ASN's Mission

To create a world without kidney diseases, the ASN Alliance for Kidney Health elevates care by educating and informing, driving breakthroughs and innovation, and advocating for policies that create transformative changes in kidney medicine throughout the world.

learn more

Contact ASN

1401 H St, NW, Ste 900, Washington, DC 20005


The Latest on X

Kidney Week

Please note that you are viewing an archived section from 2022 and some content may be unavailable. To unlock all content for 2022, please visit the archives.

Abstract: SA-PO361

Measured Serum Osmolality, Patient Symptoms, and Blood Pressure During Hemodialysis

Session Information

Category: Dialysis

  • 701 Dialysis: Hemodialysis and Frequent Dialysis


  • Yen, Timothy E., Brigham and Women's Hospital, Boston, Massachusetts, United States
  • Georgiadis, Despina, Brigham and Women's Hospital, Boston, Massachusetts, United States
  • Del Castillo Rix, Daniel Sebastian, Brigham and Women's Hospital, Boston, Massachusetts, United States
  • McCausland, Finnian R., Brigham and Women's Hospital, Boston, Massachusetts, United States

End stage kidney disease (ESKD) is accompanied by accumulation of uremic solutes in the blood. Many of these are rapidly cleared during hemodialysis (HD), leading some to postulate that rapid decline in serum osmolality may be associated with development of adverse symptoms and intra-dialytic hypotension (IDH).


We performed a prospective cohort study of 50 hospitalized adult patients with ESKD receiving thrice-weekly HD. Measured Osmolality (mOsm) and intradialytic symptoms (ascertained by SMaRRT-HD questionnaire) were measured at three time points during a single inpatient HD session (pre-HD, 60 minutes, and post-HD). Blood pressure was measured every 15 minutes during HD. Spearman correlations were used to compare the pre-HD mOsm with patient reported outcome symptom scores; logistic regression was used to assess the association of mOsm with IDH (any decline in SBP <90 mmHg).


Mean age was 65±15 years; 42% were female. The calculated Osm was an average of 1 unit higher than the mOSm, but varied widely (median difference 1 [-1, 4] milliOsm/kg). Mean mOsm decreased from 292±9mOsm/kg pre-HD, to 286±6 at 60 mins, 284±5 post-HD. The mean total symptom score was 14.8±3 pre-HD, 14.5±2.8 at 60mins, 15.1±3.4 post-HD. Correlations between pre-HD mOsm and symptom scores are shown in Table 1. IDH occurred in 9 of 50 (18%) sessions; each 5 unit increase in mOsm was associated with 43% higher risk of IDH (OR 1.43; 95%CI 0.95 to 2.14). Similar estimates were noted upon adjustment for age, sex, and pre-HD SBP (OR 1.44; 95%CI 0.90 to 2.32).


This prospective cohort study in hospitalized HD patients found substantial variability between measured and calculated Osm. Minimal correlation between mOsm and symptoms were noted, but may have been limited by minimal symptom scores overall. Signals for association of higher pre-HD mOsm with higher risk of IDH require investigation in larger studies.


  • NIDDK Support –