Ebstein's anomaly is a rare congenital cardiac disease with dysplastic tricuspid valves,
resulting in a wide spectrum of clinical manifestations, ranging from asymptomatic
state to severe congestive cardiac failure (CCF).[1] This report describes such a patient who underwent endovascular coiling of an intracranial
cerebral aneurysm under general anesthesia. Written informed consent was obtained
from the patient before writing this manuscript. A 40-year-old female patient, weighing
50 kg, presented with a history of right-sided frontal headache and left upper limb
weakness of 20 days duration. She was diagnosed to have systemic hypertension and
Ebstein's anomaly and was on treatment with calcium channel blockers, beta-blockers,
antiplatelet, and anticoagulant for the past 10 years. She had no symptoms of chest
pain, palpitations, breathlessness, cyanotic spells, or easy fatiguability during
the current visit. Diagnostic workup for her presenting symptoms included digital
subtraction angiography of the cerebral vessels that revealed a right middle cerebral
artery aneurysm measuring 5× 2.5 × 2.78 mm. Systemic examination was unremarkable
except for a low baseline peripheral arterial oxygen saturation (SpO2) of 88% at room air and pansystolic murmur of Levine grade 3 on auscultation in tricuspid
area, with no signs suggestive of CCF. Her investigations were unremarkable except
for electrocardiogram (ECG) that showed tall broad P waves in all leads. Transthoracic
echocardiogram showed severe tricuspid regurgitation (TR), dilated right atrium, and
atrialized right ventricle. Patent foramen ovale (PFO) with right to left shunt was
present with good biventricular function and pulmonary arterial systolic pressure
of 25 mm Hg.
Our anesthetic technique was tailored to ensure a preserved normal sinus rhythm with
optimal preload and afterload. Before anesthetic induction, intravenous (IV) and intra-arterial
access were secured under local anesthesia. Baseline arterial blood gas at room air
revealed normal acid– base status with oxygen partial pressure of 62.9 mm Hg. Monitoring
included ECG, invasive blood pressure, SpO2, capnography, esophageal temperature, and neuromuscular transmission. Monitoring
of regional cerebral oxygen saturation (rScO2) was done using near infra-red spectroscopy-based cerebral oximetry (Nonin Equanox
7600; Nonin Medical Inc., Plymouth, Massachusetts, United States). Sensors were placed
bilaterally on forehead, 2 cm above the eyebrow, as per the manufacturer's instructions,
ensuring that it did not interfere with image acquisition. Baseline rScO2 (at room air) were 61 and 59% on the left and right side, respectively. Preoxygenation
with 100% oxygen improved SpO2 to 92% without any change in rScO2 values. Hemodynamic stability during induction was ensured with titrated doses of
IV fentanyl up to100 μg and propofol 100 mg. Stress response to intubation was controlled
with IV lignocaine 60 mg. Vecuronium 8 mg was administered IV to facilitate tracheal
intubation. Anesthesia was maintained with oxygen: nitrous oxide mixture with a fraction
of inspired oxygen of 0.5 and sevoflurane titrated to a minimum alveolar concentration
of 0.8 to 1.0 along with intermittent boluses of vecuronium to maintain patient immobility
throughout the procedure. Patient's lungs were mechanically ventilated without positive
end expiratory pressure to maintain an end-tidal CO2 of 30 to 32 mm Hg. IV fluids were administered through a fluid warmer, titrated to
keep the systolic pressure variation (SPV) at around 10 mm Hg. A liter of crystalloid
was administered during the 3-hour-procedure. Care was taken to avoid air bubbles
in the fluid circuit to prevent paradoxical air embolism. Systemic anticoagulation
was maintained with intermittent boluses of heparin to prevent thromboembolic complications.
There were two transient episodes of peripheral arterial oxygen desaturation (SpO2 fall to 70%) with neither of these events accompanied by changes in rScO2. These episodes were transient and reverted spontaneously. rScO2 remained at 60 and 58% on the left and right side, respectively, during periods of
arterial desaturation. Our initial suspicion was pulmonary embolism with elevated
pulmonary artery pressures causing desaturation. However, airway pressures, end-tidal
CO2, and hemodynamics were within normal range and the episode was very transient lasting
a minute. Arterial blood gas analysis done at the time of SpO2 fall was also within normal limits. At the end of the procedure, patient had an optimal
recovery.
In this case report, we highlight the utility of cerebral oximetry, which is rarely
reported during the endovascular management of cerebral aneurysm in a patient with
Ebstein's anomaly.[2] Our patient had an intracardiac right to left shunt due to severe TR and PFO, which
explains the low baseline SpO2. Cyanotic spells can be triggered by events that augment right atrial pressures,
namely hypercarbia, hypoxia, hypothermia, and acidosis. We maintained normothermia
using the fluid warmer and titrated ventilation by monitoring both systemic arterial
and rScO2, end-tidal capnometry, and intermittent arterial blood gas analyses. As she was clinically
asymptomatic despite a low baseline SpO2, we used rScO2 to monitor regional oxygenation status. Interventional neuroradiological procedures
can result in cerebral embolism due to repeated flushing, further justifying monitoring
of rScO2 in this patient. As both fluid deficits and overload can compromise cardiac function
in this patient, IV fluids were titrated to maintain the SPV (the patient had sinus
rhythm and mechanically ventilated). Heparinized saline to flush the arterial sheath
was also kept to the minimum (1 L). Advanced hemodynamic monitoring (e.g., transesophageal
echocardiography, invasive cardiac output monitor) could have helped us in providing
more information on cardiac function, but nonavailability of these monitors in the
intervention suite precluded us from using these monitors. These monitors should be
preferred if one has an access to them. Nitrous oxide can aggravate the size of embolized
air and is better avoided. Due to nonavailability of medical air facility in our radiology
suite and considering the deleterious effects of prolonged 100% oxygen administration,
nitrous oxide was administered with rScO2 monitoring. Intraprocedural supraventricular and ventricular arrhythmias are frequent
in patients with Ebstein's anomaly, mandating continuation of beta-blockers as done
in this patient. Anticoagulation with heparin is usually reversed with protamine,
which was avoided in this patient for fear of an allergic reaction predisposing to
pulmonary arterial hypertension, especially in the context of elevated and high normal
right atrial and pulmonary pressures, respectively. Femoral catheter was hence removed
24 hours later after deploying the vascular closure device.
This case report emphasizes the need for understanding the pathophysiology, anticipation
of, and vigilance for potential complications during the anesthetic management of
neurointerventional procedures in patients with Ebstein's anomaly. Advanced cerebral
monitoring helps titrating the ventilatory and hemodynamic parameters during the management
of such challenging scenarios.
