Abstract
BackgroundLactic acidosis with an elevated lactate–pyruvate ratio suggesting anoxia is a common feature of severe falciparum malaria. High lactate levels are associated with parasitized erythrocyte sequestration in the microcirculation. To assess if there is an additional contribution to hyperlactataemia from relatively inadequate total oxygen delivery, oxygen consumption and delivery were investigated in patients with malaria.MethodsAdult Bangladeshi and Indian patients with uncomplicated (N = 50) or severe (N = 46) falciparum malaria or suspected bacterial sepsis (N = 27) and healthy participants as controls (N = 26) were recruited at Chittagong Medical College Hospital, Chittagong, Bangladesh and Ispat General Hospital, Rourkela, India. Oxygen delivery (DO2I) was estimated from pulse oximetry, echocardiographic estimates of cardiac index and haematocrit. Oxygen consumption (VO2I) was estimated by expired gas collection.ResultsVO2I was elevated in uncomplicated median (IQR) 185.1 ml/min/m2 (135–215.9) and severe malaria 192 ml/min/m2 (140.7–227.9) relative to healthy persons 107.9 ml/min/m2 (69.9–138.1) (both p < 0.001). Median DO2I was similar in uncomplicated 515 ml/min/m2 (432–612) and severe 487 ml/min/m2 (382–601) malaria and healthy persons 503 ml/min/m2 (447–517) (p = 0.27 and 0.89, respectively). The VO2/DO2 ratio was, therefore, increased by similar amounts in both uncomplicated 0.35 (0.28–0.44) and severe malaria 0.38 (0.29–0.48) relative to healthy participants 0.23 (0.17–0.28) (both p < 0.001). VO2I, DO2I and VO2/DO2 did not correlate with plasma lactate concentrations in severe malaria.ConclusionsReduced total oxygen delivery is not a major contributor to lactic acidosis in severe falciparum malaria.
Highlights
Lactic acidosis with an elevated lactate–pyruvate ratio suggesting anoxia is a common feature of severe falciparum malaria
Previous studies have investigated the haemodynamics of severe malaria using invasive techniques [2, 6,7,8] and reported lack of association between total oxygen delivery and plasma lactate [2]
Oxygen consumption was measured to assess whether inhibition of oxidative metabolism contributes to lactic acidosis, and determined the ratio of oxygen consumption to delivery (VO2/DO2) to provide a better estimate of the adequacy of oxygen delivery
Summary
Lactic acidosis with an elevated lactate–pyruvate ratio suggesting anoxia is a common feature of severe falciparum malaria. To assess if there is an additional contribution to hyperlactataemia from relatively inadequate total oxygen delivery, oxygen consumption and delivery were investigated in patients with malaria. Previous studies have investigated the haemodynamics of severe malaria using invasive techniques [2, 6,7,8] and reported lack of association between total oxygen delivery and plasma lactate [2]. In this article the hypothesis that inadequate oxygen delivery contributes to the metabolic acidosis of severe malaria is evaluated. Oxygen consumption was measured to assess whether inhibition of oxidative metabolism contributes to lactic acidosis, and determined the ratio of oxygen consumption to delivery (VO2/DO2) to provide a better estimate of the adequacy of oxygen delivery
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