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C HAPTER 2 1 / Hemodynamic Monitoring 495
70%) for adult patients with severe sepsis and septic if early lactate-directed therapy has an effect on outcomes in pa-
shock, 132,240 and use of as an endpoint has been found to tients with sepsis and septic shock.
improve outcomes in pediatric and adolescent patients with sep-
tic shock. 455 Optimizing Resuscitation
Caution must be exercised when using as an endpoint of The current endpoints for resuscitation are based on optimizing
resuscitation as the exact threshold to optimize outcomes has not the patient’s physiological status. 166 A major criticism of research
been identified 456 and interventions to increase may vary related to optimization is that in many cases resuscitation is not
initiated until after organ failure had occurred. Evidence suggests
between different patient populations. The benefits of Scvo 2
monitoring have been described only with continuous monitor- that although achieving normal O 2 delivery is important, the tim-
ing. Recent research found that intermittent measurements ing of the initiation of goal-directed therapy may be the more crit-
missed between 29% and 62% of clinically significant changes in ical factor in decreasing morbidity and mortality. 240,466,467 Two
, which supports the need for continuous monitoring (Pam- meta-analyses found no decrease in mortality if attempts to im-
Scvo 2
bianco, unpublished data, 2008). Other factors to consider when prove tissue perfusion were taken after the onset of organ failure.
deciding on whether to use continuous versus intermittent moni- In contrast, beneficial effects were observed when attempts to im-
toring include the risk of intermittent blood draws (infection and prove oxygenation were taken preoperatively or before the onset
iatrogenic anemia) and the cost of intermittent laboratory testing of organ failure. 466,467
versus purchasing catheters for continuous monitoring. In 2001, a study was conducted to determine the effect of early
goal-directed therapy with patients who presented to the emergency
Lactate department with severe sepsis or septic shock. 240 The patients in the
experimental group received 6 hours of early goal-directed therapy,
Lactate is an end product of anaerobic metabolism, and an in- including volume resuscitation, blood transfusions, and vasopressor
creased level ( 2 mmol/L) is a surrogate indicator of tissue hy- therapy, aimed at optimizing tissue oxygenation (CVP 8 to 12 mm
poxia. Although hyperlactatemia is indicative of tissue hypoxia, Hg, MAP 65 mm Hg, UOP 0.5 mL/kg/h, and Scvo 2
because the liver has a large capacity to oxidize lactate, a normal 70%) in contrast to the patients in control group whose ther-
serum lactate level does not rule out tissue hypoperfusion and apy was guided only by standard hemodynamic indices. An in-
anaerobic metabolism. In addition, localized hypoperfusion may teresting finding in this study was that on admission, despite
be insufficient to increase systemic levels. Therefore, lactate is a relatively normal vital signs in both the control and experimen-
late, and often insensitive, indicator of hypoperfusion. Con- tal groups, both groups had indications of tissue hypoxia. Early
versely, increased lactate occurs with factors other than hypoxia, goal-directed therapy was associated with a 16% absolute reduc-

including increased glycolysis (e.g., increased Na , K -ATPase tion in mortality compared with standard care. Although there
activity, hypermetabolic state, catecholamine administration, dia- was no difference between the routine care and experimental
betes mellitus, trauma, burns, sepsis) and impaired lactate clear- group in length of ICU stay, the experimental group was also less
ance (hepatic dysfunction, pyruvate dehydrogenase dysfunction). acutely ill during the first 3 days in the ICU and had a shorter
Despite these limitations tissue hypoxia should be ruled out be- length of hospitalization. Subsequent studies have also demon-
fore assuming that other factors are causing increased lactate. 457 strated morbidity and mortality benefits from the initiation of
Increased lactate is associated with increased morbidity and early goal-directed therapy for patients presenting with severe sep-
mortality. In patients with a suspected infection, a lactate 4 sis, 468–470 and a recent systematic analysis of 39 goal-directed
mmol/L was associated with mortality, independent of BP and therapy studies found that all studies had a relative risk reduction
other covariates. 458 In patients who underwent emergent repair of of 25% or greater and an absolute risk reduction greater than
a ruptured aortic aneurysm, an immediate postoperative lactate 9%. 470 In addition, in community hospitals the benefits of the
4 mmol/L or a base deficit 7 were associated with a 95% early recognition of hypoperfusion or shock from any cause and
probability of death 459 and in cardiac surgery patients a lactate the early initiation of therapy have also been shown. Research is
3 mmol/L during surgery or on admission to the ICU was as- ongoing to determine if the benefits in these studies are related to
sociated with increased morbidity and mortality. 460,461 the Early Goal-Directed Therapy (EGDT) Protocol or simply the
Although increased levels of lactate ( 4 mmol/L) is a trigger provision of focused care (in a manner similar to the response to
for the initiation of goal-directed therapy in patients with sepsis, 132 trauma, cardiac arrest, or stroke). 471–474 This research will also aid
the use of lactate levels as an indicator of tissue hypoxia in these pa- in further description of the triggers for the administration of
tients is complicated. 462 In septic shock, increased lactate levels blood products and to determine if monitoring is necessary
may occur when there is adequate O 2 delivery and, conversely, during EGDT.
when the O 2 delivery increases lactate levels may not decrease. Fac- There is less literature on goal-directed therapy in cardiac sur-
tors that may be associated with this discordant response include gery. 475 Goal-directed therapy to optimize oxygenation and per-
an increase in glycolysis caused by an inflammatory increase in fusion (Svo 2 70% and lactate 2 mmol/L) in addition to stan-
pyruvate or increased levels of endogenous or exogenous epineph- dard hemodynamic endpoints (CI, BP, PAOP, Hgb) during the
rine and decreased lactate clearance. 462,463 first 8 hours after cardiac surgery was associated with decreased
General recommendations for the use of lactate are to follow morbidity and shorter hospitalization compared with patients
trends rather than a single measurement. Hyperlactatemia (lactate whose care was aimed at optimizing standard endpoints. 476 Based
2 mmol/L) persisting for more than 6 hours after admission is on a review of the literature 475 the following primary endpoints for
predictive of increased mortality in ICU and trauma patients. 464 resuscitation have been suggested for high-risk cardiac surgery pa-
A decrease in lactate of 10% per hour is usually indicative of tients: normal perfusion pressure (MAP 70–90 mm Hg), SVI
2
adequate response to treatment, whereas no change or an increase 35 mL/beat/m , and Svo 2 70%. Secondary endpoints include
in lactate is an ominous sign. 465 Research is ongoing to determine CVP 15 mm Hg, PAEDP 20 mm Hg, lactate 2 mmol/L