Left ventricular depression and pulmonary edema in rats after short-term normobaric hypoxia: effects of adrenergic blockade and reduced fluid load

Acute normobaric hypoxia may induce pulmonary injury with edema (PE) and inflammation. Hypoxia is accompanied by sympathetic activation. As both acute hypoxia and high plasma catecholamine levels may elicit PE, we had originally expected that adrenergic blockade may attenuate the severity of hypoxic pulmonary injury. In particular, we investigated whether administration of drugs with reduced fluid load would be beneficial with respect to both cardiocirculatory and pulmonary functions in acute hypoxia. Rats were exposed to normobaric hypoxia (10% O2) over 1.5 or 6 h and received 0.9% NaCl or adrenergic blockers either as infusion (1 ml/h, increased fluid load) or injection (0.5 ml, reduced fluid load). Control animals were kept in normoxia and received infusions or injections of 0.9% NaCl. After 6 h of hypoxia, LV inotropic function was maintained with NaCl injection but decreased significantly with NaCl infusion. Adrenergic blockade induced a similar LV depression when fluid load was low, but did not further deteriorate LV depression after 6 h of infusion. Reduced fluid load also attenuated pulmonary injury after 6 h of hypoxia. This might be due to an effective fluid drainage into the pleural space. Adrenergic blockade could not prevent PE. In general, increased fluid load and impaired LV inotropic function promote the development of PE in acute hypoxia. The main physiologic conclusion from this study is that fluid reduction under hypoxic conditions has a protective effect on cardiopulmonary function. Consequently, appropriate fluid management has particular importance to subjects in hypoxic conditions.

Determining an Appropriate To-Keep-Vein-Open (TKVO) Infusion Rate for Peripheral Intravenous Catheter Usage

Highlights Abstract Background: Evidence to support an optimum continuous to-keep-vein-open (TKVO) infusion rate for peripheral intravenous catheters (PIVCs) is lacking. The aim of this study was to simulate typical TKVO rates, in combination with flushing, to better understand TKVO in relation to PIVC patency. Methods: We simulated saline infusion through a 20-gauge PIVC in 2 forearm veins (3.3 and 2.2 mm) using computational fluid dynamics under various venous flow rates (velocities 3.7–22.1 cm/s), with a saline flush rate of 1 mL/s and TKVO infusion rates of 10, 20, and 40 mL/h. We determined TKVO efficacy using the stream of saline clearing the stasis region at the device tip and the shear stress acting on the vein. Results: At 10 mL/h TKVO rate, blood stasis occurs around the PIVC tip as saline is pulled into the faster-moving venous blood flow, creating the blood recirculation (stasis) zone at the device tip. When TKVO increases >20 mL/h, this stasis diminishes, and the likelihood of patency increases. Shear stress on the vein is negligible during TKVO but increases 10- to 19-fold when flushing the small and large veins investigated here. Conclusions: Low TKVO rates (10 mL/h) may not clear the PIVC tip and keep the device patent. Based on our simulations, we propose a TKVO rate of at least 20 mL/h could be used in practice; however, 30–40 mL/h appears most effective across different venous flow rates and peripheral vein sizes. However, this additional fluid load must be carefully considered based on the needs of each patient.

Challenges of Managing and Diagnosing Reset Osmostat vs SIADH in a Patient With Personal and Family History of Chronic Hyponatremia

Background: Distinguishing between a reset osmostat and SIADH in a hyponatremic patient can prove to be challenging in certain circumstances. Reset osmostat is an uncommon and under recognized cause of hyponatremia. Thus, it is important to recognize it as it does not require any treatment. Clinical Case: A 48 year old male with history of chronic hyponatremia of unknown cause, fatty liver, hypertension, was in the hospital post operatively after resection of a meningioma along dura. Endocrine was consulted for management of his chronic hyponatremia. Had chronic hyponatremia for over 20 years and was always asymptomatic. Normally drank 6-7 L of water at home, mostly at night. Also found to have a spinal compression fracture of unknown cause. Both his father and brother had chronic hyponatremia of unknown cause as well, suggesting possible familial component. His baseline sodium levels were 129-133 mmol/L. In the hospital, serum sodium levels decreased to the 120s. TSH was 0.307mcunit/mL (0.27-4.2). Was also placed on 1.5 L fluid restriction. Urine osmolality was 900 mOsm/kg (500-800) with sodium of 123 mmol/L (136-145), consistent with SIADH. A rare inherited disorder, nephrogenic SIADH (NSIADH), was considered. However, it has an X-linked inheritance pattern. Fluid restriction was removed, then did fluid load with 2L of water and obtained urine sodium, serum sodium, urine osmolality, serum osmolality, Copeptin (pro-AVP) before fluid load and 1 hour after fluid load. Serum sodium level went from 127mmol/L before to 125 mmol/L after. Urine osmolality improved from 984 mOsm/kg prior to 575 mOsm/kg after. Urine sodium went from 183 mmol/L prior to 91 mmol/L after. Serum osmolality went from 278 mOsm/kg (270-310) to 268 mOsm/kg after. His co-peptin pro-AVP levels were 16.4 pmol/L (ref. <13.1). They are found to be low in NSIADH. It was decided that his chronic hyponatremia was likely due to reset osmostat. After discharge and follow up, his serum sodium was rechecked and was 128 mmol/L. It would have been challenging, but useful, to try a vaptan for diagnostic purposes and possibly to increase serum sodium. However, there are complications from overcorrection. Since patient had long standing asymptomatic chronic hyponatremia with family history, it was decided not to pursue aggressive measures just to “normalize” serum sodium. Otherwise, it would have been an example of treating the numbers and not the patient. Conclusions: Case demonstrates the importance of keeping the patient, their symptoms, and clinical picture in mind, and to not just follow numbers, as difficult as it may be, especially when managing conditions in which diagnosis may be uncertain or unclear. Sometimes no intervention is needed at all, however tempting it may be to do one, it is important to keep the former option in mind. An asymptomatic patient with longstanding chronic hyponatremia due to reset osmostat is an example of that.

Dynamic Simulation of a Warship Control Valve Based on a Mechanical-Electric-Fluid Cosimulation Model

Control valves have an important function in the warship power system. In engineering practice, the fluid oscillation inside the control valve causes the additional load to the valve actuator. When the additional load is added to the original load of the valve, it is possible that the required driving force (or driving moment) of the valve is greater than the maximum force (or moment) output by the actuator, which may cause the abnormal stop of the actuator. Conventionally, the interaction effect of the valve mechanical and electric components on the valve chamber’s flow field cannot be considered in computational fluid dynamics (CFD) simulations, so the oscillating fluid loads cannot be accurately obtained. In order to solve this problem, the mechanical-electric-fluid integrated valve model, using the FLUENT and AMESim cosimulation method, was developed to embody the interaction effect between the components of each part of the control valve and exhibit the fluid oscillation during the operating process of the control valve. Compared with the pure software simulations, the unsteady flow characteristics and dynamic response of the actuator were synchronously obtained in this study, which accurately captured the sudden fluid loads required for further compensation. At the same time, the differences in performance of different valve plugs were compared. The stability time of the valve plug and oscillation amplitude of the unstable fluid loads were distinct for control valves with different flow characteristics. The results can aid in understanding the instability mechanism of the fluid load in the control valve better, which provides the calculation basis for compensating the additional load on the valve plug and improve the reliability of the control valve.

Influence of Tip Clearance on the Hydrodynamic Damping Characteristics of a Hydrofoil

Tip clearance in hydraulic machines may complicate the fluid–structure interaction (FSI) effects. In this investigation, a mode-based approach (modal work) is evaluated and employed to quantitatively predict the added mass, added stiffness, and hydrodynamic damping ratio, in relation to the first-order bending mode of a vibrating hydrofoil. The investigated relative tip clearance ranges from 0.067% to 2% of the span length. The predicted vortex shedding frequency, natural frequency, and hydrodynamic damping ratio of the hydrofoil are in good agreement with the previously published experimental results, with relative deviations within 9.92%, 6.97%, and 11.23%, respectively. Simulation results show that the added mass, added stiffness, and hydrodynamic damping ratio increase inversely as the tip clearance increases. In particular, as the relative tip clearance increases from 0.067% to 2%, the added mass in still water, the added stiffness, and hydrodynamic damping ratio at a velocity of 10 m/s decrease by 18.66%, 9.36%, and 27.99%, respectively. As the tip clearance increases, the inversely increased pressure difference between the upper and lower surfaces of the vibrating hydrofoil is the main reason for the inversely increased hydrodynamic damping ratio. This is due to the energy leakages via the tip clearance region increase as the tip clearance increases, which may cause less fluid force to resist the vibration of the hydrofoil, resulting in less negative modal work done by the fluid load on the hydrofoil.

Monitoring circulating dipeptidyl peptidase 3 (DPP3) predicts improvement of organ failure and survival in sepsis: a prospective observational multinational study

Background Dipeptidyl peptidase 3 (DPP3) is a cytosolic enzyme involved in the degradation of various cardiovascular and endorphin mediators. High levels of circulating DPP3 (cDPP3) indicate a high risk of organ dysfunction and mortality in cardiogenic shock patients. Methods The aim was to assess relationships between cDPP3 during the initial intensive care unit (ICU) stay and short-term outcome in the AdrenOSS-1, a prospective observational multinational study in twenty-four ICU centers in five countries. AdrenOSS-1 included 585 patients admitted to the ICU with severe sepsis or septic shock. The primary outcome was 28-day mortality. Secondary outcomes included organ failure as defined by the Sequential Organ Failure Assessment (SOFA) score, organ support with focus on vasopressor/inotropic use and need for renal replacement therapy. cDPP3 levels were measured upon admission and 24 h later. Results Median [IQR] cDPP3 concentration upon admission was 26.5 [16.2–40.4] ng/mL. Initial SOFA score was 7 [5–10], and 28-day mortality was 22%. We found marked associations between cDPP3 upon ICU admission and 28-day mortality (unadjusted standardized HR 1.8 [CI 1.6–2.1]; adjusted HR 1.5 [CI 1.3–1.8]) and between cDPP3 levels and change in renal and liver SOFA score (p = 0.0077 and 0.0009, respectively). The higher the initial cDPP3 was, the greater the need for organ support and vasopressors upon admission; the longer the need for vasopressor(s), mechanical ventilation or RRT and the higher the need for fluid load (all p < 0.005). In patients with cDPP3 > 40.4 ng/mL upon admission, a decrease in cDPP3 below 40.4 ng/mL after 24 h was associated with an improvement of organ function at 48 h and better 28-day outcome. By contrast, persistently elevated cDPP3 at 24 h was associated with worsening organ function and high 28-day mortality. Conclusions Admission levels and rapid changes in cDPP3 predict outcome during sepsis. Trial Registration ClinicalTrials.gov, NCT02393781. Registered on March 19, 2015.

What Do We Know about Early Management of Sepsis and Septic Shock in Polish Hospitals? A Questionnaire Study

Background: Sepsis and septic shock are medical emergencies with a high risk of poor prognosis. We investigate the correspondence between Surviving Sepsis Campaign (SSC) guidelines and clinical practice in Poland, with special attention given to differences between ICU and non-ICU environments as well as regional variations within the country. Methods: A web-based questionnaire study was performed on a random sample of 60 hospitals from the three most populated regions in Poland—Masovia, Silesia, and Greater Poland. A 19-item questionnaire was built based on the most recent edition of SSC guidelines. Results: Sepsis diagnosis was primarily based on clinical evaluation (ICUs: 94%, non-ICUs: 62%; p = 0.02). There were significant differences between ICUs and non-ICUs regarding taking blood cultures for pathogen identification (2-times more frequent in ICUs) and having hospital-based operating procedures to adjust antimicrobial treatment to a clinical scenario (a difference of 17%). Modification of empiric antimicrobial treatment was required post-ICU admission in 70% of cases. ICUs differed from non-ICUs with regard to the methods of fluid responsiveness assessment and the types of catecholamines and fluids used to treat septic shock. The mean fluid load applied before the implementation of catecholamines was 25.8 ± 10.6 mL/kg. Norepinephrine was the first-line agent used to treat shock, and balanced crystalloids were preferred in both ICUs and non-ICUs. Conclusion: Compliance with SCC guidelines in Polish hospitals is insufficient, especially outside ICUs. There is a need for education among healthcare professionals to reach at least an acceptable level of knowledge and attitude in this field.

Risk factors for unplanned reintubation caused by acute airway compromise after general anesthesia: a case-control study

Background This study aimed to identify the risk factors and evaluate the prognosis of unplanned reintubation caused by acute airway compromise (AAC) after general anesthesia. Methods This case-control study included surgical patients who underwent unplanned reintubation in the operating room and postanesthesia care unit after general anesthesia between January 1, 2014, and December 31, 2018. Cases due to AAC were matched 1:4 with randomly selected controls. Results A total of 123,068 patients were included, and reintubation due to AAC was performed in 36 patients (approximate incidence 0.03%). Univariable analysis revealed that male sex, age > 65, ASA physical status 3, sepsis, heart disease history, cerebral infarction history, Cormack Lehane grade, surgery type, fresh frozen plasma infusion, increased intubation duration, white blood cell count, and creatinine clearance rate were related to AAC-caused unplanned reintubation. Multivariable analysis revealed that age > 65 (OR = 7.50, 95% CI 2.47–22.81, P < 0.001), ASA physical status 3 (OR = 6.51, 95% CI 1.18–35.92, P = 0.032), head-neck surgery (OR = 4.94, 95% CI 1.33–18.36, P = 0.017) or thoracic surgery (OR = 12.56, 95% CI 2.93–53.90, P < 0.001) and a high fluid load (OR = 3.04, 95% CI 1.16–7.99, P = 0.024) were associated with AAC-caused unplanned reintubation. AAC-caused unplanned reintubation patients had longer postoperative hospital (OR = 5.26, 95% CI 1.57–8.95, P < 0.001) and intensive care unit days (OR = 3.94, 95% CI 1.69–6.18, P < 0.001). Conclusions Age > 65, ASA physical status 3, head-neck or thoracic surgery and high fluid load were found to be associated with AAC-caused unplanned reintubation.