Dextran metabolism following infusion of 7.5% NaCl/6% dextran-70 to euvolemic and hemorrhaged rabbits

Small-volume resuscitation: from experimental evidence to clinical routine. Advantages and disadvantages of hypertonic solutions

BACKGROUND

The concept of small-volume resuscitation (SVR) using hypertonic solutions encompasses the rapid infusion of a small dose (4 ml per kg body weight, i.e. approximately 250 ml in an adult patient) of 7.2-7.5% NaCl/colloid solution. Originally, SVR was aimed for initial therapy of severe hypovolemia and shock associated with trauma.

METHODS

The present review focuses on the findings concerning the working mechanisms responsible for the rapid onset of the circulatory effect, the impact of the colloid component on microcirculatory resuscitation, and describes the indications for its application in the preclinical scenario as well as perioperatively and in intensive care medicine.

RESULTS

With respect to the actual data base of clinical trials SVR seems to be superior to conventional volume therapy with regard to faster normalization of microvascular perfusion during shock phases and early resumption of organ function. Particularly patients with head trauma in association with systemic hypotension appear to benefit. Besides, potential indications for this concept include cardiac and cardiovascular surgery (attenuation of reperfusion injury during declamping phase) and burn injury. The review also describes disadvantages and potential adverse effects of SVR:

CONCLUSION

Small-volume resuscitation by means of hypertonic NaCl/colloid solutions stands for one of the most innovative concepts for primary resuscitation from trauma and shock established in the past decade. Today the spectrum of potential indications involves not only prehospital trauma care, but also perioperative and intensive care therapy.

Effects of storage and homogenization methods on the hepatic recovery of dextrans determined by size-exclusion chromatography

The effects of storage and homogenization methods on the analytical recovery of dextran macromolecules from rat livers were investigated using a high-performance size-exclusion chromatographic (HPSEC) method. Livers were collected from rats dosed with fluorescein-labeled dextrans with molecular weights of 150 or 70 kD. Subsequently, the livers were subjected to different methods to study the effects of the following parameters on the hepatic recovery of dextrans: storage method (freezing the livers before homogenization or freezing the homogenates); contents of the homogenization buffer (addition of 1% Triton X-100); and sample type (HPSEC analysis of the whole homogenate or the supernatant after centrifugation). It is shown that in the absence of Triton in the homogenization buffer, the hepatic recovery of dextrans is substantially affected by all the factors studied. However, in the presence of 1% Triton in the buffer, the hepatic recoveries were maximal and independent of the storage method or sample type. These studies suggest that for optimal recovery of dextran macromolecules from the liver, a sample preparation method capable of disrupting the subcellular membranes should be used.

Molecular weight dependent tissue accumulation of dextrans: in vivo studies in rats

The effects of molecular weight (M(r)) on the serum and urine pharmacokinetics and tissue distribution of dextrans, potential macromolecular carriers for drug delivery, were studied in rats. A single 5 mg/kg dose of fluorescein-labeled dextrans (FDs) with a M(r) of 4000 (FD-4), 20,000 (FD-20), 70,000 (FD-70), or 150,000 (FD-150) was administered into the tail vein of separate groups of rats. At different times after the administration of each FD, animals were sacrificed, and blood, urine, and various tissues were obtained. The concentrations of FDs in the samples were subsequently determined by using a sensitive and specific high performance size exclusions chromatographic method. Among the tissues studied, high accumulation of dextrans was found only in the liver (liver:serum AUC ratios < or = 29) and spleen (spleen:serum AUC ratios < or = 10), with high concentrations in these tissues persisting even at the last sampling time (96 h). In contrast, the serum concentrations of the studied FDs were not measurable beyond 12 h. The serum and urine kinetics and the liver, spleen, and kidney accumulation of FDs demonstrated a significant degree of M(r) dependency. The total and renal clearance of FDs consistently decreased with an increase in M(r). However, the effects of M(r) on the tissue accumulation of dextrans was tissue dependent. For the liver, the tissue:serum AUC ratios increased from 0.346 for FD-4 to 15.2 for FD-20 and 28.8 for FD-70, while a further increase in M(r) to 150 kDa (FD-150) resulted in lowering the ratio to 8.59 in this tissue. For the spleen, the ratios increased from 0.095 for FD-4 to 9.56 for FD-150.(ABSTRACT TRUNCATED AT 250 WORDS)

Acute and subacute toxicity of 7.5% hypertonic saline-6% dextran-70 (HSD) in dogs. 2. Biochemical and behavioral responses

7.5% Hypertonic saline-6% Dextran-70 (HSD) is currently being evaluated in our laboratory as a resuscitation solution for the treatment of hypovolemia at a dose of 4 ml kg-1 body weight. A few reports of dextran toxicity, particularly of the kidney, have been cited in the literature, so the present study evaluated the acute and subacute toxicity of HSD administered i.v. to beagle dogs. In the acute toxicity studies animals were infused with a single dose of HSD, or its components of hypertonic saline (HS) or Dextran-70 (D-70), at the maximum tolerated dose (MTD: 20 ml kg-1). Controls received Ringers lactate (RL). In the HSD-infused dogs, transient but significant increases in serum alanine (ala) aminotransferase (AT), aspartate (asp) AT and alkaline phosphatase (AP) were observed for the first 72 h. In most cases this increase was also observed in the HS group. In the subacute studies, dogs were infused daily with the MTD of the above test solutions. Serum ala AT activity was 2-3-fold higher in the HSD than the RL group for the first 3 days. Again, a similar effect was observed in the HS group. Slight, transient increases in asp AT and AP activity were also observed in the HSD group. Higher lactate dehydrogenase (LDH) activity was only observed at Day 14 in dogs infused with the MTD of HSD or HS. In both studies, no adverse effects on blood urea nitrogen (BUN) or serum creatinine were observed and other transient changes in serum parameters were attributable to hemodilution induced by HSD.(ABSTRACT TRUNCATED AT 250 WORDS)