A remission spectroscopy system for in vivo monitoring of hemoglobin oxygen saturation in murine hepatic sinusoids, in early systemic inflammation

Spectrophotometric assessment of bowel perfusion during low anterior resection: a prospective study

Good perfusion of the bowel and a tension-free anastomosis are the two main prerequisites for an uneventful anastomotic healing in rectal surgery. This prospective cohort study investigates the noninvasive intraoperative spectrophotometric assessment of the bowel perfusion using a device called “Oxygen to See” (O2C^®). Forty patients, planned for low anterior resection, were prospectively enrolled in this study to undergo an intraoperative spectrophotometric assessment of the bowel. Three different O2C^® parameters were collected from the colonic and the rectal stumps before fashioning the anastomosis: SO2 (capillary venous oxygen saturation), rHb (relative hemoglobin amount), and flow (blood flow velocity). Bowel perfusion was also assessed with the cold-steel-test (CST), which involves severing the colic marginal artery of Drummond at the tip of the colon stump. The data collected from the spectrophotometric measurement and the CST were analyzed for correlation of both methods with respect to each other and to the outcome of the anastomosis. Nine patients were excluded due to different reasons, thus leaving 31 patients for statistical analysis. Three flow parameters collected at the colonic stump significantly predicted an anastomotic leak (p: 0.0057; p: 0.0250; p: 0.0404). One rHb parameter collected at the rectal stump correlated weakly with the anastomotic outcome (p: 0.0768). The CST did not correlate significantly with anastomotic leak (p: 0.1195), but showed significant correlations to some rHb values. Intraoperative noninvasive spectrophotometric measurement is feasible and could be a useful method in assessing bowel perfusion before fashioning a colorectal anastomosis.

Laser Doppler spectroscopy of testes after unilateral orchiopexy

OBJECTIVE

Undescended testes are the most common urogenital malformation in boys. Impaired microcirculation is among other factors addressed as a potential complication of surgery and scar formation, leading to long-term suboptimal results.

OBJECTIVE

Our aim was to compare the postoperative microcirculation in operated versus non-operated contralateral testis groups after unilateral orchiopexies versus a healthy control cohort.

METHODS

Ninety-nine consecutive patients were included after unilateral orchiopexy procedures at the age of 3.5 years (±2.9 years) at a single center for pediatric surgery. Eight-five patients were examined with a combination of laser Doppler (blood flow determination) and white-light spectroscopy (oxygen saturation and hemoglobin amount determinations) to determine the microcirculation at two different depth levels non-invasively. All relevant surgery data were obtained retrospectively.

RESULTS

The right side was operated in 53.5% of cases. Previous hormone treatment had been prescribed in 46.5%. There were no significant differences in perfusion measurements between patients with previous hormone therapy and patients without. There was no significant difference in age and clinical pubertal stage between groups; however, 65% of patients underwent surgery after their second birthday. When comparing oxygen saturation (So2), relative hemoglobin (rHb), flow, and velocity in the operated testis with the contralateral testis of the same patients, we found significantly higher flows and velocities for the contralateral testes (p = 0.041, p = 0.022). Similar higher flows and velocities were found in the healthy controls (p < 0.001). The differences between healthy controls and contralateral testis that were not operated on did not reach statistical significance. There was no difference in measurements at 2 mm depth (skin and subcutaneous tissue) between groups to rule out systemic or capillary differences.

DISCUSSION

Important limitations include the limited and relatively heterogeneous samples that were obtained for follow-up and retrospective surgery data collection. An additional limitation is missing presurgical data, which we hope to obtain in future studies. Hormonal data or bone age could not be obtained for study reasons. The age in our study was on average above the recommended age for orchiopexy in Germany (6-12 months), which could also restrict generalizability. In terms of complications, we observed reascending testes within the range but a rather high incidence of wound infections. The combination of Doppler and white-light spectroscopy was easily applicable and produced reliable data at 2 and 8 mm depth simultaneously in a standardized setting.

CONCLUSIONS

After orchiopexy, differences were found in the microcirculation between the operated and contralateral testes or healthy controls. It remains unclear if this is an effect of primary disease or surgery. The microcirculation of contralateral testes was also seemingly different from controls. This is most likely not a consequence of surgery alone, but a common problem for both testes in the affected patients.

Phosphodiesterase-4 inhibition with rolipram attenuates hepatocellular injury in hyperinflammation in vivo and in vitro without influencing inflammation and HO-1 expression

Objective:

To investigate the impact of the phophodiesterase-4 inhibition (PD-4-I) with rolipram on hepatic integrity in lipopolysaccharide (LPS) induced hyperinflammation.

Materials and Methods:

Liver microcirculation in rats was obtained using intravital microscopy. Macrohemodynamic parameters, blood assays, and organs were harvested to determine organ function and injury. Hyperinflammation was induced by LPS and PD-4-I rolipram was administered intravenously one hour after LPS application. Cell viability of HepG2 cells was measured by EZ4U-kit based on the dye XTT. Experiments were carried out assessing the influence of different concentrations of tumor necrosis factor alpha (TNF-α) and LPS with or without PD-4-I.

Results:

Untreated LPS-induced rats showed significantly decreased liver microcirculation and increased hepatic cell death, whereas LPS + PD-4-I treatment could improve hepatic volumetric flow and cell death to control level whithout influencing the inflammatory impact. In HepG2 cells TNF-α and LPS significantly reduced cell viability. Coincubation with PD-4-I increased HepG2 viability to control levels. The heme oxygenase 1 (HO-1) pathway did not induce the protective effect of PD-4-I.

Conclusion:

Intravenous PD-4-I treatment was effective in improving hepatic microcirculation and hepatic integrity, while it had a direct protective effect on HepG2 viability during inflammation.

[Effects of physical stimulation of spontaneous arteriolar vasomotion on microcirculation and the immune system in diabetes and impaired wound healing]

BACKGROUND

Whether and to what extent the complementary use of a biorhythm-defined physical stimulation of insufficient spontaneous arteriolar vasomotion contributes to increasing the therapeutic success of established treatment concepts were examined.

MATERIALS AND METHODS

In a placebo-controlled study on a biometrically defined sample of older diabetes patients with impaired wound healing, measurements of representative features of the functional status of the microcirculation and the immune system were investigated using high-resolution methods (intravital microscopy, reflective spectrometry, white light spectroscopy combined with laser Doppler microflow measurements). The stimulation signal corresponding to physiological spontaneous arteriolar vasomotion was transmitted using an electromagnetic alternating field of low magnetic flux density.

RESULTS

During the 27-day treatment and observation period, a complementary treatment effect of the applied biorhythm-defined physical vasomotion stimulation could be detected.

Rolipram improves renal perfusion and function during sepsis in the mouse

Microcirculatory dysfunction is correlated with increased mortality among septic patients and is believed to be a major contributor to the development of acute kidney injury (AKI). Rolipram, a selective phosphodiesterase 4 (PDE4) inhibitor, has been shown to reduce microvascular permeability and in the kidney, increase renal blood flow (RBF). This led us to investigate its potential to improve the renal microcirculation and preserve renal function during sepsis using a murine cecal ligation and puncture (CLP) model to induce sepsis. Rolipram, tested at doses of 0.3-10 mg/kg i.p., acutely restored capillary perfusion in a bell-shaped dose-response effect with 1 mg/kg being the lowest most efficacious dose. This dose also acutely increased RBF despite transiently decreasing mean arterial pressure. Rolipram also reduced renal microvascular permeability. It is noteworthy that delayed treatment with rolipram at 6 hours after CLP restored the renal microcirculation, reduced blood urea nitrogen and serum creatinine, and increased glomerular filtration rate at 18 hours. However, delayed treatment with rolipram did not reduce serum nitrate/nitrite levels, a marker of nitric oxide production, nor reactive nitrogen species generation in renal tubules. These data show that restoring the microcirculation with rolipram, even with delayed treatment, is enough to improve renal function during sepsis despite the generation of oxidants and suggest that PDE4 inhibitors should be evaluated further for their ability to treat septic-induced AKI.

Microcirculation Under an Elastic Bandage During Rest and Exercise - Preliminary Experience With the Laser-Doppler Spectrophotometry System O2C

There is an abundace of studies on the influence of rest and exercise as well as external compression on cutaneous, subcutaneous and muscle tissue blood flow using different measurement techniques. As a novel approach, we simultaneously examined the influence of a custom- made elastic thigh bandage on cutaneous and subcutaneous venous blood oxygenation (SO2), postcapillary venous filling pressures (rHb) and blood flow (flow) using the non-invasive laser- Doppler spectrophotometry system "Oxygen-to-see(O2C)". Parameters were obtained in 20 healthy volunteers in 2 mm and 8 mm tissue depth during rest, 5 and 10 minutes of moderate bicycle exercise following a 10-minute recovery period. Without the bandage, results matched the known physiological changes indicating higher blood backflow from superficial and deep veins. Underneath the elastic bandage, we observed lower post-capillary filling pressures during exercise. However, after the bandage was removed in the post-exercise period, all obtained parameters of microcirculation remained increased, indicating a higher amount of local venous blood volume in this area. Our observations might be the result of external compression, thermoregulatory and exercise-dependent vascular mechanisms. With the O2C device, a promising new non- invasive technique of measuring local microcirculation in soft tissue exists. This study gives new insights in the field of non-invasive diagnostics with special regard to the influence of elastic bandages on local microcirculation. Key PointsIt can be demonstrated that a novel non-invasive laser-Doppler spectrophotometry system allows the determination of capillary-venous microcirculation in an in-vivo study during exercise-rest cycles.The results received with this technique indicate that a) without an elastic thigh bandage, turnover rates of capillary and post-capillary microperfusion in skin and subcutaneous fat tissue increase under physical exertion, b) skin blood flow decreases while subcutaneous blood flow remained constant in the subsequent recovery phase. While wearing the bandage, c) venous back flow during exercise is increased, whereas d) in the recovery phase, microcirculation remained increased in both tissue depths after removing the bandage.In conclusion, the elastic bandage has a negative impact on local microcirculation and capillary-venous back flow, which is possibly due to a displacement of blood volume into the deep venous system and heat accumulation impairing the thermoregulatory response at the same time.

Development of oxidative stress in the peritubular capillary microenvironment mediates sepsis-induced renal microcirculatory failure and acute kidney injury

Acute kidney injury is a frequent and serious complication of sepsis. To better understand the development of sepsis-induced acute kidney injury, we performed the first time-dependent studies to document changes in renal hemodynamics and oxidant generation in the peritubular microenvironment using the murine cecal ligation and puncture (CLP) model of sepsis. CLP caused an increase in renal capillary permeability at 2 hours, followed by decreases in mean arterial pressure, renal blood flow (RBF), and renal capillary perfusion at 4 hours, which were sustained through 18 hours. The decline in hemodynamic parameters was associated with hypoxia and oxidant generation in the peritubular microenvironment and a decrease in glomerular filtration rate. The role of oxidants was assessed using the superoxide dismutase mimetic/peroxynitrite scavenger MnTMPyP [Mn(III)tetrakis(1-methyl-4-pyridyl)porphyrin]. At 10 mg/kg administered 6 hours after CLP, MnTMPyP did not alter blood pressure, but blocked superoxide and peroxynitrite generation, reversed the decline in RBF, capillary perfusion, and glomerular filtration rate, preserved tubular architecture, and increased 48-hour survival. However, MnTMPyP administered at CLP did not prevent capillary permeability or the decrease in RBF and capillary perfusion, which suggests that these early events are not mediated by oxidants. These data demonstrate that renal hemodynamic changes occur early after sepsis and that targeting the later oxidant generation can break the cycle of injury and enable the microcirculation and renal function to recover.

Actinonin, a meprin A inhibitor, protects the renal microcirculation during sepsis

Sepsis-induced acute kidney injury occurs in 20% to 50% of septic patients and nearly doubles the mortality rate of sepsis. Because treatment in the septic patient is usually begun only after the onset of symptoms, therapy that is effective even when delayed would have the greatest impact on patient survival. The metalloproteinase meprin A, an oligomeric complex made of α- and β-subunits, is highly expressed at the brush-border membranes of the kidney and capable of degrading numerous substrates including extracellular matrix proteins and cytokines. The goal of the present study was to compare the therapeutic potential of actinonin, an inhibitor of meprin A, when administered before and after the onset of sepsis. Mice were treated with actinonin at 30 min before or 7 h after induction of sepsis by cecal ligation and puncture (CLP). Intravital videomicroscopy was used to image renal peritubular capillary perfusion and reactive nitrogen species. Actinonin treatment 30 min before CLP reduced IL-1β levels and prevented the fall in renal capillary perfusion at 7 and 18 h. Actinonin also prevented the fall in renal capillary perfusion even when administered at 7 h after CLP. In addition, even late administration of actinonin preserved renal morphology and lowered blood urea nitrogen and serum creatinine concentrations. These data suggest that agents such as actinonin should be evaluated further as possible therapeutic agents because targeting both the early systemic and later organ-damaging effects of sepsis should have the highest likelihood of success.

Intraoperative monitoring of cerebral microcirculation and oxygenation--a feasibility study using a novel photo-spectrometric laser-Doppler flowmetry

BACKGROUND

The present study assesses the utility of a novel invasive device (O2C-, oxygen-to-see-device) for intraoperative measurement of the cerebral microcirculation. CO2 vasoreactivity during 2 different propofol concentrations was used to investigate changes of capillary venous cerebral blood flow (rvCBF), oxygen saturation (srvO2), and hemoglobin concentration (rvHb) during craniotomy.

METHODS

Thirty-four patients were randomly assigned to a low propofol (4 mg/kg/h) versus a high propofol (6 mg/kg/h) group. A fiberoptic probe was applied on the cortex next to the surgical site. Measurements were performed during lower (35 mm Hg) and higher (45 mm Hg) levels of partial pressure of carbon dioxide (paCO2). Arterio-venous difference in oxygen concentration (avDO2) and approximated cerebral metabolic rate of oxygen (aCMRO2) were calculated for each paCO2 state. Linear models were fitted to test changes of end points in response to paCO2 and propofol concentration.

RESULTS

In comparison to the lower levels of paCO2, higher levels of paCO2 increased rvCBF (P<0.001), and srvO2 (P=0.002). RvHb remained unchanged during measurements (P=0.325). Calculated avDO2 decreased with increasing paCO2 (P<0.001), whereas aCMRO2 did not change during the study (P=0.999). Propofol concentration had no effect on measured or calculated end points.

CONCLUSIONS

Increase of rvCBF by paCO2 indicates a preserved CO2 reactivity independent of propofol anesthesia. The consecutive rise in srvO2 implies enhanced oxygen availability due to vasodilatation. Unchanged rvHb represents constant venous hemoglobin concentration. As expected, calculated avDO2 decreases with increased paCO2, whereas aCMRO2 remains unchanged. Despite the promising technical approach, the technology needs validation and further investigation for usage during neurosurgery.

The impact of a micro-lightguide spectrophotometer on the intraoperative assessment of hepatic microcirculation: a pilot study

INTRODUCTION

The intraoperative measurement of the peripheral microperfusion after liver transplantation is connected with quite an effort and a continuous evaluation in the postoperative follow up is not possible till now.

PATIENTS AND METHODS

Before mobilization of the liver during surgical intervention the following parameters were measured on the surface of the right (segment 7/8) and the left (segment 2/3) liver lobe with a probe, combining laser-Doppler-flowmetry and tissue-spectrometry: the oxygen saturation (SO2), the relative capillary hemoglobin concentration (rHB), the blood flow (flow) and the blood flow velocity (velo). In addition the peripheral oxygen saturation (SPO2), the central venous pressure (ZVP), the positive endexspiratory pressure (PEEP) and the hemoglobin (HB) were documented.

RESULTS

9 patients (median age 75 years) were included in the study. SPO2, ZVP, PEEP and HB were regular. The parameters SO2, rHB, flow and velo showed no significant changes between the right and the left liver lobe.

CONCLUSIONS

The O2C-method allows a reproducible intraoperative evaluation of the hepatic microcirculation.

Effects of the inducible nitric-oxide synthase inhibitor L-N(6)-(1-iminoethyl)-lysine on microcirculation and reactive nitrogen species generation in the kidney following lipopolysaccharide administration in mice

The mortality rate for septic patients with acute renal failure is approximately doubled compared with patients with sepsis alone. Unfortunately, the treatment for sepsis-induced renal failure has advanced little during the last several decades. Because sepsis is often caused by lipopolysaccharide (LPS), a mouse model of LPS challenge was used to study the development of kidney injury. We hypothesized that inducible nitric-oxide synthase (iNOS)-catalyzed nitric oxide production and that generation of reactive nitrogen species (RNS) might play a role in the microcirculatory defect and resulting tubular injury associated with LPS administration. Fluorescent intravital videomicroscopy was used to assess renal peritubular capillary perfusion and document RNS generation by renal tubules in real time. As early as 6 h after LPS administration (10 mg/kg i.p.), RNS generation (rhodamine fluorescence), redox stress [NAD(P)H autofluorescence], and the percentage of capillaries without flow were each significantly increased compared with saline-treated mice (p < 0.05). The generation of RNS was supported by the detection of nitrotyrosine-protein adducts in the kidney using immunohistochemistry. The iNOS inhibitor l-N(6)-(1-iminoethyl)-lysine (l-NIL; 3 mg/kg i.p.) completely blocked the increase in rhodamine fluorescence and NAD(P)H autofluorescence and prevented the capillary defects at 6 h after LPS administration. These results suggest that iNOS-derived RNS is an important contributor to the peritubular capillary perfusion defects and RNS generation that occur during sepsis and emphasize that pharmacological inhibition of iNOS may provide beneficial effects during sepsis by improving renal capillary perfusion and reducing RNS generation in the kidney.

Peritubular capillary dysfunction and renal tubular epithelial cell stress following lipopolysaccharide administration in mice

The mortality rate for septic patients with acute renal failure is extremely high. Since sepsis is often caused by lipopolysaccharide (LPS), a model of LPS challenge was used to study the development of kidney injury. Intravital video microscopy was utilized to investigate renal peritubular capillary blood flow in anesthetized male C57BL/6 mice at 0, 2, 6, 10, 18, 24, 36, and 48 h after LPS administration (10 mg/kg ip). As early as 2 h, capillary perfusion was dramatically compromised. Vessels with continuous flow were decreased from 89 +/- 4% in saline controls to 57 +/- 5% in LPS-treated mice (P < 0.01), and vessels with intermittent flow were increased from 6 +/- 2% to 31 +/- 5% (P < 0.01). At 2 h, mRNA for intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 were elevated 50- and 27-fold, respectively, suggesting that vascular inflammation is an early event that may contribute to capillary dysfunction. By 10 h, vessels with no flow increased from 5 +/- 2% in saline controls to 19 +/- 3% in LPS-treated mice (P < 0.05). By 48 h, capillary function was returning toward control levels. The decline in functional capillaries preceded the development of renal failure and was paralleled by induction of inducible nitric oxide synthase in the kidney. Using NAD(P)H autofluorescence as an indicator of cellular redox stress, we found that tubular cell stress was highly correlated with the percentage of dysfunctional capillaries (r(2) = 0.8951, P < 0.0001). These data show that peritubular capillary dysfunction is an early event that contributes to tubular stress and renal injury.

Carbon monoxide, but not endothelin-1, plays a major role for the hepatic microcirculation in a murine model of early systemic inflammation

OBJECTIVE

Endothelin-1 and carbon monoxide play a major role in the regulation of liver microcirculation in numerous disease states. During sepsis and endotoxemia, elevated formation of endothelin-1 results in reduced sinusoidal blood flow. However, the role of carbon monoxide and endothelin-1 and its receptors endothelin receptor A and endothelin receptor B in the deranged liver microcirculation during early systemic inflammation remains unclear.

DESIGN

Prospective, randomized, controlled experiment.

SETTING

University animal laboratory.

SUBJECTS

Male C57/BL6 mice, weighing 23-27 g.

INTERVENTIONS

To induce a systemic inflammation, mice were treated with 1 hr of bilateral hind limb ischemia followed by 3 hrs or 6 hrs of reperfusion. Animals were randomly exposed to the nonselective endothelin receptor antagonist Ro-61-6612 (Tezosentan) and/or a continuous endothelin-1 infusion. Different animals were randomized to methylene chloride gavage or carbon monoxide inhalation during the reperfusion period.

MEASUREMENTS AND MAIN RESULTS

After ischemia/reperfusion, endothelin-1 plasma concentrations, endothelin-1 messenger RNA expression, and endothelin receptor A and B messenger RNA expression revealed no significant changes when compared with sham animals. After 6 hrs of ischemia/reperfusion, hepatic microcirculatory variables (sinusoidal density, sinusoidal diameter, and red blood cell velocity) deteriorated. Tezosentan after 6 hrs of ischemia/reperfusion did not improve the liver microcirculation, whereas the continuous infusion of endothelin-1 after 6 hrs of ischemia/reperfusion further impaired sinusoidal blood flow. Tezosentan treatment did not produce any alterations in hepatocellular injury or hepatic redox status when compared with the untreated animals receiving 6 hrs of ischemia/reperfusion. Animals receiving 6 hrs of ischemia/reperfusion and exposed to methylene chloride gavage or inhaled carbon monoxide during limb reperfusion showed significantly improved microcirculatory variables, hepatic redox status, and attenuated hepatocellular injury.

CONCLUSIONS

These data suggest that endothelin-1 and the endothelin receptors A and B are not responsible for the observed hepatic microcirculatory and cellular dysfunction during early systemic inflammation, but exposure to exogenous carbon monoxide protected the hepatic microcirculation and improved the impaired hepatic cellular integrity and the hepatocellular redox status.