Christa Boer

Reactive Oxygen Species Precede Protein Kinase C-δ Activation Independent of Adenosine Triphosphate–sensitive Mitochondrial Channel Opening in Sevoflurane-induced Cardioprotection

BackgroundIn the current study, the authors investigated the distinct role and relative order of protein kinase C (PKC)-&dgr;, adenosine triphosphate–sensitive mitochondrial K+ (mito K+ATP) channels, and reactive oxygen species (ROS) in the signal transduction of sevoflurane-induced cardioprotection and specifically addressed their mechanistic link. MethodsIsolated rat trabeculae were preconditioned with 3.8% sevoflurane and subsequently subjected to an ischemic protocol by superfusion of trabeculae with hypoxic, glucose-free buffer (40 min) followed by 60 min of reperfusion. In addition, the acute affect of sevoflurane on PKC-&dgr; and PKC-&egr; translocation and nitrotyrosine formation was established with use of immunofluorescent analysis. The inhibitors chelerythrine (6 &mgr;m), rottlerin (1 &mgr;m), 5-hydroxydecanoic acid sodium (100 &mgr;m), and n-(2-mercaptopropionyl)-glycine (300 &mgr;m) were used to study the particular role of PKC, PKC-&dgr;, mito K+ATP, and ROS in sevoflurane-related intracellular signaling. ResultsPreconditioning of trabeculae with sevoflurane preserved contractile function after ischemia. This contractile preservation was dependent on PKC-&dgr; activation, mito K+ATP channel opening, and ROS production. In addition, on acute stimulation by sevoflurane, PKC-&dgr; but not PKC-&egr; translocated to the sarcolemmal membrane. This translocation was inhibited by PKC inhibitors and ROS scavenging but not by inhibition of mito K+ATP channels. Furthermore, sevoflurane directly induced nitrosylation of sarcolemmal proteins, suggesting the formation of peroxynitrite. ConclusionsIn sevoflurane-induced cardioprotection, ROS release but not mito K+ATP channel opening precedes PKC-&dgr; activation. Sevoflurane induces sarcolemmal nitrotyrosine formation, which might be involved in the recruitment of PKC-&dgr; to the cell membrane.

Acute and delayed mild coagulopathy are related to outcome in patients with isolated traumatic brain injury

IntroductionThe relationship between isolated traumatic brain injury (TBI) associated coagulopathy and patient prognosis frequently lacks information regarding the time course of coagulation disorders throughout the post-traumatic period. This study was conducted to assess the prevalence and time course of post-traumatic coagulopathy in patients with isolated TBI and the relationship of these hemostatic disorders with outcome.MethodsThe local Human Subjects Committee approved the study. We retrospectively studied the medical records of computed tomography (CT)-confirmed isolated TBI patients with an extracranial abbreviated injury scale (AIS) <3 who were primarily referred to a Level 1 trauma centre in Amsterdam (n = 107). Hemostatic parameters including activated partial thromboplastin time (aPTT), prothrombin time (PT), platelet count, hemoglobin, hematocrit, glucose, pH and lactate levels were recorded throughout a 72-hour period as part of a routine standardized follow-up of TBI. Coagulopathy was defined as a aPPT >40 seconds and/or a PTT in International Normalized Ratio (INR) >1.2 and/or a platelet count <120*109/l.ResultsPatients were mostly male, aged 48 ± 20 years with a median injury severity score of 25 (range 20 to 25). Early coagulopathy as diagnosed in the emergency department (ED) occurred in 24% of all patients. The occurrence of TBI-related coagulopathy increased to 54% in the first 24 hours post-trauma. In addition to an increased age and disturbed pupillary reflex, both coagulopathy upon ED arrival and during the first 24 hours post-trauma provided an independent prognostic factor for unfavorable outcome (odds ratio (OR) 3.75 (95% CI 1.07 to 12.51; P = 0.04) and OR 11.61 (2.79 to 48.34); P = 0.003).ConclusionsOur study confirms a high prevalence of early and delayed coagulopathy in patients with isolated TBI, which is strongly associated with an unfavorable outcome. These data support close monitoring of hemostasis after TBI and indicate that correction of coagulation disturbances might need to be considered.

Right ventricular pacing improves right heart function in experimental pulmonary arterial hypertension: a study in the isolated heart

Right heart failure in pulmonary arterial hypertension (PH) is associated with mechanical ventricular dyssynchrony, which leads to impaired right ventricular (RV) function and, by adverse diastolic interaction, to impaired left ventricular (LV) function as well. However, therapies aiming to restore synchrony by pacing are currently not available. In this proof-of-principle study, we determined the acute effects of RV pacing on ventricular dyssynchrony in PH. Chronic PH with right heart failure was induced in rats by injection of monocrotaline (80 mg/kg). To validate for PH-related ventricular dyssynchrony, rats (6 PH, 6 controls) were examined by cardiac magnetic resonance imaging (9.4 T), 23 days after monocrotaline or sham injection. In a second group (10 PH, 4 controls), the effects of RV pacing were studied in detail, using Langendorff-perfused heart preparations. In PH, septum bulging was observed, coinciding with a reversal of the transseptal pressure gradient, as observed in clinical PH. RV pacing improved RV systolic function, compared with unpaced condition (maximal first derivative of RV pressure: +8.5 + or - 1.3%, P < 0.001). In addition, RV pacing markedly decreased the pressure-time integral of the transseptal pressure gradient when RV pressure exceeds LV pressure, an index of adverse diastolic interaction (-24 + or - 9%, P < 0.01), and RV pacing was able to resynchronize time of RV and LV peak pressure (unpaced: 9.8 + or - 1.2 ms vs. paced: 1.7 + or - 2.0 ms, P < 0.001). Finally, RV pacing had no detrimental effects on LV function or coronary perfusion, and no LV preexcitation occurred. Taken together, we demonstrate that, in experimental PH, RV pacing improves RV function and diminishes adverse diastolic interaction. These findings provide a strong rationale for further in vivo explorations.

Prehospital endotracheal intubation in patients with severe traumatic brain injury: Guidelines versus reality

The international Brain Trauma Foundation guidelines recommend prehospital endotracheal intubation in all patients with traumatic brain injury (TBI) and a Glasgow Coma Scale (GCS)< or =8. Close adherence to these guidelines is associated with improved outcome, but not all severely injured TBI patients receive adequate prehospital airway support. Here we hypothesized that guideline adherence varies when skills are involved that rely on training and expertise, such as endotracheal intubation. We retrospectively studied the medical records of CT-confirmed TBI patients with a GCS< or =8 who were referred to a level 1 trauma centre in Amsterdam (n=127). Records were analyzed for demographic parameters, prehospital treatment modalities, involvement of an emergency medical service (EMS) and respiratory and metabolic parameters upon arrival at the hospital. Patients were mostly male, aged 45+/-21 years with a median injury severity score (ISS) of 26. Of all patients for whom guidelines recommend endotracheal intubation, only 56% were intubated. In 21 out of 106 severe cases an EMS was not called for, suggesting low guideline adherence. Especially those TBI patients treated by paramedics tended to develop higher levels of stress markers like glucose and lactate. We observed a low degree of adherence to intubation guidelines in a Dutch urban area. Main reasons for low adherence were the unavailability of specialized care, scoop and run strategies and absence of a specialist physician in cases where intubation was recommended. The discrepancy between guidelines and reality warrants changing practice to improve guideline compliance and optimize outcome in TBI patients.

The diastolic flow-pressure gradient relation in coronary stenoses in humans.

OBJECTIVES We assessed the feasibility and reproducibility of the instantaneous diastolic coronary flow velocity-pressure gradient relation to characterize different degrees of coronary stenoses. BACKGROUND Assessment of the hemodynamic significance of coronary stenoses can be difficult. Using sensor-tipped guidewires, various physiologic indexes can be determined in the catheterization laboratory. Each of the current methods, however, has limitations. METHODS After positioning a Doppler flow wire and a pressure wire distal of a coronary stenosis, the flow velocity signals and the proximal and distal pressure were sampled simultaneously, at baseline and after intracoronary administration of adenosine. The instantaneous diastolic flow velocity and pressure gradient of single cardiac cycles at baseline, at maximal and intermediate hyperemia were plotted. Data were fitted with a regression line using the equation: Delta P = 0 +kv+Sv(2). Measurements were performed in 11 normal coronary arteries, 20 intermediate stenoses and in 7 severe stenoses before and after percutaneous transluminal coronary angioplasty plus stenting. RESULTS We found significant differences between normal coronary arteries, intermediate and severe stenoses. Percutaneous transluminal coronary angioplasty nearly normalized the highly abnormal flow-pressure gradient relation in the severe stenoses. A high degree of reproducibility was observed. In 3% of the measurements, analysis was not possible due to the occurrence of pressure drift or bad flow velocity signals. CONCLUSIONS It is feasible to assess the diastolic flow velocity-pressure gradient relation over a wide range of stenoses. It characterizes the hemodynamics of epicardial coronary stenoses and allows discrimination between normal coronary arteries, intermediate and severe stenoses.

Pulsatile flow during cardiopulmonary bypass preserves postoperative microcirculatory perfusion irrespective of systemic hemodynamics

The onset of nonpulsatile cardiopulmonary bypass is known to deteriorate microcirculatory perfusion, but it has never been investigated whether this may be prevented by restoration of pulsatility during extracorporeal circulation. We therefore investigated the distinct effects of nonpulsatile and pulsatile flow on microcirculatory perfusion during on-pump cardiac surgery. Patients undergoing coronary artery bypass graft surgery were randomized into a nonpulsatile (n = 17) or pulsatile (n = 16) cardiopulmonary bypass group. Sublingual mucosal microvascular perfusion was measured at distinct perioperative time intervals using sidestream dark field imaging, and quantified as the level of perfused small vessel density and microvascular flow index (vessel diameter < 20 μm). Microcirculation measurements were paralleled by hemodynamic and free hemoglobin analyses. The pulse wave during pulsatile bypass estimated 58 ± 17% of the baseline blood pressure waveform. The observed reduction in perfused vessel density during aorta cross-clamping was only restored in the pulsatile flow group and increased from 15.5 ± 2.4 to 20.3 ± 3.7 mm/mm(2) upon intensive care admission (P < 0.01). The median postoperative microvascular flow index was higher in the pulsatile group [2.6 (2.5-2.9)] than in the nonpulsatile group [2.1 (1.7-2.5); P = 0.001]. Pulsatile flow was not associated with augmentation of free hemoglobin production and was paralleled by improved oxygen consumption from 70 ± 14 to 82 ± 16 ml·min(-1)·m(-2) (P = 0.01) at the end of aortic cross-clamping. In conclusion, pulsatile cardiopulmonary bypass preserves microcirculatory perfusion throughout the early postoperative period, irrespective of systemic hemodynamics. This observation is paralleled by an increase in oxygen consumption during pulsatile flow, which may hint toward decreased microcirculatory heterogeneity during extracorporeal circulation and preservation of microcirculatory perfusion throughout the perioperative period.

Comparison of noninvasive continuous arterial waveform analysis (Nexfin) with transthoracic Doppler echocardiography for monitoring of cardiac output

STUDY OBJECTIVES To compare the Nexfin cardiac output (CO) with the CO obtained from transthoracic Doppler echocardiography (TTE) during routine cardiac function screening. DESIGN Observational clinical study. SETTING Echocardiography laboratory. PATIENTS 40 ASA physical status 1 and 2 patients scheduled for routine TTE examination. INTERVENTIONS None. MEASUREMENTS AND MAIN RESULTS In 40 patients scheduled for routine TTE examination, we obtained simultaneous CO measurements with Doppler ultrasound and derived from Nexfin blood pressure measurements. Correlation and level of agreement between Nexfin and TTE were analyzed using Pearson correlation coefficient and Bland-Altman plots. The Pearson correlation coefficient for Nexfin versus TTE was 0.68 (CI: 0.46 - 0.82, P < 0.0001). Bland-Altman analysis showed a bias of 0.51 ± 1.1 L/min and limits of agreement of -1.6 to 2.6 L/min, with a percentage error of 39%. CONCLUSIONS Considering limits of precision of CO measurements with Doppler echocardiography (± 30%), the agreement between noninvasive CO measurement with the Nexfin and TTE is reasonable.

The cardioprotective effect of sevoflurane depends on protein kinase C activation, opening of mitochondrial K(+)(ATP) channels, and the production of reactive oxygen species.

Several studies suggest that the cardioprotective effect of sevoflurane depends on protein kinase C (PKC) activation, mitochondrial K+ATP channel (mitoK+ATP) opening, and reactive oxygen species (ROS). However, evidence for their involvement was obtained in separate experimental models. Here, we studied the relative roles of PKC, mitoK+ATP, and ROS in sevoflurane-induced cardioprotection in one model. Rat trabeculae were subjected to simulated ischemia by applying metabolic inhibition (MI) through buffer containing NaCN, followed by 60-min reperfusion. Recovery of active force (Fa) was assessed as percentage of pre-MI force. In time controls, Fa amounted 60% ± 5% at the end of the experiment. The recovery of Fa after MI was reduced to 28% ± 5% (P = 0.045 versus time control), whereas sevoflurane reversed the detrimental effect of MI (Fa recovery, 67% ± 8%; P = 0.01 versus MI). The PKC inhibitor chelerythrine, the mitoK+ATP inhibitor 5-hydroxy decanoic, and the ROS scavenger N-(2-mercaptopropionyl)-glycine all completely abolished the protective effect of sevoflurane (recovery of Fa, 31% ± 8%, 33% ± 8%, and 24% ± 9% for chelerythrine, 5-hydroxy decanoic, and N-(2-mercaptopropionyl)-glycine, respectively). In conclusion, PKC activation, mitoK+ATP channel opening, and ROS production are all essential for sevoflurane-induced cardioprotection. These signaling events are arranged in series within a common signaling pathway, rather than in parallel cascades. Our findings implicate that the perioperative use of sevoflurane preserves cardiac function by preventing ischemia-reperfusion injury.

Prehospital management of severe traumatic brain injury: concepts and ongoing controversies

Purpose of review Prehospital management affects long-term outcome of patients with severe traumatic brain injury (TBI). This article reviews the current concepts and ongoing controversies of prehospital treatment of severe TBI. Recent findings Prehospital management focuses on the prevention of secondary brain injury and rapid transport to a neurotrauma center for definitive diagnosis and life– as well as brain-saving emergency treatment such as decompressive craniotomy. There is a broad consensus that adequate airway management, prevention of hypoxia, hypocapnia or hypercapnia, prevention of hypotension and control of hemorrhage represent preclinical therapeutic modalities that may contribute to improved survival in severe TBI. The precise role of prehospital endotracheal intubation, osmotic agents and early therapeutic hypothermia needs to be clarified in the context of time required for transportation, local infrastructure, geographical factors and availability of experienced emergency teams. Summary Prehospital management of TBI remains challenging. There are no universal objectives suitable to all patients. Randomized, controlled clinical trials are necessary for developing optimal protocols for paramedic and physician emergency medical teams.

Cardioprotection Via Activation of Protein Kinase C-δ Depends on Modulation of the Reverse Mode of the Na+/Ca2+ Exchanger

Background— Pretreatment with the volatile anesthetic sevoflurane protects cardiomyocytes against subsequent ischemic episodes caused by a protein kinase C (PKC)-&dgr; mediated preconditioning effect. Sevoflurane directly modulates cardiac Ca2+ handling, and because Ca2+ also serves as a mediator in other cardioprotective signaling pathways, possible involvement of the Na+/Ca2+ exchanger (NCX) in relation with PKC-&dgr; in sevoflurane-induced cardioprotection was investigated. Methods and Results— Isolated right ventricular rat trabeculae were subjected to simulated ischemia and reperfusion (SI/R), consisting of superfusion with hypoxic glucose-free buffer for 40 minutes after rigor development, followed by reperfusion with normoxic glucose containing buffer. Preconditioning with sevoflurane before SI/R improved isometric force development during contractile recovery at 60 minutes after the end of hypoxic superfusion (83±7% [sevo] versus 57±2% [SI/R];n=8; P<0.01). Inhibition of the reverse mode of the NCX by KB-R7943 (10 &mgr;mol/L) or SEA0400 (1 &mgr;mol/L) during preconditioning attenuated the protective effect of sevoflurane. KB-R7943 and SEA0400 did not have intrinsic effects on the contractile recovery. Furthermore, inhibition of the NCX in trabeculae exposed to sevoflurane reduced sevoflurane-induced PKC-&dgr; translocation toward the sarcolemma, as demonstrated by digital imaging fluorescent microscopy. The degree of PKC-&dgr; phosphorylation at serine643 as determined by western blot analysis was not affected by sevoflurane. Conclusions— Sevoflurane-induced cardioprotection depends on the NCX preceding PKC-&dgr; translocation presumably via increased NCX-mediated Ca2+ influx. This may suggest that increased myocardial Ca2+ load triggers the cardioprotective signaling cascade elicited by volatile anesthetic agents similar to other modes of preconditioning.