The impact of induction of general anesthesia and a vascular occlusion test on tissue oxygen saturation derived parameters in high-risk surgical 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.

Altered microvascular reactivity assessed by near-infrared spectroscopy after hepato-pancreato-biliary surgery

Little is known about microcirculatory dysfunction following abdominal surgeries. This study aimed to evaluate changes in microvascular reactivity (MVR) before and after major abdominal surgery, assessed by near-infrared spectroscopy in conjunction with a vascular occlusion test. This prospective observational study included 50 adult patients who underwent hepato-pancreato-biliary surgery lasting ≥ 8 h. MVR was assessed by tissue oxygen saturation (StO₂) changes in the plantar region of the foot during 3 min of vascular occlusion and subsequent release under general anesthesia before and after surgery. The primary outcome was alteration in the recovery slope of StO₂ (RecStO₂) and recovery time (tM) between the preoperative and postoperative values. Postoperative short-term outcome was represented by the Post-operative Morbidity Survey (POMS) score on the morning of postoperative day 2. After surgery, RecStO₂ was reduced (0.74% [0.58-1.06]/s vs. 0.89% [0.62-1.41]/s, P = 0.001), and tM was longer (57.0 [42.9-71.0] s vs. 41.3 [35.5-56.5] s, P < 0.001), compared to the preoperative values. Macrohemodynamic variables such as cardiac index, arterial pressure, and stroke volume during postoperative measurement did not differ with or without relative MVR decline. In addition, the POMS score was not associated with postoperative alterations in microcirculatory responsiveness. MVR in the plantar region of the foot was reduced after major hepato-pancreato-biliary surgery regardless of macrocirculatory adequacy. Impaired MVR was not associated with short-term outcomes as long as macrocirculatory indices were well maintained. The impact of relative microcirculatory changes, especially combined with inadequate macrocirculation, on postoperative complications remains to be elucidated.Clinical Trial Registrations UMIN-CTR trial ID: 000033461.

Microvascular Reactivity Measured by Dynamic Near-infrared Spectroscopy Following Induction of General Anesthesia in Healthy Patients: Observation of Age-related Change

Background: The purpose of this study was to investigate the effect of general anesthesia on microvascular reactivity and tissue oxygen saturation (StO₂) using near-infrared spectroscopy in conjunction with vascular occlusion tests (VOT). Age-related changes of microvascular reactivity, that is, the capacity of capillary recruitment, were examined. Methods: This prospective observational study was performed on 60 patients without comorbidities who underwent elective surgery under general anesthesia. Baseline StO₂ on thenar eminence, hemodynamics, and laboratory profile were monitored before (T0) and 30 min after general anesthesia (T1). During VOT, occlusion slope representing oxygen consumption of muscle and recovery slope representing microvascular reactivity were also collected at T0 and T1. Results: Baseline StO₂ and minimum / maximum StO₂ during VOT increased under general anesthesia. Occlusion slope decreased while the recovery slope increased under general anesthesia. To observe aging effect, Receiver operating characteristic analysis was performed and age less than 65 years old showed a fair performance in predicting the increase of microvascular reactivity after the induction of anesthesia (AUC 0.733, 95% CI 0.594-0.845, P= 0.003). For age-related analyses, 27 patients of younger group (< 65 years) and 26 patients of older group (≥ 65 years) were divided. Recovery slope significantly increased under general anesthesia in younger group (2.44 [1.91-2.81] % ∙ sec^-1 at T0 and 3.59 [2.58-3.51] % ∙ sec^-1 at T1, P <0.001), but not in older group (2.61 [2.21-3.20] % ∙ sec^-1 at T0, 2.63 [1.90-3.60] % ∙ sec^-1 at T1, P = 0.949). Conclusions: General anesthesia could improve StO₂ through increase of microvascular reactivity and decrease of tissue metabolism. However, microvascular reactivity to capillary recruitment under general anesthesia significantly improves in younger patients, not in older patients.

The vascular occlusion test using multispectral imaging: a validation study : The VASOIMAGE study

Multispectral imaging (MSI) is a new, non-invasive method to continuously measure oxygenation and microcirculatory perfusion, but has limitedly been validated in healthy volunteers. The present study aimed to validate the potential of multispectral imaging in the detection of microcirculatory perfusion disturbances during a vascular occlusion test (VOT). Two consecutive VOT's were performed on healthy volunteers and tissue oxygenation was measured with MSI and near-infrared spectroscopy (NIRS). Correlations between the rate of desaturation, recovery and the hyperemic area under the curve (AUC) measured by MSI and NIRS were calculated. Fifty-eight volunteers were included. The MSI oxygenation curves showed identifiable components of the VOT, including a desaturation and recovery slope and hyperemic area under the curve, similar to those measured with NIRS. The correlation between the rate of desaturation measured by MSI and NIRS was moderate: r = 0.42 (p = 0.001) for the first and r = 0.41 (p = 0.002) for the second test. Our results suggest that non-contact multispectral imaging is able to measure changes in regional oxygenation and deoxygenation during a vascular occlusion test in healthy volunteers. When compared to measurements with NIRS, correlation of results was moderate to weak, most likely reflecting differences in physiology of the regions of interest and measurement technique.

Extracellular Vesicles: Recent Developments in Technology and Perspectives for Cancer Liquid Biopsy

Extracellular micro- and nanoscale membrane vesicles produced by different cells progressively attract the attention of the scientific community. They function as mediators of intercellular communication and transport genetic material and signaling molecules between the cells. In the context of keeping homeostasis, the extracellular vesicles contribute to the regulation of various systemic and local processes. Vesicles released by the tumor and activated stromal cells exhibit multiple functions including support of tumor growth, preparation of the pre-metastatic niches, and immune suppression. Considerable progress has been made regarding the criteria of classification of the vesicles according to their origin, content, and function: Exosomes, microvesicles, also referred to as microparticles or ectosomes, and large oncosomes were defined as actively released vesicles. Additionally, apoptotic bodies represented by a highly heterogeneous population of particles produced during apoptosis, the programmed cell death, should be considered. Because the majority of isolation techniques do not allow the separation of different types of vesicles, a joined term "extracellular vesicles" (EVs) was recommended by the ISEV community for the definition of vesicles isolated from either the cell culture supernatants or the body fluids. Because EV content reflects the content of the cell of origin, multiple studies on EVs from body fluids in the context of cancer diagnosis, prediction, and prognosis were performed, actively supporting their high potential as a biomarker source. Here, we review the leading achievements in EV analysis from body fluids, defined as EV-based liquid biopsy, and provide an overview of the main EV constituents: EV surface proteins, intravesicular soluble proteins, EV RNA including mRNA and miRNA, and EV DNA as potential biomarkers. Furthermore, we discuss recent developments in technology for quantitative EV analysis in the clinical setting and future perspectives toward miniaturized high-precision liquid biopsy approaches.

Assessment of muscle oxygenation in children with congenital heart disease

BACKGROUND

Adaptive responses to congenital heart disease result in altered muscle perfusion and muscle metabolism. Such changes may be detectable using noninvasive spectroscopic monitors.

AIMS

In this study we aimed to determine if resting muscle oxygen saturation (MOx) is lower in children with acyanotic or cyanotic congenital heart disease than in healthy children and to identify differences in muscle oxygen consumption in children with cyanotic and acyanotic congenital heart disease.

METHODS

Using a custom fiber optic spectrometer system, optical measurements were obtained from the calf or forearm of 49 patients (17 with acyanotic congenital heart disease, 18 with cyanotic congenital heart disease, and 14 control). Twenty additional control patients were used to develop the analytic model. Spectra were used to determine MOx at baseline, during arterial occlusion, and during reperfusion. The rate of muscle desaturation during arterial occlusion was also evaluated. Two-sample t-tests were used to compare each heart disease group with the controls.

RESULTS

Patients with acyanotic and cyanotic congenital heart disease had lower baseline MOx than controls. Baseline MOx was 91.3% (CI 85.9%, 96.7%) for acyanotic patients, 91.1% (CI 86.3%, 95.9%) for cyanotic patients, and 98.9% (CI 96.7%, 101.1%) for controls. Similarly, MOx was lower in the acyanotic and cyanotic groups than the controls after reperfusion (84.6% [CI 74.1%, 95.1%] and 82.1% [CI 74.5%, 89.7%] vs 98.9% [96.5%, 101.3%]). The rate of decline in oxygenation was significantly greater in cyanotic patients versus controls (0.46%/s (CI 0.30%, 0.62%/s) vs 0.17%/s (0.13%, 0.21%/s)).

CONCLUSION

This study demonstrates that muscle oxygenation is abnormal in children with both cyanotic and acyanotic congenital heart disease. This suggests that noninvasive monitoring of muscle oxygenation may provide valuable information in situations where children with congenital heart disease may be at risk of hemodynamic compromise.

A Spectral Filter Array Camera for Clinical Monitoring and Diagnosis: Proof of Concept for Skin Oxygenation Imaging

The emerging technology of spectral filter array (SFA) cameras has great potential for clinical applications, due to its unique capability for real time spectral imaging, at a reasonable cost. This makes such cameras particularly suitable for quantification of dynamic processes such as skin oxygenation. Skin oxygenation measurements are useful for burn wound healing assessment and as an indicator of patient complications in the operating room. Due to their unique design, in which all pixels of the image sensor are equipped with different optical filters, SFA cameras require specific image processing steps to obtain meaningful high quality spectral image data. These steps include spatial rearrangement, SFA interpolations and spectral correction. In this paper the feasibility of a commercially available SFA camera for clinical applications is tested. A suitable general image processing pipeline is proposed. As a ’proof of concept’ a complete system for spatial dynamic skin oxygenation measurements is developed and evaluated. In a study including 58 volunteers, oxygenation changes during upper arm occlusion were measured with the proposed SFA system and compared with a validated clinical device for localized oxygenation measurements. The comparison of the clinical standard measurements and SFA results show a good correlation for the relative oxygenation changes. This proposed processing pipeline for SFA cameras shows to be effective for relative oxygenation change imaging. It can be implemented in real time and developed further for absolute spatial oxygenation measurements.

Journal of Clinical Monitoring and Computing 2017/2018 end of year summary: monitoring-and provocation-of the microcirculation and tissue oxygenation

The microcirculation is the ultimate goal of hemodynamic optimization in the perioperative and critical care setting. In this fourth end-of-year summary of the Journal of Clinical Monitoring and Computing on this topic, we take a closer look at papers published in the last 2 years that focus on this important aspect. The majority of these papers investigated the use of either cerebral or peripheral tissue oxygen saturation, derived non-invasively using near infrared spectroscopy (NIRS). In some of these studies, the microcirculation was “provocated” by inducing short-term tissue hypoxia, allowing the assessment of functional microvascular reserve. Additionally, studies on technical differences between NIRS monitors are summarized, as well as studies investigating the feasibility of NIRS monitoring, mainly in the pediatric patient population. Last but not least, novel monitoring tools allow assessing oxygenation at a (sub)cellular level, and those papers incorporating these techniques are also reviewed here.

Microvascular reactivity monitored with near-infrared spectroscopy is impaired after induction of anaesthesia in cardiac surgery patients: An observational study

BACKGROUND

Induction of anaesthesia causes significant macrohaemodynamic changes, but little is known about its effects on the microcirculation. However, alterations in microvascular perfusion are known to be associated with impaired tissue oxygenation and organ dysfunction. Microvascular reactivity can be assessed with vascular occlusion testing, which evaluates the response of tissue oxygen saturation to transient ischaemia and reperfusion.

OBJECTIVE

The aim of the current study was to evaluate the effects of an opioid-based anaesthesia induction on microvascular reactivity. We hypothesised that despite minimal blood pressure changes, microvascular function would be impaired.

DESIGN

Prospective, observational study.

SETTING

Single-centre, tertiary university teaching hospital, Belgium.

PATIENTS

Thirty-five adult patients scheduled for elective coronary artery bypass grafting surgery.

INTERVENTION

Microvascular reactivity was assessed before and 30 min after anaesthesia induction by means of vascular occlusion testing and near-infrared spectroscopy.

MAIN OUTCOME MEASURES

Tissue oxygen saturations, desaturation rate, recovery time (time from release of cuff to the maximum value) and rate of recovery were determined.

RESULTS

Data are expressed as median (minimum to maximum). Tissue oxygen saturation was higher after induction of anaesthesia [70 (54 to 78) vs. 73 (55 to 94)%, P = 0.015]. Oxygen consumption decreased after induction, appreciable by the higher minimum tissue oxygen saturation [45 (29 to 69) vs. 53 (28 to 81)%, P < 0.001] and the slower desaturation rate [11 (4 to 18) vs. 9 (5 to 16)% min, P < 0.001]. After induction of anaesthesia, recovery times were longer [40 (20 to 120) vs. 48 (24 to 356) s, P = 0.004] and the rate of recovery was lower [114 (12 to 497) vs. 80 (3 to 271)% min, P < 0.001].

CONCLUSION

After induction of anaesthesia, oxygen consumption was decreased. The longer recovery times and slower rates of recovery indicate impaired microvascular reactivity after induction of anaesthesia.

TRIAL REGISTRATION

The research project was registered at ClinicalTrials.gov (NCT02034682).

Recruitment of sublingual microcirculation using handheld incident dark field imaging as a routine measurement tool during the postoperative de-escalation phase-a pilot study in post ICU cardiac surgery patients

Background

Management of tissue perfusion following cardiac surgery is a challenging task where common clinical parameters do not reflect microcirculatory dysfunction. Heterogeneity in blood flow perfusion and abnormalities in capillary density characterize microcirculatory dysfunction. The restoration of a normal microcirculation may become a novel target for therapy in the future in addition to macrocirculatory parameters. The aim of this study is to determine how the sublingual microcirculatory parameters vary at the bedside in post-cardiac surgery patients which underwent diuretic therapy to correct fluid overload.

Methods

In this prospective observational pilot study, video clips of sublingual microcirculation in post-cardiac surgery patients receiving furosemide and/or spironolactone to achieve normal fluid balance were recorded using Cytocam-IDF imaging. Data was obtained on the first (T0), second (T1), and third (T2) day after the patients left the intensive care unit (ICU). Measurements were analyzed off-line to obtain the following microcirculatory parameters: total vessel density (TVD), microcirculatory flow index (MFI), proportion of perfused vessel (PPV), and perfused vessel density (PVD). Macrocirculatory parameters and body weight were also collected at these time points.

Results

Ninety measurements were performed in ten post ICU cardiac surgery patients. Thirteen measurements were excluded due to quality reasons; these excluded measurements were spread across the patients and time points, and there was no loss of patients or time points. An increase in TVD was observed from T0 to T1 (20 ± 2.7 to 24 ± 3.2 mm/mm²; p = 0.0410) and from T0 to T2 (20 ± 2.7 to 26 ± 3.3 mm/mm²; p = 0.0005). An increase in PVD was present from T0 to T1 (19 ± 2.3 to 24 ± 3.5 mm/mm²; p = 0.0072) and from T0 to T2 (19 ± 2.3 to 26 ± 3.4 mm/mm², p = 0.0008). Fluid overload was assessed through a positive cumulative fluid balance on the day of ICU discharge.

Conclusions

Cytocam-IDF imaging to monitor microcirculation as a daily parameter is feasible and could become a valuable tool to non-invasively assess the tissue oxygenation at the bedside. An increase in TVD and PVD (functional capillary density) indicated the recruitment of the sublingual microcirculation in patients with diuretic therapy. Future research is needed to prove the correlation between the recruitment of the sublingual microcirculation and the de-escalation phase of the fluid management.

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

OBJECTIVES

This study is designed to determine the feasibility and utility of vascular occlusion test variables as measured by INVOS Medtronic, Dublin, Ireland) in pediatric cardiac patients.

DESIGN

A prospective observational study.

SETTING

A tertiary children's hospital.

PATIENTS

Children less than or equal to 8 years old who were scheduled for elective cardiac surgery under cardiopulmonary bypass.

INTERVENTIONS

A vascular occlusion test (3 min of ischemia and reperfusion) was performed on the calf at three time points: after induction of anesthesia (T0), during cardiopulmonary bypass (T1), and after sternal closure (T2).

MEASUREMENTS AND MAIN RESULTS

Baseline regional tissue hemoglobin oxygen saturation, deoxygenation rate, minimum regional tissue hemoglobin oxygen saturation, and reoxygenation rate were measured using INVOS. Influence of age on variables at each measurement point was also checked using linear regression analysis. Receiver operating characteristics curve analysis was performed to determine the ability of vascular occlusion test variables at T2 to predict the occurrence of major adverse events. Both the deoxygenation and reoxygenation rates were lowest in T1. There was a tendency to decreased regional tissue hemoglobin oxygen saturation in younger patients at T0 (r = 0.37; p < 0.001), T1 (r = 0.33; p < 0.001), and T2 (r = 0.42; p < 0.001) during vascular occlusion. Minimum regional tissue hemoglobin oxygen saturation was correlated with age at T0 (r = 0.51; p < 0.001) and T2 (r = 0.35; p = 0.001). Patients with major adverse events had similar baseline regional tissue hemoglobin oxygen saturation but lower minimum regional tissue hemoglobin oxygen saturation (48.8% ± 19.3% vs 63.3% ± 13.9%; p < 0.001) and higher reoxygenation rate (4.30 ± 3.20 vs 2.57 ± 2.39 %/s; p = 0.008) at T2 compared with those without. The minimum regional tissue hemoglobin oxygen saturation less than 51% after sternal closure could predict the occurrence of major adverse events with a sensitivity of 61.1% and a specificity of 85.4%.

CONCLUSIONS

Vascular occlusion test using INVOS can be applied in children undergoing cardiac surgery. Vascular occlusion test variables are influenced by age and cardiopulmonary bypass. The minimum regional tissue hemoglobin oxygen saturation less than 51% after sternal closure is associated with worse clinical outcomes in pediatric cardiac patients.

A systematic review of human and veterinary applications of noninvasive tissue oxygen monitoring

OBJECTIVE

To describe the methodology for and utilization of tissue oxygen monitoring by near infrared spectroscopy, and to review the current literature on the use of this monitoring modality in human and veterinary settings.

DATA SOURCES

Scientific reviews and original research found using the PubMed and CAB Abstract search engines with the following keywords: "tissue oxygen monitoring," "near-infrared tissue spectroscopy," and "tissue oxygen saturation (StO2 )."

HUMAN DATA SYNTHESIS

Tissue oxygen monitors have been evaluated in a wide variety of human clinical applications including trauma and triage, surgery, sepsis, and septic shock, and early goal-directed therapy. StO2 more rapidly identifies occult shock in human patients compared to traditional methods, which can lead to earlier intervention in these patients.

VETERINARY DATA SYNTHESIS

Veterinary studies involving tissue oxygen monitoring are limited, but the technology may have utility for identification of hemorrhagic shock earlier than changes in base excess, blood lactate concentration, or other traditional perfusion parameters.

CONCLUSION

Tissue oxygen monitoring is most commonly performed utilizing a noninvasive, portable monitor, which provides real-time, continuous, repeatable StO2 measurements. A decline in StO2 is an early indicator of shock in both human and veterinary patients. Low StO2 values in human patients are associated with increased morbidity, mortality, and length of hospitalization, as well as the development of multiple organ system dysfunction and surgical site infections.

Journal of Clinical Monitoring and Computing 2015 end of year summary: tissue oxygenation and microcirculation

Last year we started this series of end of year summaries of papers published in the 2014 issues of the Journal Of Clinical Monitoring And Computing with a review on near infrared spectroscopy (Scheeren et al. in J Clin Monit Comput 29(2):217-220, 2015). This year we will broaden the scope and include papers published in the field of tissue oxygenation and microcirculation, or a combination of both entities. We present some promising new technologies that might enable a deeper insight into the (patho)physiology of certain diseases such as sepsis, but also in healthy volunteers. These may help researchers and clinicians to evaluate both tissue oxygenation and microcirculation beyond macro-hemodynamic measurements usually available at the bedside.

Near-infrared spectroscopy to assess microvascular dysfunction: A prospective pilot study in cardiac surgery patients

PURPOSE

The diagnosis of microvascular dysfunction remains challenging after cardiac surgery. We hypothesized that peripheral near-infrared spectroscopy (NIRS) monitoring in combination with a vascular occlusion test could reliably assess postoperative microvascular dysfunction in that setting.

MATERIALS AND METHODS

Twenty-two patients undergoing cardiac surgery with cardiopulmonary bypass and 10 healthy volunteers were prospectively investigated. Relevant NIRS parameters (regional tissue oxygen saturation, desaturation, and resaturation rates) were recorded the day before surgery (D-1), at the arrival in the intensive care unit (postoperative day [POD] 0) and on POD 1 and POD 2.

RESULTS

No difference in NIRS parameters was found at baseline between healthy volunteers and cardiac surgical patients. Absolute values of regional tissue oxygen saturation significantly increased at POD 0 and POD 1 when compared with D-1: 78% (75%-81%) and 75% (73%-78%) vs 68% (64%-72%), P < .001. No statistical difference was evidenced within the postoperative period in desaturation and resaturation rates compared with D-1: desaturation rate, 0.11% · s(-1) (0.08-0.14) and 0.15% · s(-1) (0.08-0.22) vs 0.14% · s(-1) (0.10-0.17), P = .233, and resaturation rate, 0.76% · s(-1) (0.41-1.11) and 0.77% · s(-1) (0.53-1.02) vs 0.79% · s(-1) (0.61-0.97), P = .453. The use of postoperative norepinephrine infusion did not change the results.

CONCLUSIONS

Peripheral NIRS monitoring in combination with a vascular occlusion test failed to assess cardiopulmonary bypass-induced microvascular dysfunction.

Hemodynamics and tissue oxygenation during balanced anesthesia with a high antinociceptive contribution: an observational study

BACKGROUND

In particular surgical conditions, a balanced anesthesia with a high-antinociceptive contribution is required. This may induce cardiovascular impairment and thus compromise tissue oxygenation. In this prospective observational study, we investigated the hemodynamic stability and tissue oxygen saturation (StO2) in 40 patients with a high-antinociceptive general anesthesia, goal-directed fluid therapy, and norepinephrine. In addition, optimal surgical conditions and safe and fast emergence are pivotal parts of anesthetic management.

METHODS

In high-antinociceptive propofol/remifentanil anesthesia with bispectral index (BIS) between 40 and 60, norepinephrine was administered to maintain mean arterial pressure (MAP) above 80% of individual baseline. Fluid was administered if the ∆ plethysmographic waveform amplitude exceeded 10%. Surgical and recovery conditions, hemodynamic responses, and tissue oxygenation were investigated.

RESULTS

Mean (SD) StO2 at the left thenar eminence increased from 83 (6)% before to 86 (4)% 20 min after induction of anesthesia (p <0.05). Cardiac index dropped from 3.0 (0.7) to 2.1 (0.4) L min(-1) (p <0.05), MAP from 109 (16) to 83 (14) mm Hg, and heart rate from 73 (12) to 54 (8) bpm (p <0.05). Thirteen out of 40 patients received a fluid bolus. The median (range) norepinephrine administration rate was 0.05 (0.0-0.10) μg kg(-1) min(-1). After complete akinesia in all patients during surgery, a median (IQR) extubation time of 311 (253-386) s was observed.

CONCLUSIONS

This high-antinociceptive balanced anesthesia with goal-directed fluid and vasopressor therapy adequately preserved StO2 and hemodynamic homeostasis.

TRIAL REGISTRATION

ISRCTN20153044.

Lower limb peripheral NIRS parameters during a vascular occlusion test: an experimental study in healthy volunteers

OBJECTIVES

The aim of the study was to compare NIRS parameters in combination with a vascular occlusion test (VOT) at a proximal (leg) and a distal (foot) site in male and female.

STUDY DESIGN

A prospective experimental study in healthy subjects.

PATIENTS AND METHODS

Twenty volunteers (10 male, 10 female, 28 ± 4 years) were investigated during 4 experimental steps: baseline, ischemia, reperfusion, and baseline. For each volunteer, 3 NIRS optodes were placed on right and left calves and the left arch of the foot. Blood pressure, heart rate and peripheral pulse oxymetry were monitored.

RESULTS

Significant differences were observed at baseline between regional oxygen saturation (rSO₂) values according to the site of measurement (proximal rSO₂ 81 ± 9% vs distal rSO₂ 60 ± 5%, P<0.001) but not according to gender. Both decreases in proximal and distal rSO₂ during ischemia and increases over baseline values during reperfusion depended on group membership (male or female). NIRS parameters during the VOT were significantly higher in male when compared with female at the proximal site: desaturation rate 5.6% (IQR: 5.5) vs 2.5% (IQR: 0.8), P=0.001; resaturation rate 40.7% (IQR: 6.6) vs 21.7% (IQR: 5.4), P=0.003; and ΔrSO₂ 10.0% (IQR: 7.0) vs 5.5% (IQR: 6.0), P=0.041.

CONCLUSIONS

Values of rSO₂ at the lower limb varied according to the anatomical site of measurement. A VOT induced major changes in rSO₂ that differed between male and female. These results should be taken into account in further clinical studies.

Dynamic evaluation of near-infrared peripheral oximetry in healthy volunteers: a comparison between INVOS and EQUANOX

PURPOSE

The present study aimed to compare peripheral regional tissue oxygen saturation (rSO2) values and desaturation/resaturation rates given by INVOS and EQUANOX devices.

MATERIALS AND METHODS

Twenty healthy volunteers were investigated during 4 experimental steps: baseline, hyperoxia, ischemia, and reperfusion. For each volunteer, 2 sensors INVOS and 2 sensors EQUANOX were placed on both left and right calves. Blood pressure, heart rate, and peripheral pulse oximetry were monitored.

RESULTS

Peripheral rSO2 ranged from 40% to 95% (INVOS) and from 47% to 100% (EQUANOX): 81±12 vs 82±9 (P=.469). A significant relationship was found at baseline between absolute values of INVOS and EQUANOX (n=40; R2=0.159; P=.011). Bias was -0.4%, and limits of agreement were ±15.1%. The percent maximum differences vs baseline values during dynamic maneuvers were 33%±19% (95% confidence interval, 24-42) and 21%±14% (95% confidence interval, 15-28) for INVOS and EQUANOX, respectively. No significant relationship was observed between percent maximum differences in INVOS and EQUANOX (n=20; R2=0.128; P=.122). Rates of desaturation/resaturation during occlusive vascular tests were 3.65% per minute vs 2.36% per minute (P=.027) and 30.42% per minute vs 16.28% per minute (P=.004) for INVOS and EQUANOX, respectively.

CONCLUSIONS

INVOS and EQUANOX are not comparable in measuring both absolute values and dynamic changes of peripheral rSO2 and near-infrared spectroscopy-derived parameters during occlusion vascular tests.