To the Editor:
We read with great interest the intriguing study by Mathis et al.1 involving 702 noncardiac procedures performed in patients with left ventricular assist devices (LVADs). We commend the authors for their work in this important area and share their passion and enthusiasm for caring for LVAD patients perioperatively.
Mathis et al. reported that arterial line blood pressure (BP) was utilized in 20% of cases, with the remaining relying on noninvasive BP monitoring modalities. Interestingly, they report that 55% of all anesthetics had a greater than 20-min gap intraoperatively without a documented BP reading. Even more alarming is that 48% of their anesthetics had BP monitoring for less than 20% of minutes intraoperatively, and 31 cases lacked any BP recordings entirely. Further, in cases where an arterial line was employed, they report a monitoring gap of greater than 20 min in 32% of anesthetics occurring primarily between induction of anesthesia and arterial line placement. It is not reported in the manuscript whether the placement of arterial access was necessitated by the inability to obtain noninvasive BP readings or whether it was anticipated based upon patient and/or surgical factors. Mathis et al. stated that when BP was not recorded, “measures approximating vital organ perfusion were documented, including patient responsiveness (e.g., patient following commands, patient alert, etc.) in 11 cases and/or serial documentation of stable LVAD parameters (i.e., flow, power, and pulsatility index) in 29 cases.”
We previously reported that arterial line BP monitoring was used in 66% of LVAD patients undergoing general anesthesia for noncardiac surgery at our institution.2 In LVAD patients undergoing exclusively gastrointestinal endoscopy principally without general anesthesia, we reported arterial line use in only 10% of procedures.3 In 6% of these anesthetics, the BP was not charted or documented as inaccurate.
The American Society of Anesthesiologists Standards for Basic Anesthetic Monitoring state “every patient receiving anesthesia shall have arterial BP and heart rate determined and evaluated at least every five minutes,” with exceptions permitted “under extenuating circumstances.”4 Continuous-flow LVAD patients present many perioperative challenges including BP monitoring. One study evaluated various noninvasive BP modalities in continuous-flow LVAD patients and found that the success rate of obtaining a BP reading with an automated BP cuff was 53%, Doppler BP 94%, auscultation 14%, and palpation 3%.5 In our experience, although noninvasive BP determination (particularly with automated cuffs) may be initially possible in LVAD patients, preload and afterload can change markedly and rapidly intraoperatively. These fluctuations may result in a significant decrease in pulsatility with subsequent loss of reliable and accurate noninvasive BP readings. For this reason, we strongly believe that if noninvasive BP determination (especially an automated BP cuff) is utilized, then a more reliable modality to determine BP should be immediately available in the anesthetizing location such as Doppler BP or the ability to expeditiously place invasive arterial line BP monitoring. In teaching institutions such as ours, this often entails educational efforts in modalities such as Doppler BP determination and the limitations of automated BP cuffs that may be unfamiliar to the wide variety of noncardiac anesthesia providers who help care for LVAD patients perioperatively. When use of invasive arterial BP monitoring is planned intraoperatively, consideration should be made for placement before induction of anesthesia to avoid monitoring gaps postinduction should noninvasive BP determination attempts become unsuccessful. In cases where the functionality of noninvasive BP modalities was confirmed before induction of anesthesia, the inability to determine BP intraoperatively should prompt clinicians to rapidly employ a different modality that ensures reliable BP determination so that large gaps devoid of BP readings do not occur during an anesthetic. Finally, given the frequent difficulty reported by Mathis et al. in determining BP intraoperatively in the majority of anesthetics, perhaps unrecognized and untreated hypotension could have also contributed to the primary outcome of acute kidney injury.
The authors declare no competing interests.