Plasma fibronectin and complement in surgical patients

Effect of high-protein peptide-based formula compared with isocaloric isonitrogenous polymeric formula in critically ill surgical patient

BACKGROUND

Malnutrition is common in critically ill patients, and it is associated with an increased risk of complications. Early enteral nutrition with adequate caloric and protein intake is critical nevertheless it is difficult to achieve. Peptide-based formulas have been shown to be beneficial in patients with feeding intolerance. However, there are limited studies showing the efficacy and safety of high-protein peptide-based formula in critically ill surgical patients.

AIM

To determine the effects of a high-protein peptide formulation on gastrointestinal tolerance, nutritional status, biochemical changes, and adverse events in patients in the surgery intensive care unit (SICU) compared to an isocaloric isonitrogenous standard polymeric formulation.

METHODS

This study was a multi-center double-blind, randomized controlled trial. We enrolled adult patients in the surgical intensive care unit, age ≥ 15 years and expected to receive enteral feeding for at least 5-14 d post-operation. They were randomly assigned to receive either the high-protein peptide-based formula or the isocaloric isonitrogenous standard formula for 14 d. Gastric residual volume (GRV), nutritional status, body composition and biochemical parameters were assessed at baseline and on days 3, 5, 7, 9, 11, and 14.

RESULTS

A total of 19 patients were enrolled, 9 patients in the peptide-based formula group and 10 patients in the standard formula group. During the study period, there were no differences of the average GRV, body weight, body composition, nutritional status and biochemical parameters in the patients receiving peptide-based formula, compared to the standard regimen. However, participants in the standard formula lost their body weight, body mass index (BMI) and skeletal muscle mass significantly. While body weight, BMI and muscle mass were maintained in the peptide-based formula, from baseline to day 14. Moreover, the participants in the peptide-based formula tended to reach their caloric target faster than the standard formula.

CONCLUSION

The study emphasizes the importance of early nutritional support in the SICU and showed the efficacy and safety of a high-protein, peptide-based formula in meeting caloric and protein intake targets while maintaining body weight and muscle mass.

Monitoring the response to injury

Tissue trauma leads to a severity-dependent activation of plasma and cellular systems. This response can be recorded by determining parameters which represent the activation state of these systems. In severely injured patients with multiple trauma three out of 14 parameters measured at the time of admission proved to be indicators of subsequent septic complications with a high degree of accuracy: Fibrinopeptide A (FPA--the first split product of fibrinogen), the C3 split product C3a, and the elastase-alpha 1 proteinase inhibitor-complex (E alpha 1 PI). In a second series of multiple-injured patients with femoral fractures who did not develop clinical sepsis (N = 25) these parameters were measured continuously to evaluate the influence of injury severity and of therapeutic strategy on the further course. We found a strong correlation between injury severity (ISS) and the degree of activation. The signs of activation decreased rapidly following immediate operative fixation, and remained elevated or even increased after primary femoral traction and secondary stabilization. The operative procedure did not cause any additional activation. Complications such as infection or the formation of haematomas were reflected by raised parameter levels.

Pulmonary hypertension and polymorphonuclear leukocyte elastase after esophageal cancer operations

To evaluate the role of polymorphonuclear leukocyte (PMN) elastase in pulmonary impairment occurring after operation for esophageal cancer, 10 patients were randomized preoperatively into two equal groups. One group received a placebo infusion and the other, an infusion of the PMN elastase inhibitor ulinastatin. In the placebo group, the mean plasma PMN elastase level increased from 154 +/- 23 micrograms/L preoperatively to 449 +/- 56 micrograms/L at 6 hours postoperatively (p less than 0.01), whereas the mean plasma fibronectin concentration decreased from 490 +/- 70 micrograms/mL preoperatively to 265 +/- 81 micrograms/L on postoperative day 2 (p less than 0.01). The mean pulmonary vascular resistance increased markedly from 151 +/- 24 dynes.s.cm-5.m-2 preoperatively to 284 +/- 76 dynes.s.cm-5.m-2 at 6 hours postoperatively (p less than 0.01). In the group given ulinastatin, 150,000 units every 12 hours from the start of the operation, the mean PMN elastase value at 6 hours postoperatively was lower (275 +/- 66 micrograms/L; p less than 0.01) and the fibronectin level on postoperative days 1 and 2, higher (p less than 0.05). A lower pulmonary vascular resistance was noted into day 2 (p less than 0.05). Our results suggest that PMN elastase may participate in the development of postoperative pulmonary impairment.

Plasma fibronectin and complement following infusion of colloidal solutions after spinal anaesthesia

A randomized study of 30 patients undergoing uncomplicated surgery under spinal anesthesia was conducted to assess the influence of colloids on the kinetics of plasma fibronectin and complement. Both are opsonins of the reticuloendothelial system; moreover fibronectin is concerned with host resistance against septic complications following trauma and surgery. The patients were assigned to receive either Ringer's lactate (Group 1), gelatin (Group 2) or dextran 40 (Group 3). Blood samples were withdrawn before colloids or Ringer's infusion and during the 4 postoperative days. There was a reduction in plasma fibronectin throughout the study in groups 1 and 3, but an increase in group 2 by 24 h. The adhesion of plasma fibronectin to gelatin was maximal 1 h after infusion (44%) and remained significant up to day 2 in group 2. There was no relationship in groups 1 and 3. C3 and C4 components of complement exhibited a low value in the early post-operative period, due to hemodilution. This study shows an in vivo fibronectin-gelatin interaction, and suggests that gelatin infusion inhibits the increased shift of plasma fibronectin at the site of tissue injury after surgery.

Protein and energy metabolism with biosynthetic human growth hormone in patients on full intravenous nutritional support

Our objective was to examine the effect of biosynthetic human growth hormone (BSHGH) on protein and energy metabolism in patients on full intravenous nutrition (IVN). Fifteen patients who had been established on IVN were allocated at random to receive either BSHGH (0.1 mg/kg/day) or placebo daily for 7 days. All patients received the same feeding regimen which contaminated 14 gN, 1000 kcal of glucose and 1000 kcal of fat (Intralipid) daily. The mean nitrogen balance for days 4 to 7 was significantly more positive with BSHGH (7.0 +/- 0.6 gN/day) than with placebo (4.4 +/- 0.7 gN/day). The BSHGH group were lighter (53 +/- 4.6 kg body weight) than controls (68 +/- 5.1 kg), but the difference was not significant. Resting energy expenditure (expressed as percentage of day 1) increased throughout the study in patients receiving BSHGH (day 7, 120.8 +/- 5.5%), whereas in patients receiving placebo it remained stable (day 7, 98.9 +/- 2.7%). The nonprotein respiratory quotients were similar for BSHGH (mean days 4-7, 0.94 +/- 0.04) and placebo (mean days 4-7, 0.93 +/- 0.01) (p greater than 0.05). This study demonstrates more positive nitrogen balance, which may in part be due to different substrate loads, and an increase in energy expenditure in patients receiving BSHGH.

Monitoring of the inflammatory response in early peritonitis

The inflammatory response which is similar in all forms of peritonitis was recorded by determining the levels of parameters shown to represent the activation state of plasmatic and cellular systems as well as the inhibitory capacity of the plasma. In a selected series of patients with different underlying diseases, blood sampling was started at the time of admission when the clinical finding of an acute abdomen led to emergency laparotomy. Depending upon the duration of the illness and the severity of the peritonitis, a significant increase in fibrinopeptide A and of C3a could be detected within a few hours, which was followed by an increase in the elastase alpha-1-proteinase inhibitor complex. Differences due to variable cause could not be found. There was a striking correlation between the preoperative values of these three parameters and the postoperative course of the patients. Additionally, there was a significant enhancement of an endothelial proliferation-inhibiting capacity in the serums of the lethal group, whereas endotoxin could only be detected in trace amounts in four patients with intraabdominal infection in the preoperative period.

Plasma fibronectin in Crohn's disease

The hypothesis that abnormal fibronectin metabolism in Crohn's disease could be an important mechanism leading to stricture formation or postoperative infection was tested in three related studies. (1) Lower concentrations of plasma fibronectin (p less than 0.05) were found in 20 patients with small and large bowel Crohn's disease (mean 0.24 g/l) compared with 13 patients with more limited disease confined to only small or only large bowel (mean 0.27 g/l) or 20 healthy controls (mean 0.29 g/l). (2) In 25 patients followed for 10 days after operation for Crohn's disease, there was a significant fall in fibronectin concentrations of 43% (p less than 0.01, Wilcoxon's rank-sum test). This fall was maximal on the second postoperative day and was more marked in patients undergoing more major operative procedures. (3) The predictive value of plasma fibronectin for subsequent stricture formation or progression was studied for one year; during which 10 patients developed strictures requiring operative treatment. Higher plasma fibronectin concentrations were related to stricture formation, although there was not a complete, predictive relationship. In this study we found that plasma fibronectin concentrations were low in patients with extensive or severe Crohn's disease, fall after operation and may be related to the risk of stricture formation. This relationship is unlikely to be of clinical value, although it shows the potential significance of fibronectin in the pathogenesis of strictures.

Reticuloendothelial failure in chronic intra-abdominal sepsis: the role of opsonic fibronectin

Severe sepsis leads to depression of the reticuloendothelial (RE) system with delayed bloodstream clearance of particulate matter and bacteria. Fibronectin may be an important opsonin of the RE system and low fibronectin levels often accompany severe sepsis in man. We have investigated the effect of prolonged intra-abdominal sepsis on plasma fibronectin concentrations and RE function. Serial plasma fibronectin concentrations were determined in rabbits for 2 weeks after either the induction of sepsis (appendix abscess) (n = 6) or laparotomy only (n = 6). RE function was measured at 2 weeks by determining the clearance kinetics and organ distribution of low dose technetium tin colloid (TTC). There was an early transient depression in plasma fibronectin values followed by elevated concentrations at 48-72 h which were more marked in the sepsis group. There was a delay in the blood clearance with reduced hepatic and increased bone uptake of TTC. We conclude that depletion of opsonic fibronectin is unlikely to be an important factor contributing to the impairment of RE function associated with intra-abdominal sepsis and that RE depression in septic animals is due to intrinsic Kupffer cell dysfunction.

Plasma fibronectin and complement activation in coronary bypass surgery

In patients with severe sepsis, plasma fibronectin concentrations are reduced and complement is activated. It is not known whether complement activation interferes with plasma fibronectin. Cardiopulmonary bypass is known to activate complement. We have therefore used this operation to study the effect of complement activation on plasma fibronectin in the absence of sepsis. After 15 min of bypass the percentage changes of plasma fibronectin and haematocrit were similar (65.9 +/- s.e.m. 4.8 and 67.0 per cent +/- s.e.m. 2.3, respectively), but the changes in C3 and C5 (58.4 +/- s.e.m. 4.8 per cent and 52.5 per cent +/- s.e.m. 2.1) were significantly greater than those of the haematocrit, indicating complement consumption. During the first 60 min of bypass there was a significant increase in the neutrophil count which is compatible with complement activation. It is unlikely that complement activation alone, in the absence of sepsis, contributes to the reduction of plasma fibronectin concentrations.

Fibronectin and the critically ill patient: current status

In summary, deficiency of plasma fibronectin has now been documented in a variety of clinical entities. Persistently low fibronectin may have prognostic value, and in certain patients may provide a clue to occult sepsis and potential organ failure. The clinical benefit of infusion of fibronectin-rich cryoprecipitate or purified human plasma fibronectin has yet to be determined in well-controlled randomized clinical trials. However, if such results become available then infusion of plasma fibronectin may provide a valuable therapeutic modality in the care of the critically-ill patient.

Opsonic dysfunction secondary to plasma fibronectin depletion after aortic surgery

Fibronectin is a plasma opsonin which is depleted after major injury or surgery. The effect of major aortic surgery on plasma fibronectin has been studied in patients and in an equivalent experimental model in pigs. On the day after aortic surgery in eleven patients mean fibronectin (+/- s.e.m.) had fallen from 363 +/- 11 mg/l pre-operatively to 179 +/- 19 mg/l (P less than 0.01). No such fall was observed in patients undergoing herniorrhaphy. In fourteen pigs aortic surgery produced reproducible surgical shock and a fall in plasma fibronectin from 331 +/- 10 mg/l to 43 +/- 13 mg/l after resuscitation (P less than 0.01). Whenever plasma fibronectin fell below 190 mg/l the circulating free fibronectin was consumed in complexes of 1000 kDa containing collagenous debris. More severe depletion of plasma fibronectin was related to higher concentrations of circulating nonopsonized collagenous debris and to subsequent mortality in pigs. The depletion of free fibronectin that occurs following major surgery may produce clinically important opsonic dysfunction. The clinical relevance of this fibronectin consumption may be missed if measurement is limited to circulating fibronectin levels without determining that proportion bound in complexes and no longer available as an opsonin.

Changes in plasma fibronectin during acute nutritional deprivation in healthy human subjects

1. Plasma fibronectin, a glycoprotein, is an opsonin of the reticuloendothelial system. 2. In ten healthy volunteers starved for 4.5 d, daily measurements showed a rapid reduction in plasma fibronectin, no alteration in either C3 or plasma transferrin and, at the end of the starvation period, an elevated serum albumin. 3. On refeeding, plasma fibronectin rapidly returned to its prestarvation level but plasma transferrin was significantly reduced and did not recover by the end of the study. 4. Changes in plasma fibronectin may be a sensitive index of nutritional status. The reduction of plasma fibronectin in short-term starvation may compromise host defence tolerance of injury and sepsis.

[Changes in levels of plasma fibronectin after surgery for digestive cancer]

Fibronectin is a large, adhesive glycoprotein, also called opsonic alpha 2 surface-binding glycoprotein. This glycoprotein which participates in all adhesions may modulate wound healing; plasma fibronectin, because it is opsonically active, may mediate reticulo-endothelial activity. Citrated plasma samples were analysed from twenty surgical patients with digestive cancer. The samples were obtained preoperatively and on 1st, 3rd, 7th, 14th and 28th postoperative days. Fibronectin assay was made by laser immunonephelometry. Other samples were obtained from a population of 340 healthy male and female subjects whose age ranged from 10 to 70 years, so that reference could be made to the standard mean of fibronectin related to the age of each patient. In the surgical patients, there was a significant decrease in fibronectin from the first to the third postoperative day. On the 7th day, there was a secondary increase of fibronectin levels which exceeded the preoperative values at the 14th and 28th days. There was no plasma dilution when the samples were collected, this being shown by protidaemia, osmolarity and haematocrit which were measured at the same time. "Septic" and "non septic" patients were compared. For septic patients, fibronectin levels were lower and the secondary increase occurred later than in the non septic patients. Patients with no secondary increase did not recover and died. Fibronectin levels were compared with other classical parameters of nutritional assessment, i.e. albumin, prealbumin, transferrin and urinary creatinine indexes. These parameters were not well correlated. However, this study may indicate the usefulness of fibronectin as an indicator of nutritional status and of non specific host defence.