ACUTE POST OPERATIVE PAIN

ISSUE2006; : PAIN50 (5) : 340 - 344 340 Indian J.PG Anaesth. INDIAN JOURNAL OF ANAESTHESIA, OCTOBER 2006 340 ACUTE POST OPERATIVE PAIN Dr. Manimala ...
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ISSUE2006; : PAIN50 (5) : 340 - 344 340 Indian J.PG Anaesth.

INDIAN JOURNAL OF ANAESTHESIA, OCTOBER 2006 340

ACUTE POST OPERATIVE PAIN Dr. Manimala Rao Keywords : Acute, Post Operative, Pain. Introduction The relief of pain has been one of the primary reasons for development of health care. Acute pain management came into force as a speciality in 1988 in Seattle where Brain Ready published his concept of acute pain services.1 Later in 1990 with joint colleges’ report that recommended the setting up of acute pain services at all hospitals. Acute pain teams are widespread in US, Australia and Europe. The decade has been denoted as decade of pain management and research. Pain has been introduced as the fifth vital sign by Joint commission on health care organization (JCAHO). They have published the standards for pain management in hospital setting in 2001.2,3 Pain is omnipresent, is an intolerable sensation and makes the patient vulnerable. There is a saying that there is no gain with out pain. This may not be true in the acute postoperative pain. It is well documented that pain inadequately relieved is deleterious and can lead to a number of complications in the post operative period Therefore the pain of surgery must be relieved totally. Acute pain services (APS) Despite good understanding of its patho-physiology and awareness regarding the beneficial effects of pain relief in the post op period, many patients do not receive adequate analgesia. This problem is international in character. Patient controlled analgesia spinal opioids regional analgesic techniques have provided better pain relief than intermittent injections of opioids. Such of the above techniques require special monitoring. Therefore one may require an organization which will provide education and policies that permit physicians and nurses to care safely for the patients. Number of times national guidelines have been published in several countries but the impact of these guidelines on the patient care was not clear. The key recommendation was to introduce APS. The principle obstacles were financial constrains and under educations of physicians regarding its management.4 Similar problems were envisaged in many countries.5 Further APS using a multi disciplinary team approach received a wide spread Professor Emeritus & Head of Anaesthesiology and Critical Care Yashoda Hospital, Somaji Guda, Hyderabad (Formerly Prof & Head NIMS Hydarabad) E-mail : [email protected]

acceptance and financial support from the institutions and organizations from many countries. The key recommendations of United Kingdom working party are as follows. 1)

Need for education and training and changing the attitudes as well as provide adequate funding.

2)

Systematic record of pain as the 5th vital sign.

3)

A named member of staff should be responsible for the hospital policy toward post operative analgesia audit and appraisal.

4)

All major hospitals per forming surgery should implement APS with a team approach, with a physician, nurse, pharmacist and psychological expertise. Anaesthesiologist has the primary key role.

5)

There is need for powerful but safe analgesics and long acting nontoxic local anaesthetics.

With advent of APS the Anaesthesiologists are offering new and powerful analgesia. However the bed side nurses have to be trained and be responsible to deliver the analgesics and monitor their adverse effects. The nurse or the anaesthesia technician can be trained in this area in our country. The protocols should be simple and could be modified when necessary. Anaesthesiologists play a pivotal role in acute pain services. APS is still not a very well organized in our country, even though the anaethesiologist takes care of post operative pain relief in major surgical procedures as well as takes care of the surgical ICUs. It has to go a long way to educate, train and implement APS in all major hospitals. Importance of post operative pain management and mechanisims The relief of pain has been one of the primary reasons for development of health care, yet physicians often do not understand the meaning of the complaint of pain or how effectively they can assist the patient to regain control over his or her life. Anesthesiologists should understand the various concepts in generation of pain and not allow their technological skills only to govern all their interactions with pain. Although treatment of pain for its own sake is considered a worthy’ duty’ in medicine, it has not been vigorously pursued as it should have been. One of the reasons for the invention of hypodermic syringe in

MANIMALA : ACUTE POST OPERATIVE PAIN

1840 was to deliver the analgesics Alexander Wood produced relief of pain but perhaps not by’ morphine conduction block but by systemic use. Pain derived from Latin word Poena means ‘punishment’. It has been defined with acute or potential danger or described in terms of such danger very aptly by International Association for study of pain. Understanding of pain is very important. It should be viewed form 4 points. They are nociception, pain, suffering and pain behaviour. The acute pain has meaning and the underlying pathophysiology is obvious. Postoperative pain forms one of the categories of acute pain. Anesthesiologists focus their attention on the abolition of postoperative pain. It would be nice if anaesthesiologists worried a bit more about patients’ pain after his/her departure from the operating theatre. This has led in many countries to manage acute pain services by anaesthesiology team. A redefinition of the role of anaesthesiologists, dedicated to manage the acute pain of surgery will bring tremendous improvement in health care delivery in the pain management services which ultimately leads to patient satisfaction and reduces the dread of surgical procedures. Surgery activates the stress response post op pain also has somewhat the same but not an identical effect. Both are modified by nerve blocks and central neuraxial blocks like the spinal and epidural anesthesia. It is now well recognized that prolonged insult to the body produces changes in the nervous system, which alter the normal physiological response to a noxious stimulus. Therefore pain is divided into two entities, physiological and pathophysiological or clinical. The process underlying both are totally different. Physiological pain describes the situation where a noxious stimulus activates peripheral receptors, which transmit the information via several relays until it reaches the brain and is recognized as harmful stimulus. This entity can also be often referred as incissional pain. The latest development is ON Q systems are simple pumps which can deliver non narcotic medication at the incision site with a multi lumen catheters inserted by the surgeon at the time of surgery. They target the specific area and prevent the sensitization of the receptors to nociception. They deliver the set concentrations of local anaesthetic solutions to the specified area. The factors responsible for development of clinical pain will result in a stimulus response system that has quite different characteristics from those of physiological pain. Inflammation or nerve damage gives rise to changes in sensory processing at peripheral and central level with a resultant sensitization. Once sensitization occurs the

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stimulus, which normally do not produce pain, are perceived as painful (allodynia) and there is an exaggerated response to painful stimulus (hyperalgesia).

Fig. 1 : Physiological pain

Low intensity stimulus

Sensitized nocioceptor A delta & C

Low threshold Mechanoreceptor A beta

PNS

CNS

Hyperexcitable dorsal horn neuron

PAIN

Fig. 2 : Clinical pain

Surgery in particular, produces biphasic insult on human body, which has implications for pain management. First of all, during surgery there is trauma to tissue, which produces noxious stimuli and great nociceptive input. Secondly, after surgery there is inflammatory process at the site, which is also responsible for noxious input. Both these processes sensitize the pain pathways. They occur at peripheral level where there is a reduction in threshold of nocioceptive afferents and at a central level with an increase in excitation of spinal neurons involved in pain transmission. It has profound implication for management of acute pain and provoked interest in the use of preemptive analgesics and new methods of postoperative pain management with new agents of non-opioid type and in combination with opioid drugs. Peripheral sensitization can be with different stimuli, VIZ., thermal, tactile, mechanical, chemical and their first relay is in the dorsal horn. In clinical situation this noxious

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stimuli is prolonged resulting in tissue damage and inflammation. This leads to release of a ‘soup’ of inflammatory mediators such as K, serotonin, bradykinin substance P, histamine etc. These substances act to sensitize high threshold nociceptors. As the low threshold stimuli, which would not normally cause pain, are now perceived as painful.6 If one would like to reduce peripheral sensitization rational approach is to prevent or reduce the inflammatory ‘soup’, use of NSAIDS and peripherally acting drugs, combination of opioids, local anaesthetic drugs. Inflammatory response is part of complex injury. Therefore, sensible modification of the injury response becomes part of the strategy for pain management and acute rehabilitation. Studies are confirming that such strategies reduce pain, post surgical catabolism and early discharge from hospital. Tissue damage

Inflammation

Sympathetic terminals

SENSITIZING SOUP

Hydrogen ions Noradrenaline Bradykinin

Histamine Purines Potassium ions Cytokines Prostaglandins 5-HT

Leucotrienes Nerve growth factor Neuropeptides

High threshold nocioceptor Transduction sensitivity Low threshold nocioceptor Fig. 3 :Peripheral sensitization

Central sensitization - Recent research has focused on dorsal mechanisms. Following injury, there is an increased response to normally innocuous mechanical stimuli (allodynia) and a zone of secondary hyperalgesia in uninjured tissue surrounding the site of injury. It is now known that a secondary ‘C’ fibre barrage in primary afferent fibres leads to other morphological and biochemical changes in dorsal horn which may be difficult to reverse. Firstly, there could be expansion in receptor field size Secondly, there is an increase in the magnitude and duration of response to stimuli and finally there is a reduction in threshold, so that stimuli, which are not normally noxious, activate neurons, which usually transmit nociceptive information. It appears, NMDA receptor may mediate responses in the physiological processing of sensory information, and is involved in central sensitization.7 Ketamine, which is NMDA receptor antagonist, has profound analgesia. Nitric Oxide(NO) has a role in nociceptive processing. NO is produced secondary to NMDA receptor activation. Drugs, which may prevent production or block, may have a role for reducing or abolishing pain.

Nocioceptor input Activity-dependent increase in excitability of dorsal horn neurons Low threshold Mechanoreceptors (A beta fibres)

Modified responsiveness PAIN (Mechanical allodynia)

Fig. 4 : Central Sensitization

(Figures are from Woolf CJ, Chong MS Anesth Analg 1993, 77: 362-379) There are basically two approaches, one is to investigate the agents, which act at spinal level on opioid, a adrenoreceptors and NMDA receptors, and the other is to prevent central sensitization. The concept of preemptive analgesia has arisen as a result of these findings, to minimize or prevent these changes. Preemptive analgesia - while the concept of peripheral sensitization has been well recognized, the central sensitization component after surgery, despite convincing animal data, failed to suggest it following surgery. Simple analgesics such as morphine or nitrous oxide, given to patients prior to surgery, may not act preemptively and prevent significant central sensitization. Nerve blocks and regional techniques may to certain extent modify the sensitization. Balanced analgesia has evolved under the direction of Kehlet and Dahl. They propose that pain free state should be utilized to the patients advantage with aggressive regime of post operative mobilisation and early enteral feeding. This may reduce deep vein thrombosis and amount of protein wasting and making the patient more anabolic.8 Wound infiltration and nerve blocks - Local anaesthetics reduce nociceptive pain at the site of operation and also attenuate central sensitization. Nerve block provided slightly superior analgesia, the later covers entire area whereas infiltration may have the advantage of blocking the peripheral sensitization. Despite the advantages one must also keep the risks associated. Infection used to be the most important concern. With the advent of ON Q systems which have been used in post cardiac surgical patients as well as in many other surgical procedures of herniorraphy and breast surgery. Specialized pumps deliver non narcotic local anesthetics at the area of incision, giving the medication where it is needed. Specially designed catheters and simple pumps which can be clipped on to the clothing are a novel

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way to provide the post operative pain relief. The benefits are reduced dosage of narcotics and their associated complications.9 Non pharmocological methods Though pharmacotherapy forms an integral part of management of acute pain, one has to look at various other methodologies to relieve post operative pain The non pharmacological methods can be used as adjuvants to the main method of pain relief. A holistic approach can cut down costs and reduce the complications associated with the opioid and non opioid drug usage and dosage. A combination of pharmacotherapy and patient education in the pre operative period may go a long way in treating acute pain after surgery. lot of interest in complimentary and alternative medicine (CAM) for chronic pain management is in vogue which could be applied for acute pain. With work on stress response system, a system integrating body and mind has evolved is also goes by the name of psycho neuro immunology.10 Disease is created when there is discrepancy between autonomic and endocrine systems, resulting in inappropriate fight and flight reactions. Treatment focuses on balancing the sympathetic overdrive by using body and mind techniques viz. Bio feed back & Hypnosis These techniques can be counter balancing the Meditation and Yoga relaxation response. But every thing can never be explained on the CAM technique.

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Hypnosis Is a mind body technique creates focused attention. It is self hypnosis where therapist functions as a guide to help patient to focus attention as well as filter out unpleasant, and negative sensation and receive positive sensation. Currant research shows it is not a passive withdrawl of awareness but rather an active suppression of somato sensory cortex by frontal cortex.13 Anecdotal reports abound but growing scientific literature on the role of suggestion in preparing for surgery there by reducing the post op pain.14 Homeopathy Symptom is Considered as positive sign throwing off the disease state. It has proved to be effective in allergy and asthma, but not so effective in acute pain. Argument against is that the methodology employed was not effective.15,16 Therapeutic touch IT is a nursing technique based on purported human energy field that surround the body as magnetic field surround a magnet. It involves three steps. First the nurse positions and observes, second detects any abnormal movement, third corrects them. By non contact movements of the hands over the affected area. It has resemblance to an ancient technique used in China and Europe for many years. It has shown to relieve phantom limb pain.17 More work is required to validate this form of energy.

Cognitive dysfunction Occurs in 10-15% of patients in the post op period. More common in the elderly alcoholics electrolyte imbalance and usage of benzodiazipine and Pethidine were also implicated. High levels of post op pain can cause delerium and vice versa. It can impair cognition and worsen the pain.

Meditation In many ancient cultures meditation could voluntarily stop the heart, bring down the respiratory rate, prolong suspended animation and relieve pain completely. Modern research has also indicated that it is useful in chronic pain. As against the common belief it does not require years of training. Simple techniques like closing the eyes and concentrating on breathing and slowly coming back to reality is an useful tool which can be practiced before surgery and would be useful to reduce the dose of pain medications in the post operative period. Could be included in the holistic approach in CAM therapy along with usage of conventional methods of pain relief.

Herbal medicine Many of the pain medications are derived from plant extractions and are purified alkaloids. Modern pain relieving extract from chlli pepper (capsicum) is commonly used. The active ingredient in zofran crème is capsaician which depletes substance P from nerve terminals. Is beneficial in amputation phantom limb pain, and post mastectomy syndrome.11,12

Tens in acute post op pain It is accepted that use of TENS either at acu point or dermatome corresponding to surgical incision decrease the post op pain, opioid requirement, and related side effects. The effect of frequency of electrical stimulation was studied in 100 women undergoing gynecological surgeries. Post op pain was controlled with patient controlled analgesia with morphine, and sham tens without

Common cam techniques for post op pain Herbal medicine, Hypnosis, Homeopathy, Therapeutic touch, Meditation, Trans cutaneous nerve stimulation (TENS), Acupuncture, Heat application are a few to name.

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stimulation in one group, 2Hz, 10Hz, and mixed 2 and 10 Hz respectively. The last group showed better pain relief and 53% decrease in morphine requirement, as well as reduced itching nausea and vomiting.18 Acupuncture Derived from Greek word Acus means needle and punctura means puncture. This method was practiced in the 5th century B.C in China. The basic theory is that of Yin and yang balance opposing influences in nature. The evidence of release of endogenous peptide with AP and EP derives from seminal work done by Pomeranz.19 Opiod receptor antagonism has shown to abolish the analgesic effects of acupuncture. The fascination for this ancient medical modality increased when one of the press Corps from presidents Nixon’s troupe received it for appendectomy. IT can be used like TENS in reducing the requirement of medications.

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3.

4.

5.

6. 7.

8.

CAM interventions have become more and more acceptable in public. Though one does not have a very clear cut idea about the mode of action, one can never turn the back on these methods They may form part of holistic approach to pain management in the acute post op pain in future, as they are already a part of chronic pain management. More research and funding is being relegated to this aspect, in view of public interest. In future it may potentially transform the way pain management is practiced even in the acute setting.

9.

Inspite of great interest in understanding the pain mechanisms and pain management, number of patients still suffer unacceptable pain even today. Surveys show that there is not much improvements in this area. So it is quite clear that the solution to post operative pain is not just developing a single technique.

12.

Or a drug to relieve it but to implement simple protocols that suit in different settings with strategies to exploit the available expertise. Anaesthesiologists with their expertise not only in understanding the pathophysiology, but coupled with their technical and technological expertise could with commitment make it safe as well as comfortable to the individual patient needs. They could inturn play a pivotal role in organize and manage pain sevices to the entire hospital. References 1. Ready LB, Oden R, Chadwick S et al. Development of an anaesthesiology based acute pain service. Anesthesiology 1988; 68: 100-106. 2. Acute Pain Management Guidelines Panel. Acute Pain Management: Operative or Medical Procedures and Trauma. Clinical Practice Guideline. Rockville, Md: US Dept of Health

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and Human Services, Agency for Health Care Policy and Research; 1992. AHCPR publication 92-0032. Practice Guidelines for Acute Pain Management in the Perioperative Setting. ASA Task Force on Pain Management. Anesthesiology 1995; 82: 1071. Gould TH, Crosby DL, Harmer M et al. Policy for controlling pain after surgery: Effect of sequential changes in management. BMJ 1992; 305: 1165-1166. Rawal N, Allvin R. Euro Pain Acute Pain Working Party: Acute pain services in Europe: A 17-nation survey of 105 hospitals. Eur J Anaesth 1998; 15: 354-363. Woolf CJ. Recent advances in pathophysiology of acute pain Brit J Anaesth 1989; 63; 139-146. Woolf CJ, Thompson WN. The induction and maintenance of central sensitization is dependent on N-Methyl D aspartic and receptor activation indication for the treatment of post injury pain hypersensitivity states Pain 1991: 44; 293-299. Kehlet H, Dahl JB. Post operative pain (review) World J Surg 1993; 17: 215-219. Sanchez B, Waxman K, Tatevossean R et al. Local anesthetic infusion pumps to improve post operative inguinal hernia repair a randomized trial Am Surg 2004; 70(11): 1002-6. Eric L. Complimentary and alternative pain management in Minding the Body, Mending the mind : The New Science of Mind/Body Medicine by Borysenko J. New York, NY: Time Warner Books; 1987. Schmid G, Carita F, Bonanno G, Raiteri M. NK-3 receptors mediate enhancement of substance P release from capsaicinsensitive spinal cord afferent terminals. Br J Pharmacol 1998; 125: 621-626. Haustkappe M, Roizen M, Toledano A et al. Review of the effectiveness of capsaicin for painful cutaneous disorders and neural dysfunction. Clin J Pain 1998; 14: 97-106. Spiegel D, Barabasz A. Effects of hypnotic instructions of P300 event related-potential amplitudes :research and clinical applications. Am J Clin Hypn 1988; 31(1): 11-17. Enqvist B, von Konow L, Bystedt T. Pre and perioperative suggestion in maxillofacial surgery: effects on blood loss and recovery. Int J Clin Exp Hypn 1995; 43: 284-294. Hart O, Mullee MA, Lewith G et al. Double-blind, placebocontrolled, randomized clinical trial of homoeopathic arnica 30c for pain and infection after total abdominal hysterectomy. J Roy Soc Med 1997; 90: 239-240. Whitmarsh T. Evidence in complementary and alternative therapies: lessons from clinical trials of homeopathy in headache. Jaltern Complement Med 1997; 3: 307-310.

17. Leskowitz E. Phantom limb pain: subtle energy perspectives. Subtle Energy Med 1998; 7(4): 1-27. 18. Hamza Ahmed, White Paul et al. Effects of the frequency of transcutaneous electrical nerve stimulation on post operative opioid analgesic requirement and recovery profile Anesthesiology 1999; 91(5): 1232. 19. Pomeranz B, Chiu D. Naloxone blockade of acupuncture analgesia: endorphins implicated Life Sci 1976; 19: 1757.

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