Arteriovenous fistula and high output cardiac failure in a double lung transplant patient

Abstract

We present a case of a high cardiac output (CO) arteriovenous fistula (AVF) with pulmonary hypertension (PH) post-double lung transplant presenting for AVF occlusion. The patient presented with a CO of 9.83 L/min, pulmonary artery pressures of 64/16, inferior vena cava dilatation and an AVF between the left common iliac artery and vein. Given her anaesthetic considerations, we elected to proceed with local anaesthesia and sedation. Trial balloon occlusion resulted in an increase in blood pressure and a headache that resolved with balloon deflation. Successful final occlusion with an endovascular stent was completed without adverse events. PH is a complex pathophysiology with the potential for catastrophic decompensation. Anaesthesiologists must consider a patient’s comorbidities and the procedure to safely administer anaesthesia without complications.

Background

Pulmonary hypertension (PH) is a cardiopulmonary pathology associated with several systemic diseases, including, but not limited to, chronic obstructive pulmonary disease (COPD), sleep apnea, HIV infection, and ischaemic heart disease. PH is defined as a mean pulmonary artery (PA) pressure ≥25 mm Hg at rest measured by right heart catheterisation.¹ PH presents many conflicting anaesthetic considerations and challenges; an anaesthesiologist must balance anaesthesia and analgesia with hypoxia and hypercarbia while avoiding precipitating acute perioperative right ventricular (RV) failure and haemodynamic collapse.² Patients with PH are at increased risk of postoperative morbidity, with up to 42% of patients experiencing complications such as arrhythmias, heart failure, myocardial ischemia, respiratory failure, delayed extubation, sepsis and renal insufficiency.^{3 4} Furthermore, perioperative mortality rates vary from 1% to 18%.⁵ We present a case of an incidental high cardiac output (CO) left common iliac artery to left common iliac vein arteriovenous fistula (AVF) causing PH after a double lung transplant; the patient first presented for balloon occlusion, and an Amplatzer ventricular septal occlusion device was used during a second procedure, which was unsuccessful. The AVF was completely occluded during a third procedure using a stent graft iliac extension. The patient has consented to publication of her medical information for the benefit of educating healthcare professionals.

Case presentation

A 41-year-old woman 1.5 years post-double lung transplant for severe idiopathic PH presented for angiography and occlusion of a left common iliac artery to left common iliac vein AVF. Her double lung transplant postoperative course was complicated by acute kidney injury (AKI) requiring haemodialysis, right heart failure, failure to wean, tracheostomy, new onset type 2 diabetes mellitus and multiple blood transfusions. She presented for a scheduled 6 month follow-up and her CO was found to be persistently elevated at 9.83 L/min, along with elevated PA pressures of 64/16. The 1 year post-transplant follow-up once again showed a dilated inferior vena cava (IVC), ongoing elevated right heart and PA pressures, and incidentally, the cardiologist documented high IVC oxygen saturations. The cardiologist performed an iliac arteriogram and identified the AVF (figure 1).

Figure 1.

Abdominal angiogram showing dilated inferior vena cava.

The patient’s medical history is significant for generalised anxiety disorder, previous lumbar discectomy and idiopathic PH. Post-transplant, she was treated with mycophenolate, tacrolimus and prednisone for immunosuppression, as well as digoxin, furosemide and metolazone for heart failure. A post-transplant cardiac MRI revealed severe RV and left ventricular (LV) dilatation without signs of constriction or infiltrative cardiomyopathy. A transthoracic echocardiogram (TTE) revealed an enlarged IVC, elevated right heart pressures and normal LV function.

The anaesthetic plan for the patient was to induce general anaesthesia for the procedure; however, given her anaesthetic considerations, including severe PH, recent double lung transplant, prior tracheostomy and the percutaneous nature of the procedure, we decided in concert with the interventional radiologist and patient to proceed with local anaesthesia and sedation. The patient was placed supine on the radiolucent table and standard Canadian Anesthesiologists’ Society (CAS) monitors, including a 5-lead ECG, were applied. Intravenous and left radial artery access were obtained for all procedures. Supplemental oxygen was applied via face mask at 8 L/min, and end-tidal CO₂ was continuously sampled. The patient was administered fentanyl 50 mcg intravenous and two doses of midazolam 1 mg intravenous prior to left femoral vein cannulation. The radiologist floated a pulmonary artery catheter (PAC) via the right femoral vein under fluoroscopic guidance. The patient experienced multiple premature ventricular complexes and short runs of ventricular tachycardia during placement in the PA. The patient required vasopressin 0.5 IU intravenous (19 IU total) and phenylephrine 40 mcg intravenous (400 mcg total) boluses titrated to maintain a systolic blood pressure greater 110 mm Hg and a mean arterial pressure greater than 65 mm Hg. She did not require any inodilators.

Following contrast arteriovenogram, it was determined that the AVF was more of an ‘H’ shape, making it challenging to correct with the equipment available. A trial occlusion with an intravascular balloon was attempted. At time 0, the occlusion balloon was inflated, resulting in a rapid increase in systemic blood pressure to 160/70 mm Hg. The patient complained of a nuchal headache that persisted throughout the occlusion trial, promptly resolving with deflation of the occlusion balloon. The patient did not complain of dyspnea, angina or presyncope. There were no ECG changes. Heart rate remained stable at approximately 60 bpm, with exception of the transient increase to 82 with balloon occlusion. This resolved over the course of the occlusion trial. The trial was stopped after 8 min due to left leg ischaemic pain. This resolved with deflation of the balloon. All devices were removed at the end of the case, haemostasis was achieved, and the patient was transferred to the recovery room in stable condition and discharged home later that evening.

Two months later, the patient presented for occlusion using an Amplatzer cardiac septal defect closure device. Given the success of the previous procedure from an anaesthesia aspect, the decision to use local anaesthesia and judicious sedation was made. Unfortunately, the procedure was unsuccessful with persistent flow around the occluder, and she subsequently developed non-dialysis-dependent AKI. Sedation was provided with titrated doses of fentanyl up to 100 mcg and midazolam 2 mg. Hydrocortisone 25 mg intravenous for adrenal insufficiency prophylaxis was administered. Haemodynamics were remarkably stable throughout the procedure, with the patient requiring one bolus of vasopressin 0.5 IU intravenous.

Outcome and follow-up

Due to the incomplete occlusion of the AVF, it was elected to use a covered stent to cover the arterial side of the fistula. Because of the proximity of the left internal iliac artery, this vessel was coil embolised using 10 mm×14 cm Nester coils (Cook Medical, Bloomington, Indiana, USA). The fistula was then covered on the arterial side with a 24 mm diameter, 66 mm length, tapered (12 mm diameter distally) Zenith Cook Stent Graft Converter (ZLC-24–66) (Cook Medical) (figure 2). This successfully closed the shunt by more than 90%, and follow-up CT angiography, 3 months later, showed complete occlusion of the fistula.

Figure 2.

3D CT angiogram reconstruction of stented iliac artery and previously inserted Amplatzer.

The patient underwent this procedure 5 months from the first attempt to close the fistula. Titrated doses of fentanyl 250 mcg intravenous and midazolam 3 mg intravenous were given for sedation. A PAC was not used again in this procedure due to the risks associated with placement and the limited benefit derived from its use. The patient tolerated the procedure without anaesthetic complications. The patient did not experience postprocedural renal injury with this admission. The patient has not been seen in follow-up at our institution as she lives more than 2000 km from the hospital. It has been reported that she is improving and her functional capacity has improved.

Discussion

PH presents many conflicting anaesthetic considerations and challenges for the anaesthesiologist. One must balance anaesthesia and analgesia with hypoxia and hypercarbia while avoiding precipitating acute perioperative RV failure and haemodynamic collapse. To complicate this case, the patient had recently undergone a double lung transplant where anastomotic integrity, immunosuppression and lung function must also be considered.

The approach to any anaesthetic must consider not only the patient’s medical comorbidities, but also how these interplay with the procedure, guiding the anaesthesiologist towards the optimal type of anaesthetic. Limited evidence exists for a safety benefit for local anaesthesia and minimal sedation compared with general anaesthesia or regional anaesthesia; however, we chose this method of anaesthesia for several reasons. First, the patient would be able to maintain spontaneous ventilation with supplemental oxygen, thus avoiding hypoxia, hypercarbia and positive pressure ventilation. Being a percutaneous intravascular procedure, the intraoperative and postoperative pain is minimal and well managed with local anaesthesia. This avoids opioids and volatile anaesthesia which may exacerbate PH due to hypoventilation and decreased RV contractility. Lastly, a spinal anaesthetic is strongly relatively contraindicated in patients with severe PH with a risk of significant reduction in systemic vascular resistance and subsequent RV dysfunction. General anaesthesia places significant stress on the cardiopulmonary system. Positive pressure ventilation and positve end-expiratory pressure (PEEP) worsen pulmonary vascular resistance (PVR). Hypothermia, pain and anaesthetic agents may also worsen PVR. Overall, patients with PH are at increased risk and require vigilant management during anaesthesia.

Our patient’s PH may have been caused by the high CO AVF. High CO heart failure associated with hyperthyroidism, cardiac beriberi (ie, thiamine deficiency), severe anaemia and portosystemic shunts have also been implicated in reversible PH.^{6 7} The shear stress from increased pulmonary blood flow leads to vascular remodelling, vascular smooth muscle hypertrophy and increased PVR. The recurrence of PH post-transplant in this patient may be due, in part, to the persistent high CO state of the AVF and subsequent vascular remodelling. It is also possible that her idiopathic PH has recurred. Her PA occlusion pressure was 22/16, indicating an element of postcapillary PH, commonly seen in heart failure with preserved ejection fraction.

Iatrogenic and/or traumatic AVF have also been reported to cause new-onset PH in previously healthy patients.^8–15 In many of these patients, endovascular closure resulted in resolution of the high output cardiac failure and PH. Unfortunately, the link between the AVF and the presence of PH cannot be confirmed. The patient had preoperative echocardiographic findings suggestive of a high-flow AVF, including an IVC diameter of 4.3 cm. If this AVF were the source of the PH, she will require permanent occlusion to stop the high-flow systemic-pulmonary shunt. It is possible that the AVF is the result of the multiple vascular catheterisations the patient underwent before, during and after her transplant, including extracorporeal membrane oxygenation (ECMO), and right and left heart catheterisations.

When the AVF was first occluded with a balloon, we reported several interesting findings. Haemodynamically, the patient experienced hypertension, brief increased heart rate and a decrease in CO by nearly 45% (table 1). The increase in blood can be explained by sudden increase in afterload caused by closure of the AVF. This sudden afterload increase also explains the nuchal headache the patient complained of during the occlusion trial. The brief increase in heart rate may be due to the sudden drop in preload, and therefore stroke volume. To maintain the CO, the heart rate would need to increase. Lastly, the drop in CO may be attributed to many factors; the heart may not have been able to increase its heart rate sufficiently in light of a reduced stroke volume due to preoperative β-blockade, or the sudden increase in afterload caused cardiac dysfunction. The latter is unlikely given the lack of ECG changes, hypotension or other symptoms.

Table 1.

Haemodynamic parameters

	Pre-transplant—intraoperative (Jul 2016)	6 months follow-up (Dec 2016)	1 year follow-up (Apr 2017)	Day of 1st procedure—preocclusion (Sep 2017)	Day of 1st procedure—postocclusion (Sep 2017)
IVC (mm Hg)	*	*	*	11/8	*
RA (mm Hg)	(15)	20/20 (17)	14/14 (11)	22/18	*
RV (mm Hg)	*	64/1, 16	58/−1, 13	42/5	*
PA (mm Hg)	63/25	63/19 (37)	61/13 (32)	62/17 (33)	73/27
PAOP (mm Hg)	*	27/21 (20)	28/19 (17)	22/16	*
Ao (mm Hg)	*	90/47 (67)	105/40 (64)	*	*
LV (mm Hg)	*	97/2, 17	*	*	*
HR (bpm)	100	73	67	60	82
SV (mL)	*	131.1	*	171	117
CO (L/min)	13.7	9.83	*	10.6	5.9
CI (L/min*m2)	8.2	6.5	*	6.5†	3.6†
SVR (dyne)	*	412	*	481†	*
NIBP (mm Hg)	*	126/62 (80)	*	*	*
IBP (mm Hg)	*	*	*	118/50	160/70

†calculated. * no data available.

Ao, aortic pressure; CI, cardiac index; CO, cardiac output; HR, heart rate; IBP, invasive blood pressure; IVC, inferior vena cava; LV, left ventricle; NIBP, non-invasive blood pressure; PA, pulmonary artery; PAOP, pulmonary artery occlusion pressure; RA, right atrium; RV, right ventricle; SV, stroke volume; SVR, systemic vascular resistance.

Learning points.

• Taking into consideration the patient’s multiple comorbidities and the procedural considerations promotes a safe conduct of anaesthesia without complications.

• Pulmonary hypertension (PH) is a complex pathophysiology with the potential for catastrophic decompensation in the perioperative period.

• Avoidance of factors that worsen pulmonary vascular resistance, along with promoting coronary perfusion and preventing myocardial depression, are cornerstones in the management of patients with PH.