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Septic shock is frequently associated with metabolic acidosis derived from increased lactic acid production and infusion of sodium chloride-based resuscitation fluids. Although the impact of hyperchloraemic acidosis on outcome is still not fully understood, avoiding such a condition is desirable. The hypothesis of the present study was that resuscitation with saline-based tetrastarch solutions results in higher plasma chloride and lower base excess levels as compared with either balanced tetrastarch or crystalloid solutions in ovine endotoxaemic shock.
Thirty-one awake healthy ewes received a continuous infusion of Salmonella typhosa endotoxin started at 5 ng/kg/minute, which was doubled every hour until the mean arterial pressure (MAP) fell below 65 mmHg. Thereafter, sheep were randomized to receive either balanced 6% HES 130/0.4; saline-based 6% HES 130/0.4 (both HES solutions were infused up to 50 ml/kg); balanced crystalloids; or no fluids. Fluid resuscitation was guided to optimize central venous pressure (8 to 12 mmHg), pulmonary arterial occlusion pressure (12 to 15 mmHg) and mixed-venous oxygen saturation (≥65%). Norepinephrine was infused to establish a MAP of 70 ± 5 mmHg, if necessary. Haemodynamic variables and blood gas analyses were determined hourly throughout the study period. Animals surviving the 12-hour intervention period were deeply anaesthetized and killed.
Haemodynamic variables were comparable between groups. Plasma chloride concentrations were significantly higher, and oximetry-corrected base excess was lower in the saline-based tetrastarch group as compared with the balanced tetrastarch or balanced crystalloid group over the whole interventional period (each P < 0.05). Whereas arterial pCO2 was lowest in the saline-based tetrastarch group (each P < 0.05), there were no differences between treatment groups in arterial pH.
As compared with balanced tetrastarch or crystalloid solutions, saline-based tetrastarch infusion is associated with hyperchloraemic acidosis, which is compensated by hyperventilation in awake, endotoxaemic sheep.