Why 0.9% saline is isotonic: understanding the aqueous phase of plasma and the difference between osmolarity and osmolality

In Vitro Evaluation of Lateral Femur Condyle Free Chondral Fragment Swelling after Soaking in Normal Saline

OBJECTIVE

After traumatic knee injuries, chondral fragments can avulse off bone with the progeny fragment becoming a loose body. The loose fragment may be larger than expected when trying to surgically repair the fragment back to its original site. The purpose of this study was to determine whether a loose chondral fragment from the lateral femur condyle would increase in size and weight after soaking in normal saline (NS) for 14 days.

DESIGN

Twelve 6-mm OAT (osteoarticular transfer) plugs were harvested from 6 cadaver knees on the lateral femoral condyle to simulate a chondral fragment. The chondral fragments were then placed inside an airtight specimen container with NS (0.9% sodium chloride) and were measured over 14 days.

RESULTS

After 14 days, the chondral fragments showed no increase in diameter as they measured an average of 5.567 ± 0.448 mm on Day 1 and 5.702 ± 0.253 mm on Day 14 (P = 0.183). The chondral fragments showed an increase in mass from an average of 0.058 ± 0.012 g on Day 1 to 0.073 ± 0.012 g on Day 14 (P < 0.001) and an increase in thickness from an average of 2.038 ± 0.346 mm on Day 1 to 2.229 ± 0.297 mm on Day 14 (P = 0.033).

CONCLUSIONS

Chondral fragments in NS increase in mass and thickness over time, but do not change in diameter. When surgeons are evaluating loose chondral fragments for fixation, they should consider that these fragments may appear thicker than the recipient location.

SOI MEMS Electro-Thermal Actuators for Biomedical Applications: Operation in 0.9% NaCl Solution

In recent years, the immense potential for MEMS devices in the biomedical industry has been understood. It has been determined that, among their many plausible functions, their use may also extend to single human red blood cell diagnostics, whereby biomarkers of quantifiable magnitudes may be detected. Without a doubt, the mechanical and thermal specifications by which potential devices must be able to function are very strict. Among them is the ability to operate while fully submerged in aqueous solutions. In this work, six devices were modelled numerically in deionised (DI) water and 0.9 wt% NaCl solution, the results of which were validated experimentally. The mechanical performance of the different devices when fully submerged in 0.9 wt% NaCl solution is hereby discussed. With the exception of one, all the devices in their current configuration are confirmed to be suitable candidates for biomedical applications.

Self-Assembly Properties of an Amphiphilic Phosphate Ester Prodrug Designed for the Treatment of COVID-19

PF-07304814 is a water-soluble phosphate ester prodrug of a small molecule inhibitor for the SARS CoV-2 3CL protease designed for the treatment of COVID-19. The amphiphilicity and self-assembly behavior of the prodrug was investigated computationally and experimentally via multiple orthogonal techniques to better design formulations for intravenous infusion. The self-assembly of PF-07304814 into micellar structures enabled an increase in the solubility of lipophilic impurities by up to 1900x in clinically relevant formulations. The observed solubilization could help extend the drug product shelf-life and in use stability through inhibition of precipitation, without the need for solubilizing excipients. The work presented in this manuscript provides a roadmap for the characterization of prodrug self-assembly and highlights the potential for prodrug modifications to enhance solubility of both active ingredients and impurities and to extend drug product shelf-life.

Thermo-Mechanical Fluid-Structure Interaction Numerical Modelling and Experimental Validation of MEMS Electrothermal Actuators for Aqueous Biomedical Applications

Recent developments in MEMS technologies have made such devices attractive for use in applications that involve precision engineering and scalability. In the biomedical industry, MEMS devices have gained popularity in recent years for use as single-cell manipulation and characterisation tools. A niche application is the mechanical characterisation of single human red blood cells, which may exhibit certain pathological conditions that impart biomarkers of quantifiable magnitude that are potentially detectable via MEMS devices. Such applications come with stringent thermal and structural specifications wherein the potential device candidates must be able to function with no exceptions. This work presents a state-of-the-art numerical modelling methodology that is capable of accurately predicting MEMS device performance in various media, including aqueous ones. The method is strongly coupled in nature, whereby thermal as well as structural degrees of freedom are transferred to and from finite element and finite volume solvers at every iteration. This method therefore provides MEMS design engineers with a reliable tool that can be used in design and development stages and helps to avoid total reliability on experimental testing. The proposed numerical model is validated via a series of physical experiments. Four MEMS electrothermal actuators with cascaded V-shaped drivers are presented. With the use of the newly proposed numerical model as well as the experimental testing, the MEMS devices' suitability for biomedical applications is confirmed.

Normal saline: Past, present, and future

Normal saline (NS) is the most widely used agent in the medical field. However, from its origin to its widespread application, it remains a mystery. Moreover, there is an ongoing debate on whether its existence is reasonable, harmful to the human body, or will still exist in the future. The current review traces back to the origins of NS and provides a brief overview of the current situation of infusion. The purpose may shed some light on the possibility of the existence of NS in the future by elaborating on the origin of NS and the research status of the impact of NS on the human body.

On the dissociation pathways of copper complexes relevant as PET imaging agents

Several bifunctional chelators have been synthesized in the last years for the development of new ⁶⁴Cu-based PET agents for in vivo imaging. When designing a metal-based PET probe, it is important to achieve high stability and kinetic inertness once the radioisotope is coordinated. Different competitive assays are commonly used to evaluate the possible dissociation mechanisms that may induce Cu(II) release in the body. Among them, acid-assisted dissociation tests or transchelation challenges employing EDTA or SOD are frequently used to evaluate both solution thermodynamics and the kinetic behavior of potential metal-based systems. Despite of this, the Cu(II)/Cu(I) bioreduction pathway that could be promoted by the presence of bioreductants still remains little explored. To fill this gap we present here a detailed spectroscopic study of the kinetic behavior of different macrocyclic Cu(II) complexes. The complexes investigated include the cross-bridge cyclam derivative [Cu(CB-TE1A)]⁺, whose structure was determined using single-crystal X-ray diffraction. The acid-assisted dissociation mechanism was investigated using HClO₄ and HCl to analyse the effect of the counterion on the rate constants. The complexes were selected so that the effects of complex charge and coordination polyhedron could be assessed. Cyclic voltammetry experiments were conducted to investigate whether the reduction to Cu(I) falls within the window of common bioreducing agents. The most striking behavior concerns the [Cu(NO2Th)]²⁺ complex, a 1,4,7-triazacyclononane derivative containing two methylthiazolyl pendant arms. This complex is extremely inert with respect to dissociation following the acid-catalyzed mechanism, but dissociates rather quickly in the presence of a bioreductant like ascorbic acid.

Factors affecting the patency and complications of peripheral intravenous catheters in newborns

BACKGROUND

Peripheral intravenous catheters (PICs) are necessary for medication, nutrient, and fluid administration in pediatric patients. However, PICs are uneasy to access and maintain in young infants. This study identified risk factors affecting the complications and patency of PICs.

METHODS

This retrospective cohort study included neonates and infants aged <4 months. All PICs inserted in the neonatal intensive care unit and intermediate care nursery were analyzed more than 5 months. The variables included gestational age, age and body weight at PIC insertion, insertion site, methods to maintain PIC patency (continuous intravenous drip [CIVD] versus intermittent flushing), fluid infusion rate and osmolarity, and ampicillin and cefotaxime concentrations. The effects of these variables on PIC complications and lifespan were assessed using binary logistic regression analysis and a general linear model, respectively.

RESULTS

In total, 315 PICs were analyzed. The mean indwelling time was 33.8 ± 21.5 h and complication rate was 82.2%. The most frequent complications were infiltration (55.9%) and leakage (22.2%). The infusion rate and method to maintain PICs significantly impacted PIC patency. A negative correlation was noted between the infusion rate and PIC patency, with the patency decreasing by 0.9 h (p = 0.047) on increasing the infusion rate by 1 mL/h. Notably, compared with intermittent flushing, CIVD using a hypertonic solution significantly decreased PIC patency by 14 h (p = 0.006). As the patients' age increased by a month, the complication risk decreased by 35% (p = 0.027). However, as the infusion rate increased by 1 mL/h, the complication risk increased by 17% (p = 0.018).

CONCLUSIONS

Intermittent flushing may be preferred over CIVD to preserve PIC patency. An increased infusion rate is correlated with decreased PIC patency and increased complications. For the peripheral administration of ampicillin, we recommended preparing final concentrations below 50 mg/dL to prevent PIC complications.

A chemical perspective on the clinical use of platinum-based anticancer drugs

Platinum drugs have been a mainstay of cancer chemotherapy since the introduction of cisplatin in the 1970s. Since then, carboplatin and oxaliplatin have been approved world-wide and nedaplatin, lobaplatin, heptaplatin, dicycloplatin, and miriplatin have been approved in individual countries. The three main platinum drugs are not used in isolation but are combined in chemotherapy protocols from a range of 28 drugs that include: anthracyclines, alkylating agents, vinca alkaloids, antimetabolites, topoisomerase inhibitors, taxanes, and monoclonal antibodies. Interestingly, they are not yet used in combination with tyrosine kinase inhibitors or proteasome inhibitors. How platinum drugs are formulated for administration to patients is important to minimise aquation during storage and administration. Cisplatin is typically formulated in saline-based solutions while carboplatin and oxaliplatin are formulated in dextrose. Pharmacokinetics are an important factor in both the efficacy and safety of platinum drugs. This includes the quantity of protein-bound drug in blood serum, how fast the drugs are cleared by the body, and how fast the drugs are degraded and deactivated. Attempts to control platinum pharmacokinetics and side effects using rescue agents, macrocycles, and nanoparticles, and through the design of platinum(IV)-based drugs have not yet resulted in clinically successful outcomes. As cancer is predominantly a disease of old age, many cancer patients who are administered a platinum drug may have other medical conditions which means they may also be taking many non-cancer medicines. The co-administration of non-cancer medicines to patients can potentially affect the efficacy of platinum drugs and/or change the severity of their side effects through drug-drug interactions.

Albumin Use in Brain-injured and Neurosurgical Patients: Concepts, Indications, and Controversies

Human albumin has been used extensively for decades as a nonwhole blood plasma replacement fluid in the perioperative and critical care setting. Its potential advantages as a highly effective volume expander must be weighed, however, against its potential harm for patients in the context of various neurological states and for various neurosurgical interventions. This narrative review explores the physiological considerations of intravenous human albumin as a replacement fluid and examines the extant clinical evidence for and against its use within the various facets of modern neuroanesthesia and neurocritical care practice.

Microscale compressive behavior of hydrated lamellar bone at high strain rates

The increased risk of fracture in the elderly associated with metabolic conditions like osteoporosis poses a significant strain on health care systems worldwide. Due to bone's hierarchical nature, it is necessary to study its mechanical properties and failure mechanisms at several length scales. We conducted micropillar compression experiments on ovine cortical bone to assess the anisotropic mechanical response at the lamellar scale over a wide range of strain rates (10^-4 to 8·10² s^-1). At the microscale, lamellar bone exhibits a strain rate sensitivity similar to what is reported at the macroscale suggesting that it is an intrinsic property of the extracellular matrix. Significant shear band thickening was observed at high strain rates by HRSEM and STEM imaging. This is likely caused by the material's inability to accommodate the imposed deformation by propagation of thin kink bands and shear cracks at high strain rates, leading to shear band thickening and nucleation. The post-yield behavior is strain rate and direction dependent: hardening was observed for transverse oriented micropillars and hardening modulus increases with strain rate by a factor of almost 2, while axially oriented micropillars showed strain softening and an increase of the softening peak width and work to ultimate stress as a function of strain rate. This suggests that for compression at the micrometer scale, energy absorption in bone increases with strain rate. This study highlights the importance of investigating bone strength and post-yield behavior at lower length scales, under hydrated conditions and at clinically relevant strain rates. STATEMENT OF SIGNIFICANCE: We performed micropillar compression experiments of ovine cortical bone at two different orientations and over seven orders of magnitude of strain rate. Experiments were performed under humid condition to mimic the natural conditions of bone in a human body using a newly developed micro-indenter setup. The strain rate sensitivity was found to be of a similar magnitude to what has been reported for higher length scales, suggesting that the strain rate sensitivity is an intrinsic property of the bone extracellular matrix. In addition, localized shear deformation in thick bands was observed for the first time at high strain rates, highlighting the importance of investigating bone under conditions representative of an accident or fall at several length scales.

Prediction of tribocorrosion processes in titanium-based dental implants using acoustic emission technique: Initial outcome

The use of dental implants is growing rapidly for the last few decades and Ti-based dental implants are a commonly used prosthetic structure in dentistry. Recently, the combined effect of corrosion and wear, called tribocorrosion, is considered as a major driving process in the early failure of dental implants. However, no previous study has reported the prediction of tribocorrosion processes in advance. Therefore, this study is a novel investigation on how the acoustic emission (AE) technique can predict tribocorrosion processes in commercially-pure titanium (cpTi) and titanium-zirconium (TiZr) alloys. In this study, tribocorrosion tests were performed under potentiostatic conditions and AE detection system associated with it captures AE data. Current evolution and friction coefficient data obtained from the potentiostatic evaluations were compared with AE absolute energy showcased the same data interpretation of tribocorrosion characteristics. Other AE data such as duration, count, and amplitude, matched more closely with other potentiostatic corrosion evaluations and delivered more promising results in the detection of tribocorrosion. Hence, AE can be consider as a tool for predicting tribocorrosion in dental implants. Experimental results also reveal Ti5Zr as one of the most appropriate dental implant materials while exposing Ti10Zr's lower effectiveness to withstand in the simulated oral environment.

Effects of Volume Replacement for Urinary Losses from Mannitol Diuresis on Brain Water in Normal Rats

BACKGROUND/OBJECTIVE

It is frequently recommended that urine output following perioperative mannitol administration be replaced 1:1 with an isotonic crystalloid solution. It is possible that this strategy could increase brain water by reducing the serum osmolality achieved with prior mannitol administration. Therefore, brain water content of rats treated with mannitol alone or mannitol plus normal saline (NS) was studied over a range of urinary replacement ratios.

METHODS

Male Wister rats received mannitol 3.2 gm/100 gm infused over 45 min followed by hourly determinations of urine output (UO). Control animals received no additional therapy, whereas animals undergoing intervention received hourly replacement of their urinary losses with 0.9% NS in decreasing NS:UO ratios (1:1, 1:2, 1:3). Three hours after completion of the mannitol infusion, a final tally of UO was made. At that time in all animals, blood was obtained for determination of hemoglobin and electrolyte concentrations and plasma osmolality. Following that, the animals were sacrificed to determine brain water content. Additional groups underwent the same protocol but for 5 h with 1:1 urinary replacement, or received a volume of NS equal to that of the mannitol administered to all other control and intervention animals.

RESULTS

1:1 replacement of urinary loss with NS following mannitol administration was associated with brain water content indistinguishable from control animals receiving only a volume of NS equal to that of the mannitol administered to all other groups. Regression analysis demonstrated a decrease in the final brain water content of 0.67% (CI95 0.43-0.92, p < 0.001) per replacement level as NS:UO replacement ratios were decreased from 1:1 to 1:2 and, finally to 1:3. At the final NS:UO replacement ratio of 1:3, brain water content was indistinguishable from the control group receiving mannitol without NS replacement (p = 0.48) For 1:1 replacement following mannitol, brain water did not differ between experiments of 3 or 5 h duration (p = 0.52).

CONCLUSIONS

In rats, NS replacement of UO 1:1 following mannitol administration leads to brain water content no different than if NS had been given in place of mannitol. Only when the NS:UO replacement ratio was 1:3, brain water was similar to that of control animals receiving mannitol alone. The recommendation to replace UO 1:1 with an equal volume of isotonic crystalloid following perioperative mannitol administration must recognize how this strategy could elevate brain water content compared to less vigorous replacement of UO.

Maintenance Fluid Therapy with Saline, Dextrose-Supplemented Saline or Lactated Ringer in Childhood: Short-Term Metabolic Effects

Maintenance with isotonic fluids is recommended in children with gastroenteritis and failure of oral rehydration therapy. However, little is known on the short-term effects of the commonly prescribed intravenous solutions on metabolic balance in children. The aim of this study is to report on our experience with normal saline, dextrose-supplemented saline and lactated Ringer solution. Methods: A retrospective analysis from the charts of all previously apparently healthy children with acute gastroenteritis, mild to moderate dehydration and failure of oral rehydration, evaluated between January 2016 and December 2019 at our institution, was performed. Subjects prescribed the above-mentioned maintenance intravenous fluids and with blood testing immediately before starting fluid therapy and 4–6 h later, were eligible. The changes in bicarbonate, ionized sodium, potassium, chloride, anion gap and glucose were investigated. Kruskal–Wallis test with the post-hoc Dunn’s comparison and the Fisher exact test were applied. Results: A total of 134 out of 732 children affected by acute gastroenteritis were included (56 patients were prescribed normal saline, 48 dextrose-supplemented normal saline and 30 lactated Ringer solution). The effect of the three solutions on sodium and potassium was similar. As compared to non-supplemented normal saline (+0.4 (−1.9 – +2.2) mmol/L), dextrose-supplemented normal saline (+1.5 (+0.1 – +4.2) mmol/L) and lactated Ringer (+2.6 (+0.4 – +4.1) mmol/L) solution had a positive effect on plasma bicarbonate. Finally, the influence of dextrose-supplemented saline on blood glucose was different (+1.1 (+0.3 – +2.2) mmol/L) compared to that observed in cases hydrated with non-supplemented saline (−0.4 (−1.2 – +0.3) mmol/L) or lactated Ringer solution (−0.4 (−1.2 – +0.1) mmol/L). Conclusions: This study points out that maintenance intravenous therapies using normal saline, dextrose-supplemented saline or lactated Ringer solution have different effects on metabolic balance. A personalized fluid therapy that takes into account the clinical and biochemical variables is advised.

Hyponatremia in infants with community-acquired infections on hospital admission

Acute moderate to severe gastroenteritis is traditionally associated with hypernatremia but recent observations suggest that hypernatremia is currently less common than hyponatremia. The latter has sometimes been documented also in children with acute community-acquired diseases, such as bronchiolitis and pyelonephritis. We investigated the prevalence of dysnatremia in children with acute moderate severe gastroenteritis, bronchiolitis and pyelonephritis. This prospective observational study included 400 consecutive previously healthy infants ≥4 weeks to ≤24 months of age (232 males and 168 females): 160 with gastroenteritis and relevant dehydration, 160 with moderate-severe bronchiolitis and 80 with pyelonephritis admitted to our emergency department between 2009 and 2017. Circulating sodium was determined by means of direct potentiometry. For analysis, the Kruskal-Wallis test and the Fisher’s exact test were used. Hyponatremia was found in 214 of the 400 patients. It was common in gastroenteritis (43%) and significantly more frequent in bronchiolitis (57%) and pyelonephritis (68%). Patients with hyponatremia were significantly younger than those without hyponatremia (3.9 [1.6–13] versus 7.5 [3.4–14] months). The gender ratio was similar in children with and without hyponatremia. Hyponatremia was associated with further metabolic abnormalities (hypokalemia, hyperkalemia, metabolic acidosis or metabolic alkalosis) in gastroenteritis (71%) and pyelonephritis (54%), and always isolated in bronchiolitis. In conclusion, hyponatremia is common at presentation among previously healthy infants with gastroenteritis, bronchiolitis or pyelonephritis. These data have relevant consequences for the nutrition and rehydration management in these conditions.