Near-Infrared Spectroscopy and Vascular Occlusion Test for Predicting Clinical Outcome in Pediatric Cardiac Patients: A Prospective Observational Study

Resuscitating the macro- vs. microcirculation in septic shock

PURPOSE OF REVIEW

This review summarizes current literature about the relationships between macro and microcirculation and their practical clinical implications in children with septic shock.

RECENT FINDINGS

Current evidence from experimental and clinical observational studies in children and adults with septic shock reveals that the response to treatment and resuscitation is widely variable. Furthermore, there is a loss of hemodynamic coherence, as resuscitation-induced improvement in macrocirculation (systemic hemodynamic parameters) does not necessarily result in a parallel improvement in the microcirculation. Therefore, patient-tailored monitoring is essential in order to adjust treatment requirements during resuscitation in septic shock. Optimal monitoring must integrate macrocirculation (heart rate, blood pressure, cardiac output, and ultrasound images), microcirculation (videomicroscopy parameters and capillary refill time) and cellular metabolism (lactic acid, central venous blood oxygen saturation, and difference of central venous to arterial carbon dioxide partial pressure).

SUMMARY

There is a dire need for high-quality studies to assess the relationships between macrocirculation, microcirculation and tissue metabolism in children with septic shock. The development of reliable and readily available microcirculation and tissue perfusion biomarkers (other than lactic acid) is also necessary to improve monitoring and treatment adjustment in such patients.

Assessment of microcirculatory alteration by a vascular occlusion test using near-infrared spectroscopy in pediatric cardiac surgery: effect of cardiopulmonary bypass

OBJECTIVES

Cardiopulmonary bypass cause microcirculatory alterations. Near infrared spectroscopic measurement of tissue oxygen saturation and vascular occlusion test are novel technologies for assessing the microcirculatory function of peripheral tissue specifically in patients undergoing cardiac surgery with cardiopulmonary bypass.Our study aimed to evaluate dynamic microcirculatory function using the vascular occlusion testing during cardiac surgery in pediatric patients.

METHODS

120 pediatric patients were scheduled. Children had continuous regional oxygen saturation monitoring using near infrared spectroscopy and vascular occlusion test. Vascular occlusion test was performed five times; before induction (T1), after induction (T2), then during cardiopulmonary bypass with full flow (T3), after the termination of CPB (T4) and after sternum closure (T5).

RESULTS

Basal value was the lowest at T3 and this value was significantly different among measurements (p < 0,01).Values for maximum and minimum tissue oxygen saturation were the lowest at T3 (83,4 and 52,9%).The occlusion slope varied significantly among measurements (p < 0,01).Reperfusion slopes were significantly different among measurements (p < 0,01) with a further progressive decrease in reperfusion slope with duration of cardiopulmonary bypass.

CONCLUSION

Microcirculatory function can assessed using VOT with forearm Near-infrared spectroscopy derived variables during cardiopulmonary bypass in pediatric cardiac surgery. Noninvasive assessment of microcirculatory perfusion during cardiopulmonary bypass can further help evaluate and improve circulatory support techniques.

TRIAL REGISTRATION

The research Project was registered at ClinicalTrials.gov (NCT06191913).

Microvascular effects of oxygen and carbon dioxide measured by vascular occlusion test in healthy volunteers

BACKGROUND

Changes in near-infrared spectroscopy-derived regional tissue oxygen saturation (StO₂) during a vascular occlusion test (VOT; ischemic provocation of microcirculation by rapid inflation and deflation of a tourniquet) allow estimating peripheral tissue O₂ consumption (desaturation slope; DS), vascular reactivity (recovery slope; RS) and post-ischemic hyperperfusion (AUC-H). The effects of isolated alterations in the inspiratory fraction of O₂ (FiO₂) and changes in expiratory CO₂ remain to be elucidated. Therefore, in this secondary analysis we determined the effects of standardized isolated instances of hypoxia, hyperoxia, hypocapnia and hypercapnia on the VOT-induced StO₂ changes in healthy volunteers (n = 20) to establish reference values for future physiological studies.

METHODS

StO₂ was measured on the thenar muscle. Multiple VOTs were performed in a standardized manner: i.e. at room air (baseline), during hyperoxia (FiO₂ 1.0), mild hypoxia (FiO₂ ≈ 0.11), and after a second baseline, during hypocapnia (end-tidal CO₂ (etCO₂) 2.5-3.0 vol%) and hypercapnia (etCO₂ 7.0-7.5 vol%) at room air. Differences in DS, RS, and AUC-H were tested using repeated-measures ANOVA.

RESULTS

DS and RS remained constant during all applied conditions. AUC-H after hypoxia was smaller compared to hyperoxia (963 %*sec vs hyperoxia 1702 %*sec, P = 0.005), while there was no difference in AUC-H duration between hypoxia and baseline. The StO₂ peak (after tourniquet deflation) during hypoxia was lower compared to baseline and hyperoxia (92 % vs 94 % and 98 %, P < 0.001).

CONCLUSION

We conclude that in healthy volunteers at rest, common situations observed during anesthesia and intensive care such as exposure to hypoxia, hyperoxia, hypocapnia, or hypercapnia, did not affect peripheral tissue O₂ consumption and vascular reactivity as assessed by VOT-induced changes in StO₂. These observations may serve as reference values for future physiological studies.

TRIAL REGISTRATION

This study represents a secondary analysis of an original study which has been registered at ClinicalTrials.gov nr: NCT02561052.

The use of a vascular occlusion test combined with near-infrared spectroscopy in perioperative care: a systematic review

In the perioperative phase oxygen delivery and consumption can be influenced by different factors, i.e. type of surgery, anesthetic and cardiovascular drugs, or fluids. By combining near-infrared spectroscopy (NIRS) monitoring of regional tissue oxygen saturation (StO₂) with an ischemic provocation test, the vascular occlusion test (VOT), local tissue oxygen consumption and vascular reactivity at the microcirculatory level can be assessed. This systematic review aims to give an overview of the clinical information that VOT-derived NIRS values can provide in the perioperative period. After performing a systematic literature search, we included 29 articles. It was not possible to perform a meta-analysis because of the lack of comparable data and the observational nature of the majority of the included articles. We have clustered the found articles in two groups: non-cardiac surgery and cardiac surgery. We found that VOT-derived NIRS values show a wide variability and are influenced by the effects of anesthetics, cardiovascular drugs, fluids, and by the type of surgery. Additionally, deviations in VOT-derived NIRS values are also associated with adverse patients' outcomes, such as postoperative complications, prolonged mechanical ventilation and prolonged hospital length of stay. However, given the variability in VOT-derived NIRS values, clinical applicability remains elusive. Future clinical interventional trials might provide additional insight into the potential of VOT associated with NIRS to optimize perioperative care by targeting specific interventions to optimize the function of the microvasculature.

Evaluation of Different Near-Infrared Spectroscopy Devices for Assessing Tissue Oxygenation with a Vascular Occlusion Test in Healthy Volunteers

Near-infrared spectroscopy devices can measure peripheral tissue oxygen saturation (StO2). This study aims to compare StO2 using INVOS® and different O3™ settings (O325:75 and O330:70). Twenty adults were recruited. INVOS® and O3™ probes were placed simultaneously on 1 side of forearm. After baseline measurement, the vascular occlusion test was initiated. The baseline value, rate of deoxygenation and reoxygenation, minimum and peak StO2, and time from cuff release to peak value were measured. The parameters were compared using ANOVA and Kruskal-Wallis tests. Bonferroni's correction and Mann-Whitney pairwise comparison were used for post hoc analysis. The agreement between StO2 of devices was evaluated using Bland-Altman plots. INVOS® baseline value was higher (79.7 ± 6.4%) than that of O325:75 and O330:70 (62.4 ± 6.0% and 63.7 ± 5.5%, respectively, p < 0.001). The deoxygenation rate was higher with INVOS® (10.6 ± 2.1%/min) than with O325:75 and O330:70 (8.4 ± 2.2%/min, p = 0.006 and 7.5 ± 2.1%/min, p < 0.001). The minimum and peak StO2 were higher with INVOS®. No significant difference in the reoxygenation rate was found between the devices and settings. The time to reach peak after cuff deflation was faster with INVOS® (both p < 0.001). Other parameters were similar. There were no differences between the different O3™ settings. There were differences in StO2 measurements between the devices, and these devices should not be interchanged. Differences were not observed between O3™ device settings.

Cerebral oxygenation during pediatric congenital cardiac surgery and its association with outcome: a retrospective observational study

Purpose

Non-invasive cerebral oxygen saturation (ScO₂) monitoring is an established tool in the intraoperative phase of pediatric congenital cardiac surgery (CCS). This study investigated the association between ScO₂ and postoperative outcome by investigating both baseline ScO₂ values and intraoperative desaturations from baseline.

Methods

All CCS procedures performed in the period 2010-2017 in our institution in which ScO₂ was monitored were included in this historical cohort study. Baseline ScO₂ was determined after tracheal intubation, before surgical incision. Subgroups were based on cardiac pathology and degree of intracardiac shunting. Poor outcome was defined based on length of stay (LOS) in the intensive care unit (ICU)/hospital, duration of mechanical ventilation (MV), and 30-day mortality. Intraoperatively, ScO₂ total time below baseline (TBBL) and ScO₂ time-weighted average (TWA) were calculated.

Results

Data from 565 patients were analyzed. Baseline ScO₂ was significantly associated with LOS in ICU (odds ratio [OR] per percentage decrease in baseline ScO₂, 0.95; 95% confidence interval [CI], 0.93 to 0.97; P < 0.001), with LOS in hospital (OR, 0.93; 95% CI, 0.91 to 0.96; P < 0.001), with MV duration (OR, 0.92; 95% CI, 0.90 to 0.95; P < 0.001) and with 30-day mortality (OR, 0.94; 95% CI, 0.91 to 0.98; P = 0.007). Cerebral oxygen saturation TWA had no associations, while ScO₂ TBBL had only a small association with LOS in ICU (OR, 1.02; 95% CI, 1.01 to 1.03; P < 0.001), MV duration (OR,1.02; 95% CI, 1.01 to 1.03; P = 0.002), and LOS in hospital (OR, 1.02; 95% CI, 1.01 to 1.04; P < 0.001).

Conclusion

In pediatric patients undergoing cardiac surgery, low baseline ScO₂ values measured after tracheal intubation were associated with several adverse postoperative outcomes. In contrast, the severity of actual intraoperative cerebral desaturation was not associated with postoperative outcomes. Baseline ScO₂ measured after tracheal intubation may help identify patients at increased perioperative risk.

Sickle cell microvascular paradox-oxygen supply-demand mismatch

We have previously demonstrated that sickle cell disease (SCD) patients maintain normal global systemic and cerebral oxygen delivery by increasing cardiac output. However, ischemic end-organ injury remains common suggesting that tissue oxygen delivery may be impaired by microvascular dysregulation or damage. To test this hypothesis, we performed fingertip laser Doppler flowmetry measurements at the base of the nailbed and regional oxygen saturation (rSO₂ ) on the dorsal surface of the same hand. This was done during flow mediated dilation (FMD) studies in 26 chronically transfused SCD, 75 non-transfused SCD, and 18 control subjects. Chronically transfused SCD patients were studied prior to and following a single transfusion and there was no acute change in rSO₂ or perfusion. Laser Doppler estimates of resting perfusion were 76% higher in non-transfused and 110% higher in transfused SCD patients, compared to control subjects. In contrast, rSO₂ was 12 saturation points lower in non-transfused SCD patients, but normal in the transfused SCD patients. During cuff occlusion, rSO₂ declined at the same rate in all subjects suggesting similar intrinsic oxygen consumption rates. Upon cuff release, laser doppler post occlusive hyperemia was blunted in SCD patients in proportion to their resting perfusion values. Transfusion therapy did not improve the hyperemia response. FMD was impaired in SCD subjects but partially ameliorated in transfused SCD subjects. Taken together, non-transfused SCD subjects demonstrate impaired conduit artery FMD, impaired microcirculatory post-occlusive hyperemia, and resting hypoxia in the hand despite compensated oxygen delivery, suggesting impaired oxygen supply-demand matching. Transfusion improves FMD and oxygen supply-demand matching but not microcirculation hyperemic response.