The anion study: effect of different crystalloid solutions on acid base balance, physiology, and survival in a rodent model of acute isovolaemic haemodilution

Abstract

Background: Commercially available crystalloid solutions used for volume replacement do not exactly match the balance of electrolytes found in plasma. Large volume administration may lead to electrolyte imbalance and potential harm. We hypothesised that haemodilution using solutions containing different anions would result in diverse biochemical effects, particularly on acid-base status, and different outcomes.

Methods: Anaesthetised, fluid-resuscitated, male Wistar rats underwent isovolaemic haemodilution by removal of 10% blood volume every 15 min, followed by replacement with one of three crystalloid solutions based on acetate, lactate, or chloride. Fluids were administered in a protocolised manner to achieve euvolaemia based on echocardiography-derived left ventrical volumetric measures. Removed blood was sampled for plasma ions, acid-base status, haemoglobin, and glucose. This cycle was repeated at 15-min intervals until death. The primary endpoint was change in plasma bicarbonate within each fluid group. Secondary endpoints included time to death and cardiac function.

Results: During haemodilution, chloride-treated rats showed significantly greater decreases in plasma bicarbonate and strong ion difference levels compared with acetate- and lactate-treated rats. Time to death, total volume of fluid administered: chloride group 56 (3) ml, lactate group 62 (3) ml, and acetate group 65 (3) ml; haemodynamic and tissue oxygenation changes were, however, similar between groups.

Conclusions: With progressive haemodilution, resuscitation with a chloride-based solution induced more acidosis compared with lactate- and acetate-based solutions, but outcomes were similar. No short-term impact was seen from hyperchloraemia in this model.

Keywords: acid-base imbalance; bicarbonate; isotonic solutions.

Fig 1

Study plan. Bv, 10% blood volume; LVIDD, left ventricular internal diameter in diastole.

Fig 2

Impact of chloride-, acetate-, and lactate-based fluids on (a) Kaplan–Meier plot of survival time with progressive haemodilution, (b) volume required to maintain ventricular filling (median, inter-quartile and full range), (c) haemoglobin (mean and sd), and (d) serum glucose (mean and sd). AS, acetate-based solution; CS, chloride-based solution; LS, lactate-based solution. n = 15 per group.

Fig 3

Impact of chloride-, acetate-, and lactate-based fluids on serum levels of (a) chloride, (b) bicarbonate, (c) lactate, (d) arterial pH, (e) strong ion difference (SID), and (f) anion gap. All data are mean and sd. *Significant differences between groups, P < 0.05. AS, acetate-based solution; CS, chloride-based solution; LS, lactate-based solution. n = 15 per group.

Fig 4

Impact of chloride-, acetate-, and lactate-based fluids on (a) arterial carbon dioxide tension, (b) serum potassium, and (c) serum sodium. All data are mean and sd. AS, acetate-based solution; CS, chloride-based solution; LS, lactate-based solution. n = 15 per group.

Fig 5

Impact of chloride-, acetate-, and lactate-based fluids on (a) stroke volume, (b) heart rate, (c) blood pressure, (d) arterial oxyhaemoglobin saturation, and (e) skeletal muscle tissue oxygen tension. All data are mean and sd. AS, acetate-based solution; LS, lactate-based solution; S, chloride-based solution; tPO₂, muscle tissue oxygen tension. n = 15 per group.