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PubMed2003

Prevalence and predictive value of ionized hypocalcemia among critically ill patients.

BACKGROUND: Ionized hypocalcemia is common among critically ill patients, and it has been shown to correlate with increased mortality. The purpose of this study was to examine the performance and independence of ionized calcium (Ca2+) in prediction of all-cause day-30 mortality among critically ill adult patients. METHODS: Of 993 critically ill patients treated in the Helsinki University Hospital during a 24-month period, the study comprised 941 patients without calcium supplementation. Patient and laboratory data were obtained retrospectively from an intensive care database. The discriminative powers of admission and lowest Ca2+ values regarding day-30 mortality were evaluated by producing receiver operating curves (ROC). Hazard ratios for death of severe and mild hypocalcemia were calculated by Cox regression model. RESULTS: The prevalence of ionized hypocalcemia (Ca2+ <1.16 mmol l-1) was 85%. Of 941 patients, 45 (4.7%) had ionized calcium >1.3 mmol l-1 and were excluded from mortality analysis. Univariate Cox regression model revealed hazard ratios of 5.1 (95% confidence interval, CI 2.9-9.0) for severe (<0.90 mmol l-1) and 1.8 (95% CI 1.3-2.4) for mild ionized hypocalcemia (0.90-1.15 mmol l-1) on admission, but hypocalcemia was not shown to be independently associated with mortality by multivariate Cox regression model. In prediction of day-30 mortality admission and lowest Ca2+, levels had areas under curves of 0.636 and 0.671, respectively. CONCLUSION: Ionized hypocalcemia is common among critically ill adults and it is associated with increased mortality. Although non-survivors and survivors differ significantly in admission Ca2+, hypocalcemia is not independently associated with day-30 mortality.

Adult↗
PubMed1999

Alterations in ionized and total blood magnesium after experimental traumatic brain injury: relationship to neurobehavioral outcome and neuroprotective efficacy of magnesium chloride.

Experimental evidence suggests that magnesium plays a role in the pathophysiological sequelae of brain injury. The present study examined the variation of blood ionized and total magnesium, as well as potassium, sodium, and ionized calcium, after experimental fluid percussion brain injury in rats. Blood ionized magnesium concentration significantly declined from 0.45 +/- 0.02 to 0.32 +/- 0.02 mM by 30 min postinjury and stayed depressed for the 24-h study period in vehicle-treated rats. Blood total magnesium concentration was 0.59 +/- 0.01 mM and remained stable over time in brain-injured vehicle-treated animals. When magnesium chloride (125 micromol/rat) was administered 1 h postinjury, ionized magnesium levels were restored by 2 h postinjury and remained at normal values up to 24 h following brain trauma. Magnesium treatment also significantly reduced posttraumatic neuromotor impairments 1 and 2 weeks after the insult, but failed to attenuate spatial learning deficits. A significant positive and linear correlation could be established between ionized magnesium levels measured 24 h postinjury and neuromotor outcome at 1 and 2 weeks. We conclude that acute ionized magnesium measurement may be a predictor of long-term neurobehavioral outcome following head injury and that delayed administration of magnesium chloride can restore blood magnesium concentration and attenuate neurological motor deficits in brain-injured rats.

Animals↗
PubMed2004

On the zirconium oxide neutral cluster distribution in the gas phase: detection through 118 nm single photon, and 193 and 355 nm multiphoton, ionization.

Zirconium oxide clusters are generated in the gas phase by laser ablation of the metal into a flow of ca. 5% O2/95% He at 100 psig and supersonic expansion into a vacuum chamber. Mass spectra of neutral gas phase zirconium oxide clusters are obtained through photoionization at three different laser wavelengths: 118, 193, and 355 nm. Ionization of the clusters with 118 nm laser radiation is through a single photon ionization mechanism, while ionization by 193 and 355 nm laser radiation is through a multiphoton (three or more photon) mechanism. Fragment ion features are observed in the mass spectra of ZrmOn+ for only the 193 nm and 355 nm ionization schemes. The true neutral ZrmOn cluster distribution is obtained only through 118 nm single photon ionization, as verified by mass spectral peak linewidths and calculations of the cluster binding energies, ionization energies, and fragmentation rates. The neutral cluster distribution consists mainly of the series ZrmO2m and ZrmO(2m+1) for m = 1,..., approximately 30.

Journal Article↗
PubMed2004

On the iron oxide neutral cluster distribution in the gas phase. II. Detection through 118 nm single photon ionization.

Neutral clusters of iron oxide are created by laser ablation of iron metal and subsequent reaction of the gas phase metal atoms, ions, clusters, etc., with an O2/He mixture. The FemOn clusters are cooled in a supersonic expansion and detected and identified in a time-of-flight mass spectrometer following laser ionization at 118 nm (10.5 eV), 193 nm (6.4 eV), or 355 nm (3.53 eV) photons. With 118 nm radiation, the neutral clusters do not fragment because single photon absorption is sufficient to ionize all the clusters and the energy/pulse is approximately 1 microJ. Comparison of the mass spectra obtained at 118 nm ionization (single photon) with those obtained at 193 nm and 355 nm ionization (through multiphoton processes), with regard to intensities and linewidths, leads to an understanding of the multiphoton neutral cluster fragmentation pathways. The multiphoton fragmentation mechanism for neutral iron oxide clusters during the ionization process that seems most consistent with all the data is the loss of one or two oxygen atoms. In all instances of ionization by laser photons, the most intense features are of the forms FemOm+, FemO(m+1)+, and FemO(m+2)+, and this strongly suggests that, for a given m, the most prevalent neutral clusters are of the forms FemOm, FemO(m+1), and FemO(m+2). As the value of m increases, the more oxygen rich neutral clusters appear to increase in stability.

Journal Article↗
PubMed2004

Collision-energy-resolved Penning ionization electron spectroscopy of bromomethanes (CH3Br, CH2Br2, and CHBr3) by collision with He*(2(3)S) metastable atoms.

Ionization of bromomethanes (CH3Br, CH2Br2, and CHBr3) upon collision with metastable He*(2(3)S) atoms has been studied by means of collision-energy-resolved Penning ionization electron spectroscopy. Lone-pair (nBr) orbitals of Br4p characters have larger ionization cross sections than sigma(C-Br) orbitals. The collision-energy dependence of the partial ionization cross sections shows that the interaction potential between the molecule and the He*(2(3)S) atom is highly anisotropic around CH3Br or CH2Br2, while isotropic attractive interactions are found for CHBr3. Bands observed at electron energies of approximately 2 eV in the He*(2(3)S) Penning ionization electron spectra (PIES) of CH2Br2 and CHBr3 have no counterpart in ultraviolet (He I) photoionization spectra and theoretical (third-order algebraic diagrammatic construction) one-electron and shake-up ionization spectra. Energy analysis of the processes involved demonstrates that these bands and further bands overlapping with sigma(C-Br) or piCH2 levels are related to autoionization of dissociating (He+ - Br-) pairs. Similarly, a band at an electron energy of approximately 1 eV in the He*(2(3)S) PIES spectra of CH3Br has been ascribed to autoionizing Br** atoms released by dissociation of (unidentified) excited states of the target molecule. A further autoionization (S) band can be discerned at approximately 1 eV below the lone-pair nBr bands in the He*(2(3)S) PIES spectrum of CHBr3. This band has been ascribed to the decay of autoionizing Rydberg states of the target molecule (M**) into vibrationally excited states of the molecular ion. It was found that for this transition, the interaction potential that prevails in the entrance channel is merely attractive.

Journal Article↗
PubMed2005

Charge transfer in the Cl-CO cluster induced by core ionization.

Ab initio calculations of core-ionization spectra of the anion-molecule Cl-CO cluster are performed. Particular attention is paid to the investigation of charge-transfer screening processes accompanying core ionization of the CO molecule in the cluster. The charge-transfer processes are very efficient and favored by the presence of a low-lying unoccupied pi* orbital in CO capable of accepting an electron from Cl-. The O1s(-1) and C1s(-1) core-ionization spectra are calculated and compared. Both reveal a breakdown of the quasiparticle picture of core ionization caused by the charge-transfer processes. Remarkable differences between these two spectra are found which manifest themselves in distinct intensity distributions in the prominent low-energy spectral bands. The underlying reason for these differences is elucidated and linked with the preference of the pi* orbital to localize mainly on carbon. Core-ionization spectra of anion-molecule clusters are very sensitive to the type of the molecule involved as the comparative analysis of the O1s(-1) core-ionization spectra of the Cl-CO and Cl-H(2)O clusters show.

Journal Article↗
PubMed2005

Competitive charge- and energy-transfer processes following core ionization in the Na- CO cluster.

Anion-molecule clusters constitute a very suitable class of systems for studying intermolecular (interatomic) charge-transfer (CT) processes following core ionization. A weakly bound electron of the anion in these clusters can be easily transferred to the core-ionized molecule. The screening effect of this electron may have a dramatic impact on core-level spectra and even account for a breakdown of the quasiparticle picture of core ionization. This is demonstrated here by calculating the O1s(-1) and C1s(-1) core ionization spectra of the Na- CO cluster using an ab initio fourth-order Green's-function method. Interestingly, along with the CT processes in this cluster there exist also very efficient energy-transfer (ET) processes favored by the low excitation energies of Na-. These ET processes constitute an appreciable part of the electronic excitations following core ionization of Na- CO and exert thereby a strong influence on the spectra studied. The spectral features attributed to the ET processes are as pronounced as those attributed to the CT processes. Major differences in the behavior of CT and ET satellites as a function of the anion-molecule separation are found and explained. We compare also the O1s(-1) core ionization spectra of the Na- CO and Na- H2O clusters. Along with a certain similarity, these spectra exhibit substantial differences which are essentially attributed to the distinct cluster geometries.

Journal Article↗
PubMed2006

Study of the molecular structure, ionization spectrum, and electronic wave function of 1,3-butadiene using electron momentum spectroscopy and benchmark Dyson orbital theories.

The scope of the present work is to reconcile electron momentum spectroscopy with elementary thermodynamics, and refute conclusions drawn by Saha et al. in J. Chem. Phys. 123, 124315 (2005) regarding fingerprints of the gauche conformational isomer of 1,3-butadiene in electron momentum distributions that were experimentally inferred from gas phase (e,2e) measurements on this compound [M. J. Brunger et al., J. Chem. Phys. 108, 1859 (1998)]. Our analysis is based on thorough calculations of one-electron and shake-up ionization spectra employing one-particle Green's function theory along with the benchmark third-order algebraic diagrammatic construction [ADC(3)] scheme. Accurate spherically averaged electron momentum distributions are correspondingly computed from the related Dyson orbitals. The ionization spectra and Dyson orbital momentum distributions that were computed for the trans-conformer of 1,3-butadiene alone are amply sufficient to quantitatively unravel the shape of all available experimental (e,2e) electron momentum distributions. A comparison of theoretical ADC(3) spectra for the s-trans and gauche energy minima with inner- and outer-valence high-resolution photoelectron measurements employing a synchrotron radiation beam [D. M. P. Holland et al., J. Phys. B 29, 3091 (1996)] demonstrates that the gauche structure is incompatible with ionization experiments in high-vacuum conditions and at standard temperatures. On the other hand, outer-valence Green's function calculations on the s-trans energy minimum form and approaching basis set completeness provide highly quantitative insights, within approximately 0.2 eV accuracy, into the available experimental one-electron ionization energies. At last, analysis of the angular dependence of relative (e,2e) ionization intensities nicely confirms the presence of one rather intense pi(-2) pi(*+1) satellite at approximately 13.1 eV in the ionization spectrum of the s-trans conformer.

Journal Article↗
PubMed1990

Ionizing radiation regulates expression of the c-jun protooncogene.

There is little known about the regulation of gene expression by ionizing radiation exposure. The present studies demonstrate transcriptional activation of a mammalian gene, the c-jun protooncogene, by x-rays. The c-jun gene encodes a component of the AP-1 protein complex and is important in early signaling events involved in various cellular functions. The increase in c-jun transcripts by ionizing radiation was time- and dose-dependent as determined by Northern blot analysis. Transcriptional run-on analysis demonstrated that ionizing radiation stimulates the rate of c-jun gene transcription. Furthermore, the half-life of c-jun RNA was prolonged in the absence of protein synthesis. These findings indicate that the increase in c-jun RNA observed after irradiation is regulated by transcriptional and posttranscriptional mechanisms. Moreover, the induction of c-jun by ionizing radiation was associated with an inverse dose rate effect in that decreasing the dose rate resulted in increased c-jun expression. The present results similarly demonstrate that ionizing radiation increases levels of c-fos transcripts as well as that of jun-B, another member of the jun family. Taken together, these results suggest a role for induction of early response genes in the pathophysiologic effects of ionizing radiation.

Blotting, Northern↗
PubMed2000

Clustered DNA damages induced in isolated DNA and in human cells by low doses of ionizing radiation.

Clustered DNA damages-two or more closely spaced damages (strand breaks, abasic sites, or oxidized bases) on opposing strands-are suspects as critical lesions producing lethal and mutagenic effects of ionizing radiation. However, as a result of the lack of methods for measuring damage clusters induced by ionizing radiation in genomic DNA, neither the frequencies of their production by physiological doses of radiation, nor their repairability, nor their biological effects are known. On the basis of methods that we developed for quantitating damages in large DNAs, we have devised and validated a way of measuring ionizing radiation-induced clustered lesions in genomic DNA, including DNA from human cells. DNA is treated with an endonuclease that induces a single-strand cleavage at an oxidized base or abasic site. If there are two closely spaced damages on opposing strands, such cleavage will reduce the size of the DNA on a nondenaturing gel. We show that ionizing radiation does induce clustered DNA damages containing abasic sites, oxidized purines, or oxidized pyrimidines. Further, the frequency of each of these cluster classes is comparable to that of frank double-strand breaks; among all complex damages induced by ionizing radiation, double-strand breaks are only about 20%, with other clustered damage constituting some 80%. We also show that even low doses (0.1-1 Gy) of high linear energy transfer ionizing radiation induce clustered damages in human cells.

Bacteriophage T7↗
PubMed1999

Mitogen-activated protein kinase kinase 2 activation is essential for progression through the G2/M checkpoint arrest in cells exposed to ionizing radiation.

An increasing body of evidence suggests that mitogen-induced activation of the RAF/ERK signaling pathway is functionally separate from the stress-induced activation of the SEK/JNK/p38 signaling pathway. In general, stress stimuli strongly activate the p38s and the JNKs while only weakly activating ERK1 and ERK2. However, a number of independent groups have now shown that the RAF/ERK signaling pathway is strongly activated by ionizing radiation. In this work, we examine this paradox. We show that both mitogen-activated protein (MAP) kinase kinase 1 (MEK1) and MAP kinase kinase 2 (MEK2) are activated by ionizing radiation. Blockage of this activation through the use of dominant negative MEK2 increases sensitivity of the cell to ionizing radiation and decreases the ability of a cell to recover from the G2/M cell cycle checkpoint arrest. Blocking MEK2 activation does not affect double-strand DNA break repair, however. Although MEK1 is activated to a lesser extent by ionizing radiation, expression of a dominant negative MEK1 does not affect radiation sensitivity of the cell, the G2/M checkpoint of the cell, or double-strand break repair. Because ionizing radiation leads to a different cell cycle arrest (G2/M arrest) than that typically seen with other stress stimuli, and because we have shown that MEK2 can affect G2/M checkpoint kinetics, these results provide an explanation for the observation that the MEKs can be strongly activated by ionizing radiation and only weakly activated by other stressful stimuli.

3T3 Cells↗
PubMed1989

The initial physical damage produced by ionizing radiations.

Biophysical studies of different ionizing radiations and their differences in biological effect can provide useful information and constraints on the nature of the initial biologically relevant damage and hence the subsequent biochemistry and repair processes. It is clear that the nature of the predominant critical component produced by densely ionizing (high-LET) radiations is qualitatively, as well as quantitatively, different from that which predominates for low-LET radiations. Comparisons of radiation track structure with observed biological effects of the radiations allow hypotheses to be developed as to the nature of these different types of damage. That associated with low-LET radiations seems consistent with what is known about DNA double-strand breaks (dsb). It is produced predominantly by a localized cluster of ionizations within a single electron 'track end' either by direct action on the DNA or in conjunction with closely-associated molecules. The characteristic high-LET damage is somewhat larger in number of ionizations and spatial extent and therefore presumably also in molecular complexity. It is suggested that the total spectrum of initial damage be categorized into four classes; in addition to the above two this would include on the one extreme sparse isolated ionizations, which may lead to very simple products that are of limited biological relevance, and on the other extreme very large and relatively rare events which are uniquely achievable by some high-LET radiations, such as alpha-particles, but not at all by low-LET radiations. These biophysical considerations pose a challenge to radiation chemistry studies to consider the chemical consequences of highly localized clusters of initial ionizations and excitations in or very near to DNA, and to biochemistry to consider classes of damage involving DNA (and perhaps associated molecules) of greater complexity than the simplest dsb.

Cells↗
PubMed2005

The effect of alpha-phenyl-N-t-butylnitrone on ionizing radiation-induced apoptosis in U937 cells.

Ionizing radiation induces the production of reactive oxygen species (ROS), which play an important causative role in apoptotic cell death. alpha-Phenyl-N-t-butylnitrone (PBN) is one of the most widely used spin-trapping compounds for investigating the existence of free radicals in biological systems. We investigated the effects of PBN on ionizing radiation-induced apoptosis in U937 cells. Upon exposure to 2 Gy of gamma-irradiation, there was a distinct difference between the control cells and the cells pre-treated with 2 mM PBN for 2 h in regard to apoptotic parameters, cellular redox status, mitochondria function and oxidative damage to cells. PBN effectively suppressed morphological evidence of apoptosis and DNA fragmentation in U937 cells exposed to ionizing radiation. The [GSSG]/[GSH+GSSG] ratio and the generation of intracellular ROS were higher and the [NADPH]/[NADP+ +NADPH] ratio was lower in control cells compared to PBN-treated cells. The ionizing radiation-induced mitochondrial damage reflected by the altered mitochondrial permeability transition, the increase in the accumulation of ROS, and the reduction of ATP production were significantly higher in control cells compared to PBN-treated cells. PBN pre-treated cells showed significant inhibition of apoptotic features such as activation of caspase-3, up-regulation of Bax and p53, and down-regulation of Bcl-2 compared to control cells upon exposure to ionizing radiation. This study indicates that PBN may play an important role in regulating the apoptosis induced by ionizing radiation presumably through scavenging of ROS.

Adenosine Triphosphate↗
PubMed1998

Changes in ionized calcium concentrations and acid-base status during abdominal aortic vascular surgery.

Abdominal aortic surgery may produce significant haemodynamic instability (from a combination of factors: hypovolaemia, acid-base disturbances, vasoactive metabolite release from ischaemic tissues and hypocalcaemia). Calcium is often given after aortic unclamping to attenuate this instability. We studied 20 patients undergoing elective abdominal aortic surgery and observed a triphasic change in ionized calcium concentrations and acid-base status. Initially, during the cross-clamp period (when patients were cardiovascularly stable), ionized calcium concentrations decreased significantly (mean 1.06 (SD 0.08) to 0.91 (0.13) mmol litre-1; P < 0.01), while a significant metabolic acidosis developed (pH 7.38 (0.05) to 7.30 (0.05); P < 0.05). Second, release of the aortic cross-clamp resulted in further acidosis (pH 7.27 (0.05) (P < 0.05) mixed respiratory and metabolic) with a decrease in mean arterial pressure, with no change in ionized calcium concentrations. The third phase was associated with spontaneous restoration of acid-base status and ionized calcium concentrations to normal over 2 h. There was no correlation between units of blood given, volume of blood lost, fluid volume given or duration of aortic cross-clamping and degree of ionized hypocalcaemia. We conclude that ionized hypocalcaemia occurred during the cross-clamp period of aortic surgery, was unrelated to the volume of blood given and did not appear to be responsible for the changes in arterial pressure during surgery.

Acid-Base Equilibrium↗
PubMed1990

Ionized calcium in human male and female reproductive fluids: relationships to sperm motility.

The levels of ionized calcium in seminal plasma were approximately 20% of the serum levels. In contrast, cervical mucus contained a level of ionized calcium similar to both serum and follicular fluid. Titration of seminal plasma and serum with increasing concentrations of calcium chloride indicated a 10-fold higher calcium-binding capacity for seminal plasma. In a random group of men under semen investigation, concentrations of ionized calcium and citrate in semen were inversely correlated (r = 0.732; P less than 0.001), an observation which was confirmed by studies of split ejaculates. These findings supported the contention that citrate is the major regulator of the levels of ionized calcium in seminal plasma and primarily responsible for maintaining the calcium gradient between the seminal plasma and cervical mucus. No significant relationship could be demonstrated between the levels of ionized calcium in the ejaculates and any of the motility characteristics of the spermatozoa in the same sample. Furthermore, the addition of increasing quantities of calcium chloride (0.16-20.00 mM) to washed spermatozoa had no major effects on their progressive motility. These data suggest that human spermatozoa are effective in maintaining an appropriate level of internal ionized calcium, necessary for normal motility, despite fluctuations in external calcium.

Ascitic Fluid↗
PubMed1990

Ionized calcium, parathormone, and mortality in critically ill surgical patients.

A prospective study measured ionized calcium and parathormone sequentially at 48- to 72-hour intervals in 25 surgical intensive care unit patients. Twelve patients (48%) died at mean day 40 and median day 26. Levels of ionized calcium, parathormone, blood urea nitrogen, creatinine, albumin, magnesium, and phosphate for patients who lived were compared with levels for patients who died. The incidence of hypotension, renal failure (creatinine greater than or equal to 3.0), and bacteremia, as well as the amount of red cell, crystalloid, and colloid administration for the two groups was compared. Hypotension, bacteremia, red cells, crystalloid, and colloid were no different. On days 1 and 2 ionized calcium levels were significantly lower and parathormone levels significantly higher in nonsurviving patients; this difference persisted through days 3 and 4. Blood urea nitrogen and creatinine levels increased early in nonsurviving patients but renal failure, which occurred in nine nonsurviving patients, did not develop until mean day 14, median day 18. The phosphate level was slightly higher but still within normal range in nonsurviving patients. By days 5 and 6 ionized calcium and parathormone levels were no different in nonsurviving patients, despite there being no improvement in renal function. Magnesium and albumin levels were no different between groups. Ionized calcium levels are lower and parathormone levels higher early in nonsurviving patients. This difference is not readily explained by associated clinical conditions, including renal dysfunction. Although etiology remains unclear, low ionized calcium and elevated parathormone are early predictors of mortality in critically ill surgical patients.

Aged↗
PubMed1995

Relationship between blood lactate concentrations and ionized calcium, glucose, and acid-base status in critically ill and noncritically ill patients.

OBJECTIVE: To determine the relationships between circulating blood lactate concentrations and several biochemical variables including ionized calcium, glucose, pH, and acid-base status in critically ill and noncritically ill patients. DESIGN: A prospective, cohort study. SETTING: The critical care research laboratory, intensive care unit (ICU), emergency room (ER), and general ward of a 466 bed university-affiliated hospital. PATIENTS: Three-hundred thirty-four critically ill and noncritically ill patients. INTERVENTION: None. MEASUREMENTS AND MAIN RESULTS: Circulating blood lactate concentrations, ionized calcium concentrations, blood glucose, pH, and base deficit values were simultaneously determined in blood samples from various patient populations. Descriptive data and physiologic parameters were also recorded. Circulating lactate and ionized calcium determinations were performed simultaneously in 334 whole blood samples from 334 subjects. There was neither a statistically significant nor clinically relevant correlation between circulating lactate concentrations and ionized calcium concentrations when lactate values were < or = 2 mmol/L (p = 0.8962, r2 = .01) or when lactate values were > 2 mmol/L (p = .3697, r2 = .09) in a heterogeneous patient population. Our study populations included five subject groups: a) nonhypotensive ICU patients (n = 93), b) nonhypotensive ER patients (n = 85), c) nonhypotensive general ward patients (n = 44), d) hypotensive patients from the ICU, ER, and general wards (n = 39), and e) normal controls (n = 73). There was neither a statistically significant nor clinically relevant correlation between circulating lactate concentrations and ionized calcium concentrations in each of the five populations studied for lactate values either < or = 2 mmol/L or > 2 mmol/L. We studied the relationship between circulating lactate concentrations and blood glucose concentrations (n = 334 patients), arterial pH and base deficit (n = 163 patients), and venous pH and base deficit (n = 171 patients). Statistically significant, but perhaps not clinically relevant correlations were observed when comparing circulating lactate values with blood glucose values (p = .0330, r2 = .12), arterial pH (p = .0007, r2 = .26) and base deficit from arterial specimens (p = .0014, r2 = .25). There were neither statistically significant nor clinically relevant correlations when comparing circulating lactate concentrations with venous pH (p = .9098, r2 = .01) or base deficit determined from venous blood specimens (p = .1365, r2 = .11). CONCLUSIONS: a) There is neither a statistically significant nor clinically relevant relationship between whole blood lactate concentrations and ionized calcium concentrations when studying patients with or without hyperlactatemia. b) Although there is a statistically significant correlation between circulating lactate concentrations and blood glucose concentrations, arterial pH or arterial base deficit, such associations do not appear to be clinically important.

Acid-Base Equilibrium↗
PubMed1995

Arterial blood sampling devices influence ionized calcium measurements.

OBJECTIVE: To determine the effect of commercially available arterial blood sampling devices on ionized calcium measurements. DESIGN: Prospective study. SETTING: Neurosurgical and shock-trauma intensive care units (ICU) at a tertiary care teaching hospital. PATIENTS: Fourteen patients admitted to the ICU. Each patient had an indwelling arterial catheter. INTERVENTIONS: Arterial blood sampling. MEASUREMENTS AND MAIN RESULTS: In 14 ICU patients, measurements of arterial blood ionized calcium concentrations were performed, using 12 different commercially available arterial blood sampling devices. Significant underestimation of ionized calcium in blood samples compared with the reference test tube (Vacutainer 45) was seen in seven of the devices. Arterial blood ionized calcium concentrations measured, using one commercially available syringe, were significantly higher compared with the reference test tube. There was no correlation between either the amount or type of heparin in the arterial blood sampling devices and arterial blood ionized calcium measurement. CONCLUSIONS: This study demonstrates that various commercially available arterial blood sampling devices alter arterial blood ionized calcium measurements. These alterations are clinically important because ICU patients may be treated with inappropriate calcium supplementation.

Arteries↗