In: Septic Shock6 Nov 2014
Analysis of Factors that Can Influence Ejection Fraction
Although EF is used as a measure of cardiac performance, it can be altered by changes in preload, afterload, and heart rate. The PAWP and EDVI can be used as measures of LV preload. Both were significantly higher in patients with MDS, even though the mean EF was lower in these patients (Table 1). Thus, preload cannot account for the differences in EF between the groups with and without MDS.
Afterload can be represented by systemic vascular resistance. As shown in Table 1, both systemic vascular resistance and heart rate were similar in the MDS-positive and MDS-negative groups. Thus, neither of these cardiac parameters can account for the EF differences between the two patient groups.
To evaluate further the cardiac parameters that could affect EF, the serial determinations of EF, systemic vascular resistance (afterload), EDVI (preload), and norepinephrine dose (vasopressor therapy) are listed in Table 2. All of the serial systemic vascular resistance changes between initial and subsequent values were statistically insignificant in both groups of patients; thus, afterload changes could not account for the large decrease in mean EF in MDS positive patients. The increase in EDVI from days 0 to 1 to days 2 to 4 in the MDS-positive patients could not account for the decreased EF, because increased preload should induce an increase (not a decrease) in EF. The decrease in norepinephrine dose from days 0 to 1 to days 2 to 4 in MDS positive patients would be expected to decrease afterload and increase EF; however EF decreased in MDS-positive patients during this interval. (Please see a previously published reference for discussion of this issue.) read
Thus, the comparison of MDS-positive and MDS-negative groups (Table 1) and the analysis of serial parameters in these two groups (Table 2) both failed to identify another reason for the decreases in EF that occurred in the MDS-positive patients, supporting the hypothesis that MDS was the cause of these decreases.
Table 2—Serial Relationships Among Preload, Afterload, Norepinephrine Dose, and Ejection Fraction in Patients with and without MDS
|Days||EF, %||SVR, dynes*s/cm||EDVI, ml/m2||Norepinephrine Dose, (JLg/min|
|0 to 1||39.7 ± 4.5f||580 ±140||138 ±16||25.8± 11.8|
|2 to 4||28.0±3.4||826 ±104||162 ±16||1.9± 1.2|
|5 to 8||50.8 ±3.6||750 ±65||98±9||0.0|
|0 to 1||41.6±2.4||755 ±107||115± 10||13.3 ±10.8|
|2 to 4||39.3 ±2.7||899 ±92||118±9||0.0|
|5 to 8||46.2 ±3.1||800 ±210||113 ±16||0.0|
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