Evaluation of Hydration Status in Patients with Intestinal Insufficiency or Intestinal Failure by Bioelectrical Impedance Measurements

Abstract

Baggrund: Vand er et vigtigt næringsstof for liv og udgør en multifunktionel bestanddel af den menneskelige krop. Således medfører, især mangel på vand (dehydrering), men også overskydende mængder af vand (overhydrering) forskellige fysiologiske forstyrrelser i kroppen. Patienter med tarminsufficiens (INS) eller tarmsvigt (IF), der henholdsvis modtager oral ernæring (ON) eller hjemme parenteral ernæring (HPN), er i risiko for udvikling af forstyrrelser i kroppens vandbalance på grund af nedsat/ophørt tarmfunktion. Korrekt evaluering af patienternes hydreringstilstand er derfor et vigtigt aspekt af sygdomsmonitoreringen. Desværre findes der ikke én enkelt ”gold standard” indenfor dette felt. Teknikker såsom bioelektrisk impedansanalyse (BIA) og bioelektrisk impedansvektoranalyse (BIVA) er blevet præsenteret som nye mulige alternativer til ældre teknikker, der anvendes i klinikken. Det er dog stadig ukendt hvor godt disse nye teknikker er i forbindelse med evalueringen af hydreringstilstanden hos patienter med INS eller IF. Formål: At evaluere anvendelsen af BIA og BIVA som teknik til vurdering af hydreringstilstanden hos INS- og IF-patienter i forhold til referenceteknikker bestående af beregnet plasma-osmolaritet og 24-timers urinvolumen. Metode: Hydreringstilstanden blev evalueret i 253 metabolisk stabile patienter med enten INS (n=125) eller IF (n=128) ud fra beregnet plasma-osmolaritet, 24-timers urinvolumen, heldkrops multifrekvens-BIA og BIVA. Patienterne blev klassificeret som enten dehydreret, euhydreret eller overhydreret i henhold til specifikke referenceintervaller for hver parameter. Korrelationen mellem parametrene blev vurderet ved Pearson’s product-moment korrelation, mens pålideligheden blev testet ved brug af vægtet Kappa (κw) med lineære vægtning. Forskelle mellem ON- og HPN-patienter (dvs. patienter med henholdsvis INS og IF) blev beregnet for multiple demografiske og kliniske værdier samt for klassificeringen af hydreringstilstanden ved brug af Test of two proportions, Independent-samples T-test, og Chi-square test of homogeneity (r x 2)/Fisher’s exact test (r x 2) med post hoc test, hvor det var relevant. Resultater: En statistisk signifikant korrelation (p <0,05) blev kun fundet mellem plasma-osmolaritet og BIA-data samt BIVA-data, skønt korrelationerne var dårlige (korrelationskoefficient fra -0.150 til -0.245). Plasma-osmolaritet og 24-timers urinvolumen resulterede i en hydreringsklassificering, der var statistisk signifikant forskellig (p <0,05) mellem ON- og HPN-patienter. Post hoc-test kunne ikke bekræfte mellem hvilken hydreringsklasse forskellen eksisterede. Ingen af de andre teknikker kunne diskriminere mellem ON- og HPN-patienter ud fra hydreringsklassificeringen (p >0,05). Signifikant overensstemmelse (p <0,05) mellem teknikker blev kun fundet for plasma-osmolaritet og BIVA samt BIA, begge med en overensstemmelse mindre end dén forventet ved tilfældighed (κw <0,0). Konklusion: Studiet demonstrerede, at hydreringsklassificeringen af INS- og IF-patienter varierede med valg af teknik, og at der ikke eksisterede nogen overensstemmelse bedre end dén forventet ved tilfældighed mellem standardteknikker (plasma osmolaritet og 24-timers urinvolumen) og nyere teknikker (BIA og BIVA). Det var ikke muligt at konkludere, om ON-patienter blev klassificeret oftere eller færre gange som dehydreret, euhydreret eller overhydreret i sammenligning med HPN-patienter. Yderligere studier med forbedret studiedesign anbefales for at verificere resultaterne.

Background: Water is a vital nutrient of life and a multifunctional constituent of the human body thus, especially lack of water (dehydration), but also excessive amounts of water (overhydration) cause various functionally disturbances in the body. Persons with intestinal insufficiency (INS) or intestinal failure (IF) on respectively, oral nutrition (ON) or home parenteral nutrition (HPN) are at risk of abnormal water balance due to altered/impaired gastrointestinal functions. Thus, an important aspect of disease management is therefore proper evaluation of hydration status. However, no single gold standard exists. Techniques such as bioelectrical impedance analysis (BIA) and bioelectrical impedance vector analysis (BIVA) have been presented as new possible alternatives to older techniques used in clinical settings. Though, it is still unknown how well these techniques perform as hydration assessment methods in patients with INS or IF. Objectives: To evaluate the performance of BIA and BIVA as hydration assessment techniques in INS- and IF-patients with calculated plasma osmolarity and 24-hour urine volume as reference techniques. Methods: Hydration status was evaluated in 253 metabolic stable patients with either INS (n=125) or IF (n=128) according to calculated plasma osmolarity, 24-hour urine volume, whole-body multi-frequency-BIA and BIVA. Patients were classified by each parameter as either dehydrated, euhydrated, or overhydrated according to specific reference intervals. Correlation between parameters was assessed by Pearson’s product-moment correlation while reliability was tested by weighted Kappa (κw) with linear weights. Differences between ON- and HPN-patients (i.e. patients with INS and IF, respectively) in regard to demographics and clinically values as well as hydration classification were investigated by Test of two proportions, Independent-samples T-test, and Chi-square test of homogeneity (r x 2)/Fisher’s exact test (r x 2) with post hoc test where appropriate. Results: A statistically significant correlation (p <0.05) was only found between plasma osmolarity and BIA-data as well as BIVA-data, although poor (correlation coefficient ranging from -0.150 to -0.245). Assessment by plasma osmolarity and 24-hour urine volume resulted in a hydration classification that was statistically significant different (p <0,05) between ON- and HPN-patients. Post hoc test could not confirm between which hydration status the difference existed. None of the other assessment techniques could discriminate ON-patients from HPN-patients based on hydration classification (p >0,05). Significant agreement (p <0,05) between techniques was only demonstrated for plasma osmolarity and BIVA as well as plasma osmolarity and BIA, both with an agreement less than the one expected by chance (κw <0.0). Conclusion: The study demonstrated that hydration classification of INS- and IF-patients varied with choice of hydration assessment technique and that no agreement above the one expected by chance existed between standard techniques (plasma osmolarity and 24-hour urine volume) and novel techniques (BIA and BIVA). It was neither possible to conclude if ON-patients where classified more often or fewer times as dehydrated, euhydrated, or overhydrated than HPN-patients. Further studies are recommended with improved study design in order to verify the present study’s results.

A master thesis from Aalborg University

Evaluation of Hydration Status in Patients with Intestinal Insufficiency or Intestinal Failure by Bioelectrical Impedance Measurements