Pain E-Book

Abdul-Ghaaliq Lalkhen

• Herausgeber: Atlantic Books
• Kategorie: Ratgeber
• Sprache: Englisch

Veröffentlichungsjahr: 2021

Beschreibung

'Combines a career's worth of expertise with a long history of pain treatment.For anyone concerned with pain treatment, or anyone who has struggled to manage pain of any kind, it's an important read.' GQ Pain is a universal human experience, but we understand very little about the mechanics behind it. We hurt ourselves, we feel pain, we seek help from a professional or learn to avoid certain behaviours that cause pain. But the story of what goes on in our body is far from simple. Even medical practitioners themselves often fail to grasp the complexities between our minds and bodies and how they interact when dealing with pain stimulus. Common conception still equates pain with tissue damage but that is only a very small part of the story - the organ which produces pain is the brain. Case studies show that a woman who has undergone a caesarean reports dramatically less pain than a patient who has had a comparably invasive operation. The soldier who drags themselves to safety after being shot deals with pain in a remarkably different way from someone suffering a similar injury on a street. The truth is that pain is a complex mix of nerve endings, psychological state, social preconceptions and situational awareness. Using case studies and medical history, Dr Lalkhen guides us through all aspects of pain, from chronic to acute, and the current landscape of pain treatments - from medication (including opioids) to electrical nerve stimulation. Whether it's a mild ache or severe discomfort, we all encounter pain in our lives and this important and illuminating book enables us to understand and cope with an experience that for so many can become all-consuming.

Leseprobe

First published in hardback in Great Britain in 2021 by Atlantic Books, an imprint of Atlantic Books Ltd.

Copyright © Abdul-Ghaaliq Lalkhen, 2021

The moral right of Abdul-Ghaaliq Lalkhen to be identified as the author of this work has been asserted by him in accordance with the Copyright, Designs and Patents Act of 1988.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior permission of both the copyright owner and the above publisher of this book.

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A CIP catalogue record for this book is available from the British Library.

Hardback ISBN: 978-1-78649-705-5

Trade paperback ISBN: 978-1-83895-067-5

E-Book ISBN: 978-1-78649-706-2

Paperback ISBN: 978-1-78649-707-9

Printed in Great Britain

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To my wife Nichola, whose patience and kindness has no equal, and to my parents and siblings who have always been both the anchors of my life and the wind in my sails.

‘But pain is perfect misery, the worst of evils, and, excessive, overturns all patience.’John Milton, Paradise Lost

Contents

Introduction: An unexpected journey

1: How does pain work?

2: A brief history of pain

3: Give me something for the pain…

4: The line between pleasure and pain – opioids and addiction

5: Pain with no injury

6: Pain management – needles, narcotics and knives

7: A journey of a thousand miles…

8: Torpedo fish

9: Do not go gentle into that good night

10: Show me the money – private pain practice

Conclusion: The beginning of the end

Acknowledgements

Index

INTRODUCTION

An unexpected journey

There is a special quality to the sound of the telephone when it rings at two in the morning. When you are working as the anaesthesiologist on a labour ward that call causes your heart to race and your stomach to do a little flip, adding another layer of fatty damage to your over-stressed coronary arteries. You have usually just fallen into an uneasy sleep on a lumpy bed in a damp but overheated on-call room, where many doctors have tossed and turned before you. The voice on the other end of the line is typically that of a harassed and overworked midwife. ‘Epidural – room 4’ might be all you hear before the deafening click of the slammed handset. There is the urban legend of an anaesthesiologist who, on receiving such a message, walked up to the room he had been sent to and stuck an epidural needle directly into the door before turning around and going back to his bed.

On entering a birthing room at 2.00 a.m., when the human spirit is at its lowest ebb, the scene is often predictable. There is a partner who looks scared out of his wits, a midwife who is fretting and trying her best to reassure everyone and a pregnant woman who is screaming in pain. You are greeted by an individual who would normally present a reasonable and calm image to the world but who is now reduced to a feral and illogical spectre as she is consumed with pain. The pain experienced during labour does not spare social class, colour or creed. Pain reduces us all to our barest elements; it is a great equalizer and unifier and one thing we all share an experience of.

As an anaesthesiologist you are therefore confronted by a woman who is demanding pain relief and may now be screaming at you and everybody who comes into her line of vision. Administering an epidural in these circumstances is challenging to say the least. When you return later, however, and the epidural has taken effect, you are greeted by somebody completely different – a calm, personable individual. The ability to transform someone’s demeanour completely by abolishing a barrage of unpleasant sensations that are coming from distended and damaged tissues has made a lasting impression on me, and I continue to be amazed at the transformation that takes place when pain is removed.

Whilst we now accept pain relief in labour as being an absolute right – and in first-world countries epidurals are provided on demand – this was not always the case. We have vacillated over the centuries between advocating that pain should be aggressively treated, and the belief that pain is necessary and important to the curing of the condition, or an integral part of the treatment being given. Inflicting suffering was thought to sometimes be inevitable, for example in the case of amputations before the invention of anaesthesia, or when ‘releasing evil humours’ by bloodletting with leeches. Pain was sometimes thought to be intrinsic to the success of the therapy, a sign of the patient’s vigour and helpful to their personal growth. ‘Pain is weakness leaving the body’ was an often-shouted phrase by my rugby coach; ‘Pain is good for you; it tells you that you are still alive’ was a phrase sometimes used by stressed doctors in the emergency department where I worked, when the umpteenth stab victim of the evening complained about the chest drain inserted to inflate a collapsed lung.

At one time, it was believed by priests that the pain of childbirth strengthened the bond between mother and child, reinforcing the idea of self-sacrifice inherent to motherhood, and that interfering with this pain would disrupt this maternal bond. Even in the early days of medical procedures, pain was not always seen as something that needed to be treated, largely because it was a sign of whether the patient was well and whether the treatment was working. It was only after 1800 that doctors became increasingly preoccupied with managing pain from injury or surgery, treating patients who had cancer, as well as non-cancer pain such as arthritis and migraines. When surgical anaesthesia was first introduced in the mid-nineteenth century, however, there were uncertainties expressed about the ethics of operating on an unconscious person and a concern that pain relief might retard the healing process. Priests, and some physicians, feared that its use would corrupt the individual’s soul, bringing into play a moral calculator to assess whether pain should be relieved or not. The development of medicine and surgery as endeavours which can only be accomplished through relieving pain, and a philosophical shift towards the value of the individual, changed the narrative from one where pain was believed necessary and a part of human life, to it being viewed as an experience which needed to be actively managed.

Religious writers initially deemed anaesthesia in the context of childbirth a violation of God’s law. This was obviously an idea proposed by men, and it was not until Queen Victoria had chloroform to facilitate the birth of one of her children that the practice of providing women with analgesia during labour achieved acceptance. Even today, the application of pain relief in labour varies across the globe; the mechanical stretching and contraction of tissues during labour is interpreted, perceived and responded to through the woman’s unique social and cultural lens. In the Chinese and Korean cultures, for example, birth must appear to be pain-free and is endured in silence, in order to not bring shame to the woman’s family, whereas in other cultures a more vocal response is believed to ensure a more solicitous and attentive husband.

What is it about pain that makes some people require medical intervention and others not? The storm of information created and transmitted by nerves when we are burnt, stabbed, bumped, bruised, shot, frozen, disappointed in love and life, jarred, shaken and irradiated is perceived, interpreted and modulated by our individual brains, which are as unique as snowflakes famously are. Pain, too, is therefore unique, individual and often confounds us and those we love and who love us.

*

I work at the Manchester and Salford Pain Centre at Salford Royal NHS Foundation Trust in the UK. The hospital is a major trauma and neurosciences centre located 5 km from the Manchester United football stadium. I split my time between anaesthetizing patients in the operating theatre, inserting electrical devices to relieve chronic pain and assessing individuals with chronic pain in an outpatient setting. But the reason I chose a career in anaesthetics was initially in order to become an intensive care doctor.

I was born and raised in South Africa, attending school and university under the shadow of Table Mountain. As a junior doctor in South Africa I worked in a major trauma centre and was exposed to some of the most horrific human-inflicted trauma imaginable. During the nine months that I spent in an inner-city trauma unit I developed a deep and pervasive antipathy towards people in general, and felt that I could only survive in medicine if my patients were asleep and if my interaction with them was brief. I found myself more comfortable with patients who were uncommunicative and found the stabilization of the injured person less emotionally taxing than a biopsychosocial assessment of the journey that had brought them to hospital. It didn’t help that at the time I was unhappily in love. This was also a time when there were influential government leaders who denied that HIV caused AIDS and when this statement was repeated to me by a patient who had been diagnosed HIV-positive and who was refusing to disclose this information to her partner, I coped by running away from home.

I went on to become an anaesthesiologist, completing my training in the UK, where I remained. Over time I specialized in pain medicine, an area that often comes under the remit of anaesthesiology, for reasons we will come to later. I now work in a pain clinic, with patients who suffer acute pain – that is to say pain with an easily identifiable cause (traumatic injury or surgery) that will eventually go away when the physical damage heals – or with chronic pain, that may not have a clear cause and may not go away.

The emotion that is primarily felt when you are faced with somebody who is in pain is extreme helplessness. In many ways pain is designed to elicit this response from others because we are social animals and one of the purposes of a visible pain experience, manifest as pain behaviours, is to encourage help from others – pain behaviours have survival value. Seeking assistance after an injury is as biologically imperative today as it was a thousand years ago. What has changed over time, however, is the place of healing and the people we seek healing from. A thousand years ago a sick person might have attended a temple to meet with a priest, since health and spiritual well-being were inextricably linked and so the priest served as both healer and spiritual guide. At an even earlier time in human history, the person consulted might have been the local medicine man, who would also have communicated with the ancestors to find answers to various afflictions. Today, we have huge biomedical temples called hospitals and networks of shamans called general practitioners, organized into a hierarchical system and monitored by professional bodies.

The nature of the interaction between doctor and patient has changed over the centuries based on our accumulated knowledge of physiology and anatomy, as well as our understanding of disease and treatments. Today, most individuals in society can understand traumatic pain without knowledge of the complex neurophysiology involved. We understand to a degree that if we injure ourselves then we experience pain, in the same way that a car or house that is broken into results in activation of an alarm. Pain is an alarm bell that something is wrong and a call to seek medical help. In the modern world, however, our understanding of pain as an alarm system has limited benefit in a society where we voluntarily subject ourselves to the trauma of surgery, for example – and yet pain continues its primitive wail despite our enhanced ability to understand and manage trauma and disease. It is this disconnect between the biological and the psychological that often makes modern pain management ineffective. Even when pain is due to an injury, seeking help is easily understood but it is still governed by the individual’s perception of the severity of the injury and their health-seeking behaviour, which in turn is governed by a host of psychosocial and cultural factors. Most people, including doctors, do not appreciate that the organ which produces pain is the brain. It is not the broken bone, or the damaged tissue or the bleeding wound. The experience of pain is the sum total of more than just the physical injury – it is the result of this information being filtered through the individual’s psychological makeup, genetics, gender, beliefs, expectations, motivations and their emotional context.

We have a collective delusion that the human body is a simple machine that can be repaired by the medical profession when it breaks down. However, the reality is that the human body is not a simple machine; it is an organism which progressively deteriorates over time and then, eventually, ceases to function. Pain as an experience is often seen simplistically as a manifestation of a dysfunctional machine, and is often a consequence, when it becomes chronic, of a machine that has been poorly treated. Unfortunately, rather than recognizing that it is the behaviour towards the machine that needs to change, we have a tendency to medicalize this pain and therefore often apply excessive amounts of lubrication in the form of opioids and surgery, which do nothing to improve the function of the machine and in fact can cause a significant deterioration of the organism.

Simply put, we need to stop viewing our bodies as machines that medicine can fix when they go wrong. If people are educated about their bodies and about pain, then perhaps we might put an end to the undulating fashions of medical meddling; meddling which, in some cases, has far-reaching consequences only appreciated decades later. We are currently, for example, at the tail end of an epidemic of opioid prescribing and are beginning to see the effect of that rampant scourge on individuals and on our society. Once upon a time the use of opiates was the province of recreational drug users and abstaining from opioids, even in the face of severe pain, was considered not only appropriate but admirable. The changing understanding of the possible advantages of treating pain after surgery or injury swung the pendulum towards increased opioid prescribing, with the relief of pain regarded as a human right and a benefit to the patient. We now see addiction, tolerance, dependence and withdrawal, as well as the long-term physical effects of prescription opioid use on patients. We have begun to realize, as medical professionals, that our overzealous management of acute post-operative pain and our mistaken treatment of chronic pain (as opposed to acute pain due to injuries) with the same medication has had unintended consequences.

My mission in this book is to explain pain in all its forms – pain from physical trauma, cancer pain and pain which appears to continue in the absence of any physical damage. We all suffer with pain at some point in our lives and are witness to the pain of those we love and care for. With renewed knowledge and understanding, we can become active participants in the art of caring, understanding and coping with an experience that can become all-consuming.

CHAPTER 1

How does pain work?

You may have purchased this book to read whilst on holiday somewhere, as you bask in sunshine. Currently you may be being tortured or delighted by the excited screams of children around you, or feeling gentle breezes blowing from the sea, whilst the smell of suntan oil permeates the surrounding air. Your swimsuit may be slightly damp from the last time you were in the swimming pool. Regardless of the sounds, smells and temperatures you are exposed to, these sensations are all quite easy to tune out and simply become background noise. However, if you were to be bitten by a mosquito, or an exposed part of your body started to object to the strong sunlight, then this experience would demand your attention and it would take a great deal of conscious effort to ignore. This is the universal experience of pain. Physiologists like to refer to pain as ‘aversive at threshold’, which means that it cannot be ignored or subdued easily. Its very nature demands attention, and this is as true today, as you sit languishing idly around a swimming pool, as it was when we were a primitive species fighting for survival in a harsh and untamed world.

But whilst damage to our bodies may eventually demand our attention through the experience of pain, this experience can be ignored, sublimated or delayed by the brain. Pain is a warning system, informing us that there is a threat to the safety of our bodies or even that damage has already occurred, but if experiencing pain and receiving this information is not immediately beneficial then the message relaying this information will be de-prioritized and sometimes ignored by the brain. We all know how crippling and all-consuming the experience of pain can be, and if it might delay, for example, our flight to safety, then it is not immediately helpful and could even be dangerous. The relationship between physical damage and the experience of pain can tell us a lot about the complexity of the biological pain alarm system and the processing of the information about damage, the route this message takes, and why, how and when it can be disrupted.

Whilst playing for Milan against Chievo on 14 March 2010, David Beckham ruptured his Achilles tendon in the eighty-ninth minute of the game. Video footage shows him turning sharply and trying to control the ball – the sharp turn is probably what caused the injury. He then starts to limp because his ankle will no longer flex and extend since he has now lost the use of his calf muscles that rely on being fixed to the ankle bones via the Achilles tendon. It appears that initially he does not realize he has injured himself – I imagine most professional sportspeople exist with a level of discomfort that would be abnormal to the rest of us and so the natural tendency would be to ignore the messages reaching his brain and carry on in the context of practising his profession. He tries again to run up to the ball to kick it but finds that he cannot perform this action – his progress is halted not by pain, as yet, but by loss of mechanical function. The tear to his Achilles tendon has already occurred moments before, and whilst the process by which information about this damage is converted to an electrical signal began at the moment of injury, it has not yet registered in his brain as pain.

When you sustain an injury, the traumatized tissue releases and attracts chemicals called inflammatory mediators. The aim of these substances is to try to heal the damaged tissue, but they also play a role in triggering the pain alarm. The release of chemicals such as hydrogen ions, potassium ions, bradykinins and prostaglandins stimulates the harm-sensing receptors in the tissues. The first step in the body’s complex pain alarm system, which we all possess (unless we are born with congenital hypoalgesia, which is a condition where people do not feel pain), is the conversion of damage to the body into an electrical signal. Throughout our bodies there exist receptors (which are like locks on doors) on free nerve endings called nociceptors – the prefix noci means harm or mischief in Greek – and these are harm-sensing receptors. Harm-sensing nerve endings are widely distributed in the skin, muscle, joints, organs and the lining of the brain, and are either covered with myelin, which is a fatty tissue, or are uncovered. Myelin-sheathed nerve endings (A delta fibres) conduct electricity faster than their thinner uncovered counterparts (C fibres); the faster signals from the A delta fibres make you instantly remove your hand from a hot object, whereas the slower fibres produce the sensation that teaches you not to do it again.

The human body can only be injured in three ways: mechanical trauma (such as gunshots, stabs, bumps and scrapes), chemical injury (a burn from an acid or an alkaline substance) and injury from extremes of temperature. All of these injuries result in the release of inflammatory mediators. Inflammation can also occur when the body’s immune system attacks itself or joints become inflamed. Nociceptors are of different classes and, like locks, they are all opened with different keys – intense pressure, temperatures greater than 40 to 45°C or less than 15°C, or chemicals released from injury and inflammation. In Beckham’s case, the damaged Achilles tendon releases substances including histamine, serotonin, bradykinin and hydrogen ions, which insert themselves into nociceptors, triggering an electrical impulse which communicates and codes for harm and damage, and begins its journey to the brain, where that message can be decoded.

The information that the body has been damaged first passes from the Achilles tendon to an area of the spinal cord called the dorsal horn and information is then passed into the substance of the spinal cord, which is an extension of the brain, and enables communication between the brain and the rest of the body. The dorsal horn is constantly receiving information both from the outer reaches of the body and from the brain via the spinal cord; it is like a bowl of soup whose flavour can be altered by inputs from the brain or from the peripheral nerves, rather than existing as a hardwired, fixed computer component. The face and neck are slightly different to the rest of the body, in that the nociceptive nerve endings meet in a structure called the trigeminal ganglion which projects to the brainstem that is located in the base of the brain.

Once the thin C fibres and fat A delta fibres mentioned above have conveyed information to the first and second layers of the dorsal horn, a chemical substance called glutamate is released from the dorsal horn nerves when the electrical signal generated from nociceptor activity reaches it and this opens doors within the spinal cord, sending a message to the brain about what has happened. The graver the injury, or the more times it is inflicted, the more keys are made available and the more doors are opened, resulting in more information being sent from the spinal cord to the brain – a phenomenon called wind-up, which contributes to the persistence of pain even when the injury has healed.

There are five superhighways of information ascending to the brain from the spinal cord – the spinothalamic tract (the ‘where is the problem’ pathway); the spinoreticular and spinomesencephalic tracts (triggering arousal, emotion, fight or flight instincts and activating motivation circuits in the brain which determine how we behave towards injury based on previous experience); and the cervicothalamic and spinohypothalamic pathways (controlling the regulation of hormones).

From the Achilles tendon this information rushes to the brain via these superhighways in the spinal cord and lights up different parts of the brain like the colours from a single firework which when ignited spreads across the night sky. The information travels to the area of the brain called the thalamus which is connected to the sensory part of the brain which deals with location and sensation (spinothalamic), as well as the areas which are responsible for sensing and coordinating emotion (spinohypothalamic), mediating the emotional components of pain. The survival and awareness areas of the brain are reached via the spinoreticular circuit, bringing into play the areas that facilitate an increase in heart rate, blood glucose and blood pressure to deal with whatever danger may be around. Connections are also made to the parts of the brain that deal with motivation. We are driven as humans by that which is necessary for survival – food, sleep, the avoidance of pain – and we are also driven by rewards which can be any experience that facilitates learning or results in pleasure; these motivation circuits develop early on and continue developing throughout our lives, determining how we behave. The damage signals also reach the parts of the brain that can release substances which cause pain relief (naturally occurring opioids and cannabinoids). Connections are made to the pathways that descend from the brain to the spinal cord and which are responsible for suppressing signals from the spinal cord, reducing the unpleasant information reaching the brain and thereby reducing the pain experienced. Pain is therefore always a sensory and an emotional experience, as these ‘superhighways’ connect to areas of the brain that involve both.

What is interesting when rewatching the footage of Beckham being injured is that initially there is no indication that he is in pain – he frowns, more confused than distressed, and continues to try to play. He eventually realizes that he cannot kick the ball and examines the area of his body that is not working properly. He knows where he has been injured because his brain has already received a message from the Achilles tendon which has registered in the part of the brain that deals with location when it comes to pain, but we do not yet see his outward expression of pain because the information is still being considered and evaluated.

What follows this assessment of the injured area is the realization of the injury and, more importantly, its meaning for him as an individual. This information is then processed through the parts of his brain that deal with emotion and context (the hypothalamus). I bet his initial thought was, ‘No World Cup. There goes my chance of captaining England.’ Once this information has been processed by his brain, we see him collapse under the weight of the implication of this injury. He lies on the ground distraught, holding his head in his hands. We see not only the expressions of pain but also the very visible experience of suffering. The sequence of events that we have witnessed, from the moment that he struggles to strike the ball to his collapse, is a powerful example of how pain and injury are not proportional to one another. It is only when an individual processes the injury in terms of attaching meaning to it that the expressions of suffering and pain are exhibited. In this way pain is a form of communication – it allows other people to see what the injury means to us as individuals and it has survival value in that our expression of pain will produce empathy and assistance.

Beckham sits on the bench with a towel over his head. The injury has not healed and therefore harm-sensing receptors are still being activated – nociception is ongoing. The information continues to reach the parts of his brain that were activated at the time of the injury, but he is no longer rolling about on the pitch; the experience of pain has been suppressed to a degree. This is caused by the activation of descending inhibitory pathways which project from the brain down to the spinal cord. The brain, therefore, can modulate the information coming up from the injured area and the pain experience is altered. The brain acts like a policeman controlling traffic, deciding how many of the cars coming from the Achilles tendon are allowed through. The brain also decides how much attention to pay to the individual drivers of these cars. The need for immediate attention is over for Beckham – the behaviours which he exhibited are no longer necessary, nor are they socially or psychologically acceptable. The game must go on and he must retire privately to decide on where he goes from this point in his life. This is the loneliness of the pain experience.

The descending inhibitory pathways which project from the brain are poorly understood. Functional magnetic resonance imaging (fMRI), which lights up parts of the brain in response to a painful stimulus, has been used to theorize about which areas of the brain are involved in suppressing pain. Parts of the emotional centre of the brain, the hypothalamus, which is responsible for appraising the sensory information, as well as the rostroventral medulla (part of the midbrain), are important for integrating these descending pathways to the spinal cord. Interestingly the same brain chemicals which we try to increase with medication when treating depression (serotonin and noradrenaline) are fundamental to the activation and functioning of these pathways. This is why individuals who are depressed often experience increased pain, because the lower levels of these chemical neurotransmitters are insufficient to activate the descending inhibitory pathways.

And so, we see that not all signals that are being sent from the Achilles tendon are being perceived in Beckham’s brain at the point of injury and in the immediate aftermath. Attention to the injury, emotional processing of the experience, expectation and thinking about the meaning of what has happened – these are all triggering return messages from the brain that regulate and control the information travelling from the injured area and moderate the consequent pain suffered.

I often use the example of David Beckham’s injured tendon when I explain to medical students the difference between tissue damage and pain. Initially he does not appear to be in pain; although of course we do not know that this is the case and can only surmise from the behaviour that he exhibits. He tries to continue to play. The information about the damage has already reached his brain but until he makes sense of what has gone wrong, we would not recognize his behaviour as that of exhibiting pain. This same situation, with regards to the mental processing of an injury, is why soldiers injured in battle are sometimes not found to complain significantly of pain even in the presence of horrific injuries such as amputations. The immediate concern of the individual is to get to safety and the brain can override the pain experience to facilitate this. It is only when soldiers reach a place of safety that an appraisal of the injury can be made. The injury results in the soldier having to leave the battlefield – a place of danger – and once this stress factor is removed the individual’s response to the injury similarly changes. In 1981, Ronald Reagan was shot in an attempted assassination. He recalled later that he only realized he had been shot in the chest when he felt and saw the blood seeping through his shirt in the limousine on the way to hospital.

The above examples of a delayed pain experience can be contrasted with those of people who are caught in fires, where immediate and severe pain is experienced. When you have been burnt in a civilian situation there is none of the modulating environment of a battlefield with its chaos or the distraction of being hastened to safety by Secret Service agents and nor, crucially, was there any expectation of possible injury when entering the arena and so the event is unexpected and thus deemed catastrophic by the victim. Burn injuries are also amongst the most painful given the degree of damage which is done and the widespread activation of harm-sensing receptors on nerve endings.

We all appreciate and understand the kind of pain described above, caused when tissues are broken, torn or damaged in some way; it is no different, perhaps, from the experience of primitive or ancient man, who understood the pain inflicted by an arrow, but failed to appreciate the pain from degenerative joints or infected, inflamed tissues. But as we have seen, injury and pain are not proportional, and the outcome of pain is dependent on more than just the degree of damage sustained – this can be harder to understand.

Pain as an experience is influenced by beliefs and expectations as well as psychological factors such as mood and resilience. An individual’s culture, genetics and innate ability to cope with adversity will all impact on their experience of pain. The rupture of an Achilles tendon on a squash court has very different implications to the same injury in a professional footballer who has aspirations of captaining a national side in a World Cup tournament; a soldier on the battlefield responds very differently to discomfort or injury than a member of the public who is injured at home, yet they both have the same internal chemistry.

The complexity of the psychological experience of pain is often best understood by looking at an individual’s reaction when they sustain an injury – their facial expressions, language and the sounds they make. But this needs to be considered alongside the physical processes taking place; the danger is that we might begin to consider the psychological experience as being separate from the pain pathways that I have described above. I talked about activation, for example, of the fight or flight system. We know that the release of adrenaline as a response to stress can cause an increase in muscle tension and the increase in muscle tension reduces blood flow (and therefore oxygen supply) to the muscle, which then releases bradykinin in response to being starved of oxygen; the bradykinin then activates more harm-sensing receptors. Anxiety and stress, therefore, which we would regard as psychological constructs, influence the pain experience on a biological basis. If a doctor is kind to you in a hospital when you are in pain, then that pain can be relieved to a degree even before the doctor has given you any pain relief, because kindness activates the descending inhibitory pathways. Similarly, whilst hostile social situations or hazardous environmental factors can cause the suppression of pain, as we saw in the instance of soldiers on a battlefield, in other environments these factors can actually aggravate the pain experience because, as we saw with adrenaline, stress influences the production of hormones, which activate parts of the brain that can either exacerbate or relieve the pain. The differing effects of psychosocial factors on an individual’s pain experience depend on how they are interpreted. There is, therefore, an integral relationship between psychological, social and environmental factors with tissue injury. This is why, when considering the experience of pain, a biopsychosocial model is used, which proposes that psychological and behavioural processes are mediated by the individual’s biology, rather than representing some esoteric force which descends from the ether – in other words, eventually it’s all down to chemistry.

As human beings we struggle with understanding how our behaviours and thoughts influence our biology via hormones and neurotransmitter chemicals. It is why individuals with mental health disorders are so marginalized and poorly understood and are therefore discriminated against, whilst we readily accept high blood pressure as a disease because it has a physiological explanation, even if most of us would never be able to outline how blood pressure functions within our bodies. Very few individuals understand that normal blood pressure is the product of the output of the heart multiplied by the resistance in their blood vessels and that abnormal blood pressure is a result of dysfunction of these blood vessels. We would not respond to somebody with high blood pressure by telling them to calm down or relax their blood vessels. Unfortunately, patients who present with pain that we consider to be in excess of what we would expect, or who have lowered mood, are often told to just get on with it and to stop being histrionic.

*

Depression and anxiety play a role in the experience and report of pain. Catastrophizing is a psychological construct that consists of excessive rumination, magnification and helplessness in the face of adversity, and involves extreme negative thoughts about one’s plight. A higher level of catastrophizing, and consequently feeling a lower sense of control, is an important predictor that a patient will experience severe acute pain or develop chronic pain, when pain persists beyond what would be medically expected. Catastrophizing may be thought of as an exaggerated negative pattern of thinking which is brought to bear during actual or anticipated painful experiences. Where patients catastrophize to a high degree they experience greater levels of pain and emotional distress. This abnormal pattern of thinking can have a significant biological impact, as it can increase pain signals and may result in increased sensitivity of the pain alarm, potentially leading to the permanent activation of the pain alarm even after the once-damaged tissues have healed and resulting in progression from acute to chronic pain.

This can be in part due to the development of pain-related fear, where patients adopt an approach to managing persistent pain by trying to avoid activities that might cause an increase in pain. Patients who have undergone surgery or experienced trauma and who have high levels of catastrophizing, for example, may find it difficult to rehabilitate because of this psychological construct. Their way of coping with pain is to avoid movement; however, this may have consequences such as the development of deep vein thrombosis when they remain in bed and the blood in their legs pools like stagnant water, as well as lung infections when they fail to cough or breathe deeply following surgery. These patients are also more likely to use higher doses of pain-relief medication.

Preoperative anxiety is one of the most consistent and predictable risk factors for the severity of post-operative pain. One of the key messages that I communicate to trainee doctors who assess patients prior to surgery is to never tell anybody that they will have no pain following surgery. I tell them to explain to the patient that if zero equals no pain and ten is the worst pain imaginable, then at best we can probably get their pain down to four following the operation. If patients have this 4/10 construct in their heads when they wake up and assess the sensory information reaching their brain, then it may allow them to cope better with the post-operative pain. If you tell them that they will feel no pain when they wake up, then any unpleasant sensory information will be appraised in a catastrophic manner.

The importance of this approach is often emphasized to me when I look after patients who have had a laparotomy, which involves cutting through all of the individual’s abdominal muscles and tissues to get to their bowels. The incision is often 10 or 15 cm long and can extend from above the pubic bone to just below the chest. We use epidural pain relief for these operations, and this is often very successful; a catheter is threaded into the epidural space, which lies just above the spinal cord, and the infused local anaesthetic bathes the nerves as they leave the spine. This technique usually provides excellent pain relief for what is a massive traumatic incision. These operations often require patients to have a plastic tube in their throats for a prolonged period and also to have a plastic drip put into one of their neck veins. I am always amazed when patients wake up and complain bitterly of the plastic tube in their neck and a sore throat, and are almost unmanageable as a consequence, in the face of a 15-cm incision which is being covered from a pain relief point of view by the epidural. The anaesthesiologists’ preoccupation with the laparotomy wounds and the epidural often causes us to forget that patients will attach meaning to any unpleasant sensory information following surgery, even for issues that we would regard as minor compared with the pain that they would be experiencing if they did not have the epidural. This is why patient-centred care is much more successful in helping people than cliniciancentred care.