Mitral annular dynamics are influenced by left ventricular load and contractility in an acute animal model.

The purpose of this study was to investigate the effects of loading conditions and left ventricular (LV) contractility on mitral annular dynamics. In 10 anesthetized pigs, eight piezoelectric transducers were implanted equidistantly around the mitral annulus. High-fidelity catheters measured left ventricular pressures and the slope of the end-systolic pressure-volume relationship (Ees ) determined LV contractility. Adjustments of pre- and afterload were done by constriction of the inferior caval vein and occlusion of the descending aorta. Mitral annulus area indexed to body surface area (MAAi ), annular circularity index (ACI), and non-planarity angle (NPA) were calculated by computational analysis. MAAi was more dynamic in response to loading interventions than ACI and NPA. However, MAAi maximal cyclical reduction (-Δr) and average deformational velocity (- v ¯ $$ \overline{v} $$ ) did not change accordingly (p = 0.31 and p = 0.22). Reduced Ees was associated to attenuation in MAAi -Δr and MAAi - v ¯ $$ \overline{v} $$ (r2 = 0.744; p = 0.001 and r2 = 0.467; p = 0.029). In conclusion, increased cardiac load and reduced LV contractility may cause deterioration of mitral annular dynamics, likely impairing coaptation and increasing susceptibility to valvular incompetence.

Left ventricular venting during extracorporeal membrane oxygenation; the effects on cardiac performance in a porcine model of critical post-cardiotomy failure.

INTRODUCTION: Left ventricular distension is a major concern with postcardiotomy veno-arterial extracorporeal membrane oxygenation (VA-ECMO) supporting a critical heart failure after cardiac surgery. This porcine study evaluates the effects of left ventricular venting on cardiac function during ECMO-supported circulation and after weaning from ECMO. METHODS: Twenty anaesthetised open-chest pigs were put on cardiopulmonary bypass with aortic cross-clamping and suboptimal cardioplegic arrest for 40 min. After declamping and defibrillation, the animals were supported by VA-ECMO for 180 min either with or without additional left ventricular venting. Continuous haemodynamic evaluations were performed at baseline and at cardiac arrest, during VA-ECMO and for 120 min after weaning from circulatory support. Left ventricular perfusion and function were evaluated with microspheres, pressure-volume loops and epicardial echocardiography at baseline and after 1 and 2 h with unsupported circulation. RESULTS: In vented animals both mean aortic and left ventricular peak systolic pressure increased at the end of the ECMO-supported period compared to those not vented and remained increased also after weaning. Both at 60 min and 120 min after weaning from circulatory support, left ventricular stroke work and pressure-volume area were increased in vented compared to not vented animals. At 120 min left ventricular stroke volume was increased in vented compared to not vented animals, myocardial perfusion did not differ. The left ventricular mechanical efficiency, defined as the ratio between pressure volume area and myocardial perfusion, was increased (53.2 ± 5 vs 36.2 ± 2.1 J/mL/g, p = 0.011) in vented- compared to not vented hearts. CONCLUSION: This experimental study demonstrate that left ventricular venting during post-cardiotomy veno-arterial ECMO for 3 h attenuates deterioration of left ventricular function and haemodynamics early after weaning from circulatory support.

Effects of Add-On Left Ventricular Assist Device to Extracorporeal Membrane Oxygenation During Refractory Cardiac Arrest in a Porcine Model.

This study evaluated the effects of extracorporeal membrane oxygenation (ECMO) in combination with a percutaneous adjunctive left ventricular assist device (LVAD) in a porcine model during 60 minutes of refractory cardiac arrest (CA). Twenty-four anesthetized swine were randomly allocated into three groups given different modes of circulatory assist: group 1: ECMO 72 ml/kg/min and LVAD; group 2: ECMO 36 ml/kg/min and LVAD; and group 3: ECMO 72 ml/kg/min. During CA and extracorporeal cardiopulmonary resuscitation (ECPR), mean left ventricular pressure (mLVP) was lower in group 1 (p = 0.013) and in group 2 (p = 0.003) versus group 3. Mean aortic pressure (mAP) and coronary perfusion pressure (CPP) were higher in group 1 compared with the other groups. In group 3, mean pulmonary artery flow (mPAf) was lower versus group 1 (p = 0.003) and group 2 (p = 0.039). If the return of spontaneous circulation (ROSC) was achieved after defibrillation, up to 180 minutes of unsupported observation followed. All subjects in groups 1 and 3, and 5 subjects in group 2 had ROSC. All subjects in group 1, five in group 2 and four in group 3 had sustained cardiac function after 3 hours of spontaneous circulation. Subjects that did not achieve ROSC or maintained cardiac function post-ROSC had lower mAP (p < 0.001), CPP (p = 0.002), and mPAf (p = 0.004) during CA and ECPR. Add-on LVAD may improve hemodynamics compared with ECMO alone during refractory CA but could not substitute reduced ECMO flow. Increased mAP and CPP could be related to ROSC rate and sustained cardiac function. Increased mLVP was related to poor post-ROSC cardiac function.

An experimental study on intraoperative recovery of recurrent laryngeal nerve function.

OBJECTIVE: If bilateral thyroid surgery is planned and staged thyroidectomy considered in case of loss of neuromonitoring signal (LOS), a waiting time of 20 minutes is suggested for evaluation of early nerve recovery. This recommendation is based on clinical observations and has not been thoroughly validated experimentally. METHODS: Sixteen pigs were randomly studied, and electromyogram (EMG) was continuously recorded during traction injury until an amplitude decrease of 70% from baseline (BL) (16 nerves) or LOS (16 nerves), and further during 40-minute recovery time. At the end of the experiments, vocal cord twitch was evaluated by video-laryngoscopy. RESULTS: In the 70% group, 8 of 16 nerves recovered to or above an amplitude of 50% of baseline after 20 minutes and finally one more after 40 minutes. In the LOS group, only one nerve showed recovery after 20 minutes and one more after 40 minutes. Video-laryngoscopy revealed good or strong vocal cord twitches, in 10 of 14 nerves in the 70% group and in only 2 of 14 nerves in the LOS group. CONCLUSIONS: The overall intraoperative recovery was low after LOS. Even after 70% amplitude depression, only half of the nerves showed recovery to amplitudes ≥50% of BL. Nerve recovery is dynamic, and a waiting time of 20 minutes seems appropriate for the identification of early nerve recovery before decisions are taken to continue or terminate surgery. The final EMG amplitude was not always well correlated with estimated vocal cord twitch, evaluated by video-laryngoscopy. This observation needs further investigation.

Balanced Biventricular Assist Versus Extracorporeal Membrane Oxygenation in Cardiac Arrest.

Mechanical assist devices in refractory cardiac arrest are increasingly employed. We compared the hemodynamics and organ perfusion during cardiac arrest with either veno-arterial extracorporeal membrane oxygenation (ECMO) or biventricular assisted circulation combining left- and right-sided impeller devices (BiPella) in an acute experimental setting. Twenty pigs were randomized in two equal groups receiving circulatory support either by ECMO or by BiPella during 40 minutes of ventricular fibrillation (VF) followed by three attempts of cardioversion, and if successful, 60 minute observation with spontaneous, unsupported circulation. Hemodynamic variables were continuously recorded. Tissue perfusion was evaluated by fluorescent microsphere injections. Cardiac function was visualized by intracardiac echocardiography. During VF device output, carotid flow, kidney perfusion, mean aortic pressure (AOPmean), and mean left ventricular pressure (LVPmean) were all significantly higher in the ECMO group, and serum-lactate values were lower compared with the BiPella group. No difference in myocardial or cerebral perfusion was observed between groups. In 15 animals with sustained cardiac function for 60 minutes after return of spontaneous circulation, left ventricular subendocardial blood flow rate averaged 0.59 ± 0.05 ml/min/gm during VF compared with 0.31 ± 0.07 ml/min/gm in five animals with circulatory collapse (p = 0.005). Corresponding values for the midmyocardium was 0.91 ± 0.06 vs. 0.65 ± 0.15 ml/min/gm (p = 0.085). Both BiPella and ECMO could sustain vital organ function. ECMO provided a more optimal systemic circulatory support related to near physiologic output. Myocardial tissue perfusion and sustained cardiac function were related to coronary perfusion pressure during VF, irrespective of mode of circulatory support.

Myocardial perfusion and cardiac dimensions during extracorporeal membrane oxygenation-supported circulation in a porcine model of critical post-cardiotomy failure.

INTRODUCTION: Venoarterial extracorporeal membrane oxygenation is widely used as mechanical circulatory support for severe heart failure. A major concern with this treatment modality is left ventricular distension due to inability to overcome the afterload created by the extracorporeal membrane oxygenation circuit. The present porcine study evaluates coronary circulation, myocardial perfusion and ventricular distension during venoarterial extracorporeal membrane oxygenation. METHODS: Ten anesthetized open-chest pigs were cannulated and put on cardiopulmonary bypass. Heart failure was achieved by 90 minutes of aortic cross-clamping with insufficient cardioplegic protection. After declamping, the animals were supported by venoarterial extracorporeal membrane oxygenation for 3 hours. Continuous haemodynamic measurements were performed at baseline, during cardiopulmonary bypass/aortic cross-clamping and during venoarterial extracorporeal membrane oxygenation. Fluorescent microsphere injections at baseline and after 1, 2 and 3 hours on venoarterial extracorporeal membrane oxygenation evaluated myocardial perfusion. Left ventricular function and distension were assessed by epicardial echocardiography. RESULTS: The myocardial injury caused by 90 minutes of ischaemia resulted in a poorly contracting myocardium, necessitating venoarterial extracorporeal membrane oxygenation in all animals. The circulatory support maintained the mean arterial blood pressure within a satisfactory range. A hyperaemic left anterior descending coronary artery flow while on extracorporeal membrane oxygenation was observed compared to baseline. Myocardial tissue perfusion measured by microspheres was low, especially in the subendocardium. Echocardiography revealed myocardial tissue oedema, a virtually empty left ventricle, and a left ventricular output that remained negligible throughout the extracorporeal membrane oxygenation run. CONCLUSION: Coronary artery blood flow is maintained during venoarterial extracorporeal membrane oxygenation after cardiopulmonary bypass and cardioplegic arrest despite severely affected performance of the left ventricle. Myocardial perfusion decreases, however, presumably due to rapid development of myocardial tissue oedema.

Vocal cord function during recurrent laryngeal nerve injury assessed by accelerometry and EMG.

OBJECTIVE: Gradual impairment of nerve conduction is expected to be tightly associated with simultaneous gradual loss of vocal cord contractility, related to the fact that injured axons are connected to a defined number of muscle cells. In clinical studies, there is a time gap between observed adverse electromyographic (EMG) changes and examination of vocal cord function. This study evaluates the impact of intraoperative EMG changes on synchronous vocal cord contractility by simultaneous use of continuous intraoperative neuromonitoring (C-IONM) and accelerometry for registration of actual vocal cord function at a given change of EMG amplitude. METHODS: EMG was obtained following vagus nerve stimulation by use of C-IONM. A vocal cord accelerometer probe that could be attached to the vocal cords was developed based on a LIS3DH ultra low-power high performance three axis linear accelerometer (STMicroelectronics, Geneva, Switzerland). Accelerometer data were registered continuously together with EMG data during traction injury of the recurrent laryngeal nerve (RLN) until an amplitude depression ≤100 µV. RESULTS: Six RLN from four immature domestic pigs were studied. Vocal cord contractility assessed by vocal cord accelerometry decreased in parallel with EMG amplitude, with significant correlations ranging from 0.707 to 0.968. CONCLUSION: Decrease of EMG amplitude during traction injury to the RLN injury is closely associated with a parallel drop in vocal cord contractility. LEVEL OF EVIDENCE: NA Laryngoscope, 130:1090-1096, 2020.

Left ventricular dysfunction after two hours of polarizing or depolarizing cardioplegic arrest in a porcine model.

INTRODUCTION: This experimental study compares myocardial function after prolonged arrest by St. Thomas' Hospital polarizing cardioplegic solution (esmolol, adenosine, Mg2+) with depolarizing (hyperkalaemic) St. Thomas' Hospital No 2, both administered as cold oxygenated blood cardioplegia. METHODS: Twenty anaesthetized pigs on tepid (34°C) cardiopulmonary bypass (CPB) were randomised to cardioplegic arrest for 120 min with antegrade, repeated, cold, oxygenated, polarizing (STH-POL) or depolarizing (STH-2) blood cardioplegia every 20 min. Cardiac function was evaluated at Baseline and 60, 150 and 240 min after weaning from CPB, using a pressure-conductance catheter and epicardial echocardiography. Regional tissue blood flow, cleaved caspase-3 activity and levels of malondialdehyde were evaluated in myocardial tissue samples. RESULTS: Preload recruitable stroke work (PRSW) was increased after polarizing compared to depolarizing cardioplegia 150 min after declamping (73.0±3.2 vs. 64.3±2.4 mmHg, p=0.047). Myocardial tissue blood flow rate was high in both groups compared to the Baseline levels and decreased significantly in the STH-POL group only, from 60 min to 150 min after declamping (p<0.005). Blood flow was significantly reduced in the STH-POL compared to the STH-2 group 240 min after declamping (p<0.05). Left ventricular mechanical efficiency, the ratio between total pressure-volume area and blood flow rate, gradually decreased after STH-2 cardioplegia and was significantly reduced compared to STH-POL cardioplegia after 150 and 240 min (p<0.05 for both). CONCLUSION: Myocardial protection for two hours of polarizing cardioplegic arrest with STH-POL in oxygenated blood is non-inferior compared to STH-2 blood cardioplegia. STH-POL cardioplegia alleviates the mismatch between myocardial function and perfusion after weaning from CPB.

Injury mechanisms and electromyographic changes after injury of the recurrent laryngeal nerve: Experiments in a porcine model.

BACKGROUND: Recurrent laryngeal nerve (RLN) injury during surgery may reveal differences in electromyographic (EMG) changes after sustained compression or traction. METHODS: In 20 pigs with the NIM-FLEX EMG-endotracheal tube, EMG was recorded at baseline, during sustained RLN compression, or traction until 70% amplitude decrease and during 30 minutes of recovery. RESULTS: Seventy percent amplitude decrease from baseline was reached after 110 ± 98 seconds (compression group) and 2034 ± 2108 seconds (traction group). Traction induced a pronounced latency increase, peaking at 122 ± 8% in contrast to compression with 106 ± 5% (P < .001). The EMG amplitude recovery to ≥50% of baseline failed in 7 nerves after compression and 8 nerves after traction. CONCLUSION: Compression caused a fast decrease of EMG amplitude with minor effects on latency. In contrast, RLN traction showed early and significant latency increase preceding a delayed amplitude decrease. Recovery rate of the EMG signals were similar in both groups.

Microvascular fluid exchange during CPB with deep hypothermia circulatory arrest or low flow.

OBJECTIVE: Use of deep hypothermic low-flow (DHLF) cardiopulmonary bypass (CPB) has been associated with higher fluid loading than the use of deep hypothermia circulatory arrest (DHCA). We evaluated whether these perfusion strategies influenced fluid extravasation rates and edema generation differently per-operatively. MATERIALS AND METHODS: Twelve anesthetized pigs, randomly allocated to DHLF (n = 6) or DHCA (n = 6), underwent 2.5 hours CPB with cooling to 20°C for 30 minutes (min), followed by 30 min arrested circulation (DHCA) or 30 min low-flow circulation (DHLF) before 90 min rewarming to normothermia. Perfusion of tissues, fluid requirements, plasma volumes, colloid osmotic pressures and total tissue water contents were recorded and fluid extravasation rates calculated. During the experiments, cerebral microdialysis was performed in both groups. RESULTS: Microvascular fluid homeostasis was similar in both groups, with no between-group differences, reflected by similar fluid extravasation rates, plasma colloid osmotic pressures and total tissue water contents. Although extravasation rates increased dramatically from 0.10 (0.11) ml/kg/min (mean with standard deviation in parentheses) and 0.16 (0.02) ml/kg/min to 1.28 (0.58) ml/kg/min and 1.06 (0.41) ml/kg/min (DHCA and DHLF, respectively) after the initiation of CPB, fluid filtrations during both cardiac arrest and low flow were modest and close to baseline values. Cerebral microdialysis indicated anaerobic metabolism and ischemic brain injury in the DHCA group. CONCLUSION: No differences in microvascular fluid exchange could be demonstrated as a direct effect of DHCA compared with DHLF. Thirty minutes of DHCA was associated with anaerobic cerebral metabolism and possible brain injury.

Myocardial energy metabolism and ultrastructure with polarizing and depolarizing cardioplegia in a porcine model.

OBJECTIVES: This study investigated whether the novel St. Thomas' Hospital polarizing cardioplegic solution (STH-POL) with esmolol/adenosine/magnesium offers improved myocardial protection by reducing demands for high-energy phosphates during cardiac arrest compared to the depolarizing St. Thomas' Hospital cardioplegic solution No 2 (STH-2). METHODS: Twenty anaesthetised pigs on tepid cardiopulmonary bypass were randomized to cardiac arrest for 60 min with antegrade freshly mixed, repeated, cold, oxygenated STH-POL or STH-2 blood cardioplegia every 20 min. Haemodynamic variables were continuously recorded. Left ventricular biopsies, snap-frozen in liquid nitrogen or fixed in glutaraldehyde, were obtained at Baseline, 58 min after cross-clamp and 20 and 180 min after weaning from bypass. Adenine nucleotides were evaluated by high-performance liquid chromatography, myocardial ultrastructure with morphometry. RESULTS: With STH-POL myocardial creatine phosphate was increased compared to STH-2 at 58 min of cross-clamp [59.9 ± 6.4 (SEM) vs 44.5 ± 7.4 nmol/mg protein; P < 0.025], and at 20 min after reperfusion (61.0 ± 6.7 vs 49.0 ± 5.5 nmol/mg protein; P < 0.05), ATP levels were increased at 20 min of reperfusion with STH-POL (35.4 ± 1.1 vs 32.4 ± 1.2 nmol/mg protein; P < 0.05). Mitochondrial surface-to-volume ratio was decreased with polarizing compared to depolarizing cardioplegia 20 min after reperfusion (6.74 ± 0.14 vs 7.46 ± 0.13 µm 2 /µm 3 ; P = 0.047). None of these differences were present at 180 min of reperfusion. From 150 min of reperfusion and onwards, cardiac index was increased with STH-POL; 4.8 ± 0.2 compared to 4.0 ± 0.2 l/min/m 2 ( P = 0.011) for STH-2 at 180 min. CONCLUSIONS: Polarizing STH-POL cardioplegia improved energy status compared to standard STH-2 depolarizing blood cardioplegia during cardioplegic arrest and early after reperfusion.

The influence of acute unloading on left ventricular strain and strain rate by speckle tracking echocardiography in a porcine model.

Noninvasive measurements of myocardial strain and strain rate by speckle tracking echocardiography correlate to cardiac contractile state but also to load, which may weaken their value as indices of inotropy. In a porcine model, we investigated the influence of acute dynamic preload reductions on left ventricular strain and strain rate and their relation to the pressure-conductance catheter-derived preload recruitable stroke work (PRSW) and peak positive first derivative of left ventricular pressure (LV-dP/dtmax). Speckle tracking strain and strain rate in the longitudinal, circumferential, and radial directions were measured during acute dynamic reductions of end-diastolic volume during three different myocardial inotropic states. Both strain and strain rate were sensitive to unloading of the left ventricle (P < 0.001), but the load dependency for strain rate was modest compared with strain. Changes in longitudinal and circumferential strain correlated more strongly to changes in end-diastolic volume (r = -0.86 and r = -0.72) than did radial strain (r = 0.35). Longitudinal, circumferential, and radial strain significantly correlated with LV-dP/dtmax (r = -0.53, r = -0.46, and r = 0.86), whereas only radial strain correlated with PRSW (r = 0.55). Strain rate in the longitudinal, circumferential and radial direction significantly correlated with both PRSW (r = -0.64, r = -0.58, and r = 0.74) and LV-dP/dtmax (r = -0.95, r = -0.70, and r = 0.85). In conclusion, the speckle tracking echocardiography-derived strain rate is more robust to dynamic ventricular unloading than strain. Longitudinal and circumferential strain could not predict load-independent contractility. Strain rates, and especially in the radial direction, are good predictors of preload-independent inotropic markers derived from conductance catheter.

Myocardial function after polarizing versus depolarizing cardiac arrest with blood cardioplegia in a porcine model of cardiopulmonary bypass.

OBJECTIVES: Potassium-based depolarizing St Thomas' Hospital cardioplegic solution No 2 administered as intermittent, oxygenated blood is considered as a gold standard for myocardial protection during cardiac surgery. However, the alternative concept of polarizing arrest may have beneficial protective effects. We hypothesize that polarized arrest with esmolol/adenosine/magnesium (St Thomas' Hospital Polarizing cardioplegic solution) in cold, intermittent oxygenated blood offers comparable myocardial protection in a clinically relevant animal model. METHODS: Twenty anaesthetized young pigs, 42 ± 2 (standard deviation) kg on standardized tepid cardiopulmonary bypass (CPB) were randomized (10 per group) to depolarizing or polarizing cardiac arrest for 60 min with cardioplegia administered in the aortic root every 20 min as freshly mixed cold, intermittent, oxygenated blood. Global and local baseline and postoperative cardiac function 60, 120 and 180 min after myocardial reperfusion was evaluated with pressure-conductance catheter and strain by Tissue Doppler Imaging. Regional tissue blood flow, cleaved caspase-3 activity, GRK2 phosphorylation and mitochondrial function and ultrastructure were evaluated in myocardial tissue samples. RESULTS: Left ventricular function and general haemodynamics did not differ between groups before CPB. Cardiac asystole was obtained and maintained during aortic cross-clamping. Compared with baseline, heart rate was increased and left ventricular end-systolic and end-diastolic pressures decreased in both groups after weaning. Cardiac index, systolic pressure and radial peak systolic strain did not differ between groups. Contractility, evaluated as dP/dtmax, gradually increased from 120 to 180 min after declamping in animals with polarizing cardioplegia and was significantly higher, 1871 ± 160 (standard error) mmHg/s, compared with standard potassium-based cardioplegic arrest, 1351 ± 70 mmHg/s, after 180 min of reperfusion (P = 0.008). Radial peak ejection strain rate increased and the load-independent variable preload recruitable stroke work was increased with polarizing cardioplegia after 180 min, 64 ± 3 vs 54 ± 2 mmHg (P = 0.018), indicating better preserved left ventricular contractility with polarizing cardioplegia. Phosphorylation of GRK2 in myocardial tissue did not differ between groups. Fractional cytoplasmic volume in myocytes was reduced in hearts arrested with polarizing cardioplegia, indicating reduction of cytoplasmic oedema. CONCLUSIONS: Polarizing oxygenated blood cardioplegia with esmolol/adenosine/magnesium offers comparable myocardial protection and improves contractility compared with the standard potassium-based depolarizing blood cardioplegia.

Haemodynamic differences between pancuronium and vecuronium in an experimental pig model.

OBJECTIVE: To compare baseline cardiovascular function in anesthetised pigs using either pancuronium or vecuronium as a neuromuscular blocker. STUDY DESIGN: Retrospective, non-randomized comparison. ANIMALS: Norwegian Land Race pigs (Sus scrofa domesticus) weighing mean 42 ± SD 3 kg. METHODS: One hundred and sixteen animals from four different research protocols premedicated with identical doses of ketamine, diazepam, atropine and isoflurane, and anaesthetised with pentobarbital, fentanyl, midazolam and N(2)O were arranged into three uniform groups with respect to neuromuscular blocking agent: pancuronium bolus of 0.063 mg kg(-1) followed by 0.14 mg kg(-1) hour(-1) (n = 54), low-dose vecuronium 0.4 mg kg(-1) /0.2 mg kg(-1) hour(-1) (n = 29) and high-dose vecuronium 0.6 mg kg(-1) /0.3 mg kg(-1) hour(-1) (n = 33). RESULTS: The majority of cardiovascular parameters demonstrated no significant differences between groups. For heart rate, there was an overall group difference, p = 0.036. Dromotropy was low in the pancuronium group, with an increased normalised PR-interval compared to the high-dose vecuronium group, median 0.200 interquartile range (0.190, 0.215) versus 0.182 (0.166, 0.199), p < 0.05. Left ventricular compliance was increased in pancuronium-treated animals, demonstrated as a reduction in the nonlinear end-diastolic pressure volume relationship ß compared to both vecuronium groups, 0.021 (0.016, 0.025) versus 0.031 (0.025, 0.046) and 0.031 (0.022, 0.048), p < 0.05. The linear end-diastolic pressure volume relationship EDPVR(lin) was reduced as well in the pancuronium group, compared to the low-dose vecuronium group, 0.131 (0.116, 0.169) versus 0.181 (0.148, 0.247), p < 0.05. CONCLUSIONS: There are only minor haemodynamic differences when using pancuronium compared to vecuronium in the fentanyl-pentobarbital-midazolam-N(2)O anesthetised domestic pigs. Furthermore, increasing doses of vecuronium have minimal haemodynamic effects. CLINICAL RELEVANCE: Experimental studies in pigs using either pancuronium or vecuronium as a neuromuscular blocking agent are comparable with regard to cardiac and haemodynamic performance.

DNA methylation of the CYP1A1 enhancer is associated with smoking-induced genetic alterations in human lung.

CYP1A1 (cytochrome P4501A1) catalyze the conversion of polycyclic aromatic hydrocarbons into reactive metabolites, which may induce DNA damage. We hypothesized that DNA methylation of the CYP1A1 enhancer could be involved in inter-individual differences in mRNA levels of CYP1A1 or affect the smoking-induced DNA damage in human lung. Using DNA bisulfite conversion and pyrosequencing, we show that DNA methylation of the CYP1A1 enhancer is affected by smoking. In adjacent histologically normal lung from lung cancer patients (n = 120), low levels of DNA methylation of the CYP1A1 enhancer were related to high levels of smoking-induced hydrophobic DNA adduct (p < 0.03), and to the presence of TP53 or K-ras mutations in the corresponding lung tumors (p < 0.03). We found an inverse correlation between DNA methylation of the CYP1A1 enhancer and mRNA levels in vivo (Spearman r = -0.54; p < 0.0001). Thus, in lung tumor tissues, the CYP1A1 enhancer hypermethylation was associated with lower mRNA levels compared to adjacent histologically normal tissue (p < 0.0001). In vitro, using a panel of cultured human lung cells, we found hypermethylation of the CYP1A1 enhancer in cancer cell lines and an inverse correlation between DNA methylation and mRNA levels (Spearman r = -0.53; p = 0.003). Altogether, our results indicated that low levels of DNA methylation of the CYP1A1 enhancer in histologically normal human lung were associated with high CYP1A1 mRNA levels and with smoking-induced genetic alterations; thus, it may play a role in the initiation of lung carcinogenesis.

Antiapoptotic intervention in repeated blood cardioplegia: a porcine study of myocardial function.

BACKGROUND: Lethal reperfusion injury has been associated with apoptotic cell death. Insulin and insulin-like growth factors (IGF-I/IGF-II) may modulate this cell death when administered at the onset of reperfusion after ischemia. We explored if antiapoptotic treatment with IGF-II could influence left ventricular function in an experimental model with cardiopulmonary bypass and repeated oxygenated blood cardioplegia. METHODS: Twenty pigs underwent cardiopulmonary bypass with aortic cross-clamping for 60 minutes. In controls, hearts were arrested with cold, oxygenated blood cardioplegia repeated after 20 and 40 minutes. In the intervention group IGF-II was added to the cardioplegic solution at 20 and 40 minutes. After declamping and weaning from cardiopulmonary bypass, left ventricular global and local function was evaluated with a conductance catheter and tissue velocity imaging. Three hours after declamping the anterior left ventricle wall was divided in three layers and studied for blood flow rate with microspheres, Akt phosphorylation, and caspase-3 cleavage. Troponin-T levels were measured at baseline and after 3 hours of reperfusion. RESULTS: A reduction of myocardial levels of cleaved caspase-3 (p < 0.001) was found in the subendocardial wall layer and serum troponin-T was reduced (p < 0.025) in the IGF-II group 3 hours after declamping. In the IGF-II treated animals, left ventricular preload recruitable stroke work was low 1 hour after declamping and increased to levels higher than in controls (p < 0.025) 3 hours after declamping. Other cardiac variables did not differ between groups. CONCLUSIONS: When added to repeated cold blood cardioplegia, IGF-II reduces apoptosis and ischemia-reperfusion injury with minor effects on cardiac function.

A specific interleukin-1B haplotype correlates with high levels of IL1B mRNA in the lung and increased risk of non-small cell lung cancer.

Epidemiological evidence suggests a relationship between chronic inflammation and lung cancer. Inflammation in the lung may be modulated by host genetic factors such as polymorphisms in inflammatory genes. Identification of polymorphisms in inflammatory genes may help understanding interindividual differences in susceptibility to lung cancer. We have investigated single-nucleotide polymorphisms (SNPs) and their haplotypes in the regulatory region of the IL1B gene in association to non-small cell lung cancer (NSCLC) risk. Our previous work showed that two promoter SNPs C-511T and T-31C modulated NSCLC risk. In the present study, we show that G-3893A and G-1464C located in the enhancer region of the IL1B gene may also affect this risk, with odds for developing NSCLC being 0.69 [95% confidence interval (CI), 0.52-0.92] for -3893 A-allele and 0.63 (95% CI, 0.47 - 0.83) for -1464 C-allele. The associations were particularly prominent in patients with TP53 mutations in the tumor. Inference of the haplotype structures showed that -3893 G, -1464 G, -511 C and -31 T formed a specific haplotype (GGCT) with near complete linkage disequilibrium in lung cancer patients but not in controls. Furthermore, the risk haplotype (GGCT) was present in 65% of cases compared with 36% of controls. Quantitative analysis of RNA in normal lung tissue of the patients showed that the risk haplotype was correlated with significantly higher IL1B messenger RNA (mRNA) levels compared with the non-risk haplotype (ACTC). These data suggest that a specific IL1B haplotype associated with increased IL1B gene expression increases the risk of NSCLC.

A comprehensive analysis of phase I and phase II metabolism gene polymorphisms and risk of non-small cell lung cancer in smokers.

Lung cancer is a leading cause of cancer mortality worldwide with smoking and occupational exposure to carcinogenic compounds as the major risk factors. Susceptibility to lung cancer is affected by existence of polymorphic genes controlling the levels of metabolic activation and detoxification of carcinogens. We have investigated 105 single nucleotide polymorphisms (SNPs) in 31 genes from the phase I and phase II metabolism genes and antioxidant defense genes for association with the risk of non-small cell lung cancer (NSCLC) in a Norwegian population-based study. Our results indicate that several SNPs in the phase I genes, CYP1B1, CYP2D6, CYP2E1 and CYP3A4, are associated with the risk of NSCLC. Moreover, significant associations with multiple SNPs in the phase II genes ALDH2, COMT, EPHX1, SOD2, NAT1, NAT2, GSTM3, GSTP1, GSTT2 and MPO were also found. We prioritized our findings by use of two different recently developed Bayesian statistical tools, employing conservative prior probabilities of association. When we corrected for multiple testing using these statistical tools, three novel associations of NSCLC risk with SNPs in the CYP1B1 (Arg48Gly), COMT (Val158Met) and GSTT2 (Met139Ile) genes were found noteworthy. However, only four of the previously reported associations with polymorphisms in the GSTP1 (Ala14Val), SOD2 (Val16Ala), EPHX1 (His139Arg) genes and the NAT1 fast acetylator phenotype remained significantly associated with lung cancer.

Frequency of TP53 mutations in relation to Arg72Pro genotypes in non small cell lung cancer.

Mutations in the TP53 gene are important events during human lung carcinogenesis. The TP53 gene harbors several polymorphisms, and functional studies have shown that the Arg72Pro polymorphism alters both wild-type and mutant p53 protein activity. Thus, we hypothesized that certain Arg72Pro genotypes may influence the frequency and pattern of somatic mutations in TP53. We therefore examined the status of the Arg72Pro polymorphism and TP53 mutations in 260 non-small-cell lung cancer cases. Here we report a significant trend toward lower frequency of TP53 mutations with increasing number of Pro72 alleles (P = 0.02). Overall, Pro72 allele carriers had significantly lower frequency of TP53 mutations compared with Arg72 homozygotes (P = 0.02). In addition, carriage of the Pro72 variant was related to a lower frequency of mutations affecting the hotspot codon 273. Mutations at codon 273 accounted for 10.6% of the mutations in Arg72 homozygotes and 1.7% of the mutations in Pro72 allele carriers. Our results suggest that the genotype of the Arg72Pro polymorphism may modulate the frequency of TP53 mutations in non-small-cell lung cancer.

Sex differences in risk of lung cancer: Expression of genes in the PAH bioactivation pathway in relation to smoking and bulky DNA adducts.

It is controversial whether women have a higher lung cancer susceptibility compared to men. We previously reported higher levels of smoking-related bulky DNA adducts in female lungs. In a pilot study (27 cases), we also found a higher level of female lung cytochrome P4501A1 (CYP1A1) gene expression. In the present extended study we report on the pulmonary expression of several genes involved in polycyclic aromatic hydrocarbon bioactivation in relation to sex, smoking and DNA adducts. CYP1A1, CYP1B1, aryl hydrocarbon receptor and microsomal epoxide hydrolase gene expression was measured by quantitative real-time reverse transcriptase-PCR in 121 normal lung tissue samples. The expression of CYP1A1 and CYP1B1 was significantly higher among current smokers compared to ex-smokers and never-smokers. Among current smokers, females had a 3.9-fold higher median level of CYP1A1 compared to males (p = 0.011). CYP1B1 expression was not related to sex. Lung DNA adducts (measured by 32P-postlabeling) were highly significantly related to CYP1A1 (p < 0.0001) irrespective of smoking-status. Our results are consistent with the hypothesis that CYP1A1 plays a significant role in lung DNA adduct formation and support a higher susceptibility to lung cancer among females.