A rare cause of perioperative stroke.

Perioperative stroke can occur following 0.2-0.3% of general surgical and orthopedic procedures. We are reporting a patient who developed multiple strokes in the immediate postoperative period following total knee replacement, where etiological workup revealed multiple pulmonary arteriovenous fistulae (PAVF). The significance of PAVF with paradoxical embolism in perioperative settings has rarely been reported in the literature.

Introduction

Stroke following surgical procedures is a devastating complication associated with high morbidity and mortality.[1] Paradoxical embolism is a rare cause for stroke in the young, accounting for less than 5% of all causes.[2] Here, we report an old lady with postoperative stroke, where paradoxical embolism via pulmonary arteriovenous fistulae (PAVF) was responsible.

Case Report

A 67-year-old lady with a long-standing history of dyspnea on exertion and cerebellar abscess 8 years back that was managed conservatively underwent right total knee replacement under spinal anesthesia for severe osteoarthrosis from a nearby center. She had no prior history of vascular risk factors or ischemic heart disease. The patient was well in the immediate postoperative period. On the second postoperative day, she was noted to have acute onset weakness of the left leg followed by right upper limb and was shifted to our center for further management.

On arrival, the patient was restless, drowsy with tachypnea and was having grade 0 power in the right upper limb and left lower limb with bipyramidal signs, without features of intracranial hypertension, cranial nerve dysfunction, fever or meningeal signs. She was evaluated with magnetic resonance imaging, which showed fluid attenuation inversion recovery (FLAIR) hyperintensities in the anterior and posterior circulation territories, some showing restricted diffusion suggestive of infarcts of varying ages [Figure 1a–d]. Vessel imaging was normal. Her chest radiograph showed multiple shadows, which was initially interpreted as secondary to aspiration [Figure 2a]. Arterial blood gas analysis showed type 1 respiratory failure (on O2by mask 6l/mt-p O242.7, p CO231 hco3 26, p H 7.54). She was intubated and ventilated in view of altered sensorium, respiratory distress and hypoxemia.

Figure 1

(a-b) -MRI –FLAIR axial images showing multiple chronic (arrow) infarcts bilateral hemispheres. (c-d) –Diffusion weighted image showing a few lesions (arrow) with reduced ADC (apparent diffusion coefficient) indicating that these infarcts are acute (<14 days)

Figure 2

(a) –Chest radiograph AP view of patient showing rounded shadows (arrow),contiguous with right main pulmonary artery. (b) –CT- Pulmonary angiogram-Maximal intensity projection image showing multiple high volume arterio-venous fisulae with arterial feeders from superior, middle and inferior branch of right pulmonary artery and inferior branch of left pulmonary artery(arrows)

Presentation in the early postoperative period following orthopedic surgery with focal neurological deficits, multiple cerebral infarcts and respiratory failure made us consider pulmonary embolism and postoperative stroke as the first possibility. There were no features to suggest fat embolism. Lower limb venous Doppler did not show any deep venous system thrombosis; however, the pelvic veins could not be studied. Her cardiac evaluation, including transthoracic echo and 24-h ECG, were normal.

The patient showed improvement in sensorium and weakness by the next week, but was having persistent hypoxemia (on ventilator SIMV, PS 12, PEEP 5, Fi O250% p O253, p CO226, Ph 7.45, with normal lung compliance) and had a few bouts of hemoptysis. A review of her chest radiographs showed nodular opacities in both lung fields appearing contiguous with pulmonary artery shadows, raising a suspicion of PAVF [Figure 1a]. Therefore, she underwent computed tomography (CT)-pulmonary angiogram, which showed multiple high-flow PAVF – a total of six in number – with arterial feeders from the right superior, middle and inferior as well as the left inferior pulmonary artery thus explaining her persisting hypoxemia and route for multiple cerebral embolism [Figure 2b]. She was not cooperative for transesophageal echo, but we performed a transcranial Doppler with agitated saline contrast, which showed high-intensity transient signals in the middle cerebral artery suggesting the presence of a right to left shunt. There were no other clinical features or family history of hereditary hemorrhagic telengectasia (HHT). However, genetic studies could not be done.

Subsequently, the patient was extubated and initiated on rehabilitation. She made a good recovery of her motor power (mRS = 2 at discharge) and is doing well on follow-up.

Discussion

Perioperative stroke is an extremely rare complication of general surgical and orthopedic procedures. Hart et al.[2] in one of the earliest series had suggested cardioembolism as a single major cause, with atrial fibrillation accounting for over 1/3rd cases. Presence of noncoronary cardiac disease, emergency nature of surgery, general anesthesia and intraoperative arrhythmias, especially atrial fibrillation, were major predictors of perioperative stroke following total knee replacement in a multivariate analysis.[1]

Pulmonary AV fistula, a rare congenital communication between the pulmonary artery and the vein, without an intervening capillary bed can predominantly present with respiratory symptoms like dyspnea, exercise intolerance and hemoptysis in adults.[3] It can also lead to cerebral complications like transient ischemic attacks, strokes or brain abscess due to paradoxical embolism.[45] Eighty percent to 90% of patients with PAVF have other manifestations of HHT.[5]

Our patient had a prior history of brain abscess for which she had not been evaluated. In the acute setting, chest radiograph was misinterpreted as aspiration pneumonia, which is not uncommon.[6] This history along with the finding of persistent mild hypoxemia despite adequate ventilation and chest radiograph finding made us consider this rare possibility that could be confirmed by CT-pulmonary angiogram. Different sources for systemic embolism have been described in patients with PAVF, including lower limb or pelvic vein thrombosis, in situ thrombosis in the pulmonary veins and air as well as fat embolism.[78] The former mechanism seems likely in our patient as she developed the event in the early postoperative period.

Management strategies include prophylaxis and treatment of deep vein thrombosis and obliteration of the PAVF by endovascular methods (if the size is above 2 cm or feeding artery diameter is above 2 mm) once the patient has recovered to prevent further events.[3] However, our patient refused to undergo embolotherapy and opted for medical follow-up.

This case is being reported to highlight a few points. PAVF, a rare cause of stroke, can predispose to ischemic events during the perioperative period, especially following orthopedic procedures where the risk of deep vein thrombosis is high. Recognizing this preoperatively can alert the surgeon and anesthesiologist, thereby reducing the risk of complications.