BackgroundCurrent research highlights the role of microcirculatory disorders in post-cardiac arrest patients. Affected microcirculation shows not only dissociation from systemic hemodynamics but also strong connection to outcome of these patients. However, only few studies evaluated microcirculation directly during cardiac arrest (CA) and cardiopulmonary resuscitation (CPR). The aim of our experimental study in a porcine model was to describe sublingual microcirculatory changes during CA and CPR using recent videomicroscopic technology and provide a comparison to parameters of global hemodynamics.MethodsCardiac arrest was induced in 18 female pigs (50 ± 3 kg). After 3 min without treatment, 5 min of mechanical CPR followed. Continuous hemodynamic monitoring including systemic blood pressure and carotid blood flow was performed and blood lactate was measured at the end of baseline and CPR. Sublingual microcirculation was assessed by the Sidestream Dark Field (SDF) technology during baseline, CA and CPR. Following microcirculatory parameters were assessed off-line separately for capillaries (≤20 µm) and other vessels: total and perfused vessel density (TVD, PVD), proportion of perfused vessels (PPV), microvascular flow index (MFI) and heterogeneity index (HI).ResultsIn comparison to baseline the CA small vessel microcirculation was only partially preserved: TVD 15.64 (13.59–18.48) significantly decreased to 12.51 (10.57–13.98) mm/mm2, PVD 15.57 (13.56–17.80) to 5.53 (4.17–6.60) mm/mm2, PPV 99.64 (98.05–100.00) to 38.97 (27.60–46.29) %, MFI 3.00 (3.00–3.08) to 1.29 (1.08–1.58) and HI increased from 0.08 (0.00–0.23) to 1.5 (0.71–2.00), p = 0.0003 for TVD and <0.0001 for others, respectively. Microcirculation during ongoing CPR in small vessels reached 59–85 % of the baseline values: TVD 13.33 (12.11–15.11) mm/mm2, PVD 9.34 (7.34–11.52) mm/mm2, PPV 72.34 (54.31–87.87) %, MFI 2.04 (1.58–2.42), HI 0.65 (0.41–1.07). The correlation between microcirculation and global hemodynamic parameters as well as to lactate was only weak to moderate (i.e. Spearman’s ρ 0.02–0.51) and after adjustment for multiple correlations it was non-significant.ConclusionsSublingual microcirculatory parameters did not correlate with global hemodynamic parameters during simulated porcine model of CA and CPR. SDF imaging provides additional information about tissue perfusion in the course of CPR.Electronic supplementary materialThe online version of this article (doi:10.1186/s12967-016-0934-5) contains supplementary material, which is available to authorized users.

Our experimental study confirmed that monitoring brain and peripheral rSO is an easy-to-use method, well reflecting the hemodynamics during CA. However, only brain rSO reflects the CPR efforts and might be used as a potential quality indicator for CPR.

Cardiac arrest represents a leading cause of mortality and morbidity in developed countries. Extracorporeal cardiopulmonary resuscitation (ECPR) increases the chances for a beneficial outcome in victims of refractory cardiac arrest. However, ECPR and post-cardiac arrest care are affected by high mortality rates due to multi-organ failure syndrome, which is closely related to microcirculatory disorders. Therefore, microcirculation represents a key target for therapeutic interventions in post-cardiac arrest patients. However, the evaluation of tissue microcirculatory perfusion is still demanding to perform. Novel videomicroscopic technologies (Orthogonal polarization spectral, Sidestream dark field and Incident dark field imaging) might offer a promising way to perform bedside microcirculatory assessment and therapy monitoring. This review aims to summarise the recent body of knowledge on videomicroscopic imaging in a cardiac arrest setting and to discuss the impact of extracorporeal reperfusion and other therapeutic modalities on microcirculation.

The effect of pulsatile blood flow on microcirculation during extracorporeal cardiopulmonary resuscitation (ECPR) is not elucidated; therefore, we designed an observational study comparing sublingual microcirculation in patients with refractory cardiac arrest (CA) with spontaneously pulsatile or low/nonpulsatile blood flow after treatment with ECPR. Microcirculation was assessed with Sidestream Dark Field technology in 12 patients with CA who were treated with ECPR and 12 healthy control subjects. Microcirculatory images were analyzed offline in a blinded fashion, and consensual parameters were determined for the vessels ≤20 μm. The patients' data, including actual hemodynamic parameters, were documented. Pulsatile blood flow was defined by a pulse pressure (PP) ≥ 15 mm Hg. Compared with the healthy volunteers, the patients who were treated with ECPR exhibited a significantly lower proportion of perfused capillaries (PPC); other microcirculatory parameters did not differ. The groups of patients with pulsatile (n = 7) versus low/nonpulsatile (n = 5) blood flow did not differ in regards to the collected data and hemodynamic variables (except for the PP and ejection fraction of the left ventricle) as well as microcirculatory parameters. In conclusion, microcirculation appeared to be effectively supported by ECPR in our group of patients with CA with the exception of the PPC. We found only nonsignificant contribution of spontaneous pulsatility to extracorporeal membrane oxygenation-generated microcirculatory blood flow.

The aims were to explore the effect of head-up tilt (HUT) to 30 and 60 degrees on hemodynamics and tissue oxygenation in anesthetized healthy swine. The data serve as a reference for a study of resuscitation efficacy at HUT such as during transport. Nine healthy swine (49±4 kg) were anesthetized and multiple sensors including myocardial pressure-volume loops catheter, carotid flow probe, blood pressure catheters, near infrared spectroscopy (NIRS) tissue oximetry and mixed venous oximetry (SVO2) catheter were introduced and parameters continuously recorded. Experimental protocol consisted of baseline in supine position (15 min), 30 degrees HUT (15 min), recovery at supine position (15 min) and 60 degrees HUT (5 min). Vacuum mattress was used for body fixation during tilts. We found that 30 and 60 degrees inclination led to significant immediate reduction in hemodynamic and oximetry parameters. Mean arterial pressure (mm Hg) decreased from 98 at baseline to 53 and 39, respectively. Carotid blood flow dropped to 47 % and 22 % of baseline values, end diastolic volume to 49 % and 53 % and stroke volume to 47 % and 45 % of baseline. SVO2 and tissue oximetry decreased by 17 and 21 percentage points. The values are means. In conclusions, within minutes, both 30 and 60 degrees head-up tilting is poorly tolerated in anesthetized swine. Significant differences among individual animals exist.