The right ventricle: An emerging concern in the multiply injured patient

Cardiovascular changes during drainage of pericardial effusion by thoracoscopy

BACKGROUND

Cardiovascular changes during drainage of pericardial effusion are not well understood, and most studies are of systemic effects and not of right ventricular performance. Thoracoscopy is not widely used to drain pericardial effusions because of haemodynamic changes in relation to the use of single lung ventilation.

PATIENTS AND METHODS

We studied 16 patients undergoing partial pericardiectomy for pericardial effusion, using videothoracoscopy with a low-pressure pneumothorax (6 mm Hg). Cardiac output was measured by thermodilution with the patient anaesthetized in the supine position before the procedure; in the right lateral position after a low-pressure pneumothorax had been established; and after drainage of the pericardial effusion.

RESULTS

Before the procedure, cardiac output was low and central venous pressure and pulmonary artery occlusion pressure were increased. Systemic vascular resistance and arterial blood pressure were within normal limits. Cardiac filling pressure and pulmonary arterial pressure increased during the pneumothorax. After the drainage cardiac index increased and systemic and pulmonary vascular resistances were reduced.

CONCLUSIONS

Pericardial effusion reduces right ventricular distensibility, right and left systolic ventricular function, and cardiac output. Anaesthesia with mechanical ventilation and a low-pressure pneumothorax do not affect the circulation greatly. Drainage of the pericardial effusion allows cardiac distensibility to increase and cardiac performance changes to allow increased ejection.

Effectiveness of nitric oxide inhalation in septic ARDS

STUDY OBJECTIVE

To evaluate the percentage of nitric oxide (NO) responders in septic shock patients with ARDS. Additionally, to investigate long-term NO effects on cardiac performance and oxygen kinetic patterns in NO responders vs nonresponders.

DESIGN

Prospective cohort study.

SETTING

ICU of a university hospital.

PATIENTS

Twenty-five consecutive patients with a diagnosis of septic shock and established ARDS requiring inotropic and vasopressor support.

INTERVENTIONS

After diagnosis of ARDS, NO was administered at 18 or 36 ppm. Patients demonstrating a NO-induced rise of arterial oxygen tension of 20% or more and/or a fall in mean pulmonary artery pressure of 15% or more were grouped as NO responders; others were grouped as nonresponders.

MEASUREMENTS AND RESULTS

Ten patients (40%) were NO responders, while 15 patients (60%) were nonresponders. Mortality was 40% in NO responders and 67% in nonresponders (NS). NO responders developed a significantly lower mean pulmonary artery pressure (28 +/- 6 vs 33 +/- 6 mm Hg; p < 0.05), lower pulmonary vascular resistance (PVR: 258 +/- 73 vs 377 +/- 163 dyne.s.cm-5.m-2; p < 0.05), and higher PaO2/FIO2 ratio (192 +/- 85 vs 144 +/- 74 mm Hg; p < 0.05) within the study period. In responders, NO-induced afterload reduction resulted in increased right ventricular ejection fraction (RVEF: 40 +/- 7 vs 35 +/- 9%; p < 0.05), significantly higher cardiac index (CI: 4.5 +/- 1.1 vs 4.0 +/- 1.2 L.min-1.m-2; p < 0.05) and oxygen delivery (DO2: 681 +/- 141 vs 599 +/- 160 mL.min-1.m-2; p < 0.05) compared with nonresponders. In NO nonresponders, RVEF was correlated with PVR, CI, DO2, mixed venous oxygen saturation (SvO2), and oxygen extraction ratio (O2ER) (r = +/- 0.60 to +/- 0.69; p < 0.05). No significant correlation between RVEF and any of these parameters was observed in responders. SvO2 (75 +/- 7 vs 69 +/- 8%; p < 0.05) and O2ER (0.24 +/- 0.06 vs 0.27 +/- 0.06; p < 0.05) were significantly different between responders and nonresponders, while no difference in oxygen consumption was observed (161 +/- 41 vs 153 +/- 43 mL.min.m-2).

CONCLUSIONS

Inhaled NO is effective in only a subgroup of septic ARDS patients, with a higher, but insignificantly different percentage of survivors in the responder group. NO responders were characterized by increased RVEF accompanied by higher CI, DO2, and lower O2ER. In nonresponders, RVEF remained depressed, with a close correlation between RVEF and CO as well as DO2 and O2ER. Thus, nonresponders seem to suffer from impaired cardiac reserves and correspondingly lower oxygen transport variables.

Effects of inhaled nitric oxide on right ventricular function in severe acute respiratory distress syndrome

OBJECTIVE

To compare the effects of inhaled nitric oxide (NO) and an infusion of prostacyclin (PGI2) on right ventricular function in patients with severe acute respiratory distress syndrome (ARDS).

DESIGN

Randomized prospective short-term study.

SETTING

Post-surgical ICU in an university hospital.

PATIENTS

10 patients with severe ARDS referred to our hospital for intensive care.

INTERVENTIONS

In random sequence the patients inhaled NO at a concentration of 18 parts per million (ppm) followed by 36 ppm, and received an intravenous infusion of PGI2 (4 ng.kg-1.min-1).

MEASUREMENTS AND RESULTS

Inhalation of 18 ppm NO reduced the mean (+/- SE) pulmonary artery pressure (PAP) from 33 +/- 2 to 28 +/- 1 mmHg (p = 0.008), increased right ventricular ejection fraction (RVEF), as assessed by thermodilution technique, from 28 +/- 2 to 32 +/- 2% (p = 0.005), decreased right ventricular end-diastolic volume index from 114 +/- 6 to 103 +/- 8 ml.m-2 (p = 0.005) and right ventricular end-systolic volume index from 82 +/- 4 to 70 +/- 5 ml.m-2 (p = 0.009). Mean arterial pressure (MAP) and cardiac index (CI) did not change significantly. The effects of 36 ppm NO were not different from the effects of 18 ppm NO. Infusion of PGI2 reduced PAP from 34 +/- 2 to 30 +/- 2 mmHg (p = 0.02), increased RVEF from 29 +/- 2 to 32 +/- 2% (p = 0.02). Right ventricular end-diastolic and end-systolic volume indices did not change significantly. MAP decreased from 80 +/- 4 to 70 +/- 5 mmHg (p = 0.03), and CI increased from 4.0 +/- 0.5 to 4.5 +/- 0.5 l.min-1.m-2 (p = 0.02).

CONCLUSIONS

Using a new approach to selective pulmonary vasodilation by inhalation of NO, we demonstrate in this group of ARDS patients that an increase in RVEF is not necessarily associated with a rise in CI. The increase in CI during PGI2 infusion is probably related to the systemic effect of this substance.

Prostacyclin and right ventricular function in patients with pulmonary hypertension associated with ARDS

Eight patients who developed pulmonary artery hypertension during the adult respiratory distress syndrome (ARDS) were treated with an infusion of prostacyclin (PGI2, 12.5-35.0 ng.kg-1.min-1) for 45 min. We examined whether reducing the right ventricular (RV) outflow pressures by PGI2 infusion would increase the right ventricular ejection fraction (RVEF) measured by thermodilution. PGI2 reduced the pulmonary artery pressure (PAP) from 35.6 to 29.1 mmHg (p less than 0.01). The cardiac index (CI) increased from 4.2 to 5.81.min-1.m-2 (p less than 0.01) partly due to an increased stroke volume. The decreased PAP together with the increased CI resulted in a fall of the calculated pulmonary vascular resistance index (PVRI, from 5.1 to 2.5 mmHg.min.m2.1-1, p less than 0.01). In the patients with subnormal baseline RVEF the increased stroke volume was associated with an increased RVEF (from 47.6% to 51.8%, p less than 0.05) suggesting improved RV function. This result was underscored by a significant relationship between the changes in PVRI and RVEF (r = 0.789, delta % RVEF = 2.11.delta PVRI-1.45). Despite an increased venous admixture from 27.8% to 36.9% (p less than 0.05) the arterial PO2 remained constant resulting in an increased oxygen delivery from 657 to 894 ml.min-1.m-2 (p less than 0.01). We conclude that short term infusions of PGI2 increased CI concomitant to improved RV function parameters when baseline RVEF was depressed. Since improved oxygen availability should be a major goal in the management of patients with ARDS PGI2 may be useful to lower pulmonary artery pressure in ARDS.