Adverse pathophysiological consequences of poor pain management

  • Respiratory - if patient is unable to cough and expand lung bases sufficiently it increases risk of chest infection/pneumonia.
  • Cardiovascular – Hypertension, tachycardia, platelet aggregation and venous stasis due to poor pain control
  • Gastrointestinal – Nausea and vomiting
  • Genitourinary – Urinary retention
  • Endocrine – The ‘stress response’ from pain causes release of hormones
  • Psychological – Pain can lead to anxiety, sleep deprivation

Generally, if patient’s pain is well controlled they will recover quicker and be discharged sooner.


Misconceptions about post-operative pain

  • Staff believe that they, rather than the patient, are the authority on the patient’s pain
  • Post-operative pain can not be prevented
  • Patients will become addicted
  • Side effects of analgesics can not be controlled
  • Opioids must not be given more than 4 hourly
  • The same operation produces comparable severity of pain in different people

Pain Assessment

  • Pain must be assessed regularly by asking the patient.  Pain can not be assessed accurately by observers
  • Believe the patient! (pain is the patients own experience)
  • Ask them to rate their pain as ‘none’, ‘mild’, ‘moderate’ or ‘severe’
  • Ask the patient to assess their pain on movement (eg. deep breathing)
  • Pain should be assessed for at least 4 days post-operatively.  Level of sedation and respiratory rate must also be observed (see ward obs sheets)

Principles of good pain management

  • Involve the patient in the management of their pain
  • Aim to predict and prevent pain if possible
  • Analgesics should be prescribed regularly for continuous pain
  • Always use the oral route if possible
  • If patient is requiring regular morphine injections consider PCA
  • Dose and frequency must be individualised.  Opioids (IM) can be given safely 1-2 hourly if patient is stable and has no adverse effects
  • Equivalent morphine doses: IV (5mg) x2 = IM (10mg) x2 = PO (20mg)
  • Next dose of analgesia should be given before previous dose has completely worn off
  • Use multi-modal approach.  Combine use of compound analgesics with NSAID.  The addition of an NSAID or paracetamol will reduce need for opioids by 30%.

Recommended Analgesics

  • Paracetamol (use for mild pain)
    • Dose: 1g qds
    • Side effects : Only hepatic damage in overdose
  • Compound analgesia (use for mild-moderate pain)
    • Action: Contain mild opioid which binds to opioid receptors in dorsal horn
    • Preparation of choice : Co-dydramol (dihydrocodeine 10mg and paracetamol 500mg)
    • Stronger alternative : Co-codamol 30/500 (codeine 30mg and paracetamol 500mg)
    • Soluble preparation : Co codamol 8/500 (codeine 8mg and paracetamol 500mg)
    • Dose : x2 qds
    • Side effects : Constipation, nausea and vomiting and drowsiness (treat with ant-emetics and laxatives DO NOT WITHDRAW ANALGESIA)
  • Buprenorphine (PO only at the moment)
    • can be used as an alternative for moderate to severe pain.  It has less incidence of respiratory depression and constipation.  But can cause more nausea and vomiting.
    • Dose: 50-100mg qds with paracetamol 1g qds
  • NSAIDs (use with compound analgesia/paracetamol)
    • Action : Inhibits inflammation (prostaglandin synthesis) that causes pain after surgery
    • Drug of choice : Diclofenac (voltarol) 50 mg tds PO/100mg od PR
    • Alternative : Ibuprofen 400mg qds
    • If patient NBM and can not receive PR drugs : Piroxicam melt 20mg od
    • Contraindications : NSAIDs should not be given to patients with poor renal function, dyspepsia or peptic ulcer, abnormal coagulation, cardiac failure or cirrhosis.  Care should be taken in asthmatics and in patients >70 years old.
  • Opioids (use for moderate – severe pain with NSAID/paracetamol)
    • Action: Binds to opioid receptors in dorsal horn
    • Drug of choice: Morphine
    • (Pethidine is no longer recommended due to short half-life, it is no safer than morphine and risk of toxicity from metabolite norpethidine in high doses, no advantage in pancreatitis)

Guidelines for post-operative intramuscular analgesia

Age Weight  Morphine Dose
 <70yrs  >65Kg  10mg
 <70yrs  <65Kg  7.5mg
 >70yrs  >65Kg  7.5mg
 >70yrs  <65Kg  5mg

Frequency : every 2 hours providing that:    

  1. Pain score 2 or 3
  2. Sedation score is 1 or 2
  3. Systolic BP >100mmHg
  4. Resp rate >10/min

Management of pain

  1. Pain score mild/no pain - consider change to oral analgesia
  2. Pain score moderate-severe - Repeat morphine dose 2 hourly for up to 3 doses and consider NSAID/paracetamol
  3. Pain score still remains moderate-severe - Clinical review +/- Acute Pain Service

Contraindications and side effects:

  • Liver disease and renal impairment (action of opioids is prolonged)
  • Causes respiratory depression which may further elevate intracranial pressure for patients with head injury.
  • Hypotension may be aggrevated
  • Nausea and vomiting (treat with anti-emetics)
  • Urinary retention
  • Sedation
  • Dependence is not likely to occur when used appropriately for the treatment of acute pain
  • Slowing of gastric emptying and GI motility

Guidelines for administration of all opioids via any route

  • All patients must have 4 hourly (if stable) pain score, sedation score, respiratory rate and blood pressure recorded if on opioids
  • All patients must have an anti-emetic prescribed PRN
  • Patients over 60 years old must have oxygen prescribed
  • Do not give other sedatives with opioids
  • If sedation score unrousable (>2), respiratory rate<10 or BP<90mmHg STOP ALL OPIOIDS AND REVIEW IN 15 MINS

Other methods of treating acute pain

Patient Controlled Analgesia (PCA)

PCAs are usually set up from theatre for patients undergoing intermediate - major surgery.  PCAs can also be set up for patients that are having regular IM injections of an opioid and NBM.  The system allows the patient to self-administer a small IV bolus of an opioid analgesic.  An IV loading dose needs to be given to establish analgesia before PCA is started.  The system has a lockout period built into it to allow the patient to re-assess their pain before administering a further dose.  The safety mechanism of the pump is that the patient MUST be the only person to press the button so if they become sedated they will not be able to press the button and overdose.

  • Advantages: Patients experience less anxiety and discomfort.  The delay associated with nurse administered IM analgesia does not occur
  • Disadvantages: Potential for malfunction and user error.  Continuous training of staff is essential.  Needs patient co-operation.

IV opioid infusions

A continuous infusion of opioid can be effectively used post-operatively, especially if patient is unable to use PCA.  Doses can be altered but it is not as safe as PCA and serious respiratory depression, regular monitoring required and may not be appropriate for general ward

Inhalation analgesia

Entonox (50% nitrous oxide and 50% oxygen) may be useful during short periods of post-operative pain (e.g. during physio, or removal of drains/dressings).  It cannot be used continuously because nitrous oxide causes bone marrow depression.

Local Anaesthesia

  • Action: Blocks transmission of nerve impulses
  • Advantages: Profound analgesia without opioid-like side effects
  • Disadvantages: Local anaesthetics are toxic in large quantities and short duration of action.  Some techniques are time-consuming and require specialist skills.
  1. Local Infiltration of wound site at the end of operation provides short term analgesia
  2. Nerve blocks are performed by the anaesthetist and require local anaesthetic to be injected around peripheral nerves and gives excellent pain relief
  3. Spinal anaesthesia blocks the nerves as they leave the spinal canal and before they separate into branches, resulting in analgesia in deep tissues as well as around the wound.  Hypotension is a serious side effect

Epidural analgesia

  • A catheter can be left in place in the epidural space post-operatively.  A combination of continuous local anaesthetic and opioid is used.
  • Advantages: Excellent analgesia allowing early mobilisation.  Reduction in stress response and post-operative complications. A reduction of opioid-like side effects has been shown.
  • Disadvantages: Hypotension (usually related to hypovolaemia).  Risk of epidural abcess, haematoma or nerve damage (very rare).

Complementary Therapies (to be used with analgesics)

  1. Reassurance.
  2. Education / Information.
  3. Relaxation.
  4. Imagery.
  5. Distraction.
  6. Hypnosis.
  7. Application of heat or cold.
  8. Massage.
  9. Aromatherapy.
  10. Exercise or Immobilisation.
  11. Transcutaneous Electrical Nerve Stimulation. (T.E.N.S.)
  12. Acupuncture.


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