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UNIVERSITY of CALIFORNIA Los Angeles Baroreflex Sensitivity UNIVERSITY OF CALIFORNIA Los Angeles Baroreflex Sensitivity during Positional Changes in Patients with Traumatic Brain Injury A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Nursing by Norma Dianne McNair 2012 © Copyright by Norma Dianne McNair 2012 ABSTRACT OF THE DISSERTATION Baroreflex Sensitivity during Positional Changes in Patients with Traumatic Brain Injury by Norma Dianne McNair Doctor of Philosophy in Nursing University of California, Los Angeles, 2012 Professor Mary A. Woo, Chair Background and Significance: Traumatic brain injury (TBI) affects 1.7 million Americans annually leading to significant morbidity and health care costs. An important cause of morbidity in TBI is secondary brain injury due to abnormal cerebrovascular autoregulation (CA). Standard measures of CA are not amenable to use outside of the intensive care unit (ICU) and patients continue to be at risk for secondary brain injury post- ICU. Baroreflex sensitivity (BRS) is a non-invasive assessment of autonomic tone that may be useful in evaluating CA. Evaluation of BRS and its relation to CA has not been examined in patients with TBI and predictors of CA are unknown. Purpose: The specific aims for this study were to 1) examine the association between BRS and CA in patients with TBI, 2) compare BRS and CA in TBI patients and age and gender matched healthy volunteers (HV) and 3) identify predictors of BRS and CA in TBI. ii Methods: This study used a two group comparative design with 52 subjects (26 with moderate to severe TBI; 26 HV). Measurement of variables: BRS was calculated as heart rate/mean arterial pressure; CA was calculated as cerebral blood flow velocity using transcranial Doppler; and cognition was assessed using the Galveston Orientation and Amnesia Test (GOAT). Results: There was no significant correlation between BRS and CA, however, BRS had high specificity (77%) for normal CA. BRS was not significantly different between TBI and HV subjects, those with normal or abnormal CA nor was BRS an independent predictor of CA. Forty six percent of TBI subjects had abnormal CA after their TBI (mean = 59.58 ± 36.54 days) and 34.6% of HV had abnormal CA. Predictors of abnormal CA were male gender, ACE- Inhibitors and GOAT. Implications: BRS can be used to identify normal CA. The GOAT has potential for routine assessment of CA status in non-ICU areas. Large proportions of TBI subjects long after a TBI event and HV had abnormal CA. Thus assessment of CA status is important in TBI subjects after ICU discharge and further research is needed on the impact of pre-existing CA abnormalities in HV. iii The dissertation of Norma Dianne McNair is approved. Barbara Bates-Jensen Margaret A. (Peggy) Compton David A. Hovda Mary A. Woo, Committee Chair University of California, Los Angeles 2012 iv DEDICATION This work is dedicated to the patients, family members and healthy volunteers who so willingly participated in this research in the hopes that others would benefit from the results. and To the memory of my parents, Norman David McNair and Shirley Grady McNair, who whether they knew it or not, instilled in me a desire for life-long learning. v TABLE OF CONTENTS Page Abstract…….............................................................................................................. ii Dedication….............................................................................................................. iv List of Figures............................................................................................................ ix List of Tables............................................................................................................. xi Acknowledgements…................................................................................................ xiii Vita, Publications and Presentations…..................................................................... xvii Chapter 1 Introduction............................................................................................... 1 Background and Significance........................................................................ 3 Traumatic Brain Injury...................................................................... 3 Cerebrovascular Autoregulation........................................................ 7 Baroreflex Sensitivity........................................................................ 12 Positioning......................................................................................... 18 Cognition/Memory............................................................................. 21 Specific Aims……............................................................................ 22 Chapter 2 Review of the Literature........................................................................... 24 Traumatic Brain Injury……………………………….................................. 24 Secondary Brain Injury…..............................................................… 25 Cerebrovascular Autoregulation……….................................................................... 28 Patterns of Cerebrovascular Autoregulation…………………….................. 29 Standard Measures of Cerebrovascular Autoregulation…............................ 30 vi Page Baroreflex Sensitivity………..................................................................................... 34 Methods of Measurement of Baroreflex Sensitivity…….............................. 34 Findings in Neurological Diagnoses……...................................................... 38 Findings in Traumatic Brain Injury…………………………....................... 39 Impact of Nursing Procedures on Cerebrovascular Autoregulation.......................... 40 Cognition/Memory ……............................................................................................ 41 Summary………………………................................................................................ 43 Chapter 3 Theoretical Framework…………............................................................. 45 General System Theory…….......................................................................... 45 Constructs…….................................................................................. 45 Concepts………................................................................................. 48 Empirical Indicators……...........................................…………….... 50 Chapter 4 Research Methodology……..................................................................... 53 Study Design……................................…………………………………….. 53 Setting………................................................................................................ 53 Sample............………………........................................................................ 53 Measurement of Variables………….............................................................. 55 Data Collection Procedures…….................................................................... 59 Statistical Analyses………………................................................................ 60 vii Page Chapter 5 Results………………………………………………………………...... 62 Subject Characteristics……………………………………………………... 62 Specific Aim # 1………………………………………………………….... 66 Specific Aim # 2………………………………………………………….... 67 Specific Aim # 3…………………………………………………………... 81 Chapter 6 Discussion……………………………………………………………… 89 Baroreflex Sensitivity and Cerebrovascular Autoregulation in Traumatic Brain Injury…………………………………………………… 89 Incidence of Abnormal Cerebrovascular Autoregulation in Healthy Subjects…........................................................................................ 93 Assessment of Cerebrovascular Autoregulation Status…………………… 94 Limitations of the Study…………………………………………………... 99 Implications for Nursing Practice…………………………………………. 100 Future Research……………………………………………………………. 102 Overall Summary…………………………………………………............... 103 Appendices…………………………………………………………………............ 104 Appendix A: IRB Approval from University of California Los Angeles, Medical IRB 3……………………………………………………………… 104 Appendix B: Recruitment Flyer for Healthy Volunteers…………………... 111 Appendix C: Recruitment Flyer for TBI Subjects at Ronald Reagan UCLA Medical Center…………………………………… 113 Appendix D: Screening Script for Healthy Volunteers…………………… 115 Appendix E: Screening Script for Traumatic Brain Injury Subjects……… 118 viii Page Appendix F: Consent for Healthy Volunteers……………………………. 120 Appendix G: Permission to Use Personal Health Information for Research At UCLA…………………………………………………………………. 126 Appendix H: Obtaining Consent from Legally Authorized Representative.. 131 Appendix I: Consent for Traumatic Brain Injury Subjects at Ronald Reagan UCLA Medical Center……………………………………. 136 Appendix J: IRB Approval from Rancho Los Amigos National Rehabilitation Center……………………………………………. 140 Appendix K: Recruitment Flyer for TBI Subjects at Rancho Los Amigos National Rehabilitation Center…………………………………………… 145 Appendix L: Permission to Use Personal Health Information for Research at Rancho Los Amigos National Rehabilitation Center……………………… 147 Appendix M: Consent for Traumatic Brain Injury Subjects at Rancho Los Amigos National Rehabilitation Center……………………… 150 Appendix N: Medical Record Screening Document……………………… 155 Appendix O: Data Collection Instrument………………………………… 157 Appendix P: Galveston Orientation and Amnesia Test…………………… 159 Appendix Q: Glasgow Coma Scale……………………………………….. 161 Appendix R: Research Participants Bill of Rights………………………… 164 References…………………………………………………………………………
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