Management of Acute Postoperative Pain Dr Alice Man Department of Anaesthesia & Intensive Care The Chinese University of Hong Kong Prince of Wales Hospital
Case scenario You are a houseman in an acute hospital
“By any reasonable code, freedom from pain should be a basic human right, limited only by our knowledge to achieve it” • - Liebeskind JC & Melzack R
IASP definition of Pain • An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage.
Factors affecting postop pain • A. Surgical factors: • 1. site of incision and nature of the surgery • upper abdomen > thoracotomy > lower abdomen > limbs • 2. complications, eg wound infection, intraabdominal sepsis, distension • B. Patient factors: • Psychology, genetic, hx of substance abuse, hx of chronic pain
Causes of postop pain • 1. Incisional- skin and subcutaneous tissue • 2. Deep- cutting, coagulation, trauma • 3. Positional- bed sore, nerve compression & traction • 4. IV site- needle trauma, extravasation, venous irritation • 5. Tubes- drains, nasogastric tube, ETT • 6. Respiratory- from ETT, coughing, deep breathing • 7. Rehab- physiotherapy, movement, ambulation • 8. Surgical- complication of surgery • 9. Others- cast, dressing too tight, urinary retention
Acute pain service • 1. Education • 2. introduction and supervision of more advanced analgesic techniques e.g. iv PCA • 3. improvement of traditional analgesic Tx • 4. standardization of equipment, standing order, guidelines, protocol • 5. 24-hr availability of pain service personnel • 6. collaboration and communication with other medical staff • 7. audit of pain service • 8. research
Pharmacology What drug to give?
Analgesic • 1. Simple analgesic • Paracetamol-for mild pain, caution with liver impairment • Dologesic- paracetamol+propoxyphene- mild to moderate pain
2. NSAID • - Mild and moderate pain • - Opioid sparing • - SE: peptic ulcer and bleeding, platelet aggregation inhibition, bronchospasm, renal impairment, allergy • - CI: bleeding, hypovolaemia, GIB, pregnancy, breast feeding, hypersensitivity, renal impairment, asthma
3. Opioid • e.g. morphine, pethidine, fentanyl , codeine phosphate, methadone, dextro-propoxyphene • Desirable effects: Analgesia, Sedation • Adverse effects: Over sedation, Respiratory depression, Nausea & vomiting, Pruritus, Urinary retention, Constipation, Dysphoria, hallucination, Addiction
4. Local anaesthetics • e.g. bupivacaine (marcain), lignocaine • used in epidural and regional analgesia • features of LA toxicity : perioral numbness, dizziness, tinnitis, diplopia, drowsiness, convulsion coma, respiratory depression, CVS depression
Methods of postop analgesia • 1. Oral/ PR • 2. Intramuscular • 3. intravenous-intermittent bolus, continuous infusion
Non-pharmacological • 1. Psychotherapy: distraction, information • 2. Behavioral therapy: modification • 3. Physical therapy: TENS, acupuncture, cryoanalgesia, heat therapy
Consequence of PONV • Delayed in oral intake, dehydration, e imbalance • Tachycardia, arrhythmia, salivation, pallor • Oesophageal tear, disruption of surgical anstomosis, wound dishiscence, increased ICP, IOP, haematoma • Aspiration pneumonia • Delayed in discharge, unplanned hospital admission
Case scenario You are a houseman in an acute hospital
Case 1 • While u are having dinner in the canteen, a ward nurse call u, “Mrs Chan came back from OT just now and her recent blood pressure is 70/40. She has an epidural.” • What are u going to do? • What is the definition of “shock”? • Any investigation?
Hypotension • Epidural analgesia- sympathetic blockade, iv PCA • Ddx: hypovolaemia, cardiogenic, distributive, obstructive • Mx: • 1. Assess patient, recheck BP • 2. ABC • 3. give O2 • 4. stop epidural infusion, iv PCA • 5. iv fluid challenge, vasopressor • 6. exclude other causes e.g. haemorrhage
Case 2 • Mr Chan, 50yr old gentleman, postop D2, on iv PCA LOC • What will u do? • What are the differential diagnosis? • What is the management for opioid overdose?
Opioid overdose • Causes: human error, equipment malfunction, patient risk factors, • Presentation: Altered conscious state, slow RR, desaturation, small pupil • Ddx: stroke, electrolyte disturbance, hypoxaemia, hypercarbia, hypotension
Mx • 1. ABC • 2. ? drowsy, rousable • 3. stop PCA/ Continuous infusion • 4. give O2 via mask, ambu bag • 5. monitor closely • 6. inform APS • 7. give 0.1mg naloxone iv and repeat 3-5min as necessary
Case 3 • 60 years old female • morbidly obese • evidence of obstructive sleep apnoea • on DVT prophylaxis - fraxiparine • require anterior resection • You are an anaesthetist, what mode of postop analgesia would you choose? • Any precautions concerning the postop analgesia?
Choice of analgesic modality • 1. Patient factors: physical conditions, age, cognitive ability, previous experience, psychological state, oral diet, drug interaction • 2. Surgical factors: type and extent of surgery, surgical complication • 3. Anaesthetic factors: anasthetic technique, expertise, available resource, ward nurse training
Considerations • abdominal surgery • adverse effect of pain to heart • effect of systemic opioid • effect of anti-coagulant • technical difficulty on epidural insertion
Options: • Options • opioid - IV PCA • epidural - PCA Pethidine • epidural infusion - LA + fentanyl • Note • anticoagulant and epidural
Case 4 • Miss J, a 20 yr old patient just had a laparoscopy performed and asked u, “ Can I get some antiemetic?” • What would u do? • What are the risk factors for postop nausea & vomiting? • Any treatment?
High risk of PONV • Patient: young, F, early preg, previous hx of PONV, motion sickness, anxiety • Increased gastric vol: obesity, blood in stomach • Anaesthetic technique: RA vs GA, N2O, opioid • Surgical: duration, laparoscopy, eye, ear operation • Post op: pain, movement, hypotension, forced oral fluid
Mx • Ensure pain control, adequate hydration, oxygenstion, slow and deep breath, stable BP, gentle handling of pt
Pharmacological • -Anticholinergic: scopolamine • -Phenothiazine: prochlorperazine, promethazine • -Butyrophenones: droperidol • -Benzamides: metoclopramide • -Antihistamine: cyclizine, diphenhydramine • -Corticosteroid: dexamethasone, betamethasone • -5-HT antagonist: ondansetron, topisetron