Chapter 50

Mechanically ventilated patients often require sedatives and analgesics, and in some circumstances may even require the addition of neuromuscular blockade. The myriad disease processes causing respiratory failure frequently elicit a sense of respiratory distress in these patients. In addition, therapies such as endotracheal intubation and positive-pressure ventilation bring about discomfort to a significant number of patients in the intensive care unit (ICU), and patients often receive these life support treatments after surgical interventions or medical conditions that themselves carry a burden of pain. Accordingly, most patients receive analgesics and/or sedatives while undergoing mechanical ventilation. Although many drugs are available to carry out the goals of pain control and, if necessary, sedation in the ICU, studies of the use of these agents were initially performed in other settings such as the operating room or procedure suite. However, accumulation of evidence directed at ICU patient outcomes—specifically patients undergoing mechanical ventilation—has increased over recent decades, and awareness of the complex pharmacology of sedatives and analgesics in critical care is now well established. At the same time, heightened awareness of the complications associated with the use of neuromuscular blocking agents has relegated their use to mostly short-term indications, such as general anesthesia in the operating room, with ICU use now reserved for a small population of patients, typically suffering from severe acute respiratory distress syndrome. The drugs used to achieve analgesia and sedation of mechanically ventilated patients are necessarily potent; however, the enduring effects when these drugs are used without discretion has impacted strategies for their administration.

Recognition of the fundamental pathophysiologies of respiratory failure and the interaction of the mechanical ventilator and patient will allow goals of pain control, sedation, and neuromuscular blockade to complement the supportive goals of mechanical ventilation. An individualized strategy can then be executed, recognizing goals unique to each patient. This chapter discusses principles and goals of pain control, sedation, and neuromuscular blockade in mechanically ventilated patients, as well as review the drugs currently available to achieve these goals.

We begin our discussion with the analgesic agents because many patients experience pain to some degree, because inadequate control of pain is unfortunately a memory patients may have after ICU management, and because the ability of the patient to clearly indicate and quantify pain may be significantly impaired by respiratory failure and the devices employed to treat it. This last fact can lead to the unfortunate circumstance of pain in the mechanically ventilated patient presenting as agitation, which, if treated with sedatives alone, is often inadequately managed and leads to excessive drug administration.

### Indications

The indications for analgesia during mechanical ventilation come directly from the multiple reasons for pain in these patients. Pain from surgical incisions or trauma is self-evident, but other indications for pain control are subtler. These include endotracheal suctioning or placement of invasive catheters such as arterial or venous lines. Preexisting problems such as skeletal fractures from metastatic cancer and prolonged ...

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