Right ventricular afterload mismatch during acute pulmonary hypertension and its treatment with dobutamine: A pressure segment length analysis in a canine model

Aspects of Anesthesia for Lung Transplantation

Anesthesia for lung transplantation is both a demand ing and rewarding experience. Success requires team- work, experience, knowledge of cardiorespiratory patho physiology and its anesthetic implications, appropriate use of noninvasive and invasive monitoring, and the ability to respond quickly and effectively to life- threatening perioperative events. Specific issues in clude management of a patient with end-stage lung and heart disease, lung isolation and one-lung ventilation, perioperative respiratory failure, pulmonary hyperten sion, and acute right ventricular failure. Recent ad vances include greater understanding of dynamic hyper inflation ("gas-trapping") during mechanical ventilation, perioperative use of inhaled nitric oxide and treatment of acute right ventricular failure. Successful anesthetic management leads to greater hemodynamic stability, improvement in gas exchange and a reduction in need for cardiopulmonary bypass, all of which should lead to improved patient outcome.

Hemodynamic effects of fluid loading in acute massive pulmonary embolism

OBJECTIVE

To assess the hemodynamic effects of fluid loading in patients with acute circulatory failure caused by acute massive pulmonary embolism (AMPE).

DESIGN

Prospective study.

SETTING

Respiratory critical care unit of a university hospital.

PATIENTS

Thirteen patients free of previous cardiopulmonary disease with angiographically proven AMPE (Miller index = 24 +/- 1), with acute circulatory failure defined by a cardiac index (CI) lower than 2.5 L/min/m2.

INTERVENTION

Infusion of 500 mL of dextran 40 over 20 mins.

MEASUREMENTS AND MAIN RESULTS

Fluid loading induced a substantial increase in right atrial pressure from 9 +/- 1 mm Hg to 17 +/- 1 mm Hg and in right ventricular end-diastolic volume index from 123 +/- 14 mL/m2 to 150 +/- 11 mL/m2 (p < .05 for both comparisons). The increase in right ventricular preload was associated with an increase in Cl from 1.6 +/- 0.1 to 2.0 +/- 0.1 L/min/m2 (p < .05), whereas right ventricular ejection fraction (15 +/- 3% at baseline vs. 16 +/- 3% after fluid loading) and total pulmonary vascular resistance index (1689 +/- 187 dyne x sec/cm5 x m2 at baseline vs. 1492 +/- 166 dyne x sec/ cm5 x m2 after fluid loading) remained unchanged. The increase in Cl induced by fluid loading was inversely correlated to baseline right ventricular end-diastolic volume index (r = -.89 ; p< .05).

CONCLUSIONS

These results suggest that fluid loading can improve hemodynamic status in patients with acute circulatory failure caused by AMPE.

Anesthesia for bilateral lung transplantation without cardiopulmonary bypass: initial experience and review of intraoperative problems

Bilateral lung transplantation (BLT) is a recently described procedure based on two sequential single-lung transplantations (SLT), which are performed by a transverse sternobithoracotomy. It does not require either cardiac arrest or routine use of cardiopulmonary bypass (CPB). The intraoperative management of 10 patients suffering from end-stage pulmonary disease is reported. Implantation of the first graft is quite similar to a SLT. Problems encountered during this procedure (ie, hypoxemia, hypercapnia, or low cardiac output) were due to restricted pulmonary and cardiac reserve. Preoperative and intraoperative assessment of the recipient's respiratory and cardiac status was, therefore, of prime importance. Mild preoperative pulmonary hypertension, well-preserved right ventricular function, and removal of the less well-perfused lung limited these difficulties; no patient required partial CPB at this stage. During the second lung implantation, gas exchange was provided by the first grafted lung. Measurements of pulmonary vascular resistance (PVR), venous admixture (Qva/Qt), and dead space (VD/VT) assessed with the arterial-to-end-tidal CO2 difference were used to confirm the adequacy of perfusion and V/Q matching. In one patient, partial CPB was instituted because of surgical difficulty related to inadequate size matching of the lungs. In the other patients, first graft function was satisfactory and the second graft was implanted without CPB. With chest closure, PVR returned to nearly normal values (range, 57-293, mean 167 dynes.s.cm-5) and Qva/Qt increased (range, 3 to 36, mean 20%). This limited series demonstrates that CPB is optional during this procedure. Good selection of recipients and donors, good lung preservation methods, and a short duration of cold ischemia are essential to success.

Acute right heart failure: pathophysiology, recognition, and pharmacological management

Acute RV failure is an increasingly more common clinical entity and problem. A good understanding of the pathophysiology is required to develop a treatment strategy. Principles of treatment outlined include optimizing RV preload, cautiously reducing RV afterload, and enhancing RV contractility.