: Patient Information
- American Society of Anesthesiologists: Frequently Asked Questions
- MedlinePlus: Spinal and Epidural Anesthesia
