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The debate on the safety, efficacy and benefits of regional anesthesia has endured since the birth and popularization of spinal anesthesia in the late 1800s. As early as 1936, an assessment was published in the literature entitled Routine spinal anesthesia in a provincial hospital: with comparative study of postoperative complications following spinal and general ether anesthesia (NvGaard 36). Over the ensuing decades, there have been multiple trials, observational studies, reviews, meta-analyses and systematic reviews that address the issue. There have been phases in this history when regional anesthesia has been popularized and considered safer and better than general anesthesia, and phases when general anesthesia has been popularized and considered safer and better. More recently, the use of regional anesthesia to supplement general anesthesia has been popularized. Yet the question of whether regional anesthesia has beneficial effects on surgical outcome has never been satisfactorily answered. Today, when advanced equipment, monitors and drugs are available to improve the administration and safety of both regional and general anesthesia, the answer is even more elusive. This paper will argue that the question itself is of such complexity that there can never be a simple answer. It will assess the role and limitations of the literature in assessing anesthetic options, and it will briefly outline the evidence to date on the benefits of regional anesthesia.
The complexity of the question The reason that we cannot provide a simple answer to the question: Does regional anesthesia improve outcome after surgery? is that the question itself is complex. In fact, even in daily practice, when faced with an individual patient, there is unlikely to be a simple answer. The answer depends on many interdependent factors that cannot possibly be separated. Thus, it depends on the patient, the surgery, the outcomes of interest, other factors that control the outcomes, how the regional anesthesia is being used, and to what it is being compared. The patient. In healthy patients, because adverse outcome is extremely rare, there is unlikely to be a difference in outcome between regional anesthesia (RA) and general anesthesia (GA). On the other hand, in patients with lung disease, and those undergoing thoracic and upper abdominal procedures, postoperative epidural analgesia has been shown to be beneficial in terms of reducing pulmonary complications. In patients with heart disease, because regional anesthesia can reduce pain and stress, reduce cardiac work, improve pulmonary function and oxygenation and improve mobility, RA may be beneficial. In pregnant women the risk of GA is exceptionally high, thus RA is generally preferable. Thus, selected patients are likely to derive benefit from regional anesthesia; other patients are unlikely to be affected. The surgery. Since RA alone is only suitable for extremity, head and neck and body surface surgery, the comparison between RA and GA can only be made for this limited range of surgeries. The question is narrowed to: do patients undergoing extremity or body surface surgery do better postoperatively following regional or general anesthesia? Combining GA with RA broadens the scope, but begs a different question, namely: do patients undergoing intrathoracic and intraabdominal surgery do better postoperatively if RA is added to GA? Already, we have had to separate surgical populations in order to judge the efficacy of RA, and the original, broader question has become mute. Clinically meaningful attenuation of stress responses is only possible when painful stimulae are effectively blocked by RA (eg spinal for lower extremity surgery). Hence, it may be only in these cases that the benefits arising from the prevention of neural-hormonal-metabolic stress responses and shifting of coagulative and fibrinolytic processes towards normalization are realized. The exceptionally high risk of GA for Cesarean section makes this a procedure for which RA is likely to be particularly beneficial. RA for ambulatory surgery is almost certainly going to be associated with shorter hospital stay because patients can be discharged before the nerve block has worn off, and before pain and nausea begin. Thus, some surgeries lend themselves to the use of RA, and patients undergoing these selected procedures can be predicted to derive clear benefit after surgery if RA is used. Other surgeries do not, and the selection of RA is then made on the basis of other factors in this complex melee. The outcomes and other factors that control the outcomes. Patients, surgeries, and outcomes are interdependent. One cannot reasonably extrapolate from the findings of a study of a certain outcome in a defined or mixed patient population undergoing a specific surgical procedure. For example, while RA patients undergoing lower extremity surgery may experience a lower incidence of deep vein thrombosis (DVT) because of the particular risk of venous stasis after this surgery, there is probably no difference for healthy patients undergoing upper body surgery. Length of hospital stay is reduced in ambulatory patients, but is not reduced in inpatients (other than those undergoing intraabdominal procedures who have a reduced period of ileus when epidurals are used). Reduced mortality has been attributed to the use of RA, but only in vascular patients and in elderly patients having hip repair, probably because of the high risk of thromboembolism associated with these patients and with these procedures. To make these evaluations even more difficult, there may be external factors that control the outcome in question, and negate the beneficial effect of RA. For example, modern coagulation prophylaxis may vitiate the known beneficial effect of RA on thrombosis; or the use of critical pathways may independently reduce delays in hospital discharge caused by prolonged ileus or prolonged immobility. How the regional anesthetic is being used and to what it is being compared. Obviously, a regional anesthetic used as a sole anesthetic is quite different from a regional anesthetic use as an adjunct to GA, and different again from RA used to prolong analgesia in the postoperative phase. Moreover, neuraxial anesthesia carries risks and benefits that do not apply to other regional techniques. In the case of the comparator, not all general anesthetics are the same and therefore studies of RA versus GA may not be comparable. For example, endotracheal anesthesia carries attendant risks of stress during intubation, failed intubation, aspiration, broken teeth and decrease in venous return and cardiac output. This makes it a different comparator to mask anesthesia using a laryngeal mask airway, or total intravenous anesthesia using high dose opiates. These factors confound any analysis of RA versus GA, and since the benefits of RA on surgical outcome are usually assessed by comparing outcomes after RA versus GA, they also confound any analysis of the effect of RA on surgical outcome. In summary, we are faced with a complex set of factors that are so interdependent as to preclude generalizing the effects of RA on surgical outcome.
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