The IASP definition above relates to all types of pain. Duarte (1997) defines acute pain as temporarily related to injury and that resolves during the appropriate healing period. It often responds to treatment with analgesic medications and treatment of the precipitating cause. Characteristics may include the following:
- Duration is short lived - less than 3 months;
- Pain of varying intensity, initially severe then subsiding as healing takes place;
- Nervous system is usually intact;
- Reasons for pain can be pinpointed - pain is caused by trauma, surgery, acute medical conditions or a physiological process;
- Responds well to conventional analgesia - opioids, local anaesthetics, etc;
- Pain tends to subside as healing takes place;
- Psychological problems such as depression are short lived if present at all.
Acute pain is also known as nociceptive pain and can be divided into visceral and somatic pain.
RADIATING OR SPECIFIC
|Patient description||Pin prick, stabbing or sharp||Ache, pressure or sharp||Burning, pricking, tingling, electric shock or lancinating|
|Mechanism of Pain||A delta fibre activity located in the periphery||C fibre activity involving deeper innervation.||Dermatomal (peripheral) or non dermatomal (central)|
Periosteum, joints, muscle injury.
Colic and muscle spasm,
Sickle cell crisis, Appendicitis, Kidney stone
Post traumatic neuralgia,
HIV, Limb amputation, Herpetic Neuralgia
|Most responsive treatments||Cold packs, Tactile stimulation, Paracetamol, non steroidal anti-inflammatory drugs (NSAIDs), Opioids, Local Anaesthetic||NSAIDs , Opioid via any route, Intraspinal local anaesthetic, antispasmodic drugs, paracetamol||Anticonvulsants, Tricyclic antidepressants, Neural blockade|
Although acute or nociceptive pain is distinct from chronic pain, the boundaries are not well defined. Patients with acute pain usually experience resolution, whereas patients with chronic pain are unlikely to do so. Remember, that although acute pain has a foreseeable end it's management should be a high priority because acute pain may, when neglected, become chronic and persistent. While most patients experience nociceptive (pain that follows normal pain pathways), some may also experience neuropathic pain (nerve damage pain). Features in the pain history that may suggest this include , :
- clinical circumstances associated with a high risk of nerve injury eg thoracic or chest wall procedures, amputations or hernia repairs;
- pain descriptors as highlighted in the above table;
- the paroxysmal or spontaneous nature of the pain, which may have no clear precipitating factors;
- the presence of spontaneous or evoked unpleasant abnormal sensations (dysaesthesias),
- increased response to anormally painful stimulus (hyperalgesia),
- pain due to a stimulus that does not normally evoke pain (allodynia)
- areas of numbness (hypoaesthesia);
- changes in colour, temperature and sweating in the affected area and phantom phenomena.
Pain can also cause significant problems for the person experiencing it and delay postoperative recovery:
- Increased heart rate.
- Increased blood pressure.
- Increased stroke volume.
- Increased myocardial oxygen demands, reduced myocardial oxygen supply and possible myocardial ischaemia.
- Reduced blood flow to viscera and skin causing delayed wound healing
- Stimulation of respiration causing initial hypocapnia and respiratory alkalosis.
- Diaphragmatic splinting and hypoventilation, atelectasis, hypoxia and ensuing hypercapnia.
- Development of chest infection
- Catabolic and anabolic changes.
- Decrease in insulin production.
- Reduction in testosterone level.
- Fluid retention
- Raised blood sugar levels
- Delayed gastric emptying
- Reduced gastro-intestinal motility and ileus
- Increased blood viscosity
- Hypercoagulability and risk of deep vein thrombosis
- Psychological effects
The goal in postoperative pain management is to mobilize the person as early as possible, get them eating and drinking as early as appropriate and ensure they are able to cough and deep breathe. Therefore, if patients are not given good postoperative pain management they have an increased risk of chest infections, hypoxia and cardiac problems, pressure sores, deep vein thrombosis, depression, anxiety, anorexia, increased wound infection rates, etc.
Good postoperative pain relief has emerged through our understanding of how different drugs, when used in combination, have a synergistic effect which improves analgesia while reducing specifically opioid side effects of the drugs used. The concept of multimodal analgesia was introduced more than a decade ago and allows for a reduction in the doses of individual drugs when they are combined and hence the incidence of side effects is lowered. It has been shown that the benefits of multimodal analgesia techniques may provide for shorter hospitalization time, improved recovery and function (deep breathing, mobilisation, etc) ,  and possibly decreased healthcare costs.
Multimodal analgesia works because of the use of combinations of different analgesics that act by different mechanisms and at different sites in the nervous system, resulting in additive or synergistic analgesia with lowered adverse effects of sole administration of individual analgesics.
Postoperative pain management can be really effective if well planned, delivered in a consistent, evidence based manner and based on patients’ assessment of their own pain whenever possible. There are many factors that cause postoperative pain which means that no two patients, even if they are having the same operation, will experience the same pain and health professionals need to be aware of this. Pain is the 5th vital sign and robust protocols, team working and regular evaluation need to underpin postoperative pain management.
- Acute neuropathic pain: diagnosis and treatment.. Curr Opin Anaesthesiol, Curr Opin Anaesthesiol 21, 590-5., 2008.
- Symptom profiles differ in patients with neuropathic versus non-neuropathic pain.. J Pain, J Pain 8, 118-26., 2007.
- Effect of short-term postoperative celecoxib administration on patient outcome after outpatient laparoscopic surgery.. Can J Anaesth, Can J Anaesth 54, 342-8., 2007.