Original Contribution

Women are less likely than men to receive Prehospital analgesia for isolated extremity injuries

Glen E. Michael MD^a,*, Karl A. Sporer MD^b,c, Glen M. Youngblood^c

^aSchool of Medicine, University of California, San Francisco, CA 94143, USA

^bDepartment of Medicine, Section of Emergency Services, San Francisco General Hospital, University of California,

San Francisco, CA 94110, USA

^cemergency medical services agency, San Mateo County, CA 94403, USA

Received 13 January 2007; revised 25 January 2007; accepted 4 February 2007

Abstract

Objectives: The goal of this study was to examine the effect of socioeconomic factors, such as ethnicity, income, age, and sex, on the administration of analgesia for isolated extremity injuries in the prehospital setting.

Methods: For this retrospective study, the electronic medical record of a large ground-based emergency medical services agency was reviewed and all isolated extremity injuries occurring during the year 2005 were extracted. A total of 1009 cases met the inclusion criteria. Of these cases, 56 were excluded because of incomplete records, leaving 953 cases for analysis. Basic univariate analysis as well as logistic regression analysis were used to examine the relationship between analgesia administration and patient age, ethnicity, sex, income, subjective Pain severity, and time under prehospital care.

Results: A total of 279 patients (29%) received morphine. Both univariate and logistic regression analysis revealed significant differences in analgesia administration based on sex (proportion of men receiving analgesia, 32.8%; women, 26.7%), initial pain severity, and time under prehospital care. Although no category of income was itself significant, a significant trend emerged in which increasing income was associated with increasing likelihood of receiving analgesia. There was no significant difference in analgesia based on patient age or ethnicity.

Conclusion: This study suggests that women are less likely than men to receive prehospital analgesia for isolated extremity injuries. Patients with higher pain severity and longer duration of prehospital care are more likely to receive prehospital analgesia. Increasing levels of income were associated with increased rates of analgesia. The overall rate of prehospital analgesia administration for isolated extremity injuries in this population is higher than has been reported for other emergency medical services systems (29% vs 2%-18% in other recent studies), but there remains considerable room for improvement in the provision of prehospital analgesia. Further inquiry is needed to determine why certain populations such as women receive disproportionately less analgesia.

D 2007

This study was presented at ACEP Scientific Assembly, New Orleans, LA, October 2006.

* Corresponding author. 513 Parnassus Ave, Box 0454, San Francisco, CA 94143-0454, USA.

E-mail address: [email protected] (G.E. Michael).

0735-6757/$ - see front matter D 2007 doi:10.1016/j.ajem.2007.02.001

Introduction

Background

Most patients seeking emergency medical assistance via 911 do so for painful conditions. The provision of analgesia is thus an important role for Prehospital providers. Oligoanalgesia, the inadequate provision of analgesia for patients in pain, is prevalent in the prehospital setting [1-6]. Although socioeconomic disparities in health care have been widely documented, there is no clear consensus on the extent or even existence of socioeconomic and sex-based disparities in current analgesic practices [7-12]. Previous studies examining the role of socioeconomic factors and sex in the provision of analgesia within the emergency department (ED) have produced conflicting results [13-20].

Importance

An extremely small number of studies have examined the role that socioeconomic factors play in prehospital care, and these few studies have supported the existence of socioeco- nomic disparities in prehospital care [21,22]. To our knowledge, no prior study has examined the role of socioeconomic status in prehospital analgesia. The role of sex in prehospital analgesia is also poorly studied, with very few studies, all with extremely small numbers of patients receiving analgesia, investigating this subject [1,3,6].

Goals of this investigation

Given the prevalence of oligoanalgesia in the prehospital setting, and the knowledge that socioeconomic factors and sex may contribute to variation in analgesic practices in the ED, we sought to examine the role that these factors play in prehospital analgesia for patients with isolated extremity injuries.

Materials and methods

Setting

The study was conducted in San Mateo county, an urban/ suburban region with a population of 700000 and a size of 552 mi². The county emergency medical services (EMS) sys- tem responds to approximately 40000 calls annually. All calls receive Advanced life support response under a tiered system consisting of a fire department single paramedic first response team and a paramedic/emergency medical technician staffed private transport ambulance working under county protocols. An electronic prehospital care record is generated for each patient receiving medical attention. This record includes data regarding patient demographics, medical history, clinical signs and symptoms, and paramedic interventions.

Selection of participants

In this retrospective cohort study, we analyzed all cases of isolated extremity injury within the San Mateo county EMS

system that occurred from January 1, 2005, to December 31, 2005. An isolated extremity injury was defined as a suspected fracture, dislocation, or laceration to the upper or lower extremity with no other obvious head, chest, or Abdominal injury. Consistent with the EMS system’s pain management protocol, which is reproduced in Fig. 1, patients with head trauma, altered mental status, or systolic blood pressure lower than 90 mm Hg were not included.

Data collection and processing

A total of 1009 cases meeting the inclusion criteria were identified. Of these, 56 had missing data and were excluded. For each of the remaining 953 cases, we retrieved data on patient age, ethnicity, sex, initial pain severity score (0-10), total time under prehospital management, and whether Intravenous morphine was administered. The home address of each patient was linked to the corresponding US census block group, and the block group median Household income was used as a proxy to estimate patient income [23]. The

Fig. 1 Overview of San Mateo EMS pain management protocol.

data were then stratified into categories for the purpose of meaningful interpretation. Age was divided into adult (18- 64 years), pediatric (b18 years), and geriatric (z65 years) groups. Income was stratified into categories based on multiples of the current US poverty level for a 4-person household ($20,000) [24].

Table 2 Results of logistic regression analysis

Income ($)

z100000^b

80000 to b100000

60000 to b80000

143

130

300

-

1.03 (0.54-1.94)

0.72 (0.42-1.22)

Prehospital time (min)

20 to b40^b b20

z40

616

99

238

-

0.19 (0.08-0.46)^c

2.56 (1.73-3.79)^c

^a For odds ratios, a value greater than 1 indicates a greater likelihood of receiving analgesia.

^b Reference group for statistical comparisons.

^c Confidence interval does not include 1.00.

	n	Odds ratioa (95% CI)
Sex Womenb	550	-
Men	403	1.65 (1.16-2.36)c

Primary data analysis

We conducted basic univariate statistical analysis to determine the relationship between analgesia administration and patient age, ethnicity, sex, estimated income, subjective pain severity, and time under prehospital care. Trend analysis was performed using the Cochran-Armitage test

40000 to b60000	324	0.68 (0.40-1.16)
20000 to b40000	46	0.47 (0.19-1.18)
b20000	10	0.00 (0.00-N10)
Pain score
10b	175	-
0	341	0.02 (0.01-0.04)c
1-3	63	0.02 (0.00-0.05)c
4-6	183	0.08 (0.05-0.14)c
7-9	191	0.25 (0.16-0.40)c

[25] for trend. Logistic regression analysis was then performed to control for possible confounding by any of the aforementioned variables that reached a predetermined significance level ( P b .25) [26]. Statistical analysis was conducted with SPSS software (13.0; Chicago, Ill). This

study was approved by the committee on human research of the University of California, San Francisco.

Table 1 Results of basic statistical analysis

n

Proportion

receiving analgesia (%)

Relative risk

(95% CI)^a

Ethnicity

prehospital time (min)

^a For Relative risks, a value greater than 1 indicates a greater likelihood of receiving analgesia.

^b Reference group for statistical comparisons.

^c Confidence interval (CI) does not include 1.00.

Whiteb	469	29.6	-
African American	51	19.6	0.66 (0.37-1.17)
Asian	64	26.6	0.90 (0.58-1.38)
Hispanic	112	33.9	1.14 (0.85-1.54)
Other/unknown	257	29.2	0.98 (0.78-1.25)
Sex Womenb	550	26.7	-
Men	403	32.8	1.23 (1.01-1.49)c
Income ($) z100000b	143	35.0	-
80000 to b100000	130	33.1	0.95 (0.68-1.32)
60000 to b80000	300	28.0	0.80 (0.60-1.07)
40000 to b60000	324	27.8	0.79 (0.60-1.06)
20000 to b40000	46	26.1	0.75 (0.44-1.27)
b20000	10	0.0	0.00 (0.00-N10)
Age (y)
18-64b	490	28.0	-
b18	106	36.8	1.13 (0.99-1.75)
z65	357	31.4	1.12 (0.91-1.38)
Pain score
10b	175	73.7	-
0	341	6.7	0.09 (0.06-0.13)
1-3	63	4.8	0.07 (0.02-0.20)c
4-6	183	20.8	0.28 (0.21-0.38)c
7-9	191	45.0	0.61 (0.51-0.73)c

Results

A total of 279 (29%) patients received morphine. The results of univariate analysis, displayed in Table 1, revealed significant differences in analgesia administration based on sex, initial pain severity, and time under prehospital care. Income, although not significant in any individual category, followed a significant trend wherein increasing income was associated with increasing likelihood of receiving analgesia (Cochran-Armitage test for trend: v² = 5.31, P = .02). There was no significant difference in analgesia based on age or ethnicity.

As shown in Table 2, multiple logistic regression analysis was then performed to control for possible confounding by any of the aforementioned variables that reached the predetermined level of significance of P b.25. The variables included in the model based on this criterion were sex, income, pain score, and duration of prehospital care. After controlling for these potential confounders, the analysis revealed a persistent significant difference in analgesia administration based on sex, pain severity, and time under prehospital care. The Hosmer-Lemeshow goodness-of-Fit test indicated that the logistic model suitably fit the data (v² = 4.91, P = .77), and the likelihood ratio test further supported the significance of the covariates (sex: v² =

20 to b40b	616	26.6	-
b20	99	7.1	0.27 (0.13-0.55)c
z40	238	45.4	1.70 (1.41-2.06)c

2

7.69, P = .006; pain score: v = 296.56, P b .001;

prehospital time: v² = 48.02, P b .001). Once again, income was not significant for any individual category, but revealed a significant trend in which increasing income was correlated with increasing likelihood of receiving analgesia (likelihood ratio test for income: v² = 5.41, P = .02).

Discussion

This study reveals that female sex is a risk factor for oligoanalgesia in the prehospital setting, even after control- ling for potential confounders. Although sex-specific differ- ences in pain perception, pain pathophysiology, and analgesia response have been documented in the literature, we know of no previous study that has found sex to be a significant risk factor for oligoanalgesia in the prehospital setting [27]. Although analgesia has been extensively studied in the prehospital setting, very few of these studies have examined the impact of sex on analgesia administra- tion [1-6,28,29]. The few studies on prehospital analgesia that have reported data on sex have not revealed significant differences in analgesia rates between men and women. However, these studies were very small-each with fewer than 25 patients receiving analgesia-and thus were likely underpowered [1,3,6]. Studies examining the role of sex on analgesia in the ED are also small in number. However, one previous study conducted in the ED found that, in contrast to the results of this study, women received stronger analgesics than men for painful conditions while in the ED [18]. It is interesting to note that the authors in this referenced study did not examine whether enrolled subjects had received prehospital analgesia before arriving in the ED. The authors’ findings that women were more likely to receive strong analgesia in the ED and that women complained of more severe pain upon presentation to the ED could both be partially accounted for by a relative lack of prehospital analgesia provided to women in the popula- tion studied. Potential explanations for the apparent sex disparity in prehospital analgesic practice require further study, and may include sex-based differences in the prehospital presentation of pain or simply discrimination in paramedic analgesic practices.

In the case of patient income, a clear trend emerged in which each successively lower income group had a reduced likelihood of receiving analgesia. Although no individual income group had a relative risk with a 95% CI entirely lower than 1, the overall trend was significant. We know of no other study in the medical literature specifically investigating the relationship between patient income and oligoanalgesia, but, given the trend demonstrated in this study, further inquiry into this subject in a larger patient population seems worthwhile.

The other significant findings of this study demonstrate a correlation between prehospital analgesia administration and both patient pain score and time under prehospital care. The relationship between pain score and analgesia

administration was an expected finding. The correlation between time under prehospital care and analgesia admin- istration is also not surprising; however, the basis of this relationship is less certain. One plausible explanation for this correlation is that scenarios requiring a longer duration of prehospital care such as long transport distances or prolonged scene times due to vehicle extrication simply provide paramedics with increased time and opportunity to administer analgesics. Alternatively, this correlation may indicate that the administration of analgesia by paramedics significantly prolongs time spent under prehospital care.

Although there were no significant differences in this study when examining the role of patient age or ethnicity with regard to prehospital analgesia administration, some interesting observations can nonetheless be made. Previous studies examining the relationship between patient age and prehospital analgesia have produced inconsistent results. However, several authors have reported that pediatric and Geriatric patients, particularly those at the extremes of age, are at increased risk for oligoanalgesia in the prehospital setting [6,29]. Conversely, in this study population both pediatric and geriatric patients were actually more likely, although not significantly so, than those aged 18 to 64 years to receive prehospital analgesia. The extremes of age were not separately examined in the statistical model of this study; however, an ad hoc glance at the data reveals varied results; 18 (36%) of 50 patients older than 90 years received prehospital analgesia, compared to 1 (14%) of 7 for patients younger than 5 years.

In this study, there was no significant difference in analgesia administration between ethnic groups. Although not statistically significant, African Americans in this study population were less likely than whites to receive preho- spital analgesia (19.6% vs 29.6%). Considering the small number of African American subjects in this study, the lack of a significant difference could reflect a type II error. Although we believe this is the first study to examine the correlation between ethnicity and analgesia administration in the prehospital setting, this topic has previously been investigated in the ED, where findings have been inconsis- tent. In 2000, Todd et al [16] published a study finding that whites were 1.8 times more likely than African Americans to receive analgesia in the ED for similar injuries. Two years later, a validation study by Fuentes et al [13] found no difference in analgesic administration between whites and African Americans. Given the small number of African American patients in this study, and the contradictory findings of similar studies conducted in the ED, further inquiry into potential Ethnic disparities in prehospital analgesia may be warranted.

Although the Sex disparities in prehospital analgesia identified by this study are a cause for some concern and require further investigation, the results also reveal a higher overall rate of prehospital analgesia than has previously been reported. The overall rate of prehospital analgesia administration in this study population was 29%, compared

to previous studies finding prehospital analgesia rates ranging from 2% to 18% for similar injuries [1-3,6]. Although 29% is still a suboptimal rate of analgesia for painful injuries, this is nonetheless a higher rate than has been previously reported, and may reflect increasing attention to the importance of prehospital analgesia over time, or a geographic or system-based variation in preho- spital analgesia practices.

Limitations

This retrospective study was subject to a number of limitations that should be noted. First, the study of socioeconomic disparities is fraught with the potential for error from confounding variables. We sought to minimize this by controlling for covariates that we thought might confound our results, but it is possible that we did not include all such variables. The study of pain and analgesia is similarly nebulous and is also subject to confounding. We again sought to control for this by including pain score as a covariate, by excluding hypotensive patients, and by including only patients with isolated extremity injuries. However, beyond limiting the study population to patients who only had isolated extremity injuries, we did not control for specific injury type. Because certain injuries may be more responsive to nonopioid pain management techniques such as immobilization, or may be more or less painful than other injuries in a way that is not entirely captured by the pain score, not controlling for specific injury type may have skewed our results. Patient refusal of pain medication or paramedic inability to obtain intravenous access may also have confounded our results, because we were unable to retrieve this information from the patient care records. Finally, we simply assessED analgesia as a dichotomous yes- or-no variable. We thus may have missed some important differences that would only be appreciable by looking at the specific dose of analgesia that each patient received. For example, certain age groups may have been less likely to receive adequate weight-based doses of analgesia, but our study design would not have captured such a discrepancy.

Another potential limitation of this study is that the data were entirely obtained from an electronic patient care record in a retrospective fashion. It is possible that errors were made or bias was introduced when paramedics were entering data into the electronic record. However, the paramedics had no knowledge of this study and it is unlikely that their frequency of data entry errors was greater for a particular sex or socioeconomic group.

We sought to include only those patients for whom morphine administration was indicated based on the EMS system’s prehospital pain management protocol. We thus excluded patients who were documented to have head injuries, an Altered level of consciousness, or hypotension. However, some of the patients included in the study may not have received analgesia for valid clinical reasons that simply

were not reflected in the electronic patient care record. Similarly, although we excluded patients who were hypo- tensive, we did not control for patient blood pressure in our statistical model. It may be that paramedics are less likely to administer morphine to patients who have relatively low blood pressures, even if they are not technically hypotensive and even though the pain management protocol allows the administration of morphine for any systolic blood pressure higher than 90 mm Hg. Blood pressure is therefore a possible confounding variable that was not completely controlled for in this study.

Finally, our method for estimating patient income has not been validated and thus may have introduced error into our results. We matched each patient’s home address to the corresponding census block group, and then used the Median household income for the census block group as a proxy for patient household income. On average, each census block group contains approximately 1500 geograph- ically related individuals. Because the block group is the smallest geographic grouping from the 2000 US census for which median household income data are available, we believe this method to be the best possible approach to estimating patient income in this type of study.

Conclusion

This study suggests that women are less likely than men to receive prehospital analgesia for isolated extremity injuries. There also appears to be an association between patient income and likelihood of receiving analgesia, as a trend emerged wherein increases in income correlated with increasing likelihood of receiving analgesia. Patients with higher pain severity and longer duration of prehospital care were more likely to receive prehospital analgesia. Differ- ences in patient age and ethnicity did not significantly impact the administration of prehospital analgesia. Further inquiry is necessary to better understand the reason for disproportionately low analgesia administration among women, and to better elucidate the impact of patient income on prehospital analgesia practices.

References

1. Abbuhl FB, Reed DB. time to analgesia for patients with painful extremity injuries transported to the emergency department by ambulance. Prehosp Emerg Care 2003;7(4):445 - 7.
2. Hennes H, Kim MK, Pirrallo RG. Prehospital pain management: a comparison of providers’ perceptions and practices. Prehosp Emerg Care 2005;9(1):32 - 9.
3. McEachin CC, McDermott JT, Swor R. Few emergency medical services patients with lower-extremity fractures receive prehospital analgesia. Prehosp Emerg Care 2002;6(4):406 - 10.
4. McLean SA, Maio RF, Domeier RM. The epidemiology of pain in the prehospital setting. Prehosp Emerg Care 2002;6(4):402 - 5.
5. McManus Jr JG, Sallee Jr DR. Pain management in the prehospital environment. Emerg Med Clin North Am 2005;23(2):415 - 31.
6. White LJ, Cooper JD, Chambers RM, Gradisek RE. Prehospital use of analgesia for suspected extremity fractures. Prehosp Emerg Care 2000;4(3):205 - 8.
7. Biros MH, Adams JG, Cone DC. Executive summary: disparities in emergency health care. Acad Emerg Med 2003;10(11):1153 - 4.
8. Blanchard JC, Haywood YC, Scott C. Racial and ethnic disparities in health: an emergency medicine perspective. Acad Emerg Med 2003;10(11):1289 - 93.
9. Cone DC, Richardson LD, Todd KH, Betancourt JR, Lowe RA. Health care disparities in emergency medicine. Acad Emerg Med 2003;10(11):1176 - 83.
10. Richardson LD, Irvin CB, Tamayo-Sarver JH. Racial and ethnic disparities in the clinical practice of emergency medicine. Acad Emerg Med 2003;10(11):1184 - 8.
11. Smedley BD, Stith AY, Nelson AR. Institute of Medicine (U.S.). Committee on Understanding and Eliminating Racial and Ethnic Disparities in Health Care. Unequal treatment: confronting racial and ethnic disparities in health care. Washington (DC)7 National Academy Press; 2002.
12. United States Agency for Healthcare Research and Quality. National healthcare disparities report. Rockville (Md)7 U.S. Department of Health and Human Services, Agency for Healthcare Research and Quality; 2004.
13. Fuentes EF, Kohn MA, Neighbor ML. Lack of association between patient ethnicity or race and fracture analgesia. Acad Emerg Med 2002;9(9):910 - 5.
14. Heins JK, Heins A, Grammas M, Costello M, Huang K, Mishra S. Disparities in analgesia and opioid prescribing practices for patients with Musculoskeletal pain in the emergency department. J Emerg Nurs 2006;32(3):219 - 24.
15. Tamayo-Sarver JH, Hinze SW, Cydulka RK, Baker DW. Racial and ethnic disparities in emergency department analgesic prescription. Am J Public Health 2003;93(12):2067 - 73.
16. Todd KH, Deaton C, D’Adamo AP, Goe L. Ethnicity and analgesic practice. Ann Emerg Med 2000;35(1):11 - 6.
17. Todd KH, Samaroo N, Hoffman JR. Ethnicity as a risk factor for inadequate emergency department analgesia. JAMA 1993;269(12): 1537 - 9.
18. Raftery KA, Smith-Coggins R, Chen AH. Gender-associated differ- ences in emergency department pain management. Ann Emerg Med 1995;26(4):414 - 21.
19. Tamayo-Sarver JH, Dawson NV, Hinze SW, et al. The effect of race/ethnicity and desirable social characteristics on physicians’ decisions to prescribe opioid analgesics. Acad Emerg Med 2003; 10(11):1239 - 48.
20. Todd KH, Lee T, Hoffman JR. The effect of ethnicity on physician estimates of pain severity in patients with isolated extremity trauma. JAMA 1994;271(12):925 - 8.
21. Brice JH, Yealy DM. Socioeconomic status and out-of-hospital delay. Ann Emerg Med 2003;41(4):491 - 3.
22. Govindarajan A, Schull M. Effect of socioeconomic status on out-of- hospital transport delays of patients with chest pain. Ann Emerg Med 2003;41(4):481 - 90.
23. United States Census Bureau. Census 2000, summary file 3. Generated by Glen E Michael; using American Factfinder; 2000. bhttp://factfinder.census.govN.
24. United States Department of Health and Human Services. Annual update of the HHS poverty guidelines. Fed Regist 2006;71(15):3848.
25. Cochran WG. Some methods for strengthening the common chi- square tests. Biometrics 1954;10:417 - 51.
26. Hosmer DW, Lemeshow S. Applied logistic regression. 2nd ed. Wiley7 New York; 2000.
27. Wiesenfeld-Hallin Z. sex differences in pain perception. Gend Med 2005;2(3):137 - 45.
28. Fullerton-Gleason L, Crandall C, Sklar DP. Prehospital administra- tion of morphine for isolated extremity injuries: a change in protocol reduces time to medication. Prehosp Emerg Care 2002; 6(4):411 - 6.
29. Watkins N. Paediatric prehospital analgesia in Auckland. Emerg Med Australas 2006;18(1):51 - 6.