Identifying prognostic factors of severe metabolic acidosis and uraemia in African children with severe falciparum malaria: a secondary analysis of a randomized trial.

BACKGROUND: Severe metabolic acidosis and acute kidney injury are major causes of mortality in children with severe malaria but are often underdiagnosed in low resource settings. METHODS: A retrospective analysis of the 'Artesunate versus quinine in the treatment of severe falciparum malaria in African children' (AQUAMAT) trial was conducted to identify clinical features of severe metabolic acidosis and uraemia in 5425 children from nine African countries. Separate models were fitted for uraemia and severe metabolic acidosis. Separate univariable and multivariable logistic regression were performed to identify prognostic factors for severe metabolic acidosis and uraemia. Both analyses adjusted for the trial arm. A forward selection approach was used for model building of the logistic models and a threshold of 5% statistical significance was used for inclusion of variables into the final logistic model. Model performance was assessed through calibration, discrimination, and internal validation with bootstrapping. RESULTS: There were 2296 children identified with severe metabolic acidosis and 1110 with uraemia. Prognostic features of severe metabolic acidosis among them were deep breathing (OR: 3.94, CI 2.51-6.2), hypoglycaemia (OR: 5.16, CI 2.74-9.75), coma (OR: 1.72 CI 1.17-2.51), respiratory distress (OR: 1.46, CI 1.02-2.1) and prostration (OR: 1.88 CI 1.35-2.59). Features associated with uraemia were coma (3.18, CI 2.36-4.27), Prostration (OR: 1.78 CI 1.37-2.30), decompensated shock (OR: 1.89, CI 1.31-2.74), black water fever (CI 1.58. CI 1.09-2.27), jaundice (OR: 3.46 CI 2.21-5.43), severe anaemia (OR: 1.77, CI 1.36-2.29) and hypoglycaemia (OR: 2.77, CI 2.22-3.46) CONCLUSION: Clinical and laboratory parameters representing contributors and consequences of severe metabolic acidosis and uraemia were independently associated with these outcomes. The model can be useful for identifying patients at high risk of these complications where laboratory assessments are not routinely available.

Investigating causal pathways in severe falciparum malaria: A pooled retrospective analysis of clinical studies.

BACKGROUND: Severe falciparum malaria is a medical emergency characterised by potentially lethal vital organ dysfunction. Patient fatality rates even with parenteral artesunate treatment remain high. Despite considerable research into adjuvant therapies targeting organ and tissue dysfunction, none have shown efficacy apart from renal replacement therapy. Understanding the causal contributions of clinical and laboratory abnormalities to mortality is essential for the design and evaluation of novel therapeutic interventions. METHODS AND FINDINGS: We used a structural model causal inference approach to investigate causal relationships between epidemiological, laboratory, and clinical variables in patients with severe falciparum malaria enrolled in clinical trials and their in-hospital mortality. Under this causal model, we analysed records from 9,040 hospitalised children (0-12 years, n = 5,635) and adults (n = 3,405, 12-87 years) with severe falciparum malaria from 15 countries in Africa and Asia who were studied prospectively over the past 35 years. On admission, patient covariates associated with increased in-hospital mortality were severity of acidosis (odds ratio [OR] 2.10 for a 7-mEq/L increase in base deficit [95% CI 1.93-2.28]), renal impairment (OR 1.71 for a 2-fold increase in blood urea nitrogen [95% CI 1.58, 1.86]), coma (OR 3.59 [95% CI 3.07-4.21]), seizures (OR 1.40 [95% CI 1.16-1.68]), shock (OR 1.51 [95% CI 1.14-1.99]), and presumed pulmonary oedema (OR 1.58 [95% CI 1.04-2.39]). Lower in-hospital mortality was associated with moderate anaemia (OR 0.87 for a decrease of 10 percentage points in haematocrit [95% CI 0.80-0.95]). Circulating parasite density was not associated with mortality (OR 1.02 for a 6-fold increase [95% CI 0.94-1.11]), so the pathological effects of parasitaemia appear to be mediated entirely by the downstream effects of sequestration. Treatment with an artemisinin derivative decreased mortality compared with quinine (OR 0.64 [95% CI 0.56-0.74]). These estimates were consistent across children and adults (mainly representing African and Asian patients, respectively). Using inverse probability weighting, transfusion was not estimated to be beneficial in children with admission haematocrit values between 15% and 25% (OR 0.99 [95% CI 0.97-1.02]). Except for the effects of artemisinin treatment and transfusion, causal interpretations of these estimates could be biased by unmeasured confounding from severe bacterial sepsis, immunity, and duration of illness. CONCLUSION: These data suggest that moderate anaemia is associated with a reduced risk of death in severe falciparum malaria. This is possibly a direct causal association. The severe anaemia threshold criteria for a definition of severe falciparum malaria should be reconsidered.

Malaria Severity in Mangaluru City in the Southwestern Coastal Region of India.

Dakshina Kannada district in the Southwestern region of Karnataka state, India, including Mangaluru city is endemic to malaria. About 80% of malaria infections in Mangaluru and its surrounding areas are caused by Plasmodium vivax and the remainder is due to Plasmodium falciparum. Malaria-associated clinical complications significantly occur in this region. Here, we report the pathological conditions of 41 cases of fatal severe malaria, admitted to the district government hospital in Mangaluru city during January 2013 through December 2016. The results of clinical, hematological, and biochemical analyses showed that most of these severe malaria cases were associated with thrombocytopenia, anemia, metabolic acidosis, acute respiratory distress, and single or multi-organ dysfunction involving liver, kidney, and brain. Of the 41 fatal malaria cases, 24, 10, and seven patients had P. vivax, P. falciparum, and P. vivax and P. falciparum mixed infections, respectively. These data suggest that besides P. falciparum that is known to extensively cause severe and fatal malaria illnesses, P. vivax causes fatal illnesses substantially in this region, an observation that is consistent with recent findings in other regions.

Identifying the Components of Acidosis in Patients With Severe Plasmodium falciparum Malaria Using Metabolomics.

BACKGROUND: Acidosis in severe Plasmodium falciparum malaria is associated with high mortality, yet the pathogenesis remains incompletely understood. The aim of this study was to determine the nature and source of metabolic acids contributing to acidosis in patients with severe falciparum malaria. METHODS: A prospective observational study was conducted to characterize circulating acids in adults with P. falciparum malaria (n = 107) and healthy controls (n = 45) from Bangladesh using high-resolution liquid chromatography-mass spectrometry metabolomics. Additional in vitro P. falciparum culture studies were performed to determine if parasites release the acids detected in plasma from patients with severe malaria acidosis. RESULTS: We identified previously unmeasured plasma acids strongly associated with acidosis in severe malaria. Metabolomic analysis of P. falciparum parasites in vitro showed no evidence that these acids are released by the parasite during its life cycle. Instead, 10 of the plasma acids could be mapped to a gut microbial origin. Patients with malaria had low L-citrulline levels, a plasma marker indicating reduced gut barrier integrity. Longitudinal data showed the clearance of these newly identified acids was delayed in fatal cases. CONCLUSIONS: These data suggest that a compromise in intestinal barrier function may contribute significantly to the pathogenesis of life-threatening acidosis in severe falciparum malaria. CLINICAL TRIALS REGISTRATION: NCT02451904.

Acidosis and acute kidney injury in severe malaria.

BACKGROUND: In severe falciparum malaria metabolic acidosis and acute kidney injury (AKI) are independent predictors of a fatal outcome in all age groups. The relationship between plasma acids, urine acids and renal function was investigated in adult patients with acute falciparum malaria. METHODS: Plasma and urinary acids which previously showed increased concentrations in proportion to disease severity in patients with severe falciparum malaria were quantified. Patients with uncomplicated malaria, sepsis and healthy volunteers served as comparator groups. Multiple regression and multivariate analysis were used to assess the relationship between organic acid concentrations and clinical syndromes, in particular AKI. RESULTS: Patients with severe malaria (n = 90), uncomplicated malaria (n = 94), non-malaria sepsis (n = 19), and healthy volunteers (n = 61) were included. Univariate analysis showed that both plasma and creatinine-adjusted urine concentrations of p-hydroxyphenyllactic acid (pHPLA) were higher in severe malaria patients with AKI (p < 0.001). Multiple regression analysis, including plasma or creatinine-adjusted urinary acids, and PfHRP2 as parasite biomass marker as independent variables, showed that pHPLA was independently associated with plasma creatinine (ß = 0.827) and urine creatinine (ß = 0.226). Principal component analysis, including four plasma acids and seven urinary acids separated a group of patients with AKI, which was mainly driven by pHPLA concentrations. CONCLUSIONS: Both plasma and urine concentrations of pHPLA closely correlate with AKI in patients with severe falciparum malaria. Further studies will need to assess the potential nephrotoxic properties of pHPLA.

Severe malaria in children: A descriptive report from Kinshasa, the Democratic Republic of Congo.

The decline of susceptibility of Plasmodium falciparum to chloroquine and sulfadoxine-pyrimethamine resulted in the change of drug policy. This policy has probably changed the facies of the severe form of malaria. A prospective study was conducted in Kinshasa, the Democratic Republic of Congo. Data on children aged ≤13 years, diagnosed with severe malaria were analyzed. In total, 378 children were included with an overall median age of 8 years (age range: 1-13 years). Dark urine was seen in 25.1% of cases. Metabolic acidosis (85.2%), hypoglycemia (62.2%) and hemoglobin ≤5 g/dl (39.1%) were the common laboratories features. Severe malaria anemia, cerebral malaria and Blackwater fever (BWF) were found in 39.1, 30.1 and 25.4%, respectively. Mortality rate was 4%. BWF emerges as a frequent form of severe malaria in our midst. Availing artemisin-based combination treatments in the health care system is a priority to reduce the incidence of BWF in our environment.

Black water fever associated with acute renal failure among Congolese children in Kinshasa.

Acute renal failure (ARF) is reported in some severe forms of malaria such as black water fever (BWF). It is associated with a high mortality rate and can be managed effectively with adequate renal replacement. A prospective survey of children with dark urine after a malarial infection with Plasmodium falciparum was coupled with a chart review study of patients managed in the past 11 years in the Pediatrics' Kinshasa University Hospital. Eighty-nine cases of ARF were identified, but data from only 63 patients were available, of whom 44 (69.8%) had severe malaria (39 with BWF and 5 with cerebral malaria). The mean age of the patients was 8.2±1.73 years. Of the 39 cases of BWF, an association with quinine ingestion was observed in 32 children (82%). Urea and creatinine levels were elevated in all cases (135.4±88.2 and 3.83±2.81 mg/dL, respectively). Oligo-anuria was observed in 44.4%, severe metabolic acidosis (bicarbonate<15 mEq/L) in 61.5% and hyponatremia (<130 mEq/L) in 33.3%. Peritoneal dialysis was required in 36 patients, including 20 with BWF. The remaining patients were managed with conservative treatment. Twenty-eight children (44.4%), including 20 on dialysis, fully recovered and 14 died (22.2%), including eight cases of BWF. Our study suggests that ARF is commonly associated with BWF in Congolese children. Elevated urea and creatinine and severe metabolic acidosis were observed more often than other clinical/metabolic disturbances. Severe renal impairment remains a significant complication with a high mortality rate in low-resource settings.

Cardiac function in Ghanaian children with severe malaria.

PURPOSE: The aim was to assess whether impaired cardiac function contributes to symptoms of severe malaria in general or to metabolic acidosis in particular in children living in endemic regions. METHODS: In a prospective observational investigation, 183 children with severe malaria were investigated for hemodynamic status and cardiac function upon admission (day 0) and after recovery (day 42). Cardiac function parameters were assessed by cardiac ultrasonography. Blood gas analyses and cardiac enzymes were measured at hospitalization and follow-up. Differences in subgroups with and without metabolic acidosis as well as other severe malaria-defining symptoms and conditions were assessed. RESULTS: Cardiac index (CI) was significantly increased on day 0 compared to day 42 (5.8 ml/m(2), SD ± 1.8 ml/m(2), versus 4.7 ml/m(2), SD ± 1.4 ml/m(2); P < 0.001). CI correlated negatively with hemoglobin levels but not with parameters indicating impaired tissue perfusion or metabolic acidosis. Parasite levels had a significant influence on metabolic acidosis but not on CI. Alterations related to cardiac function, hemoglobin levels and metabolic acidosis were most prominent in children younger than 2 years. CONCLUSION: Increased CI reflecting high output status is associated with low hemoglobin levels while metabolic acidosis is linked to parasite levels.

Metabolic acidosis induced by Plasmodium falciparum intraerythrocytic stages alters blood-brain barrier integrity.

The pathogenesis of cerebral malaria (CM) remains largely unknown. There is growing evidence that combination of both parasite and host factors could be involved in blood-brain barrier (BBB) breakdown. However, lack of adequate in vitro model of human BBB so far hampered molecular studies. In this article, we propose the use of hCMEC/D3 cells, a well-established human cerebral microvascular endothelial cell (EC) line, to study BBB breakdown induced by Plasmodium falciparum-parasitized red blood cells and environmental conditions. We show that coculture of parasitized erythrocytes with hCMEC/D3 cells induces cell adhesion and paracellular permeability increase, which correlates with disorganization of zonula occludens protein 1 expression pattern. Permeability increase and modification of tight junction proteins distribution are cytoadhesion independent. Finally, we show that permeability of hCMEC/D3 cell monolayers is mediated through parasite induced metabolic acidosis, which in turns correlates with apoptosis of parasitized erythrocytes. This new coculture model represents a very useful tool, which will improve the knowledge of BBB breakdown and the development of adjuvant therapies, together with antiparasitic drugs.

Recovery of endothelial function in severe falciparum malaria: relationship with improvement in plasma L-arginine and blood lactate concentrations.

BACKGROUND: Severe malaria is characterized by microvascular obstruction, endothelial dysfunction, and reduced levels of L-arginine and nitric oxide (NO). L-Arginine infusion improves endothelial function in moderately severe malaria. Neither the longitudinal course of endothelial dysfunction nor factors associated with recovery have been characterized in severe malaria. METHODS: Endothelial function was measured longitudinally in adults with severe malaria (n = 49) or moderately severe malaria (n = 48) in Indonesia, using reactive hyperemia peripheral arterial tonometry (RH-PAT). In a mixed-effects model, changes in RH-PAT index values in patients with severe malaria were related to changes in parasitemia, lactate, acidosis, and plasma L-arginine concentrations. RESULTS: Among patients with severe malaria, the proportion with endothelial dysfunction fell from 94% (46/49 patients) to 14% (6/42 patients) before discharge or death (P < .001). In severe malaria, the median time to normal endothelial function was 49 h (interquartile range, 20-70 h) after the start of antimalarial therapy. The mean increase in L-arginine concentrations in patients with severe malaria was 11 micromol/L/24 h (95% confidence interval [CI], 9-13 micromol/L/24 h), from a baseline of 49 micromol/L (95% CI, 37-45 micromol/L). Improvement of endothelial function in patients with severe malaria correlated with increasing levels of L-arginine (r = 0.56; P = .008) and decreasing levels of lactate (r = -0.44; P = .001). CONCLUSIONS: Recovery of endothelial function in severe malaria is associated with recovery from hypoargininemia and lactic acidosis. Agents that can improve endothelial NO production and endothelial function, such as L-arginine, may have potential as adjunctive therapy early during the course of severe malaria.

Protozoa involved in butyric rather than lactic fermentative pattern during latent acidosis in sheep.

We used six ruminally cannulated Texel wethers to study the relative role of protozoa and lactate-metabolizing bacteria in ruminal fermentative patterns during an induced latent acidosis. The sheep were fed an alfalfa hay diet (H) and latent acidosis was induced, following a short transition period of one week, with a grain-rich acidotic diet (W, 60% wheat + 40% alfalfa hay). Ruminal pH, ruminal volatile fatty acids (VFA), lactate and NH3 concentrations, protozoa and lactate-utilizing bacterial counts, the relative proportions of three main bacteria implicated in lactate metabolism (a lactate-producing species, Streptococcus bovis, and two lactate-utilizing species, Selenomonas ruminantium, and Megasphaera elsdenii) using specific 16S-rRNA-targeting oligonucleotide probes, and lactate dehydrogenase (LDH) activity were determined for both diets. The pH parameters (mean, minimum, maximum, time and area under pH 6.0 and 5.5) measured with the W diet were indicative of a latent (i.e., subacute and maintained) acidosis. However, a butyric rather than lactic latent acidosis was observed in this study. Total ruminal lactate concentration remained at low levels with the acidotic diet (< 4 mmol x L(-1)), but changes were observed in VFA composition, which was oriented towards butyrate at the expense of acetate (P < 0.05), while propionate remained constant. In agreement with the low ruminal lactate concentration, no changes in the proportion of S. bovis 16S-rRNA were observed. The lactate-metabolizing bacterial population also remained fairly constant in number, proportion and activity. The increase in butyrate concentration was accompanied by a proliferation of entodiniomorphs (P < 0.01). These results suggest that the protozoa limited lactate accumulation and possibly also the decrease in pH during latent acidosis. Experiments with defaunated and faunated sheep could provide further evidence of the role of protozoa in the development of rumen latent acidosis.

Hypokalemia in children with severe falciparum malaria.

OBJECTIVES: Acidosis is now recognized as an important component of the severe malaria syndrome and a predictor of fatal outcome. Alterations in plasma potassium concentrations are commonly associated with acidosis. To date, there is little information about the changes in potassium in severe malaria. DESIGN: Prospective study examining the changes in plasma potassium in the first 24 hrs following admission in children with severe malaria. Urinary fractional excretion of potassium and the transtubular gradient of potassium were examined at admission. SETTING: High-dependency unit on the coast of Kenya. PATIENTS: Kenyan children admitted to hospital with clinical features of severe malaria (impaired consciousness or deep breathing) complicated by acidosis (base deficit >8). INTERVENTIONS: Children received standard therapy for severe malaria; in addition, they received boluses of either 0.9% saline or 4.5% human albumin solution to correct hypovolemia, and intravenous potassium replacement was prescribed to children who developed hypokalemia (plasma potassium <3 mmol/L). MEASUREMENTS AND MAIN RESULTS: Thirty-eight Kenyan children were recruited with severe malaria and acidosis. At admission, serum potassium was normal (3-5.5 mmol/L) in 31 (81.6%) and low (<3 mmol/L) in four (11%) children, and three (6.3%) children had hyperkalemia (>5.5 mmol/L). Plasma potassium decreased rapidly within 4-8 hrs of admission: 15 (40%) patients were hypokalemic (<3 mmol/L); of these, five (13%) had plasma potassium of <2.5 mmol/L. Fractional excretion of potassium and the transtubular gradient of potassium were above normal range, indicating renal potassium loss. CONCLUSIONS: Hypokalemia is a common complication of severe malaria; however, it is often not apparent on admission. On correction of acidosis, plasma potassium decreases precipitously, and thus careful, serial monitoring of serum potassium is suggested in patients with severe malaria complicated by acidosis.

The pathophysiologic and prognostic significance of acidosis in severe adult malaria.

OBJECTIVE: To investigate the pathophysiology and prognostic significance of acidosis in severe adult malaria. DESIGN: Cohort study. SETTING: The intensive care unit of an infectious diseases hospital in southern Vietnam. PATIENTS: Three hundred forty-six consecutive adult patients with severe falciparum malaria. INTERVENTIONS: Measurements of baseline venous lactate and pyruvate concentrations and an extensive range of clinical and laboratory variables were made, and patients were followed up carefully until death or discharge from the hospital. Admission arterial blood pH and gas tensions were recorded in 296 patients, and hepatic venous sampling was done in 12 patients. MEASUREMENTS AND MAIN RESULTS: Overall, 198 (67%) patients were acidotic (standard base deficit [SBD], >3.3 mmol/L [n = 196], or arterial Pco2, >45 torr [6 kPa] [n = 3]). Hyperlactatemia (plasma lactate, >4 mmol/L) occurred in 120 (35%) of the 346 patients and was associated significantly with acidosis (p < .0001). The hepatosplanchnic lactate extraction ratio was negatively correlated with mixed venous plasma lactate (r2 = .50; p = .006). Hyperlactatemia, metabolic acidosis (SBD, >3.3), and acidemia (pH <7.35) were strongly positively associated with a fatal outcome (relative risks [95% confidence interval], 4.3 [range, 1.8-10.6], 5.0 [range, 3.0-8.1], and 2.7 [range, 1.8-4.1], respectively). The SBD was the single best clinical or laboratory predictor of fatal outcome. The overall median lactate/pyruvate ratio was raised at 30.6 (range, 20.6-62.3; normal range, <15), suggesting hypoxia and anaerobic glycolysis, and was significantly higher in fatal cases (p < .0001). In an additive multivariate model, the two main independent contributors to metabolic acidosis were plasma creatinine, as a measure of renal dysfunction, and venous plasma lactate, together accounting for 63% of the variance in SBD. In univariate analyses, they contributed 29% and 38%, respectively. CONCLUSIONS: These results confirm the importance of acidosis in the pathophysiology of severe adult malaria and suggest a multifactorial origin involving tissue hypoxia, liver dysfunction, and impaired renal handling of bicarbonate.

Transfusion for respiratory distress in life-threatening childhood malaria.

We have prospectively collected information during resuscitation in 24 children with life-threatening malaria. All had clinical respiratory distress and 16 were severely anemic (hemoglobin < or = 5 g/dL) on admission. Central venous pressure (CVP) measurements were normal (< or = 5 cm of water) prior to treatment but all had a metabolic acidosis. The geometric mean lactate level was significantly higher in children admitted with severe anemia than in those without severe anemia (11.2 mmol/l versus 4.2 mmol/l; P = 0.009). Hypovolemia (a CVP on admission < 0 cm of water) was associated, although not significantly, with a higher admission plasma creatinine concentration (94 mumol/l versus 64 mumol/l; P = 0.06) and probably contributed to the severely reduced creatinine clearances (0-39 ml/min/1.73 ml2) found in 12 of the 13 children in whom this was assessed in the first 24 hr. Treatment resulted in a rapid decrease in blood lactate in 16 of the 13 children in whom this was assessed in the first 24 hr. Treatment resulted in a rapid decrease in blood lactate in 16 of the 20 children transfused, which was most dramatic in severely anemic children, who were rapidly resuscitated. In nonanemic children, early and rapid administration of normal saline usually resulted in both metabolic and clinical improvement. However, in three children, two of whom died, acidosis persisted despite resuscitation. Metabolic acidosis often accounts for respiratory distress in life-threatening childhood malaria. Severe anemia and hypovolemia appear to play major roles in its pathogenesis, are readily treatable, and there appears to be little risk of congestive cardiac failure even with an aggressive approach to fluid replacement.

Deep breathing in children with severe malaria: indicator of metabolic acidosis and poor outcome.

Despite the frequent association of respiratory symptoms and signs with malarial morbidity and mortality in sub-Saharan Africa, the value of individual symptoms and signs has rarely been assessed. We have prospectively examined the association of individual clinical findings with the summary diagnosis of respiratory distress, outcome, and the presence of metabolic acidosis in children admitted with severe malaria to a Kenyan district hospital. Respiratory distress was present in 119 of the 350 children included in the study and in 23 of the 30 deaths (relative risk = 6.5, 95% confidence interval = 2.8-14.4). The features of a history of dyspnea, nasal flaring, and indrawing or deep breathing (Kussmaul's respiration) were individually most closely associated with the summary diagnosis of respiratory distress. Of these, deep breathing, which was sensitive (91%) and specific (83%) for the presence of severe metabolic acidosis (base excess < or = -12), is the best candidate sign to represent the prognostically important syndrome of malarial respiratory distress. Therefore, it warrants further prospective evaluation in different clinical settings and areas of different malaria endemicity.

Acid-base status in paediatric Plasmodium falciparum malaria.

We measured the acid-base status of children with falciparum malaria in order to determine the prognostic significance and rate of resolution of acidaemia in patients with severe disease. We prospectively studied 141 Malawian children who were admitted to Hospital, with falciparum malaria, 60 of whom had cerebral malaria (unrousable coma, unable to localize a painful stimulus). Of the 60 patients with cerebral malaria 25 (42%) were acidaemic (capillary blood pH < 7.3); of 81 children with uncomplicated malaria 4 (5%) were acidaemic (p < 0.0001). Eleven patients died; of these, eight presented with cerebral malaria, eight with acidaemia and seven with both. The strong association of altered acid-base status with disease severity and mortality was independent of other previously identified predictors of illness and death in malaria. Acidaemia was not associated with shock, bacteraemia or hypoxaemia. Acidaemic patients had a slower mean respiratory rate and a higher incidence of respiratory rhythm abnormalities than other patients, suggesting that acidaemia is in part the result of inadequate respiratory compensation for metabolic acidosis. Although acidaemia is quickly corrected by fluids and antimalarial drugs, specific therapy to correct acidaemia needs evaluation in children with severe malaria.