Lung replantation--respiratory reflexes, vagal integrity, and lung function in chronic dogs

Motor and sensory re-innervation of the lung and heart after re-anastomosis of the cervical vagus nerve in rats

There is no study in the literature dealing with re-innervation of the cardiopulmonary vagus nerve after its transection followed by re-anastomosis. In the present study, we explored the bronchomotor, heart rate and respiratory responses in rats at 2, 3 and 6 months after re-anastomosis of one cervical vagus trunk. The conduction velocity of A, B and C waves was calculated in the compound vagal action potential. We searched for afferent vagal activities in phase with pulmonary inflation to assess the persistence of pulmonary stretch receptor (PSR) discharge in re-innervated lungs. In each animal, data from the stimulation or recording of one re-anastomosed vagus nerve were compared with those obtained in the contra-lateral intact one. Two and three months after surgery, the conduction velocities of A and B waves decreased, but recovery of conduction velocity was complete at 6 months. By contrast, the conduction velocity of the C wave did not change until 6 months, when it was doubled. The PSR activity was present in 50% of re-anastomosed vagus nerves at 2 and 3 months and in 75% at 6 months. Respiratory inhibition evoked by vagal stimulation was significantly weaker from the re-anastomosed than intact nerve at 2 but not 3 months. Vagal stimulation did not elicit cardiac slowing or bronchoconstriction 6 months after re-anastomosis. Our study demonstrates the capacity of pulmonary vagal sensory neurones to regenerate after axotomy followed by re-anastomosis, and the failure of the vagal efferents to re-innervate both the lungs and heart.

Bronchial responsiveness after human heart-lung transplantation

We evaluated bronchial responsiveness to inhaled albuterol (salbutamol), ipratropium bromide, methacholine, and propranolol in eight heart-lung transplant (HLT) recipients 2.3 +/- 1.5 months (mean +/- SD) (range, 1 to 4.5 months) after HLT. All patients had a restrictive ventilatory defect but none had airflow limitation (FEV1/FVC = 0.93 +/- 0.05) (range, 0.86 to 0.97). Specific airway conductance (sGaw) improved significantly with both albuterol (p less than 0.01) and ipratropium bromide (p less than 0.01) but FEV1 did not. Only one HLT patient had bronchoconstriction with propranolol, whereas all but one were hyperresponsive to methacholine. Prior inhalation of ipratropium bromide blocked the response to methacholine (p less than 0.005). Serial methacholine provocation tests performed in seven long-term survivors of HLT 24.6 +/- 16.0 months (range, 12 to 51 months) after HLT revealed no time-dependent evolution of bronchial hyperresponsiveness to methacholine. Limited maximal airway narrowing to methacholine was seen in five HLT recipients who showed a 29 +/- 4 percent (range, 23 to 35 percent) fall in FEV1 compared with two patients who did not achieve a plateau with a 47 percent and 63 percent fall in FEV1, respectively. These results further our understanding of bronchial responsiveness in the denervated transplanted lung. The findings of stable hyperresponsiveness to methacholine over a prolonged time interval, limited maximal airway narrowing to methacholine, and blockade of methacholine hyperresponsiveness by ipratropium bromide support the concept of denervation hypersensitivity of muscarinic receptors.

Single- and double-lung transplantation. Problems and possible solutions

There is a resurgence of interest in single- and double-lung transplantation for end-stage disease. An experience with six double-lung and three single-lung transplants is reported. The lungs were procured from a distance of up to 600 miles and the heart was shared with another team for transplantation in seven of nine instances. The operative mortality rate was 33%. Early transplant infections of donor origin were lethal. Late transplant pneumonitis was well tolerated and recovery was the rule. Three of nine cases had significant tracheal suture line stenosis and were managed conservatively. A technique of bronchial artery implantation using a conduit tailored from donor aorta is described. Transplant rejection was easily diagnosed and treated. Other notable complications included occasional massive pleural fluid loss, temporary space problem, and a delay in the 'resetting' of chemoreceptors resulting in moderate post-transplant hypercarbia accompanied by episodes in which the patient felt hypoxemic despite the maintenance of excellent levels of blood gases. A comprehensive rehabilitation program begun before operation is essential for success.