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AS8.1-5 | Pain and Its Management — PBL Case

CLINICAL SETTING

Mrs. Asha Pillai is a 58-year-old school teacher with Stage IVB carcinoma of the cervix, diagnosed 14 months ago. She received concurrent chemoradiation (cisplatin + external beam) followed by brachytherapy, with an initial partial response. She was referred to the palliative care outpatient clinic after disease progression documented on CT three weeks ago — new para-aortic lymph node metastases and bilateral hydroureteronephrosis. She arrives with her daughter. She describes her pain as consisting of two distinct problems: (1) a constant, deep, cramping pain in her lower abdomen and pelvic area that she rates 7/10 at rest and 9/10 when she tries to walk, and (2) a burning, shooting pain that starts in her lower back and radiates down her right leg to the knee — she calls it 'like an electric shock that will not stop' and rates it 6/10. She is also passing urine through a vesico-vaginal fistula and is severely distressed by the loss of continence. She is currently on diclofenac 75 mg twice daily (prescribed by her oncologist) and occasional paracetamol 500 mg when she remembers. She weighs 47 kg. Her daughter hands you a card: 'Doctor, please do not tell her how serious this is — she thinks she is getting better.' The palliative care nurse notes the patient appears anxious, is guarding her abdomen, and scored 9/10 on the Critical Care Pain Observation Tool during her transfer to the clinic room.

Trigger 1: Understanding the Pain: Assessment and Characterisation

The palliative care registrar conducts a structured pain assessment. Using the SOCRATES framework and a systematic history, she identifies three pain components: (1) Visceral nociceptive pain from tumour mass in the pelvis — continuous, cramping, poorly localised, NRS 7–9/10, worse with movement and micturition. (2) Neuropathic pain from right lumbosacral plexus invasion by para-aortic nodes — burning, shooting, electric quality, radiating L4–S1 distribution down the right leg, NRS 6/10, partially relieved by sitting still. (3) Psychological distress (anxiety, existential suffering from incontinence and poor prognosis) — recognised as a distinct domain contributing to total pain perception. She also notes a communication barrier — the family's request conflicts with the patient's right to information about her own condition.

DISCUSSION POINTS

  • Which validated pain assessment tool is most appropriate for a semi-ambulant patient who can communicate verbally? How does SOCRATES help you structure this assessment, and what does each element reveal for Mrs. Pillai's two pain types?
  • What is 'total pain' in the palliative care context? How does the psychological, social, and existential dimension of Mrs. Pillai's suffering — incontinence, fear of prognosis, family communication conflict — interact with her physical pain experience and what are the implications for management?
Click to reveal Trigger 2: Pharmacological Management: Building the Analgesic Plan (discuss previous trigger first!)

Trigger 2: Pharmacological Management: Building the Analgesic Plan

Laboratory results arrive: serum creatinine 2.4 mg/dL (eGFR 22 mL/min — severe chronic kidney disease, likely from bilateral hydroureteronephrosis). Haemoglobin 8.2 g/dL. Serum sodium 128 mmol/L. The team reviews her current medications. Diclofenac must be stopped immediately — it is contraindicated in severe renal impairment (COX inhibition reduces renal prostaglandin-mediated afferent arteriolar dilatation, precipitating acute-on-chronic kidney injury) and carries significant GI risk without a gastroprotective agent. A new analgesic plan is needed that: addresses her visceral nociceptive pain (WHO Step 3), manages her neuropathic component with appropriate adjuvants, avoids renally toxic opioids in the context of eGFR 22 mL/min, and considers her low body weight (47 kg).

DISCUSSION POINTS

  • She is opioid-naive and weighs 47 kg. Which strong opioid is safest in eGFR 22 mL/min (consider morphine metabolites M3G/M6G vs fentanyl's metabolic profile)? Calculate an appropriate starting dose and breakthrough dose. What co-prescriptions are mandatory from day one?
  • She has clear neuropathic features (burning, electric, radicular distribution). Which adjuvant analgesic would you add, and what is the mechanism of action? Would you also consider a corticosteroid, and if so which one and why? What is the expected time to analgesic effect for each adjuvant?
Click to reveal Trigger 3: Anticipating the Terminal Phase and Ethical Dimensions (discuss previous trigger first!)

Trigger 3: Anticipating the Terminal Phase and Ethical Dimensions

Six weeks later, Mrs. Pillai is re-admitted as an emergency. She is now obtunded (GCS 11), has developed uraemia (creatinine 6.8 mg/dL), and is clearly in the active dying phase. She can no longer swallow. Her family is present. Her SC fentanyl has been running at 50 mcg/h via syringe driver (the team switched from morphine at week 3 given her renal decline). She is showing signs of pain (grimacing) and has begun producing noisy respiratory secretions. Her daughter insists the team 'do everything possible' including CPR if her heart stops. The palliative care team documents that any CPR attempt would be non-beneficial and confirms with the senior consultant that a DNAR (Do Not Attempt Resuscitation) order is appropriate. The daughter is distressed. Pain and symptom management must continue.

DISCUSSION POINTS

  • She is unconscious and in pain. How do you adjust analgesia? What drugs (with specific SC doses) would you prescribe for: (a) breakthrough pain, (b) terminal agitation/restlessness, and (c) respiratory secretions? What is the ethical justification for continuing opioids at doses that might affect consciousness or breathing?
  • Her daughter insists on CPR. How does the palliative care team balance the daughter's request against the clinical determination that CPR is non-beneficial? What is the ethical and legal framework for a DNAR decision? How would you communicate this to the family, and what support would you offer?

Group Task Assignments

Group 1: Collaborative Task

  • Construct a complete written analgesic care plan for Mrs. Pillai at the time of her initial clinic visit — include the WHO ladder step, specific drug prescriptions with doses (mg/kg where appropriate), breakthrough dose calculation, mandatory co-prescriptions, adjuvant for neuropathic pain, and rationale for avoiding diclofenac in renal impairment. Present this as a structured prescription table with clinical reasoning.

Group 2: Collaborative Task

  • Prepare a 5-minute presentation for your group explaining: (a) why fentanyl is preferred over morphine in renal failure (metabolite pharmacology), (b) how the doctrine of double effect applies to sedating opioid doses in the terminal phase, and (c) what the evidence says about whether appropriately titrated opioids shorten life in terminal illness.

Learning Issues

Research these questions and bring your findings to the discussion.

  1. [AS8.1] How does the gate control theory and the neurophysiology of lumbosacral plexus invasion explain the neuropathic (electric, burning, radicular) pain Mrs. Pillai experiences? What ascending pathway carries this signal to consciousness, and how does central sensitisation contribute to the chronification of neuropathic pain?
  2. [AS8.2] What is the SOCRATES framework and how is it applied in a structured pain history? What validated tools assess pain in non-communicative patients (CPOT, PAINAD)? What is 'total pain' in palliative care and how do psychological, spiritual, and social domains modulate physical pain perception?
  3. [AS8.3] Compare the metabolic profiles and renal safety of morphine (M3G/M6G accumulation in renal failure → neurotoxicity) versus fentanyl (CYP3A4 hepatic metabolism, inactive metabolites, not renally cleared). What are the first-line adjuvant analgesics for neuropathic pain, their mechanisms, and their starting doses? What makes diclofenac dangerous in renal impairment?
  4. [AS8.4] What are the WHO principles for opioid titration in cancer pain ('by mouth, by the clock, by the ladder')? How is the breakthrough dose calculated? What is the role of dexamethasone in malignant nerve compression pain, and when is a corticosteroid inappropriate?
  5. [AS8.5] What are the standard anticipatory prescriptions for the dying phase (SC opioid, SC midazolam, SC hyoscine hydrobromide — with doses)? What is the doctrine of double effect and how does it apply to sedating opioid doses in the terminal phase? What does evidence say about whether appropriately titrated opioids shorten survival?