Effect of Sample Storage Temperature and Time Delay on Blood Gases, Bicarbonate and pH in Human Arterial Blood Samples

The stability of blood gases and CO-oximetry under slushed ice and room temperature conditions

OBJECTIVES

Human blood gas stability data is limited to small sample sizes and questionable statistical techniques. We sought to determine the stability of blood gases under room temperature and slushed iced conditions in patients using survival analyses.

METHODS

Whole blood samples from ∼200 patients were stored in plastic syringes and kept at room temperature (22-24 °C) or in slushed ice (0.1-0.2 °C) before analysis. Arterial and venous pO2 (15-150 mmHg), pCO2 (16-72 mmHg), pH (6.73-7.52), and the CO-oximetry panel [total hemoglobin (5.4-19.3 g/dL), percentages of oxyhemoglobin (O2Hb%, 20-99%), carboxyhemoglobin (COHb, 0.1-5.4%) and methemoglobin (MetHb, 0.2-4.6%)], were measured over 5-time points. The Royal College of Pathologists of Australasia's (RCPA's) criteria determined analyte instability. Survival analyses identified storage times at which 5% of the samples for various analytes became unstable.

RESULTS

COHb and MetHb were stable up to 3 h in slushed ice and at room temperature; pCO2, pH was stable at room temperature for about 60 min and 3 h in slushed ice. Slushed ice shortened the storage time before pO2 became unstable (from 40 to 20 min), and the instability increased when baseline pO2 was ≥60 mmHg. The storage time for pO2, pCO2, pH, and CO-oximetry, when measured together, were limited by the pO2.

CONCLUSIONS

When assessing pO2 in plastic syringes, samples kept in slushed ice harm their stability. For simplicity's sake, the data support storage times for blood gas and CO-oximetry panels of up to 40 min at room temperature if following RCPA guidelines.

Impact of storage temperature and time before analysis on electrolytes (Na+, K+, Ca2+), lactate, glucose, blood gases (pH, pO2, pCO2), tHb, O2Hb, COHb and MetHb results

OBJECTIVES

The objective of our study is to evaluate the effect of storage temperature and time to analysis on arterial blood gas parameters in order to extend the CLSI recommendations.

METHODS

Stability of 12 parameters (pH, pCO₂, pO₂, Na+, K+, Ca2+, glucose, lactate, hemoglobin, oxyhemoglobin, carboxyhemoglobin, methemoglobin) measured by GEM PREMIER™ 5000 blood gas analyzer was studied at room temperature and at +4 °C (52 patients). The storage times were 30, 45, 60, 90 and 120 min. Stability was evaluated on the difference from baseline, the difference from the analyte-specific measurement uncertainty applied to the baseline value, and the impact of the variation on the clinical interpretation.

RESULTS

At room temperature, all parameters except the lactate remained stable for at least 60 min. A statistically significant difference was observed for pH at T45 and T60 and for pCO2 at T60 without modification of clinical interpretation. For lactate, clinical interpretation was modified from T45 and values were outside the range of acceptability defined by the measurement uncertainty. All parameters except pO2 remained stable for at least 120 min at +4 °C.

CONCLUSIONS

A one-hour transport at room temperature is compatible with the performance of all the analyses studied except lactate. If the delay exceeds 30 min, the sample should be placed at +4 °C for lactate measurement. If the samples are stored in ice, it is important to note that the pO2 cannot be interpreted.

Effects of time delay and blood storage methods on analysis of canine venous blood samples with an Element point-of-care analyzer

BACKGROUND

Manufacturers of point-of-care (POC) analyzers recommend immediate processing and anaerobic collection of blood samples. However, it is not uncommon for clinical scenarios to result in delayed sample processing or room air exposure that could impact the test results.

OBJECTIVE

To investigate the effect of time delay and sample storage method on key POC analytes in canine venous blood samples processed with an Element POC analyzer.

METHODS

Blood gas analysis was performed on venous blood samples at times 0 (T0), 15, 30, and 60 minutes after sampling using three different storage methods: preheparinized plastic syringes and two different lithium heparin tubes. To determine clinical relevance, results were compared with allowable total error of the respective parameter. Significance was set at P < 0.05.

RESULTS

Significant differences between the three storage methods at baseline were found for partial pressure of carbon dioxide (PCO₂ ), partial pressure of oxygen (PO₂ ), base excess, and total hemoglobin. No significant differences up to T60 were found within collection methods for actual bicarbonate (HCO₃ ^- ), base excess, sodium, potassium, chloride, ionized calcium (iCa), glucose, and BUN. Significant differences within collection methods were found after T0 for creatinine, after 15 minutes for lactate, and after 30 minutes for pH and hematocrit. No significant differences were found for PO₂ in samples stored in preheparinized plastic syringes at any time point.

CONCLUSIONS

These results suggest that HCO₃ ^- , sodium, potassium, chloride, iCa, glucose, and BUN are comparable within the three storage methods for up to 60 minutes after sampling without resulting in clinically relevant changes.

Detection of preanalytical errors in arterial blood gas analysis

Introduction

Blood gas analysis (BGA) is an essential test used for years to provide vital information in critically ill patients. However, the instability of the blood gases is a problem. We aimed to evaluate time and temperature effects on blood gas stability.

Materials and methods

Arterial blood was collected from 20 patients into syringes. Following BGA for baseline, syringes were divided into groups to stand at 4°C and 22°C for 30, 60, 90, 120 minutes. All were tested for pH, partial pressure of carbon dioxide (pCO₂), partial pressure of oxygen (pO₂), oxygen saturation (sO₂), oxyhemoglobin (O₂Hb), sodium, potassium, glucose, lactate, oxygen tension at 50% hemoglobin saturation (p50), and bicarbonate. A subgroup analysis was performed to detect the effect of air on results during storage. Percentage deviations were calculated and compared against the preset quality specifications for allowable total error.

Results

At 4°C, pO₂ was the least stable parameter. At 22°C, pO₂ remained stable for 120 min, pH and glucose for 90 min, lactate and pCO₂ for 60 min. Glucose and lactate were stable when chilled. Air bubbles interfered pO₂ regardless of temperatures, whereas pCO₂ increased significantly at 22°C after 30 min, and pH decreased after 90 min. Bicarbonate, sO₂, O₂Hb, sodium, and potassium were the unaffected parameters.

Conclusions

Correct BGA results are essential, and arterial sample is precious. Therefore, if immediate analysis cannot be performed, up to one hour, syringes stored at room temperature will give reliable results when care is taken to minimize air within the blood gas specimen.

Stability of pH, Blood Gas Partial Pressure, Hemoglobin Oxygen Saturation Fraction, and Lactate Concentration

Background

The storage temperature and time of blood gas samples collected in syringes constitute preanalytical variables that could affect blood gas or lactate concentration measurement results. We analyzed the effect of storage temperature and time delay on arterial or venous blood gas stability related to pH, partial pressure of carbon dioxide (pCO₂) and oxygen (pO₂), hemoglobin oxygen saturation (sO₂), and lactate concentration.

Methods

In total, 1,200 arterial and venous blood sample syringes were analyzed within 10 minutes of collection. The samples were divided into different groups to determine parameter stability at 25, 4–8, and 0–3.9°C and at different storage times, 60, 45, 30, and 15 minutes. Independent sample groups were used for each analysis. Percentage deviations were calculated and compared with acceptance stability limits (1.65× coefficient of variation). Additionally, sample group sub analysis was performed to determine whether stability was concentration-dependent for each parameter.

Results

The pH was stable over all storage times at 4–8 and 0–3.9°C and up to 30 minutes at 25°C. pCO₂ was stable at ≤60 minutes at all temperatures. pO₂ was stable for 45 minutes at 0–3.9°C, and sO₂ was stable for 15 minutes at 25°C and for ≤60 minutes at 0–3.9°C. Lactate concentration was stable for 45 minutes at 0–3.9°C. Subanalysis showed that stability was concentration-dependent.

Conclusions

The strictest storage temperature and time criteria (0–3.9°C, 45 minutes) should be adopted for measuring pH, pCO₂, pO₂, sO₂, and lactate concentration in blood gas syringes.

Extended recording of LMA in rats: Effects of IV catheters, "comfort jackets" and chamber lids on arterial blood gas parameters

The standard infrared photobeam locomotor activity system has been used extensively in neurobiology and neuropharmacology to study the functional impact of direct manipulations of the nervous system. There is interest in using the activity monitors to assess the early stages of drug withdrawal in rodents. In a standard twice-daily dosing strategy animals would be dosed at 6:00 am and 5:00 pm for 15 to 30 days. There is interest in using the chambers to assess the early stages of the discontinuation syndrome. Placement of the rodents into the chambers following the scheduled sham or vehicle last dose of a 15- to 30-day subchronic dosing regimen (b.i.d., t.i.d., etc.) and monitoring overnight allows for a quantitative measure of the initial physiological homeostatic acclimation period during the lights-out period. By using the chambers there is no circadian dysrhythmia induced as an experimental confound and objectively verifiable data is generated during the period expected to correspond with the plasma drug levels approaching zero and the onset of discontinuation syndrome. We demonstrated that untreated "normal" rats showed a normal decelerating time-effect curve over the 12-hour monitoring period that was not compromised by restricted access to food and water. Arterial blood gas monitoring before and after 12 h of night-time activity chamber monitoring clearly demonstrated normal respiratory function with no clinical signs of any blood gas-based diagnosis of metabolic dysfunction.

The role of the clinical laboratory in diagnosing acid-base disorders

Acid-base homeostasis is fundamental for life. The body is exceptionally sensitive to changes in pH, and as a result, potent mechanisms exist to regulate the body's acid-base balance to maintain it in a very narrow range. Accurate and timely interpretation of an acid-base disorder can be lifesaving but establishing a correct diagnosis may be challenging. The underlying cause of the acid-base disorder is generally responsible for a patient's signs and symptoms, but laboratory results and their integration into the clinical picture is crucial. Important acid-base parameters are often available within minutes in the acute hospital care setting, and with basic knowledge it should be easy to establish the diagnosis with a stepwise approach. Unfortunately, many caveats exist, beginning in the pre-analytical phase. In the post-analytical phase, studies on the arterial reference pH are scarce and therefore many different reference values are used in the literature without any solid evidence. The prediction models that are currently used to assess the acid-base status are approximations that are mostly based on older studies with several limitations. The two most commonly used methods are the physiological method and the base excess method, both easy to use. The secondary response equations in the base excess method are the most convenient. Evaluation of acid-base disorders should always include the assessment of electrolytes and the anion gap. A major limitation of the current acid-base laboratory tests available is the lack of rapid point-of-care laboratory tests to diagnose intoxications with toxic alcohols. These intoxications can be fatal if not recognized and treated within minutes to hours. The surrogate use of the osmolal gap is often an inadequate substitute in this respect. This article reviews the role of the clinical laboratory to evaluate acid-base disorders.

Effects of time delay and body temperature on measurements of central venous oxygen saturation, venous-arterial blood carbon dioxide partial pressures difference, venous-arterial blood carbon dioxide partial pressures difference/arterial-venous oxygen difference ratio and lactate

BACKGROUND

Central venous oxygen saturation (ScvO₂), venous-arterial blood carbon dioxide partial pressures difference (Pv-aCO₂), venous-arterial blood carbon dioxide partial pressures difference/arterial-venous oxygen difference ratio (Pv-aCO₂/Ca-vO₂) and lactate are important parameters employed during shock resuscitation. We designed this study to confirm the effects of time delay and body temperature on measurements of these four parameters.

METHODS

Arterial and central venous blood samples were simultaneously drawn by plastic syringes via indwelling intra-arterial and central venous catheters from critically ill patients. Blood gas analyses were performed on both samples and repeated after 10, 20, 30, 40, 50 and 60 min. Patients were divided into a control group and a high temperature group according to whether the body temperature was greater than 38 °C.

RESULTS

A total of 30 critically ill patients were enrolled. There was a trend of increasing values for ScvO₂, Pv-aCO₂, Pv-aCO₂/Ca-vO₂ and lactate over time (P < 0.001). The ScvO₂ differences were all lower in high temperature group after 10, 20, 30, 40, 50 and 60 min when compared to the corresponding differences in the control group (P < 0.05). The differences in lactate values were slightly higher in the high temperature group, relative to the control group after 20, 30, 40, 50 and 60 min (P < 0.05).

CONCLUSIONS

Measurements of ScvO₂, Pv-aCO₂, lactate and Pv-aCO₂/Ca-vO₂ were affected by time delay or body temperature. We recommend that arterial and central venous blood gas samples be analyzed quickly within 10 min, especially for patients with body temperature <38 °C.

TRIAL REGISTRATION

ChiCTR, ChiCTR1800014484 . Registered 16 January 2018.

Prognostic value of on admission arterial PCO2 in hospitalized patients with community-acquired pneumonia

BACKGROUND

There is little data about the correlation between the outcome of community acquired pneumonia (CAP) and the hypercapnic type respiratory failure. In this study we prospectively investigated the prognostic significance of first arterial CO₂ tension in patients hospitalized with CAP.

METHODS

In this prospective study patients with CAP, admitted to a general hospital were included. PaCO₂ was measured for each subject in an arterial blood sample drawn in the first 2 hours and its correlations with three major outcomes were evaluated: intensive care unit (ICU) admission, duration of admission and mortality in 30 days.

RESULTS

A total of 114 patients (mean age: 60.9±18.3; male: 51.8%) diagnosed with CAP were included. Significant relationship was not found between PaCO₂ and mortality (P=0.544) or ICU admission (P=0.863). However advanced age, associated CHF, high BUN levels, high CURB-65 scores, associated pleural effusion in chest X-ray and being admitted to the ICU (P=0.012, 0.004, 0.003, <0.001, 0.045 and <0.001 respectively) were all significant prognostic factors of higher mortality risks. Prognostic factors for ICU admission were a history of malignancy (P=0.004), higher CURB-65 (P<0.001) scores and concomitant pleural effusion (P=0.028) in chest X-ray. Hypercapnic patients hospitalized for longer duration compared with normocapnic subjects. Furthermore, patients with lower pH (P=0.041) and pleural effusions (P=0.002) were hospitalized longer than the others.

CONCLUSIONS

There was less prominent prognostic value regarding on-admission PaCO₂ in comparison to other factors such as CURB-65. Considering the inconsistent results of surveys conducted on prognostic value of PaCO₂ for CAP outcomes, further investigations are required to reach a consensus on this matter.