PLASMA VOLUME IN NORMAL AND SICKLE CELL PREGNANCY By Bosede Bukola Afolabi, M.B.Ch.B Thesis submitted to the University of Nottingham for the degree of Doctor of Medicine June 2011 TABLE OF CONTENTS ACKNOWLEDGEMENT ................................................................................................ i DECLARATION ............................................................................................................ iv ABSTRACT ..................................................................................................................... v ABSTRACTS OF CONFERENCE PRESENTATIONS ............................................... vi LIST OF ABBREVIATIONS USED IN THE THESIS ................................................ vii 1. INTRODUCTION ..................................................................................................... 10 1.1. OVERVIEW AND GENERAL PHYSIOLOGY OF SICKLE CELL DISORDER................................................................................................................ 12 1.1.1. Cardiovascular physiology........................................................................... 17 1.1.1.1. Plasma volume ...................................................................................... 18 1.1.2. Renal physiology ......................................................................................... 20 1.1.2.1. Haemodynamics .................................................................................... 20 1.1.2.2. Hyposthenuria ....................................................................................... 22 1.1.2.3. Water balance........................................................................................ 23 1.1.3. Physiology in pregnancy .............................................................................. 24 1.2. CONTROL OF PLASMA VOLUME IN PREGNANCY.................................. 26 1.2.1. Components of plasma ................................................................................. 27 1.2.2. Factors affecting plasma volume regulation ................................................ 28 1.2.2.1. Sodium .................................................................................................. 29 1.2.2.2. Effects of adrenocortical steroids on sodium regulation....................... 30 1.2.2.3. Effects of Angiotensin II (AII) and renin ............................................. 31 1.2.2.4. Effect of ACTH..................................................................................... 33 1.2.2.5. Effects of electrolytes ........................................................................... 33 1.2.2.6. Arginine Vasopressin (AVP) ................................................................ 33 1.2.2.7. Osmoreceptors ...................................................................................... 34 1.2.2.8. Prolactin and dopamine ......................................................................... 35 1.2.2.9. Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) .. 35 1.2.2.10. Nitric oxide (NO) pathways ................................................................ 36 1.2.3. Pregnancy ..................................................................................................... 37 1.2.3.1. Maintenance of plasma volume expansion in pregnancy ..................... 41 2. METHODS ................................................................................................................ 44 2.1. SUBJECT SELECTION AND INCLUSION CRITERIA ................................. 44 2.2. EXCLUSION CRITERIA .................................................................................. 46 2.3. SAMPLE SIZE ................................................................................................... 46 2.4. STUDY DESIGN ................................................................................................ 46 2.5. INTERVENTION ............................................................................................... 47 2.6. PLASMA VOLUME MEASUREMENT AND SPECIMEN COLLECTION ... 49 2.6.1. 24-hour urine collection ............................................................................... 49 2.6.2. Blood collection ........................................................................................... 50 2.6.3. Specimen processing .................................................................................... 52 2.7. LABORATORY METHODS .............................................................................. 5 3 2.7.1. Plasma volume measurements ..................................................................... 53 2.7.2. Plasma volume measurements in this thesis ................................................ 54 Figure 2.2. An example of a concentration/time plot ............................................ 57 2.7.3. Radioimmunoassay and enzyme immunoassay ........................................... 58 2.7.4. Aldosterone .................................................................................................. 60 2.7.5. Arginine-Vasopressin (AVP) ........................................................................ 60 2.7.6. Progesterone ................................................................................................. 60 2.7.7. Prolactin ....................................................................................................... 61 2.7.8. Osmolality measurements ............................................................................ 61 2.7.9. Creatinine ..................................................................................................... 61 2.7.10. Electrolytes (Sodium and Potassium) ........................................................ 62 2.8. DATA HANDLING ............................................................................................ 62 2.8.1. Statistical analysis ........................................................................................ 63 2.9. DISCUSSION ..................................................................................................... 64 2.9.1. Subject selection and inclusion criteria........................................................ 64 2.9.2. Sample preservation ..................................................................................... 65 2.9.3. Twenty-four hour urine collection ............................................................... 66 2.9.4. Plasma volume measurement ....................................................................... 66 2.9.5. Renin-angiotensin assays ............................................................................. 68 2.9.6. Study design and recruitment....................................................................... 68 2.9.7. Study data..................................................................................................... 70 2.9.7.1. Calculation of body surface area ........................................................... 70 2.9.7.2. Calculation of glomerular filtration rate (GFR) .................................... 70 3. NON-PREGNANT SICKLE CELL STUDY RESULTS.......................................... 72 3.1. STUDY DESIGN AND RECRUITMENT ........................................................ 72 3.1.1. Technical reasons (18 women) .................................................................... 73 3.1.2. Methodological reasons (34 results) ............................................................ 73 3.2. CHARACTERISTICS OF STUDIED WOMEN ............................................... 74 3.2.1. Characteristics of studied women within groups (Table 3.2) ...................... 75 3.3. NON-PREGNANT WOMEN ............................................................................. 77 3.3.1. Haematological variables amongst non-pregnant women ........................... 77 3.3.2. Plasma volume amongst non-pregnant women ........................................... 77 3.3.3. Plasma and urinary osmolality and electrolytes ........................................... 80 3.3.4. Hormones ..................................................................................................... 83 3.3.5. Association between plasma volume and measured indices........................ 84 4. PREGNANT SICKLE CELL STUDY RESULTS.................................................... 94 4.1. ALL PREGNANT WOMEN .............................................................................. 9 4 4.1.1. Haematological variables amongst pregnant women .................................. 94 4.1.2. Plasma volume amongst pregnant women ................................................... 96 4.1.3. Plasma and urinary osmolality and electrolytes ........................................... 96 4.1.4. Hormones (Table 4.4) .................................................................................. 98 4.2. PREGNANT VERSUS NON-PREGNANT WOMEN .................................... 101 4.2.1. Pregnant versus non-pregnant Hb AA women .......................................... 101 4.2.2. Pregnant versus non-pregnant Hb SS women ............................................ 114 4.3. BIRTH WEIGHT AND PLASMA VOLUME ................................................. 124 4.3.1. Birth weight and gestational age at delivery .............................................. 124 4.3.2. Plasma volume and birth weight ................................................................ 1 2 5 5. DISCUSSION .........................................................................................................