Apnea Management During WATCHMAN Device Deployment with Apneic Oxygenation: A Case Report of Three Cases

ABSTRACT

WATCHMAN is a percutaneous left atrial appendage closure device that is implanted in patients who are unsuitable for anticoagulation therapy for atrial fibrillation. During WATCHMAN implantation, inducing apnea in the patient is preferable to allow stable deployment. We present three cases in which apneic oxygenation was employed to maintain oxygenation during apnea, and oxygen reserve index (ORi™) was measured to evaluate its safety and efficacy. Oxygen was administered continuously via the endotracheal tube during apnea. During all four apneic events in three patients (mean duration of 356 seconds), the ORi values maintained above 0.24, which is generally considered the threshold of partial pressure of arterial oxygen (PaO₂) > 100 mmHg. Transcutaneous oxygen saturation and PaO₂ remained above 99% and 300 mmHg, respectively. There were no respiratory or circulatory complications during or after the surgery.

INTRODUCTION

During WATCHMAN left atrial appendage closure device (Boston Scientific, Marlborough, MA) implantation, inducing apnea in the patient is preferable for allowing stable deployment.[1] The anesthesiologist may be asked to put the patient on apnea for several minutes, which can induce hypoxemia and requires careful attention. However, there have been no previous reports on the anesthetic management of apnea associated with WATCHMAN implantation. Apneic oxygenation is a method of maintaining oxygenation during apnea, which is achieved through preoxygenation with 100% oxygen followed by continuous supplementation of oxygenation to the upper airway.[2] In this report, we present three cases in which apneic oxygenation by supplementation of oxygen into the endotracheal tubes was utilized during apnea and oxygen reserve index (ORi™) was measured to evaluate its safety and efficacy. Written consent for case reporting was obtained from all patients.

CASE HISTORY

Case 1

A 79-year-old woman with chronic atrial fibrillation, who presented anemia caused by suspected gastrointestinal bleeding, underwent WATCHMAN implantation. Despite her mildly high body mass index of 31 kg/m² (height of 150 cm and body weight of 70 kg), she had no major problems with cardiac or respiratory function.

Before induction of general anesthesia, a sensor was placed on the fingertip to initiate the measurement of ORi and transcutaneous oxygen saturation (SpO₂) using Radical-7 Pulse CO-Oximeter^® version 1630i (Masimo Corp., Irvine, CA). After general anesthesia was induced, the trachea was intubated, an arterial pressure catheter was inserted into the radial artery, and a transesophageal echocardiography (TEE) probe was placed. Anesthesia was maintained with sevoflurane, remifentanil, and rocuronium. Pure oxygen was administered for 10 min, and ventilation was discontinued during device deployment at the surgeon’s request. Oxygen (6 L/min) was continuously administered via the endotracheal tube during apnea. The apnea lasted 310 s, during which ORi decreased from 0.69 to 0.43 [Figure 1].

Figure 1.

ORi trends during apnea for WATCHMAN device deployment. In all cases, ORi decreased gradually during apnea ORi: Oxygen reserve index

Case 2

A 67-year-old man with a history of percutaneous coronary intervention due to myocardial infarction developed atrial fibrillation and underwent WATCHMAN implantation due to gastrointestinal bleeding. He had no respiratory problems.

General anesthesia was administered as in Case 1. Following the administration of pure oxygen for 3 minutes, ventilation was discontinued during device deployment. Oxygen (6 L/min) was continuously administered via the endotracheal tube during apnea. The apnea lasted for 280 s, during which the ORi decreased slightly from 0.33 to 0.28 [Figure 1].

Case 3

A 73-year-old man with a history of cardiogenic stroke caused by atrial fibrillation underwent WATCHMAN implantation due to bleeding from a colonic diverticulum. He had no significant cardiac disease other than atrial fibrillation. He was a current smoker of 20 cigarettes per day, and his respiratory function was moderately impaired.

General anesthesia was induced as in cases 1 and 2. After pure oxygen was administered for 9 min, ventilation was discontinued during device deployment. Oxygen (6 L/min) was continuously administered via the endotracheal tube during apnea. The apnea lasted 390 s, during which the ORi decreased from 0.94 to 0.66 [Figure 1]. Following the initial implantation of the WATCHMAN, the TEE evaluation determined that the size of the device was inadequate, and we decided to implant a larger WATCHMAN device. During the second implantation, the patient was administered 6 min of pure oxygen, and 445 s of ventilatory cessation was applied. Oxygen was administered continuously at 3 L/min during apnea via the endotracheal tube, during which the ORi decreased from 0.87 to 0.62 [Figure 1].

In each case, blood gas analysis was performed before and after apnea [Table 1]. In all cases, the patient’s SpO₂ and partial pressure of arterial oxygen (PaO₂) remained above 99% and 300 mmHg, respectively, during anesthesia, and there were no respiratory or circulatory complications during or after surgery.

Table 1.

Results of ORi and blood gas analysis before and after apnea

	ORi	PaO2 (mmHg)	PaCO2 (mmHg)	pH
Case 1
Pre-apnea	0.69	433	37.7	7.418
Post-apnea	0.43	333	49.4	7.321
Case 2
Pre-apnea	0.33	310	35.1	7.417
Post-apnea	0.28	303	55.7	7.264
Case 3-1
Pre-apnea	0.94	443	48.5	7.277
Post-apnea	0.66	361	65.5	7.182
Case 3-2
Pre-apnea	0.87	NA	NA	NA
Post-apnea	0.62	324	65.0	7.183

ORi: Oxygen reserve index

DISCUSSION

In these three cases, we induced apnea in patients for several minutes in order to facilitate stable WATCHMAN implantation at the request of the surgeon. Although apnea for several minutes can induce hypoxemia in patients and requires appropriate management and monitoring, there are no reports on the anesthetic management of apnea associated with WATCHMAN implantation. We employed apneic oxygenation method to maintain oxygenation during apnea and measured ORi to evaluate its efficacy.

WATCHMAN is a percutaneous left atrial appendage occlusion device that is performed in patients who are unsuitable for anticoagulation therapy for atrial fibrillation and is expected to be as effective in stroke prevention as that of anticoagulation with warfarin.[3] Fluoroscopy and TEE are important to confirm the location of WATCHMAN implantation, which is typically performed under general anesthesia.[4] When performed under general anesthesia, inducing apnea in the patient is preferable to allow for stable device deployment,[1] and anesthesiologists need to safely manage apnea for several minutes in patients with cardiopulmonary diseases.

Apneic oxygenation is a technique used to maintain oxygenation in apneic patients. This technique is achieved through preoxygenation with 100% oxygen followed by continuous supplementation of oxygen to the upper airway. Gas transfer occurs as a result of the negative pressure caused by the difference in the amount of oxygen released from the alveoli and the amount of carbon dioxide entering the alveoli.[2] It was previously reported that, in eight healthy individuals, apneic oxygenation during intubation maintained sufficient SpO₂ for 18 to 55 min.[5] Apneic oxygenation utilizing high-flow nasal cannulas or catheters inserted into the trachea has been reported to be clinically useful in patients who are expected to have difficulty airway management and in patients who require apnea for endoscopy.[6,7] However, it has been reported that some patients do not maintain oxygenation even with apneic oxygenation, and obesity and low functional residual capacity are considered risk factors.[7,8]

ORi is a noninvasive and continuous parameter that can be measured by connecting a multi-wavelength sensor attached to the fingertip to Radical-7 Pulse CO-Oximeter^®. It is an index measured using a non-unit scale between 0.00 and 1.00, which reflects the range of moderate hyperoxia. Specifically, ORi and PaO₂ are positively correlated when PaO₂ < 240 mmHg, with ORi nearly always indicating 0.00 when PaO₂ < 100 mmHg and a value of approximately 0.60 when PaO₂ is 200 mmHg, though individual differences exist. It has also been reported that almost certainly PaO₂ > 100 mmHg when ORi > 0.24.[9] Monitoring ORi trends can predict impending desaturation approximately 30 seconds before noticeable changes in SpO₂ occur, which is valuable in predicting hypoxemia during apnea.[10]

In these three cases, including patients with obesity or impaired respiratory function, ORi was continuously monitored during apnea and remained >0.24, the cut-off value for PaO₂ > 100 mmHg, while the index gradually decreased, suggesting that the patients had adequate oxygen reserves. If ORi had dropped rapidly below 0.24, we would have assessed that apneic oxygenation was not working properly and could have decided to resume ventilation before SpO₂ dropped. This is a major advantage of monitoring ORi during apneic oxygenation. It has been reported that apneic oxygen can induce respiratory acidosis and consequent arrhythmias due to little clearance of carbon dioxide. In these three cases, PaO₂ remained high, whereas PaCO2 increased by 10 to 20 mmHg within approximately 5 minutes of apnea. However, the rate of rise of carbon dioxide levels is reported between 2.6 and 3.4 mmHg per minute, suggesting that apneas of 10 minutes or less will not have a significant adverse effect.[6]

In conclusion, the present cases indicate that apneas required during WATCHMAN device deployment can be safely performed with apneic oxygenation and that its effectiveness can be confirmed through ORi monitoring.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.