| Limitations | Potential Impact |
---|---|---|
Patient-related factors | Observational study designs with generally small sample sizes | High degree of confounding and bias; elucidation of true causal relationships not possible |
Heterogeneous sepsis classification (SOFA, SIRS) and severity | Difficult to make conclusions across varied populations; prognostic value of echocardiography findings confounded by collinearity between severity of disease and adverse outcomes | |
Pre-septic cardiac function largely unknown | Acute versus chronic dysfunction may portend different prognosis | |
Variation in co-morbidities | Complex interaction between pre-existing illnesses, acute infection, and treatment renders cross-patient comparisons difficult | |
Variation in treatments (mechanical ventilation, vasopressors, inotropes) | Therapeutic interventions likely affect cardiac performance and echocardiographic measurements and may alter outcomes | |
Echocardiography-related factors | Variable timing of initial echocardiogram | Normal progression of disease (natural history) and treatment prior to initial exam may alter findings |
Variability of timing and number of repeat echocardiograms | Ongoing resuscitation may alter cardiac performance via intrinsic (e.g., increased contractility) or extrinsic (change in loading conditions) factors | |
Reference ranges derived in stable patients | Unknown how/if normal values are applicable in the setting of sepsis | |
GLS values not standardized across ultrasound vendors | Difficult to compare GLS values across US systems |