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Capillary blood gases
- Girish Gupta, India --411 040 (19 February 2004)
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Poor statistical reporting
- Jaishen Rajah (19 February 2004)
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Critically ill children
- Paul A. Heaton (22 April 2004)
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Girish Gupta, Associate Professor Armed forces Medical College,Pune, India --411 040
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guptas-ip{at}eth.net Girish Gupta, et al.
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Dear Editor I read with interest the study of Yldzda et al[1] on topic of Correlation of simultaneously obtained capillary, venous, and arterial blood gases of patients in a paediatric intensive care unit. The article is of great practical significance in managing small children in critical care units. However, there are some apprehensions of sampling for blood gas analysis from capillary. In hypothermic, hypotensive children and neonates with prolonged capillary refilling time, it is very difficult to get blood from a small peripheral vein & is extremely difficult to get the blood sample from heel stick. In attempt to get sufficient capillary blood sample one may end up with some local manipulation including inadvertent squeezing of punctured local area, with consequent incorrect blood gas analysis. Therefore, an attempt to prewarm the heel especially in neonates is a good practice for doing CBG with better likely correlation with ABG.[2] However, one can also use another site like ear lobules for CBG which is likely to provide adequate capillary blood sample by being more vascular structure & is likely to be less affected with perfusion confounders as mentioned earlier.[3] In addition, one has to pay adequate attention to make it pain free procedure by appropriate use of pre-procedure analgesic strategy, otherwise crying will confound the blood gas results. I humbly request the workers for their response to the comments offered. References 1. Yldzda D,Yapcolu H,Ylmaz HL and Sertdemir Y. Correlation of simultaneously obtained capillary, venous, and arterial blood gases of patients in a paediatric intensive care unit Archives of Disease in Childhood 2004;89:176-180 2. Jackson MR, Chuo J. Blood gas & pulmonary graphic monitoring In:Manual of Neonatal care,5th edn. Eds Cloherty JP, Eichenwald EC, Stark AR. Lippincott Williams & Wilkins, Philadelphia, 2004; pp 362 3. Dawson S, Cave C, Pavord I, Potter JF. Transcutaneous monitoring of blood gases: is it comparable with arterialized earlobe sampling? Respir Med. 1998 Mar;92(3):584-7. |
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Jaishen Rajah, Pediatric Intensivist Sheikh Khalifa Medical Center
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rajjai741{at}skmc.gov.ae Jaishen Rajah
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Dear Editor The objective of the authors is commendable as easier methods than aterial blood gases are pragmatic without an arterial line. However, the statistical methods used are archaic. The authors present us with a list of p values (without Bonferroni correction-not that this is the papers biggest statistical problem) and corrlation coefficients. In recent times statisticians have been at pains to point out the importance of estimation (confidence intervals). As a intensivist, it would be far more meaningful, for example, to know the estimated difference between capillary and arterial pH, CO2, 02, and with what certainity ie the confidence intervals eg. the difference between the arterial and capillary oxygen was 10 mm Hg (CI 4). It behoves editors of the journal to be more rigourous in this aspect. From a practical point of view, my response to the morass of p values is unfortunately, SO WHAT? |
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Paul A. Heaton, Consultant Paediatrician Yeovil District Hospital
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heatp{at}est.nhs.uk Paul A. Heaton
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Dear Editor The authors report data from 116 patients admitted to a Paediatric Intensive Care Unit (PICU)on account of a variety of conditions.[1] Each patient had simultaneous measurement of arterial, venous and capillary blood taken when there were clinical indications for blood gas analysis. I was suprised to see that only few patients admitted to a PICU had evidence of significant compromise; there were about 7 individual recordings of pH less than 7.3 and none less than 7.2. Likewise there were only 10 recordings where pCo2 was greater than 60mm Hg, and small numbers had HCO3 less than 20 or base excess more negative than -10. Why were there so few childern with severely abnormal blood gases? Do the authors recommend that there is good correlation between blood gas analysis values of blood sampled from arterial, venous and capillary sites in such cases? Reference 1. D Yildizdas, H Yapicioglu, H L Yilmaz, and Y Sertdemir. Correlation of simultaneously obtained capillary, venous, and arterial blood gases of patients in a paediatric intensive care unit. Arch. Dis. Child. 2004; 89: 176-180. |
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