Is it appropriate to stop giving pain medicine just because the patient is asleep?
My little burned patient was probably not expressing relief from pain with her periods of unresponsiveness – especially since she had not received anything for her severe pain. Each time that she woke up screaming, that was also a clue. the medical command doctor’s orders were to give no pain medicine.
Is propofol effective at putting patients to sleep without relieving their pain?
Sleep does not mean pain relief, but many of us assume that is exactly what it means.
What does this study show?
The main goals of the study were to assess prospectively the temporal relationship between morphine titration, analgesia and sedation and to determine whether patients who sleep during i.v. morphine titration are simply sedated or are actually relieved from their pain.
This study was done in a PACU (Post-Anesthesia Care Unit). This study looks at whether sleep after a painful surgery indicates that the pain is well controlled.
Among morphine‐induced side‐effects, sedation occurs in up to 60% of cases during morphine titration, and represents a common cause of discontinuation of titration for reasons of safety.3 The assumption is usually made that patients sleep when their pain has been relieved. Nevertheless, some patients complain of persistent pain when they awake and morphine titration is frequently resumed.
If the patient wakes up with pain, was the pain always there, or has the pain returned?
In this study, they woke patients from sleep to find out.
Did you fall asleep because your pain is well managed or do you still have significant pain?
Although the optimal dose of morphine is still a matter of debate, the usual recommendations for morphine titration include a short interval between two boluses (5–7 min) and no upper limit for the total administered dose.2 3 
They did not place an upper limit on the total dose, but it did seem to take a long time to manage the pain at just 2 mg to 3 mg at a time.
Boluses of i.v. morphine were 3 or 2 mg when patient’s weight was above or below 60 kg, respectively. The interval between boluses was 5 min, without an upper dose limit. Morphine titration was discontinued when VAS was inferior to 30 mm, in case of side‐effects such as nausea and/or vomiting, respiratory depression (SpO2 <92%, ventilatory frequency rate 3 min, RS >2). An RS on a 6‐point scale was used (1=anxious and agitated patient; 2=cooperative patient; 3=asleep patient, brisk response to loud voice; 4=asleep patient, sluggish response to loud voice; 5=no response to loud voice; score of 6=no response to pain).
A common measure of sedation is the RS (Ramsay Score), but like the GCS (Glasgow Coma Score) this relies heavily on the eye opening of the patient.
When a patient slept while receiving morphine, its administration was discontinued.
They were giving boluses of morphine every 5 minutes. If the patient was not awake, they did not awaken the patient to evaluate the level of pain. For this study, sleeping patients were awoken every 10 minutes to evaluate pain level.
Most of the patients who remained awake had good pain management, although it took a while for about a quarter of them to get relief from pain.
The numbers in the two graphs may not be comparable.
The three measurements in the Awake group are 10 minutes and 20 minutes after initiation of morphine titration and at the end of morphine titration.
The three measurements in the Sleep group are 10 minutes, 20 minutes, and 30 minutes after the onset of sleep.
There were significantly more men and the surgical duration was shorter in the Awake group compared with the Sleep group. In the Sleep group, the mean time to the sleep onset of initiation of morphine titration was 22 (10) min.
The Awake group graph looks at 10 minutes and 20 minutes after initiation of morphine titration, and at the end of titration.
The Sleep group graph looks at about 32 minutes, 42 minutes, and 52 minutes after initiation of morphine titration.
And why did they stop titration with 5% of the Awake patients still experiencing significant pain?
5% is just one of the 21 Awake patients, but they state that they had no upper limit on the morphine administered, so why did they not even get this one patient down to a pain level of 5/10? The comparison with the Awake patients appears to have been well intended, but it does not appear to have contributed anything useful to the results.
The current study suggests that sedation during morphine titration occurs before patients have been completely relieved from their pain (as mean VAS at sleep onset was ∼50 mm), and that sleep encountered during morphine titration is mainly related to the sedative properties of morphine.
That appears to have been well demonstrated.
The second important finding of this study is that among patients in whom morphine titration is discontinued because of sedation, 25% still bear a high level of pain (VAS >50 mm) whereas only 50% have satisfactory pain relief (VAS <30 mm).
We do not expect people to be able to sleep with more than 5/10 pain, but some do.
Sedation is not pain relief, even if the sedation is causing the patient to sleep.
Finally, this study suggests that morphine‐induced sedation should not be considered as an indirect indicator of a correct level of analgesia during i.v. morphine titration.
What I think matters most is that this study provides documentation that about a quarter of the sleeping patients had significant pain (greater than 5/10) when awoken and asked about pain level.
Just because we can sedate a patient to the point of sleep does not mean that the we have relieved the patient’s pain.
Just because we have prevented the patient from moving, by giving a paralytic, does not mean that we have relieved the patient’s pain.
We need to assess the patient’s pain to find out if the patient is experiencing significant pain.
 Is morphine-induced sedation synonymous with analgesia during intravenous morphine titration?
Paqueron X, Lumbroso A, Mergoni P, Aubrun F, Langeron O, Coriat P, Riou B.
Br J Anaesth. 2002 Nov;89(5):697-701.
PMID: 12393765 [PubMed – indexed for MEDLINE]
Paqueron X, Lumbroso A, Mergoni P, Aubrun F, Langeron O, Coriat P, & Riou B (2002). Is morphine-induced sedation synonymous with analgesia during intravenous morphine titration? British journal of anaesthesia, 89 (5), 697-701 PMID: 12393765