Page 838 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

CHAPTER 64: Sepsis, Severe Sepsis, and Septic Shock 569

septic ICU patients. The SOFA score assigns 1 to 4 points for the level of catheter tip for measures of mixed venous saturation (Sv O 2 ). Because
dysfunction to six organ systems on a daily basis: respiratory, circulatory, Scv O 2 and Sv O 2 are measures of oxygen returning to the right heart, they
renal, hematology, hepatic, and central nervous system. A systematic are general measures of both oxygen delivery and oxygen consump-
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review evaluating SOFA for predicting mortality in the ICU revealed tion, and thus in part reflect tissue oxygenation. Since sepsis induces
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that SOFA scores at admission faired a little worse than APACHE II/III, dysfunctional tissue metabolism as part of expected pathophysiology,
but were comparable with SAPS II. Serial SOFA scores seem to perform oxygen extraction from the tissues may be disturbed and results in
similarly to other organ failure scores. The systematic review concluded elevated Scv O 2 or Sv O 2 . However, for patients with septic shock, EGDT
that combination of the various models of SOFA with APACHE II/III targets a “normalization” of Scv O 2 and/or Sv O 2 by fluid administration,
and SAPS II improved prognostic performance. 88 blood transfusion, and administration of inotropic agents, as needed. 93
■ MORTALITY PROBABILITY MODEL 0 AT ZERO HOURS ■ CARDIAC OUTPUT AND FLUID RESPONSIVENESS

MPM-0 is a model predicting the probability of hospital death taken at Cardiac output may be measured by a variety of invasive or noninvasive
24, 48, and 72 hours. It uses chronic health status, acute diagnosis, physio- techniques in patients with sepsis, most frequently using standard ther-
logic variables, and other parameters including mechanical ventilation. modilution. By measuring CO, one can calculate SVR as an estimate of
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MPM-0 was validated on 12,610 critically ill patients across Europe vascular tone. In order to optimize fluid resuscitation in patients with
and the United States from 1989 to 1990. MPM-0 was then readjusted sepsis it is helpful to know whether a patient will improve (“respond”)
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because observed mortality rate was lower than the predicted aging with fluid administration or whether they suffer from pure vasoplegia
model. MPM-0 was recalibrated from 124,885 critically ill patients from and will only respond to pharmacological vasoconstriction (ie, intra-
2001 to 2004. Fifteen independent variables were used in addition to venous vasopressors). Almost invariably, sepsis patients will respond
elective surgical patients and “do–not-resuscitate” orders were also taken to fluid administration, but the optimal volume varies widely between
into account. 89 septic patients. Some patients may fail to respond further after admin-
■ MONITORING: HEMODYNAMIC AND CARDIOPULMONARY istration of, for example, 2 L of intravenous crystalloid, whereas others
may continue to improve their hemodynamics after more than 6 L of the
MONITORING IN SEPSIS same fluid administered. Optimizing and individualizing fluid resus-
Septic patients often require intensive care due to the severity of their citation may be achieved by determining in advance whether patients
illness and the monitoring that is required for optimal patient care. The will respond to additional fluid resuscitation. This is done by knowing
combination of dehydration and vasoplegia may result in profound whether the CO will increase with fluid administration, most often by an
hypotension with circulatory shock, necessitating some form of hemo- increase in stroke volume (SV). One method to make this determination
dynamic monitoring. In particular, because early fluid resuscitation is is by passive leg raising, resulting in autotransfusion of 200 to 500 cc of
crucial in the management of sepsis, accurate hemodynamic monitoring blood volume from the lower extremities to the central circulation. If CO
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is critical to the initial approach to patient management and assessing increases with this maneuver, then fluid responsiveness is very likely.
the response to medical interventions. The most common parameters Aside from this bedside maneuver, stroke volume variation (SVV), pulse
used in monitoring septic patients are pulse oximetry, central venous pressure variation (PPV), and systolic pressure variation (SPV) are clini-
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pressure (CVP), central venous or mixed venous oxygen saturation cally available predictors of fluid responsiveness. Higher values of these
), cardiac output (CO), systemic vascular resistance (SVR), parameters predict fluid responsiveness because they measure variations
(Scv O 2 , Sv O 2 in stroke volume with changes in intrathoracic pressure. There are mul-
and extravascular lung water (EVLW). Each of these parameters is
complementary and may assist in both the early and later management tiple hemodynamic monitoring systems that can measure one or more
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of sepsis, organ dysfunction, and shock. of these parameters with good accuracy. However, SVV, PPV, and SPV
■ CENTRAL VENOUS PRESSURE and they have not been validated as reliable predictors of fluid respon-
rely upon significant and consistent changes in intrathoracic pressure,
Central venous pressure can be measured by transducing the pressure siveness in patients who are spontaneously breathing, dyssynchronously
breathing with mechanical ventilatory support, or in patients with very
from a thoracic central venous catheter placed in either the internal jugu- low changes in intrathoracic pressure, including some patients managed
lar vein or the subclavian vein with its tip resting in the right atrium. CVP with low-tidal-volume ventilation. 97,98
is used in the algorithm to deliver early goal-directed therapy (EGDT)
(see the section Fluid Therapy), primarily as a measure of volume ■ EXTRAVASCULAR LUNG WATER
status and cardiac preload. Although some studies have suggested
that CVP may be used to predict the hemodynamic response to fluid Extravascular lung water is a quantitative measure of pulmonary
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administration (eg, increased cardiac output after fluid administration), edema. Because fluid resuscitation is a key component of early sepsis
CVP is notoriously inaccurate for this purpose. CVP cannot accurately therapy and because negative fluid balance after initial resuscitation
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identify patients who will respond to fluid administration, or those who and hemodynamic stabilization is associated with improved clinical
will not respond to fluid administration with improved hemodynamics. outcomes, monitoring of both fluid responsiveness and complications
In addition, CVP measures are context sensitive: for example, values of fluid resuscitation can be valuable in patients with sepsis. EVLW has
<5 mm Hg may indicate hypovolemia in patients with sepsis and may been associated with adverse clinical outcomes in critically ill patients,
be normal in healthy individuals. In addition, although the goal CVP including greater mortality, 99,100 and is predictive of the development of
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for sepsis resuscitation is generally 8 to 12 mm Hg, for patients receiving ARDS and adverse outcomes if ARDS develops. As a complementary
positive pressure ventilation a higher CVP target (12-15 mm Hg) may pulmonary measure of fluid administration and tissue edema, it may be
be appropriate. Overall, CVP is not a good predictor of intravascular used to guide both fluid resuscitation and later fluid removal.
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volume or fluid responsiveness and it cannot be used alone in determin-
ing fluid administration in sepsis. THERAPEUTIC APPROACH
■ VENOUS OXYGEN SATURATION ■ ANTIBIOTIC THERAPY

) may be determined from a Although initiating aggressive fluid resuscitation is first priority when
Central venous oxygen saturation (Scv O 2
thoracic central venous catheter, either by blood gas analysis or inter- managing patients with severe sepsis or septic shock, antibiotic therapy
nally using a fiberoptic catheter. For patients with a pulmonary artery should be initiated as soon as possible. Physicians should rapidly obtain
catheter in place, the same measures may be taken from the distal cultures of suspected body fluids/blood from suspected sites of infection

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