Case 1--1997. Diagnosis and management of dynamic hyperinflation during lung transplantation

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.

Pathophysiology and management of one-lung ventilation

The ability to manage OLV effectively in patients with significant pulmonary disease is increasing. Knowledge of pulmonary ventilation and perfusion physiology, improvements in the ability to prevent and treat hypoxia, and a thorough grasp of traditional and novel ventilatory techniques may promote improved perioperative outcomes.

Lessons from lung transplantation for everyday thoracic anesthesia

Patients with end-stage lung disease are at significant risk of hypoxia and dynamic hyperinflation during mechanical ventilation, particularly during one-lung ventilation. This article describes aspects of care such as patients, including acceptance of permissive hypercapnia, adjustment of ventilator settings, and methods to optimize recovery from anesthesia.

Continuous arterial blood gas monitoring during bilateral sequential lung transplantation

OBJECTIVE

To determine the accuracy and clinical utility of a continuous arterial blood gas (ABG) monitor during lung transplantation.

DESIGN

Prospective, observational cohort study.

SETTING

University hospital.

PARTICIPANTS

Eleven patients undergoing bilateral sequential lung transplantation (BSLTx).

INTERVENTIONS

Repeated ABG sampling.

MEASUREMENTS AND MAIN RESULTS

Agreement was measured by the bias (limits of agreement): pH, 0.006 (-0.10 to 0.10); PaO2, -22 mmHg (-130 to 86 mmHg); and PaCO2, -1.6 mmHg (-13.4 to 10.2 mmHg). Sensitivity and specificity of the Paratrend 7 (Biomedical Sensors, Ltd, Malvern, PA) PaO2 measurements (to detect PaO2 < 100 mmHg) were 84.6% and 97.6%, respectively.

CONCLUSION

Continuous ABG monitoring with the Paratrend 7 shows sufficiently good agreement with laboratory blood gas analysis during BSLTx and thus is a convenient alternative to intermittent laboratory blood gas measurement. Because of the potential for significant (and sometimes rapid) acid-base disturbances, continuous ABG monitoring may have a role during most lung transplantation procedures.

Pulmonary air trapping during two-lung and one-lung ventilation

OBJECTIVE

Evaluation of the magnitude of pulmonary air trapping during routine thoracic surgery and single-lung transplantation.

DESIGN

Prospective study on consecutive patients.

SETTING

Single institution, university hospital.

PARTICIPANTS

Sixteen patients with no or moderate obstructive lung disease undergoing routine thoracic surgery (group 1), six patients with severe emphysema (group 2), and six patients with severe fibrosis (group 3) undergoing single-lung transplantation.

INTERVENTIONS

Occlusion maneuver timed at the end of expiration to measure auto-positive end-expiratory pressure (auto-PEEP) and trapped volume (delta FRC). The maneuver was performed during two-lung ventilation in supine (2LV supine) and lateral decubitus (2LV lateral) positions and during one-lung ventilation (OLV) in lateral decubitus position. At the same time, airway pressures and PaO2 measurements were performed.

MEASUREMENTS AND MAIN RESULTS

In group 1, consistent values of auto-PEEP and delta FRC occurred only during OLV: 4.8 +/- 2.5 cm H2O and 109 +/- 61 mL (mean +/- standard deviation). In group 2, auto-PEEP and delta FRC values were 11.7 +/- 6.9 cm H2O and 355 +/- 125 mL during 2LV supine, 8.8 +/- 5.7 cm H2O and 320 +/- 122 mL during 2LV lateral, and 15.9 +/- 3.9 cm H2O and 284 +/- 45 mL during OLV. In group 3, pulmonary air trapping was low. For the three groups together, auto-PEEP and delta FRC (p < 0.0001) related inversely to the ratio of forced expired volume in 1 second (FEV1) to forced vital capacity (FVC) expressed in percent (FEV1/FVC%) during OLV. In contrast, there was no correlation between PaO2 and auto-PEEP or delta FRC.

CONCLUSION

Pulmonary air trapping must be suspected in patients with no or moderate obstructive lung disease during OLV and in those with severe obstructive disease as soon as 2LV is initiated.

Dynamic hyperinflation: comparison of jet ventilation versus conventional ventilation in patients with severe end-stage obstructive lung disease

Positive pressure ventilation in patients with obstructive lung disease may result in over-inflation of the relatively compliant lungs, resulting in dynamic hyperinflation (DHI). Using a crossover trial design, we compared high-frequency jet ventilation (HFJV) versus "optimal" intermittent positive pressure ventilation (IPPV) in ten patients undergoing lung transplantation for severe, end-stage obstructive lung disease. We measured haemodynamics and the degree of DHI after both modes of ventilation. There were no significant differences between IPPV and HFJV, with respect to efficiency of ventilation (PaCO2), haemodynamic effects (stroke volume, blood pressure and cardiac output), or lung hyperinflation (trapped gas volume). This study suggests that HFJV, when compared with optimal IPPV, is no better at minimizing DHI in patients with severe, end-stage obstructive lung disease.