Optimal crystalloid volume ratio for blood replacement for maintaining hemodynamic stability and lung function: an experimental randomized controlled study

Abstract

Background Crystalloids are first line in fluid resuscitation therapy, however there is a lack of evidence-based recommendations on the volume to be administered. Therefore, we aimed at comparing the systemic hemodynamic and respiratory effects of volume replacement therapy with a 1:1 ratio to the historical 1:3 ratio. Methods Anesthetized, ventilated rats randomly included in 3 groups: blood withdrawal and replacement with crystalloid in 1:1 ratio (Group 1, n = 11), traditional 1:3 ratio (Group 3, n = 12) and a control group with no interventions (Group C, n = 9). Arterial blood of 5% of the total blood volume was withdrawn 7 times, and replaced stepwise with different volume rations of Ringer’s acetate, according to group assignments. Airway resistance (Raw), respiratory tissue damping (G) and tissue elastance (H), mean arterial pressure (MAP) and heart rate (HR) were assessed following each step of fluid replacement with a crystalloid (CR1-CR6). Lung edema index was measured from histological samples. Results Raw decreased in Groups 1 and 3 following CR3 ( p < 0.02) without differences between the groups. H elevated in all groups ( p < 0.02), with significantly higher changes in Group 3 compared to Groups C and 1 (both p = 0.03). No differences in MAP or HR were present between Groups 1 and 3. Lung edema was noted in Group 3 ( p < 0.05). Conclusions Fluid resuscitation therapy by administering a 1:1 blood replacement ratio revealed adequate compensation capacity and physiological homeostasis similar with no lung stiffening and pulmonary edema. Therefore, considering this ratio promotes the restrictive fluid administration in the presence of continuous and occult bleeding.

Editorial: Fluid Therapy in Animals: Physiologic Principles and Contemporary Fluid Resuscitation Considerations

“…Larger molecules (i.e., colloids) negligibly penetrate the GLX and distribute in a smaller intravascular volume than crystalloids which readily distribute throughout the entire intravascular space. Recent studies suggest that crystalloid-to-colloid ratios should range from 0.7 to 1.4:1 in contrast to older ratios (i.e., 1:3) ( 167 – 175 ) and that crystalloid-to-blood ratios > 1:1 produce perivascular edema, pulmonary parenchymal stiffness ( 176 ), impaired coagulation [ Boyd et al ; ( 177 , 178 )], increased blood loss ( 44 ), and increased vasopressor requirements ( 43 ). Disagreements favoring colloids over crystalloids rest more on their delayed diffusion than on their safety [( 44 , 50 – 53 ); Boyd et al ; ( 179 )], risk-benefit ratio ( Adamik and Yozova ) or cost.…”

“…Fluid that is filtered through the glycocalyx flows rapidly through narrow inter-endothelial cell breaks, thereby limiting interstitial protein back diffusion into the sub-glycocalyx space. The “Revised” Starling equation [( 11 ); Woodcock and Michel ; ( 189 )] has proven to be more consistent with experimental and clinical observations and suggests that (1) J v is far less than originally predicted; (2) Fluid is not normally reabsorbed from the venous end of the capillary during normal physiologic conditions (steady state no-reabsorption rule); (3) Tissue lymph drainage is the primary route for return of interstitial fluid to the circulation; (4) Interstitial fluid is reabsorbed from the interstitium when P c decreases until a new steady state is established ( 14 ); and (5) Crystalloid is almost as effective as a colloid (Col) administration for treating hypovolemia from blood loss ( 11 , 173 – 176 ). These revisions highlight the importance of GLX composition and integrity and the number of inter-endothelial cellular “breaks” (i.e., glycocalyx-junction-break model) in determining the effectiveness of fluid resuscitation ( 195 ).…”

Fluid Therapy in Pulmonary Disease: How Careful Do We Need to Be?

“…Management of intravascular volume deficits (hypovolemia) typically involves the administration of aliquots (25% of blood volume) of isotonic crystalloid fluids up to a rate of 90 mL/kg/h, which is below the experimental doses reported ( 11 ). Recent experimental work in a rat hemorrhage model comparing the effects of a 1:1 blood volume lost to replacement crystalloid ratio with a 1:3 ratio identified increased histologic lung edema scores and wet:dry lung weight, but there was no effect on PaO 2 ( 12 ). Despite this, it would seem that clinically, rates used in the acute setting for resuscitation have limited immediate effect on pulmonary function in the absence of pre-existent pulmonary inflammation or injury.…”

Immune response in fluid therapy with crystalloids of different ratios or colloid for rats in haemorrhagic shock

“…Haemorrhagic shock was induced by exsanguination. Total estimated blood volume (TEBV) was defined as 0.064 mL/g based on a previous study 6 and 50% of TEBV was removed using a 5 mL syringe. Fluid was administered to resuscitate through the left femoral vein using a syringe pump (Harvard Apparatus, Holliston, MA, USA) at 60 min after exsanguination.…”

“…Alternatively, synthetic colloid restores blood volume at a 1:1 ratio 4 . However, recent trials have demonstrated that less crystalloid is sufficient [5][6][7] . The trials have also showed that organ function was different, according to the type of fluid and amount of fluid, even though restoration of haemodynamic parameters was similar.…”