- Email: [email protected]
Pediatric Postoperative Pulse Oximetry Monitoring During Transport to the Postanesthesia Care Unit Reduces Frequency of Hypoxemia
The Joint Commission Journal on Quality and Patient Safety 2017; 43:146–150
IMPROVEMENT BRIEF
Pediatric Postoperative Pulse Oximetry Monitoring During Transport to the Postanesthesia Care Unit Reduces Frequency of Hypoxemia Thomas J. Caruso, MD, MEd; Tara E. Mokhtari, BS; Monica J. Coughlan, BS; Diane S. Wu, BS; Juan L. Marquez, MD; Melissa Duan, MD; Heather Freeman, RN, MS, NNP-BC, CNS; Andrew Giustini, MD, PhD; Mary Tweedy, RN; Paul J. Sharek, MD, MPH
Background: The standard use of pulse oximetry during the transport of postoperative patients from the operating room (OR) to the postanesthesia care unit (PACU) is not routinely practiced. A study was conducted to determine if the frequency of hypoxemia on admission to the PACU decreased after implementation of routine use of transport pulse oximeters for postoperative patients being transferred to the PACU. Methods: In this prospective cohort study, which was conducted at an academic pediatric hospital, the primary outcome measure was the frequency of hypoxemic events on arrival to the PACU. Results: A total of 506 patients in the preintervention phase and 597 in the postintervention phase met the inclusion criteria. Six hypoxemic events on arrival to the PACU were identified in preintervention phase versus zero in the postintervention period, p = 0.009. Use of oxygen monitors during transport from the OR to the PACU increased from 0% to 100%, p < 0.0001, in the postintervention phase. The median duration of unmonitored time during transport decreased from 272 seconds to 13 seconds, p < 0.0001. Of the 605 patients who met the inclusion criteria for sustainment audits—conducted 18 months after the postimplementation evaluation—99.8% were transported to the PACU with a pulse oximeter, and there were zero reported hypoxemic patients on PACU admission. Conclusion: The routine use of portable oxygen monitoring when transferring patients from the OR to the PACU is a low-cost, noninvasive safety measure that should be considered at any institution performing pediatric general anesthesia.
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ompared to adults, children have increased oxygen consumption, which contributes to faster time to desaturation after apnea.1–4 Also, the risk of laryngospasm in the perioperative period is greater in children than adults.5 These differences are amplified in the postoperative period due to residual anesthetics, which lead to an increased risk of airway obstruction and thus an increased risk of clinically important hypoxemia.6 Pediatric anesthesiologists often rely on physical examination findings, including retractions, tachypnea, nasal flaring, changes in respiratory patterns, and cyanosis, to diagnosis hypoxemia.7 Given that the average time for a child to desaturate after apnea is relatively short, dropping as low as 40% in as little as 1.5 minutes in children under 18 years old depending on age and other physiologic factors, the transfer of a postoperative pediatric patient from the operating room (OR) to the postanesthesia care unit (PACU) represents a period of increased risk for clinically relevant hypoxemia in pediatric patients.4 Pulse oximetry provides clinicians with noninvasive, inexpensive, accurate, and rapid assessment of oxygen 1553-7250/$-see front matter © 2016 The Joint Commission. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jcjq.2016.12.001
saturation.8 In a study of pediatric surgical patients, Coté et al. showed that pulse oximetry detected hypoxemia faster than clinical observation alone.9 Patients of anesthesiologists without pulse oximetry had a statistically significant increase in the number of major hypoxic events and duration of hypoxemia, regardless of clinician expertise.9 The routine use of portable pulse oximetry for transport of postoperative patients to the PACU is yet to be adopted as a national standard of care. Personal correspondence to 10 academic pediatric hospitals revealed that only 1 hospital used pulse oximetry routinely for every OR-to-PACU transfer. At our institution, despite the use of supplemental oxygen during every OR-to-PACU transfer, there were still occurrence reports of patients arriving at the PACU with clinically undetected hypoxemia. These occurrence reports prompted a multidisciplinary quality improvement effort that identified lack of monitoring as a key driver leading to clinically undiagnosed hypoxemia during the transport of patients from the OR to the PACU. The aim of this study was to compare the frequency of patients with significant hypoxemia on arrival to the PACU before and after the implementation of the standard use of oximeters for every OR-to-PACU transfer.
Volume 43, No. 3, March 2017
METHODS Study Design and Setting
We conducted a prospective cohort study with historical controls at a 311-bed, freestanding academic pediatric hospital in Northern California containing seven ORs and a 13bed PACU. The Institutional Review Board at Stanford University reviewed and approved a waiver of consent for this project. The study took place between December 2013 and October 2015 and consisted of the following phases: 1. Preintervention: December 16, 2013–February 2, 2014 2. Intervention: February 3, 2014–March 2, 2014 3. Postintervention: March 3, 2014–April 14, 2014 4. Sustainment: September 1, 2015–October 15, 2015 Study Population
The study population included all patients who underwent procedures in one of the seven ORs who were admitted to the PACU postoperatively. Exclusion criteria included patients admitted to the ICU postoperatively, patients with cyanotic heart lesions, and patients who underwent procedures in non-OR settings (because portable pulse oximetry during those transports was already a standard of care due to longer travel distance to the PACU). Criteria for admission to the ICU included those patients who were critically ill with unstable vital signs or in need of intensive monitoring. The anesthesiologist, surgeon, and intensivist routinely reviewed OR patients prior to admission to the ICU. Intervention
A multidisciplinary team of pediatric anesthesiologists, PACU nurses, OR nurses, anesthesia technicians, bioengineers, and quality improvement experts used Lean methodology problem solving to approach the problem of clinically undiagnosed hypoxemia on admission to the PACU. Current state analysis revealed that attending anesthesiologists consistently transported patients to the PACU with supplemental oxygen after preoxygenation with 100% inspired oxygen prior to extubation. Approximately 60% of transports included an anesthesia resident or fellow in addition to the attending anesthesiologist. The OR nurse and a member of the surgical team also accompanied the patient during transport. The distance from the OR to the PACU is approximately 135 feet. An analysis of the problem revealed that the anesthesiologist’s attention to the patient’s respiratory status was divided between driving the patient’s stretcher and monitoring the patient, which may have decreased the likelihood of clinically identifying hypoxemia. Also, there was no standard method for making pulse oximeters available for this transport, and the ORs lacked the number of pulse oximeters needed to monitor every patient transfer. One key driver emerged from the analysis of multiple cases of hypoxemia: the lack of consistent use of monitors during transport to facilitate early recognition of hypoxemia. Countermeasures to facilitate this key driver included increasing the number of pulse oximeters available for transportation
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in the perioperative environment, developing standard work for placing the patient on a pulse oximeter during transport to the PACU, developing standard work for cleaning and reusing the pulse oximeters, and educating anesthesia providers on the utility of pulse oximeters during transfer to the PACU. Pulse oximetry was chosen as the primary intervention over increased monitoring time in the OR because it provided a low-cost, reliable method to detect hypoxemia without increasing time between cases. Once these countermeasures were developed, the perioperative team was educated over the course of one month (“intervention” time frame) on the importance of standardizing the use of pulse oximeters for every transport. OR nurses became champions for this intervention as they were the primary resource for placing the portable pulse oximeters (Masimo “Radical-7,” Irvine, California) on the patient’s bed postoperatively and then cleaning and returning the oximeters to the OR prior to the next case. A member of the research team was made available during this month to provide onsite training and answer questions. A preexisting standard of care provided all postoperative patients with a Mapleson D circuit during transport to provide supplemental oxygen and positive pressure ventilation if necessary. PACU nurses reliably use our hospital’s occurrence reporting system (an institutional system designed to identify areas of opportunity to improve patient care and decrease patient harm) to report patients who arrive at the PACU with an oxygen saturation <92%, which we defined as a hypoxemic event in this study. Data from the occurrence reporting system for eligible cases were reviewed and hypoxemic events were identified prior to and after the initial intervention and during the sustainment period. To quantify the use of pulse oximeters during the transport of patients from the OR to the PACU, three trained observers audited a convenience sample of patients undergoing general anesthesia during the pre- and postintervention periods. These observers identified (1) whether portable pulse oximeters were used during patient transport to the PACU and (2) the duration of time the patient was unmonitored by pulse oximetry during transfer from the OR to PACU admission. During the sustainment period, the PACU nurses reported the absence of a portable pulse oximeter upon admission to the PACU. Outcomes
The pre- and postintervention outcomes included the frequency of hypoxemic events on arrival to the PACU, frequency of pulse oximetry use during transport from the OR to the PACU, and the length of time a patient was unmonitored during transport from the OR to the PACU. The sustainment outcomes included the frequency of hypoxemic events on arrival to the PACU and frequency of pulse oximetry used during transport from the OR to the PACU. A hypoxemic event was defined as a saturation of less than 92%.8 The value was considered accurate only after potential plethysmograph movement artifact had subsided.10
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At oxygen saturations less than 92%, small decreases in saturation lead to large decreases in oxyhemoglobin as seen on the oxyhemoglobin dissociation curve.11,12 Data Analysis
Study data were managed using the REDCap (Research Electronic Data Capture) tool, hosted by Stanford University. REDCap is a secure, Web-based application designed to support data capture for research studies. Study data were analyzed using SAS 9.3 (SAS Institute Inc., Cary, North Carolina). To test for statistical significance, Fisher’s exact test was used to compare the frequency of hypoxemic events on arrival to the PACU, as well as to compare the frequency of pulse oximetry use pre- versus postintervention. The Mann-Whitney U test was used to compare the time patients were unmonitored during transport pre- versus postintervention. Median and interquartile ranges (25th to 75th) were reported as “median (IQR).” Results were considered to be statistically significant if p values were less than 0.05. Results from the sustainment period were reported as the percentage of patients with a pulse oximeter on arrival to the PACU and frequency of hypoxemic events. RESULTS
A total of 1,708 patients met inclusion criteria during this study (506 in the preintervention phase, 597 in the postintervention
phase, and 605 in the sustainment phase). Six hypoxemic events on arrival to the PACU were identified in the preintervention phase via review of occurrence reports. The oxygen saturations were 77%, 84%, 62%, 47%, 88%, and 91%. There were no hypoxemic events on arrival to the PACU in the postintervention period, thus the frequency of hypoxemic events dropped from 6/506 PACU admissions to 0/597 PACU admissions, p = 0.009. There were no reported incidents of hypoxemia during the sustainment period (0/605). Forty-six patient transports were audited (23 during the preintervention phase and 23 during the postintervention phase) to determine monitor use and unmonitored transport time. Use of oxygen monitors during transport increased from 0% to 100% (p < 0.0001). The median duration that the patient was unmonitored during transport decreased significantly from 272 seconds (IQR, 225–317 seconds) to 13 seconds (IQR, 9–25 seconds), p < 0.0001 (Figure 1). Of the 605 patients admitted to the PACU during the sustainment period, 604 (99.8%) had a pulse oximeter. Preintervention, the occurrence reports indicated that hypoxemia was diagnosed after the patient was placed on the monitors in the PACU, with all 6 requiring oxygen treatment. Although it was not within the scope of this study to have an observer present during the transport of every patient included in the study, the assumption is that pulse oximetry in the postintervention time frame provided early
Outlier Box Plot of Median Duration of Time That Oxygen Saturation Was Unmonitored During Transport, Pre- and Postintervention
Figure 1: The median time oxygen saturation was unmonitored decreased during patient transport from the operating room (OR) to the postanesthesia care unit (PACU) from 272 seconds to 13 seconds (p < 0.0001) after intervention of routine portable pulse oximetry monitoring
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detection and treatment of respiratory decline prior to significant hypoxemia on arrival to the PACU. DISCUSSION
Despite the well-understood risks of prolonged hypoxemia in postoperative pediatric patients, the routine use of pulse oximetry during transport from the OR to the PACU is not a national standard. Our standardized process was associated with a reduction in the frequency of hypoxemia on arrival to the PACU, significantly increased the use of portable pulse oximetry, and significantly reduced the amount of time a patient was unmonitored during the immediate postoperative period. Audits completed 18 months after intervention demonstrate sustainment of the process and outcomes. To our knowledge, this is the first prospective study to examine rates of hypoxemia after patient transfer from the OR to the PACU. The implications of these findings are substantial. First, the reliable use of a pulse oximeter during transport between the OR and the PACU resulted in appropriate situational awareness, likely allowing anesthesiologists to more effectively address desaturations during transport, resulting in elimination of undiagnosed hypoxemia at the time of PACU admission. Although all patients were transported with supplemental oxygen via a Mapleson D circuit, the anesthesiologist previously relied on clinical signs alone to prompt intervention prior to implementation of this process. Second, prior to our intervention some patients experienced preventable, significant hypoxemia. This calls into question the preintervention assumption by our anesthesiologists that the addition of a pulse oximeter would not decrease time to diagnosis of hypoxemia during transport. This finding is also consistent with prior data that have shown clinical manifestations of hypoxemia to present variably, with cyanosis being most common after the saturation falls below 72%.9 Third, the creation of a reliable process to provide pulse oximeters for transport was relatively straightforward. Of the postintervention patients audited, all had a pulse oximeter in place, which indicated that the process was effective. The sustainment period audits demonstrated reliability of the process and an adoption of a new standard of care. Because there is little lapse in monitoring during transport, it has become rare for PACU nurses to be surprised by the arrival of previously undiagnosed hypoxemic patients. The most likely reason why we observed a decrease in frequency of patients arriving at the PACU with hypoxemia was due to increased oximetry monitoring of patients. Prior to institution of routine monitoring, the average duration of unmonitored time was 4 minutes and 48 seconds. Pediatric patients preoxygenated for 3 minutes will desaturate from 100% to 40% in 3.59 to 8.1 minutes of apnea, depending on age and other physiologic factors.4 By decreasing average unmonitored transport time from almost 5 minutes to less than 30 seconds, we decreased the possibility of unobserved desaturations prior to PACU arrival.
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As with many substantial quality improvement efforts, there were challenges to the reliability and sustainability of the intervention. First, prior to intervention, anecdotal reports from staff anesthesiologists attributed the incidence of hypoxemia in the PACU to varying degrees of expertise in trainees and faculty (and not due to a lack of monitoring). However, Coté et al.’s previously reported results demonstrated that there were no differences between incidence of hypoxemia and level of training.9 By using previously published literature to justify the intervention, buy-in was increased at both the physician and nurse level during the education and intervention phase. Second, given that baseline data showed that hypoxemia occurred about 1% of the time, we were concerned that anesthesiologists would not have personally experienced a patient with a hypoxemic event during transport and thus would not perceive this to be a patient safety concern worthy of a process change. Observation audits provided a means to visually display data quickly to highlight both baseline frequency and successes of the intervention in the perioperative environment. Due to the clear benefit to patient safety and the build of a reliable process, the routine use of pulse oximeters has been sustained. Finally, given the propensity of pulse oximeters to be dispersed through the hospital, we were concerned that pulse oximeters might not be reliably available for all transfers from the OR to the PACU, thus potentially undermining the sustainability of the intervention. To minimize the risk, we obtained additional pulse oximeters for the perioperative environment so that each OR now has two pulse oximeters, one as a backup in the event of machine malfunction or absence. Limitations
There were several limitations to our study. First, we relied on PACU nurses to voluntarily report the frequency of hypoxemia on arrival to the PACU via the hospital’s occurrence reporting system. It is possible that not all incidents were reported. This would bias the results in an unpredictable direction. However, the PACU nurses provided part of the impetus for this intervention, and they were highly motivated to participate in the reporting process, thus minimizing the risk of reporting bias in this study. Second, the sample size of patients audited for the process measures of “time unmonitored” was relatively small. This sampling strategy could bias the results in an unknown direction. Third, longitudinal outcomes such as significant clinical impacts of the patients’ hypoxemia were not measured in this study. Fourth, as with other pre-post study designs, there may have been other factors that contributed to the outcome, including temporal changes in types of patients presenting for surgery or more vigilant staff. There may have other undocumented cointerventions that contributed to the results. Finally, because this study was conducted in a moderately sized PACU in an academic center, these results may not be transferrable to different PACU settings.
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CONCLUSION
REFERENCES
The routine use of pulse oximetry for the transport of patients from the OR to the PACU, when coupled with routine use of supplemental oxygen, significantly reduced the amount of unmonitored time and was associated with a reduction in the frequency of hypoxemia on arrival to the PACU. Because of the increased risk of hypoxemia in postoperative children and the potentially life threatening nature of such events, the elimination of hypoxemic events during transport between OR and PACU reported in this study is encouraging. The routine use of portable oxygen monitoring with supplemental oxygen during transfer of patients from the OR to the PACU is a low-cost, noninvasive safety measure that should be considered at any institution performing pediatric general anesthesia.
1. Lindahl SG. Oxygen consumption and carbon dioxide elimination in infants and children during anaesthesia and surgery. Br J Anaesth. 1989;62:70–76. 2. Thorsteinsson A, et al. Functional residual capacity in anesthetized children: normal values and values in children with cardiac anomalies. Anesthesiology. 1990;73:876– 881. 3. Gerhardt T, et al. Functional residual capacity in normal neonates and children up to 5 years of age determined by a N2 washout method. Pediatr Res. 1986;20:668– 671. 4. Hardman JG, Wills JS. The development of hypoxaemia during apnoea in children: a computational modelling investigation. Br J Anaesth. 2006;97:564–570. 5. Olsson GL, Hallen B. Laryngospasm during anaesthesia. A computer-aided incidence study in 136,929 patients. Acta Anaesthesiol Scand. 1984;28:567–575. 6. Caruso TJ, Janik LS, Fuzaylov G. Airway management of recovered pediatric patients with severe head and neck burns: a review. Paediatr Anaesth. 2012;22:462–468. 7. Hermansen CL, Lorah KN. Respiratory distress in the newborn. Am Fam Physician. 2007;76:987–994. 8. Ross PA, Newth CJ, Khemani RG. Accuracy of pulse oximetry in vhildren. Pediatrics. 2014;133:22–29. 9. Coté CJ, et al. A single-blind study of pulse oximetry in children. Anesthesiology. 1988;68:184–188. 10. Pedersen T, et al. Pulse oximetry for perioperative monitoring. Cochrane Database Syst Rev. 2014;(3):CD002013. 11. Adair GS. The hemoglobin system VI. The oxygen dissociation curve of hemoglobin. J Biol Chem. 1925;63:529– 545. 12. Hill AV. The possible effects of the aggregation of the molecules of haemoglobin on its dissociation curves. J Physiol. 1910;40(suppl):iv–vii.
Conflicts of Interest. All authors report no conflicts of interest.
Thomas J. Caruso, MD, MEd, is Clinical Assistant Professor of Anesthesiology, Perioperative and Pain Medicine, and Physician Lead for Perioperative Quality Improvement, Lucile Packard Children’s Hospital, Palo Alto, California, and Stanford University Medical Center, Stanford, California. Tara E. Mokhtari, BS, Monica J. Coughlin, BS, and Diane S. Wu, BS, are Stanford Medical Students. Juan L. Marquez, MD, is an Anesthesia Resident, University of Michigan Medical Center, Ann Arbor, Michigan. Melissa Duan, MD, is Director, Pediatric Anesthesiology, Providence St. Vincent Medical Center, Portland, Oregon. Heather Freeman, RN, MS, NNP-BC, CNS, is Director, Performance Improvement, Lucile Packard Children’s Hospital. Andrew Giustini, MD, PhD, is a Pediatrics and Anesthesia Resident, Lucile Packard Children’s Hospital and Stanford University Medical Center. Mary Tweedy, RN, is PACU Assistant Nurse Manager, Lucile Packard Children’s Hospital. Paul J. Sharek, MD, MPH, is Professor of Pediatrics and Chief Clinical Patient Safety Officer, Lucile Packard Children’s Hospital. Please address correspondence to Thomas J. Caruso, [email protected].
IMPROVEMENT BRIEF
Pediatric Postoperative Pulse Oximetry Monitoring During Transport to the Postanesthesia Care Unit Reduces Frequency of Hypoxemia Thomas J. Caruso, MD, MEd; Tara E. Mokhtari, BS; Monica J. Coughlan, BS; Diane S. Wu, BS; Juan L. Marquez, MD; Melissa Duan, MD; Heather Freeman, RN, MS, NNP-BC, CNS; Andrew Giustini, MD, PhD; Mary Tweedy, RN; Paul J. Sharek, MD, MPH
Background: The standard use of pulse oximetry during the transport of postoperative patients from the operating room (OR) to the postanesthesia care unit (PACU) is not routinely practiced. A study was conducted to determine if the frequency of hypoxemia on admission to the PACU decreased after implementation of routine use of transport pulse oximeters for postoperative patients being transferred to the PACU. Methods: In this prospective cohort study, which was conducted at an academic pediatric hospital, the primary outcome measure was the frequency of hypoxemic events on arrival to the PACU. Results: A total of 506 patients in the preintervention phase and 597 in the postintervention phase met the inclusion criteria. Six hypoxemic events on arrival to the PACU were identified in preintervention phase versus zero in the postintervention period, p = 0.009. Use of oxygen monitors during transport from the OR to the PACU increased from 0% to 100%, p < 0.0001, in the postintervention phase. The median duration of unmonitored time during transport decreased from 272 seconds to 13 seconds, p < 0.0001. Of the 605 patients who met the inclusion criteria for sustainment audits—conducted 18 months after the postimplementation evaluation—99.8% were transported to the PACU with a pulse oximeter, and there were zero reported hypoxemic patients on PACU admission. Conclusion: The routine use of portable oxygen monitoring when transferring patients from the OR to the PACU is a low-cost, noninvasive safety measure that should be considered at any institution performing pediatric general anesthesia.
C
ompared to adults, children have increased oxygen consumption, which contributes to faster time to desaturation after apnea.1–4 Also, the risk of laryngospasm in the perioperative period is greater in children than adults.5 These differences are amplified in the postoperative period due to residual anesthetics, which lead to an increased risk of airway obstruction and thus an increased risk of clinically important hypoxemia.6 Pediatric anesthesiologists often rely on physical examination findings, including retractions, tachypnea, nasal flaring, changes in respiratory patterns, and cyanosis, to diagnosis hypoxemia.7 Given that the average time for a child to desaturate after apnea is relatively short, dropping as low as 40% in as little as 1.5 minutes in children under 18 years old depending on age and other physiologic factors, the transfer of a postoperative pediatric patient from the operating room (OR) to the postanesthesia care unit (PACU) represents a period of increased risk for clinically relevant hypoxemia in pediatric patients.4 Pulse oximetry provides clinicians with noninvasive, inexpensive, accurate, and rapid assessment of oxygen 1553-7250/$-see front matter © 2016 The Joint Commission. Published by Elsevier Inc. All rights reserved. http://dx.doi.org/10.1016/j.jcjq.2016.12.001
saturation.8 In a study of pediatric surgical patients, Coté et al. showed that pulse oximetry detected hypoxemia faster than clinical observation alone.9 Patients of anesthesiologists without pulse oximetry had a statistically significant increase in the number of major hypoxic events and duration of hypoxemia, regardless of clinician expertise.9 The routine use of portable pulse oximetry for transport of postoperative patients to the PACU is yet to be adopted as a national standard of care. Personal correspondence to 10 academic pediatric hospitals revealed that only 1 hospital used pulse oximetry routinely for every OR-to-PACU transfer. At our institution, despite the use of supplemental oxygen during every OR-to-PACU transfer, there were still occurrence reports of patients arriving at the PACU with clinically undetected hypoxemia. These occurrence reports prompted a multidisciplinary quality improvement effort that identified lack of monitoring as a key driver leading to clinically undiagnosed hypoxemia during the transport of patients from the OR to the PACU. The aim of this study was to compare the frequency of patients with significant hypoxemia on arrival to the PACU before and after the implementation of the standard use of oximeters for every OR-to-PACU transfer.
Volume 43, No. 3, March 2017
METHODS Study Design and Setting
We conducted a prospective cohort study with historical controls at a 311-bed, freestanding academic pediatric hospital in Northern California containing seven ORs and a 13bed PACU. The Institutional Review Board at Stanford University reviewed and approved a waiver of consent for this project. The study took place between December 2013 and October 2015 and consisted of the following phases: 1. Preintervention: December 16, 2013–February 2, 2014 2. Intervention: February 3, 2014–March 2, 2014 3. Postintervention: March 3, 2014–April 14, 2014 4. Sustainment: September 1, 2015–October 15, 2015 Study Population
The study population included all patients who underwent procedures in one of the seven ORs who were admitted to the PACU postoperatively. Exclusion criteria included patients admitted to the ICU postoperatively, patients with cyanotic heart lesions, and patients who underwent procedures in non-OR settings (because portable pulse oximetry during those transports was already a standard of care due to longer travel distance to the PACU). Criteria for admission to the ICU included those patients who were critically ill with unstable vital signs or in need of intensive monitoring. The anesthesiologist, surgeon, and intensivist routinely reviewed OR patients prior to admission to the ICU. Intervention
A multidisciplinary team of pediatric anesthesiologists, PACU nurses, OR nurses, anesthesia technicians, bioengineers, and quality improvement experts used Lean methodology problem solving to approach the problem of clinically undiagnosed hypoxemia on admission to the PACU. Current state analysis revealed that attending anesthesiologists consistently transported patients to the PACU with supplemental oxygen after preoxygenation with 100% inspired oxygen prior to extubation. Approximately 60% of transports included an anesthesia resident or fellow in addition to the attending anesthesiologist. The OR nurse and a member of the surgical team also accompanied the patient during transport. The distance from the OR to the PACU is approximately 135 feet. An analysis of the problem revealed that the anesthesiologist’s attention to the patient’s respiratory status was divided between driving the patient’s stretcher and monitoring the patient, which may have decreased the likelihood of clinically identifying hypoxemia. Also, there was no standard method for making pulse oximeters available for this transport, and the ORs lacked the number of pulse oximeters needed to monitor every patient transfer. One key driver emerged from the analysis of multiple cases of hypoxemia: the lack of consistent use of monitors during transport to facilitate early recognition of hypoxemia. Countermeasures to facilitate this key driver included increasing the number of pulse oximeters available for transportation
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in the perioperative environment, developing standard work for placing the patient on a pulse oximeter during transport to the PACU, developing standard work for cleaning and reusing the pulse oximeters, and educating anesthesia providers on the utility of pulse oximeters during transfer to the PACU. Pulse oximetry was chosen as the primary intervention over increased monitoring time in the OR because it provided a low-cost, reliable method to detect hypoxemia without increasing time between cases. Once these countermeasures were developed, the perioperative team was educated over the course of one month (“intervention” time frame) on the importance of standardizing the use of pulse oximeters for every transport. OR nurses became champions for this intervention as they were the primary resource for placing the portable pulse oximeters (Masimo “Radical-7,” Irvine, California) on the patient’s bed postoperatively and then cleaning and returning the oximeters to the OR prior to the next case. A member of the research team was made available during this month to provide onsite training and answer questions. A preexisting standard of care provided all postoperative patients with a Mapleson D circuit during transport to provide supplemental oxygen and positive pressure ventilation if necessary. PACU nurses reliably use our hospital’s occurrence reporting system (an institutional system designed to identify areas of opportunity to improve patient care and decrease patient harm) to report patients who arrive at the PACU with an oxygen saturation <92%, which we defined as a hypoxemic event in this study. Data from the occurrence reporting system for eligible cases were reviewed and hypoxemic events were identified prior to and after the initial intervention and during the sustainment period. To quantify the use of pulse oximeters during the transport of patients from the OR to the PACU, three trained observers audited a convenience sample of patients undergoing general anesthesia during the pre- and postintervention periods. These observers identified (1) whether portable pulse oximeters were used during patient transport to the PACU and (2) the duration of time the patient was unmonitored by pulse oximetry during transfer from the OR to PACU admission. During the sustainment period, the PACU nurses reported the absence of a portable pulse oximeter upon admission to the PACU. Outcomes
The pre- and postintervention outcomes included the frequency of hypoxemic events on arrival to the PACU, frequency of pulse oximetry use during transport from the OR to the PACU, and the length of time a patient was unmonitored during transport from the OR to the PACU. The sustainment outcomes included the frequency of hypoxemic events on arrival to the PACU and frequency of pulse oximetry used during transport from the OR to the PACU. A hypoxemic event was defined as a saturation of less than 92%.8 The value was considered accurate only after potential plethysmograph movement artifact had subsided.10
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At oxygen saturations less than 92%, small decreases in saturation lead to large decreases in oxyhemoglobin as seen on the oxyhemoglobin dissociation curve.11,12 Data Analysis
Study data were managed using the REDCap (Research Electronic Data Capture) tool, hosted by Stanford University. REDCap is a secure, Web-based application designed to support data capture for research studies. Study data were analyzed using SAS 9.3 (SAS Institute Inc., Cary, North Carolina). To test for statistical significance, Fisher’s exact test was used to compare the frequency of hypoxemic events on arrival to the PACU, as well as to compare the frequency of pulse oximetry use pre- versus postintervention. The Mann-Whitney U test was used to compare the time patients were unmonitored during transport pre- versus postintervention. Median and interquartile ranges (25th to 75th) were reported as “median (IQR).” Results were considered to be statistically significant if p values were less than 0.05. Results from the sustainment period were reported as the percentage of patients with a pulse oximeter on arrival to the PACU and frequency of hypoxemic events. RESULTS
A total of 1,708 patients met inclusion criteria during this study (506 in the preintervention phase, 597 in the postintervention
phase, and 605 in the sustainment phase). Six hypoxemic events on arrival to the PACU were identified in the preintervention phase via review of occurrence reports. The oxygen saturations were 77%, 84%, 62%, 47%, 88%, and 91%. There were no hypoxemic events on arrival to the PACU in the postintervention period, thus the frequency of hypoxemic events dropped from 6/506 PACU admissions to 0/597 PACU admissions, p = 0.009. There were no reported incidents of hypoxemia during the sustainment period (0/605). Forty-six patient transports were audited (23 during the preintervention phase and 23 during the postintervention phase) to determine monitor use and unmonitored transport time. Use of oxygen monitors during transport increased from 0% to 100% (p < 0.0001). The median duration that the patient was unmonitored during transport decreased significantly from 272 seconds (IQR, 225–317 seconds) to 13 seconds (IQR, 9–25 seconds), p < 0.0001 (Figure 1). Of the 605 patients admitted to the PACU during the sustainment period, 604 (99.8%) had a pulse oximeter. Preintervention, the occurrence reports indicated that hypoxemia was diagnosed after the patient was placed on the monitors in the PACU, with all 6 requiring oxygen treatment. Although it was not within the scope of this study to have an observer present during the transport of every patient included in the study, the assumption is that pulse oximetry in the postintervention time frame provided early
Outlier Box Plot of Median Duration of Time That Oxygen Saturation Was Unmonitored During Transport, Pre- and Postintervention
Figure 1: The median time oxygen saturation was unmonitored decreased during patient transport from the operating room (OR) to the postanesthesia care unit (PACU) from 272 seconds to 13 seconds (p < 0.0001) after intervention of routine portable pulse oximetry monitoring
Volume 43, No. 3, March 2017
detection and treatment of respiratory decline prior to significant hypoxemia on arrival to the PACU. DISCUSSION
Despite the well-understood risks of prolonged hypoxemia in postoperative pediatric patients, the routine use of pulse oximetry during transport from the OR to the PACU is not a national standard. Our standardized process was associated with a reduction in the frequency of hypoxemia on arrival to the PACU, significantly increased the use of portable pulse oximetry, and significantly reduced the amount of time a patient was unmonitored during the immediate postoperative period. Audits completed 18 months after intervention demonstrate sustainment of the process and outcomes. To our knowledge, this is the first prospective study to examine rates of hypoxemia after patient transfer from the OR to the PACU. The implications of these findings are substantial. First, the reliable use of a pulse oximeter during transport between the OR and the PACU resulted in appropriate situational awareness, likely allowing anesthesiologists to more effectively address desaturations during transport, resulting in elimination of undiagnosed hypoxemia at the time of PACU admission. Although all patients were transported with supplemental oxygen via a Mapleson D circuit, the anesthesiologist previously relied on clinical signs alone to prompt intervention prior to implementation of this process. Second, prior to our intervention some patients experienced preventable, significant hypoxemia. This calls into question the preintervention assumption by our anesthesiologists that the addition of a pulse oximeter would not decrease time to diagnosis of hypoxemia during transport. This finding is also consistent with prior data that have shown clinical manifestations of hypoxemia to present variably, with cyanosis being most common after the saturation falls below 72%.9 Third, the creation of a reliable process to provide pulse oximeters for transport was relatively straightforward. Of the postintervention patients audited, all had a pulse oximeter in place, which indicated that the process was effective. The sustainment period audits demonstrated reliability of the process and an adoption of a new standard of care. Because there is little lapse in monitoring during transport, it has become rare for PACU nurses to be surprised by the arrival of previously undiagnosed hypoxemic patients. The most likely reason why we observed a decrease in frequency of patients arriving at the PACU with hypoxemia was due to increased oximetry monitoring of patients. Prior to institution of routine monitoring, the average duration of unmonitored time was 4 minutes and 48 seconds. Pediatric patients preoxygenated for 3 minutes will desaturate from 100% to 40% in 3.59 to 8.1 minutes of apnea, depending on age and other physiologic factors.4 By decreasing average unmonitored transport time from almost 5 minutes to less than 30 seconds, we decreased the possibility of unobserved desaturations prior to PACU arrival.
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As with many substantial quality improvement efforts, there were challenges to the reliability and sustainability of the intervention. First, prior to intervention, anecdotal reports from staff anesthesiologists attributed the incidence of hypoxemia in the PACU to varying degrees of expertise in trainees and faculty (and not due to a lack of monitoring). However, Coté et al.’s previously reported results demonstrated that there were no differences between incidence of hypoxemia and level of training.9 By using previously published literature to justify the intervention, buy-in was increased at both the physician and nurse level during the education and intervention phase. Second, given that baseline data showed that hypoxemia occurred about 1% of the time, we were concerned that anesthesiologists would not have personally experienced a patient with a hypoxemic event during transport and thus would not perceive this to be a patient safety concern worthy of a process change. Observation audits provided a means to visually display data quickly to highlight both baseline frequency and successes of the intervention in the perioperative environment. Due to the clear benefit to patient safety and the build of a reliable process, the routine use of pulse oximeters has been sustained. Finally, given the propensity of pulse oximeters to be dispersed through the hospital, we were concerned that pulse oximeters might not be reliably available for all transfers from the OR to the PACU, thus potentially undermining the sustainability of the intervention. To minimize the risk, we obtained additional pulse oximeters for the perioperative environment so that each OR now has two pulse oximeters, one as a backup in the event of machine malfunction or absence. Limitations
There were several limitations to our study. First, we relied on PACU nurses to voluntarily report the frequency of hypoxemia on arrival to the PACU via the hospital’s occurrence reporting system. It is possible that not all incidents were reported. This would bias the results in an unpredictable direction. However, the PACU nurses provided part of the impetus for this intervention, and they were highly motivated to participate in the reporting process, thus minimizing the risk of reporting bias in this study. Second, the sample size of patients audited for the process measures of “time unmonitored” was relatively small. This sampling strategy could bias the results in an unknown direction. Third, longitudinal outcomes such as significant clinical impacts of the patients’ hypoxemia were not measured in this study. Fourth, as with other pre-post study designs, there may have been other factors that contributed to the outcome, including temporal changes in types of patients presenting for surgery or more vigilant staff. There may have other undocumented cointerventions that contributed to the results. Finally, because this study was conducted in a moderately sized PACU in an academic center, these results may not be transferrable to different PACU settings.
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Pediatric Hypoxemia in the Postanesthesia Recovery Room
CONCLUSION
REFERENCES
The routine use of pulse oximetry for the transport of patients from the OR to the PACU, when coupled with routine use of supplemental oxygen, significantly reduced the amount of unmonitored time and was associated with a reduction in the frequency of hypoxemia on arrival to the PACU. Because of the increased risk of hypoxemia in postoperative children and the potentially life threatening nature of such events, the elimination of hypoxemic events during transport between OR and PACU reported in this study is encouraging. The routine use of portable oxygen monitoring with supplemental oxygen during transfer of patients from the OR to the PACU is a low-cost, noninvasive safety measure that should be considered at any institution performing pediatric general anesthesia.
1. Lindahl SG. Oxygen consumption and carbon dioxide elimination in infants and children during anaesthesia and surgery. Br J Anaesth. 1989;62:70–76. 2. Thorsteinsson A, et al. Functional residual capacity in anesthetized children: normal values and values in children with cardiac anomalies. Anesthesiology. 1990;73:876– 881. 3. Gerhardt T, et al. Functional residual capacity in normal neonates and children up to 5 years of age determined by a N2 washout method. Pediatr Res. 1986;20:668– 671. 4. Hardman JG, Wills JS. The development of hypoxaemia during apnoea in children: a computational modelling investigation. Br J Anaesth. 2006;97:564–570. 5. Olsson GL, Hallen B. Laryngospasm during anaesthesia. A computer-aided incidence study in 136,929 patients. Acta Anaesthesiol Scand. 1984;28:567–575. 6. Caruso TJ, Janik LS, Fuzaylov G. Airway management of recovered pediatric patients with severe head and neck burns: a review. Paediatr Anaesth. 2012;22:462–468. 7. Hermansen CL, Lorah KN. Respiratory distress in the newborn. Am Fam Physician. 2007;76:987–994. 8. Ross PA, Newth CJ, Khemani RG. Accuracy of pulse oximetry in vhildren. Pediatrics. 2014;133:22–29. 9. Coté CJ, et al. A single-blind study of pulse oximetry in children. Anesthesiology. 1988;68:184–188. 10. Pedersen T, et al. Pulse oximetry for perioperative monitoring. Cochrane Database Syst Rev. 2014;(3):CD002013. 11. Adair GS. The hemoglobin system VI. The oxygen dissociation curve of hemoglobin. J Biol Chem. 1925;63:529– 545. 12. Hill AV. The possible effects of the aggregation of the molecules of haemoglobin on its dissociation curves. J Physiol. 1910;40(suppl):iv–vii.
Conflicts of Interest. All authors report no conflicts of interest.
Thomas J. Caruso, MD, MEd, is Clinical Assistant Professor of Anesthesiology, Perioperative and Pain Medicine, and Physician Lead for Perioperative Quality Improvement, Lucile Packard Children’s Hospital, Palo Alto, California, and Stanford University Medical Center, Stanford, California. Tara E. Mokhtari, BS, Monica J. Coughlin, BS, and Diane S. Wu, BS, are Stanford Medical Students. Juan L. Marquez, MD, is an Anesthesia Resident, University of Michigan Medical Center, Ann Arbor, Michigan. Melissa Duan, MD, is Director, Pediatric Anesthesiology, Providence St. Vincent Medical Center, Portland, Oregon. Heather Freeman, RN, MS, NNP-BC, CNS, is Director, Performance Improvement, Lucile Packard Children’s Hospital. Andrew Giustini, MD, PhD, is a Pediatrics and Anesthesia Resident, Lucile Packard Children’s Hospital and Stanford University Medical Center. Mary Tweedy, RN, is PACU Assistant Nurse Manager, Lucile Packard Children’s Hospital. Paul J. Sharek, MD, MPH, is Professor of Pediatrics and Chief Clinical Patient Safety Officer, Lucile Packard Children’s Hospital. Please address correspondence to Thomas J. Caruso, [email protected].