Bilateral pulmonary emboli and pneumothoraces after off-pump coronary artery bypass graft in a patient with heparin induced thrombocytopenia: a case report

  1. 1.  University of California San Francisco - Fresno

Abstract

Patients presenting to the emergency department with dyspnea after recent coronary artery bypass graft (CABG) present a unique diagnostic challenge. There have been no previous reports in the literature of a patient with bilateral pulmonary emboli (PE) and bilateral pneumothoraces after CABG. We describe an adult male who presented with shortness of breath after recent CABG. He was found to have bilateral pneumothoraces, which were treated satisfactorily with a single tube thoracostomy. He remained persistently hypoxic and tachycardic and further investigation revealed bilateral pulmonary emboli. He was also diagnosed with heparin induced thrombocytopenia (HIT). PE is much more common after off-pump CABG. HIT is a potential cause of thrombosis after heparin exposure.

Introduction

The number of cardiac surgical procedures performed has increased exponentially since its advent in the 1950s, and with it an increase in postoperative pulmonary complications. Post cardiac surgery patients often present to the emergency department (ED) with shortness of breath due to a wide variety of possible etiologies. To our knowledge, this is the first case report of a patient with bilateral pneumothoraces and bilateral pulmonary emboli presenting with dyspnea after coronary artery bypass graft (CABG).

Presenting Concerns

An 82 year old male on post-operative day 11 status post CABG presented to our emergency department with dyspnea. After presenting with chest pain 12 days prior to presentation, he underwent left heart catheterization which showed severe 3 vessel disease. The following day he had off-pump 3 vessel CABG with left internal mammary artery graft to left anterior descending artery. Intraoperative heparin and partial dose protamine were given. He was discharged 3 days prior to presentation.

Clinical Findings

He had shortness of breath for two days but was uncertain of the context or exact onset. He reported a non-productive cough but no fever. He had new bilateral lower extremity edema that he noticed the day prior to presentation, but denied any chest pain, palpitations, orthopnea or paroxysmal nocturnal dyspnea. He had otherwise been well with an otherwise negative review of systems.

He had a history of hypertension, atrial fibrillation, diabetes, and hyperlipidemia. He was a non-smoker with no allergies and no family history of coagulopathy. His medications included aspirin, metoprolol, amlodipine, lovastatin, lisinopril, and amiodarone and he had been complaint.

The initial physical examination included the following vital signs: Blood pressure (BP) 184/77, heart rate (HR) 92, respiratory rate (RR) 36, temperature 36.8 C, and oxygen saturation (Sa02) 97% on 6 liter nasal cannula. He was speaking four-word sentence and had accessory muscle use. The midline sternotomy scar was clean and intact with no drainage through the staples. He had decreased breath sounds bilaterally with diffuse wheezes and no rales. Examination of his lower extremities revealed 2+ pitting edema in his bilateral extremities. The remainder of his physical exam was within normal limits.

Diagnostic Focus and Assessment

He was placed on BiPAP and minutes later he appeared clinically improved with the following vital signs: BP 121/59, HR 87, RR 27, Sa02 100%. The initial ECG showed sinus tachycardia at a rate in the high 90s with normal intervals and no ST or T wave changes. A bedside ultrasound was done which showed no pericardial effusion. Portable chest x-ray (CXR) followed which showed bilateral pneumothoraces (figure 1). BiPAP was discontinued and a single right sided chest tube was placed. Repeat CXR showed evacuation of the pneumothoraces.

Figure 1: Initial chest x-ray demonstrating large right and small left sided pneumothorax.

His laboratory tests showed a white blood cell count of 19.8 with left shift, hemoglobin of 12.1 (up from post-op hemoglobin of 9.6 recorded 6 days ago), platelets of 250k/uL, INR 1.2, glucose 442, troponin 0.031 (normal = <0.040), bnp 209. Thirty minutes after thoracostomy he was normotensive but tachycardic at 100, tachypneic to 29, and hypoxic with a Sa02 of 93% on 15 liter non-rebreather. Due to persistent hypoxia a Computed tomigraphy pulmonary angiogram was ordered which showed large pulmonary emboli in the right main pulmonary artery extending into right upper, middle, and lower lobes as well as left superior segmental branch (Figure 2, 3).

Figure 2: Computed tomography pulmonary angiogram axial view showing large right sided pulmonary embolism.

Figure 3: Computed tomography pulmonary angiogram coronal view showing large right sided pulmonary embolism

Follow-up and Outcomes

The patient was placed on a heparin drip and admitted. When his platelets plateaued at 69K/uL on hospital day three he was diagnosed heparin induced thrombocytopenia (HIT) with thrombosis and was switched to lepirudin. The remainder of his coagulopathy work-up was unremarkable. His lower extremity ultrasound found bilateral deep vein thrombosis. He was started on warfarin, the chest tube was removed on hospital day five, and he was discharged after a fifteen day stay. He was readmitted one month later with a supratherapeutic INR of 19.

Discussion

The incidence of primary cardiac complications causing dyspnea is low. In one prospective study with over 3400 CABG patients causes of 30 day re-admission included arrhythmia/heart block most commonly in 3% of patients, followed by CHF in 1.6%, pericardial effusion/tamponade in 0.4%, and MI in 0.2% (Lee 2012). This patient had an unremarkable EKG, negative troponin, minimally elevated bnp, and a negative bedside ultrasound for effusion.

Respiratory complications after CABG are much more common, occurring in up to 95% of patients. The differential diagnosis of pulmonary causes is broad and frequencies vary. Pleural effusion is most common and found in up to 95% of patients in one series, followed less commonly by atelectasis in up to 88%, phrenic nerve paralysis in up to 75%, diaphragmatic dysfunction in up to 54% and pneumonia in up to 20% of patients (Wynne 2004).

There is general agreement in the cardiac surgery literature that acute PE after cardiopulmonary bypass is uncommon (Goldhaber 2004). One meta-analysis of over 8553 post-CABG patients over 34 years found 111 PEs, an incidence of 1.3% (Protopapas 2011), a second study found the incidence varied from 0-9.5% (Kuklinski 2007). PE occurs more frequently after off-pump CABG. A study of 326 consecutive CABG patients found the frequency of PE with off-pump CABG was twice that of conventional CABG (Lee 2011). While the standard intraoperative heparin dose for conventional CABG is ³300U/kg, most surgeons prefer a low-dose intraoperative heparin regimen of ²150 U/kg for off-pump CAGB (Englberger 2008). Some authors have proposed the reduced heparin dose, along with reduced hemodilution, as the cause of the difference in incidence of thromboembolism between off-pump and conventional CABG (Hashimoto 2006).

In adult cardiac surgery, the frequency of HIT is 1.0-2.4% (Jang 2005). Though his platelets dropped from 224k/uL preoperatively to 134k/uL on post-op day two, HIT was not suspected during the patient's initial visit. The diagnosis of HIT is based on its typical clinical picture including the 4 T's: Thrombocytopenia, Timing of the platelet fall after heparin exposure, the presence of Thrombosis, and exclusion of other causes for thrombocytopenia. The treatment is immediate cessation of all heparins and alternative anticoagulation with argatroban (Warkentin 2003). Our patient's eventual diagnosis of HIT with thrombosis raises the prospect that his hypercoagulable state and subsequent thromboembolism began after receiving intraoperative heparin.

Pneumothoraces are equally uncommon, with a reported incidence of 1.4% of patients undergoing cardiac surgery (Douglas 2002). Median sternotomy can sever pleural reflections leading to an iatrogenic interpleural communication. As in this patient, a unilateral chest tube has been shown to be effective in treating bilateral pneumothoraces (Wagar 2009, Lee 1999).

Summary

Though PE and PTX are uncommon complications, they are life threatening and must be considered in patients presenting with dyspnea after CABG. The incidence of PE after off-pump CABG is double that of conventional CABG. To our knowledge, this is the first case report of a patient with bilateral pneumothoraces and bilateral pulmonary emboli after CABG. It reinforces the need for continued investigation in the presence of persistently abnormal vital signs, highlights the thromboembolic differences between off-pump and conventional CABG, and reminds us that HIT is a potential cause of thrombosis after heparin exposure.

References

Lee R, Homer N, Andrei AC, et al. Early readmission for congestive heart failure predicts late mortality after cardiac surgery. J Thorac Cardiovasc Surg. 2012;144(3):671-6. doi: 10.1016/j.jtcvs.2012.05.031.

Wynne, R and Botti, M. Postoperative Pulmonary Dysfunction in Adults After Cardiac Surgery With Cardiopulmonary Bypass: Clinical Significance and Implications for Practice. Am J Crit Care. 2004; 13, 5: 384-393.

Goldhaber SZ, Schoepf UJ. Pulmonary embolism after coronary artery bypass grafting. Circulation. 2004;109(22):2712-5.

Protopapas, et al. Pulmonary embolism following coronary artery bypass grafting. J Card Surg. 2011;26(2):181-8. doi: 10.1111/j.1540-8191.2010.01195.x.

Kuklinski D, Tevaearai H, Eckstein F, et al. Acute pulmonary embolectomy three days following a coronary artery bypass graft procedure. Anaesthesia & Intensive Care. 2007;35(2):294-297.

Lee C, Kim Y, Shim D, et al. The detection of pulmonary embolisms after a coronary artery bypass graft surgery by the use of 64-slice multidetector CT. Int J Cardiovasc Imaging. 2011 Jun;27(5):639-45. doi: 10.1007/s10554-011-9868-4.

Englberger L, Streich M, Tevaearai H, et al. Different anticoagulation strategies in off-pump coronary artery bypass operations: a European survey. Interact CardioVasc Thorac Surg (2008) 7 (3): 378-382. doi: 10.1510/icvts.2007.169086.

Hashimoto M, Aoki M, Okawa Y, et al. Massive pulmonary embolism after off-pump coronary artery bypass surgery. Jpn J Thorac Cardiovasc Surg. 2006 Nov;54(11):486-9.

Jang IK, Hursting MJ. When heparins promote thrombosis: review of heparin-induced thrombocytopenia. Circulation 2005;111:2671-2683

Warkentin TE. Heparin-induced thrombocytopenia: pathogenesis and management. Br J Haematol. 2003 May;121(4):535-55.

Douglas JM, Spaniol S. Prevention of postoperative pneumothorax in patients undergoing cardiac surgery. Am J Surg. 2002;183:551-553

Wagar S, Vaughan P, Sarkar P. Bilateral pneumothoraces treated with a single chest drain. Br J Hosp Med (lond) 2009;70(6):359.

Lee YC, et al. Contralateral Tension Pneumothorax Following Unilateral Chest Tube Drainage of Bilateral Pneumothoraces in a Heart-Lung Transplant Patient. Chest. 1999; 116:1131-1133. doi: 10.1378/chest.116.4.1131.

Showing 1 Reviews

  • Me
    Teresa Chan
    Originality of work
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    1

    Hi Jeff,
    Thanks for the opportunity to review your work.  To situate myself, I am a Canadian Emergency Physician at McMaster University, and I work at a centre with a moderate volume of CABG cases.

    Overall, I think this piece is interesting. I find case studies a fascinating study in exceptions to our typical clinical reasoning, and as such, they can be very interesting.  However, I think one of the big challenges in writing them, therefore, is to adequately represent and present the diagnostic thinking that goes into the decision making that might guide you through a case such as this.  I would suggest that in the next little while, read through this piece again to ensure that the reasoning and thinking is clear to the reader, without them having to infer what you were doing where... and more importantly without having to infer WHY you were doing something.
    One thing that puzzles me... You wrote this as "we" throughout, but you are a single author?  I would suggest that you review the submission process and ensure any missing authors are listed as well.


    I will present the remainder of this review, providing feedback re: various sections below.

    Abstract:
    Well written, concise. However the latter half of this paragraph reads a bit awkwardly.
    "He remained persistently hypoxic and tachycardic and further investigation revealed bilateral pulmonary emboli. He was also diagnosed with heparin induced thrombocytopenia (HIT). PE is much more common after off-pump CABG. HIT is a potential cause of thrombosis after heparin exposure." 
    Would suggest ending the sentence after tachycardic. And then a new sentence that better interlinks the PE to HIT.

    Introduction:
    You state in this section 'To our knowledge'... But then do not back up why you know this is the first case report.  Please clarify your search strategy if you wish to make this assertion.

    Presenting Concerns:
    Suggest changing the title of this section to "Presentation". Concerns would suggest that this paragraph should be written in the tone/perspective of the patient, and yet you use very medical terms and describe this case quite avidly, but with medical terminology.  

    Clinical Findings:
    Should you have separate subheadings History, Physical, etc. for ease for the reader?  Please clarify what this means "He was speaking four-word sentence" (check grammar too).  Do you mean he was speaking 4-words at a time? Do you mean he had 4-word dyspnea?

    DIAGNOSTIC FOCUS AND ASSESSMENT
    This section also seems misnamed?   BiPAP (and you should explain and define it) is more management than assessment or diagnostics.  Maybe the term Management & Investigations would be better? I am not sure exactly how you would like to communicate the headings, but I would suggest you take heed.
    This section is where you might clarify some of the clinical decisions more.  It is difficulty for me to understand why he was thrown on BiPAP. I can guess why, but again, i'm not 100% sure.


    Follow-up and Outcomes:
    "He was readmitted one month later with a supratherapeutic INR of 19." <-- is this relevant? If so, please explain why.


    Discussion
    It would be lovely to have a table with common post-CAGB problems...

    "There is general agreement in the cardiac surgery literature that acute PE after cardiopulmonary bypass is uncommon " <-- do you mean experts agree? Or that multiple studies all epidemiologically show this?  Not sure that people need to 'agree' that acute PE after CABG is uncommon - more important is to state that multiple studies have shown this.

    Summary:
    I like this.  It is short, and summarizes your points.

    Pictures:
    Mostly they are too small.
    Figure 3 - please add an arrow (preferably in colour) to point at the PE.

    References:
    In your present reference style, your list of references should be in the order of the last name of the first author. Currently this is in order of appearance, which you should do, if you use a numbered reference system. But you have chosen the format you have, so then you write the references in alphabetical order.


    Typographic things:
    1) For numbers less than two digits (e.g. 3 vessel disease), usually you spell out the word.  For digits > 2 digits (e.g. 12) leave as a number.
    2) BiPAP appears under Diagnostic Focus section and is not defined nor explained.  You should introduce a new term the first time with the full version, and then give it some context. Perhaps a citation as to why that would be appropriate.
    3) Spelling wise, I believe it should read: "no ST- or T-wave changes" (dashes)
    4) "Computed tomigraphy pulmonary angiogram" <-- Check spelling. I believe tomography is spelt different - and also consider putting (CT-PA) in brackets after.

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