Sonographic real-time imaging of tissue perfusion in a porcine haemorrhagic shock model

Effects of fluids vs. vasopressors on spinal cord microperfusion in hemorrhagic shock induced ischemia/reperfusion

OBJECTIVE

Spinal cord injury induced by ischemia/reperfusion is a devastating complication of aortic repair. Despite developments for prevention and treatment of spinal cord injury, incidence is still considerably high majorly impacting patient outcome. Microcirculation is paramount for tissue perfusion and oxygen supply and often dissociated from macrohemodynamic parameters used to guide resuscitation. Effects of fluids vs. vasopressors in the setting of hemodynamic resuscitation on spinal cord microperfusion are unknown. Aim of this study was to compare the effects of vasopressor and fluid resuscitation on spinal cord microperfusion in a translational acute pig model of hemorrhagic shock induced ischemia/reperfusion injury.

METHODS

We designed this study as prospective randomized explorative large animal study. We induced hemorrhagic shock in 20 pigs as a model of global ischemia/reperfusion injury. We randomized animals to receive either fluid or vasopressor resuscitation. We measured spinal cord microperfusion using fluorescent microspheres as well as laser-Doppler probes. We monitored and analyzed macrohemodynamic parameters and cerebrospinal fluid pressure.

RESULTS

Spinal cord microperfusion decreased following hemorrhagic shock induced ischemia/reperfusion injury. Both fluids and vasopressors sufficiently restored spinal cord microperfusion. There were no important changes between groups (percentage changes compared to baseline: fluids 14.0 (0.31-27.6) vs. vasopressors 24.3 (8.12-40.4), p = .340). However, cerebrospinal fluid pressure was higher in animals receiving fluid resuscitation (percentage changes compared to baseline: fluids 27.7 (12.6-42.8) vs. vasopressors -5.56 ((-19.8)-8.72), p = .003). Microcirculatory resuscitation was in line with improvements of macrohemodynamic parameters.

CONCLUSIONS

Both, fluids and vasopressors, equally restored spinal cord microperfusion in a porcine acute model of hemorrhagic shock induced ischemia/reperfusion injury. However, significant differences in cerebrospinal fluid pressure following resuscitation were present. Future studies should evaluate these effects in perfusion disruption induced ischemia/reperfusion conditions of microcirculatory deterioration.

Renal Microcirculation and Function in a Pig Model of Hemorrhagic Shock Resuscitation with Norepinephrine

RATIONALE

Norepinephrine (NE) is commonly used in combination with fluid during resuscitation of hemorrhagic shock, however its impact on kidney microcirculation, oxygenation and function is still unknown in this setting.

OBJECTIVES

During hemorrhagic shock resuscitation, does a combination of fluid and norepinephrine affect kidney oxygenation tension, kidney microcirculatory perfusion and 48-hour kidney function, as compared to fluid alone?

METHODS

Hemorrhagic shock was induced in 24 pigs and 8 pigs were included as sham. Resuscitation of hemorrhagic shock was performed, using a closed-loop device, either by fluid alone (0.9% NaCl, Fluid group) or associated with the administration of NE at two doses (moderate dose: mean rate of 0.64 µg.kg-1.min-1 and high dose: mean rate of 1.57 µg.kg-1.min-1) in order to obtain SAP (systolic arterial pressure) target of 80-90 mmHg. Resuscitation was followed by transfusion of the withdrawn blood.

MEASUREMENTS AND MAIN RESULTS

The amount of fluid required to reach SAP target was lower in NE groups than in Fluid group with subsequent less hemodilution. Norepinephrine restored kidney microcirculation, oxygenation, and function in a manner comparable to that achieved with fluid resuscitation alone. There were no histological differences among animals resuscitated with Fluid or with NE.

CONCLUSION

In pigs with hemorrhagic shock, resuscitation with a combination of NE and fluid restored kidney microcirculation and oxygenation, as well as renal function, in a manner comparable to fluid resuscitation alone and without differences between the two NE doses. NE administration led to a fluid volume sparing effect with subsequently less hemodilution.