Rare artifacts mimicking sinus tachycardia in a case of vaginal hysterectomy with situs inversus totalis.

Sir,

The introduction of modern monitoring gadgets based on ever improving technology has made the life of the anesthesiologist and intensivist fairly easy and comfortable. But the rare pitfalls and shortcomings due to the inherent electronic limitations of these monitors can sometimes prove hazardous in the interpretation of the various vital parameters.[1] The most commonly observed artifacts are of electrocardiogram (ECG) interpretation which can exhibit any type of arrhythmia or ST-T wave changes and the source of these artifacts can be internal (physiological) or external (non-physiological).[2-4] The interpretation can be so difficult sometimes that even an experienced anesthesiologist has to apply all his clinical knowledge and acumen to correctly identify the type of artifact as happened in the present case.[5]

A 49-year-old postmenopausal female with an established diagnosis of third-degree uterine prolapse and situsinversuswas posted for trans-abdominal hysterectomy and was administered epidural anesthesia with 17 ml of 0.75% ropivacaine and 60 μg of dexmedetomidine. Surgery was initiated after complete establishment of sensory block up to T-5 level. In the midst of the surgical procedure, the heart rate of the patient decreased to 46/ min. Simultaneously, the non-invasive blood pressure (BP) measured was 130/88 mmHg and we administered 0.3 mg of atropine as a prophylactic measure to rectify the bradycardia. We suddenly observed a display of sinus tachycardia on the monitor's ECG waveform which correlated well with the pulse oximetry waveform (SpO2) but not with the digital readings [Figure 1]. As the patient had situsinversus with dextrocardia, we got concerned about all the potential cardiac complications. Both the peripheral pulses and heart rate correlated with the digital readings of the monitor and the patient was asymptomatic. Thereafter, on careful analysis of the parameters on the monitor once again, we observed a slightly slower sweep cycle of the waveform of both ECG and SpO2 as the waveform speed was changed automatically from 25 ms to 12.5 ms [Figure 2]. Most probably this must have occurred when we pressed the blood pressure knob to measure the stat BP. After this initial rectification, the artifact waveform could not be reproduced on repeated attempts and the entire surgical period remained uneventful.

Figure 1

The false picture of sinus tachycardia on the ECG and SpO2 waveform not correlating with the digital reading

Figure 2

The real corrected ECG and SpO2 waveform matching with the digital reading

The electronic devices for continuous monitoring are liable to get damaged by the moisture, dust, fluctuation of the voltages, indiscriminate use and irregular servicing which can alter the values of the parameters and put the patient at risk of unwanted and unnecessary interventions. Though these monitors become available for safe use after passing so many astringent industrial tests such incidents are liable to push the naive anesthesiologist and the intensivist to press the panic button.[67] These therapeutic interventions can unnecessarily enhance the risks for developing complications, especially in patients suffering from various other pre-op co-morbidities.[2]

Situs inversus totalis and dextrocardia can be associated with congenital cardiac lesions such as ventricular septal defect, atrial septal defect, pulmonary stenosis, tetralogy of Fallot, tricuspid atresia and single ventricle, which can have various anesthetic implications. The risks of developing arrhythmias and cardiovascular complications are quite high in this subset of patients as compared to the general population.[8-10]

In the literature there are numerous reported artifacts during monitoring, resulting from offset potential, poor polarization, amplitude variations, differences in the impedance, stray currents through cables, voltage fluctuations and filtering defects in the monitor, frequency mismatching of the various devices, and so on.[211-13] The artifacts we encountered occurred solely due to some electronic snag in the monitor which must have been activated during the pressing of the blood pressure knob. Later on, it was found that the monitor was due for service since seven months and was withdrawn from the operation theatre and a complete check-up was done the next day by the engineer along with the servicing Till now, we had not faced any such problem in any of the operation theatres and intensive care unit and a team of biomedical engineer and a senior anesthesia technician has now been assigned the responsibility of getting the service done for all the electronic gadgets at least 15-30 days earlier than the recommended date.

To conclude, it is recommended that the anesthesiologist and the intensivist should always rely on their personal experience, knowledge and clinical acumen to counter any real or pseudo complications. They should make use of all their vital senses which can make them alert and vigilant in the operation theatre and intensive care unit to deal with any potential complication instead of relying solely on the electronic monitoring gadgets. The age-old proverb stands so true even in the modern electronic times i.e. ‘Treat the patient and not the monitor’.