Heart rate reduction with esmolol is associated with improved arterial elastance in patients with septic shock: a prospective observational study.

PURPOSE: Ventricular-arterial (V-A) decoupling decreases myocardial efficiency and is exacerbated by tachycardia that increases static arterial elastance (Ea). We thus investigated the effects of heart rate (HR) reduction on Ea in septic shock patients using the beta-blocker esmolol. We hypothesized that esmolol improves Ea by positively affecting the tone of arterial vessels and their responsiveness to HR-related changes in stroke volume (SV). METHODS: After at least 24 h of hemodynamic optimization, 45 septic shock patients, with an HR ≥95 bpm and requiring norepinephrine to maintain mean arterial pressure (MAP) ≥65 mmHg, received a titrated esmolol infusion to maintain HR between 80 and 94 bpm. Ea was calculated as MAP/SV. All measurements, including data from right heart catheterization, echocardiography, arterial waveform analysis, and norepinephrine requirements, were obtained at baseline and at 4 h after commencing esmolol. RESULTS: Esmolol reduced HR in all patients and this was associated with a decrease in Ea (2.19 ± 0.77 vs. 1.72 ± 0.52 mmHg l(-1)), arterial dP/dt max (1.08 ± 0.32 vs. 0.89 ± 0.29 mmHg ms(-1)), and a parallel increase in SV (48 ± 14 vs. 59 ± 18 ml), all p < 0.05. Cardiac output and ejection fraction remained unchanged, whereas norepinephrine requirements were reduced (0.7 ± 0.7 to 0.58 ± 0.5 µg kg(-1) min(-1), p < 0.05). CONCLUSIONS: HR reduction with esmolol effectively improved Ea while allowing adequate systemic perfusion in patients with severe septic shock who remained tachycardic despite standard volume resuscitation. As Ea is a major determinant of V-A coupling, its reduction may contribute to improving cardiovascular efficiency in septic shock.

Comparison between an uncalibrated pulse contour method and thermodilution technique for cardiac output estimation in septic patients.

BACKGROUND: The purpose of this study was to evaluate the reliability of a new uncalibrated pulse contour method, the MostCare, in determining cardiac output (CO) in septic patients. METHODS: Thirty patients with septic shock admitted to an intensive care unit, receiving a norepinephrine infusion and requiring haemodynamic monitoring with a pulmonary artery catheter, were prospectively enrolled. Thermodilution measurements of CO (ThD-CO) were considered as the 'gold standard'. MostCare was connected to the monitoring system of the radial arterial pressure waveform to obtain a continuous CO calculation (MostCare-CO). ThD-CO and MostCare-CO measurements were recorded at three different haemodynamic states: baseline (T1), after raising mean arterial pressure (MAP) to 90 mm Hg by increasing the norepinephrine infusion (T2), and after returning the MAP to baseline value by decreasing vasopressor therapy (T3). A Bland-Altman and linear regression analyses were performed. RESULTS: A total of 90 paired ThD-CO and MostCare-CO measures were obtained (range 4.1-13.9 litre min(-1) for ThD-CO and 4.5-13.5 litre min(-1) for MostCare-CO). A good correlation between ThD-CO and MostCare-CO was observed (R = 0.93). The mean bias between the two techniques was -0.26 litre min(-1) (sd 0.98 litre min(-1)) and the 95% limits of agreement were -2.22 to 1.70 litre min(-1). The percentage of error was 25%. Pearson's R was 0.94, 0.92, and 0.93 at T1, T2, and T3, respectively. CONCLUSIONS: MostCare-CO and ThD-CO showed a good agreement at each time of the study. The reliability of the MostCare system was not affected by the vascular tone changes produced by a norepinephrine infusion.

Relationship between N-terminal pro-B-type natriuretic peptide (Nt-proBNP) and cardiac cycle efficiency in cardiac surgery.

N-terminal pro-B-type natriuretic peptide (Nt-proBNP) is a peptide released from myocardium in response to ventricular wall stress and dysfunction. Nt-proBNP plasma levels are elevated in a variety of cardiovascular disorders and are largely used for diagnosis and treatment of cardiac diseases. The cardiac cycle efficiency (CCE) is a haemodynamic variable that represents the left ventricle wall stress and the heart's effort to maintain an adequate blood flow to tissues. We investigated the relationship between Nt-proBNP and CCE values in patients undergoing cardiac surgery. Twenty-five patients undergoing aortic valve replacement were studied. Plasma Nt-proBNP concentrations were performed by electroluminescence immunoassay before starting surgery (t0), at the end of extracorporeal circulation (t1) and 3 hours after surgery (t2). CCE measurements were acquired at the same intervals and correlations with Nt-proBNP levels were calculated. Nt-proBNP plasma concentration was 1430 ± 341 pg/ml at t0, peaked significantly at t1 (2129 ± 561 pg/ml, p<0.001) and moderately decreased at t2 (1924 ± 477 pg/ml, p<0.05). A direct correlation between Nt-proBNP measured at t0 and t1 was found (r=0.91, p<0.001). Overall, a negative correlation between CCE and proBNP values was found (r=-0.89, p<0.01). Correlations between CCE and Nt-proBNP were -0.91, -0.83 and -0.88, at t0, t1 and t2, respectively (p<0.01). Nt-proBNP levels reflect the severity of left ventricle dysfunction in patients undergoing cardiac surgery. CCE correlated well with serum Nt-proBNP levels and seems to be a useful variable to monitor the left ventricular stress and recovery during the various phases of surgery.

An angiographic evaluation of restenosis rate at a six-month follow-up of patients with ST-elevation myocardial infarction submitted to primary percutaneous coronary intervention.

BACKGROUND: Percutaneous coronary intervention (PCI) is considered to be the optimal type of revascularization in patients with ST-segment elevation myocardial infarction (STEMI). However, the long-term effectiveness of this procedure can be reduced by restenosis. This investigation was aimed at a prospective evaluation, in a group of STEMI patients of "the real world" (not involved in randomised trials), of the angiographic restenosis rate at a 6-month follow-up, and at identifying the relationship between restenosis and the patients' characteristics. MATERIALS AND METHODS: Our study population consisted of 123 patients with STEMI submitted to primary PCI to then undergo stress echocardiography 3 months after PCI and an angiographic evaluation at a 6-month follow-up. RESULTS: a) In real life the restenosis rate is quite high (42.3%); b) no correlation was found between patients' clinical characteristics and restenosis; c) restenosis rate was higher in patients with bare metal stents than in those with drug-eluting stents (55.8% vs. 11.1%; p<0.001); in patients with longer stents (21.6+/-8.62 vs 18.1+/-6.34 mm, p=0.015) and when more than one stent was implanted. Moreover, a consistent number of patients showed restenosis though asymptomatic. CONCLUSIONS: Our data suggest that primary PCI is associated with a high incidence of angiographic restenosis. No correlation was found between patients' clinical characteristics and restenosis. The length and the number of implanted stents seem to be associated with a more probable restenosis at six-month angiographic evaluation. Drug-eluting stent implantation seems to be associated with a lower incidence of restenosis even in STEMI patients.

Hemodynamic goal-directed therapy. A review.

Patients can show arterial pressure and cardiac index within the normal range and still be in circulatory shock if oxygen and metabolic demand is increased or blood flow distribution is altered.Lactate is produced in anaerobic environment to preserve cellular integrity and physicians use its blood concentration value as a reliable marker of tissue hypoxia and energy failure.The authors review the recent literature on the importance of mixed venous oxygen saturation (SvO(2)) as an early sign of inadequate DO(2) that precede the lactate production.

Most Care®: a minimally invasive system for hemodynamic monitoring powered by the Pressure Recording Analytical Method (PRAM).

Invasive hemodynamic monitoring is a cornerstone of the care of critically ill and hemodynamically unstable patients in both intensive care units and operating rooms. The assessment of cardiac output by means of the pulmonary artery catheter has been considered the clinical gold standard. Nevertheless, several concerns have been raised regarding its invasiveness, usefulness, and associated complica-tions. These disadvantages have led to the development, during the last years, of a number of less invasive technologies for cardiac output determination. Among them, those based on the analysis of a peripheral arterial waveform have become commonly used. Most Care(®) is a minimally invasive arterial pressure based monitor powered by the Pressure Recording Analytical Method (PRAM), the only algorithm that does not require prior calibration or pre-calculated parameters and which is based of flow. PRAM provides the measurement of the main factors of hemodynamics, such as systemic blood pressures, stroke volume, cardiac output, and vascular resistances. Moreover, dynamic indices of fluid responsiveness are continuously displayed. In the present paper, we reviewed the current literature focusing on advantages and limitations of PRAM.

Pressure recording analytical method (PRAM) for measurement of cardiac output during various haemodynamic states.

BACKGROUND: Cardiac output (CO) can be measured using the pressure recording analytical method (PRAM), which is a new, less invasive technique allowing beat-by-beat stroke volume monitoring from the pressure signals recorded in femoral or radial arteries. METHODS: We investigated PRAM by comparing its cardiac output (PRAM-CO) with paired measurements obtained by electromagnetic flowmetry (EM-CO) and by standard thermodilution (ThD-CO) during various haemodynamic states in a swine model. Nine pigs were monitored with a pulmonary artery catheter and a femoral artery catheter at baseline, in a hyperdynamic state produced by administration of dobutamine and in a hypodynamic state induced by progressive exsanguination. Bland-Altman analysis was used. RESULTS: One hundred and eight paired cardiac output values over a range of EM-CO of 1.8-10.4 litre min(-1) resulted. We found close agreement between the techniques. Mean bias between EM-CO and PRAM-CO was -0.03 litre min(-1) (precision 0.58 litre min(-1)). The 95% limits of agreement were -0.61 to +0.55 litre min(-1). Similar results between ThD-CO and PRAM-CO were found. CONCLUSIONS: In a porcine model we have demonstrated accuracy of PRAM during various haemodynamic states. PRAM is a reliable tool to detect changes in cardiac output in pigs and has ability as a basic research tool.

Effect of aspirin and ticlopidine on plasma tissue factor levels in stable and unstable angina pectoris.

Patients with unstable angina have an increased activation of the coagulation system. Aspirin and ticlopidine given in combination may potentiate each other by the combination of different action mechanisms and may reduce the risk of coronary occlusion and clinical instability. Plasma tissue factor (TF) levels collected into the stenotic coronary artery may be an index of TF expression within the vasculature. In 160 patients undergoing angioplasty for a 81+/-5% coronary lesion, we measured TF in blood samples collected from a vein and from the coronary ostium. Immediately after and 10 minutes after the dilation procedures the samples were withdrawn also beyond the lesion. Heparin 150 U/kg was given as an anticoagulant. All patients were pretreated with 250 mg/day of aspirin. One hundred twenty patients were randomly assigned to receive 24, 48, or 72 hours of ticlopidine treatment (250 mg/twice daily). TF levels did not increase during angioplasty but there was a significantly higher TF expression in unstable than in stable patients, irrespective of the invasiveness of debulking procedures. When ticlopidine was given for 72 hours, TF levels were similar to normal laboratory values both in stable and unstable patients. This combined antiplatelet pretreatment may be of benefit in unstable angina patients, with a favorable cost/benefit ratio.

Converse piezoelectric effect detected in fresh cow femur bone.

A piezoelectric effect has been reported to exist in biological tissues, in particular in dry bone. Since the precision and resolution now obtainable are much greater, we decided to verify the presence of the converse effect (dimensional change under the application of an electric field) in fresh bone samples, by using a very high sensitivity instrument. We took, in varying orientations, five fresh femur cylindrical bone specimens from a cow leg and placed them as a single piece, or as a stack of 10 thin interlayered slices from one specimen to improve sensitivity, in a special microwave double cavity differential dilatometer. The thickness of the specimen was approximately 10mm. The applied field strength for the nonstacked specimen was near 10 kV m-1. Thickness variation was measured along and across the electric field lines. We applied the electric field as a switched polarity square wave. This allows the thermal dilution of specimen warming and possible electrostriction effects, which are insensitive to the direction of the applied field, to be separated from an electromechanical effect which is sensitive to direction. Using coherent signal averaging over approximately 600 cycles to combat instrumental noise we observed nonthermal, nonelectrostrictional thickness variations in all samples. The amplitudes we observed were near 3 pm for the 1 cm nonstacked specimen, and the bone's responses to electric fields ranged from 26 to 38 fm V-1. With response magnitudes approximating those predicted theoretically for the converse piezoelectric effect in bone we conclude that the piezoelectric theory could not be falsified with our experiments.