AANA Resource
  • Intraoperative Hypotension, Killing Them Softly: Avoiding iatrogenic harm by managing hemodynamics appropriately

    Author(s): By Amy Yerdon, DNP, CRNA and Desiree Chappell, MSNA, CRNA, FAANA

     

    This article is sponsored and was provided to AANA by Edwards Lifesciences and is not peer-reviewed. Content has been reviewed by AANA editorial staff.

    Intraoperative hypotension (IOH) is a common occurrence with reported rates of greater than 80% of non-cardiac surgery patients.1-3 Centers for Medicare and Medicaid Services define IOH as a mean arterial pressure (MAP) <65 mm Hg for greater than 15 minutes for the Merit Based Incentive Program but definitions in the literature vary specifically around the amount of time spent in hypotension.4 In many studies, even one minute of IOH is associated with acute kidney injury (AKI), myocardial injury, stroke, and mortality. 1, 5-10 The risk of organ dysfunction and poor outcomes is greater with longer duration of MAP < 65 mm Hg or for any time period below 55 mm Hg.5-7, 9-10 In today’s high production anesthesia practices, clinicians may not realize the impact of IOH on patient outcomes.

    Considering a prolonged duration of MAP < 65 mm Hg or any time below 55 mm Hg is associated with increased risks of patient morbidity and mortality, anesthesia providers should minimize the occurrence, severity, and duration of IOH.7 Recent studies have shown a reduction of IOH with the use of continuousarterial blood pressure (CABP) monitoring compared to intermittent oscillometric blood pressure (IOBP) monitoring.11-14 Issues with traditional IOBP monitoring include overestimation of the MAP when BP values are low, allowing for longer duration of IOH, as well as the failure to provide an adequate frequency of measurements to detect IOH.11 In the AWAKE trial, Kouz and colleagues,11 performed a randomized trial comparing CABP versus IOBP monitoring and hypotension during induction of anesthesia in noncardiac surgery patients. They found a 67% reduction in the area under a MAP of 65 mm Hg (calculated as depth of hypotension multiplied by duration of hypotension) in the patient group with CABP monitoring initiated prior to induction compared to the IOBP monitoring group. They concluded CABP monitoring reduced the severity and duration of IOH, and recommended clinicians insert the arterial catheter prior to induction in patients for whom intra-arterial pressure monitoring was already planned.

    Other studies, including the DETECT trial, compared continuous non-invasive finger-cuff blood pressure (NIABP) monitoring with IOBP monitoring.12-14 Results of these studies showed statistically significant reductions in the occurrence of IOH throughout the anesthetic,12,14 reduction in IOH during anesthetic induction,13 and shorter duration and decreased severity of IOH 12-14 with NIABP monitoring. Authors of these studies recommend anesthesia clinicians consider using continuous NIABP monitoring to reduce IOH and its associated patient complications.

    Inappropriate treatment of  IOH may be associated with harm

    A five-year retrospective observational study by the Multicenter Perioperative Outcomes Group (MPOG), observed the prevalence of IOH and rates of AKI in patients undergoing major abdominal surgery.15 The authors noted a decrease in fluids administered, increase in the amount of vasopressors used, and increased incidence of AKI despite a reduction in IOH. In addition, they reported an increase of crystalloid administration from 1 to 10 ml kg-1 h-1 was associated with a 58% decreased risk of AKI.15  A possible explanation for higher rates of AKI in the normotensive group could be the restrictive approach to fluid management that has been rooted in many Enhanced Recovery After Surgery (ERAS) protocols, fluid management strategies, surgeon requests, and the use of vasopressors.15 When vasopressors are given to a hypovolemic patient, splanchnic and renal blood flow can be compromised and cause organ injury (e.g., AKI).17

    AKI places a large burden on the healthcare system. It may lead to other complications such as chronic kidney disease, myocardial injury, stroke, and death. It is also associated with an increased length of stay (LOS) by three days, increased healthcare costs, and utilization of resources.1,16 In a recent study, French and colleagues18 found that all stages of postoperative AKI were associated with increased LOS, surgical hospitalization costs, in-hospital mortality, and 1-year mortality. These findings suggest that patients with even a low-grade or stage 1 AKI are at higher risk for short- and long-term complications.18 This indicates that even a slight bump in creatinine in the immediate postoperative period, possibly due to mismanagement of hypotension, can result in iatrogenic harm. Table 1 includes the definitions and stages of AKI.

    Table 1. Stages of AKI* Severity per Kidney Disease: Improving Global Outcomes (KDIGO) Guidelines19

    Stage of AKI* Serum Creatinine (SCr) Urine Output
    1

     

    1.5–1.9 times baseline

    OR 0.3 mg/dl increase

     

    < 0.5 mL/kg/h for 6-12 hours
    2

     

    2.0–2.9 times baseline

     

     

    < 0.5 mL/kg/h for ≥ 12 hours
    3 3.0 times baseline OR Increase in serum creatinine to 4.0 mg/dl

    OR

    Initiation of renal replacement therapy

    < 0.3 mL/kg/h for ≥ 24 hours

    OR

    Anuria for ≥ 12 hours

    *AKI is defined as any of the following:

    • Increase in SCr by ≥ 0.3 mg/dl within 48 hours; or
    • Increase in SCr to ≥ 1.5 times baseline, which is known or presumed to have occurred within the prior 7 days; or
    • Urine volume < 0.5 ml/kg/h for 6 hours.

    Managing hemodynamics appropriately

    Titrating fluids and vasoactive medications to achieve specific endpoints in a goal-directed hemodynamic therapy (GDHT) approach is a promising strategy for reducing postoperative complications and death.17 Facilities performing moderate to high-risk surgeries and caring for surgical patients with comorbidities are most likely to see the benefit of implementing GDHT strategies.20-21 Utilizing advanced hemodynamic monitoring including cardiac output and stroke volume (SV) during the intraoperative period allows for optimal dosing and timing of fluids, inotropes, and vasopressors.22 Monitoring SV for an increase in response to fluid bolus, indicating fluid responsiveness, is the safest and most effective strategy for fluid management.17 Calvo-Vecino and colleagues22 studied the utilization of a cardiac output monitor and algorithm for determining interventions to optimize intraoperative hemodynamics in the landmark FEDORA trial, which showed significant reductions in postoperative complications. Yet much variability remains in intraoperative hemodynamic monitoring in clinical practice.22

    A substantial body of literature exists supporting the intraoperative use of GDHT to optimize patient hemodynamic status and decrease complications. Recent increases in the incidence of AKI point to the conclusion clinicians are poorly managing IOH.15 This suggests an apparent gap in knowledge regarding the effect of IOH on patient outcomes. Quality improvement initiatives developed to optimize hemodynamic management and prevent IOH through a multifaceted approach are needed to reduce the risk of harm to patients. Increased awareness of the harmful effects of IOH can curb the use of non-evidence-based practices and improve outcomes for the surgical patient. Focused education is needed to help prepare anesthesia providers with strategies for improved management and prevention of IOH to decrease patient complications and death.

    Take action

    Anesthesia clinicians may be delivering their patients to the post-anesthesia care unit or next level of care unaware of any patient consequences or untoward effects of the anesthetic delivered. Until all providers have postoperative quality data to suggest otherwise, we may be causing iatrogenic harm to our patients incurred from the cumulative time spent under IOH or improperly managed hemodynamics. To improve care, this public safety issue must be acknowledged by anesthesia clinicians and steps should be taken to enhance management for the perioperative patient. Monitoring of IOH may be improved with continuous arterial blood pressure and advanced hemodynamic technologies leading to reductions in the severity and duration of hypotension. Finally, anesthesia clinicians are urged to incorporate the intraoperative use of GDHT to optimize patients’ hemodynamic status to improve outcomes.

    What you can do TODAY

    • Take time to review your practice’s ERAS protocols and anesthesia fluid management strategies.
    • Replace “fluid restriction” with fluid optimization.
    • FILL FLOW PRESSURE: consider this mantra in the operating room
      • FIRST Fill the tank and optimize fluids
      • THEN address flow (cardiac index)
      • THEN use vasopressors to avoid hypotension
    • Maintain hemodynamic stability to avoid potential harm to our patients.

    What’s on the horizon TOMORROW

    IOH is a common issue that can be avoided. Traditionally, IOH is treated reactively after it becomes apparent and possibly after flow sensitive organs like the gut and kidneys become ischemic.8,17,23 However, technological advancements have made it possible for anesthesia clinicians to transition from the reactive treatment of IOH to a proactive approach by preventing its occurrence.  Hypotension can now be predicted before other traditional parameters using artificial intelligence. Anesthesia clinicians are able to anticipate issues early and avoid patient harm by reducing the severity and duration of IOH, and even prevent it from happening with proactive strategies utilizing this new technology.8 Adoption of these emerging technologies will help better inform our clinical decisions for better patient outcomes.


    Amy Yerdon, DNP, CRNA, is Assistant Professor, School of Nursing, University of Alabama at Birmingham; Assistant Program Director, BSN-DNP Nurse Anesthesia Pathway; Director, Board of Alabama Association of Nurse Anesthetists.

    Desiree Chappell, MSNA, CRNA, FAANA, is Vice President of Clinical Quality, Northstar Anesthesia; Co-Editor in Chief, TopMedTalk; Faculty, Middle Tennessee School of Nurse Anesthesia- Acute Pain Management Fellowship

     

     

    References

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    2. Salmasi V, Maheshwari K, Yang D, et al. Relationship between intraoperative hypotension, defined by either reduction from baseline or absolute thresholds, and acute kidney and myocardial injury after noncardiac surgery: A retrospective cohort analysis. 2017;126:47-65. doi: 10.1097/ALN.0000000000001432
    3. Shah N, Mentz G, Kheterpal S. The incidence of intraoperative hypotension in moderate to high risk patient undergoing non-cardiac surgery: A retrospective multicenter observational analysis. J Clin Anesth.2020;66(109961):1-12. https://doi.org/10.1016/j.jclinane.2020.109961
    4. ePreop 31: Intraoperative hypotension (IOH) among non-emergent noncardiac surgical cases. 2020. https://www.provationmedical.com/wp-content/uploads/2022/08/ePreop-Provation_IOH_Specifications.pdf
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    6. Futier E, Lefrant JY, Guinot PG, et al. Effect of individualized vs standard blood pressure management strategies on postoperative organ dysfunction among high-risk patients undergoing major surgery. JAMA. 2017;318(14):1346. https://doi.org/10.1001/jama.2017.14172
    7. Gregory A, Stapelfeldt W, Khanna A, et al. Intraoperative hypotension is associated with adverse clinical outcomes after noncardiac surgery. Anesth Analg. 2020;x(x):1-12. doi:10.1213/ANE.0000000000005250
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