Evaluating the Prevalence of Cardiac Surgery-associated Acute Kidney Injury After Septal Myectomy Combined With Concomitant Procedures in Obstructive Hypertrophic Cardiomyopathy.

OBJECTIVES: Hypertrophic obstructive cardiomyopathy (HOCM) may be treated by septal myectomy. Cardiac surgery-associated acute kidney injury (CSA-AKI) is a common complication, but little is known about its incidence after septal myectomy. The objectives of this work were to evaluate the prevalence of CSA-AKI after septal myectomy and identify potential perioperative and phenotype-related factors contributing to CSA-AKI. DESIGN: This was a retrospective database analysis with new data analysis. SETTING: The study occurred in a single university academic expertise center for septal myectomy HOCM patients. PARTICIPANTS: Data from 238 HOCM patients with septal myectomy operated on between 2005 and 2022 were collected. INTERVENTIONS: CSA-AKI was stratified according to the Kidney Disease: Improving Global Outcomes (KDIGO) guidelines using measurement of creatinine and urine production. Important HOCM phenotype-related and perioperative factors were analyzed for their possible associations with CSA-AKI. MEASUREMENTS AND MAIN RESULTS: CSA-AKI occurred in 45% of patients; of these, 55% were classified as KDIGO stage I and the remaining 45% as stage II, with no chronic kidney damage observed. Moreover, there were no phenotypical or perioperative characteristics that were more prevalent in the CSA-AKI cohort. However, the use of beta-blockers and coronary artery disease were more prevalent in the CSA-AKI cohort. CONCLUSIONS: CSA-AKI is a common complication after septal myectomy but was transient, and kidney function recovered in all patients.

Measuring Mitochondrial Oxygen Tension during Red Blood Cell Transfusion in Chronic Anemia Patients: A Pilot Study.

In light of the associated risks, the question has been raised whether the decision to give a blood transfusion should solely be based on the hemoglobin level. As mitochondria are the final destination of oxygen transport, mitochondrial parameters are suggested to be of added value. The aims of this pilot study were to investigate the effect of a red blood cell transfusion on mitochondrial oxygenation as measured by the COMET device in chronic anemia patients and to explore the clinical usability of the COMET monitor in blood transfusion treatments, especially the feasibility of performing measurements in an outpatient setting. To correct the effect of volume load on mitochondrial oxygenation, a red blood cell transfusion and a saline infusion were given in random order. In total, 21 patients were included, and this resulted in 31 observations. If patients participated twice, the order of infusion was reversed. In both the measurements wherein a blood transfusion was given first and wherein 500 mL of 0.9% saline was given first, the median mitochondrial oxygen tension decreased after red blood cell transfusion. The results of this study have strengthened the need for further research into the effect of blood transfusion tissue oxygenation and the potential role of mitochondrial parameters herein.

Monitoring of mitochondrial oxygen tension in the operating theatre: An observational study with the novel COMET® monitor.

INTRODUCTION: The newly introduced Cellular Oxygen METabolism (COMET®) monitor enables the measurement of mitochondrial oxygen tension (mitoPO2) using the protoporphyrin IX triplet state lifetime technique (PpIX-TSLT). This study aims to investigate the feasibility and applicability of the COMET® measurements in the operating theatre and study the behavior of the new parameter mitoPO2 during stable operating conditions. METHODS: In this observational study mitochondrial oxygenation was measured in 20 patients during neurosurgical procedures using the COMET® device. Tissue oxygenation and local blood flow were measured by the Oxygen to See (O2C). Primary outcomes included mitoPO2, skin temperature, mean arterial blood pressure, local blood flow and tissue oxygenation. RESULTS: All patients remained hemodynamically stable during surgery. Mean baseline mitoPO2 was 60 ± 19 mmHg (mean ± SD) and mean mitoPO2 remained between 40-60 mmHg during surgery, but tended to decrease over time in line with increasing skin temperature. CONCLUSION: This study presents the feasibility of mitochondrial oxygenation measurements as measured by the COMET® monitor in the operating theatre and shows the parameter mitoPO2 to behave in a stable and predictable way in the absence of notable hemodynamic alterations. The results provide a solid base for further research into the added value of mitochondrial oxygenation measurements in the perioperative trajectory.

Mitochondrial Oxygenation During Cardiopulmonary Bypass: A Pilot Study.

Objective: Adequate oxygenation is essential for the preservation of organ function during cardiac surgery and cardiopulmonary bypass (CPB). Both hypoxia and hyperoxia result in undesired outcomes, and a narrow window for optimal oxygenation exists. Current perioperative monitoring techniques are not always sufficient to monitor adequate oxygenation. The non-invasive COMET® monitor could be a tool to monitor oxygenation by measuring the cutaneous mitochondrial oxygen tension (mitoPO2). This pilot study examines the feasibility of cutaneous mitoPO2 measurements during cardiothoracic procedures. Cutaneous mitoPO2 will be compared to tissue oxygenation (StO2) as measured by near-infrared spectroscopy. Design and Method: This single-center observational study examined 41 cardiac surgery patients requiring CPB. Preoperatively, patients received a 5-aminolevulinic acid plaster on the upper arm to enable mitoPO2 measurements. After induction of anesthesia, both cutaneous mitoPO2 and StO2 were measured throughout the procedure. The patients were observed until discharge for the development of acute kidney insufficiency (AKI). Results: Cutaneous mitoPO2 was successfully measured in all patients and was 63.5 [40.0-74.8] mmHg at the surgery start and decreased significantly (p < 0.01) to 36.4 [18.4-56.0] mmHg by the end of the CPB run. StO2 at the surgery start was 80.5 [76.8-84.3]% and did not change significantly. Cross-clamping of the aorta and the switch to non-pulsatile flow resulted in a median cutaneous mitoPO2 decrease of 7 mmHg (p < 0.01). The cessation of the aortic cross-clamping period resulted in an increase of 4 mmHg (p < 0.01). Totally, four patients developed AKI and had a lower preoperative eGFR of 52 vs. 81 ml/min in the non-AKI group. The AKI group spent 32% of the operation time with a cutaneous mitoPO2 value under 20 mmHg as compared to 8% in the non-AKI group. Conclusion: This pilot study illustrated the feasibility of measuring cutaneous mitoPO2 using the COMET® monitor during cardiothoracic procedures. Moreover, in contrast to StO2, mitoPO2 decreased significantly with the increasing CPB run time. Cutaneous mitoPO2 also significantly decreased during the aortic cross-clamping period and increased upon the release of the clamp, but StO2 did not. This emphasized the sensitivity of cutaneous mitoPO2 to detect circulatory and microvascular changes.

In Vivo and Ex Vivo Mitochondrial Function in COVID-19 Patients on the Intensive Care Unit.

Mitochondrial dysfunction has been linked to disease progression in COVID-19 patients. This observational pilot study aimed to assess mitochondrial function in COVID-19 patients at intensive care unit (ICU) admission (T1), seven days thereafter (T2), and in healthy controls and a general anesthesia group. Measurements consisted of in vivo mitochondrial oxygenation and oxygen consumption, in vitro assessment of mitochondrial respiration in platelet-rich plasma (PRP) and peripheral blood mononuclear cells (PBMCs), and the ex vivo quantity of circulating cell-free mitochondrial DNA (mtDNA). The median mitoVO2 of COVID-19 patients on T1 and T2 was similar and tended to be lower than the mitoVO2 in the healthy controls, whilst the mitoVO2 in the general anesthesia group was significantly lower than that of all other groups. Basal platelet (PLT) respiration did not differ substantially between the measurements. PBMC basal respiration was increased by approximately 80% in the T1 group when contrasted to T2 and the healthy controls. Cell-free mtDNA was eight times higher in the COVID-T1 samples when compared to the healthy controls samples. In the COVID-T2 samples, mtDNA was twofold lower when compared to the COVID-T1 samples. mtDNA levels were increased in COVID-19 patients but were not associated with decreased mitochondrial O2 consumption in vivo in the skin, and ex vivo in PLT or PBMC. This suggests the presence of increased metabolism and mitochondrial damage.

In Vivo Assessment of Mitochondrial Oxygen Consumption.

The Protoporphyrin IX-Triplet State Lifetime Technique (PpIX-TSLT) has been proposed by us as a potential clinical noninvasive tool for monitoring mitochondrial function. We have been working on the development of mitochondrial respirometry for monitoring mitochondrial oxygen tension (mitoPO2) and mitochondrial oxygen consumption (mitoVO2) in skin. In this work, we describe the principles of the method in small experimental animals.

Monitoring of mitochondrial oxygenation during perioperative blood loss.

One of the challenges in the management of acute blood loss is to differentiate whether blood transfusion is required or not. The sole use of haemoglobin values might lead to unnecessary transfusion in individual cases. The suggestion is that mitochondrial oxygen tension can be used as an additional monitoring technique to determine when blood transfusion is required. In this case report, we report mitochondrial oxygen measurements in a patient with perioperative blood loss requiring blood transfusion.

Monitoring mitochondrial PO2: the next step.

PURPOSE OF REVIEW: To fully exploit the concept of hemodynamic coherence in resuscitating critically ill one should preferably take into account information about the state of parenchymal cells. Monitoring of mitochondrial oxygen tension (mitoPO2) has emerged as a clinical means to assess information of oxygen delivery and oxygen utilization at the mitochondrial level. This review will outline the basics of the technique, summarize its development and describe the rationale of measuring oxygen at the mitochondrial level. RECENT FINDINGS: Mitochondrial oxygen tension can be measured by means of the protoporphyrin IX-Triplet State Lifetime Technique (PpIX-TSLT). After validation and use in preclinical animal models, the technique has recently become commercially available in the form of a clinical measuring system. This system has now been used in a number of healthy volunteer studies and is currently being evaluated in studies in perioperative and intensive care patients in several European university hospitals. SUMMARY: PpIX-TSLT is a noninvasive and well tolerated method to assess aspects of mitochondrial function at the bedside. It allows doctors to look beyond the macrocirculation and microcirculation and to take the oxygen balance at the cellular level into account in treatment strategies.

Non-invasive versus ex vivo measurement of mitochondrial function in an endotoxemia model in rat: Toward monitoring of mitochondrial therapy.

Mitochondrial function has been predominantly measured ex vivo. Due to isolation and preservation procedures ex vivo measurements might misrepresent in vivo mitochondrial conditions. Direct measurement of in vivo mitochondrial oxygen tension (mitoPO2) and oxygen disappearance rate (ODR) with the protoporphyrin IX-triplet state lifetime technique (PpIX-TSLT) might increase our understanding of mitochondrial dysfunction in the pathophysiology of acute disease. LPS administration decreased mitochondrial respiration (ODR) in vivo but did not alter mitochondrial function as assessed with ex vivo techniques (high resolution respirometry and specific complex determinations). PpIX-TSLT measures in vivo mitoPO2 and ODR and can be applied non-invasively at the skin.

A monitor for Cellular Oxygen METabolism (COMET): monitoring tissue oxygenation at the mitochondrial level.

After introduction of the protoporphyrin IX-triplet state lifetime technique as a new method to measure mitochondrial oxygen tension in vivo, the development of a clinical monitor was started. This monitor is the "COMET", an acronym for Cellular Oxygen METabolism. The COMET is a non-invasive electrically powered optical device that allows measurements on the skin. The COMET is easy to transport, due to its lightweight and compact size. After 5-aminolevulinic acid application on the human skin, a biocompatible sensor enables detection of PpIX in the mitochondria. PpIX acts as a mitochondrially located oxygen-sensitive dye. Three measurement types are available in the touchscreen-integrated user interface, 'Single', 'Interval' and 'Dynamic measurement'. COMET is currently used in several clinical studies in our institution. In this first description of the COMET device we show an incidental finding during neurosurgery. To treat persisting intraoperative hypertension a patient was administered clonidine, but due to rapid administration an initial phase of peripheral vasoconstriction occurred. Microvascular flow and velocity parameters measured with laser-doppler (O2C, LEA Medizintechnik) decreased by 44 and 16% respectively, but not the venous-capillary oxygen saturation. However, mitochondrial oxygen tension in the skin detected by COMET decreased from a steady state of 48 to 16 mmHg along with the decrease in flow and velocity. We conclude that COMET is ready for clinical application and we see the future for this bedside monitor on the intensive care, operating theater, and testing of mitochondrial effect of pharmaceuticals.

Non-invasive monitoring of mitochondrial oxygenation and respiration in critical illness using a novel technique.

INTRODUCTION: Although mitochondrial dysfunction is proposed to be involved in the pathophysiology of sepsis, conflicting results are reported. Variation in methods used to assess mitochondrial function might contribute to this controversy. A non-invasive method for monitoring mitochondrial function might help overcome this limitation. Therefore, this study explores the possibility of in vivo monitoring of mitochondrial oxygen tension (mitoPO2) and local mitochondrial oxygen consumptionin in an endotoxin-induced septic animal model. METHODS: Animals (rats n = 28) were assigned to a control group (no treatment), or to receive lipopolysaccharide without fluid resuscitation (LPS-NR) or lipopolysaccharide plus fluid resuscitation (LPS-FR). Sepsis was induced by intravenous LPS injection (1.6 mg/kg during 10 min), fluid resuscitation was performed by continuous infusion of a colloid solution, 7 ml kg(-1) h(-1) and a 2-ml bolus of the same colloid solution. MitoPO2 and ODR were measured by means of the protoporphyrin IX-triplet state lifetime technique (PpIX-TSLT). Kinetic aspects of the drop in mitoPO2 were recorded during 60s of skin compression. ODR was derived from the slope of the mitoPO2 oxygen disappearance curve. Measurements were made before and 3 h after induction of sepsis. RESULTS: At baseline (t0) all rats were hemodynamically stable. After LPS induction (t1), significant (p < 0.05) hemodynamic changes were observed in both LPS groups. At t0, mitoPO2 and ODR were 59 ± 1 mmHg, 64 ± 3 mmHg, 68 ± 4 mmHg and 5.0 ± 0.3 mmHg s(-1), 5.3 ± 0.5 mmHg s(-1), 5.7 ± 0.5 mmHg s(-1) in the control, LPS-FR and LPS-NR groups, respectively; at t1 these values were 58 ± 5 mmHg, 50 ± 2.3 mmHg, 30 ± 3.3 mmHg and 4.5 ± 0.5 mmHg s(-1), 3.3 ± 0.3 mmHg s(-1), 1.8 ± 0.3 mmHg s(-1), respectively. At t1, only mitoPO2 showed a significant difference between the controls and LPS-NR. In contrast, at t1 both LPS groups showed a significantly lower ODR compared to controls. CONCLUSION: These data show the feasibility to monitor alterations in mitochondrial oxygen consumption in vivo by PpIX-TSLT in a septic rat model. These results may contribute to the development of a clinical device to monitor mitochondrial function in the critically ill.

In vivo assessment of mitochondrial oxygen consumption.

The protoporphyrin IX-triplet state lifetime technique (PpIX-TSLT) has been proposed by us as a potential clinical noninvasive tool for monitoring mitochondrial function. We have been working on the development of mitochondrial respirometry for monitoring mitochondrial oxygen tension (mitoPO2) and mitochondrial oxygen consumption (mitoVO2) in skin. In this work we describe the principles of the method in experimental animals.

Cutaneous mitochondrial respirometry: non-invasive monitoring of mitochondrial function.

The recently developed technique for measuring cutaneous mitochondrial oxygen tension (mitoPO2) by means of the Protoporphyrin IX-Triplet State Lifetime Technique (PpIX-TSLT) provides new opportunities for assessing mitochondrial function in vivo. The aims of this work were to study whether cutaneous mitochondrial measurements reflect mitochondrial status in other parts of the body and to demonstrate the feasibility of the technique for potential clinical use. The first part of this paper demonstrates a correlation between alterations in mitochondrial parameters in skin and other tissues during endotoxemia. Experiments were performed in rats in which mitochondrial dysfunction was induced by a lipopolysaccharide-induced sepsis (n = 5) and a time control group (n = 5). MitoPO2 and mitochondrial oxygen consumption (mitoVO2) were measured using PpIX-TSLT in skin, liver and buccal mucosa of the mouth. Both skin and buccal mucosa show a significant mitoPO2-independent decrease (P < 0.05) in mitoVO2 after LPS infusion (a decrease of 37 and 39% respectively). In liver both mitoPO2 and mitoVO2 decreased significantly (33 and 27% respectively). The second part of this paper describes the clinical concept of monitoring cutaneous mitochondrial respiration in man. A first prototype of a clinical PpIX-TSLT monitor is described and its usability is demonstrated on human skin. We expect that clinical implementation of this device will greatly contribute to our understanding of mitochondrial oxygenation and oxygen metabolism in perioperative medicine and in critical illness. Our ultimate goal is to develop a clinical monitor for mitochondrial function and the current results are an important step forward.

Cutaneous respirometry by dynamic measurement of mitochondrial oxygen tension for monitoring mitochondrial function in vivo.

Progress in diagnosis and treatment of mitochondrial dysfunction in chronic and acute disease could greatly benefit from techniques for monitoring of mitochondrial function in vivo. In this study we demonstrate the feasibility of in vivo respirometry in skin. Mitochondrial oxygen measurements by means of oxygen-dependent delayed fluorescence of protoporphyrin IX are shown to provide a robust basis for measurement of local oxygen disappearance rate (ODR). The fundamental principles behind the technology are described, together with an analysis method for retrievel of respirometry data. The feasibility and reproducibility of this clinically useful approach are demonstrated in a series of rats.

Validation of the protoporphyrin IX-triplet state lifetime technique for mitochondrial oxygen measurements in the skin.

Mitochondrial oxygen tension can be measured in vivo by means of oxygen-dependent quenching of delayed fluorescence of protoporphyrin IX (PpIX). Here we demonstrate that mitochondrial PO(2) (mitoPO(2)) can be measured in the skin of a rat after topical application of the PpIX precursor 5-aminolevulinic acid (ALA). Calibration of mitoPO(2) measurements was done by comparison with simultaneous measurements of the cutaneous microvascular PO(2) This was done under three different conditions: in normal skin tissue, in nonrespiration skin tissue due to the application of cyanide, and in anoxic skin tissue after the ventilation with 100% nitrogen. The results of this study show that it is feasible to measure the mitoPO(2) after the topical application of ALA cream by means of the PpIX-triplet state lifetime technique.

Microvascular and mitochondrial PO(2) simultaneously measured by oxygen-dependent delayed luminescence.

Measurement of tissue oxygenation is a complex task and various techniques have led to a wide range of tissue PO(2) values and contradictory results. Tissue is compartmentalized in microcirculation, interstitium and intracellular space and current techniques are biased towards a certain compartment. Simultaneous oxygen measurements in various compartments might be of great benefit for our understanding of determinants of tissue oxygenation. Here we report simultaneous measurement of microvascular PO(2) (µPO(2) ) and mitochondrial PO(2) (mitoPO(2) ) in rats. The µPO(2) measurements are based on oxygen-dependent quenching of phosphorescence of the near-infrared phosphor Oxyphor G2. The mitoPO(2) measurements are based on oxygen-dependent quenching of delayed fluorescence of protoporphyrin IX (PpIX). Favorable spectral properties of these porphyrins allow simultaneous measurement of the delayed luminescence lifetimes. A dedicated fiber-based time-domain setup consisting of a tunable pulsed laser, 2 red-sensitive gated photomultiplier tubes and a simultaneous sampling data-acquisition system is described in detail. The absence of cross talk between the channels is shown and the feasibility of simultaneous µPO(2) and mitoPO(2) measurements is demonstrated in rat liver in vivo. It is anticipated that this novel approach will greatly contribute to our understanding of tissue oxygenation in physiological and pathological circumstances.

Oxygen-dependent delayed fluorescence measured in skin after topical application of 5-aminolevulinic acid.

Mitochondrial oxygen tension can be measured in vivo by means of oxygen-dependent quenching of delayed fluorescence of protoporphyrin IX (PpIX). Here we demonstrate that delayed fluorescence is readily observed from skin in rat and man after topical application of the PpIX precursor 5-aminolevulinic acid (ALA). Delayed fluorescence lifetimes respond to changes in inspired oxygen fraction and blood supply. The signals contain lifetime distributions and the fitting of rectangular distributions to the data appears more adequate than mono-exponential fitting. The use of topically applied ALA for delayed fluorescence lifetime measurements might pave the way for clinical use of this technique.