Perioperative and intensive care management of the surgical patient

Introduction

The incidence of death directly attributable to anaesthesia has decreased significantly over the last 60 years. In the 1950s, several studies demonstrated that the postoperative mortality solely associated with anaesthesia was approximately 1 in 2500, ^1–3 but by 1987, in the UK Confidential Enquiry into Perioperative Death (CEPOD), this had decreased to an estimate of 1:185000. Whilst anaesthetic practice has continued to evolve over the subsequent 30 years, the marginal improvements in mortality have been likely offset by an increasingly fragile and elderly group of patients who are now operated on, leaving the underlying rate of death attributable to anaesthesia much the same.

Although deaths as a direct consequence of anaesthesia are relatively rare, the rate of morbidity and mortality following major surgery remains much higher. The European Surgical Outcomes Study in 2012 (EuSOS) found an overall mortality rate of 4% in patients undergoing non-cardiac surgery throughout Europe. These findings have been replicated globally, highlighting the need for safe perioperative care. This chapter deals with the perioperative and intensive care management of these patients with a specific focus on how to ensure that each patient has adequate cardiovascular performance for their needs during the perioperative period, in order to reduce their risk of complications and death.

Postoperative critical care is a key factor in the improvement of outcome for surgical patients, particularly those who are at high risk of postoperative morbidity and mortality. Thus, postoperative critical care admission should always be considered when the preoperative physiological condition of the patient in tandem with the planned complexity of the surgical procedure suggests that there is a reasonable risk of postoperative complications and organ dysfunction. In order to provide this postoperative critical care, it is necessary to be able to identify these high-risk patients preoperatively.

How big is the problem?

It is estimated that over 300 million operations take place globally per year and these growing numbers of patients need to be cared for in an appropriate setting. A high-risk group of patients was identified from the UK population who accounted for over 80% of all deaths but only 12.5% of procedures. Despite high mortality rates, fewer than 15% of these patients were admitted to the intensive care unit (ICU), and the highest mortality rate (39%) was found in patients who required ICU admission following initial care in a ward environment. These findings have been confirmed, with only 5% of all patients being admitted to ICU electively after their procedure. Unplanned admissions were associated with higher mortality, and 73% of those who died were not admitted to ICU at any stage. Admission to critical care following surgery is most common in patients who are elderly, have a high body mass index, have comorbid clinical conditions or require emergency surgery.

Despite this, there continues to be a problem with the allocation of critical care resources to those most in need following elective surgery. However, as also exposed by the 2020 SARS-CoV2 pandemic, the availability of critical care beds remains limited, with an average of 2.8 critical care beds per 100 acute care beds across Europe. This varies considerably between countries, with Germany having 6.9 times the number of critical care beds per head of population that Portugal has. Studies have demonstrated the paucity of both ICU and high-dependency unit (HDU) beds in the UK and found that patients were often admitted later and with worse severity of illness. This mismatch between the need/demand for postoperative critical care and the capacity to deliver it has been recently exposed during the COVID-19 pandemic with the shutting down of surgical services to prioritise the urgent and emergency care pathways resulting in a very significant surgical backlog on the waiting list.

Repeated publications by the NCEPOD have cited inadequate preoperative preparation, inappropriate intraoperative monitoring and poor postoperative care as contributing causes of perioperative mortality. ^{, ,} The NCEPOD report ( Knowing the Risk ) suggests that patients in the UK often die after surgery because they are not given the level of care they are entitled to or could reasonably expect. In this report, less than half of the patients received the care that the advisors felt was the minimally acceptable standard. Predicting which patients will most likely benefit from admission to intensive care is hugely complex and is fraught with difficulties. The significant variation in these patients’ underlying pathology and premorbid physiology makes it very difficult to provide hard-and-fast rules as to which patients will benefit from perioperative admission to either ICUs or HDUs.

Why do patients die after surgery?

Major surgery is associated with a significant stress response vital for the body to recover and heal from the surgical trauma. This response manifests in many different ways, but a typical delineating pattern is hyperdynamic circulation with increased oxygen requirements postoperatively. If the body is unable to increase the cardiac output in response to the surgical stress, then the increased need for oxygen cannot be met, and the patient develops tissue dysoxia and cellular dysfunction. This has been described by some authors as an acquired oxygen debt which if left, results in organ failure and death. The important point to recognise is that the normal response to surgery is to increase the cardiac output and the delivery of oxygen to the tissues. Any patient who, for whatever reason, is unable to develop this response is at higher risk of subsequent complications.

What is a high-risk surgical patient?

The challenge is the early identification of patients who are at a high risk of postoperative complications and death, and this is vital to ensure that correct care and therapy are initiated at an optimal time. Patients admitted to ICU following a postoperative complication tend to experience worse outcomes. A recent systematic review has identified that age, anaemia, American Society of Anesthesiologists (ASA) grade, body mass index, extent of comorbidity, emergency and high-risk surgery, male sex, sleep apnoea, increased blood loss and operative duration are all independent risk factors for unplanned critical care admission. Given these are mostly known preoperatively, resource planning should be done in a pre-emptive manner.

Overall, this patient group is characterised by undergoing major surgery whilst having concurrent medical illnesses that limit their physiological reserve to compensate for the stressful situation. Patient assessment of surgical risk is discussed in detail in Chapter 4 .

Individualised clinical risk interpretation is challenging, although the use of well-validated risk assessment scores such as P-POSSUM is commonly used to mediate this variability, inform shared decision-making with patients, and guide further preoperative assessment. It has been suggested that elective surgical patients can be assessed by cardiopulmonary exercise testing, ^{, ,} in which a strong correlation has been demonstrated between anaerobic threshold and postoperative outcome. The anaerobic threshold is the point where aerobic metabolism fails to provide adequate adenosine triphosphate and anaerobic metabolism starts to reduce the resultant deficit. The threshold is determined by monitoring inhaled and exhaled levels of oxygen and carbon dioxide during escalating levels of exercise. This provides an objective measure of physiological reserve. However, it must be remembered that complex cardiopulmonary testing in patients who have established poor cardiorespiratory reserve is only of use if used to target preoperative preparation and these patients must have specific optimisation of their comorbidities prior to surgery whenever possible. This requires that patients booked for elective surgery have all their comorbidities treated and investigated to ensure best possible physiological status prior to surgery. This is also the opportunity to consider if surgical intervention is the best course of action in view of the risk of the potential adverse outcomes. A complete and truthful risk assessment should be undertaken and the patient fully involved in the decision to proceed to surgery. A national report published in 2011 suggested that only 7.5% of patients at high risk of death or severe complications were given any indication of their risks of mortality and morbidity prior to surgery. It is now regarded as a minimum standard of care to provide each patient with an individualised risk estimation and document this clearly in the clinical records.