Microcirculation measurements: Barriers for use in clinical routine

Isoflurane, like sepsis, decreases CYP1A2 liver enzyme activity in intensive care patients: a clinical study and network model

PURPOSE

Liver function of intensive care patients is routinely monitored by static blood pathology. For specific indications, liver specific cytochrome activity may be measured by the commercially available maximum liver function capacity (LiMAx) test via quantification of the cytochrome P450 1A2 (CYP1A2) dependent C-methacetin metabolism. Sedation with the volatile anesthetic isoflurane was suspected to abrogate the correlation of LiMAx test with global liver function. We hypothesized that isoflurane has a CYP1A2-activity and LiMAx test result decreasing effect.

METHODS

In this monocentric, observational clinical study previously liver healthy intensive care patients, scheduled to be changed from propofol to isoflurane sedation, were enrolled. LiMAx testing was done before, during and after termination of isoflurane sedation.

RESULTS

The mean LiMAx value decreased during isoflurane sedation. Septic patients (n = 11) exhibited lower LiMAx values compared to non-septic patients (n = 11) at all time points. LiMAx values decreased with isoflurane from 140 ± 82 to 30 ± 34 µg kg-1 h-1 in the septic group and from 253 ± 92 to 147 ± 131 µg kg-1 h-1 in the non-septic group while laboratory markers did not imply significant hepatic impairment. Lactate increased during isoflurane inhalation without clinical consequence.

CONCLUSION

Sepsis and isoflurane have independently demonstrated an effect on reducing the hepatic CYP1A2-activity. A network model was constructed that could explain the mechanism through the influence of isoflurane on hypoxia inducible factor (HIF-1α) by upregulation of the hypoxia-inducible pathway and the downregulation of CYP1A2-activity via the ligand-inducible pathway. Thus, the increased anaerobic metabolism may result in lactate accumulation. The influence of isoflurane sedation on the validated correlation of global liver function with CYP1A2-activity measured by LiMAx testing needs to be investigated in more detail.

Immunomodulation by Hemoadsorption—Changes in Hepatic Biotransformation Capacity in Sepsis and Septic Shock: A Prospective Study

Background: Sepsis is often associated with liver dysfunction, which is an indicator of poor outcomes. Specific diagnostic tools that detect hepatic dysfunction in its early stages are scarce. So far, the immune modulatory effects of hemoadsorption with CytoSorb^® on liver function are unclear. Method: We assessed the hepatic function by using the dynamic LiMAx^® test and biochemical parameters in 21 patients with sepsis or septic shock receiving CytoSorb^® in a prospective, observational study. Points of measurement: T₁: diagnosis of sepsis or septic shock; T₂ and T₃: 24 h and 48 h after the start of CytoSorb^®; T₄: 24 h after termination of CytoSorb^®. Results: The hepatic biotransformation capacity measured by LiMAx^® was severely impaired in up to 95 % of patients. Despite a rapid shock reversal under CytoSorb^®, a significant improvement in LiMAx^® values appeared from T₃ to T₄. This decline and recovery of liver function were not reflected by common parameters of hepatic metabolism that remained mostly within the normal range. Conclusions: Hepatic dysfunction can effectively and safely be diagnosed with LiMAx^® in ventilated ICU patients under CytoSorb^®. Various static liver parameters are of limited use since they do not adequately reflect hepatic dysfunction and impaired hepatic metabolism.

Case report: Early detection of mesenteric ischemia by intravital microscopy in a patient with septic shock

Gut ischemia is a frequent but underdiagnosed complication, especially in critically ill intensive care patients, and represents a special diagnostic challenge that can only be solved in an interdisciplinary manner. We report a case of a 54-year-old woman with acute mesenteric ischemia (AMI) as a cause of septic shock diagnosed by intravital microscopy (IVM) 2 days before visible necrotic changes in a multimodality approach. We show that intravital microscopy can be a serious alternative for the early diagnosis of mesenteric ischemia in the hands of the skilled. We use this case to discuss the value and clinical perspective of IVM in the intensive care setting.

Therapeutic Modulation of the Host Defense by Hemoadsorption with CytoSorb®-Basics, Indications and Perspectives-A Scoping Review

The "normal" immune response to an insult triggers a highly regulated response determined by the interaction of various immunocompetent cells with pro- and anti-inflammatory cytokines. Under pathologic conditions, the massive elevation of cytokine levels ("cytokine storm") could not be controlled until the recent development of hemoadsorption devices that are able to extract a variety of different DAMPs, PAMPs, and metabolic products from the blood. CytoSorb® has been approved for adjunctive sepsis therapy since 2011. This review aims to summarize theoretical knowledge, in vitro results, and clinical findings to provide the clinician with pragmatic guidance for daily practice. English-language and peer-reviewed literature identified by a selective literature search in PubMed and published between January 2016 and May 2021 was included. Hemoadsorption can be used successfully as adjunct to a complex therapeutic regimen for various conditions. To the contrary, this nonspecific intervention may potentially worsen patient outcomes in complex immunological processes. CytoSorb® therapy appears to be safe and useful in various diseases (e.g., rhabdomyolysis, liver failure, or intoxications) as well as in septic shock or cytokine release syndrome, although a conclusive assessment of treatment benefit is not possible and no survival benefit has yet been demonstrated in randomized controlled trials.

High-dose CytoSorb hemoadsorption is associated with improved survival in patients with septic shock: A retrospective cohort study

BACKGROUND AND PURPOSE

Hemoadsorption with CytoSorb® offers a possible therapeutic approach in septic shock, but modes of application and dosing are still undetermined.

MATERIALS AND METHODS

Data from surgical patients with septic shock, treated with hemoadsorption adjunctive to renal replacement therapy were analyzed retrospectively. The 28-day mortality was compared to predicted mortality.

RESULTS

In 70 patients (70.6 ± 13.3 years), hemoadsorption was applied for 85.6 ± 53.8 h. The APACHE ll (30.2 ± 6.3) calculated to a predicted mortality of 73.3%, while the observed mortality was significantly lower (50%, p < 0.05). The amount of blood purified was higher in survivors than in non-survivors (8.5 ± 4.4 vs. 6.1 ± 3.6 l/kgBW, p = 0.017). We identified three clusters of <6 l/kgBW, 6-13 l/kgBW and ≥ 13 l/kgBW with a linear dose-response relation between blood purification volume and survival, which was best in the highest volume cluster (83.3%; p = 0.045).

CONCLUSIONS

The application of CytoSorb® seems to be effective in various conditions of septic shock. In a cohort of most severely ill patients the observed mortality was lower than predicted and decreased linearly with blood purification volumes inadvertently exceeding 6 l/kg BW. These results suggest that hemoadsorption might improve survival provided that the applied dose is high enough.

Assessing the Microcirculation With Handheld Vital Microscopy in Critically Ill Neonates and Children: Evolution of the Technique and Its Potential for Critical Care

Assuring adequate tissue oxygenation in the critically ill, but still developing child is challenging. Conventional hemodynamic monitoring techniques fall short in assessing tissue oxygenation as these are directed at the macrocirculation and indirect surrogates of tissue oxygenation. The introduction of handheld vital microscopy (HVM) has allowed for the direct visualization of the microcirculation and with this has offered insight into tissue oxygenation on a microcirculatory level. Since its introduction, technical improvements have been made to HVM, to both hardware and software, and guidelines have been developed through expert consensus on image assessment and analysis. Using HVM, the microcirculation of the skin, the buccal mucosa, and the sublingual mucosa of healthy and (critically) ill neonates and children have been visualized and investigated. Yet, integration of HVM in hemodynamic monitoring has been limited due to technical shortcomings. Only superficial microcirculatory beds can be visualized, inter-observer and intra-observer variabilities are not accounted for and image analysis happens offline and is semi-automated and time-consuming. More importantly, patients need to be cooperative or fully sedated to prevent pressure and movement artifacts, which is often not the case in children. Despite these shortcomings, observational research with HVM in neonates and children has revealed the following: (1) age-related developmental changes in the microcirculation, (2) loss of hemodynamic coherence, i.e., microcirculatory disturbances in the presence of a normal macrocirculation and, (3) microcirculatory disturbances which were independently associated with increased mortality risk. Although these observations underline the importance of microcirculatory monitoring, several steps have to be taken before integration in the decision process during critical care can happen. These steps include technological innovations to ease the use of HVM in the pediatric age group, measuring additional functional parameters of microvascular blood flow and integrated automated analysis software. As a next step, reference values for microcirculatory parameters need to be established, while also accounting for developmental changes. Finally, studies on microcirculatory guided therapies are necessary to assess whether the integration of microcirculatory monitoring will actually improve patient outcome. Nevertheless, HVM remains a promising, non-invasive tool to help physicians assure tissue oxygenation in the critically ill child.

Bridging the gap between basic research on microcirculation and clinical world: The translational marriage between engineering and medicine

The words "Translational" and "Medicine" have been recently coupled to indicate a combination of disciplines, resources, expertise, and techniques aimed at enhancing prevention, diagnosis, and therapies. As stated in 2015 by the European Society for Translational Medicine, translational medicine is "an interdisciplinary branch of the biomedical field supported by three main pillars: benchside, bedside and community". By definition, Translational Medicine is a highly interdisciplinary field, which gathers several specialties aimed at improving the global healthcare system.With regard to the assessment of the microcirculatory function, it is worthwhile to mention the growing interest from both basic research and clinical practice. Microcirculation is where the exchange of substances between blood and tissues takes place. Thus, it plays a key role in the pathophysiology of many diseases. Nonetheless, a gap does exist between the theoretical analysis of the microcirculatory function and its clinical exploitation. This gap can be due to the weak dissemination of analytical methods and theoretical results within the clinical community, which also delays the establishment of specific operative guidelines.This paper aims at encouraging, and possibly accelerating, the translation of basic research outcomes on microcirculatory function assessment into clinical applications.

Feasibility of optical coherence tomography angiography to assess changes in retinal microcirculation in ovine haemorrhagic shock

BACKGROUND

This study aimed to investigate the feasibility of optical coherence tomography angiography (OCT-A) for quantitative analysis of flow density to assess changes in retinal perfusion in an experimental model of haemorrhagic shock.

METHODS

Haemorrhagic shock was induced in five healthy, anaesthetized sheep by stepwise blood withdrawal of 3 × 10 ml∙kg- 1 body weight. OCT-A imaging of retinal perfusion was performed using an OCT device. Incident dark-field illumination microscopy videos were obtained for the evaluation of conjunctival microcirculation. Haemodynamic variables and flow density data in the OCT angiogram were analysed before and during progressive haemorrhage resulting in haemorrhagic shock as well as after fluid resuscitation with 10 ml∙kg- 1 body weight of balanced hydroxyethyl starch solution (6% HES 130/0.4). Videos of the conjunctival microcirculation were recorded at baseline, in haemorrhagic shock, and after resuscitation. Data are presented as median with interquartile range. Comparisons between time points were made using Friedman's test and the degree of correlation between two variables was expressed as Spearman's rank correlation coefficient.

RESULTS

Mean arterial pressure and cardiac index (CI) decreased and lactate concentration increased after induction of shock, and haemodynamics recovered after resuscitation. The flow density in the superficial retinal OCT angiogram decreased significantly after shock induction (baseline 44.7% (40.3; 50.5) vs haemorrhagic shock 34.5% (32.8; 40.4); P = 0.027) and recovered after fluid resuscitation (46.9% (41.7; 50.7) vs haemorrhagic shock; P = 0.027). The proportion of perfused vessels of the conjunctival microcirculation showed similar changes. The flow density measured using OCT-A correlated with the conjunctival microcirculation (perfused vessel density: Spearman's rank correlation coefficient ρ = 0.750, P = 0.001) and haemodynamic parameters (CI: ρ = 0.693, P < 0.001).

CONCLUSIONS

Retinal flow density, measured using OCT-A, significantly decreased in shock and recovered after fluid therapy in an experimental model of haemorrhagic shock. OCT-A is feasible to assess changes in retinal perfusion in haemorrhagic shock and fluid resuscitation.