New insights in fluid monitoring for surgical patients. A concept study

Audrius Andrijauskas¹Povilas Andrijauskas^2*Darius Dilijonas³Vaidotas Marozas⁴Tomas Jovaiša¹Edgaras Stankevičius⁵Axel Kerroum⁶Darius Čincikas¹Saulė Švedienė¹Giedrius Kvederas¹Narūnas Porvaneckas¹Christer Svensen⁷

• ¹Faculty of Medicine, Vilnius University, Vilnius, Lithuania
• ²Vilnius University Hospital Santaros Clinics, Vilnius, Lithuania
• ³Institute of Social Sciences and Applied Informatics, Kaunas Faculty, Vilnius University, Vilnius, Lithuania
• ⁴Biomedical Engineering Institute, Kaunas University of Technology, Kaunas, Lithuania
• ⁵Institute of Physiology and Pharmacology, Lithuanian University of Health Sciences, Kaunas, Lithuania
• ⁶Lausanne University Hospital, Lausanne, Geneva, Switzerland
• ⁷Department of Clinical Science and Education, Södersjukhuset, Karolinska Institutet (KI), Stockholm, Stockholm, Sweden

Purpose This study evaluates the primary hypothesis of red cell mass (RCM) dependent amplitude of homeostatically acceptable limits of fluctuation in plasma dilution by exploring the correlation between RCM-specific equilibrated hematocrit (EQ_Hct) and amplitude of plasma dilution during perioperative mini Volume Loading Test (mVLT). Materials and Methods We retrospectively analyzed data from our previous RCTs, including 1,651 invasive arterial plasma dilution (aPD), 1,645 noninvasive “capillary” plasma dilution (cPD) and 236 estimates of EQ_Hct from 236 perioperative mVLT sessions. The cPD was estimated using noninvasive hemoglobin (SpHb, Masimo Radical 7, Irvine, CA) measurement. Fixed number of crystalloid boluses was used in 36 and 48 elective total knee arthroplasty (TKA) patients, and individualized number of boluses in 34 total hip arthroplasty (THA) patients for whom the number of boluses depended on the advices by our prototype automated clinical decision support system (ACDSS). Results The primary hypothesis was confirmed - aPD decreased as EQ_Hct decreased when EQ_Hct<40%, and a very weak positive correlation was found between EQ_Hct and absolute aPD (Spearman's correlation coefficient 0.1025, p < 0.001). It was also confirmed when non-invasive data sets were used. A very weak negative correlation between HctEQ values and absolute cPD values (Spearman's correlation coefficient 0.0640, p = 0.0149). Conclusion This study points to the feasibility of Photoplethysmography (PPG) based estimates of hemoglobin concentration for continuous noninvasive monitoring of fluid accumulation and detecting imminent edema using the Homeostatic Blood States (HBS) theory and transcapillary reflux model. The ACDSS-guided fluid loading has a potential to minimise unnecessary fluid accumulation. Further research is needed to explore and improve these techniques.