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The influence of delayed sample processing time on the PO₂ values in critically ill patients with sepsis-induced leukocytosis
Background: The ability to correctly measure the partial pressure of Oxygen is one of the fundamental test that influence clinical decision making in a septic ICU patient. The study examined the extent of error over time, from collection to processing, when measuring blood gas samples for PO₂, PCO₂,...
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| Format: | Thesis |
| Language: | English |
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Department of Anaesthesia
2018
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| _version_ | 1867613360469573633 |
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| access_status_str | Open Access |
| author | Pretorius, Petrus Rohan |
| author2 | Myburgh, Adriaan |
| author_browse | Myburgh, Adriaan Pretorius, Petrus Rohan |
| author_facet | Myburgh, Adriaan Pretorius, Petrus Rohan |
| author_sort | Pretorius, Petrus Rohan |
| collection | Thesis |
| description | Background: The ability to correctly measure the partial pressure of Oxygen is one of the fundamental test that influence clinical decision making in a septic ICU patient. The study examined the extent of error over time, from collection to processing, when measuring blood gas samples for PO₂, PCO₂, pH, in critically-ill patients with sepsis and metabolically active leucocytosis > 12 000/mm³ and compares it with a control, where immersing it in ice has stopped metabolism. Methods: Thirty septic ICU patients with confirmed leucocytosis > 12 000/mm³, who had routine arterial blood analysed was included in the study. Blood form the standard PICO50 radiometer arterial blood sampler (2ml) syringe was decanted into two 1ml Glass syringes that was pre-heparinised with 1ml Heparin 1000U - all excess Heparin removed. One syringe was cooled with ice slurry and tested as a control at 60 minutes The other syringe was used to repeatedly analyse the sample at 0,10, 30 and 60 minutes. The syringes were sealed with plastecine and a glass capillary tube was use to decant the sample just prior to analysis to fit the analyser. Samples were processed using an ABL 800 blood gas analyser. Results: The mean absolute difference in PO₂ at 10 minutes was -0.94 kPa (95% CI: -1.48 to -0.4 kPa), at 30 minutes -2.42 kPa (95% CI: -3.10 to -1.75 kPa) and at 60 minutes -4.44 kPa (95% CI: -5.54 to -3.34 kPa). The relative difference in pO₂ at 10 minutes was -4.98% (95% CI: -8.12 to -1.84%), at 30 minutes -13.79% (95% CI: -17.40 to -10.17%) and 60 minutes -25.46% (95% CI: -30.97 to -19.95%). The absolute difference in PO₂ at 60 minutes on Ice was - 0.31 kPa. Conclusion: Delayed blood gas analysis in Septic ICU patients with a raised WCC > 12 000/mm³, results in statistical and possible clinical significant abnormality in the pO₂, that progressively worsens with time. After 10 minutes there was a 5% change, at 30 minutes a 14% change and there was a 25% change from baseline PO₂ at 60 minutes. The magnitude of change with statistical mixed linear models shows the rate of decline to be of the magnitude of 1% per minute. So at 60 minutes, the ratio change is 0.7313859 (0.9948 to the power of 60).This deviation may alter clinical decision making. |
| format | Thesis |
| id | oai:open.uct.ac.za:11427/26939 |
| institution | University of Cape Town (South Africa) |
| language | eng |
| last_indexed | 2026-06-10T12:34:54.857Z |
| license_str | Not specified — see source repository |
| provenance_str_mv | Harvested via OAI-PMH from UCTD — University of Cape Town Open Access Repository |
| publishDate | 2018 |
| publishDateRange | 2018 |
| publishDateSort | 2018 |
| publisher | Department of Anaesthesia |
| publisherStr | Department of Anaesthesia |
| record_format | dspace |
| source_str | UCTD — University of Cape Town Open Access Repository |
| spelling | oai:open.uct.ac.za:11427/26939 The influence of delayed sample processing time on the PO₂ values in critically ill patients with sepsis-induced leukocytosis Pretorius, Petrus Rohan Myburgh, Adriaan Anaesthesia Background: The ability to correctly measure the partial pressure of Oxygen is one of the fundamental test that influence clinical decision making in a septic ICU patient. The study examined the extent of error over time, from collection to processing, when measuring blood gas samples for PO₂, PCO₂, pH, in critically-ill patients with sepsis and metabolically active leucocytosis > 12 000/mm³ and compares it with a control, where immersing it in ice has stopped metabolism. Methods: Thirty septic ICU patients with confirmed leucocytosis > 12 000/mm³, who had routine arterial blood analysed was included in the study. Blood form the standard PICO50 radiometer arterial blood sampler (2ml) syringe was decanted into two 1ml Glass syringes that was pre-heparinised with 1ml Heparin 1000U - all excess Heparin removed. One syringe was cooled with ice slurry and tested as a control at 60 minutes The other syringe was used to repeatedly analyse the sample at 0,10, 30 and 60 minutes. The syringes were sealed with plastecine and a glass capillary tube was use to decant the sample just prior to analysis to fit the analyser. Samples were processed using an ABL 800 blood gas analyser. Results: The mean absolute difference in PO₂ at 10 minutes was -0.94 kPa (95% CI: -1.48 to -0.4 kPa), at 30 minutes -2.42 kPa (95% CI: -3.10 to -1.75 kPa) and at 60 minutes -4.44 kPa (95% CI: -5.54 to -3.34 kPa). The relative difference in pO₂ at 10 minutes was -4.98% (95% CI: -8.12 to -1.84%), at 30 minutes -13.79% (95% CI: -17.40 to -10.17%) and 60 minutes -25.46% (95% CI: -30.97 to -19.95%). The absolute difference in PO₂ at 60 minutes on Ice was - 0.31 kPa. Conclusion: Delayed blood gas analysis in Septic ICU patients with a raised WCC > 12 000/mm³, results in statistical and possible clinical significant abnormality in the pO₂, that progressively worsens with time. After 10 minutes there was a 5% change, at 30 minutes a 14% change and there was a 25% change from baseline PO₂ at 60 minutes. The magnitude of change with statistical mixed linear models shows the rate of decline to be of the magnitude of 1% per minute. So at 60 minutes, the ratio change is 0.7313859 (0.9948 to the power of 60).This deviation may alter clinical decision making. 2018-01-25T06:36:16Z 2018-01-25T06:36:16Z 2017 Master Thesis Masters MMed http://hdl.handle.net/11427/26939 eng application/pdf Department of Anaesthesia Faculty of Health Sciences University of Cape Town |
| spellingShingle | Anaesthesia Pretorius, Petrus Rohan The influence of delayed sample processing time on the PO₂ values in critically ill patients with sepsis-induced leukocytosis |
| thesis_degree_str | Master's |
| title | The influence of delayed sample processing time on the PO₂ values in critically ill patients with sepsis-induced leukocytosis |
| title_full | The influence of delayed sample processing time on the PO₂ values in critically ill patients with sepsis-induced leukocytosis |
| title_fullStr | The influence of delayed sample processing time on the PO₂ values in critically ill patients with sepsis-induced leukocytosis |
| title_full_unstemmed | The influence of delayed sample processing time on the PO₂ values in critically ill patients with sepsis-induced leukocytosis |
| title_short | The influence of delayed sample processing time on the PO₂ values in critically ill patients with sepsis-induced leukocytosis |
| title_sort | influence of delayed sample processing time on the po₂ values in critically ill patients with sepsis induced leukocytosis |
| topic | Anaesthesia |
| url | http://hdl.handle.net/11427/26939 |
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