What are the advantages and disadvantages to performing a conduction anesthetic in the ambula-tory patient?
Employing regional anesthesia in the ambulatory sur-gery patient has a number of potential advantages. If little or no intraoperative sedation is required, little or none of the “hangover” effect will be present throughout the postoperative period. Patients who express fear about los-ing consciousness or the loss of control associated with a general anesthetic may prefer a regional technique. Some patients have a strong desire to remain awake to view arthroscopic surgery as it is being performed.
Spinal or epidural anesthesia, however, has potential dis-advantages. There had been concern regarding the apparent increased incidence of PDPH in patients who ambulate postoperatively. However, experience has shown that the incidence of PDPH is equal among patients who are nonam-bulatory and ambulatory, but that the onset may be delayed in patients who remain recumbent for a longer period of time. If spinal anesthesia is chosen, the use of conventional smaller gauge needles as well as newer designs (Greene, Sprotte, Whitacre) that include modifications at the tip to be less traumatic appear to markedly reduce the incidence of PDPH. The theory behind the pencil-point Greene, the con-ical Sprotte, or side port Whitacre needles is that splitting rather than cutting of the dural fibers occurs, which may reduce the amount of cerebrospinal fluid (CSF) leak.
Reduction of the incidence of PDPH to approximately 1–2% or less would be an ideal goal. Technical failure rates of the various needles must also be figured into the overall equation.
Patients must always be informed regarding the potential for development of a PDPH because ambulatory patients usually expect to resume their normal activities shortly after surgery. Additional recommendations to reduce the incidence of headache include keeping the bevel edge of the conventional needle parallel to the longitudinal axis of the body and the dural fibers and avoiding multiple attempts at subarachnoid needle placement. Maintenance of adequate hydration intraoperatively and postoperatively and avoid-ing straining and lifting postoperatively are recommended.
Patients presenting with a persistent PDPH may require an epidural blood patch for relief. Therefore, it is especially important to follow up patients with a telephone call at 24–48 hours after surgery to inquire about the presence of any problems. Conservative treatment of a PDPH in the ambulatory patient includes traditional analgesics, fluids, and bed rest. Performance of an epidural blood patch should be considered early if the headache is perceived by the patient to be extraordinarily severe or incapacitating, or if the patient must return to work immediately, or care for children.
In an attempt to avoid the possibility of a PDPH in younger patients, an epidural anesthetic may be offered to patients if a regional technique is requested or medically indicated. Though an epidural requires greater technical expertise and may be slightly more time-consuming to perform when compared with a spinal, the insertion of a catheter allows additional incremental doses of anesthetic to be added if surgical time is unexpectedly lengthened. Additionally, the use of shorter-acting local anesthetics allows for timing the block to wear off shortly after the procedure is completed. However, the incidence of headache after unintended dural puncture with larger gauge epidural needles is significantly higher. It is interesting that the reported incidence of headache following a general anesthetic in ambulatory patients exceeds the incidence of headache after regional anesthesia, although it is usually much less incapacitating and is self-limiting. It is postulated that the cause of the headache is intraoperative and postoperative starvation and an element of dehydration.
Spinal anesthesia provided by tetracaine and bupivacaine has been associated with recovery room stays as long as 6–8 hours. This must be considered before performing a regional anesthetic, especially if the procedure is to be done later in the day. Another potential disadvantage of administering a spinal anesthetic in an ambulatory patient is the potential for persistence of autonomic blockade for 1–2 hours following restoration of motor function. This can result in the inability to urinate and the need for bladder catheterization. It appears that increasing duration of sympa-thetic blockade correlates with an increased incidence of urinary retention.