Changes in oxygen content and acid-base balance in arterial and portal blood in response to the dietary electrolyte balance in pigs during a 9-h period after a meal.

The effect of two dietary electrolyte balance (dEB, Na+ + K+ - Cl-) levels on arterial and portal blood oxygen content, blood pH, and acid-base status in pigs was studied during a 9-h period after a meal, using a crossover experimental design. The dEB levels were established by changing the Cl- level in the diets. Four pigs with a mean weight of 45 kg were surgically fitted with catheters in the carotid artery and portal vein. Two dEB levels (-100 and 200 mEq/kg) were evaluated in two periods of 1 wk each. Feed was given at 2.6 times the maintenance requirement for energy in two meals per day. Water was freely available. Blood samples were taken at 0, 0.5, 1, 1.5, 2, 3, 4, 6, and 9 h after feeding. Blood hemoglobin; O2 pressure; O2 saturation; O2 content; pH; PCO2; HCO3-; base excess; and Na+, K+, and Cl- contents were measured. Oxygen contents in arterial and portal blood were lower (P < 0.008) in the -100 mEq/kg group (5.78 and 4.82 mmol/L respectively) compared to the 200 mEq/kg group (6.18 and 4.99 mmol/L respectively). This was related to the lower hemoglobin content in the blood of animals in the -100 mEq/kg group. Arterial and portal blood pH were lower (P < 0.003) at -100 mEq/kg (7.46 and 7.37) than at 200 mEq/kg (7.49 and 7.43). The difference in blood pH between the two groups was sustained throughout the sampling period. The average values of arterial and portal blood for base excess and HCO3- content were higher (P < 0.001) at high dEB (6.96 and 31.0 mmol/L, respectively, for -100 mEq/kg and 12.54 and 35.9 mmol/ L, respectively, for 200 mEq/kg). The Na+ concentration in the blood was increased and K+ and Cl- concentrations were decreased (P < 0.02) by increasing dEB from -100 mEq/kg to 200 mEq/kg. Blood electrolyte balance level was higher (P < 0.001) in the 200 mEq/kg dEB group than in the -100 mEq/kg dEB group. In conclusion, dEB changed blood oxygen content and pH, and influenced the acid-base buffer system in pigs. Also, within each group, pigs maintained a relatively constant blood pH level during the 9-h period after feeding.