Burrows FA. Con: pH-stat Management of Blood Gases is Preferable to Alpha-stat in Patients undergoing Brain Cooling for Cardiac Surgery. J Cardiothorac Vasc Anesth. 1995; 9: 219-221.

Engelhardt W. Early Cerebral Functional Outcome after Coronary Artery Bypass Surgery using Different Acid-base Management during Hypothermic Cardiopulmonary Bypass. Acta Anesthesiol Scand. 1996; 40: 457-465.

Kern FH & Greeley WJ. Pro: pH-stat Management of Blood Gases is Not Preferable to Alpha-stat in patients
Undergoing Brain Cooling for Cardiac Surgery. J Cardiothorac Vasc Anesth. 1995; 9: 215-218.

Kofstad J. Blood Gases and Hypothermia: Some Theoretical and Practical Considerations. Scand J Clin Lab Invest (Suppl) 1996; 224: 21-26.
Abstract: There is much controversy about the optimal bloodgas management of hypothermic patients, whether the hypothermia is caused by accidents or induced before operations. The surgeons and anesthesiologists have acquired more clinical experience in recent years when operating on patients in hypothermia. The comparative physiology has given increased information about the blood gas strategy of heterothermic endotherms and poikilothermic ectotherms during lowering of their core temperature. There are two types of strategies which have been used in clinical medicine the last years in the blood gas management of patients in hypothermia: pH-stat method and alpha-stat method.

• In the pH-stat method, the arterial carbon dioxide tension (paCO2) is maintained at 5.3 kPa (40 mmHg) and the pH is maintained at 7.40 when measured at the actual temperature. It is then necessary to add CO2 to the inspired gas.

• In the alpha-method, the arterial carbon dioxide tension and the pH are maintained at 5.3 kPa and 7.40 when measured at +37 degrees C. When a patient is cooled down, the pH-value will increase and the pCO2-value and the pO2-value will decrease with lowering of the temperature if measured at the patients temperature. 

Both the pH-stat and alpha-stat strategies have theoretical disadvantages. For optimal myocardial function the alpha-stat method is the method of choice. The pH-stat method may result in loss of autoregulation in the brain (coupling of the cerebral blood flow with the metabolic rate in the brain). By increasing the cerebral blood flow beyond the metabolic requirements, the pH-stat method may lead to cerebral microembolisation and intracranial hypertension. In Norway, the alpha-stat strategy is the preferred method.

O’Dwyer C et al. Determinants of Cerebral Perfusion during Cardiopulmonary Bypass. J Cardiothorac Vasc
Anesth. 1996; 10: 54-64; quiz 65

Rahn H et al. Hydrogen Ion Regulation, Temperature, and Evolution. Am Rev Resp Dis. 1975; 112: 165- 172.

Reeves RB. An Imidazole Alphastat Hypothesis for Vertebrate Acid-Base Regulation: Tissue Carbon Dioxide Content and Body Temperature in Bullfrogs. Resp Physiol. 1972; 14: 219-236.

Robin ED, Bromberg PA & Cross CE. Some Aspects of the Evolution of Vertebrate Acid-Base Regulation. Yale Journal of Biology & Medicine. 1969; 41: 448-467.

Severinghaus JW & Astrup PB. The Development of Electrochemistry. Int Anes Clin. 1987; 25: 1-25.