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Free «Pathophysiology of Pain» Essay Sample


This paper investigates the rationale behind the use of an epidural infusion for pain relief in post-surgery period. It also examines the pathophysiology of pain, major complications manifested by pain in post-operative patients and the benefits and risks of epidural infusion analgesia while managing pain.

 This paper also gives Hernandez’s (2006), Waskett-Booth’s (2007), Vanderah’s (2007), Carre’s (2005) and Block’s (2003) opinion on the topic researched.

Keywords: pain, pain relief, epidural analgesthesia, vein thrombosis, pulmonary embolus, motor block, haematoma, postdural puncture headache, urinary retention.


Considerable pain relief is crucial for overall emotional and psychological well-being: it lessens the anguish of body and mind, and helps the patient to recuperate more quickly from the operation. There are many different procedures that help to relive the pain. The right one anaesthetist needs to discuss with the patient before the surgery.

Epidural analgesthesia is the greatest way of managing post-operative pain relief in patients undergoing surgical treatment. 27 years old Mr. Johnson had a left pneumonectomy after being diagnosed with primary lung adenocarcinoma. He has no past history and has been a non-smoker. He has an intravenous cannula put with normal saline 18/24, an indwelling catheter, and an epidural with Marcain 0.125% with Adrenaline at 5ML/hr. his vital signs are as follows: Bp 110/70 mmHg, HR, 62 regular, RR 12, core Temperature 36.2. He is awake and alert and has pain score 3/10 with movement. Sometime later Mr. Johnson blood pressure drop to 85/50 mmHg. He feels warm to touch, his skin is dry and his core temperature is 36.5. The following morning Mr. Johnson complains of headache and his respiratory rate is 26 and shallow.

This essay will discuss the benefit of using epidural infusion to control Mr. Johnson pain post-surgery, pathphysiology of pain, the complications manifested by of pain in the post-operative patient and the risk and benefits of epidural analgesia to manage pain. Also, It will discuss the seven priorities nursing care for Mr. Johnson and risk of hypotension and dural puncture headache and nursing care to alleviate these complications.

Rational behind use of an epidural infusion for pain relief in post-operative

Epidural analgesia is applied to cope with the pain of those patients, who are undergoing many various types of surgical procedures, such as thoracic, abdominal, orthopedic, and vascular surgery. Mr. Johnston has been taking epidural analgesia, Marcaine 0.125% with Adrenaline at 5ml/hr which offers trustworthy, slowly effective, site-directed pain supervision with small doses of medicaments and diminishes unacceptable risks of post-operative complications (Hernandez, 2006).

In addition, epidural injections reduce the patients’ general opioid requirements while making available more unfailing pain management. Due to the fact that epidural analgesia enhances the pain management in general, it permits the patients to become movable and acting earlier, cough easier, and breathe better (Roman, & Cabaj, 2005).

Epidural infusion analgesia is extremely successful in monitoring and directing serious severe pain after the surgery. The combination of exceptional pain relief and slight side effects presents high patient contentment compared to other methods of reliving pain (Hernandez, 2006). Local analgesia affects the pain receptor and blockades its pathway. Usually, an epidural infusion is dispersed through the dura mater, enters the spinal fluid where spreads rostrally and is totally soaked up by the arteries supplying the spinal horn and acts straightly at the opioid receptors in the dorsal horn of the spinal cord (Waskett-Booth, 2007).

Pathophysiology of pain

The phenomenon of pain is usually explained as a disagreeable sensory (physical or emotional) experience, accompanied with a serious actual or potential tissue injury (Evans, 2010). The feeling of pain is a neural-biochemical effect. As soon as a serious flesh, skin or/and muscle damage occurs, neurochemical response at the site of wound activates the free nerve endings of the special nerves called ‘nociceptors’. Those nerves cause an afferent nerve impulse to spread throughout the peripheral nerve, access the spinal cord, and synapse with higher order neurons. This neurochemical push later crosses specific ascending spinal tracts, arriving at cerebral centers for interpretation.

Variations of the afferent information can take place in many parts of human body, including the cerebral cortex, periphery, midbrain and spinal cord. Interpretation of this impulse yields a reply signal, moving through definite descending spinal tracks and out through peripheral motor nerves. That systematic series of chemical actions is a result of the postponement in feeling a pain sensation after suffering a serious damage. Pain sensations can be classified in a variety of ways, grounded on their moving speed in the nervous system (fast / slow pain), the time interval the pain has lasted (acute / chronic) and the anatomical aetiology of the sensations (somatic / visceral) (Vanderah, 2007).

Complications manifested by pain in post-operative patient

Post-operative pain can influence the patient both physiologically and psychologically.  Such effects might lead to complications (such as rises in heart rate and blood pressure, late stomach emptying and nausea, vomiting and deep changes in the endocrine system due to the multiplied adrenaline production) and late discharge. Due to the badly controlled pain, the failure to cough well and deep breathe may result in chest infections’ development, delays in mobility and other complications, such as serious vein thrombosis or pulmonary embolus (Macintyre and Ready 2002). Psychological problems, for example increased anxiety levels, sleep disorders, disquiet, impatience, petulance, anger and, most importantly, high levels of anguish and suffering (Carre et al 2005).

The benefits and risk of epidural infusion analgesia to manage pain

The main advantage of epidural infusion analgesia managing pain, in comparison to other pain-relief methods, is ameliorating instantaneous pain relief. Easing such post-surgery complications as pulmonary embolism, deep vein thrombosis, nausea, vomiting and chest infection and delayed intestine function can offer an earlier eating/drinking resumption and even full movement, possibly, with an earlier discharge from the hospital (Block, et al 2003).

On the other hand, there is a number of side-effects of the epidural infusion analgesia, such as:

  • Hypotension. It is the most common side-effect that is a result of the local anaesthetic’s influence upon the sympathetic nerves. This causes the relaxation of smooth muscle, leading to the loss of vascular tone and consequent vasodilatation. 1.34% of patients are suffering from hypotension during the epidural infusion (Christie, & Mc Cabe, 2007).
  • Motor block is another possible problem of epidural analgesia as it affects the sensory, sympathetic and motor nerves. However, they affect small bore nerves first, thereby blocking sensory and sympathetic nerves in preference to the larger bore motor nerves. 13.4% of patient going under epidural analgesia have motor block.
  • Ineffective pain control is another serious complication of epidural analgesia and 2.4% of patients experience it after the infusion (Anonymous, 2009).
  • Respiratory depression is one more negative side-effect of the epidural analgesia. Sometimes, such respiratory depression rate can be a late and often unreliable sign of analgesia overdose.
  • Epidural haematoma is another complication of epidural analgesia. There is 1 in 100000 chance of the haematoma to occur. For example, bleeding in the epidural space can lead to a haematoma large enough to cause compression of the spinal cord (Christie, & Mc Cabe, 2007). Also, epidural abscess or infection may present the same signs as a haematoma with possible addition of pyrexia, which usually develops over first two or three days.
  • Postdural puncture headache might also occur after the epidural analgesia. Very often it happens with those, who endure dural puncture with a fine pencil-point spinal needle. Such ache is usually postural and results from cerebrospinal fluid escape with the attendant decrease in intracranial pressure and compensatory cerebral vasodilatation (Ghaleb, Khorasani, & Mangar, 2012).
  • Urinary retention is one more complication of epidural analgesia and 0.4 % of patients experience it. Local anaesthetic can also affect the nerve supply to the bladder, causing the patient to retain urine. This is more common when the epidural catheter is placed in the lumbar region. Most patients return from surgery with an urinary catheter (Weetman, & Allison, 2006).

The seven priorities nursing care for patient with epidural infusion (this patient)

The patient with epidural infusion analgesia needs an appropriate nursing care to prevent post-operative complications. It is necessary to observe those patients in order to prevent health problems associated with the infusion of local anaesthetics, to make sure that the patient has sufficient analgesia, to recognize all possible changes in the patient’s condition and ensure that only an appropriate intervention occurs. Respiratory rate and sedation score are the most frequently monitored parameters. Other parameters monitored may include: blood pressure and heart rate, pain scores and oxygen saturation, motor block and catheter site, infusion and infusion pump readings, urine output.

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In the majority of cases all parameters mentioned above are monitored hourly for the first 12 hours and then no less than 4 times per every 24 hours. Observing Mr. Johnston blood pressure and heart rate is very important as he may have hypotension and bradycardia as a result of sympathetic blockade associated with epidural infusion, surgical bleeding and/or hypovolaemia. (Rowbotham, Cashman, & Counsell, et all, 2010). Monitoring respiratory rate is vital, because it could be affected by medications as one of the side-effects of epidural analgesia respiratory depression. Moreover, Mr. Johnson has pneumonectomy which increases his risk of pulmonary dysfunction (Duarte, Fernandes, Maria, Carvalho, Costa, & Saraiva, 2009). Monitoring sedation score is important because there is always a high risk of sedation due to the medication used. Pulse oximetry assists the assessment of respiratory function, so that the oxygen can be delivered accordingly.  Checking Mr. Johnson’s temperature is imperative, as fever may indicate that the infection was caught. In addition, Mr. Johnson havs indwelling catheter and epidural catheter which increase his risk of infection (Rowbotham, Cashman, & Counsell, et all, 2010).

The process of monitoring pain levels at rest and while moving/breathing, and sedation rates are another priority of nursing care for Mr. Johnson, who is under epidural analgesia. Felling pain is a vivid sign of inadequate or excessive epidural drug administration. After epidural analgesia admitted, 5% of patients feel pain which is called block failure, while another 15% experience partial relief (Shafiq, Hamid, & Samad, 2010). Monitoring sensory and motor blocks is vital as all potentially serious complications can be detected early enough. An increasing degree of motor weakness implies excessive epidural drug dose, dural penetration of the catheter, or the development of either an epidural haematoma or abscess. Motor block produces paralysis of the lower limbs which is quite stressful and worrying for the patient. (Shafiq, Hamid, & Samad, 2010). Urine production should be measured and noted in the fluid balance chart. Almost 100% of post-operational patients may experience urinary retention, which relates to dermatomal level of the epidural block, epidural medication, and surgical procedure. In such cases a catheter should be inserted to avoid urine retention after the surgery (Ladak, Katznelson, Muscat, Sawhney, Beattie, & O'Leary, 2009).

The epidural infusion data should be recorded and checked every 2 hours and must include: rate of infusion, volume infused and volume remaining in the bag to avoid epidural analgesia toxicity or pain result from inadequate analgesia (NPSA 2007). The epidural catheter site must be regularly checked to ensure that the catheter is firmly fixed and there is no leakage, catheter dislodgement or local infection (Daykin and Cox 2003). Epidural catheters and infusions must be labeled ‘FOR EPIDURAL USE ONLY’ and easily distinguished from any other by the use of yellow labels. Not labeled infusion administration sets may be used epidurally and intravenously, and can be connected to the wrong route of administration or to the incorrect infusion bag or syringe (NPSA 2007).

Nursing care to alleviate hypotension complication associated with epidural infusion (same patient)

Undoubtedly, Mr. Johnson may be exposed to the risk of hypotension as a result of epidural analgesia. Significantly low blood pressure is a major problem of epidural anesthesia. A sympathetic blockade is the most common cause of the enlargement of the veins/venules and capillary blood flow, and loosing of the arteries tension. The lessening in venous return to the heart may result in smaller cardiac output. The level of hypotension changes according to the  level of sympathetic block, the volume status of the patient and his/her position. The study found that, 1.34% of patients are suffering from hypotension during epidural infusion (Macintyre, Scott, Schug, Visser, Walker, 2010).

Hypovolemic might be caused by hypotension as a result of internal bleeding. Patient with hypotension needs immediate nurse care to alleviate this problem because it can lead to cardiac arrest. Lay patient flat in bed and elevate legs on pillows to increase venous return to the heart, increase cardiac output and increase blood pressure. Informing the pain management service and the anaesthetist involved with the patient is the most vital procedure. Check fluid balance and look for signs of dehydration such as dry tongue and lips and dark colored urine. Administer intravenous fluid such as gelofusine to replace circulating volume. Record blood pressure every 5 minutes to monitor any change and the response. To prevent dehydration, epidural infusion rate may need to be reduced or stopped, if the patients urine output has dropped to below 30mls/hr (Chumbley, & Thomas, 2010).

Nursing care to alleviate dural puncture headache complication associated with epidural infusion (same patient)

Dural puncture is one of the main complications of epidural infusion. Mr. Johnson is at risk as he is complaining about a headache, which is caused by dural puncture. An unintentional puncture of the dura by an epidural needle or an intentional puncture with a spinal needle can lead to a leakage of cerebrospinal fluid (CSF). The drop in cerebrospinal fluid pressure and tension on the meningeal vessels and nerves leads to a post-dural puncture headache (PDPH). It occurs in 0.4 - 6.0% of the patients.

Due to large associated cerebrospinal fluid leak, a large number of patients (up to 86%) suffer post-dural puncture headache, which is enormously severe in nature (Jadon, Chakraborty,  Sinha, & Agrawal, 2009). Headache post epidural infusion needs to be investigated and given care to alleviate it. Nurse should ascertain the nature of the headache to be treated. Any previous history such as migraine cannot be excluded, because it can be a possible cause of the headache. Call the Anaesthetist and the pain management service if the problem persists. Attempt a darkened area and keep out sunlight. Give simple analgesia such as paracetamol. If headache did not resolve, an anaesthetist perform epidural blood patch. When a patch is used in patients suffering from moderate to severe or prolonged PDPH a success rate of 96% to 98% can be expected. Two mechanisms are likely bring about this effect: formation of a plug in the dural defect, which stops the loss of CSF, and simultaneous reduction in the volume of the subarachnoid space through expansion of the epidural space, which eliminates the relative CSF deficiency. Also, abdominal binder to increase epidural pressure to prevent leakage of CSF and analgesics is important (Crawford, 2007).


Epidural analgesia is commonly used to cope with severe pain in a post-surgery period as it effectively reduces the risk of unfavorable outcomes. Yet, it has a number of complications such as hypotension, dural puncture headache, urinary retention, epidural haematoma, respiratory depression, motor block and other. The major role of the nurse is to carefully monitor the patients and respond to any occurring concerns. 


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