The usefulness of peripheral venous blood in estimating acid-base status in acutely ill patients

Cephalic and saphenous venous blood collected by continuous heating of the paws compared with arterial blood for measurement of blood gas values in well-perfused dogs

BACKGROUND

"Arterialization" of the dorsal hand vein is well-established in human medicine, but not in veterinary medicine.

OBJECTIVES

To compare cephalic and saphenous venous blood collected by continuously heating the paws to 37°C ("arterialization"), with arterial blood (AB) for measurement of blood gas variables in well-perfused dogs.

ANIMALS

Eight healthy dogs.

METHODS

Experimental study. Fore and hind paws were continuously heated to 37°C to "arterialize" cephalic and saphenous venous blood. AB and "arterialized" cephalic and saphenous venous blood (ACV and ASV, respectively) were simultaneously collected from lightly anesthetized dogs with induced metabolic and respiratory acid-base disorders. The pH, partial pressures of carbon dioxide (PCO2 ) and oxygen (PO2 ), bicarbonate concentration [HCO3 - ], and base excess (BE) were measured once in each state. Systolic blood pressure was maintained above 100 mm Hg. The AB, ACV, and ASV values were compared.

RESULTS

The pH, [HCO3 - ], and BE values had no significant difference and good agreement, the PCO2 values had a strong correlation (correlation coefficient of .91-1.00), and the PO2 values had a significant difference (P < .01) and poor agreement between AB and ACV, and between AB and ASV. The PCO2 values of ASV overestimated those of AB by ~3.0 mm Hg, which was considered within clinically allowable limits, while those of ACV were not within clinically allowable limits.

CONCLUSIONS AND CLINICAL IMPORTANCE

Under experimental conditions, the ASV samples were more identical to the AB samples than the ACV samples for pH, PCO2 , [HCO3 - ], and BE values in well-perfused dogs. The saphenous vein is suitable for "arterialization."

Correlation of Arterial and Venous pH and Bicarbonate in Patients With Renal Failure

Background and objective

Blood gas analysis plays a pivotal role in the management of various respiratory and metabolic disorders. Both arterial and venous samples can be used for blood gas analysis. Arterial blood sampling is technically difficult and is associated with more complications as compared to venous sampling. Many studies have shown the correlation of arterial and venous pH and bicarbonate levels in sepsis, diabetic ketoacidosis (DKA), chronic obstructive pulmonary disease (COPD), and circulatory failure. But, there is a paucity of data, pertaining specifically to the correlation of arterial blood gas (ABG) analysis and venous blood gas (VBG) analysis in patients with renal failure. The objective of this study was to look for any possible correlation between arterial and venous pH and bicarbonate values in patients with renal failure.

Methods

This cross-sectional study was carried out at a large tertiary care hospital in Rawalpindi, Pakistan. Over a period of eight months, 101 patients with renal failure were enrolled after obtaining informed consent. Arterial and venous samples from the patients were obtained, analyzed, and compared.

Results

Out of the total 101 patients, 53 (52.5%) were male while 48 (47.5%) were female. The mean age of the patients was 46.23 ±15.54 years. Mean arterial pH and venous pH were 7.35 and 7.28 respectively. The Pearson correlation coefficient between arterial and venous pH was found to be 0.857 (p<0.001). The mean arterial and venous bicarbonate values were 14.47 mEq/L and 15.51 mEq/L respectively. And the Pearson correlation coefficient between arterial and venous bicarbonate was found to be 0.842 (p<0.001). 

Conclusion

Venous pH and bicarbonate levels correlate strongly with arterial pH and bicarbonate levels, respectively, in patients with renal failure.

Reference intervals for venous blood gas measurement in adults

OBJECTIVES

Venous blood gas (VBG) analysis is becoming a popular alternative to arterial blood gas (ABG) analysis due to reduced risk of complications at phlebotomy and ease of draw. In lack of published data, this study aimed to establish reference intervals (RI) for correct interpretation of VBG results.

METHODS

One hundred and 51 adult volunteers (101 females, 50 males, 18-70 years) were enrolled after completion of a health questionnaire. Venous blood was drawn into safePICO syringes and analysed on ABL827 blood gas analyser (Radiometer Pacific Pty. Ltd.). A non-parametric approach was used to directly establish the VBG RI which was compared to a calculated VBG RI based on a meta-analysis of differences between ABG and VBG.

RESULTS

After exclusions, 134 results were used to derive VBG RI: pH 7.30-7.43, partial pressure of carbon dioxide (pCO₂) 38-58 mmHg, partial pressure of oxygen (pO₂) 19-65 mmHg, bicarbonate (HCO₃-) 22-30 mmol/L, sodium 135-143 mmol/L, potassium 3.6-4.5 mmol/L, chloride 101-110 mmol/L, ionised calcium 1.14-1.29 mmol/L, lactate 0.4-2.2 mmol/L, base excess (BE) -1.9-4.5 mmol/L, saturated oxygen (sO₂) 23-93%, carboxyhaemoglobin 0.4-1.4% and methaemoglobin 0.3-0.9%. The meta-analysis revealed differences between ABG and VBG for pH, HCO₃-, pCO₂ and pO₂ of 0.032, -1.0 mmol/L, -4.2 and 39.9 mmHg, respectively. Using this data along with established ABG RI, calculated VBG RI of pH 7.32-7.42, HCO₃- 23 - 27 mmol/L, pCO₂ 36-49 mmHg (female), pCO₂ 39-52 mmHg (male) and pO₂ 43-68 mmHg were formulated and compared to the VBG RI of this study.

CONCLUSIONS

An adult reference interval has been established to assist interpretation of VBG results.

Acidemia Detected on Venous Blood Gas After Out-of-Hospital Cardiac Arrest Predicts Likelihood to Survive to Hospital Discharge

BACKGROUND

Sudden cardiac arrest is the most common cause of death worldwide, and prognostication after survival remains challenging. Decisions regarding prognosis can be fraught with error in the immediate postarrest period, with guidelines recommending the use of various tests, including blood gas pH, to determine which interventions to perform. Despite these recommendations, the prognostic utility of blood gas pH remains unclear.

OBJECTIVES

In this retrospective cohort study, we aimed to demonstrate the prognostic utility of emergency department blood gas pH after return of spontaneous circulation (ROSC) in out-of-hospital cardiac arrest.

METHODS

A retrospective cohort study was performed, including all adult survivors of out-of-hospital cardiac arrest (n = 79). Primary disease-oriented outcome was venous blood pH after ROSC and survival to hospital discharge.

RESULTS

In patients with out-of-hospital cardiac arrest, pH < 7.2 was associated with decreased likelihood of survival to hospital discharge (odds ratio 0.06), with every 0.1-unit increase in pH being associated with an increased likelihood of survival (1.98). Based on the area under the receiver curve, the pH that optimizes sensitivity and specificity for predicting survival was 7.04.

CONCLUSION

Both presence and degree of acidemia on initial blood gas after ROSC was associated with a decreased likelihood of survival to hospital discharge. The optimal cutoff for prediction in this cohort of patients was 7.04. Using a higher pH cutoff would result in fewer patients receiving intervention that would otherwise have survived.

Can peripheral venous blood gases replace arterial blood gases in emergency department patients?

Objective:

To determine if peripheral venous blood gas values for pH, partial pressure of carbon dioxide (PCO2) and the resultant calculated bicarbonate (HCO3) predict arterial values accurately enough to replace them in a clinical setting.

Methods:

This prospective observational study was performed in a university tertiary care emergency department from June to December 1998. Patients requiring arterial blood gas analysis were enrolled and underwent simultaneous venous blood gas sampling. The following data were prospectively recorded: age, sex, presenting complaint, vital signs, oxygen saturation, sample times, number of attempts and indication for testing. Correlation coefficients and mean differences with 95% confidence intervals (CIs) were calculated for pH,PCO2and HCO3. A survey of 45 academic emergency physicians was performed to determine the minimal clinically important difference for each variable.

Results:

The 218 subjects ranged in age from 15 to 90 (mean 60.4) years. The 2 blood samples were drawn within 10 minutes of each other for 205 (96%) of the 214 patients for whom data on timing were available. Pearson’s product–moment correlation coefficients between arterial and venous values were as follows: pH, 0.913;PCO2, 0.921; and HCO3, 0.953. The mean differences (and 95% CIs) between arterial and venous samples were as follows: pH, 0.036 (0.030–0.042);PCO2, 6.0 (5.0–7.0) mm Hg; and HCO3, 1.5 (1.3–1.7) mEq/L. The mean differences (± 2 standard deviations) were greater than the minimum clinically important differences identified in the survey.

Conclusions:

Arterial and venous blood gas samples were strongly correlated, and there were only small differences between them. A survey of emergency physicians suggested that the differences are too large to allow for interchangeability of results; however, venous values may be valid if used in conjunction with a correction factor or for trending purposes.

Transcutaneous PCO2 monitoring in infants hospitalized with viral bronchiolitis

Our objective was to assess within a feasibility study the correlation and agreement of transcutaneous carbon dioxide (PtcCO2) monitoring with venous carbon dioxide (PvCO2) in infants with bronchiolitis in the emergency room (ER) and pediatric department. Sixty infants (aged 3.6 ± 3.3 months) admitted to our ER with bronchiolitis were included. PtcCO2 measurements (SenTec Digital Monitoring System) collected prospectively were compared with simultaneous PvCO2 drawn for patient care. Analysis included 100 measurements. The correlation of PtcCO2 and PvCO2 (r = 0.71, p < 0.001) was good, and the agreement (mean difference ± standard deviation of the differences 1.9 ± 7.0 mmHg) was adequate; average PtcCO2 was slightly lower than PvCO2. Changes in PtcCO2 and PvCO2 for consecutive measurements within each patient correlated (r = 0.41, p < 0.01). The level of PtcCO2 correlated with disease severity clinical score (p < 0.001).

CONCLUSIONS

PtcCO2 monitoring was feasible in the ER and pediatric department and was found to have a good correlation and adequate agreement with PvCO2 in infants with bronchiolitis. Because the standard deviation of the differences was relatively high, though comparable to the literature, we suggest that PtcCO2 should not replace blood gas but rather serve as a complementary tool for trending and for real-time continuous assessment of the CO2 levels.

Peripheral venous blood gases and pulse-oximetry in acute cardiogenic pulmonary oedema

BACKGROUND

The role of venous blood gases as an alternative to arterial blood gases in patients with severe acute heart failure has not been established.

OBJECTIVE

To assess the correlation between arterial and peripheral venous blood gases together with pulse-oximetry (SpO2), as well as to estimate arterial values from venous samples in the first hours upon admission of patients with acute cardiogenic pulmonary oedema.

METHODS

Simultaneous venous and arterial blood samples were extracted on admission and over the next 1, 2, 3, 4, and 10 hours. SpO2 was also registered at the same intervals.

RESULTS

A total of 178 pairs of samples were obtained from 34 consecutive patients with acute cardiogenic pulmonary oedema. Arterial and venous blood gases followed a parallel course in the first hours, showing high correlation rates at all time intervals. Venous samples underestimated pH (mean difference -0.028) and overestimated CO2 (+5.1 mmHg) and bicarbonate (+1 mEq/l). Conversely, SpO2 tended to underestimate SaO2 (mean±SD: 93.1±9.1 vs. 94.2±8.4). Applying simple mathematical formulae based on these differences, arterial values were empirically calculated from venous samples, showing acceptable agreement in the Bland-Altman test. Likewise, a venous pH <7.32, pCO2 >51.3 mmHg, and bicarbonate <22.8 mEq/l could fairly identify arterial acidosis, either respiratory or metabolic, with a test accuracy of 92, 68, and 91%, respectively.

CONCLUSIONS

In patients with cardiogenic pulmonary oedema, arterial blood gas disturbances may be estimated from peripheral venous samples. By monitoring SpO2 simultaneously, arterial punctures could often be avoided.

Clinicopathologic analysis of Passeriform venous blood reflects transitions in elevation and habitat

Jugular blood samples from 110 Passeriformes collected at several Texas locations were analyzed for multiple clinicopathologic parameters between April 2010 and August 2011. Electrolyte, blood gas, and select erythrocyte parameters were analyzed on site with a point of care analyzer, and gender, age, body condition score, location, and species were recorded. Many analytes exhibited a Gaussian distribution across species and are reported as a single range. Taxon affected electrolyte and red blood cell parameters, but not most blood gas or acid base variables. Migratory status affected select electrolytes but few blood gas variables. Red blood cell parameters were affected the most by variables of age, taxonomic group, and gender, but not migratory life history. We found significant changes in glucose and numerous acid base analytes in birds sampled from habitats with evolutionarily recent ecologic degradation. We advocate the use of these analytes, particularly venous blood gas values, as determined by a point of care analyzer, as reasonable biomarkers for determination of Passeriform population health, but also recommend that red blood cell parameters and electrolyte concentrations be controlled for age, species, and gender in future studies. Further, based on our investigation, venous blood gas values and acid base balance in Passeriformes can assess the health of an ecosystem.

Prospective correlation of arterial vs venous blood gas measurements in trauma patients

OBJECTIVE

The objective of this study is to assess if venous blood gas (VBG) results (pH and base excess [BE]) are numerically similar to arterial blood gas (ABG) in acutely ill trauma patients.

METHODS

We prospectively correlated paired ABG and VBG results (pH and BE) in adult trauma patients when ABG was clinically indicated. A priori consensus threshold of clinical equivalence was set at ± less than 0.05 pH units and ± less than 2 BE units. We hypothesized that ABG results could be predicted by VBG results using a regression equation, derived from 173 patients, and validated on 173 separate patients.

RESULTS

We analyzed 346 patients and found mean arterial pH of 7.39 and mean venous pH of 7.35 in the derivation set. Seventy-two percent of the paired sample pH values fell within the predefined consensus equivalence threshold of ± less than 0.05 pH units, whereas the 95% limits of agreement (LOAs) were twice as wide, at -0.10 to 0.11 pH units. Mean arterial BE was -2.2 and venous BE was -1.9. Eighty percent of the paired BE values fell within the predefined ± less than 2 BE units, whereas the 95% LOA were again more than twice as wide, at -4.4 to 3.9 BE units. Correlations between ABG and VBG were strong, at r(2) = 0.70 for pH and 0.75 for BE.

CONCLUSION

Although VBG results do correlate well with ABG results, only 72% to 80% of paired samples are clinically equivalent, and the 95% LOAs are unacceptably wide. Therefore, ABG samples should be obtained in acutely ill trauma patients if accurate acid-base status is required.

Base deficit from the first peripheral venous sample: a surrogate for arterial base deficit in the trauma bay

BACKGROUND

Arterial base deficit (ABD) measurement is a standard test for assessment of the trauma patient's metabolic response to shock. Venous blood is readily available earlier during the trauma resuscitation. The aim of this study is to analyze the difference (correlation, agreement, clinical significance) between the first peripheral venous base deficit (pVBD) and the first ABD during trauma resuscitation.

METHODS

Consecutive trauma patients >18 years presenting to John Hunter Hospital (JHH), Newcastle, Australia, from January 2007 until July 2007 requiring arterial blood gas sampling had a peripheral venous blood gas performed simultaneously. A survey of JHH trauma clinicians and members of the American Association for the Surgery of Trauma was performed to determine a clinically relevant difference between two serial base deficit measurements. Pearson correlation and Bland-Altman tests were performed.

RESULTS

During the 7-month period, 127 patients (79% men, mean age, 46.3 [±18.4 years] and median injury severity score of 15 [interquartile range, 8-23; range, 1-75]) were included into the study. The average peripheral ABD (pABD) and pVBD were -2.2 mmol/L±3.8 mmol/L and -1.3 mmol/L±3.8 mmol/L, respectively. The average difference between measurements was 0.9 (range, -1.7 to +3.5; 95% confidence interval, 0.7-1.0) with pVBD>pABD. The Pearson test showed highly significant correlation (r=0.97, p<0.0001). The survey of 11 JHH and 56 American Association for the Surgery of Trauma clinicians determined 2 mmol/L as clinically relevant difference between two base deficit measurements. All individual paired sample's difference sat within the clinically relevant limits and>95% (121 of 127) of samples sat within the 1.96 standard deviation acceptable by the Bland-Altman plot.

CONCLUSION

There is near perfect correlation and clinically acceptable agreement between pABD and pVBD values on simultaneous testing. pVBD is an acceptable test to assess trauma patients' initial metabolic status when occult blood loss suspected.

Comparison and agreement between venous and arterial gas analysis in cardiopulmonary patients in Kashmir valley of the Indian subcontinent

BACKGROUND

Arterial blood gas (ABG) analysis is routinely performed for sick patients but is fraught with complications, is painful, and is technically demanding.

OBJECTIVE

To ascertain agreement between the arterial and peripheral venous measurement of pH, pCO(2), pO(2), and bicarbonate levels in sick patients with cardiopulmonary disorders in the valley of Kashmir in the Indian subcontinent, so as to use venous gas analysis instead of arterial for assessment of patients.

SETTING

Sher-i-Kashmir Institute of Medical Sciences, Srinagar, Kashmir, a 650-bedded tertiary care hospital in North India located at an altitude of 1584 m.

METHODS

One hundred patients who required ABG analysis were admitted. Peripheral venous blood was drawn within 5 min of an ABG measurement, and the samples analyzed immediately on a point of care automated ABG analyzer. Finger pulse oximetry was used to obtain oxygen (SpO(2)) saturation. Data were analyzed using Pearson correlation and bias (Bland Altman) methods.

RESULTS

The venous measurements of pH, pCO(2), pO(2) and bicarbonate, and the digital oxygen saturation were highly correlated with their corresponding arterial measurements. Bland Altman plots demonstrated a high degree of agreement between the two corresponding sets of measurements with clinically acceptable differences. The difference in pO(2) measurements was, however, higher (-22.34 ± 15.23) although the arterial saturation and finger oximetry revealed a good degree of agreement with clinically acceptable bias.

CONCLUSION

Peripheral venous blood gas assessment in conjunction with finger pulse oximetry can obviate the routine use of arterial puncture in patients requiring ABG analysis.

Prediction of arterial blood gas values from arterialized earlobe blood gas values in patients treated with mechanical ventilation

Background/Objective:

Arterial blood gas (ABG) analysis is useful in evaluation of the clinical condition of critically ill patients; however, arterial puncture or insertion of an arterial catheter may sometimes be difficult and cause many complications. Arterialized ear lobe blood samples have been described as adequate to gauge gas exchange in acute and chronically ill pediatric patients.

Purpose:

This study evaluates whether pH, partial pressure of oxygen (PO₂), partial pressure of carbon dioxide (PCO₂), base excess (BE), and bicarbonate (HCO₃) values of arterialized earlobe blood samples could accurately predict their arterial blood gas analogs for adult patients treated by mechanical ventilation in an intensive care unit (ICU).

Setting:

A prospective descriptive study

Methods:

Sixty-seven patients who were admitted to ICU and treated with mechanical ventilation were included in this study. Blood samples were drawn simultaneously from the radial artery and arterialized earlobe of each patient.

Results:

Regression equations and mean percentage-difference equations were derived to predict arterial pH, PCO₂, PO₂, BE, and HCO₃-values from their earlobe analogs. pH, PCO₂, BE, and HCO₃ all significantly correlated in ABG and earlobe values. In spite of a highly significant correlation, the limits of agreement between the two methods were wide for PO₂. Regression equations for prediction of pH, PCO₂, BE, and HCO3- values were: arterial pH (pHa) = 1.81+ 0.76 × earlobe pH (pHe) [r = 0.791, P < 0.001]; PaCO₂ = 1.224+ 1.058 × earlobePCO₂ (PeCO₂) [r = 0.956, P < 0.001]; arterial BE (BEa) = 1.14+ 0.95 × earlobe BE (BEe) [r= 0.894, P < 0.001], and arterial HCO₃- (HCO₃-a) = 1.41+ earlobe HCO₃(HCO₃-e) [r = 0.874, P < 0.001]. The predicted ABG values from the mean percentage-difference equations were derived as follows: pHa = pHe × 1.001; PaCO₂ = PeCO₂ × 0.33; BEa = BEe × 0.57; and HCO₃-a = HCO₃-e × 1.06.

Conclusions:

Arterialized earlobe blood gas can accurately predict the ABG values of pH, PCO₂, BE, and HCO₃- for patients who do not require regular continuous blood pressure measurements and close monitoring of arterial PO₂ measurements.

The Accuracy of the Central Venous Blood Gas for Acid-Base Monitoring

Background: Routine use of central venous blood gases (VBGs) may reduce complications from prolonged arterial cannulation. We investigated the reliability of the VBG as a substitute for arterial blood gas (ABG) in multiple care settings. Methods: We developed a VBG adjustment rule of ABG pH = VBG pH + 0.05, ABG CO2 = VBG PCO2 -5 mm Hg from prior studies and validated this relationship with simultaneous venous and arterial blood obtained from 187 medical/surgical intensive care, cardiac catheterization laboratory, and coronary care unit patients with central venous access. Results: The overall accuracy of a normal adjusted VBG (aVBG) to predict a normal ABG was 90%. After adjustment, the mean systematic difference (bias) between ABG and VBG pH decreased from 0.035 ± 0.02 to -0.015 ± 0.02 and PCO2 bias decreased from -4.5 ± 3.5 to 0.5 ± 3.5. Intraclass correlation coefficients for agreement improved after applying the adjustment rule to venous pH (from 0.84 to 0.93, P < .001) and PCO2 (from 0.66 to 0.84, P < .001). Overall diagnostic accuracy of VBG improved from 45% to 74% after adjustment. Multiple logistic regression demonstrated that the factor independently associated with discrepancy between VBG and ABG diagnoses was an abnormal aVBG (OR 6.8, 95% CI 2.8-16.5). Conclusions: Because of the high agreement between a normal aVBG with a normal ABG and the small bias between these tests, we recommend use of the adjusted central VBG.

Prediction of arterial blood gas values from venous blood gas values in patients with acute exacerbation of chronic obstructive pulmonary disease

Arterial blood gas (ABG) analysis has an important role in the clinical assessment of patients with acute exacerbation of chronic obstructive pulmonary disease (AECOPD). However, arterial puncture or insertion of an arterial catheter has many drawbacks. The aim of this study was to evaluate whether venous blood gas (VBG) values of pH, partial pressure of carbon dioxide (PCO(2)) and oxygen (PO(2)), bicarbonate (HCO(3)), and oxygen saturation (SO(2)) can reliably predict ABG levels in patients with AECOPD. One hundred and thirty-two patients with a prior diagnosis of COPD presenting with acute exacerbation according to AECOPD criteria were included in this prospective study. AECOPD is defined as a recent increase in cough, wheezing, the volume and purulence of sputum or shortness of breath necessitating a change in regular medication, including corticosteroids or antibiotics. ABG samples were taken immediately after venous sampling, and both were analyzed. Linear regression analysis was performed and equations were established for the estimation of arterial values. The Pearson correlation coefficients for pH, PCO(2), HCO(3), PO(2), and SO(2) were 0.934, 0.908, 0.927, 0.252, and 0.296, respectively. There was a significant correlation between ABG and VBG values of pH, PCO(2), and HCO(3) (p < 0.001). Linear regression equations for the estimation of pH, PCO(2), and HCO(3) were as follows: arterial pH = 1.004 x venous pH; arterial PCO(2) = 0.873 x venous PCO(2); and arterial HCO(3) = 0.951 x venous HCO(3). VBG analysis can reliably predict the ABG values of pH, PCO(2) and HCO(3) in patients with AECOPD.

A method for calculation of arterial acid-base and blood gas status from measurements in the peripheral venous blood

In non-emergency medical departments such as internal medicine sampling of arterial blood and analysis for acid-base status is not routinely performed. Peripheral venous blood is routinely taken but interpretation of its acid-base status is difficult. This paper presents a method for calculation of arterial acid-base and blood gas status from measurements in peripheral venous blood combined with a pulse oximeter measurement of arterial saturation. The use of the method has been illustrated using the data of three patients with different acid-base, haemodynamic, and metabolic conditions. The sensitivity of the method has been tested for measurement errors including venous blood acid-base and blood gas status and pulse oximetry; errors due to physiological assumptions including the values of RQ and strong acid production at the tissues; and errors due to air bubbles in the blood. Errors due to these effects are relatively insignificant except for errors in calculated arterial PO(2), particularly when SpO(2) is greater than 97%; and errors when the change in base excess across the sampling site due to strong acid production is greater that 1.3 mmol/l.

Identifying the sick: can biochemical measurements be used to aid decision making on presentation to the accident and emergency department

BACKGROUND

Early and accurate identification of patients who may benefit from aggressive optimal medical intervention is essential if improved outcomes in terms of survival are to be achieved. We studied the usefulness of routine clinical measurements and/or markers of metabolic abnormality in the early identification of those patients at greatest risk of deterioration on presentation to the accident and emergency department.

METHODS

We conducted a prospective observational study in the accident and emergency department of a 602-bed district general hospital. Routine clinical measurements (heart rate, systolic blood pressure, temperature, oxygen saturation in room air, level of consciousness and ventilatory frequency) and venous blood analysis for metabolic markers (pH, bicarbonate, standard base excess, lactate, anion gap, strong ion difference, and strong ion gap) and biochemical markers (Na+, K+, Ca2+, Cl-, PO4- albumin, urea and creatinine) were recorded from unselected consecutive hospital admissions over two 3-month periods (September-November 2002 and February-April 2003).

RESULTS

Logistic regression analysis showed that neither conventional clinical measurements upon presentation to the accident and emergency department nor venous biochemical and metabolic indices have good discriminatory ability when used as single predictors of either hospital mortality or length of hospital stay. Selecting variables from all the clinical and venous blood measurements gave a parsimonious model containing only age, heart rate, phosphate and albumin (area under the receiver operating characteristic curve, 0.82 [95% CI 0.76, 0.87]).

CONCLUSIONS

A combination of clinical and venous biochemical measurements in the accident and emergency department proved the best predictors of hospital mortality. Consequently, they may be helpful as a triage tool in the accident and emergency department to help identify patients at risk of deterioration.

Correlation of simultaneously obtained capillary, venous, and arterial blood gases of patients in a paediatric intensive care unit

AIMS

To investigate the correlation of pH, partial pressure of oxygen (PO2), partial pressure of carbon dioxide (PCO2), base excess (BE), and bicarbonate (HCO3) between arterial (ABG), venous (VBG), and capillary (CBG) blood gases.

METHODS

Patients admitted to the paediatric intensive care unit (PICU) in Cukurova University between August 2000 and February 2002 were enrolled.

RESULTS

A total of 116 simultaneous venous, arterial, and capillary blood samples were obtained from 116 patients (mean age 56.91 months, range 15 days to 160 months). Eight (7%) were neonates. Sixty six (57%) were males. pH, PCO2, BE, and HCO3 were all significantly correlated in ABG, VBG, and CBG. Correlation in PO2 was also significant, but less so. Correlation between pH, PCO2, PO2, BE, and HCO3 was similar in the presence of hypothermia, hyperthermia, and prolonged capillary refilling time. In hypotension, correlation in PO2 between VBG and CBG was similar but disappeared in ABG-VBG and ABG-CBG.

CONCLUSIONS

There is a significant correlation in pH, PCO2, PO2, BE, and HCO3 among ABG, VBG, and CBG values, except for a poor correlation in PO2 in the presence of hypotension. Capillary and venous blood gas measurements may be useful alternatives to arterial samples for patients who do not require regular continuous blood pressure recordings and close monitoring of PaO2. We do not recommend CBG and VBG for determining PO2 of ABG.

An evidence-based evaluation of the use of sodium bicarbonate during cardiopulmonary resuscitation

The use of bicarbonate is rooted in three decades of clinical experience and observational studies. For many years, bicarbonate passed the tried and true test for clinical therapies; however, administration of sodium bicarbonate during cardiac arrest and hypoxic acidosis has become increasingly controversial. The controversy provides an excellent opportunity to evaluate the impact an evidence-based approach might have on a common clinical practice. Is bicarbonate efficacious in the treatment of the severe acidosis that accompanies cardiac arrest during cardiopulmonary resuscitation (CPR)? Are the deleterious effects of bicarbonate clinically relevant? What is the evidence upon which a rational decision may be based? This review evaluates and ranks the evidence supporting the use of sodium bicarbonate in the therapy of acidosis associated with cardiac arrest during CPR.

Sodium bicarbonate in cardiac arrest: a reappraisal

The routine use of sodium bicarbonate in patients with cardiac arrest has been discouraged, with the benefit of outcome evaluation. Current recommendations include an elaborate stratification of circumstances in which bicarbonate is to be used. The physiological and clinical aspects of bicarbonate administration during cardiopulmonary resuscitation in animal and human studies were reviewed. The onset of significant acidemia or alkalemia is associated with adverse system specific effects. The administration of bicarbonate may mitigate the adverse physiological effects of acidemia, improve response to exogenously administered vasopressor agents, or simply increase venous return due to an osmolar effect, resulting in increased coronary perfusion pressure. Likewise, bicarbonate may have adverse effects in each of these areas. The preponderance of evidence suggests that bicarbonate is not detrimental and may be helpful to outcome from cardiac arrest. An objective reappraisal of the empirical use of bicarbonate or other buffer agents in the appropriate "therapeutic window" for cardiac patients may be warranted.