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Comparison of pulse oximetry and arterial blood gas measurements in critically ill patients
121 AUSTRALIAN CRITICAL CARE
10 blood pump and AN69 flat plate filter circuit. Total circuit filtration time was 6,448.2 hours for the CAVHD group and 27,600.1 hours for the CVVHD group. All circuits ceased prematurely due to patient transfer for clinical investigation or surgery, completion of treatment or death were eliminated from analysis. Mean + SD/median circuit life for CAVHD was 19.3 + 12.2/15.9 hours compared to 14.5 + 7.3/13.2 hours for CVVHD. This difference was considered statistically significant (Mann-Whitney Test p=0.035), suggesting that, in our experience, CAVHD circuits last at least as long, if not longer, than a similar pump-driven mode, CVVHD. This difference does not support the assertion that pump control of blood flow increases circuit life in continuous renal replacement therapy. Possible explanations include the shorter circuit and large-bore cannula of the Scribner Shunt used with CAVHD and the propensity for flat plate filters to rupture under the higher flow rate conditions of a pump-driven circuit.
Comparison of pulse oximetry and arterial blood gas measurements in critically ill patients KM Rowley, M Salagaras, JL Moran & SL Peake The Queen Elizabeth Hospital, Woodville, South Australia A difference between oxygen saturation via pulse oximetry (SpO2) and simultaneously measured arterial oxygen saturation (SaO2) has been observed in critically ill patients. Variables determining this difference were prospectively investigated in 33 adult patients in the first 24 hours post admission to the intensive care unit (ICU). Haemodynamic observations, core and skin temperatures, total arterial blood gas analysis, SpO2, oxygen therapy and inotrope use were recorded. SpO2-SaO2 concordance and the influence of recorded variables on this was analysed using (i) Lin concordance correlation coefficient for agreement (combining measures of precision and accuracy – perfect agreement, rho_c=1.0) and (ii) the Bland-Altman Limits of Agreement (LOA) method 1. The patients’ mean (SD) APACHE II score was 23(8) and age 67(17) years. Overall mean SpO2 and SaO2 were 95.6(3) and 95.3(2) respectively. There were 369 paired SpO2 and SaO2 observations, with rho_c of 0.65 (95 per cent CI, 0.59-0.70) and LOA of -4.6 to 4.4 per cent. The cut-off levels for variables significantly influencing SpO2-SaO2 concordance (with corresponding rho_c values) are as follows. Variable Cut-off
MAP Core-skin temp Hb (g/dl) Inotropes (mmHg) diff (°C) 41-93 94-130 0.1-0.6 0 0.7-3.5 4.4-10.3 10.4-16.3 Yes No
Rho_c
0.47
0.90
0.72
0.57
0.41
0.77
0.50
95% CI
0.39- 0.86-
0.65-
0.47-
0.29-
0.72-
0.37- 0.65-
0.55
0.78
0.66
0.53
0.82
0.63
0.94
T Hughes, S Baulch & W Silvester Austin & Repatriation Medical Centre Heidelberg, Victoria There has been a common belief that electrolyte analysis by hospital biochemistry laboratories is more accurate and reliable than analysis by the arterial blood gas (ABG) analysers housed within the intensive care unit (ICU) and used by the nurses to provide results within minutes. The precision of this ICU’s ABG analyser falls within the top 20 per cent of electrolyte analysers in Australasia (Royal College of Pathologists of Australasia quality assurance program). This study aimed to compare simultaneous results from two analysers based in the ICU and one based in the hospital’s biochemistry department. Method: simultaneous blood samples were obtained from 90 patients on their admission to the ICU and analysed by the ICU’s CIBA Corning 865 (Chiron Diagnostics, Massachusetts) for Na+, K+ and Cl-, by the ICU’s AVL 988 (Graz, Austria) for Na+, and by the biochemistry department’s Hitachi 911(Tokyo) for Na+, K+ and Cl-. Analysis included Bland-Altman comparison of methods. Results: represented as mean and standard deviation Analyte
Mean
Standard Method comparison Bias (mean 95% limits deviation
Na+ - CIBA 136.8
6.4
Na+ - Hitachi-CIBA
difference) of agreement 3.72
Na+ - Hitachi 141.4
4.3
Na+ - Hitachi-AVL
2.1
-3.1 to 7.2
Na+ - AVL
138.6
6.4
Na+ - AVL-CIBA
1.87
-1.9 to 5.6
K+ - CIBA
4.1
0.6
K+ - Hitachi-CIBA
0.09
-0.6 to 0.8
K+ -Hitachi
4.2
0.6
Cl- - CIBA
103.7
6.6
Cl- - Hitachi-CIBA
-0.24
-5.5 to 5.0
Cl- - Hitachi 104.7
5.8
-1.2 to 8.7
Conclusion: point-of-care testing in our ICU compares excellently
Critical care nursing education: description of a collaborative model between a university and multiple hospital partners D Kamaker, M Fisher, G Burr, J Blundell & D Elliott Department of Clinical Nursing The University of Sydney, New South Wales
0.71
0.77
Differences between simultaneously measured SpO2 and SaO2 occur in critically ill patients. They are determined by inotrope use and certain cut-off levels for MAP, core-skin temperature difference and haemoglobin concentration. Reference: 1. Steichen P et al. Concordance correlation coefficient. STATA Technical Bulletin 1998; 43:35-39. VOLUME 12
Comparison of electrolyte analysis between intensive care unit point of care testing and biochemistry laboratory
NUMBER 3
The establishment of postgraduate education for critical care nurses in universities has highlighted the need for active and continuous collaboration between health care and tertiary education sectors. This paper discusses a collaborative model of curriculum development and implementation between a faculty of nursing and several teaching hospitals in a large metropolitan area. The philosophy of the curriculum development team for the Graduate Diploma/Master of Nursing (Critical Care) was to foster active partnerships with clinical areas so that an academically rigorous and clinically appropriate course could be designed and implemented. This strategy is underSEPTEMBER 1999
10 blood pump and AN69 flat plate filter circuit. Total circuit filtration time was 6,448.2 hours for the CAVHD group and 27,600.1 hours for the CVVHD group. All circuits ceased prematurely due to patient transfer for clinical investigation or surgery, completion of treatment or death were eliminated from analysis. Mean + SD/median circuit life for CAVHD was 19.3 + 12.2/15.9 hours compared to 14.5 + 7.3/13.2 hours for CVVHD. This difference was considered statistically significant (Mann-Whitney Test p=0.035), suggesting that, in our experience, CAVHD circuits last at least as long, if not longer, than a similar pump-driven mode, CVVHD. This difference does not support the assertion that pump control of blood flow increases circuit life in continuous renal replacement therapy. Possible explanations include the shorter circuit and large-bore cannula of the Scribner Shunt used with CAVHD and the propensity for flat plate filters to rupture under the higher flow rate conditions of a pump-driven circuit.
Comparison of pulse oximetry and arterial blood gas measurements in critically ill patients KM Rowley, M Salagaras, JL Moran & SL Peake The Queen Elizabeth Hospital, Woodville, South Australia A difference between oxygen saturation via pulse oximetry (SpO2) and simultaneously measured arterial oxygen saturation (SaO2) has been observed in critically ill patients. Variables determining this difference were prospectively investigated in 33 adult patients in the first 24 hours post admission to the intensive care unit (ICU). Haemodynamic observations, core and skin temperatures, total arterial blood gas analysis, SpO2, oxygen therapy and inotrope use were recorded. SpO2-SaO2 concordance and the influence of recorded variables on this was analysed using (i) Lin concordance correlation coefficient for agreement (combining measures of precision and accuracy – perfect agreement, rho_c=1.0) and (ii) the Bland-Altman Limits of Agreement (LOA) method 1. The patients’ mean (SD) APACHE II score was 23(8) and age 67(17) years. Overall mean SpO2 and SaO2 were 95.6(3) and 95.3(2) respectively. There were 369 paired SpO2 and SaO2 observations, with rho_c of 0.65 (95 per cent CI, 0.59-0.70) and LOA of -4.6 to 4.4 per cent. The cut-off levels for variables significantly influencing SpO2-SaO2 concordance (with corresponding rho_c values) are as follows. Variable Cut-off
MAP Core-skin temp Hb (g/dl) Inotropes (mmHg) diff (°C) 41-93 94-130 0.1-0.6 0 0.7-3.5 4.4-10.3 10.4-16.3 Yes No
Rho_c
0.47
0.90
0.72
0.57
0.41
0.77
0.50
95% CI
0.39- 0.86-
0.65-
0.47-
0.29-
0.72-
0.37- 0.65-
0.55
0.78
0.66
0.53
0.82
0.63
0.94
T Hughes, S Baulch & W Silvester Austin & Repatriation Medical Centre Heidelberg, Victoria There has been a common belief that electrolyte analysis by hospital biochemistry laboratories is more accurate and reliable than analysis by the arterial blood gas (ABG) analysers housed within the intensive care unit (ICU) and used by the nurses to provide results within minutes. The precision of this ICU’s ABG analyser falls within the top 20 per cent of electrolyte analysers in Australasia (Royal College of Pathologists of Australasia quality assurance program). This study aimed to compare simultaneous results from two analysers based in the ICU and one based in the hospital’s biochemistry department. Method: simultaneous blood samples were obtained from 90 patients on their admission to the ICU and analysed by the ICU’s CIBA Corning 865 (Chiron Diagnostics, Massachusetts) for Na+, K+ and Cl-, by the ICU’s AVL 988 (Graz, Austria) for Na+, and by the biochemistry department’s Hitachi 911(Tokyo) for Na+, K+ and Cl-. Analysis included Bland-Altman comparison of methods. Results: represented as mean and standard deviation Analyte
Mean
Standard Method comparison Bias (mean 95% limits deviation
Na+ - CIBA 136.8
6.4
Na+ - Hitachi-CIBA
difference) of agreement 3.72
Na+ - Hitachi 141.4
4.3
Na+ - Hitachi-AVL
2.1
-3.1 to 7.2
Na+ - AVL
138.6
6.4
Na+ - AVL-CIBA
1.87
-1.9 to 5.6
K+ - CIBA
4.1
0.6
K+ - Hitachi-CIBA
0.09
-0.6 to 0.8
K+ -Hitachi
4.2
0.6
Cl- - CIBA
103.7
6.6
Cl- - Hitachi-CIBA
-0.24
-5.5 to 5.0
Cl- - Hitachi 104.7
5.8
-1.2 to 8.7
Conclusion: point-of-care testing in our ICU compares excellently
Critical care nursing education: description of a collaborative model between a university and multiple hospital partners D Kamaker, M Fisher, G Burr, J Blundell & D Elliott Department of Clinical Nursing The University of Sydney, New South Wales
0.71
0.77
Differences between simultaneously measured SpO2 and SaO2 occur in critically ill patients. They are determined by inotrope use and certain cut-off levels for MAP, core-skin temperature difference and haemoglobin concentration. Reference: 1. Steichen P et al. Concordance correlation coefficient. STATA Technical Bulletin 1998; 43:35-39. VOLUME 12
Comparison of electrolyte analysis between intensive care unit point of care testing and biochemistry laboratory
NUMBER 3
The establishment of postgraduate education for critical care nurses in universities has highlighted the need for active and continuous collaboration between health care and tertiary education sectors. This paper discusses a collaborative model of curriculum development and implementation between a faculty of nursing and several teaching hospitals in a large metropolitan area. The philosophy of the curriculum development team for the Graduate Diploma/Master of Nursing (Critical Care) was to foster active partnerships with clinical areas so that an academically rigorous and clinically appropriate course could be designed and implemented. This strategy is underSEPTEMBER 1999