Multiple Organ Dysfunction Syndrome in Sepsis Workup

Laboratory tests are useful in cases of suspected sepsis or septic shock to assess the general hematologic and metabolic condition of the patient. The microbiologic studies provide results that may indicate occult bacterial infection or bacteremia and identify the causative pathogen or pathogens.

Various imaging modalities are employed to diagnose clinically suspected focal infection, detect the presence of a clinically occult focal infection, and evaluate complications of sepsis and septic shock.

In patients with severe sepsis, a chest radiograph should be obtained because the clinical examination is unreliable for diagnosing pneumonia. Clinically occult infiltrates have been detected by routine use of chest radiography in adults who are febrile without localizing symptoms or signs and in patients who are febrile and neutropenic without pulmonary symptoms. Supine and upright or lateral decubitus abdominal films may be useful when an intra-abdominal source is suspected.

Ultrasonography is the imaging modality of choice when a biliary tract infection is suspected of being the source of sepsis.

Computed tomography (CT) is the imaging modality of choice for excluding an intra-abdominal abscess or a retroperitoneal source of infection. A CT scan of the head should be obtained when there is evidence of increased intracranial pressure (papilledema), when factors suggesting focal mass lesions (eg, focal defects, previous sinusitis or otitis, recent intracranial surgery) are present, or before lumbar puncture (LP) when meningitis is suspected.

When clinical evidence of a deep soft tissue infection exists (eg, crepitus, bullae, hemorrhage, or a foul-smelling exudate), a plain radiograph should be obtained. The presence of soft tissue gas and the spread of infection beyond the clinically detectable disease may necessitate surgical exploration.

A complete blood cell (CBC) count with differential should be obtained. An adequate hemoglobin concentration is necessary to ensure oxygen delivery in shock; hemoglobin should be maintained at a level of 8 g/dL.

Acute-phase reactants and platelets usually increase at the onset of any serious stress. With persistent sepsis, the platelet count will fall, and disseminated intravascular coagulation (DIC) may develop.

The white blood cell (WBC) differential and the WBC count may predict the existence of a bacterial infection. In adults who are febrile, a WBC count higher than 15,000/µL or a neutrophil band count higher than 1500/µL is associated with a high likelihood of bacterial infection. ^[19]

A metabolic assessment should be performed with measurement of serum electrolytes, including magnesium, calcium, phosphate, and glucose, at regular intervals. Renal and hepatic function should be assessed with measurement of serum creatinine, blood urea nitrogen (BUN), bilirubin, alkaline phosphate, and alanine aminotransferase (ALT).

Arterial blood gas testing is indicated.

Measurement of serum lactate provides an assessment of tissue hypoperfusion. Elevated serum lactate indicates that significant tissue hypoperfusion exists with the shift from aerobic to anaerobic metabolism. This signals a worse degree of shock and a higher mortality.

Coagulation status should by assessed by measuring the prothrombin time (PT) and the activated partial thromboplastin time (aPTT). Patients with clinical evidence of coagulopathy require additional tests to detect the presence of DIC.

Although indiscriminate use of blood cultures has low utility, blood culture is the primary modality for facilitating the diagnosis of intravascular infections (eg, endocarditis) and infections of indwelling intravascular devices. Two populations—people who abuse intravenous (IV) drugs and patients with prosthetic heart valves—are at high risk for endocarditis.

Patients at risk for bacteremia include adults who are febrile with elevated WBC or neutrophil band counts, elderly patients who are febrile, and patients who are febrile and neutropenic. These populations have a 20-30% incidence of bacteremia. The incidence of bacteremia is at least 50% in patients with sepsis and evidence of end-organ dysfunction.

A urinalysis and a urine culture should be ordered for every patient who is in a septic state. Urinary infection is a common source of sepsis, especially in elderly individuals. Adults who are febrile without localizing symptoms or signs have a 10-15% incidence of occult urinary tract infection (UTI).

Secretions or tissue for Gram stain and culture should be obtained from sites of potential infection. Generally, the Gram stain is the only available test for immediately documenting the presence of bacterial infection and guiding the choice of initial antibiotic therapy.

When meningitis or encephalitis is suspected, LP must be performed on an urgent basis. In patients with an acute fulminant presentation, rapid onset of septic shock, and severe impairment of mental status, bacterial meningitis must be ruled out by means of LP.

Procedures such as cardiac monitoring, noninvasive blood pressure monitoring, and pulse oximetry are necessary because patients often require admission to the intensive care unit (ICU) for invasive monitoring and support. Supplemental oxygen is provided during initial stabilization and resuscitation.

In all patients in septic shock, adequate venous access for volume resuscitation is necessary. A central venous line can also be used to monitor central venous pressure for assessment of intravascular volume status.

An indwelling urinary catheter used to monitor urinary output can serve as a marker for adequate renal perfusion and cardiac output.

Patients in whom septic shock associated with acute lung injury or right-sided heart failure require either right-heart catheterization with a pulmonary artery (Swan-Ganz) catheter or a transpulmonary thermodilution device (eg, PiCCO, Vigileo) to guide therapy. These catheters provide an assessment of the volume status of a patient who is in a septic state. Cardiac output measurements can be obtained. Furthermore, determination of mixed venous oxygenation from the pulmonary artery catheter is helpful in determining the status of tissue oxygenation.

Dynamic hemodynamic monitoring devices using pulse pressure and stroke volume variation are used in some centers when the patients are in sinus rhythm and on mechanical ventilation without spontaneous breathing to define volume responsiveness and assess dynamic arterial tone, both useful in deciding on resuscitation treatment options.

Most patients who are in a septic state experience respiratory distress secondary to severe sepsis or as a manifestation of septic shock. Pulmonary dysfunction of sepsis (ie, acute respiratory distress syndrome [ARDS]) also may occur. These patients need intubation and mechanical ventilation for optimum respiratory support.

There are two well-defined forms of multiple organ dysfunction syndrome (MODS). In both, the development of acute lung injury (ALI) or ARDS is of key importance to the natural history. ARDS is the earliest manifestation in all cases (see the images below).

In the more common form of MODS, the lungs are the predominant—and often the only—organ system affected until very late in the disease. These patients most often present with a primary pulmonary disorder, such as pneumonia, aspiration, contusion, near drowning, exacerbation of chronic obstructive pulmonary disease (COPD), hemorrhage, or pulmonary embolism.

Lung disease progresses to meet ARDS criteria. Encephalopathy or mild coagulopathy may accompany pulmonary dysfunction, which persists for 2-3 weeks. At this time, the patient either begins to recover or progresses to fulminant dysfunction in another organ system. Once another major organ dysfunction occurs (see Table 1 below), these patients frequently do not survive.

Table. Criteria for Organ Dysfunction (Open Table in a new window)

 

The second form of MODS presents quite differently. These patients often have an inciting source in organs other than the lungs—most commonly, intra-abdominal sepsis, extensive blood loss, pancreatitis, or vascular catastrophes. ALI or ARDS develops early, and dysfunction in other organ systems (hepatic, hematologic, cardiovascular, and renal) also develops much sooner than in the first form of MODS. Patients remain in a pattern of compensated dysfunction for several weeks, at which time they either recover or deteriorate further and die.

Patients with infected foci should be taken for definitive surgical treatment after initial resuscitation and administration of antibiotics. When an infected focus persists, there is little to be gained from spending hours on attempting to stabilize the patient.

Infectious processes require expeditious surgical drainage or debridement for source control, even if the patient does not appear stable. Without emergency surgical treatment, the patient’s condition may not improve.