Microvascular monitoring – Do ‘global’ markers help?

Sublingual microcirculatory alterations during the immediate and early postoperative period: A systematic review and meta-analysis

BACKGROUND

The incidence of postoperative microcirculatory flow alterations and their effect on outcome have not been studied extensively.

OBJECTIVE

This systematic review and meta-analysis was designed to investigate the presence of sublingual microcirculatory flow alterations during the immediate and early postoperative period and their correlation with complications and survival.

METHODS

A systematic search of PubMed, Scopus, Embase, PubMed Central, and Google Scholar was conducted for relevant articles from January 2000 to March 2021. Eligibility criteria were randomized controlled and non-randomized trials. Case reports, case series, review papers, animal studies and non-English literature were excluded. The primary outcome was the assessment of sublingual microcirculatory alterations during the immediate and early postoperative period in adult patients undergoing surgery. Risk of bias was assessed with the Ottawa-Newcastle scale. Standard meta-analysis methods (random-effects models) were used to assess the difference in microcirculation variables.

RESULTS

Thirteen studies were included. No statistically significant difference was found between preoperative and postoperative total vessel density (p = 0.084; Standardized Mean Difference (SMD): -0.029; 95%CI: -0.31 to 0.26; I2 = 22.55%). Perfused vessel density significantly decreased postoperatively (p = 0.035; SMD: 0.344; 95%CI: 0.02 to 0.66; I2 = 65.66%), while perfused boundary region significantly increased postoperatively (p = 0.031; SMD: -0.415; 95%CI: -0.79 to -0.03; I2 = 37.21%). Microvascular flow index significantly decreased postoperatively (p = 0.028; SMD: 0.587; 95%CI: 0.06 to 1.11; I2 = 86.09%), while no statistically significant difference was found between preoperative and postoperative proportion of perfused vessels (p = 0.089; SMD: 0.53; 95%CI: -0.08 to 1.14; I2 = 70.71%). The results of the non-cardiac surgery post-hoc analysis were comparable except that no statistically significant difference in perfused vessel density was found (p = 0.69; SMD: 0.07; 95%CI: -0.26 to 0.39; I2 = 0%).

LIMITATIONS

The included studies investigate heterogeneous groups of surgical patients. There were no randomized controlled trials.

CONCLUSIONS

Significant sublingual microcirculatory flow alterations are present during the immediate and early postoperative period. Further research is required to estimate the correlation of sublingual microcirculatory flow impairment with complications and survival.

Visualization of three-dimensional microcirculation of rodents' retina and choroid for studies of critical illness using optical coherence tomography angiography

We developed a method to measure the relative blood flow speed using optical coherence tomography angiography (OCTA) in retina and choroid, and investigated the feasibility of this method for assessing microcirculatory function in rat models of sepsis and hemorrhagic shock. Two sepsis models, 6-h severe sepsis without treatment and 30-h moderate sepsis maintaining mean arterial pressure, and volume controlled hemorrhagic shock and fluid resuscitation model were used to see the change of microcirculation. The blood flow index (BFI), which was calculated from the OCTA images to represent the average relative blood flow, was decreasing during the 6-h severe sepsis model. Its change is in parallel with the mean arterial blood pressure (MAP) and blood lactate levels. In the 30-h moderate sepsis model, the BFI was decreased while maintaining MAP, and lactate was increased. In the hemorrhagic shock model, the change of BFI is in line with MAP and lactate levels. In all models, BFI change is more sensitive in choroid than in retina. This study presents the OCTA-based retinal and choroidal microcirculatory blood flow monitoring method and shows its utility for assessment of critical illness.

Microvascular endothelial dysfunction during cardiopulmonary bypass in surgery for correction of cyanotic and acyanotic congenital heart disease

OBJECTIVE

To evaluate endothelium-dependent microvascular reactivity during cardiopulmonary bypass (CPB) in surgery for the correction of cyanotic and acyanotic congenital heart disease (CHD) in children and infants using laser Doppler perfusion monitoring (LDPM).

METHODS

This cross-sectional observational study included one hundred consecutive acyanotic (AC, n = 61) and cyanotic (C, n = 39) pediatric patients scheduled for cardiac surgery for correction of CHD. The endothelium-dependent microvascular vasodilation of the skin of the forehead was evaluated using a single-point LDPM coupled with local thermal hyperemia (LTH).

RESULTS

LTH induced significant increases in microvascular conductance both in AC and C patients after the induction of anesthesia, during CPB and after weaning from CPB. Nevertheless, the vasodilation induced by LTH was significantly blunted during CPB when compared with values obtained after the induction of anesthesia both in AC and C patients. Microvascular endothelial reactivity nearly normalized after the discontinuation of CPB.

CONCLUSION

The evaluation of systemic microvascular reactivity on the forehead skin of infants and children using LDPM appears to be a valuable tool for optimizing microvascular perfusion during CPB in pediatric cardiac surgery.

Evaluation of microvascular endothelial function and capillary density in patients with infective endocarditis using laser speckle contrast imaging and video-capillaroscopy

OBJECTIVE

To evaluate the systemic microcirculation of patients with infective endocarditis (IE).

METHODS

This is a comparative study of patients with definite IE by the modified Duke criteria admitted to our center for treatment. A reference group of sex- and age-matched healthy volunteers was included. Microvascular flow was evaluated in the forearm using a laser speckle contrast imaging system, for noninvasive measurement of cutaneous microvascular perfusion, in combination with skin iontophoresis of acetylcholine (ACh) and sodium nitroprusside (SNP) to test microvascular reactivity. Microvascular density was evaluated using skin video-capillaroscopy.

RESULTS

We studied 22 patients with IE; 15 were male and seven female. The mean age and standard deviation (SD) were 45.5 ± 17.3 years. Basal skin microvascular conductance was significantly increased in patients with IE, compared with healthy individuals (0.36 ± 0.13 versus 0.21 ± 0.08 APU/mmHg; P < 0.0001). The increase in microvascular conductance induced by ACh in patients was 0.21 ± 0.17 and in the reference group, it was 0.37 ± 0.14 APU/mmHg (P = 0.0012). The increase in microvascular conductance induced by SNP in patients was 0.18 ± 0.14 and it was 0.29 ± 0.15 APU/mmHg (P = 0.0140) in the reference group. The basal mean skin capillary density of patients (135 ± 24 capillaries/mm²) was significantly higher, compared with controls (97 ± 21 capillaries/mm²; P < 0.0001).

CONCLUSIONS

The main findings in the microcirculation of patients with IE were greater basal vasodilation and a reduction of the endothelium-dependent and -independent microvascular reactivity, as well as greater functional skin capillary density compared to healthy individuals.

Evaluation of microvascular endothelial function in patients with infective endocarditis using laser speckle contrast imaging and skin video-capillaroscopy: research proposal of a case control prospective study

OBJECTIVE

Infective endocarditis is a severe condition with high in-hospital and 5-year mortality. There is increasing incidence of infective endocarditis, which may be related to healthcare and changes in prophylaxis recommendations regarding oral procedures. Few studies have evaluated the microcirculation in patients with infective endocarditis, and so far, none have utilized laser-based technology or evaluated functional capillary density. The aim of the study is to evaluate the changes in the systemic microvascular bed of patients with both acute and subacute endocarditis. This is a cohort study that will include adult patients with confirmed active infective endocarditis according to the modified Duke criteria who were admitted to our center for treatment. A control group of sex- and age-matched healthy volunteers will be included. Functional capillary density, which is defined as the number of spontaneously perfused capillaries per square millimeter of skin, will be assessed by video-microscopy with an epi-illuminated fiber optic microscope. Capillary recruitment will be evaluated using post-occlusive reactive hyperemia. Microvascular flow will be evaluated in the forearm using a laser speckle contrast imaging system for the noninvasive and continuous measurement of cutaneous microvascular perfusion changes. Laser speckle contrast imaging will be used in combination with skin iontophoresis of acetylcholine, an endothelium-dependent vasodilator, or sodium nitroprusside (endothelium independent) to test microvascular reactivity.

RESULTS

The present study will contribute to the investigation of microcirculatory changes in infective endocarditis and possibly lead to an earlier diagnosis of the condition and/or determination of its severity and complications. Trial registration ClinicalTrials.gov ID: NCT02940340.