Trends of volemic indicators in a group of critically ill patients

Introduction

The aim of this prospective non intervention study is to analyse the clinical utility of traditional preload indicators, as central venous pressure (CVP, mmHg) or pulmonary capillary wedge pressure (PCWP, mmHg), and the meaning of a pure volume indicator, as intrathoracic blood volume (ITBV, ml/m² BS).

Material and methods

Eighty-four medical or surgical patients were studied (mean age 51, SD 17; mean SAPS II (1^st day) 56, SD 9). After 6 h of ICU stay, a 7.5 F pulmonary artery catheter and a 4 F femoral artery catheter, with thermistor and fiberoptics were inserted and connected to `COLD System', an integrated monitoring system which uses the double indicator technique for studying blood volumes. All patients were in CMV (PEEP <8 cmH₂O); haemodynamic management was realized in order to optimize cardiac output (CO, l/min/m² BS) and systemic oxygen delivery. Infusion of crystalloids and colloids was guided by measurements of CVP and PCWP. All data were recorded at the beginning of the study (T0) and after 6 (T1), 12 (T2), 24 (T3) and 36 (T4) h. Statistical analysis of data was performed using Manova Test, considering the significant differences in the times of study between group A (38 pts., ITBV in T0 <1 l/m² BS) and group B (46 pts., ITBV in T0 >1 l/m² BS) and analysing the variance of repeated measures. Levels of P < 0.05 were accepted.

Result and conclusions

The Table shows the trends of parameters in the times of study (data are expressed as mean and (SD); A vs B, ^$ P < 0.0001; ^* P< 0.05; T vs T0,^§ P < 0.05).

When preload is the main determinant of CO, CVP and PCWP may be misleading in management of volemia in mechanically ventilated patients, on the contrary ITBV may be useful to optimize central filling and haemodynamic conditions.

Table 1