Effects of Hyperventilation on Venous-Arterial Bicarbonate Concentration Difference: A Possible Pitfall in Venous Blood Gas Analysis

Objectives: Recent reports on venous blood gas analysis have shown that venous bicarbonate concentration is useful in the evaluation of the body acid-base status. Most of these reports have been based on the Bland-Altman analysis comparing arterial and venous blood gas values. We intended to elucidate any factors that decrease the agreement between venous and arterial bicarbonate concentrations, which might impair the usefulness of venous blood gas analysis. Methods: Healthy volunteers and patients with various diseases (n = 141) were evaluated by simultaneous arterial and venous blood sampling and Bland-Altman analysis. The venous-arterial bicarbonate concentration difference was compared between healthy volunteers and untreated respiratory alkalosis patients. Intentional hyperventilation (30 or 60 breaths/min, for 3 min) was also performed on 6 healthy volunteers and the venous-arterial bicarbonate concentration difference was evaluated. Results: The relative average bias in bicarbonate concentration was 2.00 mEq/l with venous bicarbonate higher than arterial bicarbonate with 95% limits of agreement of ±4.15 mEq/l. Hyperventilation challenges increased the venous-arterial bicarbonate concentration difference in an intensity-dependent manner. The venous-arterial bicarbonate concentration difference was higher in untreated respiratory alkalosis patients than in healthy volunteers (P Conclusion: Although venous bicarbonate may be useful to evaluate the body acid-base status, hyperventilation increases the venous-arterial bicarbonate concentration difference. Physicians should keep this phenomenon in mind.

Serous cystadenocarcinoma of the mesentery in a man:case report and review of literature

In February 2007,a 41-year-old Japanese male was admitted to our hospital with increasing upper abdominal pain.A contrast-enhanced computed tomography(CT)scan of the abdomen demonstrated a well-demarcated,hypodense cystic mass with a thickened wall in the mesocolon.The laboratory results were within normal limits,except for increased carcinoembryonic antigen,carbohydrate antigen 19-9,DUPAN-2 and SPAN-1.The patient was diagnosed as having a mesenteric malignant cyst,and during a laparotomy,a right hemicolectomy with mesenteric cystectomy was performed without rupture in March 2007.In the microscopic findings,there was a well-differentiated adenocarcinoma in the inner surface of the cyst and in the fibrous connective tissue of the hypertrophic cystic wall.The tumor cells were immunohistochemically reactive to cytokeratin(CK)7,CK18 and CK20.No remnant of the malignancy was detected in the resected margin of the colon,cyst,liver or peritoneum nor was an uptake detected in an 18[F]-fluorodeoxyglucose positron emission tomography/CT examination of other organs.Finally,the malignancy was concluded to be a serous cystadenocarcinoma of the mesentery.Nineteen months after the operation,the patient died from peritonitis carcinomatosa due to a small intestine rupture.This report suggests mesenteric cystadenocarcinomas originating in the ovary,oviduct and intestinal mucosa,but these were ruled out in our patient.In this report,we discuss a case of the malignant transformation of a cyst into adenocarcinoma,which to our knowledge has never been previously reported in a male patient.