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Different anion-exchange membranes (AEMs) based on polystyrene (PS)-carrying benzyltrimethyl ammonium cations are currently being developed for use in alkaline fuel cells and water electrolyzers. H...

Four novel poly(phenylene oxide)-based anion exchange membranes were investigated for electrochemical performance, ionic conductivity and water transport properties in an operating anion exchange membrane fuel cell (AEMFC), using Pt/C gas diffusion electrodes with Tokuyama ionomer. The poly(phenylene oxide)-membranes have a 1- or 5-carbon alkyl spacer between the backbone and a trimethylalkylammonium (TMA) or piperidinium (Pip) cationic group, and ion-exchange capacities (IECs) between 1.5 and 1.9 mequiv g−1. The polymer with a 5-carbon alkyl spacer, a TMA cationic group, and a higher IEC showed the highest ion conductivity and performance in the AEMFC. The results also show that introducing a 5-carbon alkyl spacer does not improve performance unless the IEC is increased and that exchanging the TMA with a Pip cationic group results in lower fuel cell performance despite a higher IEC. A discrepancy in ion conductivity between fuel cell and ex situ test was observed for the 5-carbon spacer polymers and is attributed to a higher sensitivity for dehydration. Similar water flux under load, from the anode to the cathode with increased water content at both electrodes, was observed for all membranes and only varied with membrane thickness. The deviation in fuel cell performance observed between the membranes could not be explained by differences in water flux or ionic conduction, suggesting that the electrode–membrane interaction plays a major role. Nevertheless, the study emphasizes that high membrane conductivity (for the λ-range in a fuel cell) and efficient water transport (obtained by lower membrane thickness) promote higher electrochemical performance.

High alkaline stability is critical for polymeric anion exchange membranes (AEMs) and ionomers for use in alkaline electrochemical energy conversion and storage devices such as fuel cells, electrolyzer cells and advanced batteries. Here, we have prepared and studied ether-free polyfluorenes tethered with N,N-dimethylpiperidinium (DMP) and 6-azonia-spiro[5.5]undecane (ASU) cations, respectively, attached through heteroatom-free alkyl spacers. By employing alkyl–alkyl Suzuki cross-coupling, these alicyclic quaternary ammonium cations are attached at the 4-position to impede ionic loss. Thus, all the β-hydrogens sensitive to elimination reactions are placed in strain-free rings able to fully relax by the spacer flexibility. Consequently, the AEM carrying DMP cations shows a very high alkaline and thermal stability, retaining more than 91% of the cations after 2400 h immersion in 2 M NaOH at 90 °C. Compared with corresponding AEM functionalized with N-alkyl-N-methylpiperidinium (AMP) cations [conventionally tethered via the 1(N)-position], the ionic loss by β-elimination is successfully reduced by up to 92%. The AEM functionalized with DMP also reaches a high hydroxide conductivity of 124 mS cm−1 at 80 °C. Consequently, tethering piperidine-based cations via the 4-position instead of the 1(N)-position results in AEMs with substantially improved thermal and alkaline stability, combined with high hydroxide conductivity.

Ion exchange membranes with high ionic contents typically suffer from excessive water uptake and dilution effects which compromise both mechanical properties and ion conductivity. In the present work we develop and compare partial quaternization, copolymerization and crosslinking as three different synthetic strategies to balance the ion exchange capacity (IEC), water uptake and hydroxide conductivity of poly(arylene piperidinium)s, which belong to a new class of alkali-stable anion-exchange membrane materials. Poly(biphenyl N-methylpiperidine) (PBPip) was first produced in a polyhydroxyalkylation reaction of biphenyl and N-methyl-4-piperidone, and then partly quaternized with controlled stoichiometric shortages of alkyl halide to regulate the IEC. In the second approach, a series of copolymers with controlled IEC were prepared by introducing precise amounts of ketone co-monomers in the polyhydroxyalkylations. In the final approach, crosslinked AEMs were fabricated in a reactive casting procedure, followed by partial quaternization. The overall results of the study reveals that the copolymerization approach gives AEMs with the most attractive set of properties. Hence, at a given IEC and moderate water uptake, the copolymer AEMs reach the highest hydroxide conductivity, up to 120 mS cm−1 at 80 °C, and retain the high alkaline stability of the original poly(arylene piperidinium) AEM. The study demonstrates the versatility and efficiency of these synthetic strategies to tailor and significantly improve the properties of functional high-performance AEMs for different electrochemical applications.

Hydroxide ion conducting poly(terphenyl alkylene)s functionalized with piperidine-based quaternary ammonium cations were synthesized via superacid-catalyzed polyhydroxyalkylations. By employing different synthetic strategies, we have systematically varied the structures of the cation and the backbone polymer to study the effects on morphology, stability and hydroxide conductivity. Two monomers were initially prepared by attaching 4-benzylpiperidine groups to trifluororacetophenone and m-terphenyl, respectively, through Suzuki coupling reactions. Polymerizations followed by quaternizations were then carried out to obtain poly(terphenyl alkylene)s with approximately the same ionic contents. These contained either m- or p-terphenyl backbone units, and were tethered with monocyclic N,N-dimethylpiperidinium (DMP) or spirocyclic 6-azonia-spiro[5,5]undecane-6-ium (ASU) cations placed on either the stiff terphenyl or the more flexible alkylene units along the backbone. Polymer chain flexibility and functionalization with DMP cations were found to promote ionic clustering and conductivity. Hence, a membrane based on a m-terphenyl backbone tethered with DMP on pendant phenyl groups achieved a hydroxide conductivity of 146 mS cm−1 at 80 °C. While the thermal stability was significantly higher for ASU-functionalized HEMs, the alkaline stability was highest for the ones carrying DMP cations, which showed less than 5% ionic loss after 720 h in 2 M NaOH at 90 °C. After 168 h at 120 °C, 1H NMR analysis suggested that the DMP cation degraded by a combination of β-Hofmann elimination and methyl substitution. Overall, the results of the study demonstrated that the structural features of the present polymers provided high alkaline stability, most probably due to aryl ether-free backbones, and that all the β-protons of the DMP and ASU cations were placed in 6-membered rings.

We report on aryl ether-free 2,7-diphenylfluorene-based copolymers tethered with quinuclidinium (Qui) cations via hexyl spacers, prepared through superacid catalyzed Friedel–Crafts polycondensation and quaternization reactions. The 2,7-diphenylfluorene monomers were synthesised by Suzuki coupling and were employed to increase polymer backbone stiffness. Corresponding copolymers and anion-exchange membranes (AEMs) tethered with piperidinium (Pip) and trimethylalkyl ammonium (TMA) cations were prepared as reference materials. At a given water content, the AEM functionalized with Qui cations was the most efficient hydroxide conductor and its OH− conductivity reached 100 mS cm−1 at 80 °C at an ion exchange capacity of 2.0 mequiv. g−1. Moreover, this membrane showed the highest thermal and alkaline stability in the series. 1H NMR analysis of AEMs stored in 2 M aq. NaOH at 90 °C over 672 h revealed the complete absence of any ring-opening β-elimination in the bicyclic cage-like Qui structure, and less than 2% β-elimination in the hexyl spacer. In contrast, the Pip cations were found to degrade via β-elimination in both the monocyclic ring structure and the hexyl spacer. Results on the Pip-modified AEM implied that a β-hydrogen in the linear alkyl spacer chain was approximately 4 times more vulnerable to elimination than a β-hydrogen in the 6-membered ring. In addition, all the cations degraded via substitution reactions to some degree, and the total loss of Qui, Pip and TMA cations over the period was estimated to be 4, 12 and 9%, respectively. The overall findings demonstrate that the combination of aryl ether-free backbone polymers and Qui cations results in durable and high-performance AEMs suitable for use in alkaline electrochemical energy conversion and storage devices.

The potential application of a 50 μm thick anion exchange membrane prepared based on poly(terphenyl piperidinium-co-trifluoroacetophenone) (PTPT) is investigated for vanadium redox flow batteries (VRFBs). The PTPT exhibits a considerably lower vanadium permeation than Nafion 212. Therefore, the self-discharge duration of the VRFB based on PTPT is much longer than the VRFB based on Nafion 212. Besides, PTPT shows oxidative stability almost as good as Nafion 212 during immersion in an ex-situ immersion test for more than 400 h. Comparing the VRFB performance when symmetric and asymmetric electrolyte volumes are used yields interesting results. The results show that asymmetric cycling is more effective and efficient for the VRFB assembled with PTPT than Nafion 212 as the capacity fade of 0.03% cycle−1, and the highest coulombic efficiency of 98.8% is attained. Furthermore, the color change of the membrane during cycling can be reversed using a straightforward post-treatment method. QC 20210326

Aromatic polymers functionalised with cycloaliphatic quaternary ammonium (QA) cations are currently emerging as base-stable anion exchange membranes (AEMs) for use in alkaline fuel cells and water electrolyzers. In the present work, we first prepared poly(biphenyl piperidine)s by superacid-mediated polycondensations, and then introduced different N-spirocyclic QA cations via cyclo-quaternisation of the piperidine rings. The resulting polymers and AEMs were free of diaryl ether linkages and benzylic C–H bonds, and showed very high thermal stability and hydroxide ion conductivity. Alkaline testing up to 120 °C implied that the alkaline stability of the spirocyclic cations was limited by distortions of the ring conformations caused by the rigid polymer backbone. As a consequence, the ring directly attached to the backbone degraded significantly faster by Hofmann β-elimination than the pendant ring in the spirocyclic cations. These results provide valuable insights towards the molecular design of highly thermochemically stable AEMs functionalised with N-spirocyclic QA cations.

The alkaline stability of organic cations tethered to anion-exchange membranes (AEMs) is essential for the long-term performance of alkaline membrane fuel cells and electrolyzers. Here, we have prepared and studied the thermal and alkaline stability of a series of polyelectrolytes functionalized with N-spirocyclic quaternary ammonium (QA) cations. N,N-Diallylazacycloalkane quaternary salts were readily synthesized by diallylation of pyrrolidine, piperidine, azepane, and morpholine. These monomers were employed in radical-initiated cyclo-polymerizations to obtain the target poly(N,N-diallylazacycloalkane)s. 1H NMR spectroscopy revealed that the stability of the polyelectrolytes in 2 M KOD/D2O solutions critically depended on the ring size and the absence of additional heteroatoms in the ring. Thus, poly(N,N-diallylpiperidinium) showed the highest alkaline stability, with only minor signs of degradation at 120 °C after 14 days, while the polyelectrolytes based on the morpholine and azepane rings clearly deg...

The development of cationic polymers for anion-exchange membranes (AEMs) with high alkaline stability and conductivity is a considerable challenge in materials chemistry. In response, we here present the synthesis and properties of N-spirocyclic quaternary ammonium ionenes (spiro-ionenes) containing 5- and 6-membered rings fused by central nitrogen cations. High-molecular weight and film-forming spiro-ionenes are successfully synthesized in cyclo-polycondensations of tetrakis(bromomethyl)benzene and dipiperidines under mild conditions. These polyelectrolytes show excellent thermal and alkaline stability with no degradation detected by NMR spectroscopy after more than 1800 h in 1 M KOD/D2O at 80 °C. Even at 120 °C, the spiro-ionenes display reasonable alkaline stability. Transparent and mechanically robust AEMs based on ionically cross-linked blends of spiro-ionene and polybenzimidazole reach OH– conductivities up to 0.12 S cm–1 at 90 °C. The current findings demonstrate that spiro-ionenes constitute a new...

A series of poly(arylene piperidinium)s (PAPipQs) devoid of any alkali-sensitive aryl ether bonds or benzylic sites are prepared and studied as anion exchange membranes (AEMs) for alkaline fuel cells. First, the excellent alkaline stability of the model compound 4,4-diarylpiperidinium is confirmed. Medium molecular weight poly(arylene piperidine)s are then synthesized in polycondensations of N-methyl-4-piperidone and either bi- or terphenyl via superelectrophilic activation in triflic acid. Film-forming PAPipQs are subsequently prepared in Menshutkin reactions with methyl, butyl, hexyl, and octyl halides, respectively. AEMs based on poly(terphenyl dimethylpiperidinium) show the best performance with no structural degradation detectable by 1H NMR spectroscopy after storage in 2 maq. NaOH at 60 °C after 15 d, and a mere 5% ionic loss at 90 °C. In the fully hydrated state these AEMs reach an OH− conductivity of 89 mS cm−1 at 80 °C. The presence of longer pendant N-alkyl chains (butyl to octyl) is found to significantly promote Hofmann ring-opening elimination reactions and the degradation rate increases with increasing alkyl chain length. The results of the present study demonstrate that PAPipQs are efficiently prepared from readily available monomers and show excellent alkaline stability and OH− conductivity when devoid of pendant N-alkyl chains. (Less)

High-dose intravenous infusion of 5% glucose promotes rebound hypoglycaemia and hypovolaemia in healthy volunteers. To study whether such effects occur in response to glucose/insulin, 12 healthy firemen (mean age, 39 years) received three infusions over 1–2 h that contained 20 ml of 2.5% glucose/kg of body weight, 5 ml of 10% glucose/kg of body weight with 0.05 unit of rapid-acting insulin/kg of body weight, and 4 ml of 50% glucose/kg of body weight with 1 unit of insulin/kg of body weight. The plasma glucose concentration and plasma dilution were compared at 5–10 min intervals over 4 h. Regardless of the amount of administered fluid and whether insulin was given, the plasma glucose concentration decreased to hypoglycaemic levels within 30 min of the infusion ending. The plasma dilution closely mirrored plasma glucose and became negative by approx. 5%, which indicates a reduction in the plasma volume. These alterations were only partially restored during the follow-up period. A linear relationship between plasma glucose and plasma dilution was most apparent when the infused glucose had been dissolved in only a small amount of fluid. For the strongest glucose/insulin solution, this linear relationship had a correlation coefficient of 0.77 (n=386, P

Objective . Hypoglycaemia is regularly accompanied by hypovolaemia. To suggest a mechanism for this phenomenon, we reviewed data from eight studies conducted by our group and examined the circumstances under which rebound hypoglycaemia develops after intravenous infusion of glucose solutions. Material and methods. Forty healthy volunteers and 40 patients received a total of 122 infusions of glucose solutions at different rates, volumes and concentrations. Plasma glucose and the haemodilution were measured repeatedly during and for at least 2 h after the infusions ended. Glucose kinetics was calculated using a one-compartment turnover model and the plasma volume expansion was estimated from changes in Hb. Results . A strong linear correlation was found between the glucose level and the plasma volume expansion in all series of experiments (p

Background: In previous work, extravascular expansion was observed to be enhanced by isoflurane anesthesia in sheep when a crystalloid bolus was administered. The aim of the current study was to further elaborate these investigations to humans and to explore the use of population kinetics in the analysis of fluid shifts. Methods: Eleven healthy volunteers participated in two experiments each, either awake or isoflurane anesthetized, during which they received 25 ml/kg saline, 0.9%, intravenously over 20 min. Plasma dilution data were derived from repeated sampling of hemoglobin concentration, and population pharmacokinetic analysis was conducted using the WinNonMix 2.0.1 software (Pharsight Corporation, Mountain View, CA). Plasma hormones were measured, and hemodynamic values were monitored. Results: Fluid infusion during isoflurane anesthesia was followed by a higher cardiac output, lower arterial pressure, and lower urinary excretion as compared with the awake protocol (P < 0.05). Albumin dilution was greater than hemoglobin concentration‐derived plasma dilution, which indicates a transcapillary leak of albumin. A two-compartment model with an isoflurane-depressed, intercompartmental distribution parameter predicted that more than 50% of the infused volume was retained in the peripheral compartment at 180 min in both protocols. Isoflurane markedly increased the plasma levels of renin and aldosterone, whereas vasopressin was mostly unchanged. Conclusion: Fluid retention after rapid infusion of 0.9% saline was prominent in both awake and isoflurane-anesthetized subjects. Altered kinetics of infused 0.9% saline during isoflurane anesthesia was expressed as reduced clearance and a slower distribution, resulting in a small but significant increase in fluid accumulation in the body fluid compartments. These changes may be due to the associated decreasing of mean arterial pressure and increased release of renin and aldosterone. INTRAVENOUS administration of fluid is important during anesthesia and surgery. However, inability to correctly predict fluid shifts between tissues impedes precise matching of the rate of infusion with ongoing losses and volume demands. Volume kinetics has previously been applied to data from awake 1 and anesthetized 2 humans to study fluid shifts between different body fluid compartments. The current view is that fluid retention and postoperative tissue edema after surgery are promoted by trauma-induced stress 3,4 and by mechanical ventilation 5 rather than by the administration of an anesthetic per se. However, a study in sheep 6 demonstrated that the combination of isoflurane anesthesia and mechanical ventilation significantly alters the disposition of crystalloid fluid in comparison with conscious, spontaneously ventilating sheep. In a follow-up study in sheep, isoflurane was singled out as the cause for reduced urinary excretion and peripheral fluid accumulation. 7 The first aim of the current study was to investigate the hypothesis that isoflurane anesthesia promotes peripheral fluid retention and reduces urinary excretion in humans. To further develop kinetic modeling, a second aim was to apply population kinetic analysis to the plasma dilution data. With the development of a population kinetic model, it could be possible to attribute differences in fluid distribution to such parameters as body weight, age, and sex.

Glycine 1.5% is the most widely used irrigating fluid during endoscopic procedures. To investigate if glycine toxicity is a mechanism promoting a fatal outcome when the solution is absorbed, we administered glycine 200 or 300 ml kg-1 dissolved in sterile water or normal saline, and also normal saline alone, over 60 min by i.v. infusion to 100 mice under methoxyflurane anaesthesia. Survival rates were 29% after 1.5% glycine, 21% after 1.5% glycine in normal saline, 67% after normal saline and 100% in controls. Both solutions containing glycine induced bradycardia and prolongation of the PQ interval and QRS duration, while only 1.5% glycine increased the water content of the myocardium. These results suggest that glycine promotes bradycardia and death, regardless of whether hyponatraemia or hypo-osmolality is present. We conclude that glycine toxicity is an important factor that increases the risk of administration of an irrigating fluid.

Ethanol monitoring is a fairly new method of assessing fluid absorption during transurethral resection of the prostate (TURP). By using an irrigating fluid containing a trace amount of ethanol, the absorption can be measured by expired-breath tests. We describe a TURP in which large-scale absorption of irrigating fluid occurred despite the use of a pressure-warning device set at 10 cm H2O. The surgeon decided to terminate the operation because 1.0 liters of fluid had been absorbed over 10 minutes, and another 1.0 liter was absorbed during the 10 minutes required to conclude the surgery. The high absorption rate suggests that continued resection would have promoted a severe transurethral resection syndrome. This was prevented by the indication given by the breath test, whereas the pressure-warning device failed to do so.

Objective Absorption of irrigating fluid may occur through severed blood vessels during endometrial resection. We studied whether irrigating fluid can also be absorbed through the undamaged uterus. Participants We studied 25 women, aged 28-46 years (mean 38 years), who underwent elective laparoscopic sterilisation under general anaesthesia. Interventions In 15 women blue-stained irrigating fluid containing glycine 1.5 % and ethanol I % was applied to the uterine cavity under increasing pressure. Laparoscopy was employed to see when fluid emerged from the Fallopian tubes. Another 10 women had their Fallopian tubes clamped before the fluid pressure was raised, and systemic absorption was detected by measuring the serum glycine concentration. Results Passage of fluid through the Fallopian tubes occurred in 14 of the 15 patients at a utero-abdominal pressure gradient of 40 mmHg (n = 4), 80 mmHg (n = 4), 120 mmHg (n = 3), and 160 mmHg (n = 3), respectively. The fluid passage rate ranged between 0.5 and 13 (mean 6.4) ml min -1 . Of the women with clamped Fallopian tubes, 8 of 10 showed an increase in the serum glycine level of 60 % at a pressure gradient of 160 mmHg, and of 120 % at 200 mmHg. Conclusions Uterotubal and transendometrial passage of small to moderate amounts of irrigating solution occurred frequently at the intrauterine fluid pressures normally used during endometrial resection.

We evaluated signs and symptoms of the transurethral resection syndrome recorded during and after 273 transurethral prostatic resections performed at 2 hospitals between 1984 and 1993. Glycine solution was used as the irrigant and ethanol served as a tracer for fluid absorption. The incidence and severity of symptoms that could possibly be related to the syndrome increased progressively as more glycine solution was absorbed. Patients who absorbed 0 to 300 ml. of glycine solution had an average of 1.3 such symptoms. This number increased to 2.3 when 1,001 to 2,000 ml. were absorbed, 3.1 when 2,001 to 3,000 ml. were absorbed and 5.8 for volumes greater than 3,000 ml. Nausea and vomiting occurred significantly more often when 1,001 to 2,000 ml. were absorbed compared to no absorption. Confusion and arterial hypotension were other prominent signs of fluid absorption, whereas hypertension was not. The severity of symptoms was markedly aggravated when more than 3,000 ml. were absorbed. Extravasation res...

Background. We evaluated the precision in using ethanol to indicate and quantify absorption of irrigating fluid during transcervical resection of the endometrium. Methods. The ethanol concentration in the expired breath, the serum sodium level, the blood loss and the volumetric fluid balance were measured over 10-min periods during 62 operations. A solution containing glycine 1.5% and ethanol 1% was used to irrigate the uterus. Results. Most principles previously outlined for ethanol monitoring in transurethral prostatic surgery could also be applied in endometrial resection. In the 21 patients who showed the intravascular pattern of ethanol changes, the breath alcohol measurement corrected for absorption time predicted the volume of irrigant absorbed {up to 2,531 ml) with a standard error of 230 ml at the end of any 10-min period of absorption. Repeated measurement of serum sodium indicated intravascular fluid absorption with practically the same precision as the breath test. Extravascular absorption was found in 14 patients. In these operations, the volume of irrigant absorbed (up to 1,767 ml) could be predicted with a standard error of 92 ml from the ethanol concentration at the plateau level attained after absorption had occurred. Conclusion. Ethanol monitoring is precise enough to allow monitoring of irrigating fluid absorption in endometrial resection.

Intraperitoneal absorption of electrolyte-free irrigating fluid may occur secondary to uterine perforation during endometrial resection, but the clinical course of this complication is known from only a few case reports.We studied symptoms, biochemical changes and the kinetics of solute equilibration over the peritoneal membrane in 10 healthy awake women who were subjected to an experimental absorption situation by receiving an intraperitoneal infusion of 25 ml/kg of a solution containing glycine 1.5% and ethanol 1% over 20 min. We also compared the use of breath ethanol and serum sodium samples to indicate the presence of irrigating fluid in the peritoneal cavity.All infusions caused lower abdominal pain. The solute gradients between the peritoneal pool and plasma were reduced according to mono-exponential functions with a half-time of 33 +/- 5 min for ethanol, 92 +/- 9 min for sodium, 103 +/- 9 min for potassium, and 124 +/- 10 min for amino acids (mean +/- s.e.mean). Twenty minutes after infusion, the breath ethanol level reached a plateau which could be used to predict the infused volume within +/- 15% of the true value. In contrast, the serum sodium concentration decreased slowly and was only 3.0 +/- 0.7 mmol/l below baseline at 2 hours after infusion.The calculated rates of transperitoneal solute equilibration can be used to assess the need for substitution of electrolytes in patients who absorb irrigating fluid into the peritoneal cavity. Measurement of ethanol in the expired breath is more useful than serum sodium to indicate the existence of such a pool.

BACKGROUND: Conventional concept suggests that infused crystalloid fluid is first distributed in the plasma volume and then, since the capillary permeability for fluid is very high, almost instantly equilibrates with the extracellular fluid space. We challenge whether this view is consistent with findings based on volume kinetic analysis. METHODS: Fifteen volunteers received an IV infusion of 15 mL/kg of lactated Ringer’s solution during 10 min. Simultaneous arterial and venous blood hemoglobin (Hgb) samples were obtained and Hgb concentrations measured. The arteriovenous (AV) difference in Hgb dilution in the forearm was determined and a volume kinetic model was fitted to the series of Hgb concentrations in arterial and venous blood. RESULTS: The AV difference in plasma dilution was only positive during the infusion and for 2.5 min thereafter, which represents the period of net flow of fluid from plasma to tissue. Kinetic analysis showed that volume expansion of the peripheral fluid space began to decrease 14 min (arterial blood) and 20 min (venous blood) after the infusion ended. Distribution of lactated Ringer’s solution apparently occurs much faster in the forearm than in the body as a whole. Therefore, the AV difference in the arm does not accurately reflect the distribution of Ringer’s solutions or whole-body changes in plasma volume. CONCLUSIONS: The relatively slow whole-body distribution of lactated Ringer’s solution, which boosts the plasma volume expansion during and for up to 30 min after an infusion, is probably governed by a joint effect of capillary permeability and differences in tissue perfusion between body regions. (Anesth Analg 2009;108:128‐33) Crystalloid fluids, such as lactated Ringer’s solution, are commonly used during anesthesia and surgery. When infused into the circulation hemodilution occurs which correlates with the increase in plasma volume (PV). Therefore, hemoglobin (Hgb) changes have been used to indicate the PV or blood volume (BV) over time, 1‐4 although the large-vessel: wholebody hematocrit (Hct) ratio of 0.9 should be applied to correct for anticipated unequal distribution of the Hgb molecules. 4‐7 Since fluid can be assumed to distribute

We studied whether central hemodynamics measured by a pulmonary artery catheter can serve as a pharmacodynamic expression of fluid therapy in 10 patients undergoing open abdominal surgery. We examined how closely hemodynamic variables follow plasma dilution, which is an index of plasma volume expansion, during and after an IV infusion of 25 mL/kg of lactated Ringer's solution over 45 min. Pulmonary artery wedge pressure and central venous pressure responded to IV fluid with an increase that correlated with accompanying plasma dilution. Six of 10 patients showed a decrease in cardiac output that was probably secondary to an increase in peripheral vascular resistance (nonresponders), whereas the rest increased cardiac output (responders). Volume kinetic analysis suggested that 54% of the infused fluid resided in the central fluid space at the end of the infusion and 25% at the end of the study in the responders compared with 25% and 3%, respectively, in nonresponders. In conclusion, half of the patients undergoing open abdominal surgery responded to crystalloid fluid with a decrease in cardiac output. Pulmonary artery wedge pressure and central venous pressure responded more consistently to different degrees of plasma dilution, which can be simulated for various fluid regimens using volume kinetics.

Clinicians generally consider sepsis to be a state in which fluid is poorly retained within the vasculature and accumulates within the interstitium. We hypothesized that infusion of 0.9% saline in conscious, chronically instrumented sheep with hyperdynamic bacteremic sepsis would be associated with less plasma volume expansion (PVE) and greater interstitial fluid volume expansion than in conscious, nonseptic sheep. Six conscious adult sheep received an IV infusion of 25 mL/kg of 0.9% saline over 20 min (1.25 mL.kg(-1).min(-1)) in a control nonseptic state and during early and late sepsis (4 and 24 h, respectively, after initiation of a standard infusion of live Pseudomonas aeruginosa). The distribution and elimination of infused fluid were studied by mass balance (after measurement of plasma volume using Evans blue dye) and volume kinetic analysis. Mass balance demonstrated no significant differences in the time-course of PVE between control, early sepsis, and late sepsis. At the end of the infusions, which averaged 1050 +/- 125 mL in sheep weighing an average of 42 +/- 5 kg, calculated PVE was 312 +/- 50 mL, 386 +/- 34 mL, and 400 +/- 51, respectively. Volume kinetic analysis was similar in all three protocols. In both nonseptic and septic sheep, infusion of 0.9% saline resulted in similar peak PVE and resolution of PVE over a 3-h interval and similar kinetic parameters. Contrary to clinical impressions and to our hypothesis, the distribution of 0.9% saline in this animal model was not changed by bacteremia produced by infusion of Pseudomonas aeruginosa.

The optoacoustic technique is noninvasive, has high spatial resolution, and potentially can be used to measure the total hemoglobin concentration ([THb]) continuously and accurately. We performed in vitro measurements in blood and in vivo tests in healthy volunteers. Our clinical protocol included rapid infusion of intravenous saline to simulate rapid change in the [THb] during fluid therapy or surgery. Optoacoustic measurements were made from the wrist area overlying the radial artery for more than 1?h. The amplitude of the optoacoustic signal generated in the radial artery closely followed the [THb] measured directly in concurrently collected blood samples.

We used an optoacoustic technique to measure continuously and noninvasively total hemoglobin concentration in human blood in vivo. An optoacoustic probe, which combined illuminating fibers and a piezoelectric sensitive element, was placed in contact with the skin over the radial artery. Measurements in healthy volunteers agreed well with actual hemoglobin concentration.

We report a patient who developed symptoms of fluid overload after having absorbed 3 litres of irrigating fluid during transcervical resection of the endometrium. Four methods were used to measure the absorption at 10-min intervals throughout the operation. There were strong intercorrelations between the results of these monitoring methods, which consisted in breath ethanol analyses and measurements of the serum sodium and glycine concentrations and of the volumetric fluid balance. However, the ethanol method was easiest to perform and provided immediate results. This monitoring gave the operating team as much as 45 min to prevent further absorption before it became large enough to elicit a transcervical endometrial resection syndrome.

Biochemical markers for the circadian rhythm were studied in patients treated at the ICU (intensive care unit) of two regional hospitals. A normal rhythm is characterized by a relatively higher melatonin and a lower cortisol excretion at night. Disturbances affect sleep, mood and cognitive performance. All urine excreted between 07:00 and 22:00 hours (day) and between 22:00 and 07:00 hours (night) was collected and sampled throughout the entire ICU period (median, 10 days) in 16 patients for the excretion of 6-SMT (6-sulphatoxymelatonin), which is a metabolite of melatonin, and free cortisol. The overall excretion of 6-SMT was slightly lower and the cortisol excretion higher than reported for healthy reference populations. Mechanical ventilation was associated with a markedly lower 6-SMT excretion (median, 198 ng/h) compared with periods without such help (555 ng/h; P

We performed in vitro and in vivo tests of optoacoustic monitoring of total hemoglobin concentration. The results of the in vitro measurements in blood and pilot in vivo studies in volunteers suggest that the optoacoustic technique may be used for noninvasive and continuous monitoring of total hemoglobin concentration.

Hypoxic lesions in the subendocardium and long-standing dilatation of the interstitium have been described after exposure of the heart to glycine 1.5%, which is a widely used irrigating medium in endoscopic surgery. To study if the hypo-osmotic properties of the fluid cause these morphological changes, whether their long duration can be explained by rupture of the histoskeleton and whether they promote sudden death, 75 mice received an intravenous infusion of 200 ml/kg or 300 ml/kg over 60 min of either glycine 1.5%, glycine 1.5% in normal saline, normal saline, or no fluid (controls). The animals were decapitated when they were dying from the infusion, or else 7 days later, and 69 hearts were examined by light microscopy and 4 by electron microscopy. Rupture of the histoskeleton and hypoxic lesions in the subendocardium were observed in 47% and 35%, repectively, of the mice given glycine 1.5%, while the incidence averaged 20% in the two other groups. Rupture occurred in 38% of the mice that died, in 23% of those that survived an infusion, and in 0% of the controls. Hypoxic changes correlated with bradycardia, which is a sign of glycine absorption in the clinic. In conclusion, rupture of the histoskeleton and hypoxic changes occur in the subendocardium of mice after volume loading. These morphological changes were aggravated by the hypo-osmotic properties of glycine 1.5%.

To investigate if fluid therapy changes the prerequisites for the development of oedema, four i.v. infusions of Ringer's solution 25 ml kg-1 were given over 15 or 30 min in a randomized crossover study to 10 healthy male volunteers, aged 28-40 (mean 31) yr. Blood haemoglobin concentration, measured every 5 min for 90 min, and urinary excretion were used as input data for volume kinetic analysis. The results showed that the elimination rate constant (kr) was higher when another infusion had been given earlier on the same day (208 vs 140 ml min-1; P0.002) and the size of V1 was larger during the 15-min infusions (4.7 vs 3.2 litre; P0.02). However, the size of V2 and the rate constant for the exchange of fluid between V1 and V2 were similar during all infusions. We conclude that a fluid challenge makes elimination of further infused fluid more effective but does not change compliance with volume expansion in healthy volunteers.

We used an animal model to study whether glycine prompts death after absorption of irrigating fluid by the extravascular route. Mice were divided into groups of 10 and given an intraperitoneal infusion of 200, 225, 250, 275 or 300 ml/kg of glycine 1.1%, 1.5% or 2.2%. With all infused volumes, the chance of survival was better after infusion of glycine 1.1% and glycine 1.5% than after glycine 2.2%. The overall death rates were 10%, 16% and 46%, respectively. Logistic regression analysis showed that the outcome was significantly and independently affected by both the glycine concentration and the infused volume. We conclude that the glycine concentration of an irrigating fluid deposited in the peritoneal cavity is important to the chance of survival. The poorest chance is obtained with glycine 2.2%.

Monitoring of ethanol concentration in expired air is a method for assessing fluid absorption during transurethral prostatic surgery and endometrial resection, but the validity of this technique has not been studied in low-flow ventilation systems. For this purpose, we have compared the concentration-time profiles of ethanol in expired gas and in venous blood during an i.v. infusion of 0.4 g kg-1 of ethanol over 30 min in 10 women during isoflurane anaesthesia and in the awake state. Anaesthesia increased the ethanol concentration in expired gas by 13% and in venous blood by 34%. The expired gas-blood difference during infusion was abolished, and the central volume of distribution for ethanol was reduced from 20.9 to 8.6 litre, on average. We conclude that breath sampling during low-flow isoflurane anaesthesia reflects an alcohol load well, but that a change in ethanol disposition makes the values slightly higher than in the awake state.