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LETTER TO EDITOR Table of Contents   
Year : 2008  |  Volume : 11  |  Issue : 1  |  Page : 53-54
An unusual cause of hypoxaemia in a patient with pneumonia


Department of Cardiothoracic Anaesthesia and Intensive Care, Universitá Vita-Salute San Raffaele, Milano, Italia e Istituto Scientifico San Raffaele, Milano, Italia

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How to cite this article:
Bove T, Crescenzi G, Calabro M, Biselli C, Crivellari M, Maj G, Landoni G, Zangrillo A. An unusual cause of hypoxaemia in a patient with pneumonia. Ann Card Anaesth 2008;11:53-4

How to cite this URL:
Bove T, Crescenzi G, Calabro M, Biselli C, Crivellari M, Maj G, Landoni G, Zangrillo A. An unusual cause of hypoxaemia in a patient with pneumonia. Ann Card Anaesth [serial online] 2008 [cited 2019 Nov 15];11:53-4. Available from: http://www.annals.in/text.asp?2008/11/1/53/38453


Sir,

A 66-year-old man was admitted to the cardiothoracic intensive care unit after aortic arch replacement. In the intensive care unit, the patient was sedated with propofol 2 mg/kg h administered intravenously and was being mechanically ventilated. After discontinuing propofol infusion, the patient developed focal motor crisis, which was treated with 2 mg of lorazepam administered intravenously. Computerized tomographic scan of the head showed an ischemic focus in the left cerebral hemisphere. It was decided to mechanically ventilate him until his neurological status improved. During the next days, arterial blood gas analysis showed trend towards decrease in arterial oxygen tension (PaO 2 ) and increased need for inspired oxygen concentration and positive end-expiratory pressure (PEEP). On the fourth postoperative day, the patient developed elevated leukocyte counts and fever. Chest X ray showed bibasilar infiltrates. Protected minibronchoalveolar washing samples were cultured and yielded Aspergillus, and therapy with liposomal Amphotericin-B was initiated to treat the fungal pneumonia. Alveolar recruitment maneuvers were started, but these maneuvers seemed to aggravate hypoxia. At this point, a right-left shunt via a possible atrial septal defect was suspected. Trans-oesophageal echocardiography (TOE) showed a Type 1/1A atrial septal aneurysm with the following characteristics: the atrial septal aneurysm projected into the right atrium during diastole with early systolic bulging into the left atrium followed by rightward crossing-over motion in mid-systole and during inspiration; an excursion of 10 mm into the right atrium and an aneurysmal base amplitude of 18 mm were observed [Figure - 1]. Moderate pulmonary hypertension was detected. Right-to-left shunt was noted during inspiration initiated by mechanical ventilation with high PEEP (10 cmH 2 O). A contrast study with 10 ml of vigorously agitated saline solution injected in the right internal jugular vein during a series of Valsalva's maneuvers revealed increase of the shunt: more than five microbubbles were observed in the left atrium during the first three beats [Figure - 2]. A diagnosis of patent foramen ovale (PFO), with right-to-left shunt (due to moderate pulmonary hypertension), was made. The patient was treated with inhaled nitric oxide (20 parts per million) to decrease the pulmonary vascular resistance. There was a dramatic improvement in PaO 2 , which increased from 60 to 160 mmHg, with the same inspired oxygen concentration. This permitted decrease of inspired oxygen concentration to 0.4 and PEEP to zero. Nitric oxide was gradually reduced when the pulmonary artery pressure returned to normal values. At this time, paradoxical motion of the interventricular septum and bulging of the interatrial septum to the right were not seen by TOE.

The presence of PFO should be considered and looked for as potential cause of perioperative hypoxaemia. In this patient, two reasons could explain the hypoxaemia: intrapulmonary shunt caused by pneumonia and right-to-left intracardiac shunt caused by PFO.

The application of PEEP therapy can increase the pulmonary vascular resistance, creating a right-to-left shunt. In fact, it is reported that shunt fraction increases with PEEP in the majority of patients with a PFO and that when PEEP was added, right-to-left shunt through a PFO observed by TOE in the early inspiratory phase of mechanical ventilation became continuous. [1],[2] Therefore, alternative treatment of the hypoxaemia in ventilated patients with PFO could be the inhaled nitric oxide. [2] Arterial oxygenation improves via a reduction of intrapulmonary shunt by decrease in pulmonary artery pressure and outflow resistance, reversing the right-to-left atrial pressure gradient and consequently the right-to-left intracardiac shunt.

PFO should be systematically investigated in mechanically ventilated patients with unexplained severe arterial hypoxaemia. If present, a low concentration of inhaled nitric oxide may reverse the atrial pressure gradient, inducing a functional closure of the foramen ovale and a dramatic improvement in arterial oxygen concentration.


   Acknowledgments Top


We are indebted to Castelnuovo Lara, RN; Costantini Marco, RN; e Tolja Marina, RN, for the care provided to this patient and for revising the manuscript.

 
   References Top

1.Jaffe RA, Pinto FJ, Schnittger I, Brock-Utne JG. Intraoperative ventilator-induced right-to-left intracardiac shunt. Anesthesiology 1991;75:153-5.  Back to cited text no. 1  [PUBMED]  
2.Fellahi JL, Mourgeon E, Goarin JP, Law-Koune JD, Riou B, Coriat P, et al. Inhaled nitric oxide-induced closure of a patent foramen ovale in a patient with acute respiratory distress syndrome and life-threatening hypoxaemia. Anesthesiology 1995;83:635-8.  Back to cited text no. 2  [PUBMED]  [FULLTEXT]

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Correspondence Address:
Giovanni Landoni
Department of Cardiothoracic Anaesthesia and Intensive Care, Istituto Scientifico San Raffaele, Milano, Italia

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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/0971-9784.38453

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