The complexity of pain assessment and management in the first 24 hours after cardiac surgery: implications for nurses. Part I

Helen Hancock

Helen Hancock B N, Dip App Sc (Nursing), Dip Critical Care, ENBcc249 Cardiothoracic Nursing, Senior Staff Nurse, Critical Care, Papworth Hospital, NHS Trust, Papworth Everard, Cambridge CB3 8RE, UK

(Requests for offprints to HH) Manuscript accepted

Part 2 of this article will be published in the next issue: 12 (6) December 1996

Pain has been recognised as a problem within the realms of health care for many years (Szanto & Heaman 1972, Melzack 1973). The management of pain in the immediate postoperative period remains one of the most serious inadequacies of health care today (Royal College of Surgeons 1990). Recent evidence suggests that up to 75% of hospitalised patients fail to receive adequate pain relief (Carr 1990), with postoperative cardiac patients reporting detailed recollections of their pain experiences during their stay in critical care areas (Ferguson 1992). To accountable health care professionals these figures are humiliating and cannot be allowed to continue (Hollinworth 1994). Indeed, the persistance of postoperative pain can seriously compromise the status of postoperative cardiac patients (Wild 1992).

An exploration of current practices in pain management for adult individuals following cardiac surgery included a review of the methods of assessment and treatment interventions employed at three English critical care units. With the literature providing substantial evidence of research into post-operative pain management the persistence of postoperative pain was questioned.

Inadequacies in nursing knowledge were identified in all areas of postoperative pain management. The persistence of the theory-practice gap was identified as a major factor contributing to the maintenance of current practice. Similarly, the inappropriate use of change strategies, aimed ultimately at enhancing patient care, proved significant. The findings, which show neglect of the nursing responsibility for the provision of research-based, high quality patient care, carry implications for all nurses. Recommendations including the development of new strategies for the inclusion of existing knowledge into practice appear vital, in order that clinical practice, and ultimately patient care, can be enhanced.

INTRODUCTION

Pain serves in advisory and protective capaci- ties, bringing informative sensory experiences to the cerebral cortex to warn of actual or potential tissue damage (Doverty 1994). Its persistence in the post-operative period, how- ever, can have profoundly negative physio- logical and psychological effects (Puntillo 1991). With the consequences of unrelieved post-operative pain further compromising the status of critically ill individuals (Wild 1992), the importance of effective pain management is emphasised. Ultimately, successful manage- ment is dependent upon a thorough and accurate assessment of each patient's pain expe- rience with subsequent, appropriate pharmaco- logical and non-pharmacological interventions (Gujol 1994).

The complexity of pain is heightened during the immediate post-operative period by the physiological transition which follows cardiac surgery (Wild 1992). Combined with the psychological implications of surgery this physiological transition and treatment interven- tions at this time complicate the assessment of pain (Guzman et al 1989). However, recogni- tion of its complexity does not negate the responsibility of health care professionals in its management.

While it is obvious that all health care pro- fessionals contribute to the efficacy of acute pain management (Henkleman 1994), the nursing role appears central to its success (Caunt 1992). The uniqueness of the nurse- patient relationship facilitates an enhanced awareness of the physiological and psychologi- cal impact of pain on the individual patient (Mallick & McHale 1995).

Intensive and Critical Care Nursing (1996) 12, 295-302 © 1996 Pearson Professional Ltd

296 Intensive and Critical Care Nursing

Identified as a research priority by critical care nurses in 1983 (Lewandowski & Kositsky) and again in 1992 (American Association of Critical Care Nurses), the continued inade- quacies of pain management show neglect of an integral component ofindividualised, bolls- tic patient care for which nurses remain responsible (Holden 1991, Walsh & Ford 1992). While information surrounding the management of post-operative pain increases, clinical practice appears largely unchanged (Kehlet & Dahl 1993, Kitson 1994). The per- sistence of current practice shows neglect in the acquisition and application of research- based knowledge, aimed at improving the quality of patient care, as vital components of professionalism (Emerton 1992). Recognising that the acceptance of change is determined by more than the acquisition of research-based knowledge (Nolan & Grant 1993, Wilkinson 1994), an exploration of change theory may provide insight into the persistence of the the- ory-practice gap.

In view of the diversity of the topic, it is not possible in this paper to attempt to explore all aspects of it, but rather to provide insight into an area identified in the literature as defi- cient. Issues of professional responsibility are highlighted with particular reference to issues of patient autonomy, beneficence, non-malef- icence, patient rights, advocacy and the United Kingdom Central Council for Nursing, Midwifery and Health Visiting (UKCC) 'Code of Professional Conduct' (1992a). With a focus on the pain manage- ment of adult individuals following cardiac surgery, a review of current practices in three English critical care units is undertaken. This includes an analysis of pain assessment tools utilised, methods of documentation and cur- rent modes of treatment employed, with the aim being to identify factors contributing to the current inadequacies of pain management. However, in order to establish an understand- ing of its constructs, discussion will initially focus on a definition of acute pain, with sub- sequent reference to its impact in the post- operative period.

PAIN A N D N O C I C E P T I O N

In searching for a definition of pain, one is struck by the diversity of the numerous defini- tions. While many people assert that there is no agreed or acceptable definition (Jacques 1992, Peat 1995), the concept of individual experience persists in each definition. Described by McCaffery (1979, p 14) as 'what- ever the experiencing person says it is', the

complexity and individuality of the pain ex- perience emerges.

Numerous theories, including Melzack and Wall's Gate Control Theory (Melzack & Casey 1968), contribute to a greater understanding of the multidimensionality of the pain experience (Dalton et al 1994). Current theorists subscribe to the belief that it is neither a purely physical nor a purely psychological phenomenon (Walding 1991, Glynn 1992).

Literature surrounding the realms of pain describes it as the product of two halves - 'sensory' and 'reactive', where 'sensory' describes its type and intensity and 'reactive' refers to the meaning attached to the pain (Puntillo 1988). With this belief, post-opera- tive pain becomes an increasingly complex experience which extends far beyond the realms of nociception (Mitchell & Smith 1989), a term used to describe the transmis- sion of noxious stimuli to the spinal cord and thalamus (Wallace 1994).

The central processing of nociceptor input is strongly modulated by the 'reactive' ele- ments of the pain experience such as fear, anxiety and helplessness. Individuals identify and give meaning to their pain using environ- mental, experiential, cultural and pathologi- cal factors to influence this meaning (Jacques 1992). Impending cardiac surgery, for exam- ple, may be viewed as a positive or negative experience. For some individuals it represents an opportunity to return to a lifestyle they led prior to illness. Others, however, with their view of the heart as 'the centre of emotion' and 'the key of life', see surgery as a great threat (Ferguson 1992). Similarly, hospitalisa- tion may evoke a negative psychological reac- tion as the individual focuses on issues of spouse separation, isolation, loss of indepen- dence and helplessness. The degree of such negative responses has been shown to corre- late closely with subsequent pain perception (Mitchell & Smith 1989). Indeed, Ferguson (1992) found an increased awareness of nox- ious stimuli in patients exhibiting anxiety states.

I M P L I C A T I O N S OF UNRELIEVED POSTOPERATIVE PAIN

Physiological changes occurring in response to noxious stimuli can significantly compromise the status of post-operative cardiac patients (Wild 1992). Acute pain, such as that following surgery, is generally associated with actual or potential tissue damage (Peat 1995), together with objective physical signs of autonomic nervous system activity such as tachycardia,

Complexity of pain assessment and management in first 24 h after cardiac surgery 297

hypertension, diaphoresis, mydriasis and pallor (Payne 1990). The physiological consequences of pain and the resultant stress response affect many body systems and can further compro- mise the status of a critically ill patient (Wild 1992).

Postoperative pain for a cardiac patient is a multidimensional phenomenon. Patients may experience pain as a result of surgical inci- sions, intra-operative manipulation and dis- section, acute myocardial ischaemia, dissect- ing aortic aneurysm and other iatrogenic factors such as invasive monitoring, endotra- cheal tubes, nasogastric tubes, chest drains and urinary catheters (Gujol 1994, Maxam- Moore et al 1994). However, due to the uniqueness of each individual's experiences it is impossible to predict the relationship between pain and the individual patient (Briggs 1995).

As previously established, the individual's whole pain experience must be considered in order to make a true assessment of it. Indeed, an individual's response to a threat (in this case cardiac surgery) depends not on the degree of the threat but on the individual's capacity for coping (Ferguson 1992). Although some surgery, such as internal mammary artery bypass surgery, is associated with a specific pain syndrome, it is vital that pain management strategies are aimed at the individual's response to that pain (Mailis et al 1989).

Ultimately, the provision of adequate pain relief depends more on the patient's perception of pain than on the precise clinical picture or diagnosis (Sutcliffe 1993). Ignorance of the psy- chological impact of a pain experience may result in the persistence of pain, poor recovery and an increased length of hospital stay (Twycross 1984). With questions of the market economy and resource management at the forefront of health care today, the conse- quences of inadequate pain management repre- sent added burden to an already stressed indus- try (Hollinworth 1994).

Pain relief is desirable, not only for humane and moral reasons, but because it improves the patient's psychological and physiological well-being (Carr 1990). Such relief, however, proves particularly difficult in the immediate post-operative period (Shelly 1994, Tittle 1994). While vital to the success of pain management, a thorough and accurate assessment (Gujol 1994) is complicated by significant physiological changes, the pres- ence of endotracheal tubes, oxygen therapy, vasoactive drugs and sedatives. Combined with the psychological impact of the critical care experience they contribute to the cur- rent inadequacies of post-operative pain relief (Guzman 1989).

V A S O C A C T I V E D R U G S A N D S E D A T I O N I N T H E P O S T O P E R A T I V E P E R I O D

Post-operative alterations in cardiac function frequently necessitate the use of vasoactive medication and (less frequently) support devices in order to maintain cardiac output (Leatham et al 1991). The persistence of a low cardiac output state requires the use of ino- tropic drugs (George et al 1994) such as dopamine, dobutamine, adrenaline, isopre- naline and noradrenaline. Their effects produce various combinations of action on heart rate, force of contraction, peripheral vascular resis- tance and renal perfusion.

Additionally, in the immediate post-opera- tive period vasodilators such as sodium nitro- prusside are used to achieve controlled dilation of the vascular bed with subsequent control of hypertension through a decrease in afterload (Leatham 1991). However, such control over cardiovascular status masks the normally objec- tive physiological signs of the pain response, further complicating accurate assessment of the individual's pain experience and its manage- ment (Kremer & Bachenberg 1993).

Similarly, while recognising sedation as an essential part of the care of cardiac patients (Doherty 1991), one must also consider its presence as one of many barriers to communi- cation, and therefore accurate pain assessment, during this time. Identified as a serious problem in critical care areas of the UK, effective com- munication appears fundamental to the relief of pain and suffering (Shelly 1994). The presence of such barriers in the post-operative period highlights McCaffery's (1979) emphasis on ver- bal communication in her definition of pain, raising questions of its real value in critical care.

Utilised in the early post-operative phase of cardiac surgery, sedation decreases restlessness while also increasing ventilator compliance (Nightingale & Pleuvry 1985). By reducing tachycardia and hypertension, factors known to increase myocardial oxygen demand, and by reducing the incidence of arrhythmias, its use facilitates a more stable cardiovascular system (Shelly 1994).

Interestingly, preferred levels of sedation for patients in English critical care units have changed in recent years. Research in 1981 revealed that 67% of units preferred patients to be deeply sedated and unaware of their sur- roundings; 91% used neuromuscular blocking agents frequently (Merriman 1981). In 1987 only 16% of units used neuromuscular blocking agents frequently (Bion & Ledingham 1987), most commonly in the treatment of ventilated patients (Wild 1992). Further, 69% of units

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preferred patients to be asleep but easily rous- able and compliant with care (Bion & Ledingham 1987). In post-operative cardiac patients, sedation must be kept to a minimum in order to avoid the complications of pro- longed mechanical ventilation (Kremer & Bachenberg 1993). The practice of early extu- bation removes one of many barriers to com- munication with resultant positive psychologi- cal effects on the patient. Indeed, one of the most stressful aspects of mechanical ventilation and endotracheal intubation is the inability to speak (Menzel 1994).

Ultimately, these changes to clinical practice avoid the risks of oversedation including coma, hypotension, immunosuppression, hepato- toxicity and renal dysfunction (O'Sullivan & Park 1991), and avoidance of these promotes uncomplicated recovery. Furthermore, haemo- dynamic changes are likely to reflect changes in the patient's clinical condition, including the physiological manifestations of the pain experi- ence, rather than those of altered sedation levels (Shelly 1994). While recognising that the use of vasoactive drugs (vital in the treatment of post- operative hypertension and tachycardia) may mask the symptoms of pain, a reduction in sedation levels will ultimately promote a more objective assessment of the patient's pain expe- rience (Kremer & Bachenberg 1993).

Despite these changes and consequent opportunity for enhanced nurse-patient com- munication, the control of post-operative pain remains inadequate. While research describing pain experiences of patients in critical care settings is limited, studies confirm that cardiac patients both recall and express concern regard- ing their pain experiences while in the critical care area. In a recent study of cardiac surgical patients, Puntillo (1990) found that 70% (n = 24) recalled having pain during their critical care stay. Further, patients specifically remem- bered hearing others crying and calling out in pain (Daffurn et al 1994). While it is apparent that asking patients what they remember of their stay in the critical care setting may not be a good index of their experience, it allows a con- sideration of the factors that cause distress.

C O M M U N I C A T I O N IN THE I M M E D I A T E POSTOPERATIVE PERIOD

The current trend of decreased sedation of post-operative cardiothoracic patients requires a greater focus on verbal contact between health care professionals and individual patients within critical care settings. Interestingly how- ever, the amount and quality of such commu-

nication is often largely dependent on the physical condition of the patient (Leathart 1994). It appears that in the midst of attending to derangements of major organ functioning, health care professionals frequently neglect the critically ill patient's pain and its relief (Maxam- Moore et al 1994).

Although medical staff prescribe analgesics, much of the responsibility for patient comfort rests with nurses who must assess, plan, imple- ment and evaluate pain-relieving intervention (Kitson 1994). The assessment of pain during the immediate postoperative period is compli- cated by patients' inability to communicate their pain verbally (Leisifer 1990). While barri- ers to communication account for part of this problem, it appears that current methods of communication contribute significantly to its inadequacies. In a study of communication problems between nurses and patients in five (English) critical care areas, Ashworth (1980) found that 71% of communication consisted of short-term, task-related information, com- mands or questions. In a similar study, Leathart (1994) found interactions to be brief (less than 1minute), and consisting of nurse-oriented, short-term information, questions and com- mands. Further, Sayler & Stuart (1985) found that patients initiated interactions with the nurse only 15% (n=217) of the time. While the validity of their research is questionable, with the possible influence of the Hawthorne effect (Treece & Treece 1977) on its results, it reflects the reluctance of patients to 'interrupt' nurses with reports of pain (Leathart 1994). Current realities o f inadequate staffing levels appear significant in the establishment and maintenance of effective communication, with work overload identified by nurses as a con- straint to its success (Bergbom-Engberg & Halj ame 1993).

Failure to promote effective communication with individual patients represents a failure to fulfil the professional commitment to nursing. Nurses are responsible for patient advocacy related to pain management (Tittle 1994). Advocacy, the assertion of the rights of another person who is unable to assert his or her rights (Henkleman 1994), is based in the develop- ment of the nurse-patient relationship and a resultant partnership whose focus is on agreed health care goals (Mallik & McHale 1995). While the physiological and psychological impact of cardiac surgery interferes with patients' ability to make choices about their pain control, its presence does not alter their right to do so (Gaul 1990). Patient advocacy provides a means of transferring authority back to the patient (Hunt & Wainwright 1994). While implicitly endorsed throughout the U K C C ' s 'Code of Professional Conduct for

Complexity of pain assessment and management in first 24 h after cardiac surgery 299

the Nurse, Midwife and Health Visitor' (1992a) its application in clinical practice proves controversial. With reference to the management of post-operative pain, one must consider the realities of the role. While some assert the value of patient advocacy in pain management (McGuire 1994), Castledine (1981), with a focus on the inequality of the nurse-patient relationship in this situation, views patient advocacy as a nursing role as entirely inappropriate.

N U R S I N G R E S P O N S I B I L I T Y F O R B E N E F I C E N C E , A U T O N O M Y , E D U C A T I O N A N D I N F O R M E D C O N S E N T

Based on the principle of beneficence, the duty to benefit another or achieve good, the provi- sion of adequate pain relief becomes increas- ingly complex when attempting to determine the meaning of 'good' to the patient (Henkleman 1994). Indeed, each individual has not only a unique perception of pain but also desires a specific amount of pain relief (Scott 1994).

Using their own values and beliefs regarding pain, nurses frequently make inappropriate judgements of patients' pain levels (Porter 1991, East 1992). Seers (1987) found nurses' perceptions of patients' pain to be consistently underestimated, with disagreement between nurse and patient reports occurring 77% of the time. With the adequacy of pain management directly dependent upon an accurate assessment of pain (Scott 1994), these results represent a cause for concern. Contradicting the essence of the nurse-patient relationship, understanding, they emphasise the need to develop trust and mutual respect between the nurse and the patient (Burnard & Chapman 1988). Central to the concept of autonomy, these qualities pro- mote an individualised, effective approach to pain management.

Patient autonomy in health care demands the incorporation of health education into the nursing role (Albarran 1992). Tingle (1990) supports the provision of patient education, with particular reference to the legal issues surrounding informed consent. Legally, nurses are bound to ensure that patient consent is informed - that the implications of consent to or refusal of a given treatment are understood (Dimond 1990). With such knowledge, individuals' decisions are both informed and autonomous.

With ever increasing restrictions in clinical practice the adequacy of patient education may be questioned (Radcliffe 1993). Consent signed

under such circumstances raises questions about its validity which demand resolution in the realms of professional practice (Dimond 1990). Indeed, any exclusion of postoperative pain in pre-operative education contradicts the princi- ples of informed consent.

Education for individuals undergoing any procedure within the realms of cardiac surgery should include information regarding pre-pro- cedure preparation, the procedure itself, its benefits and potential complications as well as post-operative care (Radcliffe 1993). Pre- operative education is reported to decrease anxiety and subsequent pain perception, by preparing the patient for what is expected in the pre-operative, peri-operative and post- operative period (Kanto et al 1990). It is vital that such information includes both the bene- fits and potential side effects of any treatment.

Interestingly, controversy surrounds the benefits of pre-operative information. A study by Stovsky & Dragonette (1988) revealed that despite receiving information regarding the presence of an endotracheal tube and a subse- quent inability to speak, some patients could not recall this information postoperatively. In order that maximum benefit is obtained, infor- mation giving should be a two-way process, whereby a comprehensive history of each patient's previous pain experience, reactions to it and coping mechanisms is gained (Ferguson 1992). The exchange of information facilitates a greater preparation for postoperative pain management strategies for both the patient and the nurse.

While it is true that some of the responsibil- ity for optimising pain control lies with the patient (Closs 1990), many individuals maintain a strong belief in the power of others to control it. Indeed, an increasing focus on individual responsibility for health in health care today, neglects any consideration of those individuals who do not wish to accept responsibility for decisions regarding their health care (Eachus 1991). By virtue of its definition, responsibility is 'the ability of an individual to choose one course of action over another' as the correct choice in a given set of circumstances (Holden 1991, p398) appears largely inappropriate for individuals in the immediate post-operative period. Cerebral effects of cardiopulmonary bypass including temporary loss of concentra- tion, memory defects, confusion and disorien- tation (North 1988, Sang 1991) may make rational thought and responsible decisions virtually impossible at this time.

Many individuals are reluctant to report post-operative pain. A lack of pain expression does not necessarily indicate a lack of pain (East 1992, Hiscock 1993). Many people believe that admission of or complaints of pain are a sign of

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weakness and an inability to cope with the 'inevitable' consequences of surgery (Closs 1990, McGuire 1994). Such attitudes necessi- tate further emphasis on the role of nurses in accurate assessment and management of postoperative pain.

I N A D E Q U A C I E S OF N U R S I N G K N O W L E D G E

It is apparent from the literature that some nurses have insufficient pharmacological knowledge, with a resultant under-administra- tion of analgesics. Indeed, Saxey (1986) found that 77% (n=35) of nurses were unable to explain the mechanisms of action of narcotic analgesics. Nurses must be familiar with, and safe in the administration of, pharmacological methods of treatment (Younger 1993) so that pain management strategies are successful. Current reluctance to administer adequate doses of narcotics occurs as a result of nurses' undue concern with respiratory depression, addiction, tolerance and physical dependence on narcotic analgesics (Gujol 1994, Hollinworth 1994). Overestimation of the risks of respiratory depression and addiction are widely reported (Lavies 1992).

In postoperative cardiac care, analgesics may be kept to a minimum for patients requiring short-term ventilation, for fear of prolonging endotracheal intubation through respiratory depression (Wallace 1994). Patients requiring longer-term mechanical ventilation, where extubation is not an issue, are more likely to receive larger doses of analgesics (Gujol 1994).

Undeniably, opioids can cause respiratory depression. Acting on the brain-stem respi- ratory centres, they reduce responsiveness to increases in carbon dioxide tension. Ther- apeutic doses depress all phases of respiratory activity but rarely to any significant extent (Carr 1990). Respiratory depression has been known to occur in less than 1% of patients receiving analgesics (Porter 1991). It must also be remembered that respiratory depression is reversible with the use of par- enteral naloxone hydrochloride (an opiate antagonist) (McEvoy et al 1995), and that pain itself interferes with respiratory func- tion (Henkleman 1994).

Fear of addiction represents one of the greatest barriers to adequate pain control (McCaffery et al 1990) resulting in the avoid- ance of the administration of higher or more frequent doses of analgesics (Carr 1989). This fear is not restricted to the nursing profession, it appears that the general public also grossly exaggerate the risks of addiction (Miakowski

1993). Indeed, through fear of narcotic addic- tion some individuals refuse analgesics (McGuire 1994).

Documented research consistently shows that addiction is rarely a problem even for patients who receive large doses of opioids. Research revealing the percentage of patients who become addicted remains limited, but it is estimated that as few as 0.03% (n=3000) of patients are affected. Focusing on the addictive and harmful properties of analgesics, many individuals view themselves as having little or no control over their pain and are likely to assume a passive role in its management (Walding 1991).

Interestingly, nurses also have a tendency to assume a passive role in the management of post-operative pain (Briggs 1995). Frustrated by the fact that medical orders do not meet individual patients' needs, but rather represent the 'usual' order of the physician, they tend to play down the patients' pain (Leisifer 1990). Such inadequacies in the management of pain frequently occur as a result of a lack of under- standing surrounding both the consequences of unrelieved pain and actions of analgesics. The administration of narcotic analgesics in the post-operative period, for example, frequently results in a fall in blood pressure as the patients' pain is relieved (Wild 1992). Hypotension, often viewed as a direct effect of the opioid (Kitson 1994), occurs as pain and the associated sympathetic nervous system response abate, frequently revealing underlying fluid volume deficit (Wild 1992). Inadequacies in knowledge such as this inevitably restrict the administra- tion of narcotic analgesics in the post-operative period.

Research confirms that prescribed doses of analgesics are often less than half of that required to relieve patients' pain (Weis et al 1983). Persisting in the administration of analgesics according to personal interpreta- tion of the patients' pain, nurses frequently administer less than the already inadequate prescribed doses (Tittle 1994). With only 18% (n = 38) of physicians and 54% (n = 209) of nurses believing that they are adequately prepared for effective pain management (Lavies 1992), the need for further education in this area is evident (Carr 1990). Ultimately, the absence of accurate know- ledge surrounding the realms of postopera- tive pain management results in a continua- tion of ineffective pain management and continued, unnecessary patient suffering.

In current practice, health care professionals neglect their duty of non-maleficence, the duty to do no harm (Wallace 1994). Firmly en- trenched in the nursing ethic through the UKCC's 'Code of Professional Conduct'

Complexity of pain assessment and management in first 24 h after cardiac surgery 301

(1992a, Clause 2), the realities of this duty are highlighted when applied to the realms of pain management. Conflict surrounds the beneficial effects of relieving pain and the possibility of causing harmful effects such as respiratory depression and addiction. Ultimately, strategies must aim to achieve a comfortable balance between the two outcomes.

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CURRENT PRACTICES IN THREE CRITICAL CARE UNITS

Pharmacological treatment interventions

Current pharmacological techniques of pain relief include a multitude of treatments (Peat 1995). The critical care areas approached in this study advocated a combination of opioid anal- gesics, non-opioid analgesics and non-steroidal anti-inflarmnatory drugs as vital to effective pain management. Illustrating a move toward a more balanced approach to the achievement of analgesia, such combined approaches show recognition of the diversity of the pain experi- ence (Bromley 1993).

While recognising the value of a multi- modal pharmacological approach to postopera- tive pain management, one must also consider its implications for nurses. Such an approach demands a comprehensive pain assessment, combined with knowledgeable selection and administration of analgesics (Wild 1992). The UKCC's (1992b) 'Standard for the Admini- stration of Medicine' requires that all practi- tioners possess 'an understanding of substances used for therapeutic purposes'. With such knowledge, informed, accurate decisions re- garding analgesic requirements are made.

Utilised frequently in the care of post- operative cardiac patients, morphine appears the opioid of choice and the mainstay of analgesia in the immediate postoperative period (Wild 1992). While its precise mechanisms of action are unknown, morphine alters the perception of pain at the spinal cord with a resultant analgesic effect (McEvoy et al 1995). Despite its complex actions, including a number of varied side-effects, use of it follow- ing cardiac surgery appears entirely appropriate. While reducing myocardial oxygen consump- tion and workload it has little effect on heart rate or cardiac output (Wild 1992).

In the early postoperative period the use of opioid analgesics in combination with non- opioid analgesics proves more effective than that of opioids alone (McEvoy et al 1995). Non-opioid analgesics are most effective in the treatment of mild to moderate pain of non- visceral origin and represent an additional,

specific alternative for postoperative cardiac patients. However, it is vital that non-opioid analgesics (particularly paracetamol) are utilised correctly, with recognition of the potentially serious consequences of their side-effects (Younger 1993).

Similarly, compound analgesic preparations such as codydramol and coproxamol must be regarded with caution. They are utilised fre- quently in postoperative pain management, but their opioid content appears to cause side- effects, without any apparent increase in anal- gesic effect (McEvoy et al 1995).

The value of non-steroidal anti-inflamma- tory agents (NSAIAs), however, as part of a multi-modal approach to moderate or severe post-operative pain, is well documented (Kehlet & Dahl 1993). NSAIAs inhibit prostaglandin synthesis, modifying the inflammatory response and nociception (Wild 1992). But by virtue of their effect on prostaglandin synthesis, NSAIAs can affect renal function adversely (McEvoy et al 1995). They must be used with extreme cau- tion in postoperative cardiac patients, where acute alterations in renal function frequently occur following cardiopulmonary bypass (Girling 1990). NSAIAs also inhibit platelet aggregation, with resultant alterations in haemostasis (Souter et al 1994). While these side-effects are generally limited in the short- term use of the drugs, their significance in post- operative recovery cannot be ignored.

Despite the numerous side effects of NSAIAs, their use is becoming increasingly popular in pre-operative analgesic administra- tion (Peat 1995). Studies into the effÉcacy of pre-operative analgesia remain limited, but it is suggested that the pre-operative administration of NSAIAs decreases postoperative pain through the (previously established) inhibition ofprostaglandin synthesis (Coderre et al 1993).

While the value of a multi-modal (pharma- cological) approach to postoperative pain management is established, controversy surrounds the methods of administration. Current methods of opioid analgesic adminis- tration, including continuous intravenous (IV) infusion, bolus IV administration and patient- controlled analgesia (PCA), were identified by all three units where practice was reviewed during development of this paper.

Methods of opioid administration

While the administration of morphine by con- tinuous infusion was nominated as the 'pre- ferred method' in the three critical care units approached, the existence of other techniques in clinical practice indicates the necessity for a knowledge of their efficacy in the postoperative period.

302 Intensive and Critical Care Nursing

The references will follow in Part 2 of this article, which will appear in the next issue: 12(6): December.

Strong argument surrounds the administration of opioids by continuous infusion and IV bolus injection, and it appears that there is little differ- ence between the two in analgesic effect (Kehlet & Dahl 1993). However, since IV bolus tech- niques result in plasma concentration 'peaks' and 'valleys' (McCaffery 1987) and subsequent alter- ations in haemodynamic stability (Wild 1992), the value of continuous infusions following car- diac surgery emerges. Continuous IV opioid infusions minimise haemodynamic changes, while also providing a means of ongoing analge- sia for postoperative patients (Beuedetti 1990).

PCA has been strongly advocated for use in pain management following coronary artery bypass grafts (CABG) (Stanik 1991). Its use with alert, oriented and co-operative patients following surgery has proven beneficial (Aitken & Kenny 1990). Ultimately, however, the use of PCA in the immediate post-operative period may be impractical (Gould et al 1992), since the previously stated occurrence of disorienta- tion, confusion and loss of memory following cardiopulmonary bypass may make its use in the immediate postoperative period inappro- priate (Sang 1991).

In addition, many studies into the efficacy of PCA state criteria which exclude individuals with respiratory or cardiovascular disease, impaired renal function and infection (Bollish et al 1985). Such criteria raise questions about the use and indeed safety of PCA for patients after cardiac surgery. Ultimately, it appears that much of the benefit of PCA relates to the psychologi- cal aspects of pain relief (Lange et al 1988). Its use facilitates an increased sense of control for the patient, through decreased dependence on the nurse for pain relief (White 1988).

Non-pharmacologica l t r e a t m e n t intervent ions

Pharmacological interventions appear the pre- ferred and most frequently utilised method in

the treatment of post-operative pain, but many non-pharmacological therapies provide effec- tive relief (Dunn 1992, Buckle 1993). Inter- estingly, the three units approached in this study did not report use of any non-pharmaco- logical interventions in the treatment of post- operative pain. This is not necessarily a true indication of current practices however, as it is possible that responses were influenced by bias in the author's requests for information. Additionally, while complementary therapies are gaining acceptance within the realms of health care, their use remains secondary to medical treatment (Trevelyan 1993).

Including aromatherapy, massage, transcuta- neous nerve stimulation, music, relaxation techniques, biofeedback and stress manage- ment, complementary therapies offer an exten- sion to orthodox medical intervention (Caunt 1992, Booth 1993). The effects of aromather- apy massage for example, and a more conscious hands-on approach to patient care, offer psychological benefit to individuals following cardiac surgery (Stevensen 1994). It is also pos- tulated that A-Beta fibres involved in noci- ception, are activated by rubbing or massaging an area (Melzack 1973). This activation decreases noxious input to the brain by inhibit- ing noxious stimuli at the spinal cord.

Several approaches to pain relief are based on the concept of 'mind over matter'. Relaxation, distraction and, more recently, voice management strategies, aim to alter the psychological impact of the pain experience through a disruption of thought processes (Field 1995). Since such strategies result in increased patient comfort levels, decreased analgesic requirement and shorter hospital stays the value of complementary therapies appears obvious (Puntillo 1988). Ultimately, however, consistently appropriate implementation of treatment strategies cannot occur without a thorough and accurate assessment of each indi- vidual's pain.