The prevalence and impact of postprandial hypotension in elderly survivors of critical illness.

Seventy five consecutive patients aged 65 years old or older who receive at least 48 hours of care in ICU will be evaluated at 3 months (+/- 1 month) following discharge from ICU. We will document basic demographic data, all current medications (prior to hospital admission and on discharge from ICU, with particularly reference to the presence of anti-hypertensive drugs which will be analysed as pre-defined sub-group) and concurrent chronic illnesses and use validated questionnaires to evaluate falls/symptoms of PPH, frailty (a syndrome characterised by the loss of physiologic and cognitive reserves that will be quantified via the Canadian Study on Health and Ageing Clinical Frailty Scale, a well-validated 9-point assessment tool designed to quantify frailty), independent activity of daily living (iADLs) and quality of life using questionnaires. The later will be quantified using the generic quality of life instrument (EQ-5D-5L), which provide a utility score and visual analogue scale score. On the study day, patients will present to the Department of Nuclear Medicine, PET and Bone Densitometry or Diabetes Centre (where we have a gamma camera used exclusively for research purposes) at the Royal Adelaide Hospital following an overnight fast (12 hrs solids and liquids). Smoking will be prohibited for 12 hours prior to and on the study day. Participants will be instructed to consume their usual medications on the morning of the study with a small sip of water. Instructions regarding glucose-lowering drugs will be provided to patients with diabetes by a consultant endocrinologist (Dr Phillips). Following informed consent participants will be asked to rest quietly in a chair for 10 minutes. Lying, seated, and standing blood pressures will then be measured. Following these measurements, an intravenous cannula will be inserted into an antecubital vein for blood sampling. Subjects will then be seated with their back against a gamma camera with an automated blood pressure cuff placed around the opposite arm for measurement of blood pressure and heart rate. Participants will sit quietly for a further 5 minutes and following baseline measurements participants will consume a 300mL drink (Glucaid) containing 75g glucose labelled with 0.1g of Octanoic acid and 20MBq 99mTc-calcium phytate. Scintigraphy and a breath test will be used to assess gastric emptying for 4 hours. The breath test will require the participant to breathe into a collection tube at 5 minute intervals for the first hour and then every 15 minutes thereafter. Scintigraphic gastric emptying curves (expressed as % of the maximum content of the total stomach) will be derived and the content of the total stomach at t = 0, 15, 30, 45, 60, 90, 120, 150, 180, 210 and 240 minutes calculated. The duration of the lag phase and the 50% emptying time (T50) will also be obtained. Blood pressure (systolic and diastolic) and heart rate will be assessed prior to ingestion of the drink and at 3 min intervals until completion of the study i.e. t=240mins. After the study, the subject’s blood pressure will be monitored at 15 min intervals for a minimum of 1 hour to ensure the subject's blood pressure has returned to baseline levels for safety reasons. Blood samples will be obtained immediately prior to ingestion of the drink (t = -3 minutes) then every 15 minutes until t = 240 minutes for blood glucose. We will also measure serum insulin, gastrointestinal hormones (GLP-1 and GIP) and catecholamines (RAH Protocol 131217) at baseline and every 15 minutes until t=60, every 30 minutes until t=120 and then hourly until t=240. Sensations of appetite and dizziness will be evaluated using a visual analogue scale immediately prior to ingestion of the drink (t = -3 minutes) then every 15 minutes until t = 240 minutes. Upon completion of the gastric emptying study, the intravenous cannula will then be removed. Then Autonomic nerve function will be assessed using standardised cardiovascular reflex tests using ANSAR Autonomic Nervous System monitoring technology. Parasympathetic function will be calculated by the variation (R - R interval) of the HR during deep breathing and the immediate heart rate response to standing ("30:15" ratio). Sympathetic function will be assessed by the fall in systolic blood pressure in response to standing. To evaluate the trajectory of PPH symptoms, severity and impact over time, participants will be approached at 12 months and three years to complete an identical set of measurements. Prior to approaching patients we will determine whether hospital electronic repositories (OACIS) indicate that the patient has died. Once this is excluded we will contact the participant. The 12 month and three year visits will be identical to those conducted at three months. In addition we will quantify re-hospitalisation during this period.