Infusion of hypertonic saline/starch during cardiopulmonary bypass reduces fluid overload and may impact cardiac function

OBJECTIVE

Peri-operative fluid accumulation resulting in myocardial and pulmonary tissue edema is one possible mechanism behind post-operative cardiopulmonary dysfunction. This study aimed to confirm an improvement of cardiopulmonary function by reducing fluid loading during an open-heart surgery.

MATERIALS AND METHODS

Forty-nine elective CABG patients were randomized to an intraoperative infusion of hypertonic saline/hydroxyethyl starch (HSH group) or Ringer's solution (CT group). Both groups received 1 ml/kg/h of the study solution for 4 h after baseline values were obtained (PICCO transpulmonary thermodilution technique). Net fluid balance (NFB), hemodynamic and laboratory parameters were measured.

RESULTS

NFB was four times higher in the CT group compared with the HSH group during the first 6 h post-operatively. The total fluid gain until the next morning was lower in the HSH group, 2993.9 (938.6) ml, compared with the CT group, 4298.7 (1059.3) ml (P<0.001). Normalized values (i.e., %-changes from the baseline) of the cardiac index and the global end diastolic volume index increased post-operatively in both groups. Both parameters were significantly higher at 6 h in the HSH group compared with CT group (P=0.002 and 0.005, respectively). Normalized values of the intrathoracic blood volume index were lower in the HSH group at 6 h post-operatively when compared with the CT group. The PaO(2)/FiO(2) ratio decreased similarly in both groups early post-operatively, but recovery tended to be more rapid in the HSH group. Although serum-sodium and serum-chloride levels were significantly higher in the HSH group, the acid-base parameters remained similar and within the normal range.

CONCLUSIONS

An intraoperative infusion of HSH during cardiac surgery contributes to reduced fluid loading and an improvement in the post-operative cardiac performance. No adverse effects of the HSH infusion were observed.

Temporary fatigue and altered extracellular matrix in skeletal muscle during progression of heart failure in rats

Patients with congestive heart failure (CHF) experience increased skeletal muscle fatigue. The mechanism underlying this phenomenon is unknown, but a deranged extracellular matrix (ECM) might be a contributing factor. Hence, we examined ECM components and regulators in a rat postinfarction model of CHF. At various time points during a 3.5 mo-period after induction of CHF in rats by left coronary artery ligation, blood, interstitial fluid (IF), and muscles were sampled. Isoflurane anesthesia was employed during all surgical procedures. IF was extracted by wicks inserted intermuscularly in a hind limb. We measured cytokines in plasma and IF, whereas matrix metalloproteinase (MMP) activity and collagen content, as well as the level of glycosaminoglycans and hyaluronan were determined in hind limb muscle. In vivo fatigue protocols of the soleus muscle were performed at 42 and 112 days after induction of heart failure. We found that the MMP activity and collagen content in the skeletal muscles increased significantly at 42 days after induction of CHF, and these changes were time related to increased skeletal muscle fatigability. These parameters returned to sham levels at 112 days. VEGF in IF was significantly lower in CHF compared with sham-operated rats at 3 and 10 days, but no difference was observed at 112 days. We conclude that temporary alterations in the ECM, possibly triggered by VEGF, are related to a transient development of skeletal muscle fatigue in CHF.

Changes in plasma protein extravasation in rat skin during inflammatory challenges evaluated by microdialysis

Docetaxel and prostaglandin E1 (PGE1) increase transcapillary albumin extravasation and reduce interstitial fluid pressure in the skin. In this study the microdialysate concentration (Cm) of 125I-labeled human serum albumin (125I-HSA) and different-sized endogenous plasma proteins (EPP) was compared to evaluate changes in transcapillary extravasation of plasma proteins. 125I-HSA was also used to estimate changes in the specific activity of albumin. Extravasation of 125I-HSA and EPP from plasma to interstitium in the rat skin was compared during continuous administration of docetaxel and PGE1 by using microdialysis in anesthetized rats. Also, 20 ml of Ringer solution (RS) were injected intravenously during 10 min in a separate group. Two hollow plasmapheresis fibers (3 cm, cut off 3,000 kDa), one acting as control, were placed subcutaneously on the back skin and perfused with RS (5 μl/min, 140 min, collected every 10 min). The size of the different EPP was estimated to be 73, 65, 56, 47, and 39 Å, separated by a size-exclusion high-performance liquid chromatography column and quantified by UV detection (280 nm). Docetaxel (0.5 mg/ml, n = 5) increased Cm of 125I-HSA and EPP of sizes 73, 65, 56, and 39 Å significantly ( P < 0.05) compared with control. PGE1 (20 μg/ml, n = 6) increased Cm of 125I-HSA significantly ( P < 0.05) but none of the different-sized EPP was increased compared with control. Intravenous RS (20 ml, n = 6) increased Cm of 125I-HSA and increased all the different-sized EPP significantly ( P < 0.05) compared with control. Although the microdialysis method is able to monitor qualitative changes in capillary permeability, a quantitative determination of the capillary reflection coefficient or permeability-surface area product was not possible, because steady state between plasma and dialysate was not achieved during the measurement period. The different pattern of extravasation of EPP and 125I-HSA after docetaxel, PGE1, and RS indicates increased interstitial transport rate and/or increased capillary permeability after docetaxel and RS, whereas PGE1 seems to increase transcapillary fluid flux without altering the permeability.

Platelet activating factor (PAF) increases plasma protein extravasation and induces lowering of interstitial fluid pressure (P) in rat skin

AIM

To investigate the ability of the microdialysis technique to measure capillary selectivity of different sized plasma proteins induced by local administration of platelet activating factor (PAF).

METHODS

We used hollow plasmapheresis fibres with 3 cm membrane (cut off 3000 kDa) placed on the back of anaesthetized rats.

RESULTS

Platelet activating factor (50 microg mL(-1)) administered locally via the fibre, increased extravasation of radiolabelled 125I-HSA from plasma to the microdialysis fibre by approximately 900% compared both to baseline and the control fibre within 70 min (n = 6, P < 0.05). The extravasation in the control fibre did not change over time. HPLC measurement of plasma proteins in the microdialysis perfusate also demonstrated decreased capillary selectivity for proteins in the diameter range of 73 A, 56 A and 39 A after local administration of PAF (n = 6, P < 0.05). PAF also significantly lowered interstitial fluid (P(if)) pressure after subcutaneous administration (50 microg mL(-1)). Mean arterial pressure (MAP) after intravenous injection of PAF (0.4 microg kg(-1)) fell instantly by about 50 mmHg, and stabilized at 50 mmHg after 15 min (n = 6). MAP was unaltered when PAF was given through the microdialysis fibre (n = 4). Both total tissue water (TTW) and extravasation of albumin, measured as the plasma-to-tissue clearance (E-alb) showed a significant increase after PAF (n = 7, P < 0.05).

CONCLUSIONS

The present study demonstrates that PAF induces plasma protein extravasation and decrease capillary selectivity of different sized plasma proteins. It also increases transcapillary fluid flux, and lowers P(if), indicating a role for PAF in the interstitium for generation of transcapillary transport of water and large molecules followed by formation of oedema.