Lactate Levels as Predictors of the Relationship between Oxygen Delivery and Consumption in ARDS: Results


17 Jan 2013

Lactate Levels as Predictors of the Relationship between Oxygen Delivery and Consumption in ARDS: ResultsDescriptive features of patients with normal aqd with elevated lactate levels are shown in Table 1. The alveolar-arterial oxygen tension gradient and mortality were significantly higher in the elevated lactate group. A higher proportion of patients in the increased lactate group exhibited a change in Vo2 in the same direction as the change in Do2, consistent with a supply-dependent pattern of oxygen utilization (Table 1). Changes in Vo2 in response to a change in Do2 for all interventions (fluids, blood, and PEEP) are shown in Figure 1 and Table 2. The group with lactic acidosis exhibited a significant change in Vo2 corresponding to changes in Do2. In spite of a significant change in Do2 for patients without lactic acidosis, a significant corresponding change in Vo2 was not observed. The Vo2 response in this group can be considered insignificant, with a statistical power of 0.8. ventolin inhalers
Patients who received PEEP as an intervention were analyzed separately, and the results are shown in Table 3. All patients exhibited a decrease in Do2 associated with a reduction in cardiac output observed after the implementation of PEEP Patients with lactic acidosis exhibited significant decreases in Vo2 associated with the decrease in Do2. A significant decrease in Vo2 was not observed in patients without lactic acidosis, although this negative result could not be assured with a statistical power of more than 0.8.

Table 1—Descriptive Information

Lactate Level
Data Normal Increased
No. of patients 26 32
Lactate level, mmol/L 2.0 ±0. I 4.9±0.5
Cl, L/min/m2 3.7±0.4 3.8 ±0.2
Hb level, g/dl 10.9 ±0.5 9.8 ±0.4
Venous admixture, percent 31.4 ±2.8 36.5 ±2.1
Alveolar-arterial oxygen tension
difference, mm Hg 289 ± 29 377 ±22
Arterial/alveolar oxygen tension
ratio, percent 31±3 22±2
Mortality, percent 65 94
No. exhibiting direct
relationship between Vo8 and
Do2 (percent) 14 (54)|| 26 (81)||
Interval between initial and
final Do2 and Vo2
measurements, h 4.4±0.4 3.9±0.3

Table 2—Effects of All Interventions (Fluids, Blood, and Application of PEEP) on Dot and Vo

Normal Lactate (n = 26) Increased Lactate (n = 32)
Data Lowest Highest Lowest Highest
Do2) ml/min/m2 Vo2, ml/min/m2 488 ±41 142 ±11 601 ±51 151 ±11 454 ±27 118 ± 7 591 ±37 152±lit

Table 3—Effects of PEEP on Do% and Vo

Normal Lactate (n = 6) Increased Lactate (n = 10)
Data Before PEEP After PEEP Before PEEP After PEEP
Do2, ml/min/m2 Vo2, ml/min/m2 754 ±169 161 ±42 650 ±138 180 ±42 635 ±63 139 ±16 531± 52t 116 ±12


Figure 1. Change in Vo* in response to change in Do, for all patients, as outlined in Table 1. Squares represent patients with elevated blood lactate levels; circles denote patients with lactate concentrations of 2.4 mmol/L or less.

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