Pain Management in The Intensive Care Unit

1 Do critically ill patients require analgesia?

Intensive care unit (ICU) patients experience pain from underlying medical disease, immobility, surgery, and trauma. Insertion and maintenance of monitoring and therapeutic devices (venous and arterial catheters, chest tubes, drains, and endotracheal tubes) and routine bedside care (dressing changes, mobilization, physical therapy, and airway suctioning) may also cause pain and discomfort in ICU patients.

2 Is pain relief generally adequate in ICU patients?

The degree of analgesia in critically ill patients is often inadequate. Level of pain is harder to assess in ICU patients because patients are often confused, unable to communicate, or even paralyzed. Inadequate use of analgesic agents, together with routine use of sedatives, may result in oversedation and even delirium, and impaired ability of the patient to cooperate with pain assessment and management.

3 How can pain be assessed in critically ill patients?

Pain should be assessed and documented at regular intervals. Pain is a subjective experience and is most reliably measured by using a subjective scale such as the numeric rating scale (Fig. 72-1), which can be employed in patients as young as 5 years. Younger patients’ pain is assessed by using the faces scale (Fig. 72-1), which is a modified visual analog scale. In patients unable to communicate, reliance on objective measures (physiologic or behavioral) becomes necessary. Whereas use of physiologic measures (blood pressure, heart rate, tearing, diaphoresis, mydriasis) can cause underreporting and overreporting of pain, use of behavioral measures such as observation of facial expression has been demonstrated to correlate with subjective reporting.

Figure 72-1 Visual analog and numeric rating scales.

4 Is pain harmful?

Through activation of the stress response, pain exacerbates the negative effects of the sympathoadrenal response to critical illness at a multisystem level. Pain can contribute to the development of delirium, which is increasingly recognized as a contributor to poor outcomes and even long-term cognitive dysfunction. Myocardial ischemia is exacerbated through both increased myocardial oxygen demand and decreased supply. Pain after thoracic or upper abdominal surgery induces an acute restrictive respiratory defect (reflex muscle rigidity, splinting, loss of functional residual capacity) exacerbated by a reflex reduction in phrenic nerve activity with decrease in diaphragmatic contractility. The result is impaired cough, atelectasis, and pneumonia. Sympathoadrenal activation prolongs the adynamic ileus that follows abdominal surgery and that is recognized as a contributor to prolongation of hospital stay. Neuroendocrine components of the stress response interact with the cytokine system to cause a catabolic state with muscle wasting and impaired immunity and to promote a hypercoagulable state with the attendant risks of myocardial infarction and venous thrombosis.

5 What are the treatment options for a critically ill patient in pain?

6 What is the role of opioids in the ICU, and how do they act?

Opioids are the mainstay of analgesic therapy in the ICU. Long-standing familiarity has fostered relative safety in their use. They are mainly effective against visceral pain of a static nature but relatively ineffective against somatic and dynamic pain; analgesic efficacy tends to dissipate once movement including out-of-bed mobilization and respiratory therapy maneuvers are instituted.

The term opioid refers to any agent with activity at an opioid receptor. There are at least four discrete opioid receptors in the central and peripheral nervous system; the analgesic effects of opioids are mediated mostly via mu (μ) or kappa (κ) receptors. These are G protein–coupled receptors that mediate inhibition of adenyl cyclase.

7 Which opioids are recommended for routine administration in ICU patients?

Morphine, fentanyl, hydromorphone, and sufentanil are the analgesic agents most commonly used and recommended in the ICU (Table 72-1).

8 How do you decide which opioid to use?

Before an opioid is ordered, the goal of analgesia is determined and a therapeutic plan developed. The patient’s cardiovascular status and subsystem organ function are assessed.