New-Onset Atrial Fibrillation Detected by Continuous Capnography Monitoring: A Case Report

Background

Patients with obstructive sleep apnea (OSA) experience intermittent episodes of nocturnal hypoxemia secondary to obstructive apneic events, leading to increased sympathetic activation that may contribute to the development of atrial fibrillation (AF) [1]. Surgical patients with underlying OSA have been found to be at increased risk of postoperative atrial fibrillation (POAF) following both cardiac and noncardiac surgery [2,3]. POAF complicating noncardiac surgery is associated with increased morbidity, mortality, and hospital costs [4–6].

A “failure to rescue” event leading to major morbidity or mortality is an event that could have been prevented intervening early when a patient has decompensation. In the United States, acute respiratory compromise events are common, frequently occur on standard wards, and have a mortality rate of approximately 40% [7]. Implementation of continuous monitoring of respiratory effort in patients hospitalized in these low-acuity settings has been advocated as a strategy to provide early recognition of decompensation, thus allowing timely intervention before a critical event [8].

One monitor that can be used for continuous cardiopulmonary monitoring in low-acuity settings is the Capnostream™ portable bedside monitor (Medtronic, Dublin, Ireland). The Capnostream™ comprehensively assesses patient oxygenation and ventilation by continuously measuring end-tidal carbon dioxide (etCO2) and respiratory rate (RR) using Microstream™ capnography, and heart rate (HR) and oxyhemoglobin saturation (SpO2) using Nellcor™ pulse oximetry (Figure 1) [9,10].

The PRediction of Opioid-induced respiratory Depression In patients monitored by capnoGraphY (PRODIGY) trial was a multicenter, prospective, observational study designed to develop a risk prediction score for respiratory depression on the ward (ClinicalTrials.gov Identifier: NCT02811302) [9,10]. Per study protocol, medical and surgical patients admitted to standard hospital wards who were receiving parenteral opioids underwent both routine clinical monitoring (intermittent vital sign spot checks) and blinded, continuous, electronic, cardiorespiratory monitoring for a maximum of 48 hours to detect episodes of opioid-induced respiratory depression (OIRD) [9,10]. Members of the PRODIGY Clinical Event Committee reviewed and adjudicated signals from the Capnostream™ portable bedside monitor that were consistent with respiratory depression. Additional medical history for the cases described was provided by the study sites. Study data analysis revealed 2 cases of etCO2 signal pattern consistent with obstructive breathing pattern. Initially, the HR was stable in both patients and abruptly changed to a highly variable, rapid rate consistent with atrial fibrillation with rapid ventricular response.

Case Reports

CASE 1:

The patient was a 75-year-old man with a body mass index (BMI) of 26.9 kg/m2 and a medical history significant for hypertension, cerebral infarction, and pulmonary artery and deep vein thromboses. His risk for OSA was determined to be high with a preoperative STOP-BANG (Snoring, Tired, Observed, Pressure, BMI, Age, Neck size large, Gender) score of 6. His pre-operative electrocardiogram showed normal sinus rhythm and he denied a history of dysrhythmias. The patient underwent abdominoperineal resection with a laparoscopic approach for colorectal cancer with general anesthesia supplemented by epidural analgesia. His immediate perioperative course was un-remarkable and the Capnostream™ portable bedside monitor was used. On the patient’s second postoperative day, multiple apneic events were detected by the monitor. During this time, the patient’s HR abruptly increased from the 80 to 90 beats per minute (bpm) range to a variable rate of 100 to 150 bpm (Figure 2A). This pattern continued for approximately 5 hours and then spontaneously resolved (Figure 2A, 2B). This episode occurred while the patient was in a postoperative ward, and was not detected by routine clinical monitoring (intermittent vital sign spot checks), and therefore, not treated. There were no consequences from the POAF episode.

CASE 2:

The patient was a 72-year-old man with a BMI of 24.0 kg/m2 and a history of hypertension. His risk for OSA was determined to be intermediate, based on a preoperative STOP-BANG score of 3. His preoperative electrocardiogram showed sinus brady-cardia and he denied a history of dysrhythmia. The patient underwent a partial hepatic resection under general anesthesia to treat a recurrence of colorectal cancer that had metastasized to the liver. His immediate postoperative course was unremarkable and he was transferred to the floor, where the Capnostream™ portable bedside monitor was used. Approximately 9.5 hours after surgery, multiple apneic events were detected by the Capnostream™ monitor (Figure 3). During this time, the patient’s HR increased from 60 to 90 bpm over a 5-minute period, and then increased to a variable rate between 120 and 180 bpm. This episode was not detected by routine clinical monitoring (intermittent vital sign spot checks), and therefore, was not treated. There were no consequences from the POAF episode.

Discussion

We described the cases of 2 men who developed a HR and rhythm consistent with POAF with rapid ventricular response in the setting of obstructive breathing patterns. In both cases, the dysrhythmia was asymptomatic and not detected by routine clinical monitoring. The HR variability consistent with AF was detected retrospectively on the capnography tracing that was made when these patients were on the hospital ward. The Capnostream™ portable bedside monitor was designed to continuously monitor for signs of respiratory depression [9,10]. The limitation of these 2 cases is that POAF was never diagnosed with electrocardiography. Because of the PRODIGY trial protocol, continuous cardiorespiratory monitoring was blinded in these cases. In a normal clinical environment, however, Capnostream™ portable bedside monitor is unblinded, which may enable prevention of complications associated with POAF, through early detection and appropriate medical intervention, including administration of oral anticoagulation medication.

Undetected postoperative OIRD can lead to respiratory arrest associated with increased morbidity and mortality, and has been reported to develop in patients soon after their vital signs have been found to be reassuring [11]. Intermittent assessment of vital signs in hospitalized patients who are receiving parenteral opioids is considered to have low-to-moderate sensitivity and specificity for detection of episodes of OIRD [12]. Therefore, patient safety advocacy groups are calling for continuous multimodal monitoring of respiratory status in hospitalized patients [11].

Our 2 cases illustrate the limitations of intermittent monitoring of vital signs for detection of other pathophysiologic abnormalities, such as POAF, which may result in hemodynamic instability, stroke, and other serious outcomes. As more centers adopt continuous monitoring for all hospitalized patients, the detection of these events will undoubtedly increase.

Conclusions

Recent scientific evidence suggests that capnography is a reliable method for identifying respiratory distress in surgical patients when compared with standard pulse oximetry [13]. In our case reports, respiratory distress was accompanied by episodes of cardiac dysrhythmia, which were otherwise undetected by standard monitoring of vital signs. Fortunately, in both patients, the events were self-limited. However, these events illustrate how use of continuous monitoring devices in low-acuity areas can alert health care providers to deteriorating cardio-pulmonary function, which could allow time for early intervention and mitigate the risk of patient morbidity and mortality.