Reducing aerosol dispersion by high flow therapy in COVID-19: High resolution computational fluid dynamics simulations of particle behavior during high velocity nasal insufflation with a simple surgical mask.

Objective: All respiratory care represents some risk of becoming an aerosol-generating procedure (AGP) during COVID-19 patient management. Personal protective equipment (PPE) and environmental control/engineering is advised. High velocity nasal insufflation (HVNI) and high flow nasal cannula (HFNC) deliver high flow oxygen (HFO) therapy, established as a competent means of supporting oxygenation for acute respiratory distress patients, including that precipitated by COVID-19. Although unlikely to present a disproportionate particle dispersal risk, AGP from HFO continues to be a concern. Previously, we published a preliminary model. Here, we present a subsequent highresolution simulation (higher complexity/reliability) to provide a more accurate and precise particle characterization on the effect of surgical masks on patients during HVNI, low-flow oxygen therapy (LFO2), and tidal breathing. Methods: This in silico modeling study of HVNI, LFO2, and tidal breathing presents ANSYS fluent computational fluid dynamics simulations that evaluate the effect of Type I surgical mask use over patient face on particle/droplet behavior. Results: This in silico modeling simulation study of HVNI (40 L min-1) with a simulated surgical mask suggests 88.8% capture of exhaled particulate mass in the mask, compared to 77.4% in LFO2 (6 L min-1) capture, with particle distribution escaping to the room (> 1 m from face) lower for HVNI+Mask versus LFO2+Mask (8.23% vs 17.2%). The overwhelming proportion of particulate escape was associated with mask-fit designed model gaps. Particle dispersion was associated with lower velocity. Conclusions: These simulations suggest employing a surgical mask over the HVNI interface may be useful in reduction of particulate mass distribution associated with AGPs.

The effects of Tween-80 on the integrity of solutions of capsaicin: useful information for performing tussigenic challenges.

BACKGROUND: Because variable results of capsaicin challenges may be due to the incomplete solubility of capsaicin, we sought to determine if the use of Tween-80 in solutions of capsaicin improves actual concentrations of freshly prepared and stored solutions. METHODS: Capsaicin solutions ranging from 0.5-128 muM were mixed with and without Tween-80. Samples of various concentrations were then stored under 4 environmental conditions: 4 degrees C, protected from light; room temperature, protected from light; room temperature, exposed to light; -20 degrees C. All samples were analyzed initially, and at 2 and 4 months. RESULTS: While freshly prepared solutions with Tween-80 had consistently higher concentrations than those prepared without Tween-80 (83% vs. 69%), Tween-80 does not facilitate complete solubility. For solutions stored at 4 degrees C and protected from light, there was a significant decrease after 2 months in low concentration solutions of both the Tween-80 and non-Tween-80 solutions. Both Tween-80 and non-Tween-80 containing solutions significantly decreased in concentration after 2 months when stored at room temperature and protected from light, room temperature and exposed to light, and -20 degrees C. Concentrations of solutions made of 4 muM or higher are stable when stored at 4 degrees C and protected from light for 4 months. CONCLUSION: While the inherent difficulty of forcing capsaicin into solution cannot be eliminated, it can be improved with Tween-80. However, the addition of Tween-80 does not prevent the breakdown of stored capsaicin solutions. We recommend preparing and storing capsaicin solutions according to the methods and results of this study.

Anemia in critical care patients: incidence, etiology, impact, management, and use of treatment guidelines and protocols.

PURPOSE: The incidence, etiology, impact, and management of anemia in critical care patients and the development of treatment guidelines and protocols for the management of anemia in this patient population are discussed. SUMMARY: Most patients in intensive care units develop anemia as a result of blood losses, nutritional deficiencies, hemolysis, myelosuppression, renal insufficiency, inflammation, infection, or another disease process. Anemia can have an adverse impact on critically ill patients with severe ischemic heart disease or cerebrovascular disease and patients undergoing surgery. The use of blood conservation measures and restrictive blood transfusion strategies can circumvent problems associated with transfusion. Epoetin alfa increases hemoglobin concentrations and reduces the need for transfusion in critical care patients, including surgical patients with large anticipated blood losses. Epoetin alfa also appears to be effective for managing anemia in patients with multiple organ dysfunction syndrome. Iron supplementation is needed by most patients receiving erythropoietic therapy. Iron supplementation without erythropoietic therapy is inadequate to correct anemia unrelated to iron deficiency. Concerns have been raised about a possible increased risk for infection when parenteral iron therapy is used in critical care patients. Developing treatment guidelines or protocols for managing anemia in critical care patients can minimize the need for transfusions and improve prescribing of erythropoietic therapy. CONCLUSION: Epoetin alfa can play an important role in managing anemia in critical care patients, thereby minimizing patient exposure to transfusion-related risks and optimizing the use of the limited blood supply. There is currently no data available for use of darbepoetin in this manner.

Linezolid-associated serotonin syndrome after concomitant treatment with citalopram and mirtazepine in a critically ill bone marrow transplant recipient.

Linezolid was initially discovered as an antidepressant because of its effect on blocking intracellular metabolism of serotonin, norepinephrine, and other biogenic amines. As time passed, it was realized that linezolid possessed antibacterial activity, and linezolid has been developed and marketed as such. In medicine we are quick to categorize drugs into specific classes as a mechanism to recall indication and use. By classifying linezolid as an antibacterial, it is common to forget about its antidepressant roots. A case report involving linezolid with citalopram and mirtazepine in the precipitation of serotonin syndrome in a critically ill bone marrow transplant patient is described in this article.

The role of resistance and impact on appropriate antimicrobial use.

Antibiotic resistance is a subject of growing concern throughout the medical community. Addressing drug resistance requires that practitioners understand the mechanisms of resistance and the methods of treating infections effectively while minimizing the emergence of resistant organisms. When making antibiotic selections, clinicians should consider a number of factors in addition to the drug's antimicrobial activity. These include the epidemiology of regional resistance and the antibiotic's pharmacokinetic and pharmacodynamic profile. Combination therapies should be considered and appropriate durations of therapy addressed. Developing clear practice guidelines for managing infectious disease can help practitioners reduce inappropriate antibiotic use and minimize the emergence of resistance.

Improving adherence with antimicrobial therapy for respiratory tract infections: a discussion of directly observed therapy (DOT) and short-course therapies.

Although some of the variables associated with adherence (eg, patient age, place of residence) cannot be influenced, others are very amenable to modifications. Levels of adherence correlate with the convenience of dosage regimens, as shown in a number of clinical trials. Therefore, antimicrobial agents that are well accepted by patients should be considered whenever feasible. Such agents include those that enable shortterm therapy with the fewest daily doses and shortest effective treatment regimens. DOT, a cost-effective and clinically effective approach for certain chronic conditions, may also have practical implications for the treatment of acute infectious diseases, such as CAP, AECB, and otitis media. Although there are a number of challenges to the implementation of DOT for these conditions, such an approach may be beneficial, particularly when short-course antibiotic therapy is indicated and appropriate candidates are identified for treatment.

Chemical analysis of freshly prepared and stored capsaicin solutions: implications for tussigenic challenges.

The purpose of this study was to assess the stability of stored capsaicin solutions and the actual concentrations of prepared solutions. Capsaicin solutions ranging in concentration from 0.5 to 128 microM were mixed and analyzed using high performance liquid chromatography. Samples of varying concentrations were then stored under 4 environmental conditions: 4 degrees C and protected from light, room temperature (RT) exposed to light, RT protected from light, and -20 degrees C and protected from light. The concentrations were measured every other month for 1 year. Actual concentrations of freshly prepared solutions were on average 88.3% of predicted. For solutions stored at 4 degrees C, there was a decrease only in the lower concentrations (0.5, 1, and 2 microM) after 2 months (P=0.003). Solutions stored at RT exposed to light decreased in concentration after 6 months (P=0.020), and solutions stored at RT protected from light decreased in concentration after 4 months (P=0.026). The group stored at -20 degrees C decreased in concentration after 1 year (P=0.033). We conclude that the actual concentration of capsaicin solution is less than predicted, and solutions of 4 microM or higher concentration are stable for 1 year if stored at 4 degrees C protected from light.