Episode #71 Considerations for Blood Pressure Management

November 9, 2021

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Welcome to the next installment of the Anesthesia Patient Safety podcast hosted by Alli Bechtel.  This podcast will be an exciting journey towards improved anesthesia patient safety.

We are back to continue our discussion of the article, “Perioperative Hypotension” by Daniel Sessler from the October 2021 APSF Newsletter. Sessler is the chair of the department of outcomes research at Cleveland Clinic and we are excited for his contributions to the show today. This is a part two in our series on perioperative hypotension.

Here is the reference for the February 2020 Anesthesia and Analgesia study on The Hypotension Prediction Index:

Davies, Simon James MD*; Vistisen, Simon Tilma PhD; Jian, Zhongping PhD; Hatib, Feras PhD; Scheeren, Thomas W. L. MD, PhD§ Ability of an Arterial Waveform Analysis–Derived Hypotension Prediction Index to Predict Future Hypotensive Events in Surgical Patients, Anesthesia & Analgesia: February 2020 – Volume 130 – Issue 2 – p 352-359

Perioperative blood pressure management considerations may include the following:

  • Maintenance of MAP > 65mmHG with adjustments to anesthesia medication administration dose and timing, fluid management, and vasopressor administration
  • Postoperative monitoring and hemodynamic goals
  • Timing for restarting home antihypertensive medications to avoid hypotension in the early postoperative time period

We hope to see you in December at the 75th PostGraduate Assembly in Anesthesiology!

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© 2021, The Anesthesia Patient Safety Foundation

Hello and welcome back to the Anesthesia Patient Safety Podcast.  My name is Alli Bechtel and I am your host. Thank you for joining us for another show. We jumped into the October 2021 APSF Newsletter last week and we are picking up where we left off. Our featured article is, “Perioperative Hypotension” by Dan Sessler.

Before we dive into the episode today, we’d like to recognize Nihon Kohden America, a major corporate supporter of APSF. Nihon Kohden America has generously provided unrestricted support to further our vision that “no one shall be harmed by anesthesia care”. Thank you, Nihon Kohden America – we wouldn’t be able to do all that we do without you!”

To follow along with us, head over to APSF.org and click on the Newsletter heading. First one down is the current issue. Then, click on our featured article today, “Perioperative Hypotension.” Hypotension in the OR is a big threat to anesthesia patient safety and the risk continues even after we leave the OR and into the postoperative time period as well. Last week, we reviewed the associations with hypotension during the perioperative period including myocardial injury and ischemia, acute kidney injury, and delirium. Today, we are going to discuss considerations for blood pressure management.

During the preoperative patient assessment, there are no patient risk factors or specific surgical procedures that can reliably predict which patients will go one to develop intraoperative hypotension. Unfortunately, we still do not know the best methods to prevent and treat hypotension during anesthesia care. Studies have evaluated the relationships between intraoperative cardiac index and blood pressure as well as intravascular volume status and prevention of hypotension which did not provide the easy answer for preventing or treating perioperative hypotension.

Studies evaluating intraoperative hypotension have revealed some of the following concerns:

  • About one third of hypotensive episodes occur after induction of anesthesia and before surgical incision. This is often due to anesthetic drug effects. We cannot let our guard down after induction of anesthesia because hypotension during this time period has the same associations that we talked about last week as hypotension that occurs during the surgery.
  • How we monitor blood pressure is important for being able to detect hypotension. Continuous blood pressure monitoring with an arterial line will detect more hypotensive episodes than non-invasive blood pressure monitoring at 5-minute intervals. Sessler mentions an algorithm to predict hypotension from an arterial waveform. This is The Hypotension Prediction Index which uses the arterial pressure waveform trace to generate a unitless number and higher numbers may predict increased risk for hypotension with MAP <65mmHg for at least 1 minute, in the future. For more information about this algorithm, check out the February 2020 article by Davies and colleagues in Anesthesia and Analgesia, “Ability of an Arterial Waveform Analysis–Derived Hypotension Prediction Index to Predict Future Hypotensive Events in Surgical Patients.” I will include the reference in the show notes as well. Studies using this prediction tool have shown either less hypotension or no benefit. Further studies with larger patients and more diverse patient populations are needed going forward.
  • What medication do you reach for first to treat intraoperative hypotension? The most common medications include vasopressors such as phenylephrine or norepinephrine. In the United States, phenylephrine is the most common vasopressor used. Phenylephrine can be used to treat hypotension because it is an alpha agonist which increases the systemic vascular resistance often with a compensatory decrease in heart rate and cardiac output. Norepinephrine is a strong alpha agonist with weak beta-adrenergic agonism as well resulting in increased blood pressure with maintenance of cardiac output. Norepinephrine is the vasopressor of choice in septic shock since phenylephrine administration may lead to decreased splanchnic blood flow and decreased oxygen delivery to end-organs. At this time, there is little evidence regarding differences in outcomes for surgical patients based on the choice of vasopressor and phenylephrine and norepinephrine are often used depending on clinical preference and availability. What about the evidence for running a low-dose vasopressor infusion during the surgery and anesthesia care to prevent and treat intraoperative hypotension? Studies have not shown this practice to be harmful. Norepinephrine may be administered safely through a peripheral IV or central line. This is good news since there was concern that norepinephrine needed to be given through a central line only in the past. Check out the 2019 article in A & A, “Risk of Major Complications After Perioperative Norepinephrine Infusion Through Peripheral Intravenous Lines in a Multicenter Study” for more information. Spoiler alert: this study included over 14,000 patients and there were only 5 extravasation events and zero events of local tissue injury.

Remember, the patient’s risk for hypotension remains even after leaving the OR. Sessler tells us that hypotension on the hospital floor is common, prolonged, and profound and this may be when damage to end-organs from hypoperfusion occurs. Going forward considerations for monitoring blood pressure as well as oxygen levels more often or even continuously may be needed. Another important consideration includes the timing for holding and restarting home blood pressure medications. For example, holding angiotensin converting enzyme inhibitors and angiotensin receptor blockers on the morning of surgery may help to prevent hypotension in the OR. Restarting home antihypertensive medications after surgery needs to be done carefully in order to decrease the risk for postoperative hypotension.

Studies have revealed that intraoperative hypotension with a MAP of less than 65 mmHg occurs in over 25% of surgical patients. Patients may develop hypotension postoperatively and even severe and prolonged events may go undetected due to the long intervals between routine vital sign monitoring on the hospital wards. These postoperative events are concerning and contribute to the development of myocardial and renal injury. Have we been able to delineate between an association and causality? A small randomized trial found that prevention of intraoperative hypotension decreased the risk of major complications by 25%. Going forward, we will be able to return to the literature to evaluate the results from the POISE-3 trail and the GUARDIAN trial which may help to determine causality of these associations. So, stay tuned.

In the meantime, we need to keep in mind that intraoperative and postoperative hypotension are associated with myocardial and renal injury with some evidence for an association between hypotension and delirium as well. While we are waiting for these large trials and further evidence, we need to remain vigilant with blood pressure monitoring and treatment. It may be that we discover interventions to prevent myocardial and renal injury from perioperative hypotension in the future. For now, it appears that an appropriate intraoperative strategy may include maintenance of MAP > 65mmHG with adjustments to anesthesia medication administration dose and timing, fluid management, and vasopressor administration. Once we leave the OR, the challenge continues due to monitoring ability. Keep in mind that patients may benefit from delaying restarting home antihypertensive medications in the early postoperative time period when they remain at risk for hypotension and the associated myocardial and renal injury. Sessler leaves us with a call to action that I am going to read now:

“Blood pressure—specifically hypotension prevention—is a modifiable factor that may reduce cardiovascular complications. Pending the results of robust trials, reasonable efforts to avoid perioperative hypotension seem prudent.”

To wrap up the show, we are going to hear from the author of our featured article, Sessler, once again. I asked him what he hopes to see going forward related to perioperative hypotension and anesthesia patient safety. He provides some insight and advice.

[Sessler] “There’s clear evidence that hypotension is associated with myocardial injury, kidney injury, and death. The extent to which this association is causal remains largely unknown at this point. We very much need large robust randomized trials. Fortunately, these are in progress and the results should be available relatively  soon. But in the meantime, clinicians would be well guided to keep mean arterial pressure above 65 mmHg during surgery and preferably above 75 mmHg postoperatively.”

[Bechtel] Thank you so much to Sessler for contributing to the show today and we are looking forward to learning more about this area from the ongoing studies in the future. This is also an excellent call to action to monitor mean arterial blood pressure closely during and after anesthesia care while setting appropriate hemodynamic goals to help keep patients safe.

If you have any questions or comments from today’s show, please email us at [email protected].

Visit APSF.org for detailed information and check out the show notes for links to all the topics we discussed today. Please keep in mind that the information in this show is provided for informational purposes only and does not constitute medical or legal advice. Do you have plans for December? The APSF sure does and we hope to see you at the 75th Postgraduate Assembly in Anesthesiology from December 10-13th in New York City. I will include a link to the meeting in our show notes as well. If you have not seen the APSF panel on Clinician Safety: To Care is Human yet, here is your chance. Come learn all about Clinician Wellbeing as a Patient safety Issue, Incivility, Rudeness, and Violence in the Perioperative Work Environment, Perioperative Clinicians Mental Health, and Strategies for Improving Perioperative Clinician Wellbeing and Addressing Burnout! This is a session you do not want to miss!

Until next time, stay vigilant so that no one shall be harmed by anesthesia care.

© 2021, The Anesthesia Patient Safety Foundation