Changes In Left Ventricular Output Research Articles

Extended period of ventilation before delayed cord clamping augments left-to-right shunting and decreases systemic perfusion at birth in preterm lambs.

Previous studies have suggested that an extended period of ventilation before delayed cord clamping (DCC) augments birth-related rises in pulmonary arterial (PA) blood flow. However, it is unknown whether this greater rise in PA flow is accompanied by increases in left ventricular (LV) output and systemic arterial perfusion or whether it reflects enhanced left-to-right shunting across the ductus arteriosus and/or foramen ovale (FO), with decreased systemic arterial perfusion. Using an established preterm lamb birth transition model, this study compared the effect of a short (∼40s, n=11), moderate (∼2min, n=11) or extended (∼5min, n=12) period of initial mechanical lung ventilation before DCC on flow probe-derived perinatal changes in PA flow, LV output, total systemic arterial blood flow, ductal shunting and FO shunting. The LV output was relatively stable during initial ventilation but increased after DCC, with similar responses in all groups. Systemic arterial flow patterns displayed only minor differences during brief and moderate periods of initial ventilation and were similar after DCC. However, an increase in PA flow was augmented with an extended initial ventilation (P < 0.001), owing to an earlier onset of left-to-right ductal and FO shunting (P < 0.001), and was accompanied by a pronounced reduction in total systemic arterial flow (P=0.005) that persisted for 4min after DCC (P ≤ 0.039). These findings suggest that, owing to increased left-to-right shunting and a greater reduction in systemic arterial perfusion, an extended period of ventilation before DCC does not result in greater perinatal circulatory benefits than shorter periods of initial ventilation in the birth transition. KEY POINTS: Previous studies suggest that an extended period of initial ventilation before delayed cord clamping (DCC) augments birth-related rises in pulmonary arterial (PA) blood flow. It is unknown whether this greater rise in PA flow is accompanied by an increased left ventricular output and systemic arterial perfusion or whether it reflects enhanced left-to-right shunting across the ductus arteriosus and/or foramen ovale, with decreased systemic arterial perfusion. Anaesthetized preterm fetal lambs instrumented with central arterial flow probes underwent a brief (∼40s), moderate (∼2min) or extended (∼5min) period of ventilation before DCC. Perinatal changes in left ventricular output were similar in all groups, but extended initial ventilation augmented both perinatal increases in PA flow, owing to earlier onset and greater left-to-right ductal and foramen ovale shunting, and perinatal reductions in total systemic arterial perfusion. Extended ventilation before DCC does not confer a greater perinatal circulatory benefit than shorter periods of initial ventilation.

Lung ultrasound score parallels trends in systemic haemodynamics after PDA ligation: a case series.

A sustained fall in LUS after PDA ligation was identified, which most likely reflects reduction in pulmonary blood flow and interstitial edema. Changes in LUS paralleled changes in LVO, suggesting physiologic linkage. These data suggest that LU may be a useful tool to guide monitoring the biologic nature of pulmonary disease after PDA ligation. • Sustained exposure to a high-volume left-to-right patent ductus arteriosus (PDA) shunt is associated with interstitial pulmonary oedema. • In the most immature patients, cardiorespiratory deterioration, named post-ligation cardiac syndrome, presents 6-12 h post-operatively. • An early and sustained fall in lung ultrasound score (LUS) after PDA ligation most likely reflects reduction in pulmonary blood flow and interstitial oedema. LUS changes parallel changes in left ventricular output, suggesting linkage. • LU is a promising adjunctive tool in the post-operative management of PDA ligation.

A novel, hands-free ultrasound patch for continuous monitoring of quantitative Doppler in the carotid artery

Quantitative Doppler ultrasound of the carotid artery has been proposed as an instantaneous surrogate for monitoring rapid changes in left ventricular output. Tracking immediate changes in the arterial Doppler spectrogram has value in acute care settings such as the emergency department, operating room and critical care units. We report a novel, hands-free, continuous-wave Doppler ultrasound patch that adheres to the neck and tracks Doppler blood flow metrics in the common carotid artery using an automated algorithm. String and blood-mimicking test objects demonstrated that changes in velocity were accurately measured using both manually and automatically traced Doppler velocity waveforms. In a small usability study with 22 volunteer users (17 clinical, 5 lay), all users were able to locate the carotid Doppler signal on a volunteer subject, and, in a subsequent survey, agreed that the device was easy to use. To illustrate potential clinical applications of the device, the Doppler ultrasound patch was used on a healthy volunteer undergoing a passive leg raise (PLR) as well as on a congestive heart failure patient at resting baseline. The wearable carotid Doppler patch holds promise because of its ease-of-use, velocity measurement accuracy, and ability to continuously record Doppler spectrograms over many cardiac and respiratory cycles.

Indomethacin Impairs Coronary Perfusion in Infants with Hemodynamically Significant Ductus Arteriosus

Background: A haemodynamically significant ductus arteriosus (HSDA) is commonly associated with morbidity in preterm infants. Aim: To study the effect of the first dose of indomethacin on coronary blood flow in preterm neonates diagnosed with an HSDA. Method: A prospective observational echocardiographic study was performed on preterm infants. A single study dose of intravenous indomethacin (0.1 mg/kg) was administered over 1 h. Serial echocardiography was performed before and after indomethacin treatment to study the effect on coronary artery perfusion and cardiovascular performance. Results: Eighteen infants born at a median gestation of 25.8 (24.2, 28.1) weeks and a birth weight of 773 g (704, 1,002) were evaluated. The median age at indomethacin administration was 7.5 days (4, 17). There was no significant change in arterial pressure or ventilatory indices. Left anterior descending artery diastolic velocity and time integral declined from 0.3 ± 0.1 and 3.19 ± 1.2 m/s to 0.22 ± 0.08 and 2.01 ± 0.9 m/s, respectively, within 10 min of completion of infusion. These indices showed partial recovery when reassessed after 60 min. There were no changes in left ventricular output or transductal flow. Conclusions: Intravenous indomethacin was followed by a decline in coronary arterial diastolic blood flow.

Die akute Herzinsuffizienz: Diagnostik und Monitoring

The critically ill patient in acute heart failure continues to present an exceptional challenge concerning diagnostic procedures, monitoring and treatment. The European Society of Cardiology guidelines was the first to classify patients in acute heart failure into distinct clinical entities. Further management and choice of monitoring relies on this classification. Beside the obligatory monitoring (electrocardiography, respiratory rate, blood pressure, urine output, temperature) further components of a modular monitoring, as well as additional diagnostic procedures, must be implemented according to the acuteness and severity of the patient's condition. Measurement of cardiac output and arterial blood pressure are essential elements in an extended invasive monitoring. The pressure-based monitoring, which uses central venous pressure and pulmonary artery occlusion pressure as a surrogate for cardiac preload, should be replaced by a more volume-oriented monitoring. Moreover, new monitoring strategies should incorporate functional hemodynamic monitoring that evaluates the effects of treatment. Changes in volume and passive leg raising can be used to assess volume responsiveness. Changes in left ventricular output during spontaneous breathing or even positive pressure ventilation may be helpful in differentiating the extent of volume dependency. The greater the increase in tidal volume for the same lung compliance, the greater is the transient decrease in venous return and the subsequent decrease in left ventricular output. Variations in systolic pressure or pulse pressure are reliable measures of preload responsiveness. More clinical validation of these measures must be done before they can become standard measures of monitoring patients in acute heart failure.

178 Circulatory performance in neonates on high-frequency oscilliation

High-frequency oscillation (HFOV) is used to manage respiratory failure in critical ill newborns. To determine whether HFOV alters cardiac and cerebral performance we studied 18 infants (gestational age 34±3 wk, postnatal age 47±12 hours; birth weight 2350g±450) before and during HFOV (Stephan SHF 3000) for severe respiratory failure that has been unresponsive to IMV-ventilation. Dopplerechocardiography was used to determine changes in left ventricular output (LVO), cerebral and intestinal blood flow. Primary indications for HFOV included intractable airleaks (n=6), lung hypoplasia (n=1), meconium aspiration (n=1), pulmonary hypertension (n=2) and RDS (n=8). During HFOV, mean airway pressure was maintained at the same level as with IMV-ventilation Mean blood pressure (RR) increased from 45±5 to 50±6 mmHg (p<0.05). Flow resistance (RR:LVO) increased from 204±13 to 231±18 (p<0.05). Shortening fraction did not change (28% and 27%, respectively). Heart rate decreased from 138±15 to 127±13 1/min (p<0.05). LVO (220±54 and 216±48 ml/kg/min, respectively) remained unchanged. Mean blood flow velocity increased from 0.15±0.04 to 0.21±0.05 m/s in the A. carotis interna, from 0.16±0.05 to 0.22±0.04 m/s in the A. cerebri anterior and from 0.25±0.07 to 0.31±0.09 m/s in the coeliac trunc (p<0.05). PaCO2 decreased from 56±14 to 38±12 mmHg (p<0.05). Oxygenation index (OI=PaO2/FiO2) increased markedly. The results indicate that adequate ventilation and oxygenation can be maintained with HFOV in critically ill neonates without compromising their circulation.

Effect of lung volume and intrathoracic pressure on airway mucosal blood flow in man

We have recently described an inert soluble gas uptake technique (using dimethyl-ether, DME) for the non-invasive measurement of airway mucosal blood flow Q̇ aw, in humans. In the present study, we assessed the effects of lung volume and intrathoracic pressure on Q̇ aw, in healthy non-smokers (age range 19–52 years). Q̇ aw was calculated from the steady-uptake of DME from a 50 ml segment of the antomic dead space. The mean (± SD) Q̇ aw of three consecutive measurement at a lung volume of FRC + 300 ml was 8.3 ± 2.3, 8.6±2.6 and 8.3 ± 2.7 ml · min −1 ( n = 13; coefficient of variation 14 ± 7%). At zero airway pressure, there was an inverse relationship between apparent Q̇ aw on the one hand and lung volume and anatomic dead space (DS) on the other: mean Q̇ aw was 12.2 ± 5.3, 8.2 ± 2.5 and 5.3 ± 2.2. ml · min −1 at RV + 300 ml(DS = 131 ± 11 ml), FRC + 300 ml (DS = 153 ± 12 ml) and TCL (DS = 206 ± 22 ml) positions, respectively ( n = 11; P < 0.05 among all three). At a lung volume of FRC + 300 ml, an increase in intrathoracic pressure to +25 cmH 2O (modified Valsalva maneuver) decreased mean Q̇ aw to 3.3 ± 2.8 ml · min −1 while a decrease in intrathoracic pressure to −35 cmH 2O (modified Müller maneuver) increased mean Q̇ aw to 17.1 ± 7.4ml · min −1 from a control value of 7.2 ± 2.2 ml · min · min − ( n = 7; P < 0.05 among all three). These results indicate that lung volume has an effect on apparent Q̇ aw, presumably by influencing the depth to which the analyzed anatomical dead space segment extends into the bronchial tree. The results alos show that changes in intrathoracic pressure alter Q̇ aw possibly reflecting concomitant changes in left ventricular output and its distribution to intrathoracic and extrathoracic vascular beds.

Physiological mechanisms for calcium-induced changes in systemic arterial pressure in stable dialysis patients.

The mechanisms by which variations in blood ionized calcium (Ca2+) influence systemic arterial pressures independent of changes in extracellular fluid volume, pH, and electrolytes are unknown. To study this issue, we dialyzed eight stable hemodialysis patients on three separate occasions during 1 week with dialysates differing only in calcium concentration. Ultrafiltration was adjusted to achieve the patient's estimated dry weight. Postdialysis Ca2+ was measured, as were arterial blood gases, electrolytes, magnesium, blood urea nitrogen, creatinine, and hematocrit. Blood pressures and two-dimensional, targeted M-mode echocardiograms were recorded with the patient in the supine position after 15 minutes of rest. Postdialysis, three different levels of Ca2+ were achieved. Other measured biochemical variables and body weight did not differ among the three study periods. Changes in Ca2+ correlated directly with changes in systolic, diastolic, and mean blood pressures, left ventricular stroke volume, and cardiac output. In contrast, heart rate, left ventricular end-diastolic dimension, and total systemic vascular resistance were not altered significantly by changes in Ca2+. Thus, alterations in Ca2+ within the physiological range affect systemic blood pressure primarily through changes in left ventricular output rather than in peripheral vascular tone in stable dialysis patients.

Role of the cardiopulmonary blood volume in changes in left ventricular output during stimulation of somatic afferent nerve fibers

The effect of cytochalasin D (CD), an agent specifically destroying actin cytoskeleton, on DNA replication of cultured mouse embryonic fibroblasts (MEF) and BALB/3T3 strain cells was studied. Incubation of normal cells with CD resulted in progressive inhibition of DNA synthesis: in the first 16-20 h the percentage of cells pulse-labelled with 3H-thymidine was similar to that in control cultures, on day 8 the percentage of labelled cells was 7-8 times lower than in the control. The transfer of cells into fresh medium upon 8-day incubation in the presence of CD resulted in the recovery of DNA synthesis. Similar curves of DNA synthesis inhibition in the presence of CD and of DNA synthesis recovery in fresh medium were observed both in mononuclear and binuclear cells. Thus, CD-induced reorganization of actin cytoskeleton can have an abrupt but reversible disturbing effect on normal cell cycle.