Using Zero Balance Ultrafiltration with Dialysate as a Replacement Fluid for Hyperkalemia during Cardiopulmonary Bypass

Avoiding or managing hyperkalemia during cardiac surgery, especially in a patient with chronic renal insufficiency, can be challenging. Hyperkalemic cardioplegia solution is usually administered to achieve and maintain an electrical arrest of the heart. This solution eventually mixes in with the systemic circulation, contributing to elevated systemic potassium levels. Administration of packed red blood cells, hemolysis, tissue damage, and acidosis are also common causes of hyperkalemia. Current strategies to avoid or manage hyperkalemia include minimizing the volume of cardioplegia administered, shifting potassium from the extracellular into the intracellular space (by the administration of sodium bicarbonate when the pH is low and/or dextrose–insulin when effects relatively independent of serum pH are desired), using zero-balanced ultrafiltration (Z-BUF) with normal saline as the replacement fluid (to remove potassium from the body rather than simply shift the electrolyte across cellular membranes), and, occasionally, hemodialysis (1). We report the application of Z-BUF using an electrolyte-balanced, low potassium dialysate solution rather than isotonic saline to avoid a high chloride load and the potential for hyperchloremic acidosis to successfully treat hyperkalemia while on cardiopulmonary bypass

An Ultrafiltration Technique for Directly Reinfusing Residual Cardiopulmonary Bypass Blood

Given the shortages of banked blood, the risks of transfusion reactions, disease transmissions, and transfusion errors, we perfusionists must find ways to avoid blood transfusions. At the end of any given bypass run, there is residual blood left in the bypass circuit, the perfusionist must get this blood back to the patient. Most commonly either a cell saver or a hemoconcentrator (HC) has been used, in some fashion, to reinfuse residual circuit blood. The ideal method should: 1) be simple; 2) raise the hematocrit (HCT); 3) allow for changes in the patient’s volume status; and 4) not compromise the integrity of the cardiopulmonary bypass (CPB) circuit allowing for rapid re-institution of CPB. We describe a technique in which residual CPB circuit blood is pumped through an HC directly to the patient via a 3/16-inch diameter line into a 16-gauge intravenous needle positioned in a peripheral or central vein. This allows the perfusionist to give back concentrated blood that is protein-rich while maintaining the above criteria

Antithrombin: anti-inflammatory properties and clinical applications

Many humoral and cellular components participate in bidirectional communication between the coagulation and inflammation pathways. Natural anticoagulant proteins, including antithrombin (AT), tissue factor pathway inhibitor, and protein C, suppress proinflammatory mediators. Conversely, inflammation blunts anticoagulant activity and, when uncontrolled, promotes systemic inflammation-induced coagulation, such as those that occur in disseminated intravascular coagulation and severe sepsis. This review discusses the mechanisms of action and clinical use of AT concentrate in critically ill patients and in the settings of perioperative anticoagulation management for surgery and obstetrics. AT is a serine protease inhibitor with broad anticoagulant activity and potent anti-inflammatory properties. In clinical conditions associated with hereditary or acquired AT deficiency, administration of AT concentrate has been shown to restore proper haemostasis and attenuate inflammation. Of note, AT modulates inflammatory responses not only by inhibiting thrombin and other clotting factors that induce cytokine activity and leukocyte-endothelial cell interaction, but also by coagulation-independent effects, including direct interaction with cellular mediators of inflammation. An increasing body of evidence suggests that AT concentrate may be a potential therapeutic agent in certain clinical settings associated with inflammation. In addition to the well-known anticoagulation properties of AT for the treatment of hereditary AT deficiency, AT also possesses noteworthy anti-inflammatory properties that could be valuable in treating acquired AT deficiency, which often result in thrombotic states associated with an inflammatory componen

Shifting sediment sources in the world's longest river: A strontium isotope record for the Holocene Nile

We have reconstructed long-term shifts in catchment sediment sources by analysing, for the first time, the strontium (Sr) and neodymium (Nd) isotope composition of dated floodplain deposits in the Desert Nile. The sediment load of the Nile has been dominated by material from the Ethiopian Highlands for much of the Holocene, but tributary wadis and aeolian sediments in Sudan and Egypt have also made major contributions to valley floor sedimentation. The importance of these sources has shifted dramatically in response to global climate changes. During the African Humid Period, before c. 4.5 ka, when stronger boreal summer insolation produced much higher rainfall across North Africa, the Nile floodplain in northern Sudan shows a tributary wadi input of 40–50%. Thousands of tributary wadis were active at this time along the full length of the Saharan Nile in Egypt and Sudan. As the climate became drier after 4.5 ka, the valley floor shows an abrupt fall in wadi inputs and a stronger Blue Nile/Atbara contribution. In the arid New Kingdom and later periods, in palaeochannel fills on the margins of the valley floor, aeolian sediments replace wadi inputs as the most important secondary contributor to floodplain sedimentation. Our sediment source data do not show a measurable contribution from the White Nile to the floodplain deposits of northern Sudan over the last 8500 years. This can be explained by the distinctive hydrology and sediment delivery dynamics of the upper Nile basin. High strontium isotope ratios observed in delta and offshore records – that were previously ascribed to a stronger White Nile input during the African Humid Period – may have to be at least partly reassessed. Our floodplain Sr records also have major implications for bioarchaeologists who carry out Sr isotope-based investigations of ancient human remains in the Nile Valley because the isotopic signature of Nile floodplain deposits has shifted significantly over time

Ant-inspired sorting by robots: the importance of initial clustering

For engineers the prospect of scalable collective robot systems is very appealing. Such systems typically adopt a decentralized approach in their control and coordination mechanism, which employs local sensing and action as well as limited communication. Under these constraints and informed by research on Temnothorax ants, two puck sorting algorithms were tested in a combination of simulation and with real robots. Both algorithms employed puck density as a cue. Only the overall local density, irrespective of puck type, was found to be required which offers the prospect for a more simple mechanism than had been previously considered. For one algorithm, this density cue was used both for picking up and dropping items and is, therefore, referred to as the ‘double density’ algorithm (DD). In the second algorithm, density was used as a cue only for picking up. Depositing an item was governed by the distance travelled which was specific to the type of item being carried. This was referred to as the ‘single density’ algorithm (SD). Unlike the DD it was found that, for the SD, the clustering of items is a necessary pre-condition for sorting. Results from ant experiments also showed that sorting is carried out in two phases: a primary clustering episode followed by a spacing phase. This strongly suggests that clustering may also be a precondition for spacing in ants

Oxidative Stress and Cerebral Vascular Tone: The Role of Reactive Oxygen and Nitrogen Species

The brain’s unique characteristics make it exceptionally susceptible to oxidative stress, which arises from an imbalance between reactive oxygen species (ROS) production, reactive nitrogen species (RNS) production, and antioxidant defense mechanisms. This review explores the factors contributing to the brain’s vascular tone’s vulnerability in the presence of oxidative damage, which can be of clinical interest in critically ill patients or those presenting acute brain injuries. The brain’s high metabolic rate and inefficient electron transport chain in mitochondria lead to significant ROS generation. Moreover, non-replicating neuronal cells and low repair capacity increase susceptibility to oxidative insult. ROS can influence cerebral vascular tone and permeability, potentially impacting cerebral autoregulation. Different ROS species, including superoxide and hydrogen peroxide, exhibit vasodilatory or vasoconstrictive effects on cerebral blood vessels. RNS, particularly NO and peroxynitrite, also exert vasoactive effects. This review further investigates the neuroprotective effects of antioxidants, including superoxide dismutase (SOD), vitamin C, vitamin E, and the glutathione redox system. Various studies suggest that these antioxidants could be used as adjunct therapies to protect the cerebral vascular tone under conditions of high oxidative stress. Nevertheless, more extensive research is required to comprehensively grasp the relationship between oxidative stress and cerebrovascular tone, and explore the potential benefits of antioxidants as adjunctive therapies in critical illnesses and acute brain injuries

Improved early survival with a nonsternotomy approach for continuous-flow left ventricular assist device replacement

Even in the modern era of continuous-flow left ventricular assist devices (CF LVADs), device replacement may be required. Nonsternotomy (NS) approaches are being used more commonly for replacement procedures. Outcomes after this less invasive approach compared with those after a reoperative sternotomy (RS) have not been extensively studied. Furthermore, the clinical impact of concurrent cardiac procedures during device replacement has not been examined. From 2005 to 2013, all consecutive implantable LVAD procedures were reviewed, and those using CF devices as both the initial and replacement device were identified. These CF LVAD replacement procedures were divided into those using an RS and those using an NS approach. Periprocedural morbidity and mortality were compared between the groups. A total of 42 CF LVAD replacements were performed in 39 patients, with 20 using an RS approach and 22 using an NS approach. Eleven of the 20 replacement procedures performed by RS included a concurrent cardiac procedure. Relative to the RS cohort, the NS approach was associated with shorter cardiopulmonary bypass time, reduced length of mechanical ventilation, decreased transfusion requirements, less inotropic support, decreased incidence of right ventricular (RV) dysfunction, and shorter intensive care unit (ICU) and overall hospital stays. An NS approach was also associated with improved 30- and 90-day survival (100% versus 79.0% in the RS group; p = 0.048). RS replacement procedures appeared to be associated with increased morbidity, regardless of whether they included concurrent cardiac procedures. Patients who did not require an RS approach and who underwent CF LVAD replacement through an NS approach had improved survival and reduced morbidity compared with those who required an RS

Rejuvenation solution as an adjunct cold storage solution maintains physiological haemoglobin oxygen affinity during early‐storage period of red blood cells

BackgroundRed blood cell (RBC) units accumulate morphologic and metabolic lesions during storage before transfusion. Pyruvate–inosine–phosphate–adenine (PIPA) solutions (Rejuvesol, Biomet, Warsaw, IN) can be incubated with RBC units to mitigate storage lesions. This study proposes a PIPA treatment process, termed cold ‘rejuvenation’, using Rejuvesol as an adjunct additive solution, to prevent biomechanical storage lesions while avoiding the 1 h PIPA incubation required with standard PIPA treatment. We compared the efficacy of cold to standard ‘rejuvenation’ in improving metabolic lesions that occur during cold storage of RBCs, without altering function.MethodsTwelve leucoreduced, A‐positive RBC units were obtained. Each unit was aliquoted into either control (standard storage), washed (W), standard rejuvenation (SR) or cold rejuvenation (CR) groups, the latter two requiring washing. A volume‐adjusted dose of Rejuvesol was instilled into the CR group upon receipt (Day 3). After 15 days of storage, p50, RBC deformability, in‐bag haemolysis and mechanical fragility were analysed. ‘Any treatment’ is defined as W, SR and CR, with comparisons in reference to control.ResultsHigher p50s were seen in rejuvenated groups (>30 mmHg vs. <19 mmHg; P < 0·0001). Any treatment significantly increased elongation index (P = 0·034) but did not significantly increase in‐bag haemolysis (P = 0·062). Mechanical fragility was not significantly different between groups (P = 0·055) at baseline, but the control (CTL) group was more fragile after 2 h in a cardiac bypass simulation than any treatment (P < 0·0001).ConclusionsThis study demonstrates that rejuvenation (standard or cold) prevents the leftward p50 shift of storage lesions without detrimental effect on RBC deformity, in‐bag haemolysis or mechanical fragility.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/156162/2/vox12910_am.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/156162/1/vox12910.pd