Tissue oxygenation, anemia, and perfusion in relation to wound healing in surgical patients

Impairment of granulation tissue formation after menopause

Formation of connective tissue is an essential step in the process of wound healing. After menopause an atrophy of connective tissues in skin, bone, and reproductive organs takes place. Using a dead-space wound healing model we measured collagen synthesis and deposition, and cell replication in the granulation tissue of 18 premenopausal and 23 peri- and postmenopausal women not receiving any hormonal therapy. In the postmenopausal group collagen synthesis and deposition and cell number in the granulation tissue were diminished. These results document the impairment of the granulation tissue formation after menopause.

Frequency, manifestations, and correlates of impaired healing of saphenous vein harvest incisions

OBJECTIVE

To describe the frequency, manifestations, and correlates of impaired healing of saphenous vein (SV) harvest incisions in hospitalized patients who had undergone coronary artery bypass grafting (CABG).

DESIGN

Prospective, descriptive, correlational.

SETTING

West Coast university-affiliated medical center.

PATIENTS

Thirty-two English-speaking adults who had undergone CABG.

OUTCOME MEASURES

Impaired wound healing of SV-harvest incisions.

RESULTS

The overall incidence of impaired healing was 43.8%. The most frequent manifestations of impaired wound healing at discharge were prolonged erythema (8/32), prolonged drainage (8/32), and both prolonged erythema and drainage (2/32). Correlates of impaired healing of SV-harvest incisions were body mass index (product-moment correlation = 0.39, p = 0.026) and preoperative use of diuretics (point biserial correlation = 0.42, p = 0.016).

CONCLUSIONS

Impaired healing of SV-harvest incisions in this sample occurred more frequently than previously indicated in the literature. Although severe wound infections were infrequent, a high degree of impaired healing occurred (43.8% of patients who had undergone CABG). Future studies need to explore the long-term effects of impaired healing and test interventions to mitigate impaired healing in this population.

Subcutaneous tissue oxygen pressure: a reliable index of peripheral perfusion in humans after injury

The usual initial life-threatening effect of injury is hypovolemic shock. In the hierarchical physiologic response to hypovolemia, perfusion of peripheral tissues is sacrificed early and restored late. But the usual hemodynamic and metabolic measurements of blood pressure, urine output, and base deficit are not reliable indices of peripheral perfusion. Although the Clark electrode can quantitate tissue oxygen pressure and thereby serve as an index of perfusion, its use is compromised by several technical deficiencies. Recently, an optical method (optode) using fluorescent technology has been developed for measurement of oxygen tension in subcutaneous tissue (P sgO2). Our studies compared this device with the Clark electrode in the laboratory and tested its value in both animal and clinical studies of hypovolemic shock. The results of these several studies demonstrated that: (1) the new oximeter tracked a rapid fall or rapid rise of oxygen tension between room air (150 mm Hg) and 0 mm Hg ( a glucose oxidase/catalase solution) as well as the Clark electrode without encountering its technical problems; (2) with an acute hemorrhage to 20% of base line, the PsgO2 was found to decline rapidly in parallel with the decline of mean arterial pressure (MAP). Although the MAP rapidly returned to normal after immediate complete return of all shed blood, the PsgO2 did not reach normal levels for at least 2 hours, suggesting persistent peripheral vasoconstriction. (3) Studies in progress suggest that between 35 and 78% of trauma patients (n = 18) adequately resuscitated for hypovolemia b customary criteria have a decreased level of PsgO2 for as long as 60 hours after resuscitation for injury. If care is taken to prevent other causes of catecholamine induced vasoconstriction such as pain, fear, cold, and arterial hypoxia, these several results suggest that a certain number of injured patients are inadequately resuscitated despite the return to normal of conventional hemodynamic measurements. The serial analysis of PsgO2 may assist in managing patients and promote better understanding of the responses to injury.

The effect of posture on late postoperative oxygenation

Twelve patients had their arterial oxygen saturation measured pre-operatively and on days 1, 4 and 7 after laparotomy. Measurements were performed in the supine, sitting and standing positions on each day. Arterial oxygen saturation was significantly higher during sitting and standing on days 1 and 4 after operation compared with the supine position (p < 0.05). These results give further evidence for the benefits of patient mobilisation after major surgery.

Prophylaxis against postoperative complications in gastroenterology

Gastrointestinal surgery results in pain, profound endocrine metabolic changes and organ dysfunction, immunosuppression and decreased resistance to infection, fatigue and convalescence. The main pathogenetic mechanism is the surgical stress response, which may be reduced by minimal invasive (laparoscopic) surgical techniques and afferent neural and perhaps humoral mediator blockade. Subsequently, these techniques have been documented as reducing a variety of postoperative morbidity parameters. A unifying concept for control of the postoperative period is presented as a combined effort to enhance preoperative information, stress reduction and sufficient functional pain relief allowing early mobilization and oral nutrition. Preliminary data, in combination with laparoscopic surgery, suggest that this approach improves outcome significantly.

Venous ulcer fibroblasts compared with normal fibroblasts show differences in collagen but not fibronectin production under both normal and hypoxic conditions

Previous immunocytochemical analysis showed that the base of venous ulcers was deficient in fibronectin compared with surrounding "normal" dermis. Here, we investigate whether impaired synthetic ability of ulcer fibroblasts could underlie this observation. Ulcer fibroblasts, established in culture from biopsies of the edge of chronic venous leg ulcers, were compared with normal fibroblasts grown from biopsies of site-and age-matched normal skin for their ability to synthesize matrix molecules. Collagen and fibronectin synthesis were measured following metabolic labeling, as collagenase susceptible counts and counts with gelatin affinity, respectively. More collagen was produced by normal fibroblasts than ulcer fibroblasts, both when the cells were cultured on plastic and in collagen gels. In fibronectin synthesis, however, there was no major difference between the two cell types on either substratum. The hypoxic environment to which ulcer fibroblasts are exposed may have caused the intrinsic differences in collagen synthesis by the two fibroblast types. When we tested the effect of culturing cells under hypoxic conditions, both cell types produced less collagen, especially normal fibroblasts grown in a collagen gel, but there was no effect of hypoxia on fibronectin synthesis. We conclude that venous ulcer edge-derived fibroblasts have an impaired ability to synthesize collagen in vitro, but synthesize fibronectin normally. Therefore, the low level of fibronectin found in venous ulcers is not likely to be due to the inability of ulcer cells to produce it or to the response to hypoxic conditions but may be due to the degradation of synthesized fibronectin by proteases present in these ulcers.

Effects of dynamic exercise on subcutaneous oxygen tension and temperature

Exercise influences blood flow distribution and may thereby influence tissue oxygen. Given that experimental evidence suggests exercise improves wound healing, this study was undertaken to determine the effect of exercise on subcutaneous tissue oxygen tension (PscO2). Subjects performed a treadmill test to maximum oxygen consumption (VO2) while PscO2 and subcutaneous temperature (Tsc) were measured using a tonometer and optode/thermocouple system. There were no significant differences in PscO2 between measurement points. Mean Tsc had increased 4.8% at maximum VO2, and 6.3% as the cool-down period ended and differed significantly across the exercise period. Changes in PscO2 and Tsc were not correlated. Oxygen availability was neither enhanced nor significantly reduced by exercise. However, PscO2 did not increase as expected in relation to increases in Tsc. Further study will determine the purported beneficial effects of exercise and the mechanism by which it may affect wound healing.

Stimulation of glycosaminoglycan synthesis in cultured fibroblasts by hyperbaric oxygen

In this study we examined the effect of hyperbaric oxygen treatment on the synthesis of glycosaminoglycans by fibroblasts isolated from wounds and normal skin. Fibroblast cultures were exposed to seven treatments of intermittent hyperbaric oxygen, and then metabolically labelled with D-[6-(3)H] glucosamine. Hyaluronic acid and proteoglycan synthesis were determined by measuring the radioactivity precipitated with cetylpyridinium chloride before and after digestion with hyaluronidase. Hyperbaric oxygen treatment resulted in an increased synthesis of hyaluronic acid and proteoglycans by fibroblasts from wounds and normal skin. Overall, the average increase in total glycosaminoglycan synthesis after hyperbaric oxygen treatment was 28%, whereas fibroblast proliferation was decreased by 7%. These results suggest that one of the effects of this treatment on a wound may be to increase the ratio of extracellular matrix to cells. Such a change could have important consequences for cellular activities essential for effective wound healing, such as migration of cells into the wound and control of cell function.

Cells, matrix, growth factors, and the surgeon. The biology of scarless fetal wound repair

OBJECTIVE

This review updates the surgeon about the cellular, matrix, and growth factor components of scarless fetal wound repair.

SUMMARY BACKGROUND DATA

Fetal skin wound healing is characterized by the absence of scar tissue formation. This unique repair process is not dependent on the sterile, aqueous intrauterine environment. The differences between fetal and adult skin wound healing appear to reflect processes intrinsic to fetal tissue, such as the unique fetal fibroblasts, a more rapid and ordered deposition and turnover of tissue components, and, particularly, a markedly reduced inflammatory infiltrate and cytokine profile. Scarless fetal wounds are relatively deficient in the inflammatory cytokine, transforming growth factor beta (TGF-beta). In contrast, the fibrosis characteristic of adult wound repair may be associated with TGF-beta excess. Recent experimental studies suggest that specific anti-TGF-beta therapeutic strategies can ameliorate scar formation in adult wound repair and fibrotic diseases. Inhibitors of TGF-beta may be important future drugs to control scar.

CONCLUSIONS

Based on the scarless fetal wound repair model, a number of ways in which the matrix and cellular response of the healing adult wound might be manipulated to reduce scarring are reviewed.

The effects of hyperbaric oxygen on cultured fibroblasts

The effect of hyperbaric oxygen on the proliferative and synthetic responses of fibroblasts derived from wounds and normal skin was examined in this study. Hyperbaric oxygen treatment resulted in a slight decrease in fibroblast proliferation but an increase in the synthesis of extracellular matrix components. Relating these results to the process of wound healing suggests that hyperbaric oxygen therapy would increase the matrix:cell ratio, which could have important consequences for repair processes such as cell migration and regulation of cell activity. There was no apparent difference in the response to hyperbaric oxygen of fibroblasts derived from different sources.

Comparison of Clark electrode and optode for measurement of tissue oxygen tension

Measurement of PsqO2 has proven clinically valuable. The optode is more stable and reliable than the Clark electrode, does not consume oxygen, measures temperature, and is relatively simple to use. The good correlation between values obtained by the Clark electrode and the optode in this study demonstrate that the optode may replace the Clark electrode without loss of prior data.

Indications for surgical treatment of pancreatic cancer

The best chance for cure of pancreatic cancer is surgical resection. This is also possible in case of adjacent organ involvement of, for example, duodenum, portal vein, or colon. Pancreatic tumours may develop to a large size without developing metastases. Irresectable tumours without distant metastases can successfully be treated with radiotherapy and 5-fluorouracil and, in some cases, be resected during a second-look operation. Thus there is no contraindication for laparotomy in case of large size. Preoperatively estimated size of the tumour is not of prognostic value for resection. Altogether, laparotomy is contraindicated only in case of distant metastases and high operative risk.