Estimating mean circulatory filling pressure in clinical practice: a systematic review comparing three bedside methods in the critically ill.

The bedside hemodynamic assessment of the critically ill remains challenging since blood volume, arterial-venous interaction and compliance are not measured directly. Mean circulatory filling pressure (P) is the blood pressure throughout the vascular system at zero flow. Animal studies have shown P provides information on vascular compliance, volume responsiveness and enables the calculation of stressed volume.

Comprehensive review: is it better to use the Trendelenburg position or passive leg raising for the initial treatment of hypovolemia?

Hypovolemia is a common clinical problem. The Trendelenburg position and passive leg raising (PLR) are routinely used in the initial treatment while awaiting fluid resuscitation. In this meta-analysis, we evaluated the hemodynamic effects of PLR and Trendelenburg positioning to determine which position had the most optimal effect on cardiac output (CO).

Comparing hemodynamic effects with three different measurement devices, of two methods of external leg compression versus passive leg raising in patients after cardiac surgery.

External leg compression (ELC) may increase cardiac output (CO) in fluid-responsive patients like passive leg raising (PLR). We compared the hemodynamic effects of two methods of ELC and PLR measured by thermodilution (COtd), pressure curve analysis Modelflow™ (COmf) and ultra-sound HemoSonic™ (COhs), to evaluate the method with the greatest hemodynamic effect and the most accurate less invasive method to measure that effect. We compared hemodynamic effects of two different ELC methods (circular, A (n = 16), vs.

Cardiac output response to norepinephrine in postoperative cardiac surgery patients: interpretation with venous return and cardiac function curves.

Objective: We studied the variable effects of norepinephrine infusion on cardiac output in postoperative cardiac surgical patients in whom norepinephrine increased mean arterial pressure. We hypothesized that the directional change in cardiac output would be determined by baseline cardiac function, as quantified by stroke volume variation, and the subsequent changes in mean systemic filling pressure and vasomotor tone.

Design: Intervention study.

Bedside assessment of total systemic vascular compliance, stressed volume, and cardiac function curves in intensive care unit patients.

Background: Mean systemic filling pressure (Pmsf) can be measured at the bedside with minimally invasive monitoring in ventilator-dependent patients using inspiratory hold maneuvers (Pmsf(hold)) as the zero flow intercept of cardiac output (CO) to central venous pressure (CVP) relation. We compared Pmsf(hold) with arm vascular equilibrium pressure during vascular occlusion (Pmsf(arm)) and their ability to assess systemic vascular compliance (Csys) and stressed volume by intravascular fluid administration.

Methods: In mechanically ventilated postoperative cardiac surgery patients, inspiratory holds at varying airway pressures and arm stop-flow maneuvers were performed during normovolemia and after each of 10 sequential 50-mL bolus colloid infusions.

Estimation of mean systemic filling pressure in postoperative cardiac surgery patients with three methods.

Purpose: To assess the level of agreement between different bedside estimates of effective circulating blood volume-mean systemic filling pressure (Pmsf), arm equilibrium pressure (Parm) and model analog (Pmsa)-in ICU patients.

Methods: Eleven mechanically ventilated postoperative cardiac surgery patients were studied. Sequential measures were made in the supine position, rotating the bed to a 30° head-up tilt and after fluid loading (500 ml colloid).

Determination of vascular waterfall phenomenon by bedside measurement of mean systemic filling pressure and critical closing pressure in the intensive care unit.

Background: Mean systemic filling pressure (Pmsf) can be determined at the bedside by measuring central venous pressure (Pcv) and cardiac output (CO) during inspiratory hold maneuvers. Critical closing pressure (Pcc) can be determined using the same method measuring arterial pressure (Pa) and CO. If Pcc > Pmsf, there is then a vascular waterfall.

Evaluation of mean systemic filling pressure from pulse contour cardiac output and central venous pressure.

Objective: The volemic status of a patient can be determined by measuring mean systemic filling pressure (Pmsf). Pmsf is obtained from the venous return curve, i.e.

Arm occlusion pressure is a useful predictor of an increase in cardiac output after fluid loading following cardiac surgery.

Background And Objective: In pharmacological research, arm occlusion pressure is used to study haemodynamic effects of drugs. However, arm occlusion pressure might be an indicator of static filling pressure of the arm. We hypothesised that arm occlusion pressure can be used to predict fluid loading responsiveness.

Peripheral vascular decoupling in porcine endotoxic shock.

Cardiac output measurement from arterial pressure waveforms presumes a defined relationship between the arterial pulse pressure (PP), vascular compliance (C), and resistance (R). Cardiac output estimates degrade if these assumptions are incorrect. We hypothesized that sepsis would differentially alter central and peripheral vasomotor tone, decoupling the usual pressure wave propagation from central to peripheral sites.

Methods in pharmacology: measurement of cardiac output.

Many methods of cardiac output measurement have been developed, but the number of methods useful for human pharmacological studies is limited. The 'holy grail' for the measurement of cardiac output would be a method that is accurate, precise, operator independent, fast responding, non-invasive, continuous, easy to use, cheap and safe. This method does not exist today.

Partitioning the resistances along the vascular tree: effects of dobutamine and hypovolemia in piglets with an intact circulation.

Objective: We present a new physiological model that discriminated between changes in the systemic arterial and venous circulation. To test our model, we studied the effects of dobutamine and hypovolemia in intact pentabarbital-anesthetized piglets.

Methods: Aorta pressure (Pao), central venous pressure (Pcv), mean systemic filling pressure (Pmsf) and cardiac output (CO), were measured in 10 piglets, before, during and after dobutamine infusion (6 µg kg⁻¹ min⁻¹), as well as during hypovolemia (-10 mL kg⁻¹), and after fluid resuscitation to normovolemia.

Bedside assessment of mean systemic filling pressure.

Purpose Of Review: The physiology of the venous part of the human circulation seems to be a forgotten component of the circulation in critical care medicine. One of the main reasons, probably, is that measures of right atrial pressure (Pra) do not seem to be directly linked to blood flow. This perception is primarily due to an inability to measure the pressure gradient for venous return.

Assessing fluid responses after coronary surgery: role of mathematical coupling of global end-diastolic volume to cardiac output measured by transpulmonary thermodilution.

Background: Mathematical coupling may explain in part why cardiac filling volumes obtained by transpulmonary thermodilution may better predict and monitor responses of cardiac output to fluid loading than pressures obtained by pulmonary artery catheters (PACs).

Methods: Eleven consecutive patients with hypovolaemia after coronary surgery and a PAC, allowing central venous pressure (CVP) and continuous cardiac index (CCIp) measurements, received a femoral artery catheter for transpulmonary thermodilution measurements of global end-diastolic blood volume index (GEDVI) and cardiac index (CItp). One to five colloid fluid-loading steps of 250 ml were done in each patient (n = 48 total).

Less invasive indicators of changes in thermodilution cardiac output by ventilatory changes after cardiac surgery.

Background And Objective: We studied whether changes in less invasive, noncalibrated pulse-contour cardiac output (by modified ModelFlow, COmf) and derived stroke volume variations (SVV), as well as systolic and pulse pressure variations, predict changes in bolus thermodilution cardiac output (COtd), evoked by continuous and cyclic increases in intrathoracic pressure by increases in positive end-expiratory pressure (PEEP) and tidal volume (Vt), respectively.

Methods: Prospective study on 17 critically ill postcardiac surgery patients on full mechanical ventilatory support, in the intensive care unit.

Results: In contrast to systolic pressure variation and pulse pressure variation, SVV increased from (mean +/- SD) 6.

Transpulmonary versus continuous thermodilution cardiac output after valvular and coronary artery surgery.

Residual left-sided valvular insufficiencies after valvular surgery may confound transpulmonary thermodilution cardiac output (COtp). We compared the technique with the continuous right-sided thermodilution technique (CCO) after valvular surgery (n=8) and coronary artery surgery (n=8). Patients with pulmonary and femoral artery catheters in the intensive care unit (ICU) were included.

Assessment of venous return curve and mean systemic filling pressure in postoperative cardiac surgery patients.

Objective: To measure the relationship between blood flow and central venous pressure (Pcv) and to estimate mean systemic filling pressure (Pmsf), circulatory compliance, and stressed volume in patients in the intensive care unit.

Design: Intervention study.

Setting: Intensive care unit of a university hospital.

Relative value of pressures and volumes in assessing fluid responsiveness after valvular and coronary artery surgery.

Background And Aims: Cardiac function may differ after valvular (VS) and coronary artery (CAS) surgery and this may affect assessment of fluid responsiveness. The aim of the study was to compare VS and CAS in the value of cardiac filling pressures and volumes herein.

Methods: There were eight consecutive patients after VS and eight after CAS, with femoral and pulmonary artery catheters in place.

Cardiac output derived from left ventricular pressure during conductance catheter evaluations: an extended Modelflow method.

Objective: The Modelflow method computes cardiac output (CO) from arterial pressure (CO-MFao) by simulating a non-linear three-element Windkessel model of aortic input impedance. We present a novel technique to apply the Modelflow method to the left ventricular pressure (Plv) signal, to obtain an estimation of CO (CO-MFlv).

Methods: We extended the model by simulating the aortic valve as a resistance placed in series to the characteristic impedance.

Automatic intraaortic balloon pump timing using an intrabeat dicrotic notch prediction algorithm.

Purpose: The efficacy of intraaortic balloon counterpulsation (IABP) during arrhythmic episodes is questionable. A novel algorithm for intrabeat prediction of the dicrotic notch was used for real time IABP inflation timing control.

Description: A windkessel model algorithm was used to calculate real-time aortic flow from aortic pressure.

Beat-to-beat effects of intraaortic balloon pump timing on left ventricular performance in patients with low ejection fraction.

Background: Intraaortic balloon counterpulsation (IABP) timing errors during arrhythmia may result in afterload increases which may negatively influence left ventricular (LV) ejection and LV mechanical dyssynchrony. The aim of our study was to determine beat-to-beat effects of properly timed IABP, premature IAB inflation, and late IAB deflation on LV performance and LV mechanical dyssynchrony in heart failure patients undergoing cardiac surgery.

Methods: In 15 patients, LV pressure-volume relations and LV dyssynchrony were measured by conductance volume catheter.

Breath-to-breath analysis of abdominal and rib cage motion in surfactant-depleted piglets during high-frequency oscillatory ventilation.

Objective: To assess the value of monitoring abdominal and rib cage tidal displacement as an indicator of optimal mean airway pressure (Paw) during high-frequency oscillatory ventilation (HFOV).

Design And Setting: Prospective observational study in a university research laboratory.

Animals: Eight piglets weighing 12.

Regional lung volume during high-frequency oscillatory ventilation by electrical impedance tomography.

Objective: To investigate the value of electrical impedance tomography for the assessment of regional lung mechanics during high-frequency oscillatory ventilation (HFOV).

Design: Prospective, interventional animal study.

Setting: University research laboratory.