Pain and Analgesia
Pain is a primitive and survival symptom, it is the way our bodies tell us there is something wrong.
Analgesia is the relief of pain, usually without any significant impact on conscious state.
Sedation is the dulling of perception without the complete loss of consciousness normally seen with anaesthesia.
Anaesthesia means to remove all perception of stimulation and is classically divided into local and general. Local anaesthesia is where only a localised area or region is anaesthetised, and the patient’s conscious state is unaltered.
General anaesthesia is where the patient is rendered unconscious, and hence does not perceive sensation. With general anaesthesia there is a risk that the reduction in conscious state will have a negative impact on the patient’s airway, breathing and cardiovascular system, with risks of airway obstruction, stopping or inadequate breathing and low blood pressure. If not rapidly detected or appropriately responded to, can rapidly result in death. This is why where ever possible local is preferable to general anaesthesia. The problem is that manufacturing general anaesthetic agents is actually easier than manufacturing local.
Anything beyond the administration of some oral pain killers is moving into risky territory. In the realms of analgesia and anaesthesia if you do not know what you are doing, you will kill people.
a. Analgesia
The reason we need analgesia is because of ....... pain !
1. Pain
Pain is a very individual thing. What is only mild pain to one person is severe pain to someone else.
The perception of pain is influenced by both genetic and cultural factors.
Particularly the cultural, different cultural groups can react in very different ways. The patients presenting with a painful condition is not in isolation from their cultural background and this needs to be a consideration. What can you bring from the patients culture to minimise or reduce the pain?
Family / Friends
Elder
Special food
A special ceremony
2. What is pain?
Pain has various definitions and all are relatively general.
Broadly there is general agreement that “pain” is “ a noxious stimulation and the physical or emotional response to that stimulation”.
A simplistic way to think about pain is:
1. Mechanical stimulation of pain receptors in the skin or connective tissue.
2. Generates impulses which are transmitted by a peripheral nerve to the spinal cord.
3. The impulse is then transferred to dorsal horns of the spinal cord
4. The impulse is transported up the spinal cord to the brain and is perceived in the brain as a noxious or painful stimulus.
These impulses can be modified by drugs or neuro-mediators in the brain itself or as they travel; e.g. local anaesthetic blocks peripheral nerves; morphine turns down the transmission in the spinal cord and part of the brain.
This is an oversimplification but provides a brief overview.
Most of pain we deal with in an austere environment is acute pain (i.e. a broken leg or acute chest pain), however a small group will present with chronic pain (i.e. back pain or headaches which are always or usually present) and these patients are difficult to manage in an austere environment and here culture and non-drug factors would usually become the front line treatments.
3. Treating pain / Analgesic agents
Non-Drug therapies
Given the huge psychological input into pain perception it should follow that there are many other techniques which can help manage people’s pain. This spectrum extends from play therapy in children, to distraction techniques, to specific psychological interventions.
Distraction
This can extended from a child playing with a toy or talking about their favourite food or recipe during a painful procedure to simply talking about the weather with a patient while you insert an IV.
You cannot change the fact applying traction to a broken leg is painful- but you can reduce the amount of perceived pain significantly by distracting the patient.
Transcutaneous electrical nerve stimulation (TENS)
TENS is a non-invasive procedure, intended to reduce pain by nerve stimulation, it works on both acute and chronic pain, its effective for postoperative pain, osteoarthritis, and chronic musculoskeletal pain particular back pain.
Ice or cooling
Ice works muscle strains and sprains, particularly in the first 48-72 hours following the injury. Ice reduces swelling and provide some pain relief by numbing surrounding tissue. Cooling encourages warm blood to the injury site, brining oxygen and nutrients to aid in the healing process. Never apply ice directly to the skin and no more than 20 minutes for a time. Cooling can be achieved with a chemical ice pack or a bag of ice wrapped in a towel
Heat or Warming
The application of Heat increases circulation to the injury site. It should be applied after 48-72 hours following an injury. Heat can be applied via a chemical pad or a moist hot towel. Be careful not to burn or scald the skin.
The “Placebo Effect”
This is discussed also in chapter xx. The “placebo effect” is when a drug exerts a clinical effect in excess of what you would expect for that drugs pharmacological effect. Its definition has been expanded clinically to encompass the psychological effects we see with specific drugs.
While important for all drugs, the placebo effect is very important for analgesic drugs .because the perception of pain is so subjective, its relief is influenced significantly by factors beyond the drug itself. Your ability to “sell” a pain relief agent to the patient has a huge influence on how effective it is.
Compare these strategies:
“I do not think this drug xyz will help, but I’ll give it to you anyway, maybe it will work”
With this approach...
“This drug xyz is wonderful for the sort of pain you’ve got, if we combine it with drug abc it will be fantastic and really help”
The second approach will be much better than the first – it is important to acknowledge that psychological frame of mind and our ability to “sell” a drug in any given circumstance is really important to that drug’s effectiveness. Drugs will work regardless of how you present it to the patient, but we have the ability to greatly enhance their effectiveness.
Pain ladders / Escalation strategies
The basic concept behind ‘pain ladders’ is that drug therapy can be escalated and that we should start where possible with the lowest possible dose of a drug or class of a drug to begin with. Start simple and if it is ineffective then escalate to the next level (or rung). In an austere situation, it is somewhat complicated by lack of intermediate steps between mild and strong or even access to drugs at all.
Clearly this pain management approach does not work for everyone but it provides a framework for therapy.
Drug therapy.
It very easy to stock up on simple over the counter medication and it is likely that even in a preparedness scenario or austere environment they will be available, so they are a good place to start.
Simple
Paracetamol (or as it is called in the US Acetaminophen )
Notes
Paracetamol is on one of the first rungs of the analgesia ladder. It has a bad reputation for being ineffective, but that is almost completely down to inadequate or infrequent dosing.
When used at an appropriate dose (1 gram for Adults or about 20mg per kg / every 4 hours, up to 4 times a day) it is very effective in managing mild to moderate pain and even taking the edge off severe pain. Adult maximum dose 4 gram per day.
We encourage its early and aggressive use for most painful conditions, and when combined with a good “sell” from the medic it may be sufficient for some quite significant pain.
Paracetamol also has the added effect of reducing fever (anti-pyretic) and this alone can make an unwell patient feel much more comfortable.
It is dangerous to exceed the recommended dose in 24 hours due to its effect on the liver.
Exclusion
Concurrent use of other paracetamol based medicines, Hypersensitivity to paracetamol, Known liver disease
Cautions
Alcohol dependence, Patients taking warfarin. Prolonged regular use of paracetamol possibly enhances warfarin (increased INR).
Side effects
Side effects are rare but include rashes, hepatic and renal damage in over dosage, blood disorders and pancreatitis with prolonged use
NSAID’s (Non steroidal anti-inflammatory drugs)
These drugs (such as Aspirin, diclofenac, ibuprofen and naproxon) work by inhibiting the production of prostaglandins. So they are particularly good where the pain is due to local prostaglandin productions – such as muscle and joint sprains, fractures or renal colic.
They are available over the counter in most countries and are worth stocking up on
In most pain they are synergistic (effect of both together is better than that obtained with either one alone) with Paracetamol
The main problems with NSAIDs are kidney damage (more common if patient already dehydrated) or irritation of the lining of the stomach, sometimes resulting in significant bleeding. But if used in the recommended doses for short periods they are very safe and effective. (400mgs 4-6hourly; max 2.4g daily)
Aspirin (NSAID)
Notes
Aspirin 300mg Tablet
Simple analgesia and treatment of suspected Myocardial infarction (Heart attack)
Exclusion
Patients with haemophilia and other clotting disorders.
Known hypersensitivity to aspirin or any ingredient in the product.
Cautions
Asthma, uncontrolled hypertension, pregnancy, breast feeding and active peptic ulceration.
Current treatment with anticoagulants, as the likely benefits of a single 300mg aspirin dose outweighs the potential risks; aspirin may be given to the above if for he treatment of suspected heart attack.
Side effects
Nausea, vomiting and dyspepsia, hypersensitivity reactions e.g. urticaria and bronchospasm, gastro-intestinal haemorrhage, also other haemorrhage (e.g. subconjunctival).
Wheezing in some asthmatics.
Diclofenac (NSAID)
Notes
50mg Tablets, Maximum of 3 doses (150mg) in 24 hours.
Take medicine with or after food or milk.
Do not take any other NSAID-containing product whilst taking this medication e.g. aspirin.
Can be given in combination with paracetamol.
If condition worsens or symptoms persist then seek further medical advice.
Exclusion
Previous sensitivity to NSAIDS e.g. aspirin, ibuprofen any ingredient contained in the product.
History of peptic ulceration.
Asthmatics have severe asthma or had worsening of asthma symptoms after previous use
Known heart failure, renal or hepatic impairment.
Currently taking ciclosporin, clopidogrel, corticosteroids, lithium preparations, methotrexate, other NSAIDS, tacrolimus, warfarin.
Patients with coagulation defects, Porphyria, Pregnancy and breastfeeding.
Cautions
May worsen control of asthma and hypertension.
Elderly. Increased risk of side effects.
Asthmatics that have never used NSAIDs.
Side effects
Gastrointestinal discomfort and occasionally ulceration and bleeding
Nausea and diarrhoea. Hypersensitivity reactions: rashes, angioedema & bronchospasm.
Ibuprofen (NSAID)
Notes
Take with or after food or milk. Ibuprofen may be taken with paracetamol if necessary. Advise patient not to take other NSAID containing products at the same time e.g. over-the-counter medicines containing aspirin.
Ibuprofen tablets 200mg or 400mg or a solution containing 100mg/5ml.
Child 1 – 3 months (or less than 5kg) : 5mg/kg TDS
Child 3 – 12 months (over 5kg) : 50mg TDS
Child 1 – 4 years: 100mg TDS
Child 4 – 7 years: 150mg TDS
Child 7 – 12 years: 200mg TDS
Adult and Child over 12 years: 200 mg – 400mg TDS – QDS
Child 1 – 3 months: 5mg/kg TDS
Child 3 months to 12 years: 30mg/kg in 3 – 4 doses
Adults & children > 12 : maximum 1.6 grams/day
Exclusion
Hypersensitivity to aspirin or any non-steroidal drug (NSAID);Peptic ulceration; asthma; known renal, cardiac or hepatic impairment; taking warfarin; Pregnancy.
Children under 3 months or body weight under 5kgs. Not to be used purely as antipyretic in children <5years
Cautions
Monitor for sensitivity reactions, may worsen control of asthma and hypertension.
Severe liver impairment.
Side Effects
GI discomfort, nausea, diarrhoea and occasionally bleeding & ulceration. These effects may be minimised by taking these drugs with food & milk. Hypersensitivity reactions – rashes & bronchospasm. Oedema has been reported in association with ibuprofen treatment.
Naproxen 200 mg (NSAID)
Notes
Adults and children 12 years and older
Take 1 tablet every 8 to 12 hours while symptoms last, for the first dose you may take 2 tablets within the first hour. Do not exceed 2 tablets in any 8- to 12-hour period or 3 tablets in a 24-hour period
Exclusions
If you have ever had an allergic reaction to any other pain reliever/fever reducer. Naproxen may cause a severe allergic reaction, especially in people allergic to aspirin. Do not use the night before or after heart surgery.
Cautions
Have had stomach ulcers or bleeding problems, take a blood thinning (anticoagulant) or steroid drug, take other drugs containing prescription or nonprescription NSAIDs (aspirin, ibuprofen, naproxen, or others), have 3 or more alcoholic drinks every day while using this product, Have a history of stomach problems, such as heartburn, have high blood pressure, heart disease, liver cirrhosis, or kidney disease, are taking a diuretic or have asthma
Side effects
Indigestion, heartburn, stomach pain, nausea, diarrhoea, constipation, wind, headache, dizziness, nervousness, mood changes, drowsiness, and difficulty sleeping
If you experience any of the following, seek urgent medical help; Any sign of bleeding in the stomach or intestine, such as blood in vomit or dark stools, Any shortness of breath, or swelling of the mouth or face, A severe skin rash, A severe headache with a high temperature and a stiff neck.
(Drugs.com 2013)
Codeine
Notes
Codeine is a precursor of morphine and this is how it exerts it effect.
The problem is not everybody metabolises it to morphine limiting its effectiveness and it is frequently accompanied by severe constipation.
Both of these factors limit its effectiveness.
Head to head analgesic studies have not really shown any difference in effect between paracetamol alone and paracetamol with codeine.
Combined with the fact they are often tightly controlled due to the fact they are an opiate limits codeine usefulness.
30-60mg every 4 – 6 hours (3-4 times a day) if required for mild to moderate pain.
30-60mg every 4-6hours (3-4 times a day) if required for abdominal pain associated with diarrhoea
Maximum 240mg in 24 hours.
Advise patient not to drive or operate machinery as tablets may cause drowsiness or dizziness.
Inform patient that if codeine is taken with other medicines that have a sedative effect e.g. sleeping tablets, antidepressants, alcohol etc. then drowsiness is likely to increase. Regular or prolonged use of codeine can cause constipation.
If condition worsens or symptoms persist then seek further medical advice.
Exclusion
Patients with known alcohol dependency or intoxication. Current or previous opiate dependency, known severe liver disease, previous allergy to codeine. Pregnancy and breast-feeding.
Cautions
Hypotension, hypothyroidism, severe asthma, decreased respiratory reserve, prostatic hypertrophy and myasthenia gravis.
Renal or hepatic impairment.
Head injuries and raised intracranial pressure.
Side effects
Nausea, vomiting, constipation and drowsiness. Discontinue use if any of the above apply and seek medical advice.
Intermediate
In between simple and strong pain killers there is not much. A number of synthetic opiate drugs discussed under strong agents below are considered to be medium strength, but the reality is they are in fact strong. Some combinations of paracetamol and codeine (Co-Codamol panadeine forte) and Tramadol are considered intermediate level analgesics.
Co-codamol 30/500
(Containing paracetamol 500mg + codeine phosphate 30mg)
Notes
If patient is taking any other paracetamol containing preparation, total daily dose must not exceed 4g
Patients aged 12 years and over:
One or two 500mg/30mg tablets/capsules to be swallowed with water. The elderly are particularly susceptible to opioid side effects and should receive the lower dose. Four to six hourly, maximum 8 tabs in 24 hours
Exclusions
Children under the age of 12 years
Known hypersensitivity to paracetamol or codeine
Current or previous opiate dependency
History of current alcohol abuse
Patient already taking opioids
Obstructive airways disease
Renal/hepatic impairment
Patients who have taken paracetamol-containing products within the previous 4 hours
Patients who have taken 4 or more doses of paracetamol within the previous 24 hours
Cautions
Hypotension, Hypothyroidism, Asthma (avoid during attack), Prostatic hypertrophy, Pregnancy/breast feeding, Elderly (65+), Patients with constipation, If also taking other sedative drugs e.g. antidepressants, anxiolytics, antipsychotics and hypnotics – enhanced sedative and/or hypotensive effect
Side Effects
Nausea, vomiting, drowsiness, constipation. Larger doses produce respiratory depression and hypotension
Tramadol hydrochloride 50mg capsules
Notes
You are advised NOT to drink alcohol with this medicine. Swallow these capsules whole with a glass of water at the same times each day.
Adults and children aged 12 -64
Acute pain (such as after an operation): One to two capsules three to four times a day. To be taken for as long as prescribed by your doctor.
Chronic pain (such as that associated with cancer): one or two capsules at first, then one to two capsules every 4 to 6 hours according to the severity of your pain.
Take no more than eight capsules (400mg) in any 24 hour period unless told to by your doctor.
Elderly: One to two capsules every 9 hours, Patients with liver or kidney impairment: One to two capsules every 12 hours. Children:
Not recommended for use in children aged under 12 years.
Exclusions
Allergic (hypersensitive) to tramadol hydrochloride, or any of the ingredients.
Pregnant, planning to become pregnant or breast-feeding.
Have recently taken alcohol, sleeping tablets, other strong pain killers or medicines to treat mental illness.
Have taken a monoamine oxidase inhibitor (MAOI) antidepressant within the last two weeks.
Have severe liver, kidney or lung (breathing) problems.
Suffer from epilepsy (fits) not controlled by treatment from your doctor.
Are undergoing treatment to withdraw from use of narcotics.
Cautions
Have been or are presently addicted to alcohol or any other drug.
Have epilepsy or suffered head injury or raised pressure in the skull (may cause painful eyes, changes in vision or headache behind the eyes). Have liver, kidney or lung (breathing) problems which are not severe. Are in shock following a severe injury or blood loss.
Are sensitive to opiates
Side effects
Contact your doctor at once if you experience:
- an allergic reaction: itching, skin rashes, swelling of the face, lips, tongue or throat, or difficulty breathing or swallowing, narrowing of airways, worsening of existing asthma, shock or collapse.
- slowed breathing - usually when high doses of Tramadol capsules are being taken or with other medicines that slow breathing.
- Very common (more than 1 in 10 users): dizziness, feeling sick.
- Common (less than 1 in 10 users): increased sweating, tiredness, drowsiness, sleepiness, headache, stomach ache, dry mouth, being sick, constipation.
Rare (less than 1 in 1000 users): extreme sense of wellbeing (euphoria), false sense of uneasiness (dysphoria), confusion, hallucinations (sensing things that are not real), altered mental state (delirium), changes in ability to think or sense clearly, sleeping problems (including nightmares), anxiety, ‘pins and needles’, tremor, muscle spasms, fits, fainting, blurred vision, slow heart beat, high blood pressure, changes in appetite, muscle weakness, difficulty urinating or inability to urinate.
Very rare (less than 1 in 10,000 users): flushing.
Not known (cannot be estimated from the available data): changes in liver enzyme levels (detected through blood tests), speech disorders.
Strong
Opiate drugs are comprise the majority of strong pain killing drugs. Opiate drugs are derived from the opium poppy, although a number available currently are synthetic in origin.
Opiate analgesia works by binding to the opiate receptors on the spinal cord and the brain to exert its effect. Its results in a dulling in the perception of the perception of pain by the brain.
There is considerable variability as to what the right do is for any person. But care should always be taken with dosing opiate in the elderly, the small and the physiologically unstable.
The main complication seen from opiate overdose is respiratory depression. Fortunately provided you have the ability to maintain an airway and potentially bag-mask the patient for a short period the respiratory depression is not in itself dangerous it can also be reversed using the drug naloxone (Narcan)
The problem with opiate drugs is they are additive and easily abused. The consequence is they are tightly controlled legally and have harsh penalties for illegal possession. Prescription access of small amounts, is still possible for those preparing, but it is likely for only those who have a close relationship with their MD or an ocean going boat !
Morphine
This is the class type drug. Synthesised from opium it provides a baseline to compare other agents against.
The standard adult dose is would usually be 2.5 – 5mg IV or 10-20mg orally with the precautions described above.
For long term care of severe pain subtract the patients age from 100 which will give the maximum dose that a normally fit person could tolerate over 24hrs in small divided doses as above
Oxycontin
There are a variety of synthetic opiate based drugs available. This drug is worthy of mention because it is so widely available. Oxycontin is a synthetic opiate taken orally which is used for moderate to strong pain. It requires a controlled drug prescription in most places, but is useful to be aware of due to its wide use and availability. The starting dose would be 5-10mgs.
Other medications
There are a number of other classes of agents used in the management of pain which only have a limited role in survival or wilderness medicine.
Entonox (P)A mix of 50% Oxygen and 50% nitrous oxide is both an analgesic and anaesthetic gas. Used in dentistry, child birth and emergency medicine. It is fast acting taking around 3-5 minutes to take effect and 5-10 minutes for maximum effect. It is self-administered and the patient must inhale deeply to operate the demand valve.
It can be delivered through a mouth piece or facemask and maximum effect is gained when the patient breathes in and out whilst keeping the mouthpiece or mask against or in the mouth.
When taken properly can be effective as opiates.
Exclusions
- Violently disturbed psychiatric patients.
- Severe head injuries with a changed level of consciousness.
- Anyone who has been diving within 24 hours as they may have decompression sickness which entonox will worsen.
Cautions
Penetrating torso injury, where a punctured lung or bowel is suspected.
Side effects
Euphoria, disorientation, sedation, nausea, vomiting, dizziness and generalised tingling are common and generally minor and rapidly reversible.
Alpha 2 adrenergic drugs
Used to treat hypertension have sedative properties used to treat pain and anxiety. clonidine and tizanidine. Side effects include fatigue and dry mouth.
Steroids
To relieve the pain of arthritis and treat breathing problems. Side effects can include diabetes, osteoporosis.
Antidepressants,
Elevates mood but also improves the physical functioning.
Tricyclic antidepressants (amitriptyline),
Selective serotonin reuptake inhibitors (fluoxetine).
Sleeping Pills and Muscle Relaxants
For pain stiffness and muscle spasm, mild sedative properties.
Carisoprodol, Methocarbomol and Diazepam.
Analgesic for neuropathic pain;
Opioids
Opioids are effective against all types of Pain
e.g. Morphine, codeine, fentanyl, meperidine, tramadol, pentazocine and propoxyphene
Side effects include addiction, respiratory depression and constipation.
Anticonvulsants
Designed for treatment of seizures but now also used for neuropathic pain.
carbamazepine, clonazepam, valproate, phenytoin, gabapentin, topiramate and lamotrigine
Local anaesthetics
Local anaesthetics given by mouth are useful for neuropathic pain. The most commonly used one is mexiletine which was originally used for heart rhythm abnormalities. Other drugs used are tocainide and flecanide.
Narcoleptics are drugs traditionally used for psychotic illnesses. Two drugs of this class olanzapine and resperidone are found useful to treat chronic pain.
Topical analgesics
These includes drugs like menthol, lignocaine, EMLA cream and capsaicin.
Lignocaine (lidocaine)
Notes
Lidocaine hydrochloride (lignocaine) Injection 1% (5ml Amp)
The dose used depends on the site of injection, the procedure used and the individual patient response. The lowest dosage needed to provide anaesthesia should be administered. Infiltrate a sufficient dose to ensure wound care can proceed without discomfort to the patient:
Percutaneous infiltration – dosing guidelines
Neonates – according to nature of procedure up to 3mg/kg (0.3mL/kg of 1% solutiom)
Child 1 month to 12 years- according to nature of procedure up to 3mg/kg (0.3ml/kg of 1% solution)
Child 12 to 18 years – according to nature of procedure up to maximum of 200mg
Adults: 0.5 -20ml of 1% solution up to maximum of 200 mg.
20ml of lidocaine 1% = 200mg lidocaine
Local anaesthesia agent by percutaneous infiltration for suturing/wound care
Explain Infiltration may be uncomfortable.
Advise on wound care and/or follow up for suture removal if appropriate.
Full sensation should return within 2 hours – avoid driving or handling machinery until full sensation returns.
Maximum 200mg for adults. For children depends on weight of child: up to 3mg/kg
Exclusion
Careful surveillance for toxic effect during first 30 minutes after injection. Resuscitation equipment should be immediately available. Lidocaine is contraindicated in patients with known hypersensitivity to local anaesthetics of the amide type, complete heart block and other conduction disturbances, hypovolaemia, acute porphyria.,
Cautions
Effect may be reduced if injected into inflamed or infected tissue. Use lower doses in the elderly, debilitated or acutely ill. Use with caution in patients with epilepsy, known severe liver or renal disease, severe respiratory depression, congestive heart failure, bradycardia or cardiac arrhythmias
Side effects
Allergic reactions (including anaphylaxis) have been reported rarely.
The following systemic reactions have been reported in association with lidocaine:
Central nervous system: fear, light-headedness, drowsiness, dizziness, confusion, twitching, tremor, feeling hot or cold or numb, convulsions, unconsciousness, respiratory depression and arrest.
Cardiovascular system: hypotension, cardiovascular collapse and bradycardia which may lead to cardiac arrest. Other side effects: blurred or double vision, nausea and vomiting, tinnitus
NMDA antagonists
NMDA receptors worsen pain. NMDA receptor antagonists therefore can relieve neuropathic pain. Some of the drugs of this class are methadone, dextromethorphan and ketamine.
