Circadian rhythmicity in the intensive care unit (ICU): understanding melatonin patterns and their relationship to delirium in ICU patients

The circadian rhythm is an internal body cadence, responsible for regulation of sleep in all mammals. In humans, this clock is altered by several factors, including light and secretion of the hormone melatonin. Within the intensive care unit (ICU) population, it is well evidenced that patients suffer from circadian dysregulation, often for long periods of time. Additionally, many parallels have been noted between severely fragmented sleep and delirium, an acute neurological condition frequently observed in ICU patients. A prospective cohort pilot study of five subjects was undertaken to enable a greater understanding of both sleep in the ICU and the relationship between circadian rhythm and delirium. From a total of thirty-six urine samples per subject, excretion of 6-sulphatoxymelatonin (aMT6s), the urinary metabolite of melatonin was analyzed. T-test comparison (p=0.05) of mean aMT6s (ng/mL) revealed significant differences in the nighttime excretion between subjects in this study and healthy individuals. No significant differences were observed with t-test comparison of mean aMT6s of the first 24 hours from the current study to ICU subjects in previous literature. No subjects were identified as delirious in the study and therefore no relationship could be found between circadian rhythmicity, as evidenced by melatonin excretion and delirium in this study population. Running head: CIRCADIAN RHYTHM 3 Acknowledgements There are a number of people who have contributed so very much, in a variety of ways, to enable me to reach my goal of receiving a Masters in Nursing. I will always be thankful to the following individuals/groups for their help: • God. I am thankful to Him who has given me the gift to care for others, and reach this goal. • My family. My children and best friend Jason Chau, who have continued to be my motivation to complete this project. • My best friend in the world, Shanna Mae Olson. Shanna has provided with me babysitting to attend classes, editing and most importantly, heaps of emotional support and encouragement. • Dr. Diana McMillan, my supervisor, friend and mentor. Dr. McMillan’s enthusiasm inspired me from the first moment I met her. A wonderful and knowledgeable advisor, she has been there to teach me, help me understand the process of growth during a Masters, and has provided me insightful advice during the rough times in my program. • Dr. William-Diehl Jones, for providing me with his laboratory facilities and for his positive attitude at all times. • Dr. Rakesh Arora, for his continuous attempts to support me in whatever means were available to him. Additionally, for his expert knowledge in the area of delirium. Running head: CIRCADIAN RHYTHM 4 • Shelley Dollbeck, Patient Care Manager, for showing interest when no one else would, and providing unwavering support for me to complete my project on her nursing unit. • The bedside nurses on the Medical Intensive Care Unit for their assistance with sample collection and making this study a priority while they were already very busy at work. • The Manitoba Centre for Nursing and Allied Health Research for their assistance with statistical analysis. • Buhler Research Lab in the Health Sciences Centre, Winnipeg, Manitoba. • Kathleen and Winifred Ruane Foundation for the research grant which enabled this project. • Andrew Walker for his help with statistical analysis. Running head: CIRCADIAN RHYTHM 5 Dedication To my beloved children: Andrew, Emilyn, Calum and Isla Grace, I love you all so very much! You inspire me to dream big and motivate me to reach my goals and fulfill my educational pursuits. And to my mother, Jillian Dacyk, a piece of this book is yours. You have been my biggest supporter and helped me tirelessly, no matter the time of day. My love, always. Running head: CIRCADIAN RHYTHM 6