Nerve blocks in the critical care environment

The critical care patient population has much to gain from properly administered neural blockade. Effective analgesia alone may make the difference between a patient who is able to compensate for their acute insult and one who cannot. A good example is the patient with multiple fractured ribs, who, after intercostal nerve blocks, no longer requires intubation and mechanical ventilation. The authors believe that effective analgesia is just the beginning of the beneficial effects of neural blockade, because blockade of the afferent limb of sympathetic and sensory nerves may circumvent the neuroendocrine response to acute injury. There is evidence that the stress response is not beneficial in the hospital setting and in fact may be detrimental. Some of the effects include elevated plasma catecholamines, ADH, cortisol, and blood glucose, which contribute to tachycardia, hypertension, increased myocardial work and oxygen consumption, salt and water retention, and a catabolic state with negative nitrogen balance. Whether these changes result in reduced morbidity and mortality has been the subject of several studies, but more studies are needed. It would seem that critically ill patients with little physiologic reserve might be the best population to study because even a small improvement may improve survival. A small beneficial effect in healthy postoperative patients may not be clinically apparent. Most would agree that neural blockade used intraoperatively result in reduced blood loss and a lower incidence of postoperative thromboembolism. The continuation of these techniques into the postoperative period may reduce morbidity and mortality in high-risk patients. A word of caution is in order. The indiscriminate application of the techniques described in this article to critically ill patients would not be in the patients best interest. Nerve blocks are only safe in the hands of those physicians specifically trained to perform them. In addition, local anesthetics have a low therapeutic ratio, and their administration requires continual observation. The use of epidural or intrathecal opioids alone or in combination with other agents also has potentially serious side effects, and requires continual patient monitoring. The proper performance and maintenance of these techniques requires a large commitment of time, manpower, equipment, and a multidisciplinary approach to include physicians, nursing, and support staff. Nerve blocks and other sophisticated techniques started in the operating room or critical care unit should not necessarily be discontinued when the patient is transferred to a ward bed because the full benefit of this therapy may not have been fully realized. There should be a mechanism for turning care over to an acute pain management team who will then coordinate therapy and monitor for side effects. The optimal duration of therapy is unknown and requires further study. As we learn more about pain transmission and modulation in the spinal cord, specific therapy may be devised with fewer side effects than those used today. In addition to epidural combinations of local anesthetics and opioids, alpha-2-adrenergic agonists have been used with some success, and ketamine and others have been tried. Systemic NSAIDs have been useful in treating somatic pain and decreasing opioid dose. In summary, the proper use of neural blockade in the critical care unit holds promise for patient comfort as well as decreased morbidity and mortality. To be effective and safe, however, there must be an institutional and personal commitment of considerable resources and time. With careful patient selection, performance of blocks, and proper monitoring by trained personnel, many patients will benefit and the experience gained will guide future therapy.