1Department of Anaesthesia, 2Department of Histopathology, Northern General Hospital, Herries Road, Sheffield S5 7AU, UK. 3University Department of Anaesthesia, K Floor, Royal Hallamshire Hospital, Glossop Road, Sheffield S10 2JF, UK*Corresponding author
Accepted for publication: July 19, 2000
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Abstract |
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Br J Anaesth 2000; 85: 9215
Keywords: complications, hypoxia; heart, bubble contrast echocardiography; intensive care
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Introduction |
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In contrast, the adult patient with an asymptomatic inter-atrial defect may develop an acute RLIAS following a cardiac or respiratory insult. Acute RLIAS is a separate clinical entity from the Eisenmenger syndrome. Acute RLIAS is often overlooked as a cause of hypoxia2 but early diagnosis can direct therapy and avoid unnecessary invasive investigations. The three cases reported here illustrate the need to consider RLIAS in the differential diagnosis and investigation of profound hypoxia.
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Case reports |
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Initially the underlying cause of this patients hypoxia was not clear. Transthoracic echocardiography (TTE) demonstrated good left ventricular function, mild mitral regurgitation and septal hypertrophy. A lung perfusion scintographic scan showed no evidence of pulmonary embolism. Thoracic computerized tomography revealed non-specific bilateral shadowing of the lung fields consistent with adult respiratory distress syndrome (ARDS) or infection. Despite antibiotic therapy followed by a trial of prednisolone 70 mg day1 for possible ARDS, he continued to deteriorate and required reintubation and positive pressure ventilation. A pulmonary artery flotation catheter demonstrated a cardiac index of 2.1 litres min1 m2, mean right atrial pressure of 8 mm Hg, mean pulmonary arterial pressure of 37 mm Hg and pulmonary artery occlusion pressure of 3 mm Hg. During inspired nitric oxide therapy at 20 p.p.m. the cardiac index increased to 3.8 litres min1 m2, the mean right atrial pressure was 4 mm Hg, mean pulmonary arterial pressure 34 mm Hg and pulmonary artery occlusion pressure 5 mm Hg. The PaO2 increased from 10.5 to 24.5 kPa on a FIO2 1.0.
A cardiology opinion was sought concerning the possibility of an inter-atrial shunt, but this diagnosis was thought to be excluded by the absence of a persistent right-to-left pressure gradient; right atrial pressure range of 48 mm Hg with a pulmonary artery occlusion pressure range of 35 mm Hg. However, an inter-atrial defect was discovered fortuitously during pulmonary angiography when a catheter passed from the right atrium into the left atrium. Bubble contrast transoesophageal echocardiogram (TOE) demonstrated RLIAS with severe impairment of right ventricular function (Fig. 1).
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Patient 2
A 38-yr-old woman presented with platypnoea and cyanosis that developed over a period of 4 days. Sitting upright exacerbated her breathlessness and she was more comfortable when lying flat despite being profoundly hypoxic. She had a past history of chronic renal impairment and aortic incompetence. At presentation she was an inpatient recuperating from an episode of infective endocarditis and gastrointestinal bleeding for which she had required treatment in the ICU.
On physical examination she was apyrexial, heart rate 110 beats min1, arterial pressure 120/80 mm Hg and the jugular venous pressure was not elevated. An aortic murmur was present, but unchanged from previous examinations; respiratory rate was 20 b.p.m. and chest auscultation was normal. Arterial blood gases on a FIO2 0.6 were: pH 7.6, PaO2 5.6 kPa, PaCO2 3.8 kPa, base excess 6.3 mmol litre1. A chest radiograph showed a small right pleural effusion. Lung perfusion scintographic scan demonstrated a single segment perfusion defect in the right mid-zone. A preliminary diagnosis of pulmonary embolism was made but the decision to anticoagulate was deferred until a pulmonary angiogram could be performed in view of her recent history of gastrointestinal haemorrhage. During pulmonary angiography, the catheter passed through a patent foramen ovale into the left atrium and left upper lobe pulmonary vein. Radio-opaque dye flowed from the right to the left atrium. Pulmonary arteriography demonstrated no emboli. Mean pulmonary arterial pressure was 12 mm Hg and mean right atrial pressure was 13 mm Hg compared with 8 mm Hg in the left atrium. Right atrial PO2 was 2.8 kPa and the left atrial PO2 was 5.5 kPa. Transthoracic echocardiogram revealed a right-sided pericardial effusion, 4.5 cm in depth, compressing the right ventricle. Left ventricular function was good. Pericardial tap brought immediate relief of the patients hypoxia; the PaO2 rising from 5.8 to 30.4 kPa, on oxygen 10 litres min1 by facemask.
Patient 3
A 46-yr-old man presented with breathlessness 4 days after right hemicolectomy for caecal carcinoma. Axillary temperature was 38.5°C, he had a sinus tachycardia 135 beat min1, arterial pressure 90/60 mm Hg and a respiratory rate of 32 breath min1. PaO2 was 4.1 kPa and PaCO2 4.2 kPa on room air. Oxygen at maximum flow via a facemask did not improve his hypoxia and he was transferred to ICU. FIO2 0.9 with CPAP 5 cm H2O produced a PaO2 7.5 kPa. The patient was not distressed despite his hypoxia and was able to tolerate lying flat for a pulmonary angiogram. Pulmonary angiogram revealed a large embolus in the left-upper lobe pulmonary artery with smaller emboli in the right middle lobe pulmonary artery and right pulmonary vessels peripherally. The catheter passed from the right atrium to the left atrium. Mean right atrial pressure was 13 mm Hg, left atrial pressure 11 mm Hg and mean pulmonary arterial pressure 27 mm Hg. Left pulmonary venous PO2 was 32.3 kPa but the radial arterial PaO2 was 6.24 kPa. A Greenfield inferior vena cava filter was deployed with its base at the level of the L3-L4 disc space. A bolus of tissue plasminogen activator 5 mg i.v. plus an infusion of 5 mg h1 was instituted. The patients oxygenation improved over the next 3 days and thereafter his recovery was uneventful.
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Discussion |
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Platypnoea is a sign that is strongly associated with RLIAS. This sign, first described in 1949 and given the name platypnoea in 1969, occurs in approximately one quarter of reported cases of acute RLIAS.23 24 A corresponding postural change in oxygenation is known as orthodeoxia.25
RLIAS is often diagnosed unexpectedly during investigation for other causes of acute hypoxia.26 A pulmonary angiography catheter may pass through an inter-atrial defect, as occurred in our patients, but the angiogram may be reported as normal despite the presence of a significant RLIAS.4 13 Lung perfusion scintigraphy indicates RLIAS when early activity is detected in the brain, myocardium and kidneys.27 It has been advocated as the investigation of choice28 but failed to detect RLIAS in our first and second patients and in several other reported cases.2 4 29 Injection of radiolabelled microaggregates into the arm has resulted in a normal perfusion scan whereas injection into the foot demonstrated shunt because of preferential flow from the IVC across the interatrial defect.30
Bubble contrast echocardiography has the greatest sensitivity for detecting RLIAS and has the advantage that it is a relatively non-invasive technique that can be performed at the bedside.1 31 32 A syringe filled with 9 ml saline and 1 ml air is agitated, macroscopic bubbles expelled and the remaining microbubble emulsion injected i.v. The test is positive if microbubbles are seen in the left atrium (Fig. 1) within two to three cycles of the initial appearance in the right atrium.
Bubble contrast echocardiography has detected RLIAS as a first line investigation15 22 33 and when preceding pulmonary angiogram and lung perfusion scintigram have both been falsely negative.2 12 29 Injection of contrast via the leg may increase the sensitivity of the test as most shunting occurs via the IVC.34 RLIAS is exacerbated when intra-thoracic pressure is increased by PEEP in the artificially ventilated patient35 and during coughing or the Valsalva manoeuvre.31 Each of these manoeuvres can increase the likelihood of detecting RLIAS by echocardiography.
Bubble contrast echocardiography is a safe technique widely reported in the investigation of chronic RLIAS, particularly in patients who are thought to have developed paradoxical embolism.36 37 Paradoxical embolism is not commonly associated with profound hypoxia as these patients present with systemic embolic phenomena. Patient 1 had a past history of cerebrovascular events and whether these were caused by paradoxical emboli is an interesting matter for conjecture.
Treatment of RLIAS is treatment of the underlying cause and/or closure of the PFO or ASD. Successful closure of the inter-atrial defect is frequently reported38 although some patients have died following its closure because of right heart failure.20 35 Temporary closure may be achieved with a balloon catheter10 but definitive closure requires either open surgery or a percutaneous technique using an occlusive device.6
Patient 1 developed acute RLIAS and platypnoea. The nature of the precipitating cause remains uncertain. However, the raised perioperative pulmonary arterial pressures and the subsequent beneficial effect of nitric oxide suggests that pulmonary vasoconstriction was a contributing factor. The diagnosis of RLIAS was discounted because of the absence of a significant right-to-left pressure gradient between the atria. By the time RLIAS was diagnosed, the patients condition precluded surgical closure of his ASD. The use of bubble contrast during the patients first echocardiogram might have revealed the RLIAS early enough for surgery to be feasible.
Patient 2 presented with platypnoea; as this is highly indicative of RLIAS, early use of bubble contrast echocardiography was indicated. A lung perfusion scintogram failed to detect it and was falsely positive for pulmonary embolism. RLIAS was discovered during pulmonary angiography when the catheter passed through a PFO. Early use of bubble contrast echocardiography might have saved the patient from these more invasive investigations.
Patient 3 demonstrates that acute RLIAS can occur without platypnoea and without high pulmonary arterial pressures.
In conclusion, the diagnosis of acute RLIAS should be considered in any patient with unexplained acute hypoxia particularly if platypnoea or orthodeoxia is present. Neither pulmonary hypertension nor a pressure gradient between the right and left atria need be present. Bubble contrast echocardiography is more sensitive in detecting RLIAS than more invasive techniques and should be performed early.
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