The influence of haemorrhage and fluid resuscitation with either Plasma-Lyte A or Ringer's Lactate in Beagle dogs under sevoflurane anaesthesia-part 1: Macrocirculation.

OBJECTIVE

To compare macrocirculatory effects of haemorrhage followed by fluid resuscitation with Plasma-Lyte A (PA) or Ringer's Lactate (RL) crystalloid solution in dogs under sevoflurane anaesthesia.

STUDY

DESIGN

Single-centre, randomised, blinded, experimental study.

ANIMALS: A group of 12 adult, healthy, intact, purpose-bred Beagle dogs.

METHODS

Dogs were instrumented under sevoflurane anaesthesia. Heart rate, cardiac output (CO), and mean arterial blood pressure (MAP) were measured at baseline, after removing 30 mL kg-1 of blood over 15 minutes [hypovolaemia (HV)], and after each of two boluses (B1 and B2) of either 10 mL kg-1 PA or RL administered intravenously over 10 minutes. Data were compared using a linear mixed model with group and time points as fixed factors and dogs as a random factor, and corrections for multiple comparisons. A p value < 0.05 was considered significant.

RESULTS

There were no significant differences between treatments. Compared with HV, CO increased in both groups at B1: RL [0.57 (0.23-0.91) L minute-1 (estimated difference ± 95% confidence interval), p < 0.001] and PA [0.37 (0.03-0.7) L minute-1, p = 0.030], and at B2: RL [0.88 (0.54-1.2), p < 0.001] and PA [0.66 (0.23-0.91) L minute-1, p < 0.001]. The increase of MAP in RL was significant at B1 [15 (1-29) mmHg, p < 0.028] and B2 [16 (2-30) mmHg, p < 0.016] compared with HV, while MAP in PA was not significantly different at B1 [3 (-11 to 17) mmHg, p = 0.995] and B2 [4 (-9 to 18) mmHg, p = 0.943] compared with HV.

CONCLUSIONS AND CLINICAL RELEVANCE: In this small experimental study, both fluids tested led to a clinically significant increase in CO. No consistent increase in MAP was observed across fluid types. Alterations in MAP should not be used as a surrogate for flow variables to assess fluid responsiveness.