Do Hemolyzed Potassium Specimens Need to be Repeated?

Background

In the emergency department (ED), hyperkalemia in the presence of hemolysis is common. Elevated hemolyzed potassium levels are often repeated by emergency physicians to confirm pseudohyperkalemia and to exclude a life-threatening true hyperkalemia.

Objectives

We hypothesize that in patients with a normal renal function, elevated hemolyzed potassium, and normal electrocardiogram (ECG), there may not be a need for further treatment or repeat testing and increased length of stay.

Methods

Data were prospectively enrolled patients presenting to the ED from July 2011 to February 2012. All adult subjects who had a hemolyzed potassium level ≥ 5.5 mEq/dL underwent a repeat potassium level and ECG. The incidence of true hyperkalemia in this population was measured.

Results

A total of 45 patients were enrolled. The overall median age was 52 years (range 25–83 years); 22 were female (49%). In patients with hyperkalemia on initial blood draw and glomerular filtration rate (GFR) ≥ 60 (n = 45), the negative predictive value was 97.8% (95% confidence interval [CI] 88.2–99.9%). When patients had hyperkalemia on initial blood draw, GFR ≥ 60, and a normal ECG (n = 42), the negative predictive value was 100% (95% CI 93.1–100%).

Conclusions

In the setting of hemolysis, GFR ≥ 60 mL/min in conjunction with a normal ECG is a reliable predictor of pseudohyperkalemia and may eliminate the need for repeat testing. In patients with a normal GFR who are otherwise deemed safe for discharge, our results indicate there is no need for repeat testing.     

Impact of pharmacy outreach services on blood pressure management in the elderly community of Hong Kong

Aim: To investigate the impact of the Pharmacy Outreach Service (POS) on blood pressure (BP) and disease knowledge among community‐dwelling elderly patients with hypertension, and to evaluate the sustainability of such impact of POS. Methods: A prospective open‐labeled study of elderly adults (aged ≥65 years) with hypertension (BP ≥140/90 mmHg for non‐diabetics and ≥130/80 mmHg for diabetics) was carried out at seven elderly community centers from July 2008 to March 2010. Pharmacists provided BP monitoring, medication review and disease knowledge assessment. The target BP was <140/90 mmHg for non‐diabetics and <130/80 mmHg for diabetics. The primary outcome was BP change, whereas the secondary outcome was the change of disease knowledge of hypertension. All outcomes were compared between baseline and the last visit. For POS 2008/09 participants, BP was compared between values obtained during POS 2008/09 and 2009/10. Results: A total of 97 participants were recruited. Systolic BP reduced significantly from 152.38 ± 18.80 mmHg to 147.04 ± 20.72 mmHg (P = 0.021), and diastolic BP reduced from 73.84 ± 11.36 mmHg to 71.03 ± 10.97 mmHg (P = 0.010). Cumulative reductions in mean systolic BP and diastolic BP throughout the 2‐year study period were 21.39 ± 24.72 mmHg and 9.88 ± 13.48 mmHg, respectively (P < 0.001). A 12% increase in the at‐goal rate was observed in new participants recruited in 2009 (P = 0.039). Disease knowledge of hypertension improved significantly (P < 0.005), particularly in areas that included the definition of hypertension, diet and lifestyle modification. Conclusions: The POS might improve blood pressure control, hypertension and diabetes knowledge in elderly adults with hypertension in Hong Kong. The effect on blood pressure improvement was sustainable. Geriatr Gerontol Int 2013; 13: 175–181.     

Relevance of Resistance Against Direct Acting Antiviral Agents in Hepatitis C Virus Infection – What Technology do we Really Need in Clinical Practice?

The hepatitis C virus (HCV) is extremely variable and exposure to direct acting antiviral drugs (DAA) leads to rapid emergence of resistance associated variants (RAV). Different sequencing approaches – most notably population sequencing, clonal sequencing, and next generation or deep sequencing – can detect minor variants with different detection thresholds. While it is clear that RAV become more frequent during DAA-containing antiviral therapy especially in those individuals that suffer virologic failure, i.e., breakthrough or relapse, it is unclear whether the presence of RAV’s at a certain frequency at baseline is associated with poorer treatment outcomes. Resistance testing has no role in routine clinical care today. More data from studies using sensitive sequencing techniques will be required to determine whether it may become clinically important in the near future as more DAA from different classes become available and clinicians face an increasing number of patients who have previously been exposed to DAA.     

Interactions between the volume effects of hydroxyethyl starch 130/0.4 and Ringer′s acetate

Introduction

The turnover of Ringer´s solutions is greatly dependent on the physiological situation, such as the presence of dehydration or anaesthesia. The present study evaluates whether the kinetics is affected by previous infusion of colloid fluid.

Methods

Ten male volunteers with a mean age of 22 years underwent three infusion experiments, on separate days and in random order. The experiments included 10 mL/kg of 6% hydroxyethyl starch 130/0.4 (Voluven™), 20 mL/kg of Ringer''s acetate, and a combination of both, where Ringer´s was administered 75 minutes after the starch infusion ended. The kinetics of the volume expansion was analysed by non-linear least- squares regression, based on urinary excretion and serial measurement of blood haemoglobin concentration for up to 420 minutes.

Results

The mean volume of distribution of the starch was 3.12 L which agreed well with the plasma volume (3.14 L) estimated by anthropometry. The volume expansion following the infusion of starch showed monoexponential elimination kinetics with a half-life of two hours. Two interaction effects were found when Ringer´s acetate was infused after the starch. First, there was a higher tendency for Ringer´s acetate to distribute to a peripheral compartment at the expense of the plasma volume expansion. The translocated amount of Ringer´s was 70% higher when HES had been infused earlier. Second, the elimination half-life of Ringer´s acetate was five times longer when administered after the starch (88 versus 497 minutes, P <0.02).

Conclusions

Starch promoted peripheral accumulation of the later infused Ringer´s acetate solution and markedly prolonged the elimination half-life.

Trial registration

ClinicalTrials.gov: {"type":"clinical-trial","attrs":{"text":"NCT01195025","term_id":"NCT01195025"}}NCT01195025     

RH5–Basigin interaction plays a major role in the host tropism of Plasmodium falciparum

Plasmodium falciparum, the cause of almost all human malaria mortality, is a member of the Laverania subgenus which infects African great apes. Interestingly, Laverania parasites exhibit strict host specificity in their natural environment: P. reichenowi, P. billcollinsi, and P. gaboni infect only chimpanzees; P. praefalciparum, P. blacklocki, and P. adleri are restricted to gorillas, and P. falciparum is pandemic in humans. The molecular mechanism(s) responsible for these host restrictions are not understood, although the interaction between the parasite blood-stage invasion ligand EBA175 and the host erythrocyte receptor Glycophorin-A (GYPA) has been implicated previously. We reexamined the role of the EBA175–GYPA interaction in host tropism using recombinant proteins and biophysical assays and found that EBA175 orthologs from the chimpanzee-restricted parasites P. reichenowi and P. billcollinsi both bound to human GYPA with affinities similar to that of P. falciparum, suggesting that the EBA175–GYPA interaction is unlikely to be the sole determinant of Laverania host specificity. We next investigated the contribution of the recently discovered Reticulocyte-binding protein Homolog 5 (RH5)–Basigin (BSG) interaction in host-species selectivity and found that P. falciparum RH5 bound chimpanzee BSG with a significantly lower affinity than human BSG and did not bind gorilla BSG, mirroring the known host tropism of P. falciparum. Using site-directed mutagenesis, we identified residues in BSG that are responsible for the species specificity of PfRH5 binding. Consistent with the essential role of the PfRH5–BSG interaction in erythrocyte invasion, we conclude that species-specific differences in the BSG receptor provide a molecular explanation for the restriction of P. falciparum to its human host.The most deadly of the malaria parasites, Plasmodium falciparum, is highly divergent from the other species of Plasmodium known to infect humans (1–3), with its closest relatives comprising a group of chimpanzee and gorilla parasites from the subgenus Laverania (3–7). Despite the origin of P. falciparum as a zoonosis, and the continuing coexistence of humans and apes in West and Central Africa, extensive field studies have failed to detect P. falciparum in wild-living chimpanzees and gorillas (5). Although there are reports of P. falciparum infecting chimpanzees either in certain captive settings (2) or following splenectomy and deliberate transfer of P. falciparum-infected human blood (8–10), the resulting infections have low parasitemia and are not known to result in malignant tertian malaria, suggesting a host-specific barrier for replete infection. The existence of host-specific barriers within the Laverania subgenus is supported further by the strict host specificity exhibited by ape Laverania parasites in the wild: Plasmodium reichenowi, Plasmodium billcollinsi, and Plasmodium gaboni infect only chimpanzees, and Plasmodium praefalciparum, Plasmodium blacklocki, and Plasmodium adleri are restricted to gorillas (3–6).The molecular basis for the host tropism of P. falciparum and other Laverania parasites is not currently understood and is difficult to investigate experimentally, because no ape Laverania parasites have been adapted to in vitro culture, and because ethical considerations clearly preclude the use of endangered African apes for in vivo experiments (3). In principle, the species specificity of known host–parasite interactions could be examined using recombinant proteins, but the technical challenges associated with expressing functional Plasmodium proteins in a recombinant form have made this approach difficult thus far (11). There also are multiple points in the complex Plasmodium life cycle that could represent restriction points, and some evidence suggests that transmission of Laverania to anthropophilic Anopheles species, for example, may be restricted (12). Although several restriction points are possible, the blood stage of Plasmodium infection, which is initiated when host erythrocytes are invaded by the parasite, is of particular interest. Erythrocyte invasion is an obligate stage in the parasite life cycle (13), and the inability of P. falciparum to produce infections of high parasitemia in chimpanzees by transfer of infected blood, despite contrived permissive experimental conditions, suggests that a host-specific barrier for infection exists at the blood stage. Moreover, erythrocyte invasion involves extracellular interactions between several different receptor–ligand pairs which are coevolving rapidly, driven by strong immune selection pressure and functional constraints (14, 15). This rapid coevolution means that interactions between parasite blood-stage ligands and erythrocyte receptors quickly could become host-specific, isolating a certain parasite species within a single host. Given these findings, erythrocyte invasion therefore is likely to represent a significant restriction point in determining host tropism.P. falciparum erythrocyte invasion depends on a partially redundant set of parasite ligands and erythrocyte receptors (14, 16–18), and there is experimental support for the suggestion that at least two of these interactions may be involved in P. falciparum host tropism. The interaction between Plasmodium falciparum Erythrocyte Binding Antigen-175 (PfEBA175) and the erythrocyte receptor Glycophorin-A (GYPA) is important for invasion and is known to require sialic acid residues displayed on GYPA (19, 20). The sialic acid content of human GYPA differs from that of other apes because humans lack a functional cytidine monophosphate-N-acetylneuraminic acid hydroxylase (CMAH) enzyme. Consequently, human GYPA contains only N-Acetylneuraminic acid (Neu5Ac) sialic acids, whereas chimpanzees and gorillas, both of which have an active CMAH gene, contain a mixture of both Neu5Ac and its hydroxylated derivative, N-Glycolylneuraminic acid (Neu5Gc), with Neu5Gc being more abundant (21). This difference in GYPA sialic acid content led Martin et al. (10) to propose that the restriction of P. falciparum to humans results from the sialic acid-binding specificity in the PfEBA175–GYPA interaction. The cocrystal structure of the glycan-binding regions of P. falciparum EBA175 in complex with a Neu5Ac-containing glycan derivative (22) followed by modeling of the equivalent EBA175 sequence from the chimpanzee-restricted parasite, P. reichenowi (23), suggested a structural basis for this binding specificity. However, this hypothesis is inconsistent with a much earlier study by Orlandi et al. (24) in which the binding of native PfEBA175 to human erythrocytes was observed to be potently inhibited by soluble Neu5Gc and oligosaccharides containing Neu5Acα2–3Gal but not by Neu5Ac as a monosaccharide. This glycan-binding specificity was confirmed in a recent biochemical investigation using a recombinant protein consisting of the entire ectodomain of PfEBA175 (25). Furthermore, the sialic acid specificity of PfEBA175 orthologs cannot explain the restriction of ape Laverania parasites to their respective chimpanzee and gorilla hosts, both of which carry a functional CMAH gene (5). Therefore there is reasonable doubt about the importance of the EBA175–GYPA interaction in Laverania host tropism. A second and unrelated invasion ligand, Plasmodium falciparum Reticulocyte-binding protein homolog 5 (PfRH5) has also been implicated in host tropism by governing the ability of P. falciparum to infect New World Aotus monkeys (26, 27). The erythrocyte cell-surface receptor of PfRH5, Basigin (BSG), was identified only recently (28), and so the contribution of the PfRH5–BSG interaction toward determining host-species selectivity in P. falciparum is unknown.We recently have developed technology that enables the recombinant expression of P. falciparum cell-surface and secreted proteins in a functional form using a mammalian expression system (29). We have used this method to identify novel host–parasite interactions (28, 30), but here we apply it to investigate the relative roles of the EBA175–GYPA and PfRH5–BSG interactions as determinants of P. falciparum host tropism.     

Millisecond spatiotemporal dynamics of FRET biosensors by the pair correlation function and the phasor approach to FLIM

Here we present a fluctuation-based approach to biosensor Förster resonance energy transfer (FRET) detection that can measure the molecular flow and signaling activity of proteins in live cells. By simultaneous use of the phasor approach to fluorescence lifetime imaging microscopy (FLIM) and cross–pair correlation function (pCF) analysis along a line scanned in milliseconds, we detect the spatial localization of Rho GTPase activity (biosensor FRET signal) as well as the diffusive route adopted by this active population. In particular we find, for Rac1 and RhoA, distinct gradients of activation (FLIM-FRET) and a molecular flow pattern (pCF analysis) that explains the observed polarized GTPase activity. This multiplexed approach to biosensor FRET detection serves as a unique tool for dissection of the mechanism(s) by which key signaling proteins are spatially and temporally coordinated.     

Therapy and prophylaxis of opportunistic infections in HIV-infected patients: a guideline by the German and Austrian AIDS societies (DAIG/ÖAG) (AWMF 055/066)

Introduction

There was a growing need for practical guidelines for the most common OIs in Germany and Austria under consideration of the local epidemiological conditions.

Materials and methods

The German and Austrian AIDS societies developed these guidelines between March 2010 and November 2011. A structured Medline research was performed for 12 diseases, namely Immune reconstitution inflammatory syndrome, Pneumocystis jiroveci pneumonia, cerebral toxoplasmosis, cytomegalovirus manifestations, candidiasis, herpes simplex virus infections, varizella zoster virus infections, progressive multifocal leucencephalopathy, cryptosporidiosis, cryptococcosis, nontuberculosis mycobacteria infections and tuberculosis. Due to the lack of evidence by randomized controlled trials, part of the guidelines reflects expert opinions. The German version was accepted by the German and Austrian AIDS Societies and was previously published by the Arbeitsgemeinschaft der Wissenschaftlichen Medizinischen Fachgesellschaften (AWMF; German Association of the Scientific Medical Societies).

Conclusion

The review presented here is a translation of a short version of the German–Austrian Guidelines of opportunistic infections in HIV patients. These guidelines are well-accepted in a clinical setting in both Germany and Austria. They lead to a similar treatment of a heterogeneous group of patients in these countries.