Critical Care |

Understanding the Limitations of Your Arterial Blood Gas (ABG) Analysis FREE TO VIEW

Veronica Brito, MD; Peter Spiegler, MD; Shweta Upadhyay*, MBBS
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Winthrop University Hospital, Mineola, NY

Chest. 2012;142(4_MeetingAbstracts):313A. doi:10.1378/chest.1390371
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SESSION TYPE: Critical Care Case Report Posters

PRESENTED ON: Tuesday, October 23, 2012 at 01:30 PM - 02:30 PM

INTRODUCTION: ABG analysis is required to measure important parameters in critically ill patients, including co-oximetry. Clinicians should be aware of the limitations on the test.

CASE PRESENTATION: We present a case of a 44 year-old woman admitted to the hospital for worsening shortness of breath and cough. She has a history of dermatomyositis and at the time of admission was being treated with systemic steroids. Her physical exam showed hypoxemia, tachypnea and fever. Computer Tomography showed ground-glass opacities bilaterally. Pneumocystis jerovecii was identified in bronchoalveolar lavage. She subsequently developed respiratory failure and a diagnosis of ARDS was made. Her initial antimicrobial regimen was Meropenem, Vancomycin and Sulfamethoxazole/Trimethoprim. Due to poor clinical response, on hospital day 5 Sulfamethoxazole/Trimethoprim was switched to Primaquine. She initially received lung protective ventilation but remained hypoxemic. Salvage therapies with airway pressure release ventilation, prone ventilation and nitric oxide were also used. On hospital day 6 the patient was noticed to have elevated amylase and lipase levels, her renal function had deteriorated, requiring renal replacement therapy. The patient’s liver function tests showed a cholestatic picture. Given the need to monitor both Primaquine and Nitric oxide effect on hemoglobin and possibility of methemoglobinemia, all ABG samples were drawn with co-oximetry. On hospital day number 7, the Methemoglobin level was 7.6% and Carboxyhemoglobin was 6.4%. There was an error message on the co-oximetry measurements and the blood obtained in the ABG syringe had a milky supernatant. Serum levels of triglycerides 2613mg/dL (normal on admission). Primaquine was discontinued and Nitric oxide was titrated down. The patient expired on day 13 of admission as a consequence of multi-organ failure.

DISCUSSION: Our patient was having adequate monitoring of her hemoglobin with co-oximetry, but the results obtained did not reflect the reality, since they were falsely elevated by the hypertriglyceridemia. The absorbance of the analyzer light in the cooximeter by homogenous sample is proportional to the absorbing substances.This is not true with high levels of the triglycerides which scatter the light and cause spectral interference leading to the erroneous reading.

CONCLUSIONS: By understanding the technology,we can interrupt the erroneous result on the ABG. In this case,elevated levels of triglycerides falsely affecting the absorption of methemoglobin.

1) Noskin GA, et al. Salvage therapy with clindamycin/primaquine for Pneumocystis carinii pneumonia. Clin Infect Dis,1992;14:183-8

2) Howdieshell TR, et al. Reliability of in vivo mixed venous oximetry during experimental hypertriglyceridemia. Crit Care Med,1992;20:999-1004

3) Spurzem JR, et al. Factitious methemoglobinemia caused by hyperlipemia Chest 1984;86;84-6

DISCLOSURE: The following authors have nothing to disclose: Veronica Brito, Peter Spiegler, Shweta Upadhyay

No Product/Research Disclosure Information

Winthrop University Hospital, Mineola, NY




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