Distributive Shock Workup

Updated: Jan 05, 2018
  • Author: Klaus-Dieter Lessnau, MD, FCCP; Chief Editor: Michael R Pinsky, MD, CM, Dr(HC), FCCP, MCCM  more...
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Workup

Approach Considerations

All patients with evidence of distributive shock should undergo the following studies:

  • Complete blood count (CBC) with differential

  • Urinalysis

  • Electrolytes

  • Blood urea nitrogen (BUN)

  • Creatinine

  • Glucose

  • Urine cultures

  • Blood cultures

  • Possibly arterial blood gas or at least venous blood gas

  • Serum lactate -  Especially with metabolic acidosis or if an elevated anion gap is present

If pneumonia is suspected, sputum Gram stain and culture should be performed.

All patients with a suspected intra-abdominal pathologic condition or hepatic insufficiency should undergo the following studies:

  • Serum bilirubin

  • Alkaline phosphatase

  • Aspartate aminotransferase (AST), alanine aminotransferase (ALT)

  • Prothrombin time (PT)/activated partial thromboplastin time (aPTT)/INR (international normalized ratio)

  • Amylase, lipase

All patients with suspected disseminated intravascular coagulation (DIC) should undergo the following studies:

  • Obtain PT, aPTT, fibrin split products, D-dimer assay, fibrinogen level, and platelet count.

  • Examine peripheral blood smear for signs of erythrocyte microangiopathic changes, such as schistocytes.

Electrocardiography

Electrocardiography should be performed to examine the patient for evidence of underlying pathologic cardiac conditions (left ventricular hypertrophy, cor pulmonale, low voltage, bundle branch block) or acute changes of ischemia or pericarditis.

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Imaging Studies

Imaging studies may be integral to defining the source of infection and identifying areas in need of drainage. All patients should undergo chest radiography (see the images below). However, radiographic studies may not be sensitive enough to reveal intra-abdominal pathologic conditions. Consequently, computed tomography (CT) scanning has become the diagnostic test of choice for suspected intra-abdominal causes of sepsis. Consider abdominal and pelvic CT scans with oral contrast and intravenous contrast if these sites are found to be clinically suspicious for infection.

In suspected cases of cholecystitis or pancreatitis, abdominal ultrasonography is most useful to assess for cholelithiasis, biliary dilatation, and fluid collections around the gallbladder or the head of the pancreas.

Point-of-care ultrasonography/echocardiography may be performed at the bedside in critically ill patients to evaluate cardiac function, fluid status, and response to hemodynamic intervention and to exclude tamponade.

An 8-year-old boy developed septic shock secondary An 8-year-old boy developed septic shock secondary to Blastomycosis pneumonia. Fungal infections are a rare cause of septic shock.
A 28-year-old woman who was a previous intravenous A 28-year-old woman who was a previous intravenous drug user (human immunodeficiency virus [HIV] status: negative) developed septic shock secondary to bilateral pneumococcal pneumonia.
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Procedures

Lumbar puncture

Lumbar puncture (LP) is indicated in patients with nuchal rigidity, headache, or unexplained neurologic findings or in patients with sepsis and altered level of consciousness without another apparent source of infection. A CT scan of the head should be performed prior to LP whenever feasible.

Arterial catheters

The use of pulmonary artery catheters (PACs) was the standard of care for decades (see Table 1, below). However, data now suggest an increase in mortality with the use of PAC monitoring, calling this practice into question. Additionally, current parameters for PAC-guided resuscitation may not be appropriate. A randomized trial of the use of PACs in elderly, high-risk surgical patients found no benefit to therapy directed by PACs compared with treatment per the standard of care. [15, 16]

Table 1. Pulmonary Artery Catheter Findings in Common Shock States (Open Table in a new window)

Diagnosis

Pulmonary Capillary Wedge Pressure

Cardiac Output

Cardiogenic shock*

Increased

Decreased

Extracardiac obstructive shock

1. Pericardial tamponade†

2. Pulmonary embolism

Increased

Normal or decreased

Decreased

Decreased

Hypovolemic shock

Decreased

Decreased

Distributive shock

1. Septic shock

2. Anaphylactic shock

Normal or decreased

Normal or decreased

Increased or normal

Increased or normal

*In cardiogenic shock due to a mechanical defect, such as mitral regurgitation, forward cardiac output is reduced, although the measured cardiac output may be unreliable. Large V waves are commonly observed in the pulmonary capillary wedge tracing in mitral regurgitation.

†The hallmark finding is equalization of right atrial mean, right ventricular end-diastolic, pulmonary artery (PA) end-diastolic, and pulmonary capillary wedge pressures.

Arterial catheter placement should be considered in hemodynamically unstable patients who are receiving continuous infusions of vasoactive drugs or in patients requiring frequent arterial blood gas measurements (eg, patients on mechanical ventilation). The arterial catheter can be placed radially, femorally, axillary, but never brachially. Some patients can be managed with the pulse oximetry wave graphic only.

Transthoracic and transesophageal echocardiography

Transthoracic echocardiography (TTE) and transesophageal echocardiography (TEE) may be used to estimate right atrial filling and right ventricular volumes in patients with undetermined fluid status. TTE is a noninvasive method for the assessment of left ventricular function. This technique has several limitations, being time consuming, operator dependent, and limited by preexisting pulmonary disease or chest wall injuries.

TEE is a somewhat more invasive test that provides excellent structural information in the critically ill patient. This technique allows the assessment of preload, ventricular wall motion abnormalities, and the pericardium.

Other minimally invasive techniques

Thoracic bioelectrical impedance (TBI)

This technique relies on formulas to estimate stroke volume and cardiac output based on the measured bioimpedance of blood velocity and volume of blood flow through the aorta.

Pulse-induced CO (PiCO), lithium dilution CO (LiCO), and FloTrac

Via an arterial catheter, cardiac output (CO) can be continuously monitored. FloTrac does not require calibration. Stroke volume and continuous systemic vascular resistance (SVR) can be measured and calculated using basic patient information.

Total circulating blood volume (TCBV)

This is measured using indocyanine green infusion and is quantified using spectrophotometry.

Microcirculatory imaging

Microcirculatory imaging techniques, such as orthogonal polarization spectral and side-stream dark-field imaging, have allowed direct observation of the microcirculation at the bedside. They have demonstrated different types of heterogenous flow patterns of microcirculatory abnormalities in different types of distributive shock and may complement early goal-directed therapy in shock. [17, 18]

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