Pain

Definition:

An pleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage

Nociception

• Nonciceptive pain results from tissue damage causing continual nociceptor stimulation

• It may be either somatic or visceral in origin

Somatic pain

Somatic pain results from activation of nociceptors in cutaneous and deep tissue, such as bone.

It is well localized and described as aching, throbbing or gnawing.

Somatic pain usually sensitive to opioids.

Visceral pain

Visceral pain arises from internal organs.

It is vague in distribution and quality and is often as described as deep, dull or dragging.

It may be associated with nausea, vomiting and alteration in arterial pressure and heart rate.

Mechanism of visceral pain include abnormal distension or contraction of smooth muscle, stretching of the capsule of solid organs, hypoxia or necrosis and irritation by substances.

Visceral pain is often referred to cutaneous sites distant from the visceral lesion (like shoulder pain resulting from diaphragmatic irritation.

Etiology

1. Middle aged more than infant and elderly patients.

2. Neurotic personality.

3. Fear of pain

4. Site of operation like thorasic, upper abdominal and orthopedic being the most painful

Management

The management of pain is important not just for humanitarian also to improve and reduce postoperative complications.

Pain assessment: visual, verbal, numerical, Faces pain scale.

Routes of analgesic delivery

Oral:

• Simplest route available

• The bioavailability is limited to 1st pass metabolism

• The oral route is not suggested following major surgery due to potential delays in gastric emptying

Intermittent subcutaneous or intramuscular injection

Advantages:

• Safe if it administered more regularly

• Familiar practice

• Gradual onset of side-effects

• Inexpensive.

Disadvantages:

• Fixed dose not related to pharmacovariability

• Painful injections

• Fluctuating plasma concentration

• Delayed onset of analgesia

Intravenous bolus

• For the management of severe acute pain.

• It gives the quickest onset and repeated doses can be titrated against effect.

• Close supervision of the patient is required.

• This method is not appropriate for continuing pain management at ward level

Intra nasal bolus

• Efficacy and speed of action are similar to that I.M.

• It offers an alternative method of administration for areas such as emergency department and pediatric units

Continuous intravenous infusion

Advantages:

• Rapid onset of analgesia

• Steady-state plasma concentrations

• Painless

• Pain control may be superior to PCA spc. For major surgery

Disadvantages:

• Fixed dose not related to pharmacodynamic variability

• Errors may be fatal

• Expensive fail-safe equipment required

• Close monitoring of the patient is important to detect respiratory depression or over-sedation

Patient-controlled analgesia (PCA)

• Intravenous PCA is now a standard method of providing postoperative analgesia in many hospital worldwide

• PCA can give high-quality analgesia but can fail if not applied appropriately

• PCA can be used for most surgery where moderate to severe postoperatively pain is expected

• With PCA the patient determines the rate of i.v. administration of the drug thereby providing feedback control.

• PCA equipment comprises an accurate source of infusion, coupled to an i.v. cannula and controlled by patient-machine interface device. Safety features are incorporated to limit the preset dose, the number of doses which may be administered and the lock out period between doses. The drug that has been most commonly used with PCA is morphine

Advantages:

• Dose matches patient’s requirements and therefore compensates for pharmacodynamic variability

• Doses given are small and therefore fluctuations in plasma concentrations are reduced

• Reduces nurses’ workload

• painless

Disadvantages:

• Technical errors may be fatal

• Expensive equipment

• Requires ability to cooperate and understand

Epidural

• Its superior to i.v. PCA for the management of pain following major abdominal surgery and lower limb amputation

• Its safe to use at ward level, but this dependent on adequate monitoring and on nursing staff who have received specific training in caring for patient with epidural infusions

• Used mainly for the management of pain during child birth and following major abdominal, thoracic orthopedic and vascular surgery

• Opioids exhibit 10 times the potency when administered via the epidural route as opposed to the intravenous route

• A combination of local anesthetic and opioid is usually administered the two drugs act synergistically resulting in superior analgesia and improved side effect profile

Contraindication to epidural:1. Anticoagulation or coagulopathy2. Hypovolemia3. Local infection, septicemia4. Lack of patient consent

In addition to its analgesic effects, the utilization of epidural analgesia may decrease the incidence of DVT following orthopedic surgery and improve circulation following vascular surgery

Thank You