Cognitive function in hemodialysis patients

We investigate the effects of inflammation and Autonomic Nervous System activity on cognitive function during a hemodialysis session.All measurements took place 30 min before the onset of the HD therapy and 30 min after the HD therapy. Subjects were studied in a quiet, comfortable room with controlled temperature between 25 and 28 degrees Celcius. Inflammation was evaluated ANS function was assessed simultaneously using pupillometric and Heart Rate Variability (HRV) measurements. A physiologist administered all the methods. Cognitive function assessment Cognitive function was assessed before the onset of the HD therapy and 30 min after the completion of the HD therapy. Mini-Mental State Examination (MMSE) in Greek, which includes 11 items and needs about 7-10 minutes to complete, was used for the cognitive impairment evaluation. MMSE evaluates orientation, attention, memory, concentration, language and constructional ability, with a total score range from 0 to 30 which reflects the number of correct responses . Score from 30 to 24 indicates normal cognitive function while score below 24 reflects cognitive impairment, which could be mild (score between 19-24), moderate (score between 10-18) or severe (score below or equal to 9). Pupillometry The hand-held infrared pupillometer (NeurOptics PLR-200 trademark City and Country) was used to measure the pupil size and the pupillary light reflex. The pupillometer uses infrared imaging technology and it requires no calibration by the user. Pupillometry was performed on each eye separately. Each eye assessed three times with 5 minutes apart. The pupillometric indices were: 1) maximum pupil size namely the baseline pupil diameter after 2 min dark adaptation, which is an indicator of symaptho-vagal balance, 2) minimum pupil size, which is generally defined as a marker of sympatho-vagal balance, since it is involved in the second segment of the V-shaped pupillometric response, 3) constriction, which is modulated by PNS activity, 4) latency, which is an index of sympatho-vagal balance, 5) average constriction velocity and 6) maximum constriction velocity, which are both sensitive indices of PNS activity , 7) average dilation velocity, which reflects sympatho-vagal balance and 8) 75% pupil size recovery time, which is an index of SNS activity. An average of the three measurements was recorded as the final value. Inflammation status The blood samples were collected 30 min before the onset of the HD therapy and 30 min after the completion of the HD therapy. The blood samples were collected in tubes containing EDTA and centrifuged immediately. Serum C-reactive protein (CRP) was detected using the immunonephelometric assay on the BNII nephelometer (N High Sensitivity CRP; Dade Behring Inc, Deerfield, IL).