First annual Herbert S. Shubin Memorial Lecture. Acute circulatory failure (shock) associated with cardiogenic pulmonary edema

Cardiac output measurement by pulse dye densitometry using three wavelengths

OBJECTIVES

Pulse dye densitometry (PDD), based on the principles of pulse oximetry and dye-dilution technique, is a less invasive method of measuring cardiac output (CO). We have developed prototype equipment to measure CO in pediatric patients using this technique. The purpose of our study was to evaluate the accuracy of this new PDD system using three wavelengths for pediatric application by comparing measurement with an ultrasound flowmeter.

DESIGN

Laboratory investigation.

SETTING

Hospital physiology research laboratory.

SUBJECTS

A total of 15 young piglets weighing approximately 10 kg each.

INTERVENTIONS

Measurement of CO by PDD was performed using general anesthesia. Indocyanine green, 0.2 mg/kg, was administered intravenously, and CO was calculated from the dye dilution curve obtained by the PDD system. The ultrasound flowmeter probe was placed on the ascending aorta in the animal, and CO was simultaneously calculated.

MEASUREMENTS AND MAIN RESULTS

The two CO values, simultaneously obtained by the ultrasound flowmeter and PDD, were compared during various hemodynamic states. The bias between the CO measured by the ultrasound flowmeter and the CO measured by the PDD system using the reflection-type probe at the central site was 33.8 mL/min and the precision was 293.4 mL/min, indicating that CO measured by PDD had a good correlation with measurements obtained with the ultrasonic method.

CONCLUSION

We measured CO in young piglets at an acceptable level of bias and precision using a prototype PDD device. CO measurement by this new PDD system using three wavelengths can be useful and beneficial for critically ill infants and children. It is simple to perform, requiring an injection of dye into a peripheral intravenous catheter, and it will provide a less invasive bedside measurement of CO.

Tracheal gas insufflation combined with high-frequency oscillatory ventilation

OBJECTIVES

To determine the efficacy of tracheal insufflation delivered by two different catheter designs on CO2 elimination when used in conjunction with high-frequency oscillatory ventilation.

DESIGN

A nonrandomized before and after trial. Each animal served as his own control.

SUBJECTS

Ten mongrel dogs weighing 20.9 +/- 1.9 kg. Four animals were assigned to a normal lung group and six animals underwent lung injury by large volume saline lavage.

INTERVENTION

Permissive hypercapnia was allowed to occur by selecting oscillator settings that would lead to alveolar hypoventilation. Proximal mean airway pressure was kept constant. Tracheal gas was insufflated at 1 cm above the carina for 30 min periods at gas flows of 5 to 15 L/min.

MEASUREMENTS AND MAIN RESULTS

Carinal pressure, hemodynamic parameters (cardiac output, mean arterial pressure, pulmonary artery occlusion pressure), and gas exchange parameters (PaCO2, PaO2, PaO2/FIO2, shunt fraction, D O2) were measured. For the normal dogs, at catheter flow of 15 L/min; the forward thrust catheter increased carinal pressure and Pao2/FIO2 BY 30% (p<.003) and 105% (p<.005), respectively. The forward thrust catheter reduced Paco2 by 40% (p<.04). The reverse thrust catheter increased PaO2/FIO2 by 102% (p<.001) and decreased pressure and PaCO2 by 44% (p<.001) and 34% (p<.003), respectively. For the injured dogs, at catheter flow rate of 15 L/min, the forward thrust catheter increased carinal pressure, PaO2, and PaO2/FIO2 by 6% (p<.001), 23% (p<.001), and 24% (p<.02), respectively. The forward thrust catheter reduced PaCO2 by 29% (p<.002). The reverse thrust catheter increased PaO2 and PaO2/FIO2 both by 11% (p<.02) and reduced carinal pressure and PaCO2 by 23% (p<.001) and 18% (p<.002), respectively.

CONCLUSIONS

Tracheal gas insufflation is capable of improving oxygenation and ventilation in acute lung injury when combined with high-frequency oscillatory ventilation. The addition of this second gas flow at the level of the carina raises or lowers distal airway pressure, the magnitude of which is dependent on the direction and rate of gas flow. The beneficial effects of tracheal gas insufflation may be tempered by the long-term effects of altering distal airway pressure; lowering distal airway pressure may lead to atelectasis, whereas raising distal airway pressure may lead to an auto-positive end-expiratory pressure (auto-PEEP) effect.

Predictors of between-method differences in cardiac output measurement using thoracic electrical bioimpedance and thermodilution

OBJECTIVES

To evaluate the usefulness of transthoracic electrical bioimpedance in trending changes in cardiac output after cardiac surgery, and to identify predictors of differences between cardiac output measured by thermodilution and transthoracic electrical bioimpedance methods.

DESIGN

Prospective repeated-measures study.

SETTING

University-affiliated tertiary care center.

PATIENTS

Thirty-four adult patients undergoing elective cardiac surgery with routine pulmonary artery catheter placement.

INTERVENTIONS

Simultaneous paired cardiac output measurements by transthoracic electrical bioimpedance and thermodilution were made at four time points: within 2 hrs of intensive care unit (ICU) admission; when the patient reached a normothermic temperature; after extubation; and 24 hrs after ICU admission.

MEASUREMENTS AND MAIN RESULTS

Mean measurements by each method over time did not differ, except at ICU admission, when compared by repeated-measures analysis of variance. For each time point, bias and precision between methods were calculated. Bias calculations ranged from 0.02 to 0.21 L/min/m2. Precision calculations ranged from 1.06 to 1.52 L/min/m2. Predictors of between-method differences identified by a multiple regression model of hemodynamic variables were: increased systemic vascular resistance index, decreased mean arterial pressure (MAP), and the presence of atrial or ventricular pacing.

CONCLUSIONS

While mean postoperative cardiac output measurements did not differ by method over time, agreement between transthoracic electrical bioimpedance and thermodilution methods was poor in the immediate postoperative period, with precision calculations indicative of clinically significant differences. Increased systemic vascular resistance index and decreased MAP were predictive of larger between-method differences.

[Low-capillary-pressure pulmonary edema occurring in the acute phase of myocardial infarction]

A 44-year old man presented a postanoxic coma and acute pulmonary oedema after cardiopulmonary resuscitation in the acute phase of myocardial infarction. Early haemodynamic measurements revealed low right and left ventricular filling pressures and a low cardiac output. Haemodynamic and clinical improvement was obtained after volume expansion. The cause of low-pressure pulmonary oedema occasionally seen in patients with acute myocardial infarction is sometimes unclear. In the present case, a neurogenic mechanism may be involved. The early diagnosis of this oedema has important therapeutic implications.

Effect of afterload reduction on plasma volume during acute heart failure

Previous investigations in our unit indicated that acute cardiogenic pulmonary edema is associated not only with an increase in left ventricular end-diastolic pressure and pulmonary arterial wedge pressure but also with a relative increase in colloid osmotic (oncotic) pressure and peripheral hemoglobin concentration. This combination of changes suggested that acute congestive heart failure with pulmonary edema, unlike chronic congestive heart failure, is associated with a contraction of intravascular blood volume. In this study, plasma volume changes were measured before and during the treatment of acute cardiogenic pulmonary edema in 14 patients with arteriosclerotic heart disease. The plasma volume measurement in all 14 patients before the initiation of treatment was either normal or decreased. After treatment with the alpha adrenergic blocking agent phentolamine, the plasma volume increased rather than decreased when measured 4 and 12 hours after the initiation of treatment. During this time colloid osmotic pressure and peripheral hemoglobin concentration progressively decreased. These findings suggest that acute cardiogenic pulmonary edema is associated with the extravasation of large quantities of plasma water from the intravascular compartment into the interstitial compartment and contraction of the intravascular plasma volume. The treatment of acute cardiogenic pulmonary edema is associated with the return of hypo-oncotic fluid from the interstitial compartment back into the intravascular compartment with expansion of plasma volume and reduction of colloid osmotic pressure and hemoglobin concentration.