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 r² = 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.     

Can mainstream end-tidal carbon dioxide measurement accurately predict the arterial carbon dioxide level of patients with acute dyspnea in ED

Objective

This study was designed to determine whether the mainstream end-tidal carbon dioxide (ETCO₂) measurement can accurately predict the partial arterial carbon dioxide (Paco₂) level of patients presented to emergency department (ED) with acute dyspnea.

Methods

This prospective, observational study was conducted at a university hospital ED, which serves more than 110?000 patients annually. Nonintubated adult patients presented with acute dyspnea who required arterial blood gas analysis were recruited in the study for a 6-month period between January and July 2010. Patients were asked to breathe through an airway adapter attached to the mainstream capnometer. Arterial blood gas samples were obtained simultaneously.

Results

We included 162 patients during the study period. The mean ETCO₂ level was 39.47 ± 10.84 mm Hg (minimum, 19 mm Hg; maximum, 82 mm Hg), and mean Paco₂ level was 38.95 ± 12.27 mm Hg (minimum, 16 mm Hg; maximum, 94 mm Hg). There was a positive, strong, statistically significant correlation between ETCO₂ and Paco₂ (r = 0.911, P < .001). The Bland-Altman plot shows the mean bias ± SD between ETCO₂ and Paco₂ as 0.5 ± 5 mm Hg (95% confidence interval, −1.3165-0.2680) and the limits of agreement as −10.5 and +9.5 mm Hg. Eighty percent (n = 129) of the ETCO₂ measurements were between the range of ±5 mm Hg.

Conclusion

Mainstream ETCO₂ measurement accurately predicts the arterial Paco₂ of patients presented to ED with acute dyspnea. Further studies comparing mainstream and sidestream methods in these patients are required.     

Concordance between transcutaneous and arterial measurements of carbon dioxide in an ED

Background

Transcutaneous carbon dioxide pressure (PtcCO₂) has been suggested as a noninvasive surrogate of arterial carbon dioxide pressure (PaCO₂). Our study evaluates the reliability of this method in spontaneously breathing patients in an emergency department.

Patients and methods

A prospective, observational study was performed in nonintubated dyspneic patients who required measurement of arterial blood gases. Simultaneously and blindly to the physicians in charge, PtcCO₂ was measured using a TOSCA 500 monitor (Radiometer, Villeurbanne, France). Agreement between PaCO₂ and PtcCO₂ was assessed using the Bland-Altman method.

Results

Forty-eight patients (mean age, 65 years) were included, and 50 measurements were done. Eleven (23%) had acute heart failure; 10 (21%), pneumonia; 7 (15%), acute asthma; and 7 (15%), exacerbation of chronic obstructive pulmonary disease. Median PaCO₂ was 42 mm Hg (range, 17-109). Mean difference between PaCO₂ and PtcCO₂ was 1 mm Hg with 95% limits of agreement of − 3.4 to + 5.6 mm Hg. All measurement differences were within 5 mm Hg, and 32 (64%) were within 2 mm Hg.

Conclusion

Transcutaneous carbon dioxide pressure accurately predicts PaCO₂ in spontaneously breathing patients.     

Agreement between emergency medical services and expert blood pressure measurements

Background

Emergency Medical Services (EMS)-measured blood pressures (BPs) are utilized for administering medications in the field and for triage decisions. Retrospective work has demonstrated poor agreement between EMS and Emergency Department (ED) BP but has lacked a valid, reliable reference standard.

Study Objectives

To compare EMS BP measurements with those of trained research assistants (RA) and observe measurement technique for sources of error.

Methods

A prospective study was performed with a large urban EMS. BP measurements were made by RA within 5 min of patients presenting to the ED. EMS personnel were asked about technique. EMS personnel were then observed while RA simultaneously measured BP. Analysis was performed using methods outlined by Bland and Altman.

Results

There were 100 patients enrolled for each phase. In the first phase, the mean difference in systolic BP was −3.8 ± 18.6 mm Hg (95% confidence interval [CI] −8.3 to 0.59), and the mean difference in diastolic BP was 0.42 ± 13.8 mm Hg (95% CI −3.3 to 4.1). In the second phase, the mean difference in systolic BP was −4.6 ± 10.1 mm Hg (95% CI −6.6 to −2.6) and the mean difference in diastolic BP was −3.6 ± 10.6 mm Hg (95% CI −3.6 to −0.2). EMS personnel failed to properly place the cuff or deflate it 2–3 mm Hg/s in over 90% of the readings. They failed to properly inflate the cuff in 74% of the patients, and failed to properly place the stethoscope in 40%. EMS personnel demonstrated a significant preference for the terminal digit of “0” (p < 0.0001).

Conclusions

EMS and expert BP measurements showed smaller discrepancies than those previously noted, especially with simultaneous measurements. However, EMS demonstrated poor adherence to American Heart Association recommendations for measuring BP. EMS also showed terminal digit preference.     

Evaluation of the radial artery applanation tonometry technology for continuous noninvasive blood pressure monitoring compared with central aortic blood pressure measurements in patients with multiple organ dysfunction syndrome

Purpose

We compared blood pressure (BP) measurements obtained using radial artery applanation tonometry with invasive BP measurements using a catheter placed in the abdominal aorta through the femoral artery in patients with multiple organ dysfunction syndrome (MODS).

Materials and Methods

In 23 intensive care unit patients with MODS, we simultaneously assessed BP values for 15 minutes per patient using radial artery applanation tonometry (T-Line TL-200pro device; Tensys Medical Inc, San Diego, Calif) and the arterial catheter (standard-criterion technique). A total of 2879 averaged 10-beat epochs were compared using Bland-Altman plots.

Results

The mean difference ± SD (with corresponding 95% limits of agreement) between radial artery applanation tonometry–derived BP and invasively assessed BP was + 1.0 ± 5.5 mm Hg (− 9.9 to + 11.8 mm Hg) for mean arterial pressure, − 3.3 ± 11.2 mm Hg (− 25.3 to + 18.6 mm Hg) for systolic arterial pressure, and + 4.9 ± 7.0 mm Hg (− 8.8 to + 18.6 mm Hg) for diastolic arterial pressure, respectively.

Conclusions

In intensive care unit patients with MODS, mean arterial pressure and diastolic arterial pressure can be determined accurately and precisely using radial artery applanation tonometry compared with central aortic values obtained using a catheter placed in the abdominal aorta through the femoral artery. Although systolic arterial pressure could also be derived accurately, wider 95% limits of agreement suggest lower precision for determination of systolic arterial pressure.     

Central venous saturation in septic shock: co-oximetry vs gasometry

Objectives

Central venous oxygen saturation calculated by gasometry (Gaso-Scvo₂) is more available than central venous oxygen saturation measured by co-oximetry (Co-oxy-Scvo₂) in environments with less resources and underdeveloped countries. Therefore, we aimed to determine the agreement between Co-oxy-Scvo₂ and Gaso-Scvo₂ and between central venous oxygen tension measured by gasometry (Gaso-Pcvo₂) and Co-oxy-Scvo₂, respectively.

Design and settings

This is a prospective study in a university hospital’s intensive care unit.

Patients

Sixteen patients were studied during the first 48 hours after diagnosis of septic shock. All patients were intubated, connected to mechanical ventilation, and resuscitated according to the standards of care.

Measurements and results

One hundred eleven pairs of central venous blood measurements were analyzed both by conventional gasometry and co-oximetry. Bland and Altman analysis between Co-oxy-Scvo₂ and Gaso-Scvo₂ showed lack of agreement (1.7 [− 10.7, + 14.2]). A Gaso-Scvo₂ less than 70% had a positive predictive value of 63% in relation to Co-oxy-Scvo₂, and its negative predictive value was 90% with 20% false-positives and 5% false-negatives. The area under the receiver operator characteristic curve of Gaso-Pcvo₂ to discriminate a Co-oxy-Scvo₂ greater than or equal to 70% was 0.87 (confidence interval, 0.80-0.93), and the best cut-off point was a Gaso-Pcvo₂ more than 40 mm Hg, (sensitivity, 75%; specificity, 93%).

Conclusions

The reliability of Gaso-Scvo₂ determination during the resuscitation phase of septic shock is not acceptable. There is a good agreement between a Gaso-Pcvo₂ more than 40 mm Hg and a Co-oxy-Scvo₂ greater than or equal to 70%. Our results suggest that given these limitations, Gaso-Scvo₂ results should be interpreted with caution, helped by Gaso-Pcvo₂ measurements and in context with other perfusion parameters.     

High-frequency oscillatory ventilation with and without arteriovenous extracorporeal lung assist in patients with severe respiratory failure

Purpose

Elimination of carbon dioxide by an arteriovenous extracorporeal lung assist (av-ECLA) can facilitate the lung protective capabilities of high-frequency oscillatory ventilation (HFOV). This case series describes patients treated with HFOV because of severe respiratory failure with and without additional av-ECLA.

Methods

A retrospective analysis of 31 patients regarding patient characteristics, gas exchange, respirator settings, hemodynamics, and outcome. In 18 patients, av-ECLA was started before, together with, or during HFOV.

Results

The initial arterial carbon dioxide tension before HFOV and av-ECLA was higher in patients who received av-ECLA compared with patients without (P = .043): 65 (48-84) mm Hg and 50 (44-60) mmHg (median and interquartile range). The initial arterial oxygen tension (Pao₂)/inspiratory oxygen fraction (Fio₂) index in patients who received av-ECLA was 79 (63-133) mm Hg. The Pao₂/Fio₂ index immediately before HFOV was 84 (65-124) mm Hg (av-ECLA) and 121 (68-150) mmHg (no av-ECLA) and improved to 149 (89-231) mm Hg and 200 (117-233) mmHg during HFOV. Similarly, the oxygenation index improved. No statistically significant differences among groups were detected for Pao₂/Fio₂ index, oxygenation index, and arterial carbon dioxide tension immediately before and during HFOV. The hospital mortality was 39% (av-ECLA) and 69% (no av-ECLA).

Conclusions

High-frequency oscillatory ventilation improved the oxygenation in patients with severe respiratory failure. Additional av-ECLA may facilitate using lung protective HFOV settings in more severe lung injury and hypercapnia.     

Estimation of central venous pressure using inferior vena caval pressure from a femoral endovascular cooling catheter

Purpose

Endovascular cooling using the femoral cooling catheter is widely practiced. Central venous pressure (CVP) monitoring in patients undergoing femoral endovascular cooling may require the placement of another catheter near the right atrium (RA). We sought to estimate the agreement between the CVP recorded from catheters placed in the superior vena caval pressure (SVCP) and the inferior vena caval pressure (IVCP) recorded from the femoral cooling catheter in patients undergoing femoral endovascular cooling.

Methods

We enrolled adult cardiac arrest survivors undergoing femoral endovascular cooling. A commercially available central venous catheter was placed in the SVC (superior vena cava) near the RA via subclavian venous access. Both SVCP and IVCP were recorded every 4 hours during therapeutic hypothermia. Arterial pressure, heart rate, peak inspiratory pressure (PIP), and positive end expiratory pressure (PEEP) at the time of vena caval pressure measurements were obtained.

Results

A total of 323 pairs of SVCP and IVCP measurements were collected. The correlation coefficient between SVCP and IVCP was 0.965 (P < .001). The mean difference between SVCP and IVCP was − 0.45 mm Hg (SD, 1.27; 95% confidence interval, − 0.59 to − 0.31 mm Hg). The limits of agreement were − 2.94 to 2.05 mm Hg. Vena caval pressures were significantly correlated with airway pressures (peak inspiratory pressure and positive end expiratory pressure), whereas the difference between SVCP and IVCP did not correlate with airway pressures.

Conclusion

Inferior vena caval pressure measured via the femoral cooling catheter showed excellent agreement with CVP recorded from catheters placed in the SVC, which indicates that the femoral cooling catheter can be used for monitoring CVP.     

Validation of noninvasive pulse contour cardiac output using finger arterial pressure in cardiac surgery patients requiring fluid therapy

Introduction

Nexfin (Edwards Lifesciences, Irvine, CA) allows for noninvasive continuous monitoring of blood pressure (ABP_NI) and cardiac output (CO_NI) by measuring finger arterial pressure (FAP). To evaluate the accuracy of FAP in measuring ABP_NI and CO_NI as well as the adequacy of detecting changes in ABP and CO, we compared FAP to intra-arterially measured blood pressure (ABP_IA) and transpulmonary thermodilution (CO_TD) in postcardiac surgery patients during a fluid challenge (FC).

Methods

Twenty sedated patients post cardiac surgery were included, and 28 FCs were performed. Measurements of ABP and CO were simultaneously collected before and after an FC, and we compared CO and blood pressure.

Results

Finger arterial pressure was obtainable in all patients. When comparing ABP_NI with ABP_IA, bias was 2.7 mm Hg (limits of agreement [LOA], ± 22.2), 4.9 mm Hg (LOA, ± 13.6), and 4.2 mm Hg (LOA, ± 13.7) for systolic, diastolic, and mean arterial pressure, respectively. Concordance between changes in ABP_NI and ABP_IA was 100%. Mean bias between CO_NI and CO_TD was − 0.26 (LOA, ± 2.2), with a percentage error of 38.9%. Concordance between changes in CO_NI vs CO_TD and was 100%.

Conclusion

Finger arterial pressure reliably measures ABP and adequately tracks changes in ABP. Although CO_NI is not interchangeable with CO_TD, it follows changes in CO closely.     

Concordance between capnography and capnia in adults admitted for acute dyspnea in an ED

Background

End-tidal carbon dioxide pressure (etCO₂) is widely used in anaesthesia and critical care in intubated patients. The aim of our preliminary study was to evaluate the feasibility of a simple device to predict capnia in spontaneously breathing patients in an emergency department (ED).

Patients and methods

This study was a prospective, nonblind study performed in our teaching hospital ED. We included nonintubated patients with dyspnea (≥18 years) requiring measurement of arterial blood gases, as ordered by the emergency physician in charge. There were no exclusion criteria. End-tidal CO₂ was measured by an easy-to-use device connected to a microstream capnometer, which gave a continuous measurement and graphical display of the etCO₂ level of a patient's exhaled breath.

Results

A total of 43 patients (48 measurements) were included, and the majority had pneumonia (n = 12), acute cardiac failure (n = 8), asthma (n = 7), or chronic obstructive pulmonary disease exacerbation (n = 6). Using simple linear regression, the correlation between etCO₂ and Paco₂ was good (R = 0.82). However, 18 measurements (38%) had a difference between etCO₂ and Paco₂ of 10 mm Hg or more. The mean difference between the Paco₂ and etCO₂ levels was 8 mm Hg. Using the Bland and Altman matrix, the limits of agreement were −10 to +26 mm Hg.

Conclusion

In our preliminary study, etCO₂ using a microstream method does not seem to accurately predict Paco₂ in patients presenting to an ED for acute dyspnea.     

Capnography monitoring in nonintubated patients with respiratory distress

Objective

The objective was to assess agreement between end-tidal carbon dioxide values measured by a handheld capnometer (Petco₂) and values measured by a blood gas analyzer (Paco₂) in nonintubated patients with respiratory distress in an out-of-hospital setting.

Methods

This prospective study compared Petco₂ values obtained by an end-tidal capnometer (Microcap Plus; Oridion Capnography Inc, Needham, Mass) to Paco₂ values by the Bland and Altman statistical method.

Results

A total of 50 patients were included. Continuous Petco₂ monitoring was easily performed in all 50 patients during ambulance transport, but blood gas analysis failed in 1 patient. Agreement between the 2 methods was poor with a bias (mean difference) between Petco₂ and Paco₂ measurements of 12 mm Hg and a precision (SD of the difference) of 8 mm Hg. The gradient between Petco₂ and Paco₂ was greater than 5 and 10 mm Hg in 41 and 25 patients, respectively.

Conclusions

Petco₂ measurements poorly reflected Paco₂ values in our population of nonintubated patients with respiratory distress of various origins.     

Transfusion of Packed Red Blood Cells is Not Associated with Improved Central Venous Oxygen Saturation or Organ Function in Patients with Septic Shock

Background

The exact role of packed red blood cell (PRBC) transfusion in the setting of early resuscitation in septic shock is unknown.

Study Objective

To evaluate whether PRBC transfusion is associated with improved central venous oxygen saturation (ScvO₂) or organ function in patients with severe sepsis and septic shock receiving early goal-directed therapy (EGDT).

Methods

Retrospective cohort study (n = 93) of patients presenting with severe sepsis or septic shock treated with EGDT.

Results

Thirty-four of 93 patients received at least one PRBC transfusion. The ScvO₂ goal > 70% was achieved in 71.9% of the PRBC group and 66.1% of the no-PRBC group (p = 0.30). There was no difference in the change in Sequential Organ Failure Assessment (SOFA) score within the first 24 h in the PRBC group vs. the no-PRBC group (8.6–8.3 vs. 5.8–5.6, p = 0.85), time to achievement of central venous pressure > 8 mm Hg (732 min vs. 465 min, p = 0.14), or the use of norepinephrine to maintain mean arterial pressure > 65 mm Hg (81.3% vs. 83.8%, p = 0.77).

Conclusions

In this study, the transfusion of PRBC was not associated with improved cellular oxygenation, as demonstrated by a lack of improved achievement of ScvO₂ > 70%. Also, the transfusion of PRBC was not associated with improved organ function or improved achievement of the other goals of EGDT. Further studies are needed to determine the impact of transfusion of PRBC within the context of early resuscitation of patients with septic shock.     

Hemodynamic Effect of External Chest Compressions at the Lower End of the Sternum in Cardiac Arrest Patients

Background

Little is known about the hemodynamic effects of chest compression at different positions on the sternum during cardiopulmonary resuscitation (CPR).

Objectives

This study aimed to test whether external chest compression at the lower end of the sternum as an alternative position (alternative compression) results in superior hemodynamic effects compared to standard external chest compression (standard compression).

Methods

We enrolled 17 patients with non-traumatic cardiac arrest who failed to regain spontaneous circulation within 30 min after CPR initiation. Standard compression was begun when cardiac arrest was confirmed. Alternative compression was performed for 2 min if spontaneous circulation was not attained after 30 min of standard CPR. We compared hemodynamics and end-tidal CO₂ pressure during the last 2 min of standard compression and during alternative compression.

Results

Peak arterial pressure during compression systole (114 ± 51 vs. 95 ± 42 mm Hg, p < 0.001) and end-tidal CO₂ pressure (11.0 ± 6.7 vs. 9.6 ± 6.9 mm Hg, p < 0.05) were higher with alternative than standard compression, whereas arterial pressure during compression diastole, peak right atrial pressure, and coronary perfusion pressure did not differ between standard and alternative compression.

Conclusions

Compared to standard compression, alternative compression results in a higher peak arterial pressure and end-tidal CO₂ pressure, but no change in coronary perfusion pressure.     

A comparison of central venous and arterial base deficit as a predictor of survival in acute trauma

Background

The arterial base deficit has been demonstrated to be a marker of shock and predictive of survival in injured patients. The venous blood, however, may better reflect tissue perfusion. Its usefulness in trauma is unknown. We compared central venous with arterial blood gas analysis to determine which was a better predictor of survival in injured patients.

Methods

A prospective, nonrandomized series of acutely injured patients was investigated. Patients who had an arterial blood gas analysis for acid-base determination had a simultaneous central venous blood gas analysis and routine blood tests. Patient demographics, Injury Severity Score, and survival past 24 hours were recorded. Arterial and venous blood samples were analyzed for pH, Pco₂, Po₂, HCO₃, hemoglobin-oxygen saturation, base deficit, and lactate.

Results

One hundred patients were enrolled. There were 76 survivors and 24 nonsurvivors. Wilcoxon rank sum test and multivariate logistic regression were used for each recorded variable; only central venous base deficit was predictive of survival past 24 hours (P = .0081). Specifically, arterial base deficit was not predictive of survival past 24 hours.

Conclusion

In a prospective series of acutely injured patients, central venous base deficit, not arterial base deficit, was predictive of survival past 24 hours.     

Quantification of superoxide radical production in 4 vital organs of rats subjected to hemorrhagic shock

Objective

The aim of this study was to measure the production of superoxide radical (O₂⁻), a direct indicator of oxidative stress, in 4 vital organs of rats subjected to hemorrhagic shock. For this purpose, and for the first time, a new quantitative assay for the ex vivo measurement of O₂⁻ via an established 1:1 molar relationship between O₂⁻ and 2-OH-ethidium was used. The production of lipid hydroperoxides (LOOHs), a standard method of evaluation of oxidative stress, was also used for reasons of comparison.

Methods

Sixteen male Wistar rats were divided into 2 groups: sham and hemorrhagic shock, targeting to a mean arterial pressure of 30 to 40 mm Hg for 60 minutes. Three hours after resuscitation, tissues were collected for measurement of LOOHs and O₂⁻ production.

Results

Hemorrhagic shock induced increased production of LOOHs in the gut, liver, and lungs (P < .001), whereas the production of O₂⁻ was also increased in the gut (P < .001), liver (P < .001), and, to a lesser extent, in the lungs (P < .05). The oxidative load of the kidneys, as estimated by both techniques, remained unaffected.

Conclusion

The results of this new O₂⁻ assay were comparable with the results of the established LOOHs method, and this assay proved to be accurate and sensitive in the detection and quantification of O₂⁻ production in all organs tested. Thus, the proposed direct measurement of O₂⁻ in critically ill patients often facing in extremis situations could be used as a prognostic tool and as a method to evaluate therapeutic interventions in the setting of emergency medicine.     

Intra-abdominal hypertension in the critically ill: Interrater reliability of bladder pressure measurement

Purpose

Intra-abdominal hypertension is frequently underdiagnosed and defined by intra-abdominal pressure (IAP) 12 mm Hg or higher. Increasing IAP may compromise organ viability and culminate in abdominal compartment syndrome. Bladder pressure measurement is a surrogate for IAP, but measurement properties are unknown in the intensive care unit. Our primary objective was to assess the agreement of bladder pressure measurements in critically ill patients.

Methods

We conducted an observational study examining the correlation of measurement variability of bladder pressure. Four raters (2 nurses and 2 physicians) measured IAP. Patient's age, Acute Physiology and Chronic Health Evaluation II, body mass index, mechanical ventilation parameters, and demographics were collected.

Results

Fifty-one patients had bladder pressures measured in quadruplicate, producing 204 measurements. Among 51 patients, the mean age was 61.9 years, Acute Physiology and Chronic Health Evaluation II was 23.8, and body mass index was 27.8 kg/m². The average bladder pressure was 12.4 (SD, ± 6.2) mm Hg. The interrater agreement by intraclass correlation coefficient was 0.745 (95% confidence interval [CI], 0.637-0.825), 0.804 (95% CI, 0.684-0.882), and 0.626 (95% CI, 0.428-0.767) among all raters, physicians, and nurses, respectively.

Conclusions

Agreement on bladder pressure was high among 4 clinicians and were not significantly different between physicians and nurses. Given that medical/surgical treatments are considered on bladder pressure values, understanding their reliability is essential to monitor critically ill patients.     

The inability of emergency physicians to adequately clinically estimate the underlying hemodynamic profiles of acutely ill patients

Objective

Emergency physicians (EPs) estimate the underlying hemodynamics of acutely ill patients and use them to help both diagnose and formulate a treatment plan. This trial compared the EP clinically derived estimates of cardiac output (CO) and systemic vascular resistance (SVR) to those measured noninvasively.

Methods

Forty acutely ill emergency department patients with a broad range of diagnosis and blood pressure (BP) and pulse were monitored for 2 hours using novel noninvasive finger cuff technology (Nexfin; BMEYE, Amsterdam, The Netherlands). The Nexfin device provides continuous BP monitoring and, from the resulting pulse pressure waveform, calculates beat-to-beat CO and SVR. At baseline assessment and after 2 hours of testing and therapy, treating EPs were asked to estimate the CO and SVR (low, normal, or high), and these were compared with Nexfin measurements.

Results

Twenty-five men and 15 women were enrolled with a mean age of 62.2 years (SD, 12.6 years). Eighteen had acute shortness of breath; 11, with probable stroke syndrome; 3, with suspected sepsis; and 8, with a systolic BP greater than 180 or less than 100 mm Hg. Concordance tables showed that there was very little agreement (κ values) between either the compared initial CO (−0.0873) and SVR (−0.0645) or the 2-hour values (−0.0645 and −0.1949, respectively).

Conclusions

Emergency physicians cannot accurately estimate the underlying hemodynamic profiles of acutely ill patients when compared with more objective measurements. This inaccuracy may have important clinical ramifications. Further study is needed to determine how to use these measured continuous CO and SVR monitoring values.     

Improving the Validity of Peripheral Venous Blood Gas Analysis as an Estimate of Arterial Blood Gas by Correcting the Venous Values with SvO2

Background

Peripheral venous blood gas (pVBG) analysis in replacement of arterial blood gas (ABG) is limited by the unpredictable differences between arterial and venous values, especially for PCO₂ and pH (ΔPCO₂ and ΔpH).

Objectives

We hypothesized that, using the theoretical relationship linking SvO₂ and blood flow, we could diminish the effect of local circulatory conditions on ΔPCO₂ and ΔpH and thereby increase pVBG validity.

Methods

This was a prospective cross-sectional study performed in emergency patients requiring a blood gas analysis in which ABG and pVBG were performed simultaneously. The data of 50 randomly selected patients (model group) were used for developing two equations to correct PvCO₂ and pHv according to the peripheral SvO₂ (SpvO₂) level. The formulas derived were PvCO_2cor = PvCO₂ − 0.30 × (75 − SpvO₂), and pHv_cor = pHv + 0.001 × (75 − SpvO₂). The validity of the corrected values was then tested on the remaining population (validation group).

Results

There were 281 patients included in the study, mainly for dyspnea. ΔPCO₂ and ΔpH were strongly correlated with SpvO₂ (r² = 0.62 and r² = 0.53, respectively, p < 0.001). Using the data of the model group, we developed equations that we applied on the validation group. We found that the corrected values were more valid than the raw values for detecting a PaCO₂ > 45 mm Hg (AUC ROC = 0.96 ± 0.01 vs. 0.89 ± 0.02, p < 0.001), a PaCO₂ < 35 mm Hg (AUC = 0.95 ± 0.02 vs. 0.84 ± 0.03, p < 0.001), a pHa < 7.35 (AUC = 0.97 ± 0.01 vs. 0.95 ± 0.02, p < 0.05), or a pHa > 7.45 (AUC = 0.91 ± 0.02 vs. 0.81 ± 0.04, p < 0.001).

Conclusions

The variability of ΔPCO₂ and ΔpH is significantly lowered when the venous values are corrected according to the SpvO₂ value, and pVBG is therefore more accurate and valid for detecting an arterial abnormality.     

Radiologic diagnoses of patients who received imaging for venous thromboembolism despite negative D-dimer tests

Objective

The literature supports a negative D-dimer (−DD) excluding venous thromboembolic disease (VTE) in low-risk patients. We determined the radiologic diagnoses in patients where imaging was ordered despite a −DD.

Methods

This is a retrospective chart review of patients with a −DD (Tinaquant; Roche Diagnostics, Mannheim, Germany) and a radiologic study within 48 hours, sought to determine radiologic diagnosis (primary outcome), treatment of VTE, and consensus diagnosis of acute VTE.

Results

Among 3462 DD tests, 1678 met the inclusion criteria. Of 1362 patients with DD values of 350 ng/mL or less, 166 (12.2%) had radiologic studies: 93.4% of the final radiologic diagnoses were negative for VTE, 3.6% were indeterminate, and 3.0% (1.0%-6.9%) were positive; 1.8% ultimately had a consensus diagnosis of acute VTE. In 316 patients with DD values between 351 and 500 ng/mL, 88 (27.8%) had radiologic studies: 95.5% were negative, 1.1% were indeterminate, and 3.4% (0.7%-9.6%) were positive.

Conclusions

Of patients who receive radiologic studies despite −DD tests, 3.0% have positive radiologic diagnoses for acute VTE; only 1.8% had acute VTE after the review of their hospital course.     

The oxygenation ratio during mechanical ventilation in children: The role of tidal volume and positive end-expiratory pressure

Objective

The objective of this study is to analyze the role of tidal volume (Vt) and positive end-expiratory pressure on the oxygenation ratio (OR) (Pao₂/Fio₂) during mechanical ventilation (MV) in children with a normal pulmonary gas exchange on admission.

Methods

A retrospective cohort study of children with an admission OR greater than 300 mm Hg and duration of MV greater than 48 hours (n = 96) was done. We analyzed Vt, Fio₂, Pao₂, and positive end-expiratory pressure and calculated Vt (mL/kg) and Pao₂/Fio₂ based on the measured Vt and weight. Patients were divided into group 1, Vt less than 9 mL/kg (n = 24); 2, Vt 9 to 12 mL/kg (n = 58); and 3, Vt 12 mL/kg or higher (n = 14).

Results

Baseline characteristics and OR were comparable. Forty-one percent of patients developed OR less than 300 mm Hg. The proportion of patients developing an OR less than 300 mm Hg was lowest in group 1 and highest in group 3, and differences became more pronounced with longer MV duration: 56%, 58%, and 89% on day 5; 29%, 65%, and 100% on day 7 (P = .05); 0%, 40%, and 100% on day 10 (P = .03). In patients maintaining an OR greater than 300 mm Hg during 10 days of MV, Vt was 9.3 ± 1.0 vs 12.7 ± 4.8 mL/kg in patients developing an OR less than 300 mm Hg (P = .05). Mechanical ventilation duration was longer in children developing OR less than 300 mm Hg (P < .01). Positive end-expiratory pressure levels were not significantly different between groups.

Conclusion

In ventilated children, Vt was greater than 9 mL/kg were associated with increased development of an OR less than 300 mm Hg and longer duration of MV.