Impact of increased mean arterial pressure on skin microcirculatory oxygenation in vasopressor-requiring septic patients: an interventional study

A proof of concept for microcirculation monitoring using machine learning based hyperspectral imaging in critically ill patients: a monocentric observational study

BACKGROUND

Impaired microcirculation is a cornerstone of sepsis development and leads to reduced tissue oxygenation, influenced by fluid and catecholamine administration during treatment. Hyperspectral imaging (HSI) is a non-invasive bedside technology for visualizing physicochemical tissue characteristics. Machine learning (ML) for skin HSI might offer an automated approach for bedside microcirculation assessment, providing an individualized tissue fingerprint of critically ill patients in intensive care. The study aimed to determine if machine learning could be utilized to automatically identify regions of interest (ROIs) in the hand, thereby distinguishing between healthy individuals and critically ill patients with sepsis using HSI.

METHODS

HSI raw data from 75 critically ill sepsis patients and from 30 healthy controls were recorded using TIVITA® Tissue System and analyzed using an automated ML approach. Additionally, patients were divided into two groups based on their SOFA scores for further subanalysis: less severely ill (SOFA ≤ 5) and severely ill (SOFA > 5). The analysis of the HSI raw data was fully-automated using MediaPipe for ROI detection (palm and fingertips) and feature extraction. HSI Features were statistically analyzed to highlight relevant wavelength combinations using Mann-Whitney-U test and Benjamini, Krieger, and Yekutieli (BKY) correction. In addition, Random Forest models were trained using bootstrapping, and feature importances were determined to gain insights regarding the wavelength importance for a model decision.

RESULTS

An automated pipeline for generating ROIs and HSI feature extraction was successfully established. HSI raw data analysis accurately distinguished healthy controls from sepsis patients. Wavelengths at the fingertips differed in the ranges of 575-695 nm and 840-1000 nm. For the palm, significant differences were observed in the range of 925-1000 nm. Feature importance plots indicated relevant information in the same wavelength ranges. Combining palm and fingertip analysis provided the highest reliability, with an AUC of 0.92 to distinguish between sepsis patients and healthy controls.

CONCLUSION

Based on this proof of concept, the integration of automated and standardized ROIs along with automated skin HSI analyzes, was able to differentiate between healthy individuals and patients with sepsis. This approach offers a reliable and objective assessment of skin microcirculation, facilitating the rapid identification of critically ill patients.

IMPACT OF HIGH-DOSE VASOPRESSOR DURING ENDOTOXIC SHOCK ON THE CEREBRAL, LINGUAL, HEPATIC, AND RENAL MICROCIRCULATION EVALUATED BY NEAR-INFRARED SPECTROSCOPY IN SWINE

ABSTRACT

Background: High-dose vasopressors maintain blood pressure during septic shock but may adversely reduce microcirculation in vital organs. We assessed the effect of high-dose norepinephrine and vasopressin on the microcirculation of the brain, tongue, liver, and kidney during endotoxic shock using near-infrared spectroscopy (NIRS). Methods: Thirteen pigs (24.5 ± 1.8 kg) were anesthetized, and an NIRS probe was attached directly to each organ. Approximately 0.2, 0.5, 1, and 2 μg/kg/min of norepinephrine were administered in a stepwise manner, followed by 0.5, 1, 2, and 5 μg/kg/min of sodium nitroprusside in normal condition. Moreover, 1 μg/kg/h of lipopolysaccharide was administered continuously after 100 μg bolus to create endotoxic shock and after 1,000 mL of crystalloid infusion and high-dose norepinephrine (2, 5, 10, and 20 μg/kg/min) and vasopressin (0.6, 1.5, 3, and 6 U/min) were administered in a stepwise manner. The relationship between the MAP and each tissue oxygenation index (TOI) during vasopressor infusion was evaluated. Results: Three pigs died after receiving lipopolysaccharides, and 10 were analyzed. An increase of >20% from the baseline MAP induced by high-dose norepinephrine during endotoxic shock reduced the TOI in all organs except the liver. The elevation of MAP to baseline with vasopressin alone increased the kidney and liver TOIs and decreased the tongue TOI. Conclusion: Forced blood pressure elevation with high-dose norepinephrine during endotoxic shock decreased the microcirculation of vital organs, especially the kidney. Cerebral TOI may be useful for identifying the upper limit of blood pressure, at which norepinephrine impairs microcirculation.

INITIATION TIMING OF VASOPRESSOR IN PATIENTS WITH SEPTIC SHOCK: A SYSTEMATIC REVIEW AND META-ANALYSIS

ABSTRACT

Background: Vasopressor plays a crucial role in septic shock. However, the time for vasopressor initiation remains controversial. We conducted a systematic review and meta-analysis to explore its initiation timing for septic shock patients. Methods: PubMed, Cochrane Library, Embase, and Web of Sciences were searched from inception to July 12, 2023, for relevant studies. Primary outcome was short-term mortality. Meta-analysis was performed using Stata 15.0. Results: Twenty-three studies were assessed, including 2 randomized controlled trials and 21 cohort studies. The early group resulted in lower short-term mortality than the late group (OR [95% CI] = 0.775 [0.673 to 0.893], P = 0.000, I2 = 67.8%). The significance existed in the norepinephrine and vasopressin in subgroup analysis. No significant difference was considered in the association between each hour's vasopressor delay and mortality (OR [95% CI] = 1.02 [0.99 to 1.051], P = 0.195, I2 = 57.5%). The early group had an earlier achievement of target MAP ( P < 0.001), shorter vasopressor use duration ( P < 0.001), lower serum lactate level at 24 h ( P = 0.003), lower incidence of kidney injury ( P = 0.001), renal replacement therapy use ( P = 0.022), and longer ventilation-free days to 28 days ( P < 0.001). Conclusions: Early initiation of vasopressor (1-6 h within septic shock onset) would be more beneficial to septic shock patients. The conclusion needs to be further validated by more well-designed randomized controlled trials.

Bedside Hyperspectral Imaging and Organ Dysfunction Severity in Critically Ill COVID-19 Patients-A Prospective, Monocentric Observational Study

Hyperspectral imaging (HSI) is a non-invasive technology that provides information on biochemical tissue properties, including skin oxygenation and perfusion quality. Microcirculatory alterations are associated with organ dysfunction in septic COVID-19 patients. This prospective observational study investigated associations between skin HSI and organ dysfunction severity in critically ill COVID-19 patients. During the first seven days in the ICU, palmar HSI measurements were carried out with the TIVITA® tissue system. We report data from 52 critically ill COVID-19 patients, of whom 40 required extracorporeal membrane oxygenation (ECMO). HSI parameters for superficial tissue oxygenation (StO2) and oxygenation and perfusion quality (NPI) were persistently decreased. Hemoglobin tissue content (THI) increased, and tissue water content (TWI) was persistently elevated. Regression analysis showed strong indications for an association of NPI and weaker indications for associations of StO2, THI, and TWI with sequential organ failure assessment (SOFA) scoring. StO2 and NPI demonstrated negative associations with vasopressor support and lactate levels as well as positive associations with arterial oxygen saturation. These results suggest that skin HSI provides clinically relevant information, opening new perspectives for microcirculatory monitoring in critical care.

Hyperspectral imaging for perioperative monitoring of microcirculatory tissue oxygenation and tissue water content in pancreatic surgery - an observational clinical pilot study

BACKGROUND

Hyperspectral imaging (HSI) could provide extended haemodynamic monitoring of perioperative tissue oxygenation and tissue water content to visualize effects of haemodynamic therapy and surgical trauma. The objective of this study was to assess the capacity of HSI to monitor skin microcirculation and possible relations to perioperative organ dysfunction in patients undergoing pancreatic surgery.

METHODS

The hyperspectral imaging TIVITA® Tissue System was used to evaluate superficial tissue oxygenation (StO2), deeper layer tissue oxygenation (near-infrared perfusion index (NPI)), haemoglobin distribution (tissue haemoglobin index (THI)) and tissue water content (tissue water index (TWI)) in 25 patients undergoing pancreatic surgery. HSI parameters were measured before induction of anaesthesia (t1), after induction of anaesthesia (t2), postoperatively before anaesthesia emergence (t3), 6 h after emergence of anaesthesia (t4) and three times daily (08:00, 14:00, 20:00 ± 1 h) at the palm and the fingertips until the second postoperative day (t5-t10). Primary outcome was the correlation of HSI with perioperative organ dysfunction assessed with the perioperative change of SOFA score.

RESULTS

Two hundred and fifty HSI measurements were performed in 25 patients. Anaesthetic induction led to a significant increase of tissue oxygenation parameters StO2 and NPI (t1-t2). StO2 and NPI decreased significantly from t2 until the end of surgery (t3). THI of the palm showed a strong correlation with haemoglobin levels preoperatively (t2: r = 0.83, p < 0.001) and 6 h postoperatively (t4: r = 0.71, p = 0.001) but not before anaesthesia emergence (t3: r = 0.35, p = 0.10). TWI of the palm and the fingertip rose significantly between pre- and postoperative measurements (t2-t3). Higher blood loss, syndecan level and duration of surgery were associated with a higher increase of TWI. The perioperative change of HSI parameters (∆t1-t3) did not correlate with the perioperative change of the SOFA score.

CONCLUSION

This is the first study using HSI skin measurements to visualize tissue oxygenation and tissue water content in patients undergoing pancreatic surgery. HSI was able to measure short-term changes of tissue oxygenation during anaesthetic induction and pre- to postoperatively. TWI indicated a perioperative increase of tissue water content. Perioperative use of HSI could be a useful extension of haemodynamic monitoring to assess the microcirculatory response during haemodynamic therapy and major surgery.

TRIAL REGISTRATION

German Clinical Trial Register, DRKS00017313 on 5 June 2019.

Automatic Liver Viability Scoring with Deep Learning and Hyperspectral Imaging

Hyperspectral imaging (HSI) is a non-invasive imaging modality already applied to evaluate hepatic oxygenation and to discriminate different models of hepatic ischemia. Nevertheless, the ability of HSI to detect and predict the reperfusion damage intraoperatively was not yet assessed. Hypoxia caused by hepatic artery occlusion (HAO) in the liver brings about dreadful vascular complications known as ischemia-reperfusion injury (IRI). Here, we show the evaluation of liver viability in an HAO model with an artificial intelligence-based analysis of HSI. We have combined the potential of HSI to extract quantitative optical tissue properties with a deep learning-based model using convolutional neural networks. The artificial intelligence (AI) score of liver viability showed a significant correlation with capillary lactate from the liver surface (r = −0.78, p = 0.0320) and Suzuki’s score (r = −0.96, p = 0.0012). CD31 immunostaining confirmed the microvascular damage accordingly with the AI score. Our results ultimately show the potential of an HSI-AI-based analysis to predict liver viability, thereby prompting for intraoperative tool development to explore its application in a clinical setting.

Associations between peripheral perfusion disorders, mean arterial pressure and dose of norepinephrine administrated in the early phase of septic shock

The aim of the study was to explore the correlations between peripheral perfusion, mean arterial pressure and the dose-rate of norepinephrine (NE) infused for the treatment of septic shock. The study is retrospective analysis of data acquired prospectively on 57 patients during the first 24 hours after the occurrence of the shock. Clinical and haemodynamic characteristics, skin perfusion parameters (capillary refill time [CRT], mottling score and temperature gradients) and the dose rate of NE infusion were collected. Negative correlations between mean arterial pressure (MAP) and temperature gradients (core-to-toe: P = .03, core-to-index: P = .04) were found and abnormal CRT was associated with lower MAP (P = .02). The dose rate of NE was negatively correlated with temperature gradients (core-to-toe: P = .02, core-to-index: P = .01, forearm-to-index: P = .008) in the overall population. In patients receiving NE for at least 12 hours, the NE dose rate positively was correlated with the mottling score (P = .006), temperature gradients (core-to-toe: P = .04, forearm-to-index: P = .02, core-to-index: P = .005) and CRT (P = .001). The dose of NE administrated was associated with 14-days mortality (odds ration [OR] = 1.21 [1.06-1.38], P = .006) and with 28-days mortality (OR = 1.17 [1.01-1.36], P = 0.04). In conclusion, the study described the presence of correlations between peripheral perfusion and MAP and between peripheral perfusion and the dose rate of NE infusion.

Bedside hyperspectral imaging indicates a microcirculatory sepsis pattern - an observational study

INTRODUCTION

Microcirculatory alterations are key mechanisms in sepsis pathophysiology leading to tissue hypoxia, edema formation, and organ dysfunction. Hyperspectral imaging (HSI) is an emerging imaging technology that uses tissue-light interactions to evaluate biochemical tissue characteristics including tissue oxygenation, hemoglobin content and water content. Currently, clinical data for HSI technologies in critical ill patients are still limited.

METHODS AND ANALYSIS

TIVITA® Tissue System was used to measure Tissue oxygenation (StO2), Tissue Hemoglobin Index (THI), Near Infrared Perfusion Index (NPI) and Tissue Water Index (TWI) in 25 healthy volunteers and 25 septic patients. HSI measurement sites were the palm, the fingertip, and a suprapatellar knee area. Septic patients were evaluated on admission to the ICU (E), 6 h afterwards (E+6) and three times a day (t3-t9) within a total observation period of 72 h. Primary outcome was the correlation of HSI results with daily SOFA-scores.

RESULTS

Serial HSI at the three measurement sites in healthy volunteers showed a low mean variance expressing high retest reliability. HSI at E demonstrated significantly lower StO2 and NPI as well as higher TWI at the palm and fingertip in septic patients compared to healthy volunteers. StO2 and TWI showed corresponding results at the suprapatellar knee area. In septic patients, palm and fingertip THI identified survivors (E-t4) and revealed predictivity for 28-day mortality (E). Fingertip StO2 and THI correlated to SOFA-score on day 2. TWI was consistently increased in relation to the TWI range of healthy controls during the observation time. Palm TWI correlated positively with SOFA scores on day 3.

DISCUSSION

HSI results in septic patients point to a distinctive microcirculatory pattern indicative of reduced skin oxygenation and perfusion quality combined with increased blood pooling and tissue water content. THI might possess risk-stratification properties and TWI could allow tissue edema evaluation in critically ill patients.

CONCLUSION

HSI technologies could open new perspectives in microcirculatory monitoring by visualizing oxygenation and perfusion quality combined with tissue water content in critically ill patients - a prerequisite for future tissue perfusion guided therapy concepts in intensive care medicine.

Scores based on neutrophil percentage and lactate dehydrogenase with or without oxygen saturation predict hospital mortality risk in severe COVID-19 patients

Background

Risk scores are needed to predict the risk of death in severe coronavirus disease 2019 (COVID-19) patients in the context of rapid disease progression.

Methods

Using data from China (training dataset, n = 96), prediction models were developed by logistic regression and then risk scores were established. Leave-one-out cross validation was used for internal validation and data from Iran (test dataset, n = 43) was used for external validation.

Results

A NSL model (area under the curve (AUC) 0.932) and a NL model (AUC 0.903) were developed based on neutrophil percentage and lactate dehydrogenase with and without oxygen saturation (SaO₂) using the training dataset. AUCs of the NSL and NL models in the test dataset were 0.910 and 0.871, respectively. The risk scoring systems corresponding to these two models were established. The AUCs of the NSL and NL scores in the training dataset were 0.928 and 0.901, respectively. At the optimal cut-off value of NSL score, the sensitivity and specificity were 94% and 82%, respectively. The sensitivity and specificity of NL score were 94% and 75%, respectively.

Conclusions

These scores may be used to predict the risk of death in severe COVID-19 patients and the NL score could be used in regions where patients' SaO₂ cannot be tested.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12985-021-01538-8.

Vasopressors in septic shock: which, when, and how much?

In addition to fluid resuscitation, the vasopressor therapy is a fundamental treatment of septic shock-induced hypotension as it aims at correcting the vascular tone depression and then at improving organ perfusion pressure. Experts’ recommendations currently position norepinephrine (NE) as the first-line vasopressor in septic shock. Vasopressin and its analogues are only second-line vasopressors as strong recent evidence suggests no benefit of their early administration in spite of promising preliminary data. Early administration of NE may allow achieving the initial mean arterial pressure (MAP) target faster and reducing the risk of fluid overload. The diastolic arterial pressure (DAP) as a marker of vascular tone, helps identifying the patients who need NE urgently. Available data suggest a MAP of 65 mmHg as the initial target but a more individualized approach is often required depending on several factors such as history of chronic hypertension or value of central venous pressure (CVP). In cases of refractory hypotension, increasing NE up to doses ≥1 µg/kg/min could be an option. However, current experts’ guidelines suggest to combine NE with other vasopressors such as vasopressin, with the intent to rising the MAP to target or to decrease the NE dosage.

Early norepinephrine use in septic shock

As vascular tone depression is a hallmark of septic shock, administration of norepinephrine is logical in this setting. In this article, we provide and develop the following arguments for an early use of norepinephrine-the recommended first-line vasopressor-in septic shock: (I) prevention of prolonged severe hypotension, (II) increase in cardiac output through an increase in cardiac preload and/or contractility, (III) improvement of microcirculation and tissue oxygenation, (IV) prevention of fluid overload, and (V) improvement of outcome. Presence of a low diastolic arterial pressure as a marker of depressed vascular tone can be used as a trigger to initiate norepinephrine urgently.