Have you measured lactate in your sick obstetrics and gynecology patients during the past year?

CASE 2. Gynecologic practice: Bacterial infection identified in the presence of abdominal pain and vomiting

A 40-year-old woman presents to the ED 5 days following a myomectomy, with nausea, vomiting, and abdominal pain. Her vital signs reveal: temperature, 98.4°F (36.9°C); heart rate, 122 bpm; blood pressure, 115/70 mm Hg; and white blood cell count, 6,270 per uL. Her lactate level is 4.0 mM. She is admitted to the ICU with a presumptive diagnosis of severe sepsis and treatment with broad-spectrum antibiotics is initiated. Twenty-four hours following admission, gram-negative rods are identified in blood cultures that are later identified to be Bacteroides fragilis.

For the past 2 decades there has been a concerted national effort to reduce mortality caused by sepsis through early diagnosis and aggressive treatment of sepsis in an ICU setting. Observational studies have reported that an elevated lactate level is an excellent early biomarker for sepsis and may be observed prior to the onset of fever, elevated white blood cell count, or hypotension.⁶ For example, in one large study of patients with sepsis and a lactate measurement ≥4 mM, only 50% of patients had a systolic blood pressure <90 mm Hg.

Elevated lactate levels also are associated with an increased risk of death. Among 13,932 consecutive patients admitted to an ICU in Alberta, Canada, the mortality rate among patients with a venous or arterial lactate >2 mM was 20%, compared with a mortality rate of 5% for patients with a lactate level ≤2 mM.¹² In a study of 1,278 patients with infection admitted to the hospital from the ED, mortality increased as baseline lactate concentration rose. For lactate concentrations of 0 to 2.4, 2.5 to 3.9, and ≥4.0 mM, mortality rates were 5%, 9%, and 28%, respectively.¹³

In patients with sepsis, serial measurement of lactate can help to guide treatment. In a randomized trial, 348 patients admitted to an ICU with a lactate ≥3 mM were randomly assigned to standard treatment, in which the clinicians had no knowledge of patients’ lactate levels, or to an experimental group, in which the clinicians were provided lactate measurement results every 2 hours. Compared with clinicians in the control group, the clinicians with access to frequent lactate measurements administered more fluids and vasodilators to their patients. Compared with patients in the control group, the hospital mortality rate was lower when the clinicians had access to frequent lactate measurements (34% vs 44%, respectively; adjusted hazard ratio, 0.61; 95% confidence interval, 0.43−0.87; P = .0006).¹⁴

Elevated lactate levels in the fetus and newborn

The physiologic status of the newborn is routinely assessed with the Apgar score. Umbilical artery and venous blood gases, including measurement of pH, are often used as a corroborating biomarker. Most studies report that umbilical artery or vein lactate measurement is as useful as a pH measurement in assessing newborn physiologic status. The normal range of lactate in fetuses and newborns is not precisely defined, with values between 3.5 and 7 mM being cited as the upper limit of normal.¹⁵⁻¹⁸

In many countries (but not the United States), in utero fetal status during labor is assessed by fetal scalp sampling of blood and measurement of either pH or lactate. Fetal scalp sampling is difficult and often very little blood is obtained, making it difficult to measure pH. A Cochrane review reported that in 2 randomized trials, fetal scalp sampling produced a successful measurement of lactate in 99% of attempts, while a pH result could only be obtained in 79% of cases due to an inadequate volume of blood or clotted blood.¹⁹

Increased lactate measurement can help our patients

Measuring lactate in order to rapidly identify patients with major physiologic derangements is practiced widely in EDs and ICUs. There is significant opportunity to increase the use of lactate measurement in obstetrics and gynecology. Increasing this use will help to rapidly identify women with severe sepsis and other diseases, leading to more rapid intervention and improved outcomes.

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