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Anesthesia & Analgesia:
doi: 10.1213/ANE.0b013e3182713b61
Obstetric Anesthesiology: Brief Report

Availability of Lipid Emulsion in United States Obstetric Units

Toledo, Paloma MD, MPH*; Nixon, Heather C. MD; Mhyre, Jill M. MD; Wong, Cynthia A. MD§; Weinberg, Guy MD

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Author Information

From the *Department of Anesthesiology and Center for Healthcare Equity/Institute for Healthcare Studies, Northwestern University Feinberg School of Medicine, Chicago; Department of Anesthesiology, University of Illinois Hospital and Health Science System, Chicago, Illinois; Department of Anesthesiology, the University of Michigan Health System, Ann Arbor, Michigan; §Department of Anesthesiology, Northwestern University Feinberg School of Medicine, Chicago; and Department of Anesthesiology, University of Illinois College of Medicine and Jesse Brown VA Medical Center, Chicago, Illinois.

Accepted for publication August 17, 2012

Supported by grant number F32HS020122 from the Agency for Healthcare Research and Quality (PI: Paloma Toledo, MD, MPH). The content is solely the responsibility of the authors and does not necessarily represent the official views of the Agency for Healthcare Research and Quality.

The authors declare no conflicts of interest.

Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.anesthesia-analgesia.org).

Reprints will not be available from the authors.

Address correspondence to Paloma Toledo, MD, MPH, Department of Anesthesiology and Center for Healthcare Equity/Institute for Healthcare Studies, Northwestern University Feinberg School of Medicine, 251 E. Huron St., F5-704, Chicago, IL 60611. Address e-mail to p-toledo@md.northwestern.edu.

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Abstract

BACKGROUND: Lipid emulsion is recommended in the guidelines for the management of local anesthetic systemic toxicity. In this study, we sought to identify the current level of lipid emulsion availability in U.S. obstetric units.

METHODS: A survey was developed addressing lipid emulsion availability and sent to U.S. obstetric anesthesia directors in June 2011. Univariate statistics were used.

RESULTS: The response rate was 69%. Lipid emulsion was available in 88% of the units (95% confidence interval, 73%–94%). At least 95% of respondents had lipid emulsion available in <30 minutes (100% of n = 68).

CONCLUSIONS: U.S. academic obstetric anesthesia units are equipped to administer lipid emulsion in the setting of local anesthetic systemic toxicity.

Local anesthetic systemic toxicity (LAST) after epidural anesthesia is a rare event with an incidence of approximately 4 per 10,000 epidural procedures.1 Clinical consequences range from prodromal symptoms to cardiovascular collapse. The incidence of LAST has been decreasing in the past several decades due to the routine use of a variety of safety measures, such as test dose administration.1 Lipid emulsion has emerged as a potential antidote to LAST.2

In 2007, the Association of Anaesthetists of Great Britain and Ireland (AAGBI) published the first resuscitation guidelines that included lipid emulsion.3 Subsequently, the evidence demonstrating the effectiveness of lipid emulsion has continued to expand.2,4–6 In 2010, the AAGBI, the American Society of Regional Anesthesia (ASRA), and the American Heart Association published guidelines for the management of LAST that included the administration of lipid emulsion.7–9

Although the risk of LAST in obstetric anesthesia practice is low because of the use of dilute concentrations of local anesthetic, the possibility remains, particularly during epidural anesthesia,10 during regional blocks such as the transversus abdominis plane block,11 and as a consequence of medication error.12

A 2007 survey documented the availability of lipid emulsion in obstetric anesthesia units in the United Kingdom,13 but to date, no comparable survey has been completed in the United States. The objective of the current study was to estimate the current level of lipid emulsion availability in U.S. academic obstetric units.

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METHODS

This study was approved by the University of Illinois at Chicago and Northwestern University IRBs. A survey was developed by 2 of the investigators (PT and HCN) on the basis of a review of the literature. Permission was obtained from the authors of previously copyrighted work to use/modify survey questions.13 The survey then underwent expert panel review by 2 obstetric anesthesiologists (CAW and JMM) and an expert in lipid emulsion therapy (GW). The final survey was reviewed by all authors for face validity. The survey is available as a Web supplement (see Supplemental Digital Content 1, http://links.lww.com/AA/A505).

The Society of Academic Anesthesiology Associations’ list-serve was used to identify U.S. anesthesiology residency programs. The names and e-mail contact information for the obstetric anesthesia directors of these programs were obtained through the departments’ Web sites and were subsequently verified. If no information was found, the department chair was contacted by e-mail or phone to obtain this information.

An invitation to complete the electronic survey was e-mailed to the obstetric anesthesia directors. Nonresponders received 2 follow-up e-mail reminders at 1-month intervals. Survey completion implied consent for study participation.

Univariate statistics (counts, percentages, medians) were used to characterize survey responses. Probability distributions for lipid emulsion availability and time to obtain lipid emulsion were estimated using the binomial distribution and the Clopper-Pearson value, respectively. The 95% 2-sided confidence intervals (CIs) are reported. Delivery volume was stratified by lipid emulsion availability, as well as by lipid guideline availability. A 2-tailed t test with unequal variances was used to compare delivery volumes between (a) units that had lipid emulsion available versus those that did not; and (b) units that had guidelines for the management of LAST versus those that did not. Three division directors could not recall the year in which lipid emulsion became available on their units. For the purpose of creating Figure 1, these years were imputed using multiple linear regression, on the basis of the institutional delivery volume, the cesarean delivery rate, the epidural analgesia rate, and the experience of LAST on the unit. Data were analyzed using Stata SE (version 10, StataCorp LP, College Station, TX).

Figure 1
Figure 1
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RESULTS

One hundred four academic anesthesiology programs had a director of obstetric anesthesiology. Seventy-two directors responded to the survey (69% response rate). Characteristics of the responding hospitals are shown in Table 1.

Table 1
Table 1
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Lipid emulsion was available in 88% of the obstetric units (95% CI, 73%–94%). Figure 1 shows when lipid emulsion became available in each unit. Eighty-two percent of the units had lipid emulsion available before the publication of the ASRA guidelines in March 2010. Of the 9 units that did not stock lipid emulsion, 1 unit planned to acquire it; 1 unit was reviewing the evidence; and the remaining 7 units felt that they were at low risk for LAST. Therefore, they did not stock lipid emulsion on the unit. All 9 of these units had lipid emulsion available in another part of the hospital.

At least 95% of respondents had lipid emulsion available in <30 minutes (100% of n = 68). The estimated time to obtain lipid emulsion was <10 minutes in 70 hospitals, and 10 to 30 minutes in the remaining 2. The most common locations for lipid emulsion storage were: a drug dispensing machine (50%), regional anesthesia or line cart (33%), anesthesia workroom (17%), in a code cart (10%), and/or in the operating room (10%).

Of the 72 programs, 10 had previously had an incident of local anesthetic toxicity. Seventy-one percent of the respondents had an algorithm or guideline for the treatment of LAST. Lipid emulsion was a component of all guidelines, and all but 1 guideline included dosing regimens to guide lipid emulsion administration. The majority of the units (96%) had lipid emulsion guidelines posted in multiple locations. The most common locations were on an instruction sheet stored with the lipid emulsion, posted elsewhere on the labor and delivery unit, or on a departmental Web site.

The difference in delivery volume means by lipid emulsion availability was –274 deliveries per year (95% CI, –2253 to 1705), and the difference in means by guideline availability was –788 deliveries per year (95% CI, –1959 to 383).

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DISCUSSION

The results of this survey found that the majority of U.S. obstetric units are equipped to administer lipid emulsion in the setting of LAST, with 88% of responding units having lipid emulsion immediately available in the unit, and the remainder having it available elsewhere in the hospital. In addition, the majority of units have guidelines to manage LAST and dosing guidelines for lipid emulsion administration. In the United Kingdom, the availability of lipid emulsion increased significantly after the publication of AAGBI guidelines.14 In contrast, the majority of U.S. obstetric units had lipid emulsion available before the publication of the ASRA guidelines.

There are several limitations to this survey. Although the response rate was acceptable (69%), the possibility of responder bias remains; survey responders may be more likely to have lipid emulsion available than nonresponders. We did not collect institutional information from nonresponders; therefore, nonresponders could have differed demographically from those who chose to respond to the survey. Because this survey did not assess lipid emulsion availability in the community setting, the external validity of the study is limited to academic obstetric units. In addition, we acquired no data regarding the effectiveness or outcomes after the use of lipid emulsion for LAST. Also, these data provide no indication as to whether there is a relationship between annual deliveries and lipid emulsion availability or guideline availability. Finally, because a high percentage of units had lipid emulsion available, regression analysis could not be performed to evaluate characteristics associated with nonadoption.

The availability of lipid emulsion is a patient safety issue, because it may be a potential antidote in the treatment of LAST. Most academic obstetric units in the United States have implemented systems to ensure that lipid emulsion is available and used them appropriately in the unlikely event of LAST on the labor and delivery units.

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RECUSE NOTE

Dr. Cynthia Wong is the Section Editor for Obstetric Anesthesiology for the Journal. This manuscript was handled by Dr. Steven L. Shafer, Editor-in-Chief, and Dr. Wong was not involved in any way with the editorial process or decision.

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DISCLOSURES

Name: Paloma Toledo, MD, MPH.

Contribution: This author helped design and conduct the study, analyze the data, and write the manuscript.

Attestation: Paloma Toledo has seen the original study data, reviewed the analysis of the data, approved the final manuscript, and is the author responsible for archiving the study files.

Name: Heather C. Nixon, MD.

Contribution: This author helped design and conduct the study, analyze the data, and write the manuscript.

Attestation: Heather Nixon has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Jill M. Mhyre, MD.

Contribution: This author helped design the study, analyze the data, and write the manuscript.

Attestation: Jill M. Mhyre has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Cynthia A. Wong, MD.

Contribution: This author helped design and conduct the study, and write the manuscript.

Attestation: Cynthia A. Wong has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

Name: Guy Weinberg, MD.

Contribution: This author helped design and conduct the study, and write the manuscript.

Attestation: Guy Weinberg has seen the original study data, reviewed the analysis of the data, and approved the final manuscript.

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REFERENCES

1. Mulroy MF. Systemic toxicity and cardiotoxicity from local anesthetics: incidence and preventive measures. Reg Anesth Pain Med. 2002;27:556–61

2. Weinberg GL, VadeBoncouer T, Ramaraju GA, Garcia-Amaro MF, Cwik MJ. Pretreatment or resuscitation with a lipid infusion shifts the dose-response to bupivacaine-induced asystole in rats. Anesthesiology. 1998;88:1071–5

3. The Association of Anaesthetists of Great Britain & Ireland. . Guidelines for the management of severe local anesthetic toxicity. Available at: http://www.aagbi.org/publications/guidelines/docs/latoxicity07.pdf. Accessed July 29, 2010

4. Rosenblatt MA, Abel M, Fischer GW, Itzkovich CJ, Eisenkraft JB. Successful use of a 20% lipid emulsion to resuscitate a patient after a presumed bupivacaine-related cardiac arrest. Anesthesiology. 2006;105:217–8

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6. Weinberg GL, Di Gregorio G, Ripper R, Kelly K, Massad M, Edelman L, Schwartz D, Shah N, Zheng S, Feinstein DL. Resuscitation with lipid versus epinephrine in a rat model of bupivacaine overdose. Anesthesiology. 2008;108:907–13

7. The Association of Anaesthetists of Great Britain & Ireland.. AAGBI safety guideline: management of severe local anaesthetic toxicity. Available at: http://www.aagbi.org/publications/guidelines/docs/la_toxicity_2010.pdf. Accessed July 29, 2010

8. Neal JM, Bernards CM, Butterworth JF 4th, Di Gregorio G, Drasner K, Hejtmanek MR, Mulroy MF, Rosenquist RW, Weinberg GL. ASRA practice advisory on local anesthetic systemic toxicity. Reg Anesth Pain Med. 2010;35:152–61

9. Vanden Hoek TL, Morrison LJ, Shuster M, Donnino M, Sinz E, Lavonas EJ, Jeejeebhoy FM, Gabrielli A. Part 12: cardiac arrest in special situations: 2010 American Heart Association Guidelines for Cardiopulmonary Resuscitation and Emergency Cardiovascular Care. Circulation. 2010;122:S829–61

10. Spence AG. Lipid reversal of central nervous system symptoms of bupivacaine toxicity. Anesthesiology. 2007;107:516–7

11. Griffiths JD, Barron FA, Grant S, Bjorksten AR, Hebbard P, Royse CF. Plasma ropivacaine concentrations after ultrasound-guided transversus abdominis plane block. Br J Anaesth. 2010;105:853–6

12. Smetzer J, Baker C, Byrne FD, Cohen MR. Shaping systems for better behavioral choices: lessons learned from a fatal medication error. Jt Comm J Qual Patient Saf. 2010;36:152–63

13. Williamson RM, Haines J. Availability of lipid emulsion in obstetric anaesthesia in the UK: a national questionnaire survey. Anaesthesia. 2008;63:385–8

14. Picard J, Ward SC, Zumpe R, Meek T, Barlow J, Harrop-Griffiths W. Guidelines and the adoption of “lipid rescue” therapy for local anaesthetic toxicity. Anaesthesia. 2009;64:122–5

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