Post-operative Pain management Flashcards
Causes of Post operative pain
Somatic, visceral and neuropathic
Negative effects of pain
Emotional and physical suffering, sleep disturbance
Hypertension and tachycardia, increased O2 use and decreased bowel movements
Delays mobilization leading to DVT
Positive effects of pain
Warning of tissue damage
Immobilization to aid wound healing
Anatomy of pain
Skin nocioceptors to C fibres up the spinothalamic tract to the thalamus and the limbic system
Why do we need analgesia?
Comfort
Mobility (reduces risk of DVT, pressure sores & stiffness)
Respiration and prevents pneumonia in thoracic or upper abdominal surgery
Reasons analgesia may be inadequate
Pain is subjective
Hard to predict severity
Inadequate knowledge of staff
Fear of side effects
What effects the severity of pain?
Site and extent of wound, Age (goes both ways)
psychological & personal factors (anxiety, experience), coexisting medical problems and Drug tolerance
Pre-operative patient education
Measurement of pain
Graded on subjective 1-10 or visual scales
pretty poor really
Surgical Pain ladder
Increasing pain relief depending on operation performed
Start with NSAIDs/paracetamol, then wound infiltration with LA, then peripheral nerve block, then systemic opioids then PCA or epidural
Minor surgery
Inguinal hernia, varicose veins, Gynae Laparotomy
Use paracetamol/NSAIDs + wound infiltration with LA and/or peripheral nerve block
Moderate Surgery
Hip replacements, hysterectomy or maxiliofacial
Use paracetamol/NSAIDs + wound infiltration with LA and/or peripheral nerve block or PCA
Major surgery
Thoracotomy, upper abdominal or knee surgery
Use paracetamol/NSAIDs + epidural/LA opioids or PCA
Management of Pain
Combinations of drugs are best
Usually try to use the best combination of LAs, Opioids and NSAIDs/Cox-2 inhibitors
Opioids
Morphine is gold standard - also diamorphine, papaveretum, fentanyl, codeine, tramadol
Indications for using opioids
Moderate to severe pain
Prescribe on age not weight
Choose route: PO, SC, IV, IM, sub-lingual
Effects of Opioids (6,4,3,3)
CNS: analgesia, sedation, euphoria, coma, tolerance/addiction, pupil constriction
GI: N&V, constipation, biliary spasm, slow gastric emptying
Resp: resp depression, apnoea, cough reflex suppression,
CVS: bradycardia, hypotension + urinary retention
SEs are worse in elderly & in combination with other drugs
Analgesic corridor
The dose range where pain is adequately controlled by side effects are minimised
Sedation score
Awake and alert (0)
Mild sedation (1)
Sleepy but rousable (2)
Unrousable (3)
Methods of administering opioids (4)
IM PRN
IV PRN
Continuous IV infusion
IV PCA
Mangement of opioid overdose
ABC to stabilise
Naloxone 0.4-0.8mg but may need an infusion or to be on ITU/HDU
PCA for opioids
Pros –> titrate to needs, safe, smaller peaks, placebo
Cons –> Needs more monitoring, risk of SEs or OD, N&V
1-2mg bolus with 5-15mins lockout
Oral opioids
Usually codeine with paracetamol (min 3mg/kg/day)
Codeine is metabolised into morphine - similar SEs (sedation and constipation)
Tramadol
IV, IM or oral 50-100mg 8hrly, 100mg = 5-15mg morphine
Reduces 5HT and NAdr reuptake and is a weak opioid agonist - risk of serotonin syndrome if used with SSRIs
Antiemetics
Metoclopramide (benzamide?) - SE - agitation
Cyclizine (antihistamine+anticholinergic) - painful IM or IV
Ondansetron (5-HT3 antagonist) +Dex (unclear mechanism)
Domperidol (butyrophenone) (Prochlorperazine (DA agonist)
Laxatives
Osmotic (lactulose) 15-30ml BD regularly
Stimulant (Senna) 2-4 tabs nocte - short term effect
Oral mild opioid preparations
Codydramol: Dihydrocodeine 6-10mg + paracetamol 500mg
Cocodcamol Codeine 30mg + paracetamol 500mg 1-2 tabs 4-6hrly
NSAIDs
15-60% effect of opioids –> inhibit the production of PGs
Eg Aspirin, ibuprofen, diclofenac
Side effects of NSAIDS
GI–>Gastric irritation, ulceration and bleeding
Resp–>Bronchospasm
Renal–> oliguria, renal failure, elderly at special risk
Skin rashes and antiplatelet effect
Increased risk of MI?
Cox-2 inhibitors
Selectively inhibit Cox-2 enzyme so should be GI sparing
Paracoxib 40mg IV or Celecoxib 200mg OP
Concern over CVS SEs –> may be increased MI risk
Paracetamol
Good SE profile, possible works on cannibinoid or COX-3
1g 4hrly max 4g/24hrs
IM morphine Doses
20-39yrs 7.5-12.5mg 40-59yrs 5-10mg 60-69yrs 5-7.5mg 70-89yrs 2.5-5mg >89yrs 2-3mg
Opioids verses opiates
Opiates are naturally occuring substances similar to morphine - opioids are chemicals with an effect on the opioid receptor (Mew1/2, Kappa & delta)
Aims of post-operative management
Reduce suffering and so improve clinical outcomes by increasing patients ability to move, cough, ADLs etc
