Relationship of inferior vena cava collapsibility to ultrafiltration volume achieved in critically ill hemodialysis patients

Abstract

BackgroundUltrasound (US) assessment of intravascular volume may improve volume management of dialysis patients. We investigated the relationship of intravascular volume evaluated by inferior vena cava (IVC) US to net volume changes with intermittent hemodialysis (HD) in critically ill patients.MethodsA retrospective cohort of 113 intensive care unit patients in 244 encounters had clinical assessment of intravascular volume followed by US of respiratory/ventilatory variation of IVC diameter, and had HD within 24 h. IVC collapsibility index (IVC CI)=(IVCmax–IVCmin)/IVCmax*100%. Volume management was guided by clinical data plus IVC US findings. Intradialytic hypotension (IDH) was categorized by severity from none to inability to tolerate HD.ResultsLinear regression correlating n-weighted proportions of encounters achieving net volume removal of ≥0.5 L, ≥1.0 L, ≥1.5 L, and ≥2.0 L strongly correlated across the range of IVC CI (R2=0.87–0.64). Sensitivity and specificity analysis showed IVC CI was a better predictor than IVCmax of achieving net ultrafiltration (UF) volumes. Mean central venous pressure, pulmonary artery occlusion pressure, and cardiac output were poor predictors by logistic regression and receiver operating curve analyses. IVC CI <20% was the approximate optimal cutoff for achieving ≥0.5 L to ≥2.0 L net UF volumes. Net volume change achieved tended to be less than recommended and may have been limited by the development of IDH. Severity of IDH did not correlate with UF rate in mL/kg/h. χ2 analysis showed pre-US clinical intravascular volume assessments had poor concordance with IVC CI categories.ConclusionIVC US may be a useful tool for predicting whether critically ill patients will achieve volume removal with HD.

Changes in cardiac output with hemodialysis relate to net volume balance and to inferior vena cava ultrasound collapsibility in critically ill patients

“…Bedside IVC US was performed in real-time during daily bedside rounds without Valsalva or sniff maneuvers, since most patients were unable to perform these maneuvers, as previously described [5]. For continuous HD encounters, all were scanned while on HD except for one who had IVC US pre-HD (Supplemental Table 1).…”

“…Severity of IDH was categorized as previously reported [5], with the greatest severity recorded for each encounter. Increasing severity of IDH in our ICU patients were as follows: 0, No criteria for IDH; 1, received more than 500 mL 0.9% saline or received albumin IV to treat IDH (all patients receiving intermittent HD received 250 mL of 0.9% saline initially to prime the line and dialyzer and 250 mL of 0.9% saline at the completion of HD to return the blood and rinse the line and dialyzer) [5]; 2a, MAP < 65 mmHg with or without volume resuscitation during HD, no vasopressors/inotropes given, and HD not discontinued due to hypotension; 2b, pre-HD hypotension requiring vasopressors/inotropes, and a constant dose of vasopressors/inotropes given to maintain BP before and during HD/UF with or without volume resuscitation; 3, SBP decreased more than 50 mmHg or MAP decreased more than 20% with or without volume resuscitation and/or vasopressors/ inotropes; 4, vasopressor/inotrope therapy initiated, dose increased, or dialysis stopped within 2 h due to intractable IDH with or without volume resuscitation.…”

“…Critically ill patients with undifferentiated hypotension have been shown to benefit from inferior vena cava ultrasound (IVC US) assessment of relative intravascular volume to guide volume management [3,4]. IVC US may be a useful tool for predicting whether critically ill patients are likely to tolerate volume removal with hemodialysis (HD) and ultrafiltration (UF) [5]. In our previous study, critically ill patients with low inferior vena cava (IVC) collapsibility index (CI) values, consistent with relative intravascular volume overload, more frequently tolerated UF, while those with high IVC CI consistent with low relative intravascular volumes were much less likely to tolerate UF [5].…”

“…IVC US may be a useful tool for predicting whether critically ill patients are likely to tolerate volume removal with hemodialysis (HD) and ultrafiltration (UF) [5]. In our previous study, critically ill patients with low inferior vena cava (IVC) collapsibility index (CI) values, consistent with relative intravascular volume overload, more frequently tolerated UF, while those with high IVC CI consistent with low relative intravascular volumes were much less likely to tolerate UF [5]. Assessing relative intravascular volume using inferior vena cava collapsibility determined by ultrasound may provide a useful tool in guiding volume management in critically ill patients receiving HD/UF.…”

“…Intradialytic hypotension (IDH) may relate to cardiac stunning and decreased CO in stable ESRD patients [25,26], and may limit the volume of net UF removed in critically ill patients [5].…”