Effect of dopamine on renal blood flow of baboon in endotoxin shock

Renal perfusion in sepsis: from macro- to microcirculation

The pathogenesis of sepsis-associated acute kidney injury is complex and likely involves perfusion alterations, a dysregulated inflammatory response, and bioenergetic derangements. Although global renal hypoperfusion has been the main target of therapeutic interventions, its role in the development of renal dysfunction in sepsis is controversial. The implications of renal hypoperfusion during sepsis probably extend beyond a simple decrease in glomerular filtration pressure, and targeting microvascular perfusion deficits to maintain tubular epithelial integrity and function may be equally important. In this review, we provide an overview of macro- and microcirculatory dysfunction in experimental and clinical sepsis and discuss relationships with kidney oxygenation, metabolism, inflammation, and function.

Renal Vascular Resistance in Sepsis

AIMS

To assess changes in renal vascular resistance (RVR) in human and experimental sepsis and to identify determinants of RVR.

METHODS

We performed a systematic interrogation of two electronic reference libraries using specific search terms. Subjects were animals and patients involved in experimental and human studies of sepsis and septic acute renal failure, in which the RVR was assessed. We obtained all human and experimental articles reporting RVR during sepsis. We assessed the role of various factors that might influence the RVR during sepsis using statistical methods.

RESULTS

We found no human studies, in which the renal blood flow (and, therefore, the RVR) was measured with suitably accurate direct methods. Of the 137 animal studies identified, 52 reported a decreased RVR, 16 studies reported no change in RVR, and 69 studies reported an increased RVR. Consciousness of animals, duration of measurement, method of induction of sepsis, and fluid administration had no effect on the RVR. On the other hand, on univariate analysis, size of the animals (p < 0.001), technique of measurement (p = 0.017), recovery after surgery (p = 0.004), and cardiac output (p < 0.001) influenced the RVR. Multivariate analysis, however, showed that only cardiac output (p = 0.028) and size of the animals (p = 0.031) remained independent determinants of the RVR.

CONCLUSIONS

Changes in RVR during sepsis in humans are unknown. In experimental sepsis, several factors not directly related to sepsis per se appear to influence the RVR. A high cardiac output and the use of large animals predict a decreased RVR, while a decreased cardiac output and the use of small animals predict an increased RVR.

Renal blood flow in sepsis

Introduction

To assess changes in renal blood flow (RBF) in human and experimental sepsis, and to identify determinants of RBF.

Method

Using specific search terms we systematically interrogated two electronic reference libraries to identify experimental and human studies of sepsis and septic acute renal failure in which RBF was measured. In the retrieved studies, we assessed the influence of various factors on RBF during sepsis using statistical methods.

Results

We found no human studies in which RBF was measured with suitably accurate direct methods. Where it was measured in humans with sepsis, however, RBF was increased compared with normal. Of the 159 animal studies identified, 99 reported decreased RBF and 60 reported unchanged or increased RBF. The size of animal, technique of measurement, duration of measurement, method of induction of sepsis, and fluid administration had no effect on RBF. In contrast, on univariate analysis, state of consciousness of animals (P = 0.005), recovery after surgery (P < 0.001), haemodynamic pattern (hypodynamic or hyperdynamic state; P < 0.001) and cardiac output (P < 0.001) influenced RBF. However, multivariate analysis showed that only cardiac output remained an independent determinant of RBF (P < 0.001).

Conclusion

The impact of sepsis on RBF in humans is unknown. In experimental sepsis, RBF was reported to be decreased in two-thirds of studies (62 %) and unchanged or increased in one-third (38%). On univariate analysis, several factors not directly related to sepsis appear to influence RBF. However, multivariate analysis suggests that cardiac output has a dominant effect on RBF during sepsis, such that, in the presence of a decreased cardiac output, RBF is typically decreased, whereas in the presence of a preserved or increased cardiac output RBF is typically maintained or increased.

Adrenergic vasopressor agents and mechanical ventilation for the treatment of experimental septic shock

OBJECTIVE

Vasopressor agents and mechanical ventilation are routine interventions for the treatment of sepsis complicated by hypotension. It was our hypothesis that such treatment singly or in combination increases the duration of survival.

DESIGN

Prospective, randomized, controlled study.

SETTING

University research laboratory.

SUBJECTS

Thirty male Sprague-Dawley rats anesthetized with intraperitoneal injection of pentobarbital.

INTERVENTIONS

Peritonitis was induced by cecal ligation and spillage of cecal contents into the abdominal cavity. The first phase of this study was performed on 15 spontaneously breathing Sprague-Dawley rats that were randomized to three groups of five animals each. One group received treatment with dopamine. The second group received norepinephrine. The third group received only the diluent as a placebo. Concentrations of the vasopressor agents were increased such that mean arterial pressure was maintained at approximately 80% of baseline values; the volumes infused were kept constant. For the second phase of this study, the grouping of animals and the techniques of study were identical, except that rats were mechanically ventilated.

MEASUREMENTS AND MAIN RESULTS

Mean arterial pressure was best maintained with norepinephrine. However, no statistically significant differences in duration of survival, cardiac index, arterial blood lactate concentration, or arterial and venous PCO2 and PO2 values were identified between groups. With mechanical ventilation, survival was prolonged (p < .01). Survival was increased from an average of 291 mins to 342 mins with dopamine, from 257 mins to 352 mins in placebo controls, and from 280 mins to 329 mins with norepinephrine. Again, no significant differences in hemodynamic and blood gas measurements, or in the duration of survival between vasopressor-treated and control animals were documented.

CONCLUSIONS

No benefit or detriment was demonstrated when vasopressor agents were administered to sustain arterial pressure in the course of experimental peritonitis in this murine model of septic shock. This finding contrasted with highly significant prolongation of survival when animals were mechanically ventilated. There was no evidence that routine vasopressor therapy, under these controlled experimental conditions in rats, improved duration of survival.