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This chapter includes commonly encountered pain issues, including assessment of pain in children, management of perioperative pain including in opioid-tolerant cases, use of ketamine as an analgesic and the basics of chronic pain assessment. Analgesic ladders are included in Chapter 32. Together these sections aim to refresh your pain assessment and management skills.
Paediatric pain assessment tools
You are required to assess a 2-year-old child 1 hour after a paraumbilical hernia repair as the nurses are concerned that they are in pain.
Which of the following pain assessment tools would be the most appropriate?
a) Autonomic responses to pain
b) The FLACC (face, legs, activity, cry, consolability) pain scale
c) The Wong–Baker faces pain rating scale
d) A visual analogue scale
e) The child’s own report
Answer: b)
Studies have demonstrated that pain is under-assessed and poorly documented in children and this can result in poor pain management. There are three approaches to pain assessment in children:
1. Self-reporting
2. Observational/behavioural
3. Physiological.
The most appropriate approach will depend upon the age of the child and whenever possible, self-reporting should be regarded as the most reliable assessment. However, in the case of young children, this is not possible. It is therefore necessary to look for physiological, behavioural and/or observational clues, and there are many pain scales available for children within each of these categories.
The appropriate age ranges for the scales overlap. In general, a child below 2 years old is unable to rate pain intensity, and the FLACC scale is most appropriate. This scale involves a score of 0, 1 or 2 for each element, based on observation. The maximum score is therefore 10, with zero indicating absence of pain. The FLACC scale has been validated up to the age of 18 years.
The Wong–Baker faces scale is valid for 4- to 12-year-olds. It involves the child choosing from five face diagrams with varying expressions to describe the pain. Visual analogue and numerical scales are useful over the age of 8 years.
The COMFORT scale is frequently used for infants through to adults in the critical care setting. It encompasses scores for alertness, calmness/agitation, respiratory response, physical movement, blood pressure, heart rate, muscle tone and facial tension. Other pain scales in use include Pieces of Hurt (3–8 years) and the Multiple Size Poker Chip Tool (MSPCT: 4–6 years).
The use of physiological approaches alone has been shown to be unreliable and should not be used.
Further reading
Management of acute post-operative pain
A 50-year-old woman is in recovery following bilateral mastectomy. She has a history of type 2 diabetes, obstructive sleep apnoea requiring overnight continuous positive airway pressure (CPAP) and CKD (chronic kidney disease) stage 3. Previously she has had post-operative vomiting due to opioids. She has received 1 g paracetamol, 50 mg tramadol and 10 mg morphine. Her pain score is 8/10.
Which of the following would be most suitable for managing her pain and why?
a) Further boluses of intravenous morphine, up to 30 mg until comfortable and then morphine PCA with 1.5 mg boluses and 5-minute lockout period
b) Further bolus of 10 mg intramuscular morphine now with as-required or oral morphine 5–10 mg every 4 hours
c) Further 200 mg intravenous tramadol now, and then morphine PCA with 1 mg boluses and 5-minute lockout period
d) Boluses of intravenous oxycodone, up to 10 mg now until comfortable, and then oxycodone PCA with 1 mg boluses and 5-minute lockout period
e) Boluses of intravenous fentanyl up to 100 mcg now, and then fentanyl PCA with 20 mcg boluses and 5-minute lockout period
Answer: e)
This lady is at risk of post-operative respiratory failure, which could be worsened by excessive opioid administration. She is also at risk of nausea and vomiting. Fentanyl is a good choice as it is short-acting and considered to be the safest opioid for use in renal impairment. Oxycodone may have a better side-effect profile than morphine but should be used with caution in patients with renal impairment.
Opioids are frequently used in large doses for acute post-operative pain. The side effects of opioids must be considered carefully, and often it is a balance between two or three conflicting problems.
Obese patients are often more challenging to manage. Higher doses are required, but the weight used for any calculations is as yet undefined and will vary greatly between patients. In addition these patients are more at risk of obstructive sleep apnoea, and consequently the sedative effects of opioids are more profound. In general it is better to use opioids with shorter half-lives. Fentanyl is a good choice, although the short half-life is due to distribution, meaning that as compartments become saturated the pharmacokinetics alter greatly. Morphine has a longer half-life and is even more unpredictable when administered intramuscularly or subcutaneously. Post-operative nausea and vomiting is problematic and will increase pain and reduce mobility.
Opioids are associated with nausea and vomiting through a variety of mechanisms. There is some evidence to suggest that the emetic side effects of oxycodone are less than those of morphine, although most studies have been performed in patients receiving opioids for chronic cancer pain.
The use of morphine must be carefully considered in patients with renal disease. This patient will have a risk of post-operative acute kidney injury in addition to the chronic disease. Morphine-6-glucuronide is a metabolite of morphine and is 13 times more potent. Like morphine, it is renally excreted, and will therefore accumulate quickly in patients with renal failure. For this reason fentanyl is the analgesic of choice.
Further reading
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