Why did you set skin temperature at 37 °C, although it was used at 41-42 °C in humans?

Because we’d like to avoid complications, such as low temperature burn. Low temperature burn happens above 44°C in humans. In this study, we designed continuously heating the paws to collect blood samples whenever required. One researcher concluded that it was enough to arterialize peripheral venous blood by keeping skin temperature at 35°C1. Therefore we tried at 37°C. As we expected, we experienced no complications in this study.


Why was significant difference detected under metabolic acidosis in Pco2 between blood samples from arteries and arterialized peripheral vein?

I guess three reasons. First, respiratory compensation in metabolic acidosis mildly decrease arterial Pco2. Second, heating the paws may gain tissue metabolism rate and result in increase in venous Pco2. Third, vasoconstriction effect of NH4Cl in vitro was reported2,3 and it may impair the tissue perfusion and induce increase in venous Pco2.

Why were blood samples from saphenous vein better than that form cephalic vein?

I think because less of the muscles around the hindpaw is less subject to tissue metabolic effect4, that is, increase in venous Pco2.

Have you experienced any complications associated with the procedure?

No, I have not. Low temperature burn happens above 44°C in humans.

Could you please tell about the assessment of agreement in detail between arterial and arterialized peripheral venous blood, especially about criteria for “clinically acceptable agreement”?

We used a Bland-Altman plots which usually evaluate interchangeability between two analyzers, because neither “not significant difference” nor “high correlation” is enough to tell interchangeability. We determined those criteria based on quality control principles, that is, control samples should be measured within ±2 or 3 SDs from the mean5.

What is “proficiency testing”?

It is a external quality control system to check the accuracy of the analyzer and the proficiency of the technician in the laboratory. An unknown sample is periodically distributed to the laboratory, and they report the results, and the measurement skill in the laboratory is evaluated5.

Have you ever tried the procedure in clinical setting?

No, I have not yet. But I’d like to try with new heating device, such as heating box4 or heating pad6, more stable and appropriate for clinical setting than with lamps.

Have you ever tried the procedure in clinical setting?

No, I have not yet. But I’d like to try with new heating device, such as heating box4 or heating pad6, more stable and appropriate for clinical setting than with lamps.

How did you set in steady state when you collected blood samples?

We observed that the dog’s vital signs were stable at least 5 minutes until we collected blood samples.

Did you collect venous blood with stasis?

No. We collected venous blood with venipuncture and with free-flowing.

Where are arterio-venous anastomoses exactly?

According to the previous papers7, they are mainly on the skin.

Did you correct the measurement of blood gas with temperature? And what do you think temperature correction of values for blood gases?

No. I did not perform temperature correction because we cannot determine normal and appropriate values for blood gases not at 37°C5,8. Therefore we cannot tell the temperature-corrected values good or bad. We always evaluate blood gases at 37°C whatever temperature is.

How the dogs breathe when you experimentally induced metabolic acid-base disturbances? Did they breathe spontaneously or with mechanical ventilation?

Dogs breathed in room air spontaneously although they were intubated. We didn’t use ventilator.

How did you maintain anesthesia for such a long time?

We administered pentobarbital 5mg/kg intravenously intermittently, and with continuous infusion of ketamine.

How long did it take throughout one experiment?

It took about 12 hours for each experiment.

  1. Brooks D, Wynn V. Use of venous blood for pH and carbon-dioxide studies especially in respiratory failure and during anaesthesia. Lancet 1959;1:227-230.
  2. Wakabayashi I, Kukovetz WR, Groschner K. NH4Cl-induced contraction of porcine coronary artery involves activation of dihydropyridine-sensitive Ca2+ entry. Eur J Pharmacol 1996;299:139-147.
  3. Wakabayashi I, Sakamoto K, Hatake K, et al. Potentiating effect of NH4Cl on vasoconstriction in rat aorta. Biochem Biophys Res Commun 1991;178:808-814.
  4. Zello GA, Smith JM, Pencharz PB, et al. Development of a heating device for sampling arterialized venous blood from a hand vein. Ann Clin Biochem 1990;27 ( Pt 4):366-372.
  5. Malley WJ. Clinical Blood Gases: Assessment and Intervention, 2nd ed. St.Louis: Elsevier Saunders; 2005.
  6. Forster HV, Dempsey JA, Thomson J, et al. Estimation of arterial PO2, PCO2, pH, and lactate from arterialized venous blood. J Appl Physiol 1972;32:134-137.
  7. Linderman J, Fahey TD, Lauten G, et al. A comparison of blood gases and acid-base measurements in arterial, arterialized venous, and venous blood during short-term maximal exercise. Eur J Appl Physiol Occup Physiol 1990;61:294-301.
  8. Shapiro BA, Peruzzi WT, Templin R. Clinical Application of Blood Gases, 5th ed. St.Louis: Mosby; 1994.