Analgaesia a Practical Approach

By Clare Di Bona

Step wise Approach to Pain Management

Paracetamol

 Analgaesia, antipyretic

  Inihibition of COX however has

limited ani-inflammatory action

 Adverse effects: acute overdose can

cause fatal liver damage generally very well tolerated in normal doses

Classes of Analgaesics

 NSAIDs

  General Considerations:

  Analgaesic, anti-inflammatory effects, antipyretic effects

  Inhibit enzyme (cyclo-oxygenase (COX)) leading to reduction in synthesis of pro-inflammatory prostaglandins

  Selective NSAIDS refers to COX-2 inhibitors COX-2 (celecoxib) less GIT ulcers

NSAIDS

 Prostaglandins have the following actions

  Inflammation

  Pain

  Protective gastric layer

  Maintenance of renal perfusion

  Platelet aggregation

NSAIDS

 NSAIDS block the action of COX reduce production which leads to

  Analgaesia

  Antinflammation

  Decreased gastric mucosa

  Decreased renal perfusion

  bleeding

NSAIDS Mechanism of Action

Non-selective vs Cox-2 selective

NSAID pharmacokinetics

 Absorption: well absorbed orally

 Highly protein bound and small

volumes of distribution

 Hepatic metabolism, renal excretion

 Half-life generally short (1-4hrs)

except naproxen (12-15hrs).

Pharmacokinetics Opioids

  Absorption: well absorbed IV, IM, PO. Intra-nasal routes can avoid first-pass metabolism (fentanyl).

  Distribution: rapidly leaves blood department and goes to highly perfused tissues: brain, lungs, liver, kidney, spleen

 Metabolism:

  Hepatic metabolism. 10% morphine is

metabolised into active metabolite morphine-3-glucuronide

Pharmacodynamics Opioids

 Mechanism of action:

  Produce analgaesia by binding to specific G-

protein coupled receptors primarily in the brain and spinal cord region involved in the transmission and modulation of pain

  Three major classes of receptors: Mu, Delta, Kappa

  Most analgaesic act as the Mu receptor (analgaesia, euphoria, respiratory depression, physical dependence)

Organ System Effects of Morphine

  CNS

  Analgaesia

  Euphoria

  Sedation

  Respiratory Depression (suppresses the

sensitivity of the medullary respiratory center to hypercapnia)

  Cough Suppression

  Mioisis

  Truncal rigidity

  Nausea and vomiting

Organ System Effects of Morphine

  Cardiovascular

  Bradycardia

  GIT

  Nausea and vomiting

  Constipation

  Constrict biliary smooth muscle result biliary colic

  Renal

  Decreased renal function via reduced renal plasma flow

  Uterus

  Prolong labour and reduced uterine tone

  Skin

  itchiness

 GIT

Nalaxone

  Pure opioid antagonist

  Antidote used for opioid toxicity

  Competitively binds to opioid receptors

  Indicated patients with opioid intoxication

with significant CNS or respiratory depression

 Given IV 400mcg stat in critical situation or titrated (50-100mcg boluses)

 May need up to 2mg initially

Simple Analgaesia

 Paracetamol 1g QID oral

  Use if no contraindications ie liver

dysfunction

 Add NSAID if no contraindications

  Celecoxib 100mg bd oral OR

  Naproxen 500mg bd oral OR

  Ibuprofen 400mg tds oral

PRN Oral options

  Tramadol 50-100mg 6hrly oral (avoid use in patients >70yrs, causes delirium)

+/-

 Oxycodone IR 2.5-5mg 4hrly oral (tolerant

patients may need higher dosing, use lowest dose if at all in elderly)

+/-

  Buprenorphine 200-400mcg 4hrly SL

Oral Opioids

  Adverse Effects

  Respiratory: respiratory depression,

bronchospasm

  Cardiovascular: bradycardia, hypotension

  Neurological: confusion, delirium, dysphoria,

euphoria, miosis, cough suppression

  GIT: n+v, LOA, delayed gastric emptying,

constipation

  Musculoskeletal: myoclonus

  Urinary: retention

IV Opioids

 Used for severe pain in adults

  Severe abdominal pain ie renal colic

  Myocardial infarction

  Fractures/dislocations

 Fentanyl titrate up to 100mcg given in 10mcg boluses by nursing staff IV

 Morphine titrate up to 10mg given in 1mg boluses IV

Safety Tips

  Sedation is the first sign of narcotisation then drop in RR

  Be very careful in young children (intranasal fentanyl only for severe pain then ask expert advice)

 Give lowest dose possible to relieve symptoms in elderly

  If BP is low already then do not give IV opioids

and stick with simple analgaesia only

Antiemetics

 All PRN options will cause nausea

 Always prescribe in combination with

antiemetic

  Ondansetron wafer 4-8mg tds oral +/-

  Metoclopramide 10mg tds IV or oral

(ondansetron preferred as occassionally metoclopramide causes dystonic reactions)

Case 1

 17yo young lady with presents with terrible lower abdominal cramping

 She is nauseated and using a heat pack when you arrive

 She is due for her period and hasn’t taken any analgaesia at home

 She has a history of very painful periods

Dysmenorrhoea

 Prostaglandins released by endometrial cells at the start of menstruation cause uterine contraction

  If uterine pressure exceeds arterial pressure uterine ischaemia develops

 COCP +/- NSAID mainstays of treatment

Dysmenorrhoea

 Trials show COCP reduce pain compared to placebo

 GP is the best person to start this therapy

 Consider potential side effects ie increased risk veonous thromboembolic disease

 Aim to use

Dysmenorrhoea

 NSAIDs relieve dysmenorrhoea by suppressing prostaglandins

 Treatment to start ideally just prior to onset of pain and to continue for 48-72hrs

 There is insufficient evidence to favour one NSAID over another

Dysmenorrhoea

 Possible regimes:

  Ibuprofen 200-400mg orally tds or qid

max dose 1600mg/day OR

  Mefenamic acid 500mg tds OR

  Naproxen 500mg initially, then 250mg

tds-QID max daily dose 1250mg

Dysmenorrhoea

 Application of heat packs to lower abdo is effective in reducing pain

 Women who do not respond to NSAIDs plus COCP may have a gynaecological disease ie endometriosis causing their pain. Some women may need referral for diagnostic laparoscopy

Case 2

 65yo with a history of renal stones presents with R flank pain radiating to his groin

 He has blood++ in his urinalysis

 The pain is colicky and severe

 He’s a category two and the nurse

passes you his drug chart

Renal Colic

 SEE JEDO Renal Colic Guidelines!

  Initially in the ED

  MILD PAIN

  Panadeine forte +indocid PR+/-buscopan

  SEVERE PAIN

  IV morphine or fentanyl titrated PLUS

  Indocid PR and panadeine forte

Renal Colic

 All patients should take a two week course of

  diclofenac 50mg tds or

  Diclofenac 50mg PR bd or

  Indocid 100mg PR bd

PLUS

  Tamsulosin 400mcg daily

Renal Colic

  In addition to NSAIDS and flomaxtra daily for two weeks

 Use panadeine forte for breakthrough +/- Tramadol

 Pain will recur until stone passes (2-3weeks)

  If pain is as severe as when in hospital need to represent

Case 3

 28yo man has burning pain in his epigastrium

 He was drinking alcohol last night but only had 4-5 drinks which he has had before

 He has no history of pancreatitis or gallstones

Gastritis/GORD

INITIAL TREATMENT

  Pink Lady

  Ranitidine 300mg

  PPI pantoprazole or esomeprazole 40mg

PO

LIFESTYLE ADVICE

  Avoid alcohol, high fat meals, citrus fuits,

spicy food, carbonated drinks

  Eat smaller meals, fluid between meals,

avoid lying down after eating

Gastritis/GORD

  Discharge on

  Antacid ie Mylanta 20mL PRN OR

  Histamine H2 receptor antagonist ie ranitidine 150mg bd

prn OR

  PPI pantoprazole 40mg daily for 2 weeks

  RED FLAGS WARRANT FOLLOW-UP ENDOSCOPY

  Anaemia

  Dysphagia

  Hematemesis +/- melaena

  Vomiting

  Weight loss

Case 4

 55yo lady has crushing central chest pain

 She is sweaty and diaphoretic

 She had an MI many years ago and

has not been taking any antiplatelet therapy

 ECG shows STEMI and she is going via ambulance to SCGH

Acute Coronary Syndrome

  Simple measures to increase 02 delivery to the heart muscle

  GTN (2 sprays PRN if BP tolerates), refractory pain may

require GTN infusion

  Drugs to increase vascular perfusion (aspirin 300mg,

ticagrelor 180mg, heparin IV 500IU bolus in STEMI prior to transfer or infusion in NSTEMI or unstable angina)

  IV opioids

  Titrated IV opioids fentanyl or morphine for severe pain

  Drug-induced ACS add in lorazepam or diazepam

Acute Coronary Syndrome

 GTN is contraindicated in RCA infarction as it’s PRELOAD SENSITIVE

 Hypotension in R sided infarct is treated with FLUIDS

 Nitrates are contraindicated

 HOW DO I RECOGNISE A R SIDED INFARCT?

Acute Coronary Syndrome

Acute Coronary Syndrome

 Occurs in 40% of patients having inferior MI

  ST elevation V1 (looks directly at RV)

  ST elevation lead III > lead II

Acute Coronary Syndrome

Look for ST elevation in V4R

Case 5

 62yo man was taking out the trash and bent sideways

 He felt a twang in his lower back and now feels like it has ‘seized up’

 He is finding it difficult to mobilise from the pain

Lower Back Pain

 Most patients have a nonspecific mechanical cause and self-limiting illness

  Radicular pain (sciatica) indicates nerve root involvement and refers to sharp or burning pain down the lateral or posterior aspects of legs

  Due to herniated lumbar disc 90% or lumbar

canal or faraminal stenosis

  Imaging (CT or MRI required)

Lower Back Pain

  Reg flags (non-mechanical back pain) are features in presentation that indicate the need to exclude potentially serious conditions ie fracture, tumour, spinal infection, ankylosing spondylitis

  Red flags

  Pain localised, always there and not affected by movement/

posture

  LOW

  Fever

  Peripheral arthritis

  Symptoms in other systems (change bowel habit, breast mass,

cough)

  Imaging is required when there is suspicion of non-

mechanical disease (spinal stenosis, nerve root involvement or above mentioned conditions)

Lower Back Pain

 Features of spinal canal stenosis

  Bilateral sensation loss +/- weakness

affecting the legs exac/produced by walking or prolonged standing

  Nerve root injury may occur leading to

  radiculopathy

  Cauda equina syndrome: saddle

anaesthesia, urinary retention, bowel incontinence, absent anal tone

  MRI is the best form of imaging

Back pain

 Nonpharmacological Treatment

  Advice to stay active

  Reassurance and positive

encouragement most people recover in 4 weeks, imaging does not correlate with disease in non-specific back pain

Lower Back Pain

 Paracetamol 1g PO 4-6hrly max dose 4g daily AND/OR

 NSAID orally

 Consider adding for up to 3 weeks

only

  Codeine 30-60mg PO QID PRN or

  Tramadol 50-100mg QID PRN or

  Oxycodone 5-10mg 4hrly PRN

Case 6

 23 yo lady presents with unilateral throbbing headache

 Her mum is very concerned about the level of pain

 She is photosensitive

 She has a history of migraine

Migraine

  Non pharmacological: advise patient to rest in quiet room

  Initially:

  Aspirin 600-900mg can repeat in 4hrs OR

  NSAID

  Diclofenac 50-100mg can repeat in 6hrs OR

  Ibuprofen 400mg can repeat in 6hrs OR

  Naproxen 550-825mg can repeat in 6hrs

OR

  Paracetamol 1g can repeat in 4hrs

Migraine

 Antiemetic can relieve nausea and also relieve migraine pain

  Metoclopramide 10mg IV tds PRN OR

  Prochlorperazine 12.5mg in 1L NS over

2hrs (can lead to light headedness if given in larger doses quickly)

Migraine

  If the above therapy fails a tryptin can be added

  Sumitriptan 50mg-100mg PO up to

300mg in a 24hr period

  May need the nurse to get pharmacy to

delivery (0800-1700)

Case 7

 2yo Sam fell off the see-saw and has 2cm chin laceration

 He is very brave and lets you take off the dressing

 He will not allow you to touch the wound without screaming

Suturing in Children

 Option A: hold child down to inject local anaesthetic and suture in ED

 Option B: Use topical anaesthetic first then hold child down and inject more anaesthetic then suture

 Option C: Use ketamine sedation then inject local and perform procedure

 Option D: Offer plastics referral for the plastic surgeon to suture

 Option E: Glue

Suturing in Children

  No right or wrong answer

  Give parents the options and let them decide

  The topical anaesthetic takes 40 minutes to work

  Holding down the child (option A and B) can be

traumatic for child and parents

  Ketamine sedation child has to be fasted, will need

to stay for at least 1-2 hrs post to become more alert and this is difficult at night when it’s the child’s usual bedtime

  Need a dedicated nurse for a prolonged period for ketamine

  A plastic surgeon gives a better cosmetic result and any facial laceration in child, parents should have this option

  Wound needs to be straight and well opposed for glue

Local Anaesthetic Options

 Laceraine

  Each 5ml contains 5mg adrenaline,

lignocaine 200mg, amethocaine 25mg

  Dose 0.1ml/kg max 3ml

  May not provide full anaesthetic cover

may need top up infiltration

 Lignocaine 1%

  Each 5ml contains 50mg lignocaine

  Up to 3mg/kg

Ketamine

  SEE PMH Guideline

  Can only occur with consent of consultant

and nurse manager of paeds area

  It is a dissociative anaesthetic has

anxiolytic, amnesic and analgaesic properties

  Requires two doctors: airway doctor and procedure doctor and one nurse who stays with patient including during their recovery

Ketamine

Ketamine

  Can be given IM 4mg/kg or IV 1-1.5mg/kg

  Possible adverse events

Ketamine

Pain Relief for Severe Pain in Children

 Dylan is 5yrs old he has a displaced distal radius fracture after falling off the slide.

 He is awaiting surgery and is crying out in agony

Pain relief in Children

 Simple analgaesia

  Paracetamol DOSE 15mg/kg/dose

  Not to exceed 4 doses in 24hrs of any

paracetamol products

  Oral liquid different formulations

  Tablet 500mg tablet

  Rectal suppository 125mg or 250mg (20mg/

kg 4 doses in 24hrs max)

Pain relief in Children

 Painstop for more severe pain

 Has codeine as well as paracetamol

 Each 5ml contains

  120mg paracetamol and 5mg codeine

  I only use Painstop Day-Time

 Dose 0.6ml/kg/dose 6hrly (max 4

doses in 24hrs)

Pain Relief in Children

  Neurofen 10mg/kg 6hrly max 400mg/dose

 Well absorbed, peak levels after 1hr

  Half life 2hrs

  Take with food

 Maybe used in combination with

paracetamol

  Don’t use in children

Intranasal Fentanyl

  1.5mcg/kg/dose intranasal

  A second dose can be administered if

required

 Onset of action 5 minutes

  Duration of effect 30-45min

  Calculate lean body weight in overweight

children

  Side effects uncommon include: respiratory

depression, hypotension, nausea/vomiting, itch

Case 8

 78 year old lady had an unwitnessed fall at the nursing home

 She has a shortened externally rotated R leg

 She says she is not in pain but cries out when the nurse tries to put a catheter in

NOF fracture

  Nerve block

  Avoid IV opioids if possible

Neuropathic Pain

  Different quality of pain ‘electrical properties’ , allodynia, hyperalgesia

  Causes: amputation, radiculopathy, post inguinal hernia, thoracotomy

  Ketamine and tramadol are good options oral or IV

  Amitriptyline and pregabalin are also good oral options.

 GP/Pain specialists usually treat this type of pain

Neuropathic Pain

  Amitriptyline 10-20mg nocte orally

  Side Effects: sedative, anticholinergic (cardiac

dysrhythmia, dry mouth, constipation, urinary retention)

  Takes several days for effects

  Pregabalin 75mg bd orally (increased after

a few days to 150mg bd and another increase after a few days to 300mg bd)

  Use 50% dose in elderly and renal impairment

  SE dizziness, drowsiness

References

 Uptodate: Dysmenorrhoea diagnosis and treatment, Migraine

 TG: dysmenorrhoea, low back pain, GORD, migraine

 JEDO renal colic guideline

 PMH Ketamine and laceraine

guidelines

 ANZA Pain management guidelines