[Comment on article "Variability of hemoglobin and hematocrit determined in blood gas equipment"]. / Comentario al artículo "Variabilidad de la hemoglobina y hematocrito determinados en equipo de gases sanguíneos".

´The analysis of samples on different equipment may lead to variation between results; in the article "Variability of hemoglobin and hematocrit determined in blood gas equipment", the authors talk about the variability of hemoglobin and hematocrit between an automated hematology analyzer and an arterial blood gas analyzer. Information is requested on some aspects considered relevant to improve the understanding of the conclusions.

El análisis de muestras en diferentes equipos puede conllevar una variación entre los resultados; en el artículo "Variabilidad de la hemoglobina y hematocrito determinados en equipo de gases sanguíneos", sus autores hablan de la variabilidad de hemoglobina y hematocrito entre un analizador automatizado de hematología y un analizador de gases arteriales. Se solicita información sobre algunos aspectos considerados relevantes para mejorar la compresión de las conclusiones.

PaCO2-management in the neuro-critical care of patients with subarachnoid hemorrhage.

The partial pressure of carbon dioxide (PaCO2) in the arterial blood is a strong vasomodulator affecting cerebral blood flow and the risk of cerebral edema and ischemia after acute brain injury. In turn, both complications are related to poor outcome in patients with aneurysmal subarachnoid hemorrhage (aSAH). We aimed to analyze the effect of PaCO2 levels on the course and outcome of aSAH. All patients of a single institution treated for aSAH over 13.5 years were included (n = 633). Daily PaCO2 values from arterial blood gas measurements were recorded for up to 2 weeks after ictus. The study endpoints were: delayed cerebral ischemia (DCI), need for decompressive craniectomy due to increased intracranial pressure > 20 mmHg refractory to conservative treatment and poor outcome at 6-months follow-up (modified Rankin scale > 2). By correlations with the study endpoints, clinically relevant cutoffs for the 14-days mean values for the lowest and highest daily PaCO2 levels were defined by receiver operating characteristic curve analysis. Association with the study endpoints for the identifies subgroups was analyzed using multivariate analysis. The optimal range for PaCO2 values was identified between 30 and 38 mmHg. ASAH patients with poor initial condition (WFNS 4/5) were less likely to show PaCO2 values within the range of 30-38 mmHg (p < 0.001, OR = 0.44). In the multivariate analysis, PaCO2 values between 30 and 38 mmHg were associated with a lower risk for decompressive craniectomy (p = 0.042, aOR = 0.27), DCI occurrence (p = 0.035; aOR = 0.50), and poor patient outcome (p = 0.004; aOR = 0.42). The data from this study shows an independent positive association between low normal mean PaCO2 values during the acute phase of aSAH and patients' outcome. This effect might be attributed to the reduction of intracranial hypertension and alterations in the cerebral blood flow.

Accuracy of two pulse-oximetry measurements for INTELLiVENT-ASV in mechanically ventilated patients: a prospective observational study.

Recently, maintaining a certain oxygen saturation measured by pulse oximetry (SpO2) range in mechanically ventilated patients was recommended; attaching the INTELLiVENT-ASV to ventilators might be beneficial. We evaluated the SpO2 measurement accuracy of a Nihon Kohden and a Masimo monitor compared to actual arterial oxygen saturation (SaO2). SpO2 was simultaneously measured by a Nihon Kohden and Masimo monitor in patients consecutively admitted to a general intensive care unit and mechanically ventilated. Bland-Altman plots were used to compare measured SpO2 with actual SaO2. One hundred mechanically ventilated patients and 1497 arterial blood gas results were reviewed. Mean SaO2 values, Nihon Kohden SpO2 measurements, and Masimo SpO2 measurements were 95.7%, 96.4%, and 96.9%, respectively. The Nihon Kohden SpO2 measurements were less biased than Masimo measurements; their precision was not significantly different. Nihon Kohden and Masimo SpO2 measurements were not significantly different in the "SaO2 < 94%" group (P = 0.083). In the "94% ≤ SaO2 < 98%" and "SaO2 ≥ 98%" groups, there were significant differences between the Nihon Kohden and Masimo SpO2 measurements (P < 0.0001; P = 0.006; respectively). Therefore, when using automatically controlling oxygenation with INTELLiVENT-ASV in mechanically ventilated patients, the Nihon Kohden SpO2 sensor is preferable.Trial registration UMIN000027671. Registered 7 June 2017.

Arterial blood gas as a prognostic indicator in patients with sepsis.

Abnormal arterial blood gas (ABG) among patients with sepsis is an important prognostic indicator. All-cause mortality was the highest among patients with respiratory acidosis (4/9 = 44.4%), followed by those having metabolic acidosis (3/8 = 37.5%). Median length of hospital and intensive care unit stay was 15.75 days and 6.25 days for those with abnormal ABG and 11 and 3.5 days among those with normal ABG. Median health-care expenditure at the time of discharge or death of the patient was the highest in patients with respiratory acidosis ($14,473) and least in patients with normal ABG ($3,384) (average expenditure among patients with abnormal ABG was [$10,059]).

Determining the predictive capability of a Clinical Assessment Scoring Chart to differentiate severity of the clinical consequences of neonatal calf diarrhea relative to gold-standard blood gas analysis.

Neonatal calf diarrhea (NCD) is a major problem to calf health worldwide, in terms of both morbidity and mortality. A five-point ordinal scale clinical assessment scoring (CAS) chart was utilized to assess calves suffering from NCD-related clinical abnormalities (acidosis and dehydration) on commercial farms. The objective of this research was to determine the predictive capability of this CAS chart against gold standard blood gas parameters, designed to assist farmers in the accurate assessment of the clinical consequences of NCD. A total of 443 diarrheic and non-diarrheic calves were enrolled in the study. The CAS chart rated a calf's health from no clinical signs to varying degrees of clinical severity on a 0 (clinically normal) to 4 (grave) scale, based on clinical indicators including calf demeanour, ear position, mobility, suckle reflex, desire-to-feed, and enophthalmos. Blood gas analysis was conducted for individual calves, consisting of pH, base excess, Na+, K+, Ca2+, Cl-, glucose, total hemoglobin, bicarbonate, anion gap, and strong ion difference. Statistical evaluation was performed by comparison of the CAS score with blood gas profiles using ordinal logistic regression and a non-parametric estimation of the Receiver Operating Characteristics (ROC). The ROC analysis indicated that the CAS chart had acceptable specificity (>95%) with low sensitivity (<60%) in differentiating clinically normal from acidotic/dehydrated cases. Assessment of individual severity classes indicated that the chart can predict and differentiate both clinically normal and advanced cases from the other severity classes (peak estimations >80%) but had reduced accuracy in differentiating mild and moderate cases (peak estimations >50%). The chart, as presented, provides a simple tool to differentiate clinically normal from calves suffering the consequences of diarrhea, but fails to accurately differentiate severity for NCD related acidosis and dehydration. Further efforts are required to enhance the sensitivity and differential diagnostic value of this type of chart.

Serial single breath count is a reliable tool for monitoring respiratory functions in Guillain-Barré Syndrome.

In this study, we correlate single breath count (SBC) with arterial blood gas (ABG) parameters to derive a cutoff point for intubation and mechanical ventilation (MV) in Guillain-Barré Syndrome (GBS). Ninety-four GBS patients underwent serial SBC at 2 Hz using an audio program. ABG was done at admission, and repeated if SBC declined. The patients were intubated based on "the modified intubation criteria" as follows (a + b or c): (a) hypoxia (PaO2 < 60 mm of Hg on ventimask); (b) hypercarbia (PaCO2 > 50 mm of Hg); (c) acidosis (pH < 7.3). The primary outcome was the absolute SBC at which patients had ABG alteration needing intubation. All the patients maintained a desired ABG without respiratory distress till SBC 7. At SBC 5, need for MV could be predicted with a sensitivity of 90.6% and specificity of 95.2%. Admission SBC cut-off of 13 and relative delta SBC at 24 h cut-off of > 20% had a negative predictive value of 88.5% (95% CI 77.0%-96.0%) and 80.8% (95% CI 60.7%-93.4%) respectively for ruling out need of MV. SBC is a useful non-invasive measure for monitoring respiratory function and guiding ABG analysis. Till SBC 7, repeated ABG may be avoided in GBS.

Arterial blood gas analysis utility in predicting lung injury in blunt chest trauma.

BACKGROUND: thoracic trauma is one of the leading causes of death in all age groups and accounts for 25-50 % of all traumatic injuries. With the term lung injury in blunt chest trauma, we identified a spectrum of conditions: lung contusion, pneumothorax and haemothorax. The aim of this study was to evaluate the utility of arterial blood gas analysis parameters in predicting lung injury in blunt chest trauma. METHODS: we included 51 patients presenting to the Emergency Department of "C.T.O." Hospital in Naples [Italy] for blunt chest trauma. The patients were assigned to the Lung Injury Group or to the Non-Lung Injury Group basing on CT scan findings. For each patient, we calculated the alveolar-arterial oxygen gradient [AaDO2], the AaDO2 augmentation, the arterial partial pressure of oxygen deficit [PaO2 Deficit] and the ratio between arterial partial pressure of oxygen and fraction of inspired oxygen [P/F]. Areas under the curve [AUC] and receiver operating characteristic [ROC] curve were used to compare the performance of each different test in relation to the detection of lung injury in blunt chest trauma. RESULTS: patients with lung injury had lower oxygen saturation, arterial partial pressure of oxygen, P/F and higher PaO2 Deficit, AaDO2, AaDO2 augmentation than patients without lung injury. PaO2 Deficit, AaDO2 and AaDO2 augmentation showed a good accuracy to predict lung injury in blunt chest trauma. CONCLUSION: our study demonstrates that the combination of different arterial blood gas analysis variables may be a fast approach for identifying patients with lung injury in the setting of blunt chest trauma in the Emergency Department.

Odd haemoglobins in odd-toed ungulates: Impact of selected haemoglobin characteristics of the white rhinoceros (Ceratotherium simum) on the monitoring of the arterial oxygen saturation of haemoglobin.

BACKGROUND: Due to the current poaching crisis in Africa, increasing numbers of white rhinoceroses (Ceratotherium simum) require opioid immobilisation for medical interventions or management procedures. Alarmingly, the results of both blood gas analysis and pulse oximetry regularly indicate severe hypoxaemia. Yet, the recovery of the animals is uneventful. Thus, neither of the techniques seems to represent the real oxygenation level. We hypothesized that unusual haemoglobin characteristics of this species interfere with the techniques developed and calibrated for the use in human patients. METHODS: Haemoglobin was isolated from blood samples of four adult, white rhinoceroses. Oxygen dissociation curves at pH 7.2 and 7.4 (37°C) were determined based on the absorbance change of haemoglobin in the Soret-region (around 420 nm). Absorbance spectra of oxy- and deoxyhaemoglobin extending into the infrared region were measured. RESULTS: Oxygen dissociation curves of rhinoceros haemoglobin showed the typical high oxygen affinity (p50 of 2.75 ± 0.07 and 2.00 ± 0.04 kPa for pH 7.2 and 7.4, respectively) under near-physiological conditions with respect to pH, temperature and DPG. The infrared absorbance spectra of oxy- and deoxyhaemoglobin showed only marginal deviations from standard human spectra, possibly due to the presence of a few percent of methaemoglobin in vitro. CONCLUSIONS: Our data enables the development of a rhinoceros-specific blood gas analysis algorithm, which allows for species-specific calculation of SaO2 levels in anaesthetized animals. The inconspicuous absorbance spectra do not contribute to the systematic underestimation of SpO2 by pulse-oximetry.

Guidelines on the management of acute respiratory distress syndrome.

The Faculty of Intensive Care Medicine and Intensive Care Society Guideline Development Group have used GRADE methodology to make the following recommendations for the management of adult patients with acute respiratory distress syndrome (ARDS). The British Thoracic Society supports the recommendations in this guideline. Where mechanical ventilation is required, the use of low tidal volumes (<6 ml/kg ideal body weight) and airway pressures (plateau pressure <30 cmH2O) was recommended. For patients with moderate/severe ARDS (PF ratio<20 kPa), prone positioning was recommended for at least 12 hours per day. By contrast, high frequency oscillation was not recommended and it was suggested that inhaled nitric oxide is not used. The use of a conservative fluid management strategy was suggested for all patients, whereas mechanical ventilation with high positive end-expiratory pressure and the use of the neuromuscular blocking agent cisatracurium for 48 hours was suggested for patients with ARDS with ratio of arterial oxygen partial pressure to fractional inspired oxygen (PF) ratios less than or equal to 27 and 20 kPa, respectively. Extracorporeal membrane oxygenation was suggested as an adjunct to protective mechanical ventilation for patients with very severe ARDS. In the absence of adequate evidence, research recommendations were made for the use of corticosteroids and extracorporeal carbon dioxide removal.

Continuous Noninvasive Carbon Dioxide Monitoring in Neonates: From Theory to Standard of Care.

Ventilatory support may affect the short- and long-term neurologic and respiratory morbidities of preterm infants. Ongoing monitoring of oxygenation and ventilation and control of adequate levels of oxygen, pressures, and volumes can decrease the incidence of such adverse outcomes. Use of pulse oximetry became a standard of care for titrating oxygen delivery, but continuous noninvasive monitoring of carbon dioxide (CO2) is not routinely used in NICUs. Continuous monitoring of CO2 level may be crucial because hypocarbia and hypercarbia in extremely preterm infants are associated with lung and brain morbidities, specifically bronchopulmonary dysplasia, intraventricular hemorrhage, and cystic periventricular leukomalacia. It is shown that continuous monitoring of CO2 levels helps in maintaining stable CO2 values within an accepted target range. Continuous monitoring of CO2 levels can be used in the delivery room, during transport, and in infants receiving invasive or noninvasive respiratory support in the NICU. It is logical to hypothesize that this will result in better outcome for extremely preterm infants. In this article, we review the different noninvasive CO2 monitoring alternatives and devices, their advantages and disadvantages, and the available clinical data supporting or negating their use as a standard of care in NICUs.

Can the blood gas analyser results be believed? A prospective multicentre study comparing haemoglobin, sodium and potassium measurements by blood gas analysers and laboratory auto-analysers.

Blood gas analysers are point-of-care testing devices used in the management of critically ill patients. Controversy remains over the agreement between the results obtained from blood gas analysers and laboratory auto-analysers for haematological and biochemistry parameters. We conducted a prospective analytical observational study in five intensive care units in Western Australia, in patients who had a full blood count (FBC), urea, electrolytes and creatinine (UEC), and a blood gas performed within 1 h of each other during the first 24 h of their intensive care unit admission. The main outcome measure was to determine the agreement in haemoglobin, sodium, and potassium results between laboratory haematology and biochemistry auto-analysers and blood gas analysers. A total of 219 paired tests were available for haemoglobin and sodium, and 215 for potassium. There was no statistically significant difference between the results of the blood gas and laboratory auto-analysers for haemoglobin (mean difference -0.35 g/L, 95% confidence interval (CI) -1.20 to 0.51, P = 0.425). Although the mean differences between the two methods were statistically significant for sodium (mean difference 1.49 mmol/L, 95% CI 1.23-1.76, P < 0.0001) and potassium (mean difference 0.19 mmol/L, 95% CI 0.15-0.24, P < 0.0001), the mean biases on the Bland-Altman plots were small and independent of the magnitude of the measurements. The two methods of measurement for haemoglobin, sodium and potassium agreed with each other under most clinical situations when their values were within or close to normal range suggesting that routine concurrent blood gas and formal laboratory testing for haemoglobin, sodium and potassium concentrations in the intensive care unit is unwarranted.

Continuous Monitoring of pH and Blood Gases Using Ion-Sensitive and Gas-Sensitive Field Effect Transistors Operating in the Amperometric Mode in Presence of Drift.

Accurate and cost-effective integrated sensor systems for continuous monitoring of pH and blood gases continue to be in high demand. The capacity of ion-selective and Gas-sensitive field effect transistors (FETs) to serve as low-power sensors for accurate continuous monitoring of pH and blood gases is evaluated in the amperometric or current mode of operation. A stand-alone current-mode topology is employed in which a constant bias is applied to the gate with the drain current serving as the measuring signal. Compared with voltage-mode operation (e.g., in the feedback mode in ion-selective FETs), current-mode topologies offer the advantages of small size and low power consumption. However, the ion-selective FET (ISFET) and the Gas-sensitive FET (GasFET) exhibit a similar drift behavior, imposing a serious limitation on the accuracy of these sensors for continuous monitoring applications irrespective of the mode of operation. Given the slow temporal variation associated with the drift characteristics in both devices, a common post-processing technique that involves monitoring the variation of the drain current over short intervals of time can potentially allow extraction of the measuring signal in presence of drift in both sensor types. Furthermore, in the amperometric mode the static sensitivity of a FET-based sensor, given by the product of the FET transconductance and the sensitivity of the device threshold voltage to the measurand concentration, can be increased by adjusting the device design parameters. Increasing the sensitivity, while of interest in its own right, also enhances the accuracy of the proposed method. Rigorous analytical validation of the method is presented for GasFET operation in the amperometric mode. Moreover, the correction algorithm is verified experimentally using a Si3N4-gate ISFET operating in the amperometric mode to monitor pH variations ranging from 3.5 to 10.

Verification testing to confirm VO2max attainment in persons with spinal cord injury.

Context/Objective: Maximal oxygen uptake (VO2max) is a widely used measure of cardiorespiratory fitness, aerobic function, and overall health risk. Although VO2max has been measured for almost 100 yr, no standardized criteria exist to verify VO2max attainment. Studies document that incidence of 'true' VO2max obtained from incremental exercise (INC) can be confirmed using a subsequent verification test (VER). In this study, we examined efficacy of VER in persons with spinal cord injury (SCI).Design: Repeated measures, within-subjects study.Setting: University laboratory in San Diego, CA.Participants: Ten individuals (age and injury duration = 33.3 ± 10.5 yr and 6.8 ± 6.2 yr) with SCI and 10 able-bodied (AB) individuals (age = 24.1 ± 7.4 yr).Interventions: Peak oxygen uptake (VO2peak) was determined during INC on an arm ergometer followed by VER at 105 percent of peak power output (% PPO).Outcome Measures: Gas exchange data, heart rate (HR), and blood lactate concentration (BLa) were measured during exercise.Results: Across all participants, VO2peak was highly related between protocols (ICC = 0.98) and the mean difference was equal to 0.08 ± 0.11 L/min. Compared to INC, VO2peak from VER was not different in SCI (1.30 ± 0.45 L/min vs. 1.31 ± 0.43 L/min) but higher in AB (1.63 ± 0.40 L/min vs. 1.76 ± 0.40 L/min).Conclusion: Data show similar VO2peak between incremental and verification tests in SCI, suggesting that VER confirms VO2max attainment. However, in AB participants completing arm ergometry, VER is essential to validate appearance of 'true' VO2peak.

Correlation between sodium, potassium, hemoglobin, hematocrit, and glucose values as measured by a laboratory autoanalyzer and a blood gas analyzer.

INTRODUCTION: Blood gas analyzers can be alternatives to laboratory autoanalyzers for obtaining test results in just a few minutes. We aimed to find out whether the results from blood gas analyzers are reliable when compared to results of core laboratory autoanalyzers. MATERIALS AND METHODS: This retrospective, single-centered study examined the electronic records of patients admitted to the emergency department of a tertiary care teaching hospital between May 2014 and December 2017. Excluded from the study were patients under 18 years old, those lacking data, those who had any treatment before the laboratory tests, those whose venous gas results were reported more than 30 minutes after the blood sample was taken and for whom any of the laboratory tests were performed at a different time, and recurrent laboratory results from a single patient. RESULTS: Laboratory results were analyzed from a total of 31,060 patients. The correlation coefficients for sodium, potassium, hemoglobin, hematocrit, and glucose levels measured by a blood gas analyzer and a laboratory autoanalyzer were 0.725, 0.593, 0.982, 0.958, and 0.984, respectively; however, there were no good, acceptable agreement limits for any of the parameters. In addition, these results did not change according to the different pH stages (acidosis, normal pH and alkalosis). CONCLUSION: The two types of measurements showed a moderate correlation for sodium and potassium levels and a strong correlation for glucose, hemoglobin, and hematocrit levels, but none of the levels had acceptable agreement limits. Clinicians should be aware of the limitations of blood gas analyzer results.

Base Excess usefulness for prediction of immediate mortality in severe trauma patients admitted to the Emergency department.

BACKGROUND: Trauma is a leading cause of death in young people and hemorrhagic shock is a leading mechanism of this mortality. Hypoperfusion can be difficult to diagnose clinically, especially in younger patients. Arterial Base Excess (BE) has been used as an early indicator of hypoperfusion. AIM: To evaluate the prognostic value of admission BE in severe trauma patients admitted to the emergency department (ED). METHODS: In this prospective study, severe trauma patients meeting high velocity criteria admitted to the ED during the study period were included. BE was calculated from arterial blood gas samples. Multivariate analysis was performed for Day-1 and Day-7 post trauma mortality. ROC characteristics and survival curves were used. RESULTS: We included 479 patients. Median age was 37 (18-90). Eighty-one per cent were male. Clinical characteristics n(%): GCS<13: 170(35); SBP<90 mmHg: 64(13) and SpO2 <90%: 82(17). Mean ISS was 22 ± 13. Mortality was at days 1 and 7: 2.2% and 27.3%, respectively. Median BE was -3.2 mmol/l (-25; 28). Forty-five per cent had a BE ≤ -3.5 mmol/l. In multivariate analysis, initial BE ≤ -6.5 mmol/l was predictive of first day mortality with an Odds Ratio; [CI95%] = 3.17; [1.4-7.1]; p=0.005. Similar results were found at Day 7: Odds Ratio; [CI95%] = 1.5; [1.14-1.96]; p=0.003. BE showed high prognostic value for both mortality rates. Survival curve was significant for BE> -6.5mmol/l. CONCLUSION: in this study, a high BE above 6.5mmol/L showed a significant prognostic value in immediate and early mortality and is proposed as a marker of injury severity in trauma patients admitted to the ED. Prediction was better for the immediate mortality and thus could be proposed as a triage tool in the ED.

Una mirada crítica a las consideraciones preanalíticas de gases sanguíneos / Uma análise crítica das considerações pré-analíticas dos gases sangüíneos / A critical look at the preanalytical considerations of blood gases

Introducción: uno de los asuntos menos discutidos y que poco se entiende del mismo, es la seguridad del paciente. Hace poco tiempo se ha convertido en un tema ubicuo y polémico, especialmente para algunas organizaciones médicas. Objetivo: sistematizar referentes teóricos relacionados con las particularidades del proceso de toma de muestra y análisis de los gases en sangre. Método: se revisan los principales elementos que gravitan en esta fase para el análisis de los gases sanguíneos, así como la influencia que estos pueden tener en la calidad de los resultados y las prácticas clínicas y de laboratorio para optimizarla. Desarrollo: la fase preanalítica es aquella que antecede a la realización de un ensayo o estudio de laboratorio e incluye la preparación del paciente, la confección de la solicitud de análisis y los cuidados para la obtención de las muestras. La atención que el médico de asistencia y el personal del laboratorio concedan a esta fase es directamente proporcional a la calidad de los resultados que se obtendrán. Conclusiones: el análisis de pH y gases sanguíneos deben ser considerados siempre como un estudio de urgencia. La muestra no debe permanecer por más de diez minutos a temperatura ambiente y cuando el análisis demore más de 15 minutos, la muestra deberá ser conservada en agua con hielo(AU)

Introduction: one of the least discussed issues and that little is understood about it, is patient safety. It has recently become a ubiquitous and controversial issue, especially for some medical organizations. Objective: to systematize theoretical references related to the particularities of the process of sample taking and analysis of blood gases. Method: the main elements that gravitate in this phase are analyzed for the blood gas analysis, as well as the influence that these can have on the quality of the results and the clinical and laboratory practices to optimize it. Development: the preanalytical phase is the one that precedes the performance of a trial or laboratory study and includes the preparation of the patient, the preparation of the analysis request and the care for obtaining the samples. The attention that the attending physician and laboratory staff give to this phase is directly proportional to the quality of the results that will be obtained. Conclusions: the analysis of pH and blood gases should always be considered as an emergency study. The sample should not remain for more than ten minutes at room temperature and when the analysis takes more than 15 minutes, the sample should be stored in ice water(au)

Introdução: uma das questões menos discutidas e que pouco é entendido sobre isso, é a segurança do paciente. Tornou-se recentemente uma questão onipresente e controversa, especialmente para algumas organizações médicas. Objetivo: sistematizar referenciais teóricos relacionados às particularidades do processo de coleta de amostras e análise de gases sangüíneos. Método: os principais elementos que gravitam nesta fase são analisados para a gasometria, assim como a influência que estes podem ter na qualidade dos resultados e nas práticas clínicas e laboratoriais para otimizá-la. Desenvolvimento: a fase pré-analítica é aquela que precede a realização de uma pesquisa ou estudo laboratorial e inclui a preparação do paciente, a elaboração do pedido de análise e o cuidado para obtenção das amostras. A atenção que o médico assistente e o pessoal de laboratório dão a essa fase é diretamente proporcional à qualidade dos resultados que serão obtidos. Conclusões: a análise do pH e dos gases sanguíneos deve ser sempre considerada como um estudo de emergência. A amostra não deve permanecer por mais de dez minutos em temperatura ambiente e quando a análise demora mais de 15 minutos, a amostra deve ser armazenada em água gelada(AU)

The discriminative value of blood gas analysis parameters in the differential diagnosis of transient disorders of consciousness.

AIM: The differentiation between epileptic and non-epileptic episodes can be challenging. Our aim was to compare lactate, anion gap (AG), bicarbonate and the Denver Seizure Score (DSS) as point-of-care test (POCT) markers for episodes of transient alterations of consciousness. METHODS: The blood serum parameters were drawn at arrival in the emergency department (ED) within 2 h of the episode. After calculating AG and DSS values, the four parameters were compared retrospectively between patients with generalized tonic-clonic seizures (GTCS) (n = 165) and patients with other disorders of consciousness [syncopes (n = 43), and psychogenic non-epileptic seizures (n = 15)]. Additionally, we compared all values among men and women. RESULTS: In GTCS patients, all four parameters differed significantly compared to non-epileptic episode patients (p < 0.001). Serum lactate showed significant additional benefit over the remaining values, with an AUC of 0.947 (95% CI 0.92-0.975) and a high sensitivity and specificity for an optimal cut-off value of 2.45 mmol/l. For DSS, the AUC was 0.857 (95% CI 0.808-0.906; cut-off: 0.35), and for AG 0.836 (95% CI 0.783-0.889; cut-off: 12.45 mmol/l). In the case of serum bicarbonate, the AUC was 0.831 (95% CI 0.775-0.886; cut-off: 22.75 mmol/l). In the sex-dependent comparison, the results were similar. Men showed more significant differences in the compared values than women. CONCLUSIONS: Serum lactate is best suited as POCT marker in the differential diagnosis of epileptic and non-epileptic episodes and is superior to AG, DSS and bicarbonate. The differences among sexes may pose a challenge in their implementation and interpretation.