PEDIATRICS Vol. 120 No. 3 September 2007, pp. 461-466 (doi:10.1542/peds.2007-0012)
ARTICLE |
Additional Health Care Visits Needed Among Adolescents for Human Papillomavirus Vaccine Delivery Within Medical Homes: A National Study
Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, New York
 |
ABSTRACT |
|---|
 TOP ABSTRACT METHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
|---|
OBJECTIVE. We estimated the additional number of primary care visits needed to deliver 3 doses of human papillomavirus vaccine to all US adolescents in medical homes. We determined adolescent and family factors associated with needing the greatest number of additional visits for full human papillomavirus vaccination.
METHODS. We performed a cross-sectional analysis of adolescents 11 to 21 years of age included in the 2002 and 2003 Medical Expenditure Panel Surveys (n = 2900) to measure existing primary care visits to pediatricians, family physicians, obstetrician/gynecologists, and internists. We then estimated additional visits needed for human papillomavirus vaccination. We determined the number of additional visits needed within a 6-, 12-, 18-, or 24-month vaccination window.
RESULTS. Within a 12-month period, 72% of female adolescents would need 3 visits for human papillomavirus vaccination if the vaccine was introduced at a preventive visit; 9% and 16% would need 1 and 2 more visits, respectively. Similarly, 79% of male patients would need 3 visits; 7% and 12% would need 1 and 2 more visits, respectively. If all opportunities to vaccinate were used, then 41% of female patients and 52% of male patients would need 3 additional visits within 12 months. With expansion of the window to 24 months and vaccination at every possible visit, 23% of female patients and 37% of male patients would need 3 additional visits. Factors that predicted needing more visits (2 or 3 vs 0 or 1 in 24 months) included being older, male, black, Hispanic, uninsured, and near-poor.
CONCLUSIONS. Most adolescents would require 2 or 3 additional primary care visits to receive 3 vaccines for human papillomavirus in the medical home. Strategies to minimize additional visits include vaccinating patients at all primary care visits and encouraging annual preventive visits.
Key Words: adolescent health • utilization of services • health services research • immunizations
Abbreviations: HPV—human papillomavirus
Human papillomavirus (HPV) is the most common sexually transmitted infection in the United States, with a prevalence of 27% among women 14 to 59 years of age.1 Three doses of a vaccine to prevent infection with the most commonly carcinogenic HPV types (types 16 and 18), as well as the types associated with most genital warts (types 6 and 11), were recommended recently by the Advisory Committee on Immunization Practices for 11- to 12–year-old girls and for female adolescents 13 to 26 years of age who had not been vaccinated previously.2 This quadrivalent vaccine was shown to be 100% effective over 5 years in preventing precancerous cervical lesions caused by HPV types 6, 11, 16, and 18 when delivered with a dosing schedule of 0, 2, and 6 months.3 A second vaccine to prevent types 16 and 18, which is expected to be licensed in the near future, seems equally efficacious.4 Although it is not currently known how well antibody levels correlate with clinical protection, 1 HPV vaccination offers some immune response, 2 provide much higher antibody levels, and 3 are recommended to provide individuals with the best protection and longest duration of immunity.5
A number of possible sites for vaccination have been discussed,6,7 but it is generally assumed that primary care practices or medical homes will be the major sites for HPV vaccination and that additional visits will be required for full HPV vaccination. However, no studies have described, on a national level, the proportion of adolescents who currently make sufficient primary care visits to receive 3 vaccines for HPV within the recommended time frames or the proportions of those who would need 1, 2, or 3 additional visits to be fully vaccinated. Currently, most vaccinations for adolescents are provided during routine preventive visits to either pediatricians or family physicians.6 Few adolescents make >1 preventive visit annually, and the proportions who make even 1 visit in a year range from 34% to 82% (depending on the source).8–10 Therefore, HPV vaccine may place a significant burden on primary care providers to ensure 3 separate visits in a timely manner. Better understanding of this challenge should allow primary care clinicians to plan strategies for vaccinating large populations of eligible adolescents.
Our first objective was to determine the proportions of adolescents across the United States who would need 0, 1, 2, or 3 additional visits to complete the HPV series within primary care settings, assuming current utilization patterns. Although the vaccine is not yet approved for boys, ongoing clinical trials are evaluating HPV vaccine efficacy for boys11; therefore, visits were examined for both genders. We considered various windows of time to complete the 3-dose series. We hypothesized that the majority of adolescents would require 2 or 3 additional visits to complete the HPV series. Our second objective was to assess adolescent and family factors associated with needing the greatest number of additional visits for full vaccination. It is important to identify subgroups of adolescents who will need more aggressive outreach to receive a full HPV vaccine series. We hypothesized that adolescents who are male, older, and uninsured would be more likely to need a greater number of visits, compared with those who are female, younger, and insured.
|
METHODS |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
|---|
Setting and Database
The Medical Expenditure Panel Survey is a national probability survey of the noninstitutionalized civilian population of the United States that is conducted annually by the Agency for Healthcare Research and Quality.12 The survey includes household, medical provider, and insurance components. The household component, which collects data about individuals' health status, medical services used, and health insurance coverage, was used for our analyses. Survey administrators use the medical provider component for a subsample of individuals surveyed, to verify medical care events. Data are collected for the survey through an initial contact followed by 6 subsequent interviews over a 2.5-year period. A parent or other knowledgeable adult in the household answers questions about health service use for children <17 years of age, and individuals
17 years of age answer the questions themselves.
Study Design
We selected a cohort of adolescents included in the 2002 and 2003 Medical Expenditure Panel Surveys and counted outpatient visits by adolescents to primary care providers (pediatricians, family physicians, internists, and obstetrician/gynecologists) in any outpatient setting other than an emergency department. We used these visit patterns to estimate the number of HPV vaccinations that could have been administered to eligible adolescents on the basis of their actual utilization of primary care. Because vaccinations are offered traditionally at preventive visits,6 when a physician may be more likely to explain a new vaccine, we counted visits with 2 potential scenarios for HPV vaccination, that is, (1) the first vaccine is administered during a preventive visit and (2) the first vaccine is administered during any type of primary health care visit. In both scenarios, the second and third vaccines were assumed to be offered at any visit. Additional visits were counted if the second visit was 1 month after the first primary care visit and the third visit was 3 months after the second visit (on the basis of the timetable for the first Food and Drug Administration-approved HPV vaccine).2 We applied various time windows (6, 12, 18, and 24 months, starting January 1) for vaccination with all 3 doses, to determine how many more visits adolescents would need given longer periods of time to receive 3 vaccinations. We obtained approval for these analyses from the institutional review boards of the University of Rochester and the Centers for Disease Control and Prevention.
Variables
Independent Variables
Preventive visits were defined as parent/adolescent-reported visits for a "general checkup." We categorized age as early (11–14 years), middle (15–17 years), and late (18–21 years) adolescence, on the basis of the Bright Futures definitions of adolescent developmental stages.13 Income was defined as nonpoor (>200% of federal poverty level), near-poor (100%–200% of federal poverty level), or poor (<100% of federal poverty level). Other independent variables examined were gender, race (white, black, or other), ethnicity (Hispanic or non-Hispanic), and insurance status (insured or uninsured).
Dependent Variables
The outcome measured was the additional number of visits needed to receive 3 HPV vaccines, ranging from 0 visits (adolescents who had 3 visits at appropriate intervals) to 3 visits (individuals who had no visits).
Statistical Analyses
Tabular analyses summarized the proportions of adolescents and subgroups of adolescents who would require 0, 1, 2, or 3 additional visits beyond health care visits already made; 
2 tests compared characteristics of adolescents associated with needing more (2 or 3) versus fewer (0 or 1) additional visits, applying 12- and 24-month windows of opportunity for vaccination. Logistic regression analyses, which included variables significant at P < .05 in bivariate analyses, assessed characteristics of adolescents associated independently with needing more visits within 12 or 24 months. SUDAAN 9.014 was used to account for the complex sampling design and to provide national estimates. All analyses were based on weighted data.
|
RESULTS |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
|---|
Population Characteristics
A total of 2900 adolescents 11 to 21 years of age were monitored for the 2 calendar years (2002–2003) of the Medical Expenditure Panel Survey. Most adolescents were white, non-Hispanic, insured, and nonpoor (Table 1). Overall, 38% of adolescents had preventive visits in the 24-month period surveyed, with rates ranging from 23% (for 20-year-old subjects) to 48% (for 15-year-old subjects).
|
Additional Numbers of Visits for Female Patients
Scenario 1: Assuming First Vaccine at Preventive Visit
With a 6-month window for vaccination and administration of the first HPV vaccine at a preventive visit, only 0.3% of female adolescents would have sufficient visits to receive 3 vaccines for HPV and 86% would need 3 visits. Expanding the vaccination window to 12, 18, and 24 months would enable 3%, 9%, and 14% of female patients, respectively, to be fully vaccinated, but 72%, 64%, and 56% would still require 3 additional visits (Fig 1A).
|
Scenario 2: Assuming First Vaccine at Any Visit
If we used all opportunities to vaccinate female adolescents at any type of primary health care visit, then 1% of female adolescents would have sufficient visits within a 6-month window to receive 3 vaccines and 60% would need 3 additional visits (Fig 1B). With expansion of the interval to 12, 18, and 24 months, 10%, 22%, and 32% of female adolescents, respectively, would have 3 visits spaced appropriately for HPV vaccine, but 41%, 31%, and 23% would still require 3 additional visits. Provision of HPV vaccine during any available visit reduced markedly the number of additional visits needed for full vaccination.
Additional Numbers of Visits for Male Patients
Scenario 1: Assuming First Vaccine at Preventive Visit
Only 0.1% of male adolescents had sufficient visits within 6 months. Given 12, 18, and 24 months, 1%, 5%, and 9%, respectively, had sufficient visits with appropriate intervals between visits (Fig 2A).
|
Scenario 2: Assuming First Vaccine at Any Visit
With vaccination at any primary care visit, 1%, 6%, 13%, and 19% had sufficient visits within 6-, 12-, 18-, and 24-month windows, respectively. With the most-generous 24-month window, 37% would still require 3 additional visits (Fig 2B).
Characteristics of Adolescents Needing More Visits
By using bivariate analyses, we found that adolescents who were older, male, black, Hispanic, uninsured, and near-poor were more likely to need a greater number of visits, even with a 24-month window (Table 2). Results were similar if a shorter window for vaccination was used. In regression analyses controlling for age group, gender, race, ethnicity, insurance, and income, factors associated with needing more (2 or 3) versus fewer (0 or 1) visits within 12 or 24 months mirrored those noted in bivariate analyses and included being near-poor, older (significant for the 24-month window only), male, black, Hispanic, and uninsured (24-month window) (Table 2).
|
|
DISCUSSION |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
|---|
Overall Findings
Currently, most adolescents do not have sufficient primary care visits to receive 3 doses of vaccine within the recommended 6-month time frame, particularly if the initial vaccine is delivered at a preventive visit. Even if all primary health care visits were used to start the vaccination series for eligible adolescents, the vast majority would still require 2 or 3 additional visits. Longer vaccination windows would reduce the number of adolescents requiring additional visits. Male patients would need more visits than female patients, particularly at older ages. Adolescents who would need the greatest number of additional visits include those who are black, Hispanic, uninsured, and near-poor. These results highlight the need for implementing efficient vaccination strategies.
Avoiding Missed Opportunities
Traditionally, health care providers administer the majority of vaccinations at preventive visits for both young children and adolescents.6,15 Because adolescents have fewer preventive visits, compared with young children,16 and the recommended vaccine schedule has expanded, a new approach should be taken for adolescents to be fully vaccinated. Almost 70% of adolescents have some type of primary care visit within 12 months, affording at least 1 opportunity for HPV vaccination. Although reducing missed opportunities is important for infants and toddlers,17–22 it may be even more critical for adolescent immunizations.
High-Risk Groups
Our study shows that, similar to the case for young children,23–26 adolescents who are male, black, Hispanic, uninsured, and near-poor currently make fewer primary care visits; these groups would need a greater number of additional visits to be fully vaccinated for HPV. Among college students, Hispanic and black female students have increased risk of HPV,27 which, together with a lack of visits, puts them at particular risk for persistent infection.
Potential for Additional Preventive Visits
Although the American Academy of Pediatrics,28 the American Medical Association,29 and Bright Futures13 recommend preventive visits for adolescents, 62% of adolescents in this study did not have a preventive visit within 24 months. Delivery of a HPV vaccine provides an ideal entrée into discussion of sexual health risks, including HIV. Reminder/recall methods that improve rates of early childhood vaccination30 have been shown to increase other preventive services, including receipt of health supervision visits, anemia screening, and lead testing.31 By emphasizing the need for immunizations during adolescence, health care providers may create more opportunities for preventive visits, as well as other counseling and screening measures.
Visits Elsewhere
Our study highlights the challenge of vaccinating adolescents within primary care medical homes. If strict windows of time are required to receive 3 vaccines, then it may be necessary to consider the possibility of vaccinating patients in alternative settings as an adjunct to the medical home. Programs coordinating public health agencies with schools have delivered vaccines successfully to adolescents in school settings in some states.32,33 The feasibility of vaccinating adolescents with a HPV vaccine outside the medical home (in family planning clinics, pharmacies, or emergency departments) has not yet been evaluated but should be examined as a potential method to increase completed rates of vaccination. The use of immunization registries connected to multiple sites could alleviate concern regarding delivery of unnecessary vaccine doses.
Intervals Between Visits
Our study imposed a theoretical window of time to receive 3 doses of vaccine, but the HPV vaccine being currently marketed has not been studied with delivery intervals of >12 months. Ideally, adolescents would be vaccinated in the shortest time possible to be protected from HPV infection. If 3 doses can be given before sexual activity occurs, however, then the longer interval provides more time for teens to present for care. We recommend that postmarketing studies examine whether immunizations provided at greater intervals are less protective.
Limitations
We were limited by the definition of "general medical examination," as described by the patient for each visit. It is possible that some visits for preventive care were not described as such by the individuals interviewed. Parents responded for individuals <17 years of age in each household, and adolescents might have had visits for confidential care that were not known to the parent. However, such visits are often to alternative sites of care,34 rather than to medical homes. Our analyses were performed by using data from 2002 to 2003, before HPV vaccine was available and before other adolescent vaccines (meningococcal) were recommended. These visit patterns may not predict future patterns of utilization, given that these vaccines are now available.
|
CONCLUSIONS |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
|---|
Most adolescents do not have sufficient visits to receive 3 HPV vaccinations within 6 months from primary care providers and would require 2 or 3 additional visits for full vaccination. Vaccinating over a longer interval and at every primary care visit would reduce the number of additional visits needed. Individuals who would need more visits, particularly black, Hispanic, and uninsured adolescents, are also those most at risk for HPV-related diseases.1 Additional efforts are needed to reach adolescents for HPV vaccination.
Information is needed about the immunogenicity of the HPV vaccine if it is offered over longer intervals than studied previously. The impact of HPV vaccine delivery (and strategies to enhance HPV vaccination) on receipt of other preventive services should be studied. It will be important to assess whether high-risk groups are reached with the vaccine.
Primary care practitioners should avoid missed opportunities for vaccination, should begin the HPV vaccination series at any primary care visit, and should encourage adolescents to have annual preventive health care visits. Delivery of HPV vaccine presents new challenges to medical homes, as well as opportunities to enhance the delivery of preventive services to our nation's adolescents.
|
ACKNOWLEDGMENTS |
|---|
This work was supported by a cooperative agreement with the Centers for Disease Control and Prevention (agreement U01IP000040).
We thank William Bonnez, MD, of the Department of Infectious Disease, University of Rochester School of Medicine and Dentistry, for his insight into the pathogenicity of HPV and immunologic features of vaccines.
|
FOOTNOTES |
|---|
Accepted Apr 23, 2007.
Address correspondence to Cynthia M. Rand, MD, MPH, Division of General Pediatrics, Box 777, University of Rochester School of Medicine and Dentistry, Rochester, NY 14642. E-mail: cynthia_rand{at}urmc.rochester.edu
This work was presented in part at the annual meeting of the Pediatric Academic Societies; April 29–May 2, 2006; San Francisco, CA.
The authors have indicated they have no financial relationships relevant to this article to disclose.
|
REFERENCES |
|---|
|
TOPABSTRACTMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
|---|
- Dunne EF, Unger ER, Sternberg M, et al. Prevalence of HPV infection among females in the United States.
JAMA. 2007;297
:813
–819
[Abstract/Free Full Text] - Markowitz LE, Dunne EF, Saraiya M, et al. Quadrivalent human papillomavirus vaccine: recommendations of the Advisory Committee on Immunization Practices (ACIP). MMWR Recomm Rep. 2007;56 (RR-2):1–24
- Villa LL, Costa RL, Petta CA, et al. High sustained efficacy of a prophylactic quadrivalent human papillomavirus types 6/11/16/18 L1 virus-like particle vaccine through 5 years of follow-up. Br J Cancer. 2006;95 :1459 –1466[CrossRef][Web of Science][Medline]
- Harper DM, Franco EL, Wheeler CM, et al. Sustained efficacy up to 4.5 years of a bivalent L1 virus-like particle vaccine against human papillomavirus types 16 and 18: follow-up from a randomised control trial. Lancet. 2006;367 :1247 –1255[CrossRef][Web of Science][Medline]
- Villa LL, Ault KA, Giuliano AR, et al. Immunologic responses following administration of a vaccine targeting human papillomavirus types 6, 11, 16, and 18. Vaccine. 2006;24 :5571 –5583[CrossRef][Web of Science][Medline]
- Schaffer SJ, Humiston SG, Shone LP, Averhoff FM, Szilagyi PG. Adolescent immunization practices: a national survey of US physicians.
Arch Pediatr Adolesc Med. 2001;155
:566
–571
[Abstract/Free Full Text] - Humiston SG, Rosenthal SL. Challenges to vaccinating adolescents: vaccine implementation issues. Pediatr Infect Dis J. 2005;24(suppl) :S134 –S140[CrossRef][Web of Science][Medline]
- Klein JD, Wilson KM, McNulty M, Kapphahn C, Collins KS. Access to medical care for adolescents: results from the 1997 Commonwealth Fund Survey of the Health of Adolescent Girls. J Adolesc Health. 1999;25 :120 –130[CrossRef][Web of Science][Medline]
- McInerny TK, Cull WL, Yudkowsky BK. Physician reimbursement levels and adherence to American Academy of Pediatrics well-visit and immunization recommendations.
Pediatrics. 2005;115
:833
–838
[Abstract/Free Full Text] - Yu SM, Bellamy HA, Schwalberg RH, Drum MA. Factors associated with use of preventive dental and health services among US adolescents. J Adolesc Health. 2001;29 :395 –405[CrossRef][Web of Science][Medline]
- Centers for Disease Control and Prevention, National Immunization Program. HPV and HPV vaccine: information for healthcare providers. Available at: www.cdc.gov/std/hpv/STDFact-HPV-vaccine-hcp.htm. Accessed July 5, 2007
- Cohen SB. Sample Design of the 1997 Medical Expenditure Panel Survey Household Component. Rockville, MD: Agency for Healthcare Research and Quality; 2000. AHRQ publication 01–0001
- National Center for Education in Maternal and Child Health. Bright Futures: Guidelines for Health Supervision of Infants, Children, and Adolescents. 2nd ed. Arlington, VA: National Center for Education in Maternal and Child Health; 2002
- Shah BV, Barnwell BV, Bieler GS. SUDAAN User's Manual and Software. Release 9.0 ed. Research Triangle Park, NC: Research Triangle Institute; 2004
- Rand CM, Shone LP, Albertin C, et al. National health care visit patterns of adolescents: implications for delivery of new adolescent vaccines.
Arch Pediatr Adolesc Med. 2007;161
:252
–259
[Abstract/Free Full Text] - Byrd RS, Hoekelman RA, Auinger P. Adherence to AAP guidelines for well-child care under managed care.
Pediatrics. 1999;104
:536
–540
[Abstract/Free Full Text] - Szilagyi PG, Rodewald LE. Missed opportunities for immunizations: a review of the evidence. J Public Health Manag Pract. 1996;2 :18 –25[Medline]
- Santoli JM, Szilagyi PG, Rodewald LE. Barriers to immunization and missed opportunities. Pediatr Ann. 1998;27 :366 –374[Web of Science][Medline]
- Minkovitz CS, Belote AD, Higman SM, Serwint JR, Weiner JP. Effectiveness of a practice-based intervention to increase vaccination rates and reduce missed opportunities.
Arch Pediatr Adolesc Med. 2001;155
:382
–386
[Abstract/Free Full Text] - Sabnis SS, Pomeranz AJ, Amateau MM. The effect of education, feedback, and provider prompts on the rate of missed vaccine opportunities in a community health center.
Clin Pediatr (Phila). 2003;42
:147
–151
[Abstract/Free Full Text] - Daley MF, Beaty BL, Barrow J, et al. Missed opportunities for influenza vaccination in children with chronic medical conditions.
Arch Pediatr Adolesc Med. 2005;159
:986
–991
[Abstract/Free Full Text] - Dombkowski KJ, Davis MM, Cohn LM, Clark SJ. Effect of missed opportunities on influenza vaccination rates among children with asthma.
Arch Pediatr Adolesc Med. 2006;160
:966
–971
[Abstract/Free Full Text] - Klevens RM, Luman ET. US children living in and near poverty: risk of vaccine-preventable diseases. Am J Prev Med. 2001;20 :41 –46[CrossRef][Web of Science][Medline]
- Darling NJ, Barker LE, Shefer AM, Chu SY. Immunization coverage among Hispanic ancestry: 2003 National Immunization Survey. Am J Prev Med. 2005;29 :421 –427[CrossRef][Web of Science][Medline]
- Santoli JM, Huet NJ, Smith PJ, et al. Insurance status and vaccination coverage among US preschool children.
Pediatrics. 2004;113
:1959
–1964
[Abstract/Free Full Text] - Smith PJ, Stevenson J, Chu SY. Associations between childhood vaccination coverage, insurance type, and breaks in health insurance coverage.
Pediatrics. 2006;117
:1972
–1978
[Abstract/Free Full Text] - Ho GY, Bierman R, Beardsley L, Chang CJ, Burk RD. Natural history of cervicovaginal papillomavirus infection in young women.
N Engl J Med. 1998;338
:423
–428
[Abstract/Free Full Text] - American Academy of Pediatrics. Guidelines for Health Supervision III. Elk Grove Village, IL: American Academy of Pediatrics; 1998
- Elster AB, Kuznets NJ. AMA Guidelines for Adolescent Preventive Services (GAPS): Recommendations and Rationale. Baltimore, MD: Williams & Wilkins; 1994
- Szilagyi PG, Bordley C, Vann JC, et al. Effect of patient reminder/recall interventions on immunization rates: a review.
JAMA. 2000;284
:1820
–1827
[Abstract/Free Full Text] - Rodewald LE, Szilagyi PG, Humiston SG, et al. A randomized study of tracking with outreach and provider prompting to improve immunization coverage and primary care.
Pediatrics. 1999;103
:31
–38
[Abstract/Free Full Text] - Cassidy W. School-based adolescent hepatitis B immunization programs in the United States: strategies and successes. Pediatr Infect Dis J. 1998;17(suppl) :S43 –S46[CrossRef][Web of Science][Medline]
- Seid M, Simmes DR, Linton LS, et al. Correlates of vaccination for hepatitis B among adolescents: results from a parent survey.
Arch Pediatr Adolesc Med. 2001;155
:921
–926
[Abstract/Free Full Text] - Civic D, Scholes D, Grothaus L, McBride C. Adolescent HMO enrollees' utilization of out-of-plan services. J Adolesc Health. 2001;28 :491 –496[CrossRef][Web of Science][Medline]
PEDIATRICS (ISSN 1098-4275). ©2007 by the American Academy of Pediatrics
CiteULike 
Connotea 
Del.icio.us 
Digg 
Facebook 
Reddit 
Technorati 
Twitter What's this?
This article has been cited by other articles:
|
|
 |
|
  S. Munte, J. Klockars, M. van Gils, A. Hiller, M. Winterhalter, C. Quandt, M. Gross, and T. Taivainen The Narcotrend Index Indicates Age-Related Changes During Propofol Induction in Children Anesth. Analg., July 1, 2009; 109(1): 53 - 59. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
