Anaesthetic management of bilateral alveolar proteinosis for bronchopulmonary lavage.

R Dixit, LS Chaudhari, AA Mahashur 
 Department of Anesthesiology and Chest Medicine, Seth G.S. Medical College, Parel, Mumbai.

Correspondence Address:
R Dixit
Department of Anesthesiology and Chest Medicine, Seth G.S. Medical College, Parel, Mumbai.

Full Text

::   Introduction

Pulmonary alveolar proteinosis is a condition in which the alveoli are filled with a granular flocculent proteinaceous material due to abnormal accumulation of normal surfactant. This is usually treated by bronchopulmonary lavage, the anaesthetic management of which is described.

::   Case report

A 14 years old boy weighing 30 kgs had dyspnoea on exertion for last four years, progressively increased to grade III and frequent attacks of fever and cough with minimal thin mucoid secretion. There was no history of any other symptom or allergy or addiction.

His clinical findings were: pulse 100/min, blood pressure 110/70 mm of Hg, respiratory rate 22/min, bilaterally decreased breath sounds and rales on right 'middle zone. Chest Xray showed bilateral alveolar shadows with confluence at middle zones and lower zones. Arterial blood gas analysis showed basal' hypoxemia (PaO2 60 mm Hg) on air with non-significant fall in PaO2 (58 mm Hg) following exercise with inadequate rise in PaO2 (62 mm Hg) after 100% oxygen. A diagnosis of interstitial lung disease could be made from this report. On pulmonary function test, lung mechanics favour the diagnosis of restrictive lung disease. However, the diagnosis of bilateral pulmonary alveolar proteinosis was confirmed only after bronchoscopic aspiration lavage. Ventilation perfusion scan showed equal involvement of both the lungs. It was therefore decided to do left bronchopulmonary lavage (BPL) followed by right bronchopulmonary lavage after few months.

Pre-procedure preparation of patient was done with bronchial hygiene therapy. No premedication was given. Patient was made to lie on warm heating mattress to avoid hypothermia. Preoxygenation was done for 5 minutes to cause denitrogenation of lungs. 15mg pentazocine and 2.5 mg diazepam were given through 18G intravenous cannula, as a part of, balanced anaesthesia technique. Induction was done with a sleep dose of 2.5% thiopentone sodium and 2mg/kg suxamethonium taking standard precautions. Trachea was intubated with 26 French Gauge (Broncho Cath) left sided plastic double hymen tube[1],[5]. Bilateral equal air entry was confirmed after inflating the tracheal cuff. The bronchial cuff was inflated after clamping the tracheal side of tube, till air entry disappeared on tracheal side. The ‘air bubble detection method’[1],[2] with ‘catheter under water assembly' for adequacy of cuff seal was used to confirm functional separation of the two lungs.

Anaesthesia was maintained with 50% nitrous oxide in oxygen, 0.51% isoflurane and atracurium (a muscle relaxant). The parameters monitored were pulse, blood pressure, temperature, electrocardiogram, central venous pressure, pulse oximetry and capnography. Radial artery cannulation was done for continuous measurement of blood pressure and intermittent blood gas analysis. Jugular vein was cannulated for central venous pressure monitoring. The procedure was done in lateral decubitus position with lavage side dependent to avoid hazardous complication of any spillage of lavage fluid to ventilated side. It was decided to promptly change the position to supine only if pulse oximetry reading fell below 90%. One lung ventilation was done during BPL with a tidal volume of 10ml/kg and 14 16/min4 of respiratory rate.

Lavage was done with warm isotonic saline containing 9.5 ml sodium bicarbonate and 1 unit of heparin in 1 litre of fluid. A tidal lavage of 500 ml was needed by patient and a total lavage volume of 9.5 litres and 9 litres respectively was needed for left and right sided lavage. Each time it took around 6 hours to finish the procedure.

Continuous monitoring to detect the loss of lung isolation was done as follows[1],[2],[3].

1. The appearance of bubbles in the lavage fluid draining from the lavaged side.

2. Increased resistance to ventilation and appearance of rales and rhonchi on the ventilated side.

3. Imbalance between administered lavage volume and drained lavage volume.

4. A fall in arterial oxygen saturation and end tidal carbon dioxide due to spillage leading to inadequate ventilation.

At no time during the procedure, the oxygen saturation fell below 92% during left lung lavage and 90% during right lung lavage. Highest end tidal CO2 reading was 54.5 mm of Hg during left lung lavage and 47.5 mm of Hg during right lung lavage.

Once the returning fluid was clear, the procedure was terminated. Endotracheal tube was changed to a standard 8.5 mm Rusch cuffed tube. Two lung ventilation, chest wall percussion with different positions of patient, suctioning and arterial blood gases were done. Once the chest was clear, arterial blood gas was satisfactory, temperature was normal and other clinical parameters were stable the patient was reversed with 0.6 mg atropine and 1 mg neostigmine intravenously taking standard precautions. After extubation, the patient was observed in operation theatre for some time and then shifted to intensive care unit on oxygen mask.

::   Discussion

Bronchopulmonary lavage (BPL) is usually indicated in alveolar proteinosis patients with an arterial oxygen tension less than 60 mm Hg at rest or hypoxemic limitation of exercise[3]. The clinical course and prognosis with or without BAL is variable. Some patients require lavage every few months while others remain in remission for several years.

All the measures during the procedure are directed to enhance patient safety by avoiding hypoxemia, spillage of lavage fluid and hypothermia. A constant team of' senior anaesthesiologists and chest physicians should be engaged to manage the patient from the day of admission. A thorough detailed preoperative visit by the anaesthesiologist helps to build up patient’s confidence. The patient should also be informed of the need for endotracheal tube and artificial ventilation in the immediate postoperative period. The lavage is first performed on the most affected side allowing the better lung to provide gas exchange. However as in our case, if both lungs are equally involved, the left lung is lavaged first leaving relatively larger right lung to support gas exchange[3].

Premedication with anticholinergic drugs is avoided to prevent undue drying of secretions. We did not sedate our patient preoperatively as he was hypoxaemic even at rest. However, a light premedication in the form of oral diazepam followed by oxygen mask may be given[1],[3].

During the procedure, all the measures should be taken to avoid hypothermia since the procedure takes several hours to complete and lavage fluid temperature may not be always precisely controlled leading to tremendous cooling of the patient[1],[3]. Patients should be monitored thoroughly. Additionally, pulmonary artery catheterisation can be used in patients with compromised cardiovascular function[1],[3].

Preoxygenation for 5 minutes prior to anaesthesia is not only done as a routine precaution especially in critically ill patients but also to facilitate lavage by causing denitrogenenation of lungs. If nitrogen is present in the alveoli, it interferes with the lavage by limiting the contact of lavage fluid with the alveolar wall[1],[3].

Adequate oxygenation can be maintained throughout the procedure by using high inspired oxygen concentration (upto 100%).

Isoflurane is preferred to halothane to avoid cardiac complications especially in presence of hypoxemia in these patients who are also on theophylline. Atracurium is preferred as relaxant for its advantage of easy and better reversibility.

Complete isolation of one of the lung is a must throughout the procedure to avoid life-threatening complication of accidental leakage of lavage fluid to the ventilated lung. For endotracheal intubation, a left sided disposable plastic double lumen tube of appropriate size with high volume low pressure cuff is preferred[1],[3]. The transparent plastic helps to monitor the tidal movements of respiratory moisture and monitoring the draining fluid for air bubbles to detect the spillage. Though fibre optic bronchoscopy is needed to confirm correct placement of the tube, it alone does not confirm functional separation of two lungs. This is done by 'air bubble detection' method for adequacy of cuff seal[1],[3]. In this method, the left endobronchial cuff seal is checked by ventilating the left lung alone while no air bubble should emerge the right open suction port connected through a tube to beaker of water. The two lugs are then ventilated for some time followed by similar checking for right endotracheal cuff seal.

During BPL, the patient is positioned to balance two major effects of the position[1],[3] i.e. hypoxemia and spillage of lavage fluid. Lateral decubitus with the lavaged lung dependent protects against the spillage. However, hypoxemia is worsened during the periods of lavage fluid drainage, by decreasing venous shunt due to improved pulmonary blood flow to dependent lavaged lung. Just reverse of this happens in lateral decubitus with lavaged lung nondependent. As a compromise many prefer to use supine position. However, we had used lateral position with lavage side dependent, keeping a close watch on any signs of hypoxemia indicated by fall in percentage saturation of oxygen on pulse oximeter.

Warm isotonic saline is used as the lavage fluid. It is infused by gravity by placing it above mid axillary line[1],[3]. Once the filling is complete, the fluid ceases to flow. Drainage is done by clamping the inflow line and unclamping the drainage line connected to a bottle kept 20 cm below the mid axillary line. The inflow and outflow lines are connected to the endotracheal tube by a Y adapter. The total lavage volume may be as high as 10  20 litres and takes several hours.

If a small leak is detected in the cuff seal, the position of the double lumen tube should be manoeuvred and confirmed before starting the procedure again[1],[3]. If the detected leak is large, the procedure has to be terminated. The patient is quickly put in lateral position with lavage side dependent and head low is given to hasten the drainage vigorously. Chest physiotherapy, suctioning through standard single lumen endotracheal tube is done. Patient should be put on ventilator on controlled ventilation with PEEP for few hours.

Two special problems for BPL occur in critically ill patients and children. Double lumen tube for a child is not available. Our patient was 14 years old weighing 30 kg and we were lucky to get 26G plastic double lumen tube (Bronchocath). Otherwise one has to do repeated BPL under local anaesthesia through fibre optic bronchoscope or use partial cardiopulmonary by pass in critically ill patients and children.

After the procedure, the decision of reversal and extubation was taken on the basis of clinical signs and blood gas report. This decision can be taken more precisely by using additional parameters like compliance of hemithorax of the lavaged side and peak inspiratory force.

References