Microvascular blood flow alterations are frequent in animal models of sepsis and may impair tissue oxygenation. We hypothesized that alterations of the microcirculation are present in patients with sepsis. We used an orthogonal polarization spectral imaging technique to investigate the sublingual microcirculation in 10 healthy volunteers, 16 patients before cardiac surgery, 10 acutely ill patients without sepsis (intensive care unit control subjects), and 50 patients with severe sepsis. The effects of topical application of acetylcholine (10(-2) M) were tested in 11 patients with sepsis. In each subject, five to seven sublingual areas were recorded and analyzed semiquantitatively. Data were analyzed with nonparametric tests and are presented as medians (25th-75th percentiles). No significant difference in microvascular blood flow was observed between healthy volunteers and patients before cardiac surgery or intensive care unit control subjects. The density of all vessels was significantly reduced in patients with severe sepsis (4.5 [4.2-5.2] versus 5.4 [5.4-6.3]/mm in volunteers, p < 0.01). The proportion of perfused small (< 20 microm) vessels was reduced in patients with sepsis (48 [33-61] versus 90 [89-92]% in volunteers, p < 0.001). These alterations were more severe in nonsurvivors. The topical application of acetylcholine totally reversed these alterations. In conclusion, microvascular blood flow alterations are frequent in patients with sepsis and are more severe in patients with a worse outcome.

Microvascular Blood Flow Is Altered in Patients with Sepsis

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(02)09459-X.pdf

Association between mitochondrial dysfunction and severity and outcome of septic shock

The interaction of light within tissue has been used to recognize disease since the mid-1800s. The recent developments of small light sources, detectors, and fiber optic probes provide opportunities to quantitatively measure these interactions, which yield information for diagnosis at the biochemical, structural, or (patho)physiological level within intact tissues. However, because of the strong scattering properties of tissues, the reemitted optical signal is often influenced by changes in biochemistry (as detected by these spectroscopic approaches) and by physiological and pathophysiological changes in tissue scattering. One challenge of biomedical optics is to uncouple the signals influenced by biochemistry, which themselves provide specificity for identifying diseased states, from those influenced by tissue scattering, which are typically unspecific to a pathology. In this review, we describe optical interactions pursued for biomedical applications (fluorescence, fluorescence lifetime, phosphorescence, and Raman from cells, cultures, and tissues) and then provide a descriptive framework for light interaction based upon tissue absorption and scattering properties. Finally, we review important endogenous and exogenous biological chromophores and describe current work to employ these signals for detection and diagnosis of disease.

Quantitative optical spectroscopy for tissue diagnosis

Keywords: Photomedicine group Reference LPAS-ARTICLE-1998-003View record in Web of Science Record created on 2007-07-20, modified on 2016-08-08

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1751-1097.1998.tb02521.x

In Vivo Fluorescence Spectroscopy and Imaging for Oncological Applications

Singlet oxygen, O2(a1Δg), the lowest excited electronic state of molecular oxygen, has been known to the scientific community for ∼80 years. It has a characteristic chemistry that sets it apart from the triplet ground state of molecular oxygen, O2(X3Σ−g), and is important in fields that range from atmospheric chemistry and materials science to biology and medicine. For such a “mature citizen”, singlet oxygen nevertheless remains at the cutting-edge of modern science. In this critical review, recent work on singlet oxygen is summarized, focusing primarily on systems that involve light. It is clear that there is indeed still something new under the sun (243 references).

Singlet oxygen: there is indeed something new under the sun

ObjectiveTo review optical spectroscopic techniques for assessment of the determinants of tissue oxygenation and to evaluate the notion that the disturbances in oxygen pathways in sepsis can be accounted for by enhanced functional shunting of parts of the microcirculation.Data ResourcesExperimental

Microcirculatory oxygenation and shunting in sepsis and shock.

Molecular oxygen is the primary oxidant in biological systems. The ultimate destination of oxygen in vivo is the mitochondria where it is used in oxidative phosphorylation. The ability of this process to produce an amount of high-energy phosphates adequate to sustain life highly depends on the available amount of oxygen. Despite a vast array of techniques to measure oxygen, major (patho)physiological questions remain unanswered because of the unavailability of quantitative techniques to measure mitochondrial oxygen in situ. Here we demonstrate that mitochondrial PO2 can be directly measured in living cells by harnessing the delayed fluorescence of endogenous protoporphyrin IX (PpIX), thereby providing a technique with the potential for a wide variety of applications. We applied this technique to different cell lines (V-79 Chinese hamster lung fibroblasts, HeLa cells and IMR 32-K1 neuroblastoma cells) and present the first direct measurements of the oxygen gradient between the mitochondria and the extracellular volume.

Mitochondrial PO2 measured by delayed fluorescence of endogenous protoporphyrin IX.

Sinaasappel, M., and C. Ince. Calibration of Pd-porphyrin phosphorescence for oxygen concentration measurements in vivo. J. Appl. Physiol. 81(5): 2297–2303, 1996.—Quantitative measurement of oxygen...

Calibration of Pd-porphyrin phosphorescence for oxygen concentration measurements in vivo

Intestinal ischaemia resulting from shock is particularly hazardous because it can cause loss of barrier function, which could contribute to the development of sepsis (Pinsky & Matuschak, 1989). The oxygenation of the microcirculation can show deterioration in advance of changes in global parameters of oxygenation (Gutierrez, 1986; Stein et al. 1993; Lam et al. 1994; Kerger et al. 1996). However, the behaviour of microcirculatory oxygenation in shock and resuscitation remains largely unknown. Therefore methods are needed to assess the microvascular PO2 (μPO2). The application of the quenching of Pd-porphyrin phosphorescence by oxygen provides a new promising optical method. This method of oxygen measurement has been applied to measure the PO2 of the microcirculation of the eye (Shonat et al. 1992), the isolated rat heart (Ince et al. 1993; Rumsey et al. 1994), brain (Wilson et al. 1991; Pastuszko et al. 1993), muscle (Poole et al. 1995; Kerger et al. 1996) and tumour (Helmlinger et al. 1997). However, it has not as yet been applied to the intestines. The quenching of phosphorescence technique provides a quantitative measure of the amount of oxygen in the microcirculation. In this technique, the decay time of the phosphorescence is measured after pulsed excitation. The Pd-porphyrin is bound to albumin and when this molecular complex is injected intravascularly the dye is confined to the circulation and enables measurement of the PO2 of this compartment (Shonat et al. 1992). We recently calibrated and characterized the use of Pd-porphyrin phosphorescence for measurement of PO2 with a newly developed phosphorimeter (Sinaasappel & Ince, 1996). The main purpose of this study was to investigate the relation between the microvascular oxygenation of the pig ileum, measured by the quenched phosphorescence of Pd-porphyrin, and regional and global parameters of oxygenation, during haemorrhagic shock and resuscitation. Pd-porphyrin phosphorescence quenching by oxygen was validated for measurement of μPO2 in the intestine by comparison with surface electrode measurements. The results presented in this study show that μPO2 becomes lower than the venous PO2 during haemorrhagic shock, indicating that oxygen bypasses the microcirculation. This indicates that venous PO2 is not a good measure of the oxygenation of the intestine under all circumstances.

https://physoc.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1469-7793.1999.245af.x

Microvascular oxygen pressure in the pig intestine during haemorrhagic shock and resuscitation

A theory is presented describing a method for quantitative measurement of fluorophores inυiυo. The method employs a combination of two-wavelength excitation and two-wavelength detection. A dimensionless fluorescence ratio is defined. The theory predicts that this ratio is a function of the concentration of the fluorophore only and is independent of optical properties, independent of geometrical parameters, and independent of autofluorescence. Experiments using a 0.1–10-μg/mL hematoporphyrin derivative in a tissue phantom with the optical properties of the dermis show good agreement with theory.

Michiel Sinaasappel

Papers

Microcirculatory oxygenation and shunting in sepsis and shock.

Mitochondrial PO2 measured by delayed fluorescence of endogenous protoporphyrin IX.

Calibration of Pd-porphyrin phosphorescence for oxygen concentration measurements in vivo

Microvascular oxygen pressure in the pig intestine during haemorrhagic shock and resuscitation

Quantification of the hematoporphyrin derivative by fluorescence measurement using dual-wavelength excitation and dual-wavelength detection