R Parizkova

Differential effects of intravenous anesthetics on hepatosplanchnic microcirculation in rats: sidestream dark-field imaging study.

This study aimed to investigate the effects of intravenous anesthetics on hepatosplanchnic microcirculation in laparotomized mechanically ventilated rats using Sidestream Dark-field (SDF) imaging. Thirty male Wistar rats were divided into 5 groups (n = 6 each). All rats were initially anesthetized with 60 mg/kg pentobarbital (i.p.) for instrumentation. This was followed by either ketamine, propofol, thiopental, midazolam or saline+fentanyl (iv bolus over 5 min and then maintenance over 90 min). SDF imaging of the liver and distal ileum microcirculation was performed at the baseline and at t = 5, 35, 65 and 95 min. In propofol group there was increase of functional sinusoidal density (FSD) following induction (+25%, P < 0.05) and maintenance at t = 95 min (+10.3%, P < 0.05), in ketamine and midazolam group decrease of FSD was observed after induction (-20.4%, P < 0.05; -10.1%, P < 0.05) and during maintenance at t = 65 min (-11.6%, P < 0.05; -11.4%, P < 0.05) when compared to baseline. Following induction with propofol functional capillary density (FCD) of ileal longitudinal muscle layer increased (+10.6%, P < 0.05) and returned to baseline values during maintenance. Ketamine and midazolam decreased FCD of longitudinal layer after induction (-24.6%, P < 0.05; -21.1%, P < 0.05) and remained decreased during maintenance at t = 95 min (-10.8%, P < 0.05; -15.5%, P < 0.05). In thiopental and control group, changes in microcirculatory parameters were not significant throughout the study. In conclusion, intravenous anesthetics affect the hepatosplanchnic microcirculation differentially, propofol has shown protective effect on the liver and intestinal microcirculation.

Preserved cerebral microcirculation in early stages of endotoxemia in mechanically-ventilated rabbits

The purpose of our study was to evaluate changes of the cerebral microcirculation during the early stages of endotoxemia in mechanically-ventilated rabbits using Sidestream dark-field (SDF) imaging. Images were obtained using SDF imaging from the surface of the brain via craniotomy before and after rapid administration of a high dose of endotoxin or saline (control group). Although endotoxin shock was successfully induced, we have not found any significant alteration of the cerebral microcirculation during the shock. We speculate that either the model of sepsis with a rapid high dose of endotoxin does not reflect the usual progression of septic encephalopathy or some components other than cerebral microcirculatory alteration play a role at the early stage of septic encephalopathy and the cerebral microcirculation is still preserved. Further studies are needed to clarify our findings.

Comparison of cold crystalloid and colloid infusions for induction of therapeutic hypothermia in a porcine model of cardiac arrest

IntroductionLarge-volume cold intravenous infusion of crystalloids has been used for induction of therapeutic hypothermia after cardiac arrest. However, the effectiveness of cold colloids has not been evaluated. Therefore, we performed an experimental study to investigate the cooling effect of cold normal saline compared to colloid solution in a porcine model of ventricular fibrillation.MethodsVentricular fibrillation was induced for 15 minutes in 22 anesthetized domestic pigs. After spontaneous circulation was restored, the animals were randomized to receive either 45 ml/kg of 1°C cold normal saline (Group A, 9 animals); or 45 ml/kg of 1°C cold colloid solution (Voluven®, 6% hydroxyethyl starch 130/0.4 in 0.9% NaCl) during 20 minutes (Group B, 9 animals); or to undergo no cooling intervention (Group C, 4 animals). Then, the animals were observed for 90 minutes. Cerebral, rectal, intramuscular, pulmonary artery, and subcutaneous fat body temperatures (BT) were recorded. In the mechanical ex-vivo sub study we added a same amount of cold normal saline or colloid into the bath of normal saline and calculated the area under the curve (AUC) for induced temperature changes.ResultsAnimals treated with cold fluids achieved a significant decrease of BT at all measurement sites, whereas there was a consistent significant spontaneous increase in group C. At the time of completion of infusion, greater decrease in pulmonary artery BT and cerebral BT in group A compared to group B was detected (−2.1 ± 0.3 vs. -1.6 ± 0.2°C, and −1.7 ± 0.4 vs. -1.1 ± 0.3°C, p < 0.05, respectively). AUC analysis of the decrease of cerebral BT revealed a more vigorous cooling effect in group A compared to group B (−91 ± 22 vs. -68 ± 23°C/min, p = 0.046). In the mechanical sub study, AUC analysis of the induced temperature decrease of cooled solution revealed that addition of normal saline led to more intense cooling than colloid solution (−7155 ± 647 vs. -5733 ± 636°C/min, p = 0.008).ConclusionsIntravenous infusion of cold normal saline resulted in more intense decrease of cerebral and pulmonary artery BT than colloid infusion in this porcine model of cardiac arrest. This difference is at least partially related to the various specific heat capacities of the coolants.

Prolonged hypervolemic hemodilution decreases functional capillary density of ileal mucosa in pigs revealed by sidestream dark-field imaging

ObjectiveHemodilution changes the physical properties of blood by reducing its hematocrit and blood viscosity. We tested whether prolonged hypervolemic hemodilution (HHD) impairs functional capillary density (FCD) of ileal mucosa in healthy mechanically-ventilated pigs and if there is any correlation between changes in FCD of ileal and sublingual mucosas during HHD.MethodsSixteen domestic female pigs were anesthetized, mechanically-ventilated, and randomly assigned to the HHD (20 ml/(kg·h) Hartmann’s solution for 3 h) or fluid restrictive (5 ml/(kg·h) Hartmann’s solution for 3 h) group. Microcirculations of sublingual and ileal mucosas via ileostomy were visualized using sidestream dark-field (SDF) imaging at baseline conditions (t=0 h) and at selected time intervals of fluid therapy (t=1, 2, and 3 h).ResultsA significant decrease of ileal FCD (285 (278–292) cm/cm2) in the HHD group was observed after the third hour of HHD when compared to the baseline (360 (350–370) cm/cm2) (P<0.01). This trend was not observed in the restrictive group, where the ileal mucosa FCD was significantly higher after the third hour of fluid therapy as compared to the HHD group (P<0.01). No correlation between microhemodynamic parameters obtained from sublingual and ileal mucosas was found throughout the study.ConclusionsProlonged HHD established by crystalloid solution significantly decreased ileal villus FCD when compared to restrictive fluid regimen. An inappropriate degree of HHD can be harmful during uncomplicated abdominal surgery.