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PubMed1999

No beneficial effects of isocolloidoosmotic synthetic colloid addition to St. Thomas Hospital cardioplegic solution in ischemia-reperfusion injury in isolated perfused rat hearts.

1. Cardioplegic solutions provide the opportunity to operate on a nonbeating heart and to protect the heart against ischemic injury during cardiac surgery. The components of these solutions are constantly being modified in an effort to find the optimal solution. We studied the effects of colloidal volume replacers such as dextran, HES and gelatin as an isocolloidoosmotic addition to St. Thomas Hospital cardioplegic solution in ischemia-reperfusion injury of isolated rat hearts. 2. In the control group, after a stabilization period of 20 min, the hearts were arrested with St. Thomas Hospital cardioplegic solution for 3 min, then subjected to 30 min of global ischemia. Hearts then were reperfused for 10 min. In the experimental groups, the protocol was the same, but either HES 200/0.5 (50 g/L), modified fluid gelatin (30 g/l) or dextran 70 (25 g/L) were added to the St. Thomas Hospital solution. 3. All hearts were compared for their preischemic and postischemic contractility, heart rate, contractility rate product, coronary flow, lactate dehydrogenase, creatine phosphokinase enzyme leakage and wet/dry weight ratio. 4. All groups had similar contractility (for control, HES, gelatin and dextran groups the values at minute 10 of reperfusion were 59+/-9, 56+/-11%, 61+/-14%, 49+/-14% of initial values [P>0.05, respectively]) and enzyme leakage (lactate dehydrogenase 4.1+/-1.0, 8.1+/-1.5, 5.8+/-1.4, 3.7+/-1.2 [P>0.05] and for creatine phosphokinase 3.9+/-2.5, 6.4+/-3.7, 5.5+/-1.3, 5.5+/-0.8, P>0.05] IU xmin(-1) x g dry tissue(-1) in the reperfusion period, respectively) results as compared with the control group. 5. The addition of isocolloidoosmotic colloids to the cardioplegic solution did not appear to enhance the effectiveness of the crystalloid St. Thomas Hospital cardioplegic solution. If a colloid is to be chosen as a plasma replacer or an additive to priming solution in the preoperative period, or during open-heart surgery, it should be modified fluid gelatin-for no sign of cardiodepression was determined with the use of this agent.

Animals↗
PubMed2001

Stabilization of supersaturated solutions of a lipophilic drug for dermal delivery.

The stability of supersaturated solutions of a model lipophilic drug (LAP, a lavendustin derivative) in propylene glycol-water mixtures prepared using the method of mixed cosolvents was investigated. The solutions had a fixed degree of saturation (DS=4), but contained different ratios of propylene glycol-water. The absolute concentrations of LAP in these solutions varied by approximately a factor of 40, but the solutions at lower concentrations were no more stable than the more concentrated solutions. This shows that stability is primarily a question of the degree of saturation and not of the absolute drug concentration. Solutions of up to 5 degrees of saturation in 7:3 propylene glycol-water mixture were stable when stored for several hours; those at higher degrees of saturation recrystallized immediately. When the solutions were stirred, recrystallization occurred more rapidly. The influence of various polymeric additives on the stability of the supersaturated solutions showed that only sodium carboxymethyl cellulose had a stabilizing effect; however, the solution was very viscous and it is not clear whether the stabilizing effect was due to this high viscosity or to a specific interaction between drug and polymer.

Administration, Cutaneous↗
PubMed2001

Stability of stored methacholine solutions: study of hydrolysis kinetic by IP-LC.

Methacholine chloride is a powerful cholinergic bronchoconstrictor agent used during bronchial airway hyper-responsiveness diagnosis. Methacholine is susceptible to hydrolysis in aqueous solutions in acetic acid and beta-methylcholine. In the present work, kinetics of hydrolysis with different solvents (water and phosphate-buffered saline (PBS) pH 7.4) at different temperatures have been studied using a newly developed high-performance liquid chromatography. At 4 degrees C, kinetic determination of hydrolysis in methacholine chloride solutions (50 mg/ml) shows no hydrolysis in either aqueous or phosphate-buffered solutions over a 40-day period. At 30 degrees C, concentration of unbuffered methacholine chloride solutions remained unchanged, but buffered methacholine chloride solutions have degradation up to 5.5% over a 40-day period. At 40 degrees C, concentration of unbuffered methacholine chloride has degradation up to 5% and buffered methacholine chloride solutions have degradation up to 10% over a 40-day period. Methacholine chloride solutions are susceptibly to be used in hospital pharmacy at different concentrations. We have studied pH and osmolality for methacholine solutions prepared with different diluents potentially used in hospital pharmacies, i.e. deionized water, 0.9% NaCl and PBS pH 7.4. We have demonstrated that methacholine solutions prepared with deionized water at 50 mg/ml and diluted with PBS pH 7.4 from 5 to 40 mg/ml are isoosmotic and potentially available for inhalation tests to measure non-specific bronchial hyper-responsiveness.

Bronchoconstrictor Agents↗
PubMed2002

Effects of an alanyl-glutamine-based oral rehydration and nutrition therapy solution on electrolyte and water absorption in a rat model of secretory diarrhea induced by cholera toxin.

OBJECTIVES: Recurring diarrhea and persistent diarrhea are commonly associated with malnutrition and long-term functional deficits. A beneficial approach would be to develop an alanyl-glutamine (AlaGln)-based oral rehydration and nutrition therapy (ORNT). We investigated the effect of an AlaGln-ORNT solution on electrolyte and water absorption in a rat model of secretory diarrhea induced by cholera toxin. METHODS: Phenolsulfonphthalein (50 microg/mL) was used as a non-absorbable marker for calculation of net water and electrolyte transport. Solutions tested were Ringer's solution, a glutamine-based ORNT (Gln-ORNT) solution, and an AlaGln-ORNT solution. Cholera toxin (1 microg/mL) was injected into lumen of rat small intestinal segments and incubated for 18 h before the initiation of the perfusion. RESULTS: Cholera toxin induced significant secretion of electrolyte and water in the control Ringer's solution. AlaGln-ORNT and Gln-ORNT solutions reduced the sodium secretory effect of cholera toxin by 128% and 36%, respectively. The net water secretion also was reduced by 95% and 60%, respectively, with the AlaGln-ORNT and Gln-ORTN solutions. CONCLUSIONS: These results showed that AlaGln-ORNT solution can enhance water and electrolyte intestinal absorption even better than glutamine or glucose and thus provide a potential novel approach for ORNT to break the vicious cycle of diarrhea and malnutrition. Clinical trials are now needed in children and adults with diarrhea and malnutrition.

Animals↗
PubMed1999

A comparative study of Celsior and University of Wisconsin solutions based on 12-hr preservation followed by transplantation in canine models.

BACKGROUND: Celsior is a recently developed extracellular-type preservation solution that is effective in organ preservation. This experimental study was designed to compare the effects of Celsior and University of Wisconsin (UW) solutions in myocardial protection, using 12-hour preservation followed by orthotopic transplantation. METHODS: Fourteen pairs of adult mongrel dogs were divided into 2 groups. In the UW group (n = 7), UW solution at 4 degrees C was used for coronary vascular washout and storage following cardiac arrest with glucose-insulin-potassium (GIK) solution. In the Celsior group (n = 7), Celsior solution was used to produce cardiac arrest, for coronary vascular washout, and for storage. After 12-hour cold preservation, orthotopic transplantation was performed under cardiopulmonary bypass (CPB). The rate of recovery (%) of cardiac function of donor hearts was compared 1 and 2 hours after weaning from CPB, and then the transplanted hearts were harvested for histological study. RESULTS: Hemodynamic parameters including cardiac output, left ventricular pressure (LVP), and the maximum rates of positive and negative increase of LVP after transplantation were significantly (p < 0.05) higher in the Celsior group than in the UW group 2 hours after weaning from CPB. The transmission electron microscopic study found that degeneration of the mitochondria in the Celsior group was less extensive than in the UW group. CONCLUSION: Celsior solution enhanced the cardiac function of hearts preserved for 12 hours prior to transplantation compared to UW solution. Our results indicate that Celsior solution is equivalent or superior to UW solution for cardiac preservation.

Adenosine↗
PubMed2006

Unique gelation behavior of cellulose in NaOH/urea aqueous solution.

A transparent cellulose solution was prepared by mixing 7 wt % NaOH with 12 wt % urea aqueous solution which was precooled to below -10 degrees C and which was able to rapidly dissolve cellulose at ambient temperature. The rheological properties and behavior of the gel-formed cellulose solution were investigated by using dynamic viscoelastic measurement. The effects of temperature, time, cellulose molecular weight, and concentrations on both the shear storage modulus (G') and the loss modulus (G") were analyzed. The cellulose solution having a viscosity-average molecular weight (M(eta)) of 11.4 x 10(4) had its sol-gel transition temperature decreased from 60.3 to 30.5 degrees C with an increase of its concentration from 3 to 5 wt %. The gelation temperature of a 4 wt % cellulose solution dropped from 59.4 to 30.5 degrees C as the M(eta) value was increased from 4.5 x 10(4) to 11.4 x 10(4). Interestingly, at either higher temperature (above 30 degrees C), or lower temperature (below -3 degrees C), or for longer gelation time, gels could form in the cellulose solutions. However, the cellulose solution remains a liquid state for a long time at the temperature range from 0 to 5 degrees C. For the first time, we revealed an irreversible gelation in the cellulose solution system. The gel having been formed did not dissolve even when cooled to the temperature of -10 degrees C, at which it was dissolved previously. Therefore, this indicates that either heating or cooling treatment could not break such stable gels. A high apparent activation energy (E(a)) of the cellulose solution below 0 degrees C was obtained and was used to explain the gel formation under the cooling process.

Cellulose↗
PubMed2005

Monte Carlo simulations of the solution structure of simple alcohols in water-acetonitrile mixtures.

Monte Carlo simulations have been performed to explore the solution structure of ethyl, isopropyl, isobutyl, and tertiary butyl alcohols in pure water, pure acetonitrile, and different mixtures of the two solvents. The explicit solvent studies in NpT ensembles at T = 298 K illustrate that the solute "discriminates" the solvent's components and that the composition of the first solvation shell differs from that of the bulk solution. Since the polarizable continuum dielectric method (PCM) does not presently model the solvation of molecules with both polar and apolar sites in mixed protic solvents, we suggest a direction for further program development wherein a continuum dielectric method would accept more than one solvent and the solute sites would be solvated by user-defined solvent components. The prevailing solvation model will be determined upon the lowest free energy calculated for a particular solvation pattern of the solute having a specific conformational/tautomeric state. Characterization of equilibrium hydrogen-bond formation becomes a complicated problem that depends on the chemical properties of the solute and its conformation, as well as upon the varying nature of the first solvation shell. For example, while the number of hydrogen bonds to secondary and tertiary alcohol solutes are nearly constant in pure water and in water-acetonitrile mixtures with at least 50% water content, the number of hydrogen bonds to primary alcohols gradually decreases for most of their conformations when acetonitrile content is increased. Nonetheless, the calculations indicate that O-H...O(water) hydrogen bonds are still possible in a small fraction of the arrangements for the solution models with water content of 30% or less. The isopentene solute does not form any observable hydrogen bonds, despite having an electron-rich, double-bond site.

Acetonitriles↗
PubMed2005

Nanometer-scale ion aggregates in aqueous electrolyte solutions: guanidinium sulfate and guanidinium thiocyanate.

Neutron diffraction experiments and molecular dynamics simulations are used to study the structure of aqueous solutions of two electrolytes: guanidinium sulfate (a mild protein conformation stabilizer) and guanidinium thiocyanate (a powerful denaturant). The MD simulations find the unexpected result that in the Gdm2SO4 solution the ions aggregated into mesoscopic (nanometer-scale) clusters, while no such aggregation is found in the GdmSCN solution. The neutron diffraction studies, the most direct experimental probe of solution structure, provide corroborating evidence that the predicted very strong ion pairing does occur in solutions of 1.5 m Gdm2SO4 but not in 3 m solutions of GdmSCN. A mechanism is proposed as to how this mesoscopic solution structure affects solution denaturant properties and suggests an explanation for the Hofmeister ordering of these solutions in terms of this ion pairing and the ability of sulfate to reverse the denaturant power of guanidinium.

Electrolytes↗
PubMed2002

Accumulation of crystal deposits in abdominal organs following perfusion with defrosted University of Wisconsin solutions.

Previous studies reported on both visible and invisible particles in University of Wisconsin (UW) solutions. Those particles originated from components of the bags. In recent clinical observations we noticed macroscopically visible, indissoluble particles in UW bags reaching subzero temperatures during transportation of organs and preservation solutions. In an experimental model we examined whether those particles could be detected following perfusion of abdominal organs with established perfusion solutions. UW-, HTK- or physiological saline solutions reached -3 +/- 0.5 degrees C under conditions frequently applied during transportation. UW solutions demonstrated the accumulation of visible, indissoluble crystals and were subsequently used for the perfusion of abdominal organs in LEW rats. After perfusion with UW solutions stored at freezing temperatures, crystals were detected in all abdominal organs localized in and around vessels, bile ducts, glomeruli and in the interstitium of harvested livers, kidneys and pancreas. By spectroscopy, we were able to characterize crystals as adenosine. A 40-microm pore-size filter eliminated crystals from UW solutions. Crystals were absent in organs perfused with HTK- or saline solutions kept at subzero conditions. UW solutions can reach subzero temperatures under commonly used transportation conditions. Under these conditions, visible crystals accumulate and can be detected in abdominal organs of an experimental system.

Adenosine↗
PubMed2005

Mode-coupling study on the dynamics of hydrophobic hydration II: Aqueous solutions of benzene and rare gases.

The dynamic properties of both the solute and solvent of the aqueous solution of benzene, xenon and neon are calculated by the mode-coupling theory for molecular liquids based on the interaction-site model. The B-coefficients of the reorientational relaxation and the translational diffusion of the solvent are evaluated from their dependence on the concentration of the solute, and the reorientational relaxation time of water within the hydration shell is estimated based on the two-state model. The reorientational relaxation times of water in the bulk and within the hydration shell, that of solute, and the translational diffusion coefficients of solute and solvent, are calculated at 0-30 degrees C. The temperature dependence of these dynamic properties is in qualitative agreement with that of NMR experiment reported by Nakahara et al. (M. Nakahara, C. Wakai, Y. Yoshimoto and N. Matubayasi, J. Phys. Chem., 1996, 100, 1345-1349, ref. 36), although the agreement of the absolute values is not so good. The B-coefficients of the reorientational relaxation times for benzene, xenon and neon solution are correlated with the hydration number and the partial molar volume of the solute. The proportionality with the latter is better than that with the former. These results support the mechanism that the retardation of the mobility of water is caused by the cavity formation of the solute, as previously suggested by us (T. Yamaguchi, T. Matsuoka and S. Koda, J. Chem. Phys., 2004, 120, 7590-7601, ref. 34), rather than the conventional one that the rigid hydration structure formed around the hydrophobic solute reduces the mobility of water.

Benzene↗
PubMed1996

The palatability of five colonic lavage solutions.

BACKGROUND: Many patients dislike the taste and saltiness of polyethylene glycol-electrolyte colonic lavage solutions. Several commercially available lavage solutions have been introduced with reduced salt content or flavouring added in an attempt to improve palatability and to encourage patient compliance. AIM: To determine which of the commercially available lavage solutions are the most palatable. METHODS: A taste test of the five commercially available lavage solutions was performed by two groups of subjects: (a) adult patients scheduled to undergo colonoscopy (n = 50) and (b) adult family members of patients scheduled to undergo colonoscopy and hospital volunteers (n = 50). Subjects sampled all five products and were asked to grade the taste and saltiness, and to rank them in their overall order of preference. RESULTS: Similar findings were observed in the two groups of subjects. Colyte-Flavored, Cherry-NuLytely, NuLytely and GoLytely had similar median taste scores and a similar frequency of taste scores labelled as 'unacceptable' (8-11%); these four products ranked ahead of plain Colyte (which had a 25% frequency of taste scores labelled as 'unacceptable'). However, in the ranking phase of the study, about three-quarters of the subjects preferred a flavoured lavage solution to an unflavoured one. Colyte-Flavored and Cherry-NuLytely rated almost equal. Twenty-two per cent of subjects rated an unflavoured lavage solution (generally NuLytely or GoLytely) as their first choice. This included a subset of subjects who disliked the flavoured solutions and greatly preferred an unflavoured product. CONCLUSIONS: Four of the five commercially available products studied received similar taste scores. However, in the direct comparison phase of the study, a majority of subjects expressed a preference for a flavoured lavage solution. On the other hand, about one in five subjects expressed a dislike for the available flavoured solutions and preferred an unflavoured one.

Adolescent↗
PubMed2003

Composition of the additive solution affects red blood cell integrity after photodynamic treatment.

BACKGROUND AND OBJECTIVES: Photodynamic treatment is a promising technique for pathogen inactivation of red blood cell concentrates. For protocol optimization, the influence of the composition of the storage solution on the integrity of phototreated red cells was studied. MATERIALS AND METHODS: Red blood cells were resuspended in the storage solutions SAG-M or AS-3 to a haematocrit (Hct) of 30%. After addition of the photosensitizer, 1,9-dimethylmethylene blue (DMMB) (25 microm), the suspensions were illuminated with red light, and potassium leakage and delayed haemolysis were determined. In some experiments, the cells were washed after illumination and resuspended in modified storage solutions. RESULTS: Illumination of red cells in the presence of DMMB resulted in an immediate, light-dose-dependent increase in potassium leakage. The illumination conditions used induced no detectable haemolysis immediately after photodynamic treatment. Potassium leakage was higher when the illumination was performed in AS-3. In contrast, delayed haemolysis, measured after overnight storage, was considerably lower when cells were stored in AS-3. This protection was mainly a result of the presence of citrate in AS-3. In addition, other impermeant solutes protected against haemolysis. CONCLUSIONS: The additive solution strongly influences the integrity of red cells after photodynamic treatment. Whereas the solution in which the cells are illuminated has a small effect on red cell integrity, the main influence of the additive solution is during post-treatment storage. Red cell integrity is best maintained when illumination is performed in SAG-M followed by storage in AS-3. The presence of non-permeant solutes, such as citrate, in the solution used for storage, prevents haemolysis of the phototreated, cation-permeable cells by counterbalancing the osmotic activity of haemoglobin.

Blood Preservation↗
PubMedDate not supplied

Sterility of epidural solutions--recommendations for cost-effective use.

BACKGROUND AND OBJECTIVES: Specific recommendations or guidelines for duration of use or "hangtime" for epidural solutions have not been established. Presently, most hospital policies limit expiration dating of these solutions to 24 hours at room temperature. Extending expiration dating would reduce or eliminate the manipulation of the epidural system during the course of therapy. The objective of this study was to assess the bacteriologic status over time of pharmacy-prepared epidural solutions to determine if longer expiration dating could be safely instituted. METHODS: Samples from both previously administered and nonadministered bags of epidural infusate solutions were retrieved for bacteriologic testing and maintained at room temperature. These solutions were tested every 5 to 7 days beginning 24 to 48 hours after preparation. RESULTS: Samples of 54 infusion bags were tested for a median duration of 63 days. One hundred fifteen samples were tested. Only 5 samples of 4 solutions reported positive cultures; no growth was reported for multiple subsequent cultures of these solutions. CONCLUSIONS: Samples of pharmacy-prepared epidural solutions remained sterile for greater than 42 days. A change from epidural solution expiration dating of 24 hours to 48 or 72 hours would translate into a cost savings of $36,375 to $48,450 at our institution.

Analgesia, Epidural↗
PubMed2001

Comparison of two oral electrolyte solutions for the treatment of dehydrated calves with experimentally-induced diarrhoea.

We compared the ability of two oral electrolyte solutions to resuscitate calves with experimentally induced diarrhoea and dehydration. Sucrose solution, furosemide, spironolactone, and hydrochlorothiazide were administered to 18 male Holstein-Friesian calves to induce diarrhoea and dehydration. Clinical changes after 24 h included severe diarrhoea, moderate dehydration (8-10% body weight), azotemia, and clinical depression. Calves were then randomly assigned to one of three treatment groups (milk replacer, 2 L every 12 h; hyperosmotic oral electrolyte solution, 2 L every 12 h; iso-osmotic oral electrolyte solution, 1.5 L every 6 to 12 h) and followed for an additional 48 h. Compared to feeding milk replacer, the hyperosmotic solution significantly (P< 0.05) improved hydration status, increased body weight, maintained urine production, decreased the degree of clinical depression and prevented development of metabolic acidosis, although serum glucose concentration was decreased at 24 h and 48 h. The hyperosmotic solution produced a similar resuscitative response to the iso-osmotic solution, but maintained higher serum glucose concentrations and lower serum beta-OH butyrate and non-esterified fatty-acid concentrations, indicating that the hyperosmotic solution provided greater nutritional support. The hyperosmotic solution rehydrated calves faster and more effectively than feeding equivalent volumes of milk replacer and can, therefore, be recommended as part of the initial treatment of dehydrated calves with diarrhoea.

Animals↗
PubMed2001

Prime solutions for cardiopulmonary bypass in neonates: antioxidant capacity of prime based on albumin or fresh frozen plasma.

OBJECTIVE: Oxidative damage and inflammation are believed to play an important role in postoperative complications after cardiopulmonary bypass. During bypass, a prime solution with a high antioxidant capacity may reduce the oxidative damage and inflammation. We investigated total antioxidant capacity and individual scavengers during the preparation of 2 different prime solutions. METHODS: The prime solutions were prepared with either pasteurized human albumin or fresh frozen plasma. The total antioxidant capacity was measured with the total radical antioxidant parameter assay and with the ferric-reducing ability of plasma assay. The individual scavengers vitamin C, sulfhydryl groups, uric acid, and total protein were measured before, during, and after the prime preparation. Malondialdehyde was measured as a parameter for lipid peroxidation. RESULTS: Neither prime solution showed a total radical antioxidant parameter value. The ferric-reducing ability of plasma value of prime solutions was lower than that of undiluted human albumin or fresh frozen plasma. Addition of mannitol did not increase the ferric-reducing ability of plasma value. Vitamin C was only found in the fresh frozen plasma prime. Both prime solutions contained sulfhydryl groups and uric acid in low concentrations. During ultrafiltration, low-molecular-weight antioxidants were lost into the ultrafiltrate. CONCLUSIONS: We showed that prime solutions based on either albumin or fresh frozen plasma had very low antioxidant capacity and that ultrafiltration of the prime solution further lowers this capacity. A prime solution with a low antioxidant capacity may increase oxidative stress in neonates undergoing cardiopulmonary bypass.

Albumins↗
PubMed1960

True anomalous osmosis in multi-solute model membrane systems.

The transport of liquid across charged porous membranes separating two electrolytic solutions of different composition consists of both a normal and an anomalous osmotic component. Anomalous osmosis does not occur with electroneutral membranes. Thus, with membranes which can be charged and discharged reversibly, normal osmosis can be measured with the membrane in the electroneutral state, and normal together with anomalous osmosis with the membrane in a charged state, the difference between these two effects being the true anomalous osmosis. Data are presented on the osmotic effects across an oxyhemoglobin membrane in the uncharged state at pH 6.75 and in two charged states, positive at pH 4.0 and negative at pH 10.0, in multi-solute systems with 0.2 and 0.4 osmolar solutions of a variety of electrolytes and of glucose against solutions of other solutes of the same, one-half, and twice these osmolarities. In the simpler systems the magnitude of the true anomalous osmosis can be predicted semiquantitatively by reference to appropriate single-solute systems. In isoosmolar systems with two electrolytic solutions the anomalous osmotic flow rates may reach 300 microl./cm.(2) hr. and more; systems with electrolytic solutions against solutions of glucose can produce twice this rate. These fluxes are of the same order of magnitude as the liquid transport rates across such living structures as the mucosa of dog gall bladder, ileum, and urinary bladder.

Animals↗
PubMed1977

Effects of low-chloride solutions on action potentials of sheep cardiac Purkinje fibers.

The rapid repolarization during phase 1 of the action potential of sheep cardiac purkinje fibers has been attributed to a time- and voltage-dependent chloride current. In part, this conclusion was based on experiments that showed a substantial slowing of phase 1 when larger, presumably impermeant, anions were substituted for chloride in tyrode's solution. We have re- examined the electrical effects of low-chloride solutions. We recorded action potentials of sheep cardiac purkinje fibers in normal tyrode's solution and in low-chloride solutions made by substituting sodium propionate, acetylglycinate, methylsulfate, or methanesulfonate for the NaCl of Tyrode's solution. Total calcium was adjusted to keep calcium ion activity of test solutions equal to that of control solutions. Propionate gave qualitatively variable results in preliminary experiments; it was not tested further. Low-chloride solutions made with the other anions gave much more consistent results: phase 1 and the notch that often occurs between phases 1 and 2 were usually unaffected, and the action potential duration usually increased. The only apparent change in the resting potential was a transient 3-6 mV depolarization when low-chloride solution was first admitted to the chamber, and a symmetrical transient hyperpolarization when chloride was returned to normal. If a time- and voltage-dependent chloride current exists in sheep cardiac purkinje fibers, our results suggest that it plays little role in generating phase 1 of the action potential.

Action Potentials↗
PubMed1997

Stability of meropenem in intravenous solutions.

The stability of meropenem in various i.v. fluids stored in various containers for i.v. use was studied. Solutions of meropenem were prepared in a variety of i.v. diluents in polyvinyl chloride (PVC) bags, glass vials, and commercial easy-to-prepare infusion systems. Solutions for storage in PVC bags were prepared with meropenem concentrations of 1 and 20 mg/mL; in glass vials, 2.5 and 50 mg/mL; and in commercial easy-to-prepare infusion systems, 2.5 and 20 mg/mL (Baxter Minibag Plus system) and 1, 5, and 20 mg/mL (ADD-Vantage system, Abbott). The solutions were stored for up to 48 hours at 4-5 or 21-26 degrees C. Meropenem concentrations were determined by high-performance liquid chromatography. The stability of meropenem was influenced by the drug concentration; the drug was stable for a longer time in the 1-mg/mL solution than in the 20- and 50-mg/mL solutions. Stability was also influenced by storage temperature; the drug was stable for a longer time in solutions stored at 4-5 degrees C than in solutions stored at 21-26 degrees C. Meropenem was stable for the longest time in sterile water for injection and in 0.9% sodium chloride injection. The stability of meropenem in solutions in PVC bags, glass vials, Baxter Minibag Plus containers, and ADD-Vantage bags was influenced by the i.v. fluid used to reconstitute the drug, the concentration of the final solution, and the storage temperature.

Chromatography, High Pressure Liquid↗