Association between Serum Lactate Levels and Early Neurogenic Pulmonary Edema after Nontraumatic Subarachnoid Hemorrhage

Background and Purpose: Few studies have described the risk factors associated with the development of neurological pulmonary edema (NPE) after subarachnoid hemorrhage (SAH). We have hypothesized that acute-phase increases in serum lactate levels are associated with the early development of NPE following SAH. The aim of this study was to clarify the association between lactic acidosis and NPE in patients with nontraumatic SAH. Methods: We retrospectively evaluated 140 patients with nontraumatic SAH who were directly transported to the Nippon Medical School Hospital emergency room by the emergency medical services. We compared patients in whom NPE developed (NPE group) and those in whom it did not (non-NPE group). Results: The median (quartiles 1-3) arrival time at the hospital was 32 minutes (28-38 minutes) after the emergency call was received. Although the characteristics of the NPE and non-NPE groups, including mean arterial pressure (121.3 [109.0-144.5] and 124.6 [108.7-142.6] mm Hg, respectively; P=0.96), were similar, the median pH and the bicarbonate ion (HCO3-) concentrations were significantly lower in the NPE group than in the non-NPE group (pH, 7.33 [7.28-7.37] vs. 7.39 [7.35-7.43]); P=0.002; HCO3-, 20.8 [18.6-22.6] vs. 22.8 [20.9-24.7] mmol/L; P=0.01). The lactate concentration was significantly higher in the NPE group (54.0 [40.3-61.0] mg/dL) than in the non-NPE group (28.0 [17.0-37.5] mg/dL; P<0.001). Multivariable regression analysis indicated that younger age and higher glucose and lactate levels were significantly associated with the early onset of NPE in patients with SAH. Conclusion: The present findings indicate that an increased serum lactate level, occurring within 1 hour of the ictus, is an independent factor associated with the early onset of NPE. Multicenter prospective studies are required to confirm our results.