Transcapillary colloid osmotic gradient and body fluid volumes in renal failure

The aim was to study the transcapillary fluid balance in dialysis patients during and after ultrafiltration. Plasma and subcutaneous interstitial fluid (wick technique) colloid osmotic pressure, plasma volume (I125-albumin space) and extracellular fluid volume (radiosulfate space) were measured in nine patients on maintenance hemodialysis before (pre-dialysis state) and after (dry-weight state) ultrafiltration. In the pre-dialysis state, interstitial colloid osmotic pressure was reduced compared to normal controls (12.7 +/- 3.5 versus 15.8 +/- 2.7 mmHg, mean values +/- SD) and transcapillary colloid osmotic gradient increased (15.3 +/- 3.0 versus 12.8 +/- 2.7 mmHg). Ultrafiltration resulted in a parallel decrease of plasma volume and interstitial fluid volume of 19 to 20%, and an increase in mean interstitial colloid osmotic pressure of 3.4 mmHg and in mean transcapillary colloid osmotic gradient of 1.9 mmHg. The mean ultrafiltration rate was 21.9 +/- 1.9 ml/min and the plasma refilling rate was 16.5 +/- 2.7 ml/min. It is concluded that the changes in plasma and interstitial fluid colloid osmotic pressure tend to preserve plasma volume and limit the interdialytic increase in interstitial fluid volume.     

Transcapillary colloid osmotic pressures in injured and non-injured skin of seriously burned patients

Thermal skin injury is accompanied by rapid and excessive oedema formation implicating a dramatic increase in the transcapillary fluid transport. In order to clarify the pressure changes occurring across the microvasculature after a thermal skin injury we have measured colloid osmotic pressures (COP) in interstitial fluid (COPi) of injured and non-injured skin as well as in plasma (COPp) from patients suffering major cutaneous burns. Interstitial fluid was collected with a wick-technique and analysed for COP. Measurements were performed as early as 6 h and continued until 56 h after injury. A severe hypoproteinaemia occurred in all patients with a marked reduction in COPp down to about 10 mmHg. Up to 12h post-burn we found a higher COPi in injured skin than in plasma. The first measurement of COPp averaged 9.8 mmHg as compared to an average COPi of 11.1 and 9.3 mmHg in injured and non-injured skin respectively. Measurements performed later than 12h showed a return of the transcapillary COP gradient towards the normal direction (COPp greater than COPi). The gradient was considerably less than in a normal situation. Based on the present observations of transcapillary COP it is suggested that colloids should be withheld until the transcapillary COP gradient returns to the normal direction.     

Relation of hypoxia and edema of the intestinal wall and skin to colloid osmotic pressure

Whereas the impact of colloids and crystalloids on hypoxia and edema has been extensively debated with respect to pulmonary function, their corresponding effects on the systemic circulation have been largely ignored. Manifest edema of the intestine and skin develops, however, when the serum colloid osmotic pressure (COP) is lowered to 15 mm Hg or less by crystalloid infusions. Hypoxia of wounds, which may be aggravated by crystalloids, impairs healing and antibacterial defense, and its has been speculated that edema and/or hypoxia of the intestine may be associated with postoperative gastrointestinal dysfunction. We therefore studies the relationship between lowering and restoration of the COP, the pO2 of the intestinal surface and skin, and tissue edema. We generated an acute hypoproteinemic fluid overload reducing the COP from around 20 to 10 mm Hg in 56 rabbits by means of a 50% plasma loss and excess replacement with Ringer's lactate. We measured the COP with a membrane having a cut-off level of 20,000 d, the cardiac output (with derivation of further hemodynamic data) with an electromagnetic flow probe around the ascending aorta, and the tissue pO2 (pO2t) in mm Hg with the Dortmund 8-channel surface electrode. After 30 min without infusion (Fig. 1), we assigned 14 animals each at random to 4 treatment groups: (1) no treatment (O); (2) 20% albumin 7.5 ml/kg (A); (3) furosemide 2 mg/kg i.v. given three times at 30-min intervals (F); and (4) the combination of both agents (AF). During the infusion-free interval, the cardiac output and pO2t fell by 20%-30% of baseline (Table 1).(ABSTRACT TRUNCATED AT 250 WORDS)     

Postoperative albumin infusion therapy based on colloid osmotic pressure. A prospectively randomized trial

In a prospectively randomized trial of 220 patients, 106 were given albumin when their colloid osmotic pressure (COP) fell below 24 cm H2O and 114 were given albumin when their COP fell below 29 cm H2O. There was no difference in the postoperative course between the two groups; however, by using the lower COP limit the postoperative albumin consumption in the intensive care unit was reduced significantly and thus the costs of treatment were lowered. In the case of extremely low COP, the prognosis of the disease worsened, indicating that the COP is of prognostic value. The albumin supply, however, did not influence the final outcome of the patients under these circumstances because it treated only a characteristic symptom and not the cause of the disease.     

目标导向液体治疗中晶体液和胶体液对血管内皮多糖包被的影响

目的探讨在相同目标导向液体治疗(GDFT)策略下,晶体液和胶体液对血管内皮多糖包被的影响。方法选取拟于我院行择期腹膜后肿瘤切除手术的患者80例,男,50例,女,30例,ASAⅠ或Ⅱ级,依据随机数字表法分为晶体液组和胶体液组,每组40例。两组患者均以1.5ml·kg~(-1)·h~(-1)连续输注复方乳酸钠以维持基础补液量,连接FloTrac/Vigileo系统监测每搏量变异度(SVV)和心脏指数(CI),并将SVV≤12%、CI≥2.5L·min~(-1)·m~(-2)和MAP≥60mmHg作为目标进行GDFT,晶体液组液体冲击采用复方乳酸钠,胶体液组液体冲击采用羟乙基淀粉130/0.4氯化钠注射液。记录入室、手术开始1、4h、术后24、72h的血清多糖包被降解产物蛋白聚糖~(-1)(SCD~(-1))、透明质酸(HA)和硫酸乙酰肝素(HS)的浓度;记录术中输液总量和术后恶心呕吐(PONV)、切口感染、肺部并发症和急性肾损伤(AKI)等发生情况。结果与入室比较,两组血清多糖包被降解产物在手术开始1、4h、术后24、72h均呈不同程度增加,手术开始4h升至最高,且于术后逐渐回落,但术后72h仍高于入室;术后24、72h,胶体液组血清多糖包被降解产物明显高于晶体液组(P0.05)。胶体液组术中输液总量明显少于晶体液组(P0.05)。两组患者PONV、切口感染、肺部并发症和AKI发生率差异无统计学意义。结论在相同液体管理策略下,胶体液虽然可以在一定程度上减少液体输注量,但也会对血管内皮多糖包被产生更加持久和严重的破坏。     

Effect of intraoperative fluid administration and colloid osmotic pressure on the formation of intestinal edema during gastrointestinal surgery.

The effects of intraoperative changes in plasma colloid osmotic pressure (COP) on the formation of intestinal edema were studied in patients during modified Whipple's operation (hemipancreato-duodenectomy). Eighteen patients (ASA physical status I or II) were randomly assigned to one of three groups. They received either lactated Ringer's (RL group, n = 6), 10% hydroxyethyl starch (HES group, n = 6), or 20% human albumin (HA group, n = 6) as a volume replacement solution, which was given to maintain central venous pressure (CVP) at the preoperative level. Jejunal specimens were obtained after the first transsection of the jejunum and prior to the jejuno-jejunostomy. Their water fraction (g H2O/g tissue dry weight) was measured gravimetrically. COP was determined prior to induction of anesthesia and upon removal of the second jejunal sample. In the RL group, 3,850 +/- 584 ml (data are means +/- SEM) of volume replacement solution were infused from induction of anesthesia to removal of the second jejunal sample. In the HES group, 1,358 +/- 45 ml were infused, and in the HA group, 463 +/- 49 ml were infused. During this time, COP decreased from 20.3 +/- 0.5 mmHg to 14.1 +/- 0.6 mmHg in the RL group, remained at 22.0 +/- 0.9 mmHg in the HES group, and increased from 20.7 +/- 0.9 mmHg to 28.1 +/- 0.9 mmHg in the HA group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Post-traumatic changes in, and effect of colloid osmotic pressure on the distribution of body water.

The aim of this study was to define the post-traumatic changes in body fluid compartments and to evaluate the effect of plasma colloid osmotic pressure (COP) on the partitioning of body fluid between these compartments. Forty-two measurements of plasma volume (green dye), extracellular volume (bromine), and total body water (deuterium) were done in ten traumatized patients (mean Injury Severity Score, ISS, = 34) and 23 similar control studies were done in eight healthy volunteers who were in stable fluid balance. Interstitial volume, intracellular volume, and blood volume were calculated from measured fluid spaces and hematocrit; COP was directly measured. Studies in volunteers on consecutive days indicated good reproducibility, with coefficients of variation equal to 3.5% for COP, 6.3% for plasma volume, 4.5% for extracellular volume, and 4.9% for total body water. COP values extended over the entire range seen clinically, from 10 to 30 mmHg. Interstitial volume was increased by 55% in patients, but intracellular volume was decreased by 10%. We conclude (1) that posttraumatic peripheral edema resulting from hemodilution is located in the interstitial compartment, with no intracellular space expansion; and (2) that interstitial volume, but not intracellular volume, is closely related to plasma COP.     

Parenteral fluid therapy in septic shock: An evaluation of crystalloid and colloid

A retrospective review of 25 patients with bacteremic shock was undertaken to evaluate and compare the quality of resuscitation with infusion of either crystalloid or colloid solutions. The average improvement in systolic pressure in the crystalloid infusion group was 23 mm of Hg, whereas the colloid group achieved a mean rise in pressure of 48 mm. Colloid was also superior to crystalloid in terms of speed and magnitude of response measured. In the group of 8 patients given colloid, central venous pressure was recorded over the 24-hour infusion period with a mean rise of 8 cm of water produced, vs. 2 cm of water in the crystalloid group. Crystalloid administration aggravated arterial hypoxemia, whereas colloid infusion did not worsen respiratory function. All 25 patients were oliguric or anuric before beginning therapy; adequate urine flow was quickly restored by expanding blood volume alone, with the fusion of a large volume of salt and water unnecessary. Hence, it is concluded that salt solutions should not be given in cases of bacteremic shock, unless clear indications of deficits or continuing losses of sodium and water are present. Excessive sodium administration was an unreliable and ineffective blood volume expander, accentuated hypoalbuminemia, and increased pulmonary shunting and hypoxemia. Prompt blood pressure and central venous pressure elevation, and restoration of urine flow, can be achieved with colloid solution.     

The effect of colloid osmotic pressure in human spermatozoa exposed to hypoosmotic conditions

The use of a protein source such as serum and albumin had been extensively employed as supplements of culture media for handling and culture of gametes and embryos. Protein molecules behave as colloids in solution and contribute to the osmotic pressure of fluids. The interaction of proteins in solution and spermatozoa needs to be assessed in order to determine their possible role in osmoregulation. The aim of this study was to assess possible osmoregulatory mechanisms of protein supplementation against exposure to hypoosmotic conditions by assessing the sperm's response to those environments. A stock hypoosmotic solution (HOS) was prepared by using a mixture of fructose and sodium citrate and adjusted to an osmotic pressure of 150 mOsm l-1. Another stock solution was prepared by diluting a preparation of synthetic serum supplement [SSS; 6% (v/v) total protein] with distilled water to obtain an osmotic pressure of 150 mOsm l-1 (hypoosmotic SSS or H-SSS). Three additional solutions were prepared by mixing the stock HOS and H-SSS solutions in the following proportions (v/v): (i) 75% H-SSS/25% HOS, (ii) 50% H-SSS/50% HOS and (iii) 25% H-SSS/75% HOS. Aliquots of washed spermatozoa from 18 men were diluted 1 : 10 (v/v) with each of the testing solutions and incubated for 60 min. Specimens were assessed on wet mounts for total and specific swelling patterns. Swelling patterns were classified as maximal (>50% tail length swollen) and minimal (<50% tail length swollen) swelling with or without associated sperm motility. The major finding of this study was that increasing the concentration of protein supplementation resulted in a decrease in the proportion of maximal sperm tail swelling patterns and an increase in the proportion of minimal tail swelling patterns. A proportion of spermatozoa which exhibited minimal swelling patterns were still motile in all solutions tested, and the percentage of those spermatozoa increased as the protein supplementation was also increased in the testing solutions. Incorporation of protein supplementation as described in this study delays the effect of sperm swelling in hypoosmotic conditions.     

The importance of plasma colloid osmotic pressure for interstitial fluid volume and fluid balance after elective abdominal vascular surgery.

The relationships between plasma colloid osmotic pressure (COPp) and interstitial fluid volume (IFV) as well as postoperative fluid balance were investigated in a prospective study involving 53 patients undergoing elective abdominal aortic reconstruction. The patients were divided into four groups according to pre- and postoperative blood replacement and fluid therapy programs whereby a continuum of postoperative COPp-values between 33 and 16 mmHg was obtained. Measurements were done before the operation and on days 1 and 4 after surgery. After surgery, COPp below 20 mmHg led to increased IFV. On day 1, COPp was linearly correlated to the total amount of fluid retained during the day of operation. A positive fluid balance of 3 L on this day ensured unchanged extracellular fluid volume (ECV). Of the 3 L, 1.5 L was insensible water loss and 1.5 L had moved into the cells. On day 4 after surgery, COPp below 22 mmHg was associated with increased plasma volume. The authors suggest that COPp be maintained above 20 mmHg after major surgery, and positive fluid balance should not exceed 5 L during the day of operation.     

Laser-induced photoacoustic injury of skin: effect of inertial confinement

Argon-fluoride (ArF) excimer laser-induced acoustic injury was confirmed by ablating the stratum corneum (s.c.) inertially confined by water in vivo. Hairless rats were irradiated through a quartz chamber with flowing distilled water or air and a 2.5 mm aperture. The laser was adjusted to deliver 150 mJ/cm2 at the skin surface for both conditions. Partial and complete ablation of the s.c. was achieved with 12 and 24 pulses, respectively. Immediate damage was assessed by the transmission electron microscopy. Partial ablation of the s.c. through air produced no damage, whereas partial ablation through water damaged skin to a mean depth of 114.5 +/- 8.8 microns (+/- SD). Full thickness ablation of the s.c. through air and water produced damage zones measuring 192.2 +/- 16.2 and 293.0 +/- 71.6 microns, respectively (P less than 0.05). The increased depth of damage in the presence of inertial confinement provided by the layer of water strongly supports a photoacoustic mechanism of damage. The damage induced by partial ablation of the s.c. provides evidence that photochemical injury is not a significant factor in the damage at a depth because the retained s.c. acts as a partial barrier to diffusion of photochemical products. Combined with our previous studies, these experiments demonstrate that pressure transients are responsible for the deep damage seen with 193 nm ablation and that photoacoustic effects must be considered when using short-pulse, high-peak power lasers.     

Thermal injury induces expression of CD14 in human skin

BACKGROUND: Skin is equipped with an array of immune mediators aimed at fighting invading microbes. CD14 has been shown to play a key role in modulating the activation of cells by LPS. Since LPS levels within burn wounds are often found to be elevated, we sought to examine the expression of CD14 within human skin following thermal injury. METHODS: Patients who sustained partial thickness burns, were recruited into the study (n=57). Total RNA was isolated from both burn and normal (control) skin. Northern blot analysis and TaqMan RT-PCR were used to determine skin CD14 mRNA levels. Immunohistochemistry was used to localize CD14 expression in burned and normal skin. RESULTS: Quantitative PCR showed significantly increased CD14 expression levels in the immediate post-burn period (P<0.05 burn versus non-burn). Immunohistochemistry revealed more pronounced CD14 staining 24 h after the injury, reaching normal levels approximately 5-7 days post-burn. CONCLUSION: CD14 expression peaks within the first week post-burn before declining, reaching normal levels after 14 days. This loss of supranormal CD14 expression locally within the wound may contribute to a weakened host defense response 5-6 days after injury, when patients become especially vulnerable to infection.     

The influence of thoracic epidural analgesia on transcapillary fluid balance in subcutaneous tissue

Clinical observation and calculation of fluid balance have shown that patients undergoing aortocoronary bypass surgery with thoracic epidural analgesia (TEA) in addition to general anesthesia retain less fluid than patients having general anesthesia only. The present study was designed to investigate whether this effect could be explained by thoracic epidural analgesia influencing the transcapillary fluid balance, i.e. the transcapillary forces (COPpl, COPif, Pif). Interstitial fluid colloid osmotic pressure (COPif) and interstitial fluid pressure (Pif) were measured subcutaneously at heart level by the blister suction technique and the wick-in-needle technique, respectively. Simultaneously plasma colloid osmotic pressure (COPpl) was recorded. Sixteen male patients were allocated to two groups, one having general anesthesia only (controls, n = 8). The other group (TEA, n = 8) received, at the induction of anesthesia, bupivacaine 50 mg via an epidural catheter as an adjunct to general anesthesia. TEA was maintained by continuous infusion for 24 h postoperatively. Preoperatively no intergroup differences were observed in "the Starling forces" (COPpl, COPif, Pif). At the start of extracorporeal circulation COPpl was significantly lower in the TEA-group than in controls. During extracorporeal circulation the transcapillary COP-gradient (COPpl-COPif) was reversed in both groups. At the end of extracorporeal circulation Pif increased to a minor degree in the TEA-group and remained significantly lower than in controls from 3 to 24 h postoperatively. The subcutaneous interstitial tissue could be less expanded postoperatively in the TEA-group, also reflected by a lower increase in Pif.     

Crystalloid versus colloid fluid resuscitation: a meta-analysis of mortality

Controversy persists over the best choice of fluid to use for resuscitation. A number of published articles promote the use of either colloid or crystalloid fluids. Most of the arguments for use of one fluid or the other are based on cardiopulmonary data collected during and after fluid resuscitation. Although many studies report the mortality rate of patients treated with both fluids, none have critically analyzed this most important aspect of therapy. Meta-analysis is a relatively new statistical method whereby data from a number of clinical trials can be pooled to produce more reliable data. In this study meta-analysis was used to pool mortality data from reports of eight previously published, randomized, clinical trials, in which the efficacy of crystalloid and colloid fluid resuscitation was compared. The overall treatment effect when the data from all the clinical trials were pooled showed a 5.7% relative difference in mortality rate in favor of crystalloid therapy. When the data from only those studies using trauma patients were pooled, the overall treatment effect showed a 12.3% difference in mortality rate in favor of crystalloid therapy. However, when data from studies that used nontrauma patients were pooled, there was a 7.8% difference in mortality rate in favor of colloid treatment. In patients with trauma who are septic and in whom the capillary leak syndrome leads to adult respiratory distress syndrome, it may be assumed that colloid resuscitation would be no better than crystalloid resuscitation. In this study the meta-analysis of published data showed that this form of treatment is deleterious. In patients who are nonseptic or having elective surgery, however, the basement membrane is intact, and meta-analysis of data in this setting showed that treatment with colloids would be efficacious.