Need For Arterial Sampling Research Articles

Calculating acid-base and oxygenation status during COPD exacerbation using mathematically arterialised venous blood

Repeated arterial puncture is painful. A mathematical method exists for transforming peripheral venous pH, PCO 2 and PO 2 to arterial eliminating the need for arterial sampling. This study evaluates this method to monitor acid base and oxygenation during admission for exacerbation of chronic obstructive pulmonary disease (COPD). Simultaneous arterial and peripheral venous blood was analysed. Venous values were used to calculate arterial pH, PCO 2 and PO 2, with these compared to measured values using Bland-Altman analysis and scatter plots. Calculated values of PO 2 were assessed with previously defi ned rules.Differences between maximal changes of calculated and measured values were compared using a t-test, with trends analysed by inspection of plots. Fifty-four patients, median age 67 years (range 62 – 75), were studied on average 3 days. Mean values of pH,PCO 2 and PO 2 were 7.432 } 0.047, 6.8 } 1.7 kPa and 9.2 } 1.5kPa, respectively. Calculated and measured arterial pH and PCO 2 agreed well, differences having small bias and SD(0.000 } 0.022 pH, – 0.06 } 0.50 kPa PCO 2 ), significantly better than venous blood alone. Calculated PO 2 obeyed the clinical rules. Calculated values could track patients, with no significant differences in maximal changes in measured and calculated values (pH p = 0.96, PCO 2 p = 0.62, PO 2 p = 0.33), and time-course plots matching quantity and pattern of change in measurements. This study shows that arterial pH, PCO 2 and PO 2 can be calculated from peripheral venous values so as to characterise changes seen during exacerbation. Application of the method has potential to reduce arterial sampling, decrease discomfort and enable venous sampling as routine practice.

Partial volume corrected image derived input functions for dynamic PET brain studies: Methodology and validation for [11C]flumazenil

Extraction of arterial input functions from dynamic brain scans may obviate the need for arterial sampling and would increase the clinical applicability of quantitative PET studies. The aim of the present study was to evaluate applicability and accuracy of image derived input functions (IDIFs) following reconstruction based partial volume correction (PVC).Settings for the PVC ordered subset expectation maximization (PVC-OSEM) reconstruction algorithm were varied. In addition, different methods for defining arterial regions of interest (ROI) in order to extract IDIFs were evaluated. [11C]flumazenil data of 10 subjects were used in the present study. Results obtained with IDIFs were compared with those using standard on-line measured arterial input functions. These included areas under the curve (AUC) for peak (1–2 min) and tail (2–60 min), volume of distribution (VT) obtained using Logan analysis, and VT and K1 obtained with a basis function implementation of a single tissue compartment model.Best results were obtained with PVC-OSEM using 4 iterations and 16 subsets. Based on 11C point source measurements, a 4.5 mm FWHM (full width at half maximum) resolution kernel was used to correct for partial volume effects. A ROI consisting of the four hottest pixels per plane (over the carotid arteries) was the best method to extract IDIFs. Excellent peak AUC ratios (0.99±0.09) between IDIF and blood sampler input function (BSIF) were found. Furthermore, extracted IDIFs provided VT and K1 values that were very similar to those obtained using BSIFs.The proposed method appears to be suitable for analysing [11C]flumazenil data without the need for online arterial sampling.

The utility of venous lactate to triage injured patients in the trauma center

Background: Field triage criteria for trauma patients results in over-triage rates of 30% to 50% to achieve under-triage rates of 10%. This large number of patients may stress trauma center resources. Elevated arterial lactate (ALAC) levels have been shown to be a marker of serious injury but the need for arterial sampling limits the utility of the determination. The goal of this study was: 1) to determine the correlation between venous lactate (VLAC) and ALAC; 2) to determine whether VLAC could identify those patients with serious injuries; and 3) to compare an elevated VLAC level against standard triage criteria (STC) in their ability to identify major injury. Study Design: Arterial and venous samples for blood gas and lactate analyses were obtained in 375 patients within 10 minutes of patient arrival to the trauma center. Arterial and venous samples were drawn within 2 minutes of each other, placed on ice, and analyzed within 10 minutes of sampling. The location of sampling was left to physician discretion. Data collected included injury mechanism, demographics, admission vital signs, emergency department disposition, length of stay, and injury severity scores (ISS). Admission to the ICU, need for emergency operation, length of stay, and death were noted. Emergency medical service staff were queried to determine which standard triage criteria (STC) were fulfilled. Results: The mean ALAC was 3.11 mmol/L (SD 3.45, 95% confidence interval [CI] 2.67 to 3.55) and mean VLAC was 3.43 mmol/L (SD 3.41, 95% CI 2.96 to 3.90). There was no significant difference between ALAC and VLAC. The correlation between ALAC and VLAC was 0.94 (95% CI 0.94 to 0.96, p = 0.0001). An elevated VLAC predicted moderate to severe injury and there was a significant association between an increased lactate and maximum Abbreviated Injury Score (AIS) of 4 and 5 (ANOVA, F = 8.26, p < 0.001). Patients with VLAC ≥ 2 mmol/L had significantly increased relative risks of ISS ≥ 13, death, admission to the ICU, and length of stay > 2 days. In comparison with STC, a VLAC ≥ 2 mmol/L decreased under-triage in patients with ISS ≥ 13 by one half (11% versus 24%) for patients with ISS ≥ 13 and decreased over-triage by 28% (46% versus 64%). These data were most pronounced for patients injured in motor vehicle collisions. Conclusions: VLAC is an excellent approximation for ALAC. A VLAC ≥ 2 mmol/L appears to predict an ISS ≥ 13, the need for ICU resources, and prolonged hospital stays. VLAC was significantly better than STC in all patients and was most useful in victims of blunt trauma, especially motor vehicle collisions.