Patient selection and premedication
Is regional anesthesia safer than general anesthesia?
Surgeries most associated with improved outcome after regional anesthesia include:
Airway and regional anesthesia
Regional anesthesia refers to anesthesia of a segment of the body, achieved by selective interruption of nerve transmission (i.e., peripheral or neuraxial) without the need to alter the patient’s level of consciousness. In this manual I discuss several aspects related to regional anesthesia, according to the techniques most commonly used in the United States, although with special emphasis in the techniques we perform daily at Cook County Hospital of Chicago.
Regional anesthesia has been traditionally considered an “art”. As such, it is usually practiced by “artists”, who use their particular talents to produce results difficult to reproduce by anesthesiologists devoid of such artistic talents. We have a great respect and admiration for all the pioneers who introduced and/or helped popularized the various regional anesthesia techniques available to us now. We owe them a debt of gratitude. It is the foundation on which we build our practice today. However, we also believe that the practice of regional anesthesia in the 21st century should be based more on science than art, taking advantage of all the various technologies available to us now. Using objective tools to help our work, does not demean our practice, in the contrary, it makes it more rational, reproducible, and potentially easier and safer. The recent introduction of ultrasound to assist peripheral nerve blocks is an example of that.
The nerve blocks that we perform, and which I describe in these pages, are based on anatomical, physiological, and pharmacological facts. The endpoints chosen are objective. The local anesthetic solutions are used in volumes and concentrations considered adequate and safe by clinical experience. Regional anesthesia practiced in this manner, should likely lead to results that are predictable and reproducible.
Regional anesthesia carries the risks and complications associated with the use of local anesthetics (i.e., local anesthetic toxicity), the risks and complications of using needles and drugs in the proximity of nerves (e.g., neuropraxia, irreversible nerve damage) and those risks associated with a particular technique (e.g., pneumothorax, total spinal).
As with any other anesthetic technique, choosing regional anesthesia requires a thorough assessment that involves the patient, the surgeon, the nature of the procedure and its estimated duration, as well as the level of experience of the anesthesiologist with regional anesthesia and its management.
The type of anesthesia for any procedure must be tailored to every individual patient. There are patients who in general are not good candidates for regional anesthesia, especially if they remain awake (e.g., drug abusers, pediatric patients). On the other hand we have a vast and successful experience with peripheral nerve blocks on drug abusers and some pediatric patients, confirming that each case must be individually evaluated.
Judicious use of sedation increases patient’s cooperation and acceptance. Sedation should be used to calm anxiety, but not to turn the patient unconscious or otherwise unresponsive. This is especially true in blocks performed close to the neuraxis, like interscalene blocks and lumbar plexus blocks. Keeping the patient lightly sedated, but awake and cooperative, makes the procedure easier for both the patient and the anesthesiologist. A conscious and cooperative patient may also potentially decrease the chances of complications (e.g., pain at injection, early subjective symptoms indicating impending systemic toxicity, etc).
Every nerve block, whether it is performed in holding area, OR, PACU or office, must be treated as potentially dangerous. Monitoring blood pressure, heart rate and pulse oxymetry, as well as the establishment of IV access must always be considered. Supplemental oxygen should be given especially when sedation is being used. Resuscitation equipment, including oxygen, ambu bag, airways of different sizes, intubation equipment and tubes, along with appropriate resuscitation drugs and suction capabilities, must always be readily available.
A clear strategy to deal with and treat complications must be in place. It is always advisable, before starting a technique, to leave room at the head of the bed for the anesthesiologist to manage the patient’s airway, should that become necessary. Familiarity with the surroundings helps when dealing with emergencies.
Every discussion on regional anesthesia must address the issue of its relative safety compared to general anesthesia. Despite several studies suggesting it and an intuitive feeling that regional anesthesia seems “safer’ than general anesthesia, no definite and general answer can be given. The inability to give a clear answer comes from insufficient data. Most of the outcome studies available to us, have compared the relative benefits of neuraxial anesthesia (spinal or epidural) versus general anesthesia in intra abdominal surgery. Most of the studies lack the power (number of cases) to be able to see a true difference, if it existed, and most of them are retrospective. Lack of randomization raises the possibility of bias at the time of technique selection (i.e., sicker patients receiving more regional anesthesia).
Other problems have to do with the parameter chosen for comparison. To compare mortality for example, the sample would have to be extremely large in order to find a statistically significant difference, since mortality under any type of anesthesia is extremely low. Other parameters like DVT, myocardial infarction, pneumonia seem more adequate for comparison, but their rates vary according to the procedure and not just type of anesthesia.
The physiological response to the stress of surgery or “surgical stress response” involves release of local and central mediators leading to increased levels of, among others, cathecolamines, cortisol, aldosterone and renin. It is also frequently associated with hypercoagulability, immune response depression and protein wasting. The release of local tissue inflammatory factors like cytokines and interleukins can be partially blocked by non-steroidal anti-inflammatory drugs and peripheral nerve blocks using local anesthetics. The central response, responsible for the release of cathecolamines and cortisol, can only be blocked by neuraxial blocks using local anesthetics. Determination of hormonal markers of stress can be demonstrated after general anesthesia and after certain regional anesthesia techniques. However, its impact on morbidity has not been clearly established. If physiological parameters are measured (e.g., PO2, O2 sat) there is also some evidence that the values obtained are frequently better after regional than general anesthesia. However, the real impact that better postoperative physiological parameters have on morbidity is not clear.
Nonetheless, there seems to be some agreement that regional anesthesia improves the outcome of selective surgical procedures in a number of different ways, including decreased rates of DVT, PE and blood loss.
Mortality rates also have been shown to be significantly lower with epidural anesthesia as compared to general anesthesia.
An interesting meta-analysis on the subject of comparative outcome was published in December 2000 in the British Medical Journal, by Rodgers et al from New Zealand. The authors reviewed the literature looking for randomized trials with or without use of neuraxial anesthesia (spinal or epidural) before 1997. A total of 141 trials including 9,559 patients were included in this meta-analysis. The following are the main findings:
The authors concluded that neuraxial blocks “reduce postoperative mortality and other serious complications”, adding that it was not clear whether these effects were due “solely to benefits of neuraxial blockade or partly to avoidance of general anaesthesia”.
Meta-analysis has the advantage of pooling large numbers, therefore infrequent clinical events can be studied. However, it also means putting together trials from different settings. They not only include data from different institutions, but also in some cases different countries and cultures. It remains to be seen whether these very encouraging results can be duplicated, and whether they could apply more generally to regional anesthesia beyond neuraxial blocks (i.e., peripheral nerve blocks).
Other authors, like Christopher Wu from Johns Hopkins, have shown the benefits of regional over general anesthesia, when non-traditional outcomes are measured. These outcome parameters include patient satisfaction (including analgesia, prevention of nausea and vomiting and discharge readiness), ability to undergo physical rehabilitation, and cost. These so-called “soft” parameters are having increased importance in today’s cost-conscious practice.
For some anesthesiologists managing a difficult airway usually means always securing it. This approach negates the benefits that regional anesthesia can provide when it is judiciously used. Evidence does not exist to support either claim.
We believe, that regional anesthesia, with its capacity to produce safe and dense surgical anesthesia with minimal physiological derangements, should be carefully contemplated, on a case by case basis, in all kind of patients. This does not mean that the anesthesiologist should not be prepared at all times to manage the airway, and have at his/her immediate disposal all necessary equipment and personnel to do it. We do need to remember though, that “securing” the airway in all patients is not completely devoid of risks.
In our practice we routinely provide regional anesthesia to patients with challenging airways. These patients include the obese, as well as trauma patients wearing halos and cervical collars. These patients are assessed individually. The discussion needs to involve the patient and the surgeons and must take into account the anesthesiologist’s expertise and familiarity with regional anesthesia. If a regional anesthesia option is selected, a backup plan, that can be readily implemented, needs to be available at all times.