Delayed haemolysis was found only in hyperparasitaemic patients treated with artesunate (alone or in combination with quinine) but not in patients with quinine (and other partner drugs). After intravenous artesunate was established as a first-line treatment option for severe malaria in the University Medical Centre Hamburg-Eppendorf, active follow-up to detect haemolysis once a week for a total of four weeks after treatment initiation was implemented. The possibility that some cases of delayed haemolysis had been missed in quinine patients before establishing these active follow-up procedures cannot be ruled out. It appears realistic, however, to assume that delayed haemolysis would have been recognized passively in quinine patients if it was as frequent and clinically relevant. In addition, there are no other reports of delayed haemolysis after quinine available up to date. In contrast, increasing evidence indicates that delayed haemolysis occurs comparatively frequently after parenteral artesunate
[13–16]. Interestingly we could detect delayed haemolysis also in two patients treated with intrarectal artesunate – a finding which had not previously been reported. It has to be noted that patients treated with quinine and additional intrarectal artesunate were more severely ill and had higher initial parasite densities than patients treated primarily with quinine. As hyperparasitaemia has been implicated as a risk factor for delayed haemolysis, parasite densities might be a confounder
The aetiology of delayed haemolysis remains unknown. The fact that mainly hyperparasitaemic patients develop haemolysis may point to the contribution of a mechanism called ‘pitting’. After extraction of blood stage parasites during splenic passage, these once-infected erythrocytes have a reduced life-span compared to naïve erythrocytes with a mean life-span of around 180 hours and with a total removal of pitted erythrocytes after 28 days
[20, 21]. One could postulate an increase of haemolytic activity two weeks after acute malaria due to more or less synchronized destruction of pitted erythrocytes. The proportion of pitted erythrocytes seems to be higher after the use of artemisinins than after quinine – potentially explaining the absence of this adverse effect after use of quinine
[20, 21]. Immune-mediated haemolysis may be another explanation – although Coombs testing in the reports published so far has remained inconclusive. Coombs tests were negative in three patients in the case series by Zoller et al.. In the Belgian-Dutch cohort, half of the tested patients had a positive Coombs test
. In the present study, half of the tested patients had positive direct Coombs test – albeit with different specificity (anti-E and warm autoantibodies). HIV-infection induced immunologic dysfunctions might have played a further role in the development of delayed haemolysis in one patient in this study. Further appropriately designed studies are necessary to clarify the pathophysiological mechanisms behind delayed haemolysis.
It is important to separate the haemolysis of acute malaria from delayed haemolysis after parasitological cure. Also, Hb levels can remain decreased during weeks two or three in patients slowly recovering from severe malarial anaemia without showing a new onset of haemolytic activity. It is, therefore, relevant to precisely define delayed haemolysis by applying biochemical parameters over time. In this study, delayed haemolysis was defined as a decrease in Hb (median Hb of week three lower than in week two) in combination with a rise in median LDH (median LDH of week three higher than in week two). This definition was selected based on the known time course of delayed haemolysis in the case series reported recently
[13–16]. Median values of one week were used to correct for any potential outliers (e.g. transfusions or fluid resuscitation), which would have inappropriately influenced the mean values of one week.
The only other adverse event seen in patients treated with artesunate was development of acute renal failure after treatment was started. Renal failure might be due to malaria itself
. In an animal model, however, it was shown that intravenous artesunate leads to increased diuresis and decreased glomerular filtration rate
. Two case reports confirmed an increased diuresis in humans after infusion of intravenous artesunate – but no decrease in renal function was seen
. Creatinine levels in the three patients with acute renal failure after parenteral artesunate in this report normalized rapidly in the first week and no dialysis was necessary.
Quinine confers the risk of a wide spectrum of adverse events and complications. Cinchonism consisting of gastrointestinal disturbances, tinnitus, hearing loss, vasodilatation and headaches are comparatively common and reversible soon after the drug exposure has discontinued
. A potentially dangerous adverse event is hypoglycaemia – which occurred in every third patient in this study. Hypoglycaemic episodes are significantly more frequent in patients treated with quinine than in patients treated with artesunate
. Quinine (as well as quinidine – the prototypic drug of class Ia antiarrythmics) leads to changes in cardiac electrophysiology – mainly in a prolongation of the ventricular repolarization as emphasized by a prolongation of the corrected QT-interval and predisposing to the development of potentially lethal torsade de pointe arrhythmia
. Three patients developed prolongation of the QT-interval and the dose of quinine had to be reduced.
Several factors limit this study. Adverse events might be underreported in a retrospective chart review – either because patients do not or are unable to mention onset of new signs and symptoms because active screening is incomplete or simply because of incomplete chart entries. Furthermore, follow-up was not standardized for all patients which might hamper comparison between groups. Patients who were initially severely ill tended to have more extensive follow-up and adverse events might have been detected more frequently. These aspects may limit the generalizability of findings to patients with severe malaria. Moreover, the sample size was relatively small. A multi-centre retrospective approach might provide a larger sample size, although further heterogeneity in treatment regimens could add a further limitation. To define severe malaria, the German guidelines for the diagnosis and treatment of malaria issued in 2006 were used. In 2011, a new updated guideline has been published. In this revised guideline, elevated bilirubin and elevated LFTs have been omitted as severity criteria
. The 2006 guidelines were consistently applied for this study because it was the aim to yield a homogenous study population and because the majority of patients were treated prior to 2011.