When considering “risks,” “complications,” or “consequences” associated with ICU stays, it is important to recognize that some of the most difficult and complex cases and surgical problems that can arise are managed by ICU staff. Risks can still be reduced, and substantial advances are being continuously made to improve the situation. Despite this, morbidity and mortality remain high in relative terms for patients admitted to ICU.

The purpose of this chapter is to raise awareness of the potential problems that can occur in ICU patients of differing types in order to predict and potentially act to avert complications from arising. This may also prevent a “chain” of other complications from arising and so maximize potential reversibility and recovery. The best intensive care treatment is often a matter of simply and safely supporting the patient through the problems that can arise postoperatively. If complications are averted in this critical period, the patient stands an excellent chance of success in the longer term.

It is on this broad understanding and background that the following chapter is written.

Admission of surgical patients to ICU may be elective or planned, or it may occur as an emergency admission following surgical or anesthetic complication or progression of the underlying condition. Admissions may sometimes be preoperative for surgical optimization but are usually postoperative in order to avert, detect, monitor, and manage pathological and physiologic aberrations and organ failures and to improve morbidity and mortality. This support often means patients survive when they may not have in the past or can undergo more “dangerous” surgery than previously was possible. For many others, this support may help to avoid or curtail complications of their surgery, underlying surgical condition, and medical comorbidities.

Many elective admissions to the intensive care unit (ICU) are relatively short term and are not associated with significant complications. The elective nature means these patients should be informed and consented for their ICU admission. However, some admissions may be more prolonged and are associated with exposure to higher risks; many of these may not be predicted. It is useful to warn patients and relatives preoperatively of the possibility of an ICU admission, to prepare them and avoid unnecessary anxiety. In the event of unplanned ICU admission and support, informed consent is often not possible or practicable. In any case clear and ongoing communication with the patient and/or family is essential.

Complications associated with intensive care for surgical patients may be categorized as:

Many complications associated with ICU support are a consequence of the preexisting comorbidities and acute pathology that a patient has, together with the type and complexity of the surgical procedure performed. In addition, significant comorbidities and the performance of complex surgery are associated with increased risk of complications, which often necessitate or prolong an ICU stay. This inevitably exposes these patients to a greater risk of complications resulting directly from intensive care itself. For example, prolongation of the ICU stay increases the risks from immobility, sedation, nosocomial infection, and utilization of long-term indwelling devices for ventilation, vascular access, monitoring, nutrition, or drainage.

Given the broad range of surgical patients and conditions, therapies, and procedures undertaken in ICU, complications are common and diverse. This chapter will outline some of the important complications more specifically to intensive care. Although it is easier to consider these within individual organ systems as we do here, complications encountered in ICU patients often coexist and are frequently additive. Increasing numbers of organ system failures have been clearly shown to increase mortality and morbidity.

Critical illness itself frequently leads to central and peripheral neurologic complications (Barlas et al. 2001). These complications may also arise from a constellation of ICU procedures and therapy, medical or surgical conditions, or simply an underlying primary neurologic disease. Such complications may go unrecognized, as critically ill patients are often intubated, sedated, and/or receiving neuromuscular-blocking agents. Encephalopathy remains the most common neurologic complication in ICU and is usually multifactorial in origin. Sepsis is the condition with the highest incidence of neurologic complications. Severe weakness termed “critical illness polymyoneuropathy” is another frequent complication of critical illness and its treatment. Neurologic complications are associated with increased disability, longer hospital stay, and increased mortality. Minor neural deficits may go entirely unnoticed due to the subtle nature of many of these, such that the range and frequency of neurologic complications is often underreported and underappreciated but may be discernable to those who know the patient well, for example, family members or close friends, who may notice cognitive impairment(s). If fact, the more we study these post-ICU patients, especially the severely unwell and prolonged stay cases, the more appreciation we are gaining for the more subtle deficits that are acquired, either by the disease(s), the ICU care, or both. Avoidance of hypotension, to preserve cerebral perfusion, where possible, is a major factor in averting this range of complications. Of course, the scope of neurologic deficits, especially the more minor ones, needs to be sensibly balanced against the often higher risks from not admitting the patient to ICU. See Table 6.1.

Some complications are associated with the procedure and anesthetic required to intubate or extubate a patient’s trachea (Table 6.2), drain pleural spaces, or create a tracheostomy in ICU patients. However, the most frequent complications are associated with invasive ventilation, and the risk increases with time duration on mechanical ventilation. Significant complications include (Figs. 6.1 and 6.2):

Cardiovascular monitoring and support is a common reason for a surgical patient to require ICU care. One-third of all postoperative complications and more than half of the deaths are due to cardiac complications (Devereaux et al. 2005a). Up to 50 % of perioperative myocardial infarctions (MIs) may be unrecognized, if physicians rely solely on clinical symptoms and signs (Devereaux et al. 2005b); 15–25 % of patients experiencing a MI following noncardiac surgery die during that admission. Furthermore, while in ICU patients may suffer complications of underlying cardiac disease brought on by the stressed and critically ill state, such as decompensated heart failure or acute myocardial ischemia. Even in the absence of underlying cardiac disease, cardiac function is often depressed in patients with severe sepsis and other multiorgan dysfunction syndromes. Some echocardiographic studies suggest up to half of patients with prolonged septic shock develop myocardial depression (defined by reduced ejection fraction) and that 25 % of septic patients without shock have impaired ventricular function (Rudiger and Singer 2007). Many of the other complications in ICU relate to drugs and procedures that either impair cardiac function or contribute to arrhythmias. Some examples include:

The kidneys normally require about 20 % of cardiac output and perfusion with blood at about 400 ml/min/100 g (kidney) in normal states and are highly sensitive to low cardiac output, low mean arterial pressure, and hypoxia. These conditions often contribute to the renal dysfunction and failure, commonly encountered in surgical patients in ICU. In approximately 6 % of ICU patients, this can be severe enough to require renal replacement therapy (dialysis) (Bagshaw et al. 2008; Uchino et al. 2005). Development of acute renal failure in ICU is associated with a mortality ranging from 50 to 70 %, especially when requiring dialysis or associated with other organ failures (Brivet et al, 1996; Briglia and Paganini 1999). Of the survivors, 5–20 % remain dialysis dependent at hospital discharge (Hoste and Schurgers 2008). Sepsis, burns, trauma, and acute respiratory failure often result in renal failure. Although usually multifactorial, the most frequent causes of renal failure in surgical ICU patients are shock, aminoglycoside therapy, and intravenous contrast media. Other conditions and therapies in ICU further contribute to the burden of renal complications. Methods for preventing or treating acute renal failure remain unclear; however, it is important to maintain circulation and to avoid the use of nephrotoxic substances such as contrast media, aminoglycosides, and nonsteroidal anti-inflammatory drugs. The concentration of these drugs should be measured and perhaps avoided or alternatives chosen, if possible. Renal replacement therapies (most commonly hemofiltration and/or hemodialysis) are delivered in ICU when required but have specific complications particularly associated with vascular access catheters and extracorporeal circuits. Some important and common complications include:

Hepatobiliary problems occur during the treatment of other systemic disorders in ICU and are frequent sequelae of sepsis, shock, and cardiac low-flow states. Although hepatic problems are principally either prehepatic, intrahepatic (hepatocellular), or posthepatic (cholestatic), in practice and in serious unwell ICU patient, mixed etiologies are usual. Unless the primary problem is with the liver, hepatic dysfunction usually corrects if the underlying problem (e.g., sepsis or shock) is corrected.

Examples of types and causes include:

Nutrition is important for ICU survival and surgical recovery. Intravenous (total parenteral) nutrition has been shown for years to be inferior to enteric feeding and associated with greater complications (Moore et al. 1992). When gastrointestinal complications occur, as they frequently do in ICU patients, not only is the gut itself compromised, but so too is the ability for the patient to receive sufficient enteral nutrition.

Diagnosis of any gastrointestinal complication is often difficult and delayed due to paucity of signs and reported symptoms (often due to sedation and analgesia) in the ICU patient. Although gastrointestinal bleeding (GIB) is common (up to 91 % of some ICU patient groups) (Peura and Johnson 1985), overt bleeding requiring transfusion occurs in only 1–2 % (Cook et al. 1996). This must be weighed against the risk and cost of prophylaxis with gastric acid suppression, which is expensive; contributes to bacterial colonization of the upper GI tract; is associated with increased incidence of ventilator-acquired pneumonia; and can interact with other medications. Enteral feeding reduces the incidence of GIB while providing nutrition and maintaining bowel mucosal integrity so should be given early to all patients without a contraindication.

Common GI complications include:

Regulatory functions of the body are commonly impacted by the stresses of surgery and critical illness. As such, metabolic and endocrine abnormalities are frequently present on admission and during ICU admissions. Although the clinical significance of some of these conditions remains to be understood, many, such as hyperglycemia, have been shown to be associated with morbidity and mortality (Wah Cheung et al. 2005), so detection and treatment is important. Some of the more common abnormalities include: