Sedation and analgesia I: Principles

The first in a three-part series on the basics of ICU analgesia and sedation.

Many critically ill patients experience pain due to injury, illness, or the care we give them. Many also experience anxiety and distress. Consequently, many patients—although not all—benefit from medications that alleviate these issues. Let’s consider those drugs and when to use them.

Analgesia vs sedation

Analgesics are medications that diminish a patient’s sensation of pain. Sedatives are those that promote relaxation, defray anxiety, and diminish their level of consciousness.

This may seem like an obvious distinction to make, but the two categories are often confused. Why? Probably because many analgesics (such as opiates) also have some sedative effects; likewise, sufficient sedation will blunt the awareness of pain, or at least limit outward signs of it. Despite these blurred lines, however, these are distinct classes of medication, and choosing the wrong type of drug for the patient’s problem will not serve them well.

Patients who have pain need analgesia. Those with anxiety or agitation need sedation. Attempting to treat pain with sedatives will require immense escalations in dose until the patient is deeply comatose—essentially achieving general anesthesia—and even then their bodies may be experiencing pain on a subconscious level. (Notice how anesthesiologists will push opiates during surgery even when the patient is fully anesthetized.) Conversely, trying to treat agitation with pain meds will also require huge doses until you pile on enough of their weak sedative effect to achieve a therapeutic result.

This leads us to the First Rule of Sedation and Analgesia:

Use analgesics to treat pain. Use sedatives to treat agitation. Do not try to mix effects.

Having established that, we can then ask…

How much is enough?

Sensible readers may realize that nothing about being sick necessarily denotes the presence of either pain or agitation. Certainly some patients suffer from these. In the surgical ICU setting, most patients are either post-operative or post-trauma, and they usually need some analgesia. However, they do not necessarily need sedation, and purely medical patients (e.g. suffering from respiratory failure or sepsis) may not need anything at all.

This is a confusing notion for many providers of the modern era, who may be accustomed to ICU patients being drugged into a coma the moment they enter the unit. But in the early days of critical care medicine, even mechanically ventilated patients were more likely to be found sitting awake in a chair than lying unconscious in bed. Somehow along the way, we acquired the trope that everyone sick—and certainly everyone intubated—needs to be deeply snowed. Only in recent years have we begun to turn back that clock.

This movement is driven by the realization that oversedation, while it may make life easier for caregivers, has profound negative effects for patients. It promotes delirium—which is directly associated with mortality—increases time on the ventilator, worsens deconditioning, and generally keeps patients sicker for longer. Progressive systems have therefore returned to the practice of “just enough” sedation, and you might even see their halls darkened by patients ambulating (with ample assistance) while intubated and dragging IVs. Why not?

This leads us to the Second Rule of Analgesia and Sedation. Whenever possible…

Patients should be calm, with pain controlled, but either awake and alert, or sleeping normally.

Notice what this does not say:

  • It does not say that patients should be deeply sedated. During the day, they should have the same level of alertness as you or I. At night, they should enter normal physiological sleep. Being slightly sleepy during the day is fine; being knocked out is not.
  • It does not say that patients should be left in pain. (“No pain” is not always achievable, but pain should be controlled to an acceptable, undistressing level.) Even without trauma or surgery, many ICU patients will nevertheless complain of significant pain, often developing hyperalgesia which can lead to pain even during routine care (such as suctioning and repositioning in bed). This should and must be controlled.
  • It does not say that patients on the ventilator should be treated any differently. Awake and comfortable is still their goal.
  • It does not say that acutely agitated or delirious patients should be left that way. They can still be sedated as needed. However, their desired level of arousal remains the same; it just may be more difficult to achieve.

Getting there

The road to that goal can be informed by our Third Rule of Analgesia and Sedation:

Start by treating pain, then add only whatever sedation is needed.

This has been referred to as “analgosedation,” or an “analgesia first” (“A1”) approach, but it needs no fancy name, because it’s just common sense and proceeds naturally from our prior rules. Why would we do anything else?

The important point is that when pain is present, it needs to be controlled. So does agitation. Yet often agitation is caused by pain, and hence treating the former may obviate the need for the latter. Starting with sedation—that is, going backwards—leads to a violation of the First Rule, resulting in a still-uncomfortable patient who has merely stopped wriggling. Using this approach, many patients will need some analgesia, yet no sedation at all. Some will need sedation alone, but only if it is clear that they are free from pain.

Measuring and titrating

How much drug do you give? You titrate to effect. Fortunately, numerous scales and scores exist.

  • Pain: The ubiquitous 1–10 (or 0–10) scale is acceptable, and may be supplemented with a visual analog scale or the Wong-Baker FACES chart. However, ICU patients are not always able to respond to these questions, especially when they have been over-sedated. Other scales exist that focus on objective criteria, such as the Behavioral Pain Scale (BPS) and the Critical Care Pain Observation Tool (CPOT).
  • Sedation: The Richmond Agitation and Sedation Score (RASS) seems to have emerged as the most common sedation scale, although others exist. It offers simple, objective criteria for measuring the level of arousal. In general, a RASS goal should be from 0 (alert and calm) to -1 (slightly drowsy).

Each ICU should adopt standard scores of this kind and use them consistently. This allows orders for nurse-driven titration of pain and sedation to reach objective targets.


We now understand our three basic principles of sedation and analgesia:

  1. Use analgesics to treat pain. Use sedatives to treat agitation. Do not try to mix effects.
  2. Patients should be calm, with pain controlled, but either awake and alert, or sleeping normally.
  3. Start by treating pain, then add only whatever sedation is needed.

Consistent application of these rules will result in manageable patients with better mobility, less delirium and PTSD, and shorter pathways toward rehabilitation.

Next time: specific agents for analgesia

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