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Correspondence  |   November 2017
In Reply
Author Notes
  • University of Michigan Health System, University of Michigan, Ann Arbor, Michigan (M.R.M.). mathism@med.umich.edu
  • (Accepted for publication July 28, 2017.)
    (Accepted for publication July 28, 2017.)×
Article Information
Correspondence
Correspondence   |   November 2017
In Reply
Anesthesiology 11 2017, Vol.127, 903-904. doi:10.1097/ALN.0000000000001854
Anesthesiology 11 2017, Vol.127, 903-904. doi:10.1097/ALN.0000000000001854
We thank Drs. Barbara and Freundlich et al. for their thoughtful responses to our recent article.1  In their responses, they highlight critical points regarding the management of patients with left ventricular assist devices (LVADs) presenting for noncardiac surgery. These points include: (1) LVAD patients are at high risk for perioperative complications; (2) frequency of invasive arterial line monitoring continues to decrease, despite high rates of intraoperative monitoring gaps; (3) potential hemodynamic instability in the setting of inadequate blood pressure monitoring may lead to increased incidence of complications (including acute kidney injury); and, as such, (4) alternatives to automated noninvasive cuff measurements for blood pressure monitoring must be more aggressively pursued.
We agree with Drs. Barbara and Freundlich that the LVAD population is, by definition, high risk and that a decreasing frequency of arterial line monitoring observed over our study period is not justified by the high rate of blood pressure monitoring gaps also observed. We support arterial line placement for major procedures requiring general anesthesia in this population; however, we highlight alternatives to routine arterial line use for minor procedures with sedation, as alluded to in Dr. Barbara’s and Dr. Freundlich’s responses.
With the increased prevalence of LVAD patients presenting for noncardiac procedures, rapidly growing demands are placed on limited anesthesiology department resources. Arterial line placement can occasionally be a technically challenging, time-consuming task in the LVAD patient, often requiring ultrasound guidance in the setting of nearly nonpulsatile blood flow. While we do not discourage such attempts, we strongly encourage anesthesiologists to seek access to—and develop a familiarity with—other means of blood pressure monitoring, most notably a Doppler cuff. In the LVAD population, Doppler measurements demonstrate success rates of 91 to 100%, a vast improvement upon automated cuff measurements (50 to 63%).2–4  As a result of these findings, we have developed a staff education program at our institution to improve departmental awareness and access to Doppler devices for the specific purpose of LVAD patient monitoring; we support efforts to do the same among institutions caring for LVAD patients.
With regards to the context of arterial line usage and monitoring gaps observed, we acknowledge limitations of the retrospective nature of our study. Anesthesiologist justification for arterial line use, whether planned or unplanned, was unavailable for study. In most instances of gaps in monitoring, gaps occurred after induction of anesthesia; in such cases, we can speculate that the monitoring gap may have been associated with an automated cuff failure in the setting of decreased preload or afterload and diminished pulsatility. Beyond seeking a means of improved blood pressure monitoring, it has been our experience in caring for LVAD patients that efforts to maintain pulsatility—including judicious fluid boluses and vasopressor administration concurrent with gentle induction of anesthesia—can often successfully maintain automated cuff monitoring capability and prevent unrecognized hypotension.
In addition to a familiarity with blood pressure monitoring in the LVAD population, we encourage all anesthesiologists to become familiar with basic settings for continuous-flow LVADs, including pump flow, speed, power, and pulsatility index.5  Although we describe an association between intraoperative hypotension and acute kidney injury in our study, a correlation between LVAD pump flows and outcomes remains understudied. Pump flow generated by a specific pump speed may be a sensitive indicator of the balance between preload and afterload and may be a useful aid in patient management. Finally, no hemodynamic parameters monitored should serve to replace an understanding of the pathophysiology of the preload-dependent, afterload-sensitive LVAD patient; such an understanding remains equally important in clinical decision making.
In conclusion, we thank Drs. Barbara and Freundlich et al. for their valuable feedback regarding our study. Although the optimal means for hemodynamic monitoring in the LVAD patient is yet to be fully elucidated, it is clear that this population poses a challenge to American Society of Anesthesiologists Standards for Basic Anesthetic Monitoring.6  Given the potential for increased postoperative complications with inadequate monitoring, our study represents a call to action for consensus guidelines addressing anesthetic monitoring specific to this increasingly common, high-risk population.
Research Support
All work and partial funding attributed to the Department of Anesthesiology, University of Michigan Medical School, Ann Arbor, Michigan. The project described was supported in part by grant No. 5T32GM103730-03 from the National Institute of General Medicine Sciences, Bethesda, Maryland. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. Industry contributors have had no role in the study.
Competing Interests
The authors declare no competing interests. The University of Michigan performs contract research with St. Jude, Pleasanton, California, and HeartWare, Framingham, Massachusetts.
Michael R. Mathis, M.D., Subramanian Sathishkumar, M.B.B.S., Milo C. Engoren, M.D. University of Michigan Health System, University of Michigan, Ann Arbor, Michigan (M.R.M.). mathism@med.umich.edu
References
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American Society of Anesthesiologists: American Society of Anesthesiologists Standards for Basic Anesthetic Monitoring. 2015. Available at: http://www.asahq.org/sitecore/shell/~/media/sites/asahq/files/public/resources/publications/epubs/standards-for-basic-anesthetic-monitoring-epub.epub. Accessed June 30, 2017