Perioperative medicine: a changing model of care

Key points.

• •Perioperative medicine strives to meet the individual needs of complex patients through all stages of their surgical journey, providing a multidisciplinary ‘single point of contact’ team.
• •It uses the best available evidence to influence all stages of the patient pathway to improve perioperative outcomes.
• •Shared decision-making is key to patients understanding the importance of their values and preferences in care decisions.
• •The surgical pathway offers an opportunity for lifestyle modifications as the goal of surgery can act as a catalyst for positive behavioural change.
• •There has been a paradigm shift to an individualised, procedure-specific model of postoperative care.

Learning objectives.

By reading this article you should be able to:

• •Describe the philosophy underpinning perioperative medicine.
• •Discuss the available risk assessment measures and interventions as well as the evidence behind them.
• •Explain the necessary requirements and potential barriers to develop perioperative services within your own institution.

Perioperative medicine is a growing multidisciplinary subspecialty that has been driven by more complex surgical populations and advancing anaesthetic and surgical techniques. Although not exclusive to one specialty, it is led largely by anaesthetists, as they are well placed to undertake the role of the perioperative physician.¹ It is, however, a collaborative effort, that aims to provide an umbrella framework encompassing all aspects of the patient's surgical journey from the primary care setting through to full recovery at home; it also attempts to quantify the risks of the specific procedure for an individual. The standards of care are changing and a complete model does not yet exist; innovation of the service redesigns required is challenged by limited NHS budgets. There are, however, numerous examples of centres that have successfully implemented some of its key components utilising the best available evidence-based practice. This article will review the current and evolving strategies in perioperative medicine and how their implementation could improve outcomes and reduce healthcare costs.

Preoperative

Risk assessment

Risk assessment of the surgical patient is paramount to the underlying philosophy of perioperative medicine. It is essential to the process of shared decision-making and informed consent; and allows for preoperative patient optimisation and modification of the surgical pathway as required.

Patient comorbidities can be addressed before surgery and patients are given the opportunity to make necessary preoperative lifestyle and behavioural changes. It also provides a platform for shared patient knowledge and education between primary and secondary care providers when well executed.

Assessment of the risk can be achieved in a number of ways and combination of the different methods builds a more robust picture of the overall functional state of the patient. Methods to determine functional capacity include the following:

History

Assessment of self-reported effort tolerance to determine metabolic equivalents

Cardiopulmonary exercise testing

Exercise is a marker of the coupling of ‘external’ to ‘internal’ or mitochondrial respiration. Cardiopulmonary exercise testing (CPET) provides an individualised assessment of cardiorespiratory function and fitness by exercising patients on a bike ergometer. A treadmill or arm crank can be used, but these are tolerated less well by patients with musculoskeletal comorbidities and can pose a greater risk of falls. There are four key physiological stages: cardiodynamic, increased cellular respiration, steady state and incremental work phases. The test provides raw and derived data with the generation of nine-panel plot of data (Wasserman or Whipp) representing cardiovascular and ventilatory performance.² Anaerobic threshold, peak oxygen consumption (peak VO₂), and ventilatory equivalents (VE/VECO₂) variables have specifically been shown to be independent predictors of mortality, morbidity, and length of hospital stay.3, 4

Other exercise capacity tests

These include the shuttle test, the 6 minute walk test, and the stair climb test. While they are all relatively simple to perform, they are used less commonly in current practice and have not shown the same degree of sensitivity and specificity as CPET for perioperative outcomes.

Risk stratification tools

There are many available scores and models, though it is not established which score is the best predictor of risk. Scores need to be contextualised and their use is limited by their validity, relevance to the specific patient, and required input variables. Current commonly used scores include: P-POSSUM, Surgical Outcomes Risk Tool (SORT) and the Surgical Risk Calculator Score (ACS NSQIP).

Surgical pathways

Engagement with anaesthetists occurs relatively late in traditional surgical pathways. This significantly limits the ability to prepare patients adequately and affect changes in their decision-making, expectation, behaviour, and physiological reserve (through comorbidity management) in a collaborative way. Grocott and colleagues have proposed a redesign of the existing process with much earlier patient engagement and risk stratification, allowing effective triage and resource utilisation.⁵ Specialised clinics for high-risk individuals provide the opportunity for shared decision-making, whereby the risks and benefits of the proposed surgery can be comprehended fully by the patient within the context of their own lives. The concept of multidisciplinary ‘surgery schools’ that provide an interactive learning environment where patients can learn about their surgical journey and how they can influence it is also introduced (Fig. 1).⁵

Fig 1.

The pathway re-engineered—a model of process evolution in perioperative pathways. Adapted with permission from the original article.⁵ The original article is an open access article distributed under the terms of the creative commons attribution license. MDT, Multidisciplinary Team Meeting.

Prehabilitation

Prehabilitation refers to the multimodal process of improving a patient's functional status before surgery to enhance their body's ability to cope with a stressful event and therefore improve their postoperative outcome.⁶ It is a shift in focus towards the preoperative phase and requires ‘interaction’ with the perioperative team much earlier in the patient surgical pathway compared with the more traditional concept of ‘rehabilitation’, which focuses on postoperative interventions.⁷ Patients are thought to be more susceptible to change in the perioperative period. Prehabilitation utilises the theory of ‘marginal gains’, whereby a number of small interventions can bring about a reduction in morbidity and mortality; it includes structured exercise programmes, nutritional optimisation, psychological interventions, and lifestyle changes.8, 9 The ultimate aim is to build resilience and reserve in the physiological, physical, mental, and nutritional wellbeing of the patient in order to enhance the recovery process.⁴

Preoperative exercise

There is good evidence that exercise improves a patient's health and has preventative effects against many serious medical conditions. Preoperative exercise programmes aim to improve patient outcomes by enhancing the body's ability to withstand the surgical stress response. Reductions in morbidity, length of hospital stay, and quality of life have been reported in the literature, albeit in small numbers of patients.⁵ Exercise programmes that improve physical fitness through high intensity interval training alone or in combination with muscular strength training are deemed safe in patients with a spectrum of cardiorespiratory comorbidities. The optimal duration of exercise programmes tends to be driven by the specific patient pathway, but clinical improvements have been shown with programmes as short as 2 weeks. Objective assessment of improvement in fitness is most commonly assessed by CPET, as it currently has the largest base of supporting evidence. Successful set-up of structured exercise programmes is complex. They require the allocation of resources and can be challenging to coordinate between primary and secondary care. Hospital-based programmes are more costly, and centralising the service may lead to exclusion of patients depending on their home location. In contrast, community-based programmes are more likely to encounter problems with patient adherence. Failure to attend can be multifactorial. A holistic approach, providing an individualised plan in conjunction with behavioural and lifestyle modifications and understanding of the factors that influence a patient's attendance, is key to programme success. Incorporation of structured exercise programmes into existing enhanced recovery programmes needs consideration in the future.⁷

Nutritional optimisation

Malnutrition in patients presenting for surgery is often a direct result of the underlying disease process. It can be associated with muscle deconditioning, fatigue, impaired immunity, and poor wound healing. Studies have shown that providing preoperative nutrition for patients scheduled for gastrointestinal or cancer surgery patients reduces morbidity significantly.¹⁰ It is recognised that preventative rather than ‘reactive’ boosting of nutritional stores and general metabolic reserve can protect against the catabolic stress response of surgery. This optimisation should start as early as feasible in the perioperative process, and involvement of the patient is key to success. Enhanced recovery after surgery (ERAS) pathways have led the way with the use of clear fluid carbohydrate drinks in the immediate preoperative period to decrease the incidence of insulin resistance and postoperative hyperglycaemia, by replicating normal metabolic responses and endogenous insulin release.¹¹

Wischmeyer and colleagues on behalf of the American Society for Enhanced Recovery and Perioperative Quality Initiative 2 (POQI-2) released a joint consensus statement on nutrition screening and therapy within a surgical enhanced recovery pathway.¹² The need for routine preoperative screening to identify patients in need of nutritional optimisation was highlighted, as was the key role of oral nutritional supplements, protein delivery rather than total calorie delivery, and early initiation of postoperative nutrition.

Currently there are a few nutritional screening scores specific to the perioperative period and it is unclear which best predicts outcome. The Malnutrition Universal Screening Tool is most widely used to identify individuals at-risk. The POQI-2 Group have developed a simple and effective Perioperative Nutrition Screening Score to determine high-risk nutritional groups requiring referral to nutritionists for initiation of oral nutritional supplementation (Fig. 2).

Fig 2.

Perioperative Nutrition Screening Score (PONS) for preoperative nutrition screening. Figure reused with the permission of the POQI. Albumin 3.0 is in units of g dl⁻¹, which equates to 30 g L⁻¹. Pre-op, preoperative.

A Cochrane review showed significant reduction in postoperative complications with total parenteral nutrition. It is not without risk and is therefore currently reserved for when deficiencies in enteral nutrition exist. The effect on outcomes after surgery of immunonutrition (glutamine, arginine, omega-3 fatty acids), in combination with oral formulations, has also been investigated, regardless of baseline nutritional state.¹³

Psychological intervention

Anxiety is a major cause of psychological stress before surgery. It can affect outcomes, resulting in longer hospital stays, altered immune function, reduced wound healing, and worse functional recovery.⁷ If not adequately addressed, psychological stress can also impair motivation to engage in other prehabilitation interventions. Improving a patient's coping strategies through shared decision-making, provision of adequate information, and management of expectations can act as a motivator for behavioural change and positively influence patient recovery.

Lifestyle modifications

Smoking, obesity, and excessive alcohol use have all been associated with poorer outcomes after surgery. Stopping smoking for 4–8 weeks before surgery has been shown to significantly reduce pulmonary and wound complications.¹⁴ Equally, just 4 weeks of alcohol abstinence has been shown to decrease morbidity and shorten patient hospital stay.¹⁵ These ‘abstinence time-frames’ are achievable within existing surgical pathways and collaborative cessation programmes offer the opportunity for positive behavioural modification in the ‘teachable moment’ before surgery when patients are most susceptible to change.⁴

The key principles in weight management are early identification of individuals at the extreme ends of the weight spectrum who pose the greatest perioperative risk. The focus should be on the provision of targeted weight management programmes and nutritional support to optimise a patient's condition and pre-emptive interventions in primary care need to be fostered.

Evaluation of prehabilitation programmes

There is currently no consensus as to which interventions bring the greatest benefit to patients and cost savings to the NHS.¹⁶ Barriers include a lack of standardisation of programmes and heterogeneity of patient populations, the relative difference in timescale between optimal prehabilitation programmes and existing surgical pathways, and whether delays in surgical pathways are justified to allow for programmes to run in entirety. Future evaluation of prehabilitation programmes will need to incorporate outcome measures for both their implementation and effectiveness. Traditionally, 30-day mortality has been used as the marker of surgical outcomes, however there has been a paradigm shift towards longer-term patient-centred outcome measures that address functional performance and return to independent living, with the recognition that the recovery process is complex and multidimensional in nature. There are trials currently running in the UK looking at longer-term outcomes.⁴

Comorbidity management

Optimisation of patient comorbidities in preoperative clinics is another key component of improving patient outcomes. Patients can often be managed in ‘virtual clinics’ unless the patient requires specific hospital-based therapy.

Anaemia

Preoperative anaemia has been associated with increased perioperative transfusion requirements, morbidity, and mortality.¹⁷ The advent of ERAS pathways and patient blood management programmes has brought preoperative management of anaemia to the fore, and identification of patients in the primary care setting before referral is key. Traditionally, there has been significant variation between institutions over definitions and perioperative management of anaemia, but more recent expert consensus has indicated the need for correction of actual and functional iron deficiency and iron deficiency anaemia with oral or i.v. iron supplementation. There has also been recognition that previous classifications have traditionally undertreated non-pregnant women, resulting in increased transfusion rates. This is because they have proportionately higher blood losses when measured as a proportion of circulating blood volume compared with men.

The consensus statement has had several benefits including a reduction in the number of blood transfusions at a patient level, significant cost savings at an NHS level, and improvement in patient outcomes at a population level. A series of independent, collective, best practice evidence-based statements and management algorithms have been produced by Muñoz and colleagues in the ‘International consensus statement on the perioperative management of anaemia and iron deficiency’ to guide clinicians, and further evidence from larger clinical trials is awaited (Fig. 3).¹⁸

Fig 3.

Algorithm for the management of surgical patients. Adapted from the original article with the permission of the authors and Wiley & Sons Ltd.¹⁸

Frailty

The British Geriatrics Society defines frailty as ‘a distinctive health state related to the ageing process in which multiple body systems gradually lose their in-built reserves’. Frailty can be classified according to Fried's Physical Phenotype Model where the presence of three or more of the following criteria constitute frailty: weakness, slowness, low level of physical activity, unintentional weight loss, and self-reported exhaustion or Rockwood's Cumulative Deficit Index which ‘counts’ deficits accumulated over time in physical and cognitive domains, psychosocial risk factors, and geriatric syndromes. Both require time and skill to perform and interpret, and are not always practical. There are derived scoring systems for use in the perioperative setting but no consensus exists as to which is best.

As the average age of patients presenting for elective and emergency surgery continues to increase, frailty is increasingly being recognised as an independent risk factor for poorer postoperative outcomes.¹⁹ Diagnosis of frailty in preoperative clinics can help shared decision-making around perioperative risk and initiate multidisciplinary packages of care that optimise prehabilitation and rehabilitation, therefore reducing postoperative morbidity and mortality. The Proactive Care of Older People Undergoing Surgery Programme founded by consultants at Guy's and St. Thomas Foundation Trust is a dedicated service that aims to provide timely, individualised, protocol driven, multidisciplinary care for elderly surgical patients to maximise their chance of return to the premorbid state.

Diabetes

Diabetes affects 10–15% of the surgical population and is associated with increased complications, length of hospital stay, and mortality rates.

Perioperative management focuses on early identification of ‘at risk’ patients and concurrent optimisation of haemoglobin A_1c at the point of referral. Decisions about perioperative management regarding variable rate insulin infusions vs a period of starvation also need to be made. Diabetes nurse specialists play a key role in facilitating communication between clinical teams and the patient, and formulating perioperative management plans.

Type 2 diabetes has been recognised as a complication of weight gain and excess body fat and is not necessarily a permanent condition. The perioperative pathway can thus act as a unique catalyst for adopting lifestyle changes and engaging in weight management programmes in this particular patient group, as the goal of surgery provides the impetus for targeted weight loss and changes in dietary habits. The Diabetes Remission Clinical Trial (DiRECT Trial) demonstrated the ability for significant numbers of patients to achieve remission of Type 2 diabetes (with cessation of antidiabetic drugs) after intensive weight management within routine primary care.²⁰ This finding holds great significance for future management of Type 2 diabetes. Remission avoids the adverse effects of antidiabetic drugs, delays and or prevents end organ damage associated with the disease, and delivers significant cost savings to the NHS.

Intraoperative

Optimisation of anaesthesia

The WHO ‘Safer Surgery Saves Lives’ programme has been very successful in helping to drive patient safety and improve postoperative outcomes. There are established intraoperative interventions influencing patient quality of care including intra-operative normothermia, guided fluid management, minimisation of blood transfusions, and standardised packages of care such as enhanced recovery programmes. The relationship between intraoperative hypotension and depth of anaesthesia with postoperative outcomes is, however, less well defined. Evidence is emerging that they, too, are important influencing factors in poorer perioperative outcomes. Sessler and colleagues describe the ‘triple effect’ phenomenon whereby a low MAP in the presence of a low mean alveolar concentration and a low bi-spectral index value is an ominous predictor of morbidity and mortality.²¹

Intraoperative BP management in particular lacks standardisation and more multicentre randomised studies comparing BP strategies in high-risk surgical populations are needed.

Goal-directed therapy

With increasingly complex patients and surgical procedures goal-directed therapy (GDT) using haemodynamic monitors is fast becoming routine practice. A growing body of evidence has shown GDT results in a reduction in postoperative complications and length of hospital stay compared with standard fluid therapy. The key to the improvements in patient outcomes when GDT is used lies with the evidence-based algorithms rather than the specific type of monitor used. The use of liberal compared with restrictive fluid regimens in GDT has been researched extensively; it has highlighted the need for individualised GDT strategies to optimise fluid replacement and inotropic support, and therefore optimise haemodynamic stability and tissue perfusion.

Postoperative

Enhanced recovery programme

ERAS programmes are now widely established in many surgical subspecialties. These procedure-specific pathways, running from the preoperative period through to discharge provide ‘multimodal packages’ of perioperative care; these reduce variations in practice and improve the quality of care by adhering to a set of evidence-based standards which, when undertaken collectively, enhance a patient's recovery. Future developments are likely to focus on the longer-term effects on patient survival.²²

Postoperative management

There has been a paradigm shift away from the ‘reactive’ management of postoperative complications to a more pre-emptive model of postoperative care planning. Individualised patient plans made in the preoperative period with early appropriate referral to Critical Care Units are key and the use of risk assessment scores to quantify patient specific mortality have facilitated this process. The adoption of PACUs, as outlined in the Association of Anaesthetists' 2013 Safety Guideline, provide a safe and designated clinical area for more prolonged monitoring and intervention of patients after surgery. They serve to bridge the gap between critical care and ward care, and aim to facilitate the constant forward movement of patients as they transition into the postoperative period. Certain centres have also incorporated perioperative clinician teams into the daily follow-up of patients receiving ward-based care, until the point of discharge.

Pain management

Pain management planning should start before surgery to allow for early patient engagement, education, and appropriate postoperative care planning. Multimodal, opioid-sparing approaches have become standard practice; however there is a growing body of evidence that procedure-specific postoperative pain management protocols can improve pain management further by providing multidisciplinary, individualised plans that provide the balance between ERAS principles and optimal pain relief.

Postoperative cognitive dysfunction

Postoperative cognitive dysfunction (POCD) was originally described in patients after cardiac surgery; however, it is now a recognised phenomenon in other surgical patients. The exact aetiology is unknown although mechanisms have been postulated. It is likely to be multifactorial in origin with both non-modifiable (age, pre-existing cognitive impairment, comorbidities, level of education) and modifiable risk factors (perioperative complications).²³

POCD is commonly described as an acute deterioration in cognitive processing, memory, and executive function after surgery that usually lasts a few days to weeks, but may persist for several months. In some cases it can impact on longer-term socioeconomic status and quality of life. It is clinically distinct from delirium and dementia, although they can exist together which can make diagnosis challenging. In addition, the more complex neurocognitive testing required for diagnostic purposes is not always practical. Frailty scoring has been used as a surrogate for risk of POCD, as they share common risk factors.

It is unclear exactly how anaesthesia affects POCD. The focus is currently on prevention strategies to reduce incidence through identification of modifiable risk factors including avoidance of psychoactive medications, balanced anaesthetic technique, early active re-orientation in recovery, treatment of delirium, and postoperative cognitive rehabilitation. Consent of the high-risk patient is complicated by the lack of precise diagnostic criteria, disease incidence statistics, and available treatment options; however an appropriate discussion should be undertaken.

Conclusion

Perioperative medicine is a growing and evolving field that places patient outcome at its core. It aims to build a patient's physical, physiological, and emotional resilience to the surgical stress response through engagement and intervention at all steps in the surgical pathway. The complete model of care does not yet exist and further research as to best practice is ongoing. As more evidence becomes available, the package of ‘best practice care’ can be shaped and standardised to reduce inequalities between institutions. There are, however, some excellent examples of centres already providing components of this multidisciplinary, holistic package of care with promising results. The challenge going forward will be innovation and development of services within the current economic constraints of the NHS.

Declaration of interest

The authors declare that they have no conflicts of interest.

MCQs

The associated MCQs (to support CME/CPD activity) will be accessible at www.bjaed.org/cme/home by subscribers to BJA Education.

Biographies

Jeanne Louise Schonborn FRCA is a specialist trainee in anaesthesia and is currently undertaking a fellowship in perioperative medicine at Torbay and South Devon NHS Trust.

Helen Anderson FCARCSI is a consultant anaesthetist and lead for perioperative medicine at Plymouth University Hospital NHS Trust. She is Honorary Secretary of the Perioperative Exercise Testing and Training Society (POETTS).

Matrix codes, 1H02, 2A07, 3I00