Jan Odom- Forren , PhD, RN, CPAN, FAAN 1 Lynne Hall, DrPH , RN 2 Susan Fetzer , PhD, RN 3

1. Psychometric Properties of the Ambulatory Surgery-Inventory of Nausea, Vomiting and Retching (AS-INVR)

2. Jan Odom-Forren, PhD, RN, CPAN, FAAN1 • Lynne Hall, DrPH, RN2 • Susan Fetzer, PhD, RN3 • Christian Apfel, PhD, MD4 • 1College of Nursing, University of Kentucky, Lexington, KY • 2School of Nursing, University of Louisville, Louisville, KY • 3School of Nursing, University of New Hampshire, Durham, NH • 4Anesthesia and Perioperative Care, University of California, San Francisco, CA • Funded by an unrestricted grant from Merck and Co., Inc., North Wales (PA) awarded to University of California, San Francisco and from Dr. Apfel’s Discretionary Fund for the Perioperative Clinical Research Core

3. Purpose • To evaluate the psychometric properties of the AS-INVR in adults who required ambulatory surgery and experienced post discharge nausea and vomiting (PDNV).

4. Background • Over 34 million patients in the U.S. undergo ambulatory surgery each year and PDNV affects 35-55% of outpatients. • Reliable and valid measures of the incidence and severity of PDNV are lacking. • The Ambulatory Surgery-Inventory of Nausea, Vomiting and Retching (AS-INVR) is a short measure of PDNV adapted from the Rhodes Index of Nausea and Vomiting for the ambulatory surgery population. • The psychometric properties of the AS-INVR were evaluated in only one prior study with ambulatory surgery patients.

5. Specific Aims • Explore the dimensionality of the AS-INVR. 2. Examine the internal consistency reliability of the AS-INVR. 3. Evaluate the construct validity of the AS-INVR.

6. Hypothesis Testing for Construct Validity H1: Persons with PDNV will have a higher mean AS-INVR score than those ` without. H2: Higher AS-INVR scores will be associated with lower quality of life scores related to nausea. H3: Higher AS-INVR scores will be associated with lower quality of life scores related to vomiting.

7. Methods • Design and Sample • Multi-site prospective study of a convenience sample of 203 adults after ambulatory surgery from Day of Surgery through Day 5 post-op. • The purpose of the larger study was to identify the incidence and management strategies of adult patients after ambulatory surgery. • Eligible participants were recruited consecutively either in preadmission testing or in the preoperative area on the day of surgery.

8. Inclusion/Exclusion Criteria • Inclusion Criteria • At least 18 years of age or older and undergoing outpatient surgery • Received general anesthesia requiring an endotracheal tube or laryngeal mask anesthesia • Exclusion Criteria • Unable to communicate in English • Transferred to inpatient stay • Current pregnancy • Persistent or recurrent nausea and/or vomiting before anesthesia

9. Measures • Post Discharge Nausea (PDN) Severity • Quality of Life (QOL) • Ambulatory Surgery-Inventory of Nausea, Vomiting and Retching • Sociodemographiccharacteristics • Clinical characteristics

10. Procedure • Protocol approved by Institutional Review Board • Written informed consent obtained • Data collected via phone interview and mailed patient diary

11. Data Analysis • Principal components analysis followed by exploratory factor analysis with Varimax rotation to determine the instrument’s dimensionality • Cronbach’salpha to assess internal consistency reliability. Coefficients greater than .70 were considered to represent good internal consistency. • Independent samples t-test and correlational analysis for hypothesis testing to evaluate construct validity.

12. Results

13. Sample Description • Mean age 55 + SD 15.4; range 23-87 years • Female 72%; Caucasian 93% • Presence of PDNV 56% • Conventional surgery 36%; laparoscopic surgery 35% • American Society of Anesthesiologists’ Physical Status II—70%

14. Exploratory Factor Analysis withVarimax Rotation of Two Factorsa a Sample size varies from 197-203. Note: Factor 1 = Nausea; Factor 2 = Vomiting.

15. Internal Consistency Reliability • Cronbach’salphas were > .80 for the 7-item AS-INVR and the shortened 6-item AS-INV, indicating strong internal consistency of both measures in this sample of ambulatory surgery patients.

16. Factor Structure and Cronbach’s Alphas for the 7-Item AS-INVR by Day Post-surgery a,b aAS-INVR = Ambulatory Surgery-Inventory of Nausea, Vomiting, Retching bSample size varies from 197-203. cResults based on exploratory factor analysis with Varimax rotation; all factor loadings were .40 or greater.

17. Internal Consistency of the AS-INV a,b a Ambulatory Surgery-Inventory of Nausea and Vomiting b Sample size varies from 197-203.

18. Construct Validity

19. Differences in Mean AS-INVR and AS-INV Scores by Presence of PDNV and Post-Op Day a, b a Sample size varies from 197-203. b All comparisons significant at p < .001.

20. Correlations of the 6-Item AS-INV Scores with QOL-N, QOL-V, and Mean PDN Scores by Post-Operative Daya a Sample size varies from 195-203. *p < .01 Note: --Unable to compute because of lack of vomiting

21. Discussion • The results of dimensionality assessment support shortening the 7-item AS-INVR to form the 6- item AS-INV. • Both versions demonstrated strong internal consistency. • Construct validity was supported via hypothesis testing: • Patients with PDNV had higher AS-INVR and AS-INV mean scores than those without PDNV. • Higher AS-INVR and AS-INV scores were associated with lower quality of life scores related to nausea. • Higher AS-INVR and AS-INV scores were associated with lower quality of life scores related to vomiting.

22. Conclusions • The AS-INV is an inexpensive, easy to administer measure of nausea and vomiting in adults after ambulatory surgery. • The 6-item AS-INV is recommended based on this psychometric evaluation of the 7-item AS-INVR. • This shortened scale provides a reliable and valid measure of the amount and distress of nausea and vomiting in adult patients after ambulatory surgery. • The 6-item version should be considered for use in future studies.