Infection in the critically ill surgical patient

After surgery, critically ill patients in the intensive care unit (ICU) may acquire infections which differ from those acquired elsewhere with regard to the anatomical site involved and the causative micro-organisms. Specific risk factors for infection in the ICU have been shown to be associated with exposure to invasive devices and the use of broad-spectrum antibiotic treatment. Control of infection depends on the timely suspicion of its presence and the identification of the potential anatomical source of infection. Furthermore, the collection of adequate fluid samples for cultures before any anti-microbial treatment is introduced is paramount in order to identify responsible microbes correctly and to re-adjust therapy subsequently. It should be stressed that, when empirical anti-microbial therapy is started before micro-organism identification, the initial treatment will be appropriate only in half of the cases. Gram-negative bacteria of the Pseudomonas aeruginosa and Enterobacter cloaca strains remain the leading cause of nosocomial infection in the ICU. Other pathogens which have caused concern in ICU patients over the past decade are Staphylococcus aureus and fungal infection mainly of theCandida spp.This chapter reviews the more common infections encountered in the high-risk surgical patients in the ICU according to the anatomical localization of the infection, i.e. respiratory, abdominal, urinary, wound and bloodstream infections.     

Lymphocyte function in the critically ill surgical patient

Lymphocyte function is commonly altered in critical ill surgical patients. There is controversy whether or not formation of antibodies is impaired; however, cellular immune responses are routinely depressed. Patients who have suffered major surgical or accidental trauma or burns frequently become anergic. Their lymphocytes respond poorly to mitogenic or antigenic stimulation, and serum factors suppressive of lymphocyte activation appear. Mechanisms underlying these abnormalities remain to be defined.     

Acute renal failure and the critically ill surgical patient

Acute renal failure can occur following major surgery. Predisposing factors include massive haemorrhage, sepsis, diabetes, hypertension, cardiac disease, peripheral vascular disease, chronic renal impairment and age. Understanding epidemiology, aetiology and pathophysiology can aid effective diagnosis and management. A consensus definition for acute renal failure has recently been developed. It relates to deteriorating urine output, serum creatinine and glomerular filtration rate. In the surgical patient, precipitants are often pre-renal, although intrinsic damage and obstructed urine flow can occur. Worsening renal function results in distal organ damage. Acute renal failure is a marker of disease severity, carrying a poor prognosis if associated with deteriorating respiratory and cardiovascular function. Acute renal failure in the critically ill surgical patient exerts a massive impact on the evolution of complications and prognosis. Management relates to treating life-threatening problems, maintaining effective ventilation and circulation, removal (or reduction) of nephrotoxins and, where appropriate, establishing either renal replacement therapy or palliative care.     

Immunologic mechanisms underlying sepsis in the critically ill surgical patient

This article describes the range of immunologic abnormalities that follows accidental and operative trauma. The high rate of infection in critically ill postoperative patients may result from these abnormalities in host defense function. Means to recognize and correct the post-trauma immune deficiencies are discussed.     

The Bengmark tube in surgical practice and in the critically ill patient

Enteral nutrition (EN) is increasingly used to minimize the rate of septic complications related to bacterial translocation, due to its effectiveness and low cost. Bengmark's self-propelling auto-positioning feeding tube (SPT) absorbs and uses gut motility for rapid transport to the upper small intestine, thereby allowing uninterrupted EN both in surgical and critically ill patients. We report on our experience with 175 SPTs applied over the period from December 1996 to February 2000, and analyse the safety, compliance, and indications of SPT in surgical and ICU practice. Open study: feasibility of insertion, time and rate of placement, compliance and complications related to the tube or to EN were studied. SPTs were successfully placed in 40 patients before liver resection, in 32 patients before extensive maxillo-facial surgery MFS and prior to colon resections in 10 cases. SPTs were also applied in 56 patients with acute vascular neurological diseases, 22 in pancreatic diseases and in another 15 critically ill patients. 92.5% of SPT's crossed the pylorus, while only 7.5% stopped in the stomach and 3.4% in the duodenum; 89.14% reached the first jejunal loop. The tip of the tube reached its final position within a mean period of 5.2 hours, 8% instantly and all within 24 hours. Enteral nutrition was started immediately after introduction of the tube into the stomach. The compliance was excellent, even in maxillo-facial surgery patients: only 2/76 patients (2.6%) showed poor compliance. There were no cases of aspiration pneumonia or other complications related to SPT. Polymeric nutrition was usually supplied at a starting flow rate of 45 ml/hour and rapidly increasing over the following 48 h. Eleven patients experienced diarrhoea and 6 abdominal distension, leading to a temporary reduction of the EN flow rate. Clogging of the SPT occurred in 13 patients: 7/13 were cleansed with pancreatic enzymes, but 6 had to be replaced. SPT is ideal for intensive EN and is characterised by minimal complications and excellent patient compliance.     

Dyslipidemia in the critically ill patient

Dyslipidemia seen in the critically ill patient is a common disturbance, poorly recognized by physicians in this setting. Shock states, sepsis, multifactorial systemic inflammatory response syndrome and ischemia-reperfusion injury are associated with important metabolic changes that contribute to this disturbance. As a result, the lipid concentration, including cholesterol, high-density lipoproteins and apo-lipoprotein A-I, diminishes. Previous reports correlate the disturbance in lipids with a higher risk of infection, systemic inflammatory response syndrome, multiple organic dysfunction syndrome, and raised mortality. The use of reconstituted high-density lipoprotein may be a therapeutic alternative for the management of this entity.     

Nutrition in the critically ill patient

Critically ill patients are hypermetabolic and have increased nutrient requirements. Although it is assumed that nutritional support is beneficial in this group of patients there are no well designed clinical trials to test this hypothesis. The rationale for nutritional support, therefore, is based upon clinical judgement. Although it is not known how long a critically ill patient can tolerate what is effectively starvation, the loss of lean tissue which occurs in catabolic patients (20-40 g nitrogen/day) suggests that depletion to a critical level may occur after 14 days. Total parenteral nutrition given to malnourished patients with gastrointestinal cancer for 7 to 10 days before surgery has been shown to decrease complications by about 10%. Wound healing and normal immune responses are dependent upon adequate nutrient intake, and it seems reasonable, therefore, to commence feeding as soon as possible. Earlier feeding may decrease length of stay and complication rates in both critically ill patients and following surgery. It has been shown in randomised controlled trials of both enteral and parenteral feeding in the critically ill, that current regimens are sub-optimal. Calorie intake was shown to be often considerably in excess of metabolic requirements alone, and variable study design has made comparisons impossible. Despite the lack of knowledge regarding even the most simple of nutritional requirements in these patients, the administration of specific micronutrients and specialised supplements has attracted attention. Again, many of these more recent studies are limited because of poor study design.     

Sedation in the critically ill patient

The goal of critical care medicine is to support organ function and maintain homeostasis until healing can occur. Sedation and analgesia may blunt the physiologic and psychologic sequelae of intensive care unit stress, and support homeostasis. Although a wide variety of agents have been used empirically, the recognition of analgesia, amnesia, and hypnosis as discrete elements comprising the sedated state has facilitated an individualized approach to therapy. Because intensive care unit patients are a highly heterogeneous population with varying levels of end-organ compromise, the development of specific, easily titratable, parenteral agents has made intensive care unit sedation safer. A trend toward refining dosage regimens in order to minimize the total dose of drug administered and to reduce the occurrence of residual sedation is driven by utilization and cost concerns. The capability for simple bedside electrophysiologic monitoring of the level of sedation is expected to improve the ability to provide optimal therapy.     

Pain in the critically ill patient

The intensive care unit (ICU) presents a unique environment for the assessment and treatment of pain, given the potential compromise of both the patients’ physiologic stability and communication skills secondary to underlying disease processes. These present special challenges to clinicians that may not be seen in other arenas of pain control. The typical patient in the ICU may not be able to communicate with the nursing or physician staff his/her discomfort due to the level of discomfort caused by either the severity of the disease or impediments to communication. The problem of pain control in those patients in the ICU has been clearly documented. This may be partially due to the difficulty in assessing how much pain a critically ill patient, who may be obtunded secondary to the underlying disease process or physiologically compromised by a process, such as sepsis or shock, is having. Thus, patients who cannot verbalize pain may need more creative techniques of pain assessment, as well as an increased vigilance by both the physician and nursing staff to maintain an awareness of pain issues. Patients in the ICU, who typically may be intubated or are at higher risk for pulmonary complications, may especially be vulnerable to increased levels of pain after surgery. There are many options for pain control in these patients, including epidural analgesia, intrapleural analgesia, intravenous patient-controlled analgesia, and intercostal nerve blockade. In addition, organizational changes may improve pain control in the ICU.     

Monitoring the critically ill patient

It has long been recognised that the physiological response of the patient to a stress or disease process will very largely determine the outcome. It is important, therefore, to monitor the physiological responses of patients since this not only allows the assessment of physiological reserve but will also give a baseline against which the effectiveness of any applied treatment can be judged. Basic knowledge of the principles of monitoring and correct interpretation of data is important since a failure to do so can result in misdirected therapy. Much of what will be discussed in this review revolves around the maintenance of normal aerobic metabolism and thus maintenance of viable cell function and measurement of the degree of tissue oxygenation. Reduced supply of oxygen over demand for oxygen results in cell injury and organ dysfunction. Only by assessing this dysfunction can appropriate modifications of therapy be undertaken.     

Recognizing the critically ill patient

Critical illness is a life-threatening multisystem process that can result in significant morbidity or mortality. In most patients, critical illness is preceded by a period of physiological deterioration; but evidence suggests that the early signs of this are frequently missed. All clinical staff have an important role to play in implementing an effective ‘Chain of Response’ that includes accurate recording and documentation of vital signs, recognition and interpretation of abnormal values, patient assessment and appropriate intervention. Early-warning systems are an important part of this and can help identify patients at risk of deterioration and serious adverse events. Assessment of the critically ill patient should be undertaken by an appropriately trained clinician and follow a structured ABCDE (airway, breathing, circulation, disability and exposure) format. This facilitates correction of life-threatening problems by priority and provides a standardized approach between professionals. Good outcomes rely on rapid identification, diagnosis and definitive treatment and all doctors should possess the skills to recognize the critically ill patient and instigate appropriate initial management.     

Sedation in the critically ill patient

Critically ill patients who require intensive care need effective analgesia and sedation to control potentially unpleasant symptoms, such as pain and anxiety. Analgesics and sedatives are also used to allow patients to tolerate nursing procedures and tracheal intubation as well as to aid mechanical ventilation. Metabolism of traditional opioids is dependent on organ function, which is abnormal among critically ill patients. The use of a score system to ensure sufficient but not excessive sedation should be mandatory. Sufentanil and remifentanil are more predictable opioids that are suitable for either sedation or analgesia in critically ill patients to achieve an adequate Ramsay score from 2 to 4.