Needless pain is a major concern for patients after surgery or trauma. The ethical obligation to relieve suffering is at the core of medical care. RMOs are usually the first members of the medical team to be called for pain problems. By following simple guidelines, you can greatly improve the pain relief of your patients. The aim of this guide is to help treat pain after surgery, trauma, burns or other medical procedures. Its content is based on several evidence based guidelines.
What is Pain?
It is whatever the patient says hurts. You must avoid imposing your own views and expectations on what you think the patient should feel. What you see at the bedside is pain behaviour, that is, how the patient expresses pain. Pain can be measured by asking the patient to rate the severity eg using words or numbers (ie 0 to 10). Use the patient's self-report.
Adverse effects of pain
Unrelieved pain can lead to preventable postoperative morbidity. Pain reduces the ability to deep breath, cough and do chest physiotherapy, which causes respiratory complications. Pain stimulates the sympathetic nervous system causing tachycardia, vasoconstriction and increased myocardial oxygen demand and possibly ischaemia. Pain can also result in hypercoagulability (and DVTs), increased stress response with catabolism and immune impairment.
Drugs for pain relief
Opioids. The opioids (morphine like drugs or narcotics) are the cornerstone of acute pain relief. As well as analgesia they also produce other effects such as sedation, elevated mood, respiratory depression, nausea, vomiting, increased smooth muscle tone, constipation, bradycardia, hypotension (if hypovolaemic). Addiction is very rarely seen (risk 1:5000) when opioids are used for pain relief in normal people. Tolerance and physical dependence occur with longer-term use and are usually not a problem with acute pain relief. There is no evidence that giving opioids interferes with the ability to make a diagnosis.
Morphine is the opioid of first choice. The usual starting doses are - 5 to 15mg Q2h IM or SC, 1 to 3mg Q5min IV, 10 to 30mg Q4h Oral. Doses are highly variable and need to be adjusted for the individual patient and the clinical situation. Always review the effectiveness of what you have prescribed.
Pethidine offers no advantage over morphine (except maybe reduced smooth muscle tone). It is shorter acting and needs to be given more frequently. After large, repeated doses (800 to 1000mg/day) it may lead to accumulation of a toxic metabolite (norpethidine) which causes CNS simulation with irritability, confusion or seizures. This is most likely in patients with renal impairment. It is the drug preferred by opioid abusers. Large IV doses cause hypotension by direct myocardial depression. It is contraindicated in patients taking antidepressants of the monoamine oxidase inhibitor class. The usual doses are - 75 to 100mg Q2h IM, 25mg Q5min IV.
Oxycodone is a synthetic opioid that has high oral bioavailability. It is useful as an oral analgesic that is more effective than Panadeine Forte. The usual dose is - PO 10mg Q4h. Can also be given as a suppository - 60mg Q6h and sustained release tablet (Oxycontin®)
Codeine is given PO or IM. It is a weak opioid that has a ceiling to its effectiveness if more than 60mg is given. It is used for moderate pain. Its analgesic effect is probably due to its conversion to morphine in the liver, which is variable amongst individuals. It is traditionally used after intra-cranial surgery due to its limited effectiveness. Its most commonly used in combination with paracetamol e.g. Panadeine Forte (0.5g paracetamol with codeine 30mg) or Panadeine (with only 8mg codeine that is of doubtful value). Both are given 1-2 tablets Q4h (maximum of 8 tablets per day).
Important principles of opioid use: The recommended doses are only starting doses for normal adults. The effective dose can vary by up to 10 times between individuals. Age rather than weight is a useful guide to dose. Patients must always be reviewed for their response and the dose adjusted accordingly. Generally, if the patient has continuing pain, is not sedated and an adequate time has passed since the last dose (10min for IV and 60 min for IM) then it is safe to give another dose. Note: If pain is not controlled despite an increased dose, then a postoperative complication should be considered.
Table: suggested equi-analgesic doses of opioids
|
Opioid |
Parenteral (IM or SC) |
Oral |
|
Morphine |
10mg |
30mg |
|
Fentanyl |
100µg |
NA |
|
Pethidine |
100mg |
300mg |
|
Oxycodone |
15mg |
20-30mg |
|
Hydromorphone |
1.5mg |
7.5mg |
|
Methadone |
10mg |
20mg |
|
Codeine |
130mg |
200mg |
Traditionally, opioids are prescribed on an as needed basis - called PRN. This is usually ineffective as more than half of patients will still suffer moderate to severe pain. Doses are not given until pain re-occurs and there are delays in obtaining, administering and absorbing each dose. For ongoing and expected pain then it is more rational to prescribe doses on a regular or "around the clock" schedule. A dose can be withheld if the patient is asleep, sedated, has respiratory depression (<10 breaths/min), has no pain or refuses. The risk of significant respiratory depression from opioid use is rare and about 1:1000. Excessive sedation is a more sensitive indicator of opioid excess than a slow respiratory rate.
Management of opioid side effects. While opioids can cause nausea and vomiting, other causes need to be considered also eg effects of surgery and anaesthesia. The usual treatment includes antiemetic agents. Commonly used are the anti-dopaminergic agents such as metoclopramide (10mg IV or IM Q4h PRN) or prochlorperazine (12.5 mg IM Q6h PRN). For most patients these are adequate. Otherwise 5HT3 drugs can be added, such as ondansetron (4mg IV or 4 mg by trans oral wafer Q8h PRN). While ondansetron is moderately more effective than previous agents, it is significantly more expensive. Pruritus can be caused by opioids and treatment depends on the route of opioid administration. For systemic opioids then antihistamines are useful (promethazine 12.5 mg IM Q4h PRN). For spinal opioids, then low dose naloxone (40ug SC Q2h) is used. Constipation will occur with longer term opioid use and must be prevented with regular daily laxatives.
Naloxone is a competitive opioid antagonist. Given IV it promptly reverses the effects of excessive opioid administration. It has a short duration of action and repeated doses may be needed. It must be given with caution as serious adverse effects may occur especially with large doses e.g. severe pain, withdrawal syndrome in opioid dependant patients, hypertension, pulmonary oedema, and cardiac arrhythmias.
Patients with special needs:
Some patients should be flagged for early consultation for effective management. Examples include methadone program patients, those on naltrexone and patients on chronic opioids (eg cancer pain or chronic pain).
Tramadol: This a unique mixed-action drug. Analgesia is produced by a weak opioid action (like codeine), and by nor-adrenergic and serotonin mechanisms. It must not be given with antidepressants as interactions may occur. It has less abuse potential, less respiratory depression and constipation than conventional opioids. The usual dose is 50 to 100 mg Q6h IM or PO.
Non-opioid analgesics. These are the non-steroidal anti-inflammatory drugs (NSAIDs) and related drugs (paracetamol and aspirin). Their effect probably produced by inhibition of the enzyme cyclo-oxygenase with reduced production of prostaglandins from tissue injury. If used alone they are effective for relief of mild to moderate pain. When combined with an opioid, they are useful for relief of severe pain. Here they reduce the opioid dose requirements (~30%) and maybe adverse effects of the opioid.
While the NSAIDs avoid the adverse effects of opioids they do introduce their own adverse effects. Prostaglandins are important for the regulation of many physiological systems. All NSAIDs (except paracetamol) impair platelet aggregation and must not be given where strict haemostasis is vital. Aspirin is unique as it causes prolonged inhibition of platelet aggregation (~ one week). NSAIDs can provoke GIT bleeding and should not be given to patients with an active peptic ulcer. Patients with asthma that is provoked by aspirin must not be given NSAIDs. NSAIDs can impair maintenance of renal blood flow that may result in renal failure. They should not be given with concurrent renal disease, hypovolaemia or hypotension. Ketorolac is the most potent NSAID and is given parenterally. It has increased risk of serious adverse effects and its use is restricted and requires approval from the Acute Pain Service. Recently, selective COX-2 inhibitor NSAIDs are now available, but the contraindications remain and adverse effects appear similar.
Doses. Diclofenac 100mg BD PR or 50mg tds PO, Indomethacin: 25 mg Q6h PO or 100mg BD PR. Naproxen: 500mg BD PO (also as suspension), Ketorolac 10mg Q6h IM (restricted)
The Acute Pain Service
The hospital has a formal acute pain service that provides specialised and invasive methods of pain relief to patients after surgery, trauma or burns. It is operated by the department of Anaesthesia, as part of the Multidisciplinary Pain Service, and is available 24hrs a day. The registrar can be contacted by page number 08596. Examples of the methods used are patient controlled analgesia, epidural analgesia and continuous regional analgesia. Patients are usually commenced on their analgesia either at the time of surgery or on the wards after consultation from the primary medical team.
The components of the Multidisciplinary Pain Service are cancer pain treated in association with the oncologists and palliative care physicians and chronic non-malignant.pain.
Further reading:
Acute Pain Management: scientific evidence. NHMRC 1999.
http://www.nhmrc.health.gov.au/publications/synopses/cp57syn.htm
Acknowledegements:
This guideline was produce with input and comments from the following. -
Richard Halliwell, Peter Barclay, David Gronow, Michael Smith and the members of the Westmead Drug Committee.
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