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

Transcriptional Activation of the Human Leptin Gene in Response to Hypoxia

In addition to having a major role in energy homeostasis, leptin is emerging as a pleiotropic cytokine with multiple physiological effector functions. The recently discovered proangiogenic activity of leptin suggested the hypothesis that its production might be regulated by hypoxia, as are other angiogenic factors. To examine this proposal, the expression of leptin protein and mRNA was measured and found to be markedly up-regulated in response to ambient or chemical hypoxia (upon exposure to desferrioxamine or cobalt chloride), an effect that requires intact RNA synthesis, suggesting a transcriptional mechanism. Transient transfection of cultured cells with deletion constructs of the leptin gene promoter linked to a reporter gene revealed a functional hypoxia response element (HRE) located at position -116 within the proximal upstream region. This putative HRE harbors a characteristic 5'-RCGTG-3' core motif, a hallmark of hypoxia-sensitive genes and recognized by the hypoxia-inducible factor 1 (HIF1), which consists of a HIF1alpha/HIFbeta heterodimer. Constructs harboring this -116/HRE supported reporter gene expression in response to hypoxia but not when mutated. Expression of HIF1alpha cDNA in normoxic cells mimicked hypoxia-induced reporter gene expression in cells cotransfected with the wild type leptin -116/HRE construct but not with the mutant. Gel shift assays with a (32)P-labeled leptin promoter -116/HRE probe and nuclear extracts from hypoxia-treated cells indicated binding of the HIF1alpha/beta heterodimer, which was blocked with an excess of unlabeled -116/HRE probe or a HIF1-binding probe from the erythropoietin gene enhancer. Taken together, these observations demonstrate that the leptin gene is actively engaged by hypoxia through a transcriptional pathway commonly utilized by hypoxia-sensitive genes.

Effect of a specialized amino acid mixture on human collagen deposition

OBJECTIVE

To examine the effect of arginine, beta-hydroxy-beta-methylbutyrate (HMB), and glutamine supplementation on wound collagen accumulation in a double-blind, randomized study.

SUMMARY BACKGROUND DATA

Control of wound collagen synthesis has been an elusive goal for clinicians and scientists alike. In many clinical instances, it is desired to increase collagen deposition as a means of enhancing wound strength and integrity. Arginine, a semiessential amino acid, has been shown to increase wound collagen accumulation in rodents and humans. HMB, a metabolite of leucine, regulates muscle proteolysis in animals and humans and increases collagen deposition in rodents.

METHODS

Thirty-five healthy, nonsmoking human volunteers 70 years or older were enrolled and underwent subcutaneous implantation of two small, sterile polytetrafluoroethylene (PTFE) tubes into the deltoid region under strict aseptic techniques. The tubes were 1 mm in diameter and 6 cm in length with pore size of 90 to 120 microm to allow optimal ingrowth of fibroblasts and the deposition of matrix. Eighteen volunteers (mean age 75.4 years; 2 men, 16 women) were randomized to receive daily supplementation of 14 g arginine, 3 g HMB, and 14 g glutamine (total nitrogen 3.59 g) in two divided doses. The control group (n = 17; mean age 75.3 years; 6 men, 11 women) received an isonitrogenous, isocaloric supplementation of nonessential amino acids. Catheters were removed at 7 and 14 days postimplantation and analyzed for hydroxyproline (OHP, nmol/cm catheter, an index of collagen accumulation) and alpha-amino nitrogen (alpha-AN, mmol/cm, an index of total protein deposition).

RESULTS

Supplements were well tolerated, without any reported side effects. Supplementation with the specialized amino acid mixture led to a significant rise in plasma arginine and ornithine levels. The specialized amino acid supplement led to a significant increase in collagen deposition (as reflected by OHP content) in the PTFE tubes without an effect on total protein accumulation.

CONCLUSIONS

Collagen synthesis is significantly enhanced in healthy elderly volunteers by the oral administration of a mixture of arginine, HMB, and glutamine. This provides a safe nutritional means for increasing wound repair in patients.

Oxygen, oxidants, and antioxidants in wound healing: an emerging paradigm

Disrupted vasculature and high energy-demand by regenerating tissue results in wound hypoxia. Wound repair may be facilitated by oxygen therapy. Evidence supporting the mode of action of hyperbaric oxygen in promoting wound healing is sketchy, however. Topical oxygen therapy involves local administration of pure oxygen. The advantages of topical oxygen therapy include low cost, the lack of systemic oxygen toxicity, and possibility of home treatment. While this modality of wound care is of outstanding interest, it clearly lacks the support of mechanism-oriented studies. The search for mechanisms by which oxygen supports wound healing has now taken another step. Respiratory burst-derived oxidants support healing. Oxidants serve as cellular messengers to promote healing. Although this information is of outstanding significance to the practice of oxygen therapy, it remains largely unexplored. The search for "natural remedies" has drawn attention to herbals. Proanthocyanidins or condensed tannins are a group of biologically active polyphenolic bioflavonoids that are synthesized by many plants. Proanthocyanidins and other tannins facilitate wound healing. A combination of grape seed proanthocyanidin extract and resveratrol facilitates inducible VEGF expression, a key element supporting wound angiogenesis. Strategies to manipulate the redox environment in the wound are likely to be of outstanding significance in wound healing.

Local instillation of Staphylococcus aureus peptidoglycan at operation prevents wound healing impairment after trauma

BACKGROUND

Considerable experimental evidence and limited clinical evidence indicate that wound healing is impaired after trauma. Because Staphylococcus aureus peptidoglycan (SaPG) accelerates healing in normal rats and prevents wound healing impairment induced by glucocorticoids, cyclophosphamide, and streptozotocin-diabetes, we hypothesized that SaPG would prevent the impaired wound healing after trauma.

METHODS

In each of two experiments, 18 Sprague-Dawley male rats were divided into two groups, nine rats each, paired by weight; one group received unilateral comminuted femoral fracture and wounding (two dorsal skin incisions and six subcutaneous polyvinyl alcohol [PVA] sponges), and the other group was only wounded. The incision and PVA sponges on one side were inoculated at operation with saline (200 microL/incision, 50 microL/sponge) and on the other side with SaPG in saline (860 microg of SaPG per centimeter of incision, 0.5 mg of SaPG per sponge). Rats ate chow and drank tap water ad libitum and were killed 7 days postoperatively.

RESULTS

In both experiments, the wound breaking strength (WBS) of saline-inoculated incisions was significantly lower in rats with femoral fracture; histologically, reparative granulation tissue was looser and less prominent. WBS of SaPG-inoculated incisions in rats with and without femoral fracture was significantly higher than that of saline-inoculated incisions and, histologically, reparative tissue was more prevalent, more closely packed, and more mature. WBS of SaPG-inoculated incisions in rats with femoral fracture was similar to that of saline-inoculated incisions in rats without femoral fracture. Reparative tissue hydroxyproline and histologic findings of saline-inoculated PVA sponge reparative tissue were similar in all rats, as were the increases induced by SaPG inoculation.

CONCLUSION

Wound breaking strength and histologic findings of skin incisions (impaired in rats with unilateral femoral fracture) are more sensitive to the adverse effects of trauma than accumulation of PVA sponge reparative tissue. A single inoculation of SaPG at operation increased wound incision healing in rats both without and with femoral fracture and notably prevented the impaired healing in rats with femoral fracture.

Effects of profound hemodilution on small-intestinal wound healing in rabbits

BACKGROUND

Wound healing is influenced by tissue oxygen tension and blood perfusion, but not by moderate anemia or hemodilution. The effect of perioperative profound hemodilution on small-intestinal wound healing remains unclear.

METHODS

We performed jejunectomy followed by end-to-end anastomosis in rabbits subjected to a variety of perioperative hemodilutions: HD((HES)), hemodiluted with hydroxyethylstarch; HD((P+HES)), hemodiluted with autologous plasma and hydroxyethylstarch; HD((HES))/R, hemodiluted with hydroxyethylstarch and retransfused afterward. Intraoperative hemoglobin levels were 5 g 100 ml(-1). On Postoperative Day 5, the tensile strength (TS) of the anastomosis was measured and histological specimen was obtained. The time courses of hemoglobin, serum albumin (Alb), plasma fibrinogen (Fbg), and plasma activity of factor XIII (F XIII) were measured.

RESULTS

TS in HD((HES))/R (236.0 +/- 52.2 gf) was similar to that in control (266.5 +/- 41.6 gf); however, TS in HD((HES)) (179.8 +/- 17.9 gf) and HD((P+HES)) (165.5 +/- 14.7 gf) decreased significantly. The histological findings in HD((HES))/R were similar to those of control, whereas they demonstrated a delayed healing process in HD((HES)) and HD((P+HES)). Hemoglobin levels were still lower on Postoperative Day 5 in HD((HES)) and HD((P+HES)), but increased to 10.0 g 100 ml(-1) after retransfusion in HD((HES))/R. Hemodilution caused significant decreases in Alb, Fbg, and F XIII, but the values after retransfusion in HD((HES))/R were similar to postoperative values in HD((P+HES)).

CONCLUSION

Intraoperative profound hemodilution does not interfere with small-intestinal wound healing as long as postoperative hemoglobin levels were maintained above 10 g 100 ml(-1). Postoperative levels of other plasma constituents may not influence wound healing.

Increased collagen deposition in an uncomplicated surgical wound compared to a minimal subcutaneous test wound

Little information is currently available concerning the relationship between results obtained in humans from surgical test wounds and results from wound models. Therefore, to evaluate human wound healing parameters, tubings of expanded polytetrafluoroethylene were implanted in a subcutaneous test wound in the arm of 47 volunteers and 20 patients undergoing hernia repair. The surgical patients also had implants left in the surgical wound cavity. After 10 days the deposition of collagen in the tubings as expressed by hydroxyproline content was 30% higher in the surgical wound than in the test wound, p < 0.05. The amount of collagen deposited in the tubing within the surgical wound did not correlate with measurements in the test wound, whereas a significant correlation of proline levels was found between the two sites, p < 0.05. Deposition of proline and total protein in the model was equivalent. In both wound types age negatively correlated with levels of protein, but not collagen. The variability of the results was 40% lower in the subcutaneous test wound than in the surgical wound. There was no significant difference in hydroxyproline deposition between the volunteers and the patients undergoing hernia repair. In patients undergoing minor surgery without signs of compromised healing the expanded polytetrafluoroethylene test wound in the arm reflects the deposition of non-collagenous protein, but not collagen, within the surgical wound.

Modelling of hypoxaemia after gynaecological laparotomy

BACKGROUND

Late postoperative arterial hypoxaemia is common after major surgery, and may contribute to cardiovascular, cerebral or wound complications. This study investigates the time course of hypoxaemia following gynaecological laparotomy, and estimates parameters of mathematical models of pulmonary gas exchange to describe hypoxaemia.

METHODS

Twelve patients were studied on four occasions; preoperatively, 2, 8 and 48 h after surgery. On each occasion inspired oxygen fraction (FIO2) was varied, changing end-expired oxygen fraction (FEO2) to achieve arterial oxygen saturations (SaO2) ranging from 90% to 100%. Measurements of ventilation and blood gases were taken. Oxygenation was characterized plotting FEO2 against SaO2. The shape and position of the FEO2/SaO2 curve was described using two mathematical models including parameters describing gas exchange: either shunt and resistance to oxygen diffusion (Rdiff); or shunt and asymmetry of ventilation-perfusion (fA2).

RESULTS

Two hours after surgery SaO2 was reduced from 97.5%+/-1.2% (mean+/-SD) to 93.8%+/-2.7% (mean+/-SD) (P<0.001). Values of shunt, Rdiff and fA2 were significantly changed at 2 and 8 h postoperatively. Forty-eight hours postoperatively Rdiff and fA2 were still significantly changed.

CONCLUSION

Oxygenation in 12 patients preoperatively, 2, 8 and 48 h after gynaecological laparotomy is described. Two patients were hypoxaemic (SaO2 <92%) 48 h postoperatively. When two different models of oxygen transport are fitted to patient data, high values of Rdiff or low values of fA2 describe the right shift in the FEO2/SaO2 curve seen in patients with oxygenation problems. These models fit patient data identically, and may be useful in quantifying postoperative hypoxaemia.

Complications of ankle fractures in diabetic patients

Ankle fracture in patients with DM mandates a stepwise protocol to minimize the potential complications of delayed fracture healing, wound complications, and development of Charcot arthropathy. For nondisplaced ankle fracture, a nonoperative approach with increased duration of immobilization seems successful based on experience of the limited series. A displaced ankle fracture in a patient with DM requires a surgical intervention. The authors advocate tight glucose control in both groups to improve the fracture milieu and to ameliorate the potential complications. Appropriate stable fixation with adequate length of immobilization is crucial for successful fracture resolution.

Tissue and wound healing effects of short duration postoperative oxygen therapy

The purpose of this study was to determine the effects of 28% oxygen given in the first 36 hours after surgery on tissue oxygen, collagen deposition, and clinical healing outcomes. Twenty-four subjects having cervical spine surgical procedures participated in a randomized, repeated-measures pilot study of tissue and healing effects of postoperative supplemental oxygen. The treatment group (n = 13) received 28% oxygen for the first 36 postoperative hours, whereas the control group (n = 11) was maintained on room air. Subcutaneous tissue oxygen and temperature were measured at intervals up to 36 hours postsurgery. Wound healing was evaluated by hydroxyproline content in a subcutaneous polytetrafluoroethylene tube removed on the 7th postoperative day. Clinical outcomes were evaluated for the 30 days post-hospital discharge. Subjects in the treatment group had significantly higher tissue oxygen tension overall, and at postoperative hours 1, 2, 18, and 36, with mean values 10 to 20 mm Hg higher than control subjects. Significant differences were not found in hydroxyproline levels or clinical wound outcome measures. Low level, short duration, supplemental oxygen increased and sustained wound tissue oxygen and was well tolerated by subjects. Larger studies of populations at risk for wound complications are needed to investigate variables of dose and duration of oxygen therapy in relation to clinical and cellular wound healing outcomes.

Oxygen sufficiency in the gingiva of smokers and non-smokers with periodontal disease

BACKGROUND

Epidemiological studies have demonstrated deteriorating effects of smoking on periodontal tissue. The aims of this study were to compare oxygen saturation of hemoglobin in the gingiva (GSo2) of smokers and non-smokers and to evaluate the chronic effect of smoking on gingival oxygen sufficiency.

METHODS

GSo2 was determined using tissue reflectance spectrophotometry in 110 papillary gingival sites of 62 smokers and 100 sites of 60 non-smokers.

RESULTS

No significant difference was found in GSo2 between smokers and non-smokers. In the model of ANOVA with covariates, age (P= 0.0048) and probing depth (P= 0.0012) had significant effects on GSo2. No significant effect was found in either smoking status (P= 0.3557) or the modified gingival index (MGI) (P= 0.3824). The interaction effect between smoking status and the MGI was highly significant (P = 0.0003) indicating that the effect of smoking status on the GSo2 should be compared at each level of the MGI score. GSo2 in healthy gingiva was significantly lower in smokers than non-smokers (P = 0.0014), while smokers showed higher GSo2 than non-smokers in moderately inflamed gingiva (P = 0.0356). The GSo2 in inflamed gingiva was significantly decreased compared with healthy gingiva in non-smokers (P = 0.0044), while smokers showed no significant difference between healthy and inflamed gingiva (P= 0.2772 to 0.8665). GSo2 in smokers was consistently and significantly lower than that of healthy gingiva of non-smokers (P = 0.0391 to 0.0004).

CONCLUSIONS

Smokers exhibit possibly lower function of oxygen sufficiency in healthy gingiva and reduced ability to adapt the function in inflamed gingiva than non-smokers. This suggests that smokers have functional impairments in the gingival microcirculation.

Staple vs. subcuticular vicryl skin closure in knee replacement surgery: a spectrophotographic assessment of wound characteristics

Staple closure is a popular method of skin closure for patients undergoing knee replacement surgery. There are no guidelines regarding spacing of staples and some concern exists with regard to wound oxygenation in knees subject to early movement. We compared cutaneous wound characteristics in terms of blood oxygenation and blood content, using two types of skin closure. Staples or 4/0 subcuticular vicryl were used. We found favourable blood perfusion characteristics when using stapled closure. Our results also suggest that optimum wound oxygenation requires staple spacing of 6 mm or more.

Reducing red blood cell transfusion in elective surgical patients: the role of audit and practice guidelines

In 1996, we prospectively audited peri-operative transfusion practice in elective surgical patients over a 3-month period. Two-unit transfusions represented 60% of all transfusions. Haemoglobin was measured infrequently prior to transfusion and the main 'trigger' for transfusion was an estimated blood loss in excess of 500 ml. Transfusion guidelines that required the haemoglobin level to be measured immediately before transfusion were introduced. The audit was repeated in 1998; transfusion 'triggers' and the number of transfusions for the two periods were compared. In the second audit, the total number of transfusions decreased by 43%. The mean estimated blood loss associated with a 2-unit transfusion had increased from 608 (373) ml to 1320 (644) ml (p < 0.01) and the estimated haemoglobin concentration after transfusion had decreased from 12.4 (1.8) g.dl-1 to 9.9 (2.4) g.dl-1 (p < 0.01). These results suggest that transfusion guidelines can have a significant impact on clinical practice.

Lactate elicits vascular endothelial growth factor from macrophages: a possible alternative to hypoxia

Macrophages respond to various stimuli to produce angiogenic factors but few mechanistic details are known. We examined the effects of hypoxia, lactate and nicotinamide on the expression of vascular endothelial growth factor by cultured macrophages. These agents were chosen because they down-regulate polyadenosine diphosphoribose levels. Following exposure, conditioned media were analyzed for vascular endothelial growth factor protein. Nicotinamide adenine dinucleotide, polyadenosine diphosphoribose, and vascular endothelial growth factor mRNA were measured in the cellular fraction. Angiogenic capacity of the conditioned media was tested in rabbit corneas and Matrigel implants. All three agents, hypoxia, lactate and nicotinamide, elicited significantly increased levels of vascular endothelial growth factor mRNA and vascular endothelial growth factor in the conditioned media, and these levels were paralleled by their angiogenic activity. Polyadenosine diphosphoribose in the cellular fraction was correspondingly depressed. Anti-vascular endothelial growth factor antibody inhibited most of the angiogenic response whereas anti-basic fibroblast growth factor antibody had little effect. We propose that redox changes associated with the alteration of cellular nicotinamide adenine dinucleotide and polyadenosine diphosphoribose are involved in lactate-mediated VEGF expression.

A critical assessment of endpoints of shock resuscitation

Modern hemodynamic therapy is not only the recognition and treatment of hypotension but also the avoidance and treatment of shock in its broadest sense. The major issues include the recognition of hypoperfusion of the body as a whole or its individual tissues and organ systems and the determination of the best endpoints for the treatment of shock. Even if all of the commonly used clinical indicators of shock are "normal," shock on a cellular, tissue, or organ basis may still be present. Whether "organ-specific" assessments, such as gastric tonometry or tissue oxygen tension measurement, are the ultimate answer to this problem remains to be seen. The determination of adequate intravascular volume (preload) continues to present major difficulties in the care of critically ill or injured patients. Although PCWP is frequently helpful, it is not a gold standard. A bedside ultrasonic technique, such as esophageal Doppler sonography, may replace the Swan-Ganz catheter technique in many patients.

Supplemental oxygen improves resolution of injury-induced pneumothorax

BACKGROUND/PURPOSE

Traditionally, supplemental oxygen is administered to patients with asymptomatic pneumothorax to accelerate spontaneous resolution. However, this practice is based on models that did not include injury to the visceral pleura and ongoing pleural air leak. This study evaluated the effects of increased inspired oxygen concentration on pneumothorax resolution in a visceral pleural injury model.

METHODS

A total of 27 New Zealand white rabbits were divided randomly into 3 groups: room air (RA), 40% FIO2 (40%), and 60% FIO2 (60%). A complete unilateral pneumothorax was created in each animal by a thoracoscopically guided visceral pleural puncture. The animals were then housed in designated oxygen chambers, and observers were blinded to the inspired oxygen concentration. Cross table anteroposterior chest x-rays were obtained preoperatively, postoperatively, and twice a day until the pneumothorax resolved. Time to resolution between the 3 groups was analyzed with 1-way analysis of variance (ANOVA).

RESULTS

Twenty of 27 (74%) of the animals completed the study successfully. Mean time to resolution in the RA group (n = 7; 111.2 +/- 30.8 hours) was longer than in the 40% group (n = 6; 71.8 +/- 22.3 hours) and the 60% group (n = 7; 39.4 +/- 14.2 hours). The time to resolution also was longer in the 40% group than in the 60% group. Seven rabbits died before completion of the study of tension pneumothorax (3 of 7) or anesthetic complications (4 of 7).

CONCLUSIONS

Supplemental oxygen improves resolution of injury-induced pneumothorax. The tradition of administering supplemental oxygen to patients with asymptomatic pneumothorax should be continued even if there is ongoing pleural air leak.

Efeitos da nicotina na cicatrização intestinal em ratos

É grande o número de pessoas que inalam nicotina diariamente através do hábito de fumar e eventualmente têm que ser submetidos a intervenção cirúrgica no aparelho digestivo. Sendo a nicotina um agente que tem sido implicado no retardo da cicatrização das feridas, foi realizado estudo experimental em ratos com o objetivo de testar o seu efeito na evolução histológica da cicatrização de anastomoses intestinais. Foram utilizados 17 ratos Wistar com média de peso 275±14g, divididos aleatoriamente em grupo I (n=9) e grupo II (n=8), anestesiados com éter sulfúrico e operados com técnica asséptica. A nicotina foi administrada por via subcutânea na dose de 5mg/kg em dias alternados, durante 17 dias nos ratos do grupo I e foi usado placebo no grupo II. Após sete dias de uso da nicotina e do placebo, foi feita secção transversal do jejuno a 5 cm do duodeno e anastomose com polipropileno 6-0. No décimo dia os ratos foram mortos com superdose de éter sulfúrico e foi feita biópsia da anastomose. Após processamento dos cortes histológicos e coloração pela hematoxilina-eosina, os dados foram quantificados por escores. A análise histológica revelou que o grupo I atingiu o escore 135 (média 15±4,41) e o grupo II, 218 (média 27,25±4,89). De acordo com o teste t, a diferença mostrou-se significativa (p<0,05). Os dados permitem concluir que a nicotina, quando administrada por via subcutânea em ratos, contribui para prejudicar a cicatrização de anastomoses intestinais.

Smoking and alcohol abuse are major risk factors for anastomotic leakage in colorectal surgery

BACKGROUND

Several studies have examined the association between anastomotic leakage and intraoperative risk factors in colorectal surgery, but only a few have taken patients' lifestyle into account. The aim of this study was to assess the association between anastomotic leakage and lifestyle factors such as smoking habits and alcohol consumption.

METHODS

Between January 1993 and October 1996, 333 unselected consecutive patients in one surgical department underwent colonic or rectal resection with anastomosis. The association between clinical anastomotic leakage and 24 variables related to patient history, diagnosis and surgery was assessed retrospectively and analysed by logistic regression.

RESULTS

The rate of clinical anastomotic leakage was 15.9 per cent (53 of 333 patients). Multiple regression analysis showed that smokers, compared with non-smokers, had an increased risk of anastomotic leakage (relative risk (RR) 3.18 (95 per cent confidence interval (c. i.) 1.44-7.00)), as did alcohol abusers compared with abstainers (RR 7.18 (95 per cent c.i. 1.20-43.01)). In the analysis, well known risk factors for anastomotic leakage such as site of anastomosis, age and stage of training of the surgeon were taken into account.

CONCLUSION

Smoking and alcohol abuse are important predictive factors for anastomotic leakage after colonic and rectal resection.

Fibroblast response to hypoxia: the relationship between angiogenesis and matrix regulation

A number of studies have demonstrated the critical role of angiogenesis for successful wound repair in the surgical patient. Vascular disruption from tissue injury due to trauma or surgery leads to a hypoxic zone in the healing wound. In this dynamic process, angiogenesis is vital for the delivery of oxygen, nutrients, and growth factors necessary to initiate the synthetic processes of wound healing. Fibroblasts, invading the wound early in the healing process, are involved in extracellular matrix (ECM) deposition as well as wound contraction. However, the exact mechanisms by which important genes are regulated remain unknown. In order to examine these processes, we studied the effects of hypoxia on fibroblasts for the expression of VEGF, type IalphaI collagen, and matrix-metalloproteinase-3, three genes essential for the regulation of angiogenesis, ECM deposition, and ECM degradation in wound healing. Primary cell cultures of normal human dermal fibroblasts (NHDFs) were placed in hypoxia for varying periods of time. Northern blot hybridization was performed with [alpha32P]dCTP-labeled cDNA probes for VEGF, type IalphaI collagen, and MMP-3. The results demonstrated a time-dependent VEGF mRNA upregulation (470% of baseline) under hypoxia. Type IalphaI collagen increased (170% of baseline) at 24 h, but was then abruptly downregulated to 3.8% of baseline at 48 h. MMP-3 was incrementally downregulated to 2.2% of baseline at 48 h. These experiments focused on the effect of hypoxia on genes thought to play a role in wound repair. VEGF upregulation in the hypoxic microenvironment of the early wound may serve to stimulate angiogenesis. Type IalphaI collagen, though upregulated early on, was abruptly downregulated at 48 h. This downregulation may reflect the in vivo requirement for angiogenesis to deliver oxygen for successful hydroxylation and collagen synthesis in the wound. MMP-3, also downregulated at 48 h, may also implicate the need for angiogenesis. These data support the theory that hypoxia-driven angiogenesis is critical for ECM formation and remodeling in successful soft tissue repair. Furthermore, they may represent the role of hypoxia as an important regulator to efficiently balance these complex processes in the healing wound.

Hemorrhage decreases macrophage inflammatory protein 2 and interleukin-6 release: a possible mechanism for increased wound infection

OBJECTIVE

To determine whether alteration in wound exudate cell immune function occurs after trauma-hemorrhage.

BACKGROUND

Although clinical and experimental studies indicate that the rate of wound infection is increased after trauma and hemorrhagic shock, the underlying mechanism for this increased susceptibility remains unknown.

METHODS

Male C3H/HeN mice were subjected to a midline laparotomy and polyvinyl alcohol sponges were implanted subcutaneously in the abdominal wound before hemorrhage (35+/-5 mm Hg for 90 minutes and resuscitation) or sham operation. The wound exudate cells from the sponges were harvested on the first, third, and fifth postoperative day and cultured for 24 hours in the presence of lipopolysaccharide (10 microg/ml) or heat-killed Staphylococcus aureus. Interleukin (IL)-1beta, IL-6, monocyte chemotactic protein 1, macrophage inflammatory protein 2, and nitrite levels were determined in the supernatants. The distribution of macrophages and polymorphonuclear leukocytes was assessed in the sponge with and without in vivo injection of S. aureus. The phagocytic activity of isolated wound exudate cells was determined using fluorescent S. aureus.

RESULTS

The composition of exudate cells was unaltered by hemorrhagic shock; however, in vivo injection of S. aureus significantly decreased the percentage of macrophages under such conditions. Wound exudate cell phagocytic activity and the release of IL-1beta, IL-6, monocyte chemotactic protein 1, and macrophage inflammatory protein 2 was decreased on the first postoperative day. The release of IL-1beta and IL-6 was also decreased on the third postoperative day in hemorrhaged mice. On the fifth postoperative day, wound exudate cell cytokine production was comparable to that in shams.

CONCLUSIONS

Because most wound infections occur early after severe trauma, these results suggest that the dysfunction of wound exudate cells after hemorrhage might contribute to the increased incidence of wound infections. Therefore, attempts to enhance or restore wound cell immune function might be helpful for decreasing the incidence of wound infections in trauma victims.

Modifying perfusion, nutrition, and stress to promote wound healing in patients with acute wounds

Tissue injury is common among patients in acute care settings. The subsequent response to injury, wound healing, follows an intricate but well-defined sequence that, under normal conditions, proceeds to satisfactory repair. However, because of the complexity of the healing response, several factors can intervene to impair normal healing. As a better understanding of how diverse factors influence healing is gained, the use of interventions that modulate these factors becomes possible and potentially beneficial. This article reviews knowledge of perfusion, nutrition, and stress as they relate to healing in patients experiencing acute wounds. Therapeutic implications based on current research are discussed.

Biliary complications in pediatric living related liver transplantation

BACKGROUND

The goal of this study was to evaluate cause and outcome of biliary complications occurring after pediatric living related liver transplantation (LRLT).

METHODS

A database of 205 pediatric patients (71 male and 134 female) undergoing 208 LRLT from June 1990 to April 1996 was reviewed.

RESULTS

The overall incidence of bile duct complications was 13.9% (29 patients). There were 19 bile leaks, 7 anastomotic strictures, 8 intrahepatic biliary complications, and the bile duct was ligated inadvertently in 2 cases. Logistic regression analysis revealed hepatic artery thrombosis, ABO incompatible transplantation, intrapulmonary shunting in recipients, mode of artery reconstruction, and cytomegalovirus infection were all significant risk factors for biliary complications.

CONCLUSIONS

Avoidance of ABO incompatible transplantation where possible, routine use of microvascular techniques for hepatic artery reconstruction to minimize the risk of artery thrombosis, earlier transplantation for patients with intrapulmonary shunt, and prophylaxis against cytomegalovirus infection should all reduce the rate of biliary complications after LRLT in pediatric recipients.

Postoperative oxygen therapy

Much has been published in the medical literature concerning adverse events relating to the surgical patient. Among the notable disorders requiring the expertise of the postanesthesia care unit nurse are the diagnosis and management of respiratory dysfunction acutely attributable to the effects of surgery and anesthesia. Inhalational and/or intravenous anesthetic agents contribute to pathophysiological alterations that lend to the development of hypoxemia in the postoperative period. When patients present with preexisting respiratory disease, their care is frequently more complex and challenging. This review session will address the oxygenation component of respiration and the perioperative influences that alter it as well as treatment considerations for normalizing oxygenation.

The effects of hyperbaric oxygen on normal and ischemic colon anastomoses

BACKGROUND

Leakage from colonic anastomoses is a major complication causing increased mortality and morbidity, and ischemia is a well-known cause of this event. Inadequate tissue oxygenation could be reversed by using hyperbaric oxygen. This study was designed to investigate the effects of hyperbaric oxygen on the healing of ischemic and normal colon anastomoses in the rat model.

METHODS

Standardized left colon resection 3 cm above the peritoneal reflection and colonic anastomosis were performed in 40 Wistar rats divided into four groups. The control group (I) received no further treatment. To mimic ischemia, 2 cm mesocolon was ligated on either site of the anastomosis in group II and IV rats. Hyperbaric oxygen therapy was started immediately after surgery in group III and IV rats (therapeutic groups). All animals were sacrificed on the fourth postoperative day. After careful relaparotomy, in situ bursting pressure was measured. The hydroxyproline contents of the anastomotic segments in equal length were determined.

RESULTS

The hydroxyproline assay revealed that rats in group II with ischemic colonic anastomosis have significantly lower levels (P <0.05). The highest levels are in the group III rats with normal colonic anastomosis treated by hyperbaric oxygen (P <0.05). There was no significant difference in hydroxyproline levels between group II and group IV animals (P >0.05). Group III animals had significantly higher bursting pressures than any other group (P <0.05). Group II rats had lowest bursting pressures (P <0.05). Group IV animals had significantly higher levels than group II (P <0.05). Mean bursting pressure values both in groups III and IV and hydroxyproline levels in group III were significantly increased by hyperbaric oxygen therapy (P <0.05).

CONCLUSIONS

Ischemia impairs anastomotic healing. Hyperbaric oxygen increases anastomotic healing of both normal and ischemic colonic anastomosis and reverses ischemic damage. This study demonstrated that hyperbaric oxygen improves anastomotic healing.

Nutrition, tissue oxygenation, and healing of venous leg ulcers

The purpose of the prospective study described in this article was to explore nutrition, tissue oxygenation, and healing in venous ulcer patients. Nutritional risk, anthropometric measures, biochemical indices, two 3-day dietary records, and transcutaneous tissue oxygen levels were obtained. Wound surface area was evaluated 2 times, 4 weeks apart. A convenience sample of 25 English-speaking persons with 1 or more venous ulcers participated (mean age 59.8 years, 60% men, 48% white). Moderate or high nutritional risk existed in 84% of the persons in the sample. Based on body mass index, more than 50% of the persons in the sample were obese. Nonetheless, 17 of 25 persons in the sample had 1 or more abnormal biochemical nutritional indices. In addition, caloric intake (17 of 20), protein intake (15 of 20), and zinc intake (17 of 20) were inadequate to meet the needs for healing. No statistically significant relationships were found between biochemical nutritional indices, tissue oxygenation, and healing. The women in the sample were more likely to heal than were the men (P < 0.05). This study begins to document the problems of overnutrition and undernutrition in the venous ulcer population. Future studies need to explore the effects of obesity and inadequate intake on the healing of venous ulcers. Additional examination of the differences between men and women also is warranted to identify predictors of venous ulcer healing.

Impediments to wound healing

Chronic wounds will often heal in a short period of time if factors that inhibit wound healing are identified and managed. Recombinant growth factor therapy may provide an added stimulus to healing in certain types of chronic wounds. However, there remains no substitute for a physiologic environment conducive to tissue repair and regeneration, without which the efficacy of growth factor therapy is questionable. Some of the most commonly encountered and clinically significant impediments to wound healing include wound hypoxia, infection, presence of debris and necrotic tissue, use of anti-inflammatory medications, a diet deficient in vitamins or minerals, or general nutritional deficiencies, tumors, environmental factors, and metabolic disorders, such as diabetes mellitus. Treatment of chronic wounds should be directed against the main etiologic factors responsible for the wound. Moreover, factors that may impede healing must be identified and, if possible, corrected, for healing to occur.

Tissue repair of the epidermis and dermis

Wounds of the skin heal in a predictable fashion and at a fairly constant rate if impediments to healing can be avoided. For the skin wound of the hand, the therapist and surgeon face paradoxic demands to balance optimal immobilization for wound healing with optimal motion for function. As long as the wound remains stable, therapy can begin very early in the postoperative period without interruption of the wound-healing process.

Retrospective evaluation of postoperative intralesional steroid injections on wound healing

Steroids have been implicated as an etiology in delayed wound healing. Although there is much documentation in the literature that steroids delay wound healing, most studies are in vitro or use high systemic doses. No studies have used a one-time, postoperative, intralesional steroid injection and evaluated wound healing. This study retrospectively reviewed 73 patients with 115 foot and ankle surgeries over 12 years. Seventy-two patients had steroid injections and 43 did not. The average healing time for the steroid group was 17.1 +/- 10.5 days, and for the non-steroid group 17.3 +/- 8.75 days. There were two infections in the non-steroid group, and one infection in the steroid group. There were five dehiscences in each group. The patients were further subdivided into groups based on age, gender, number of procedures, type of surgery, health status, steroid type, and steroid dose. The healing time increased in patients > 60 years old, and in immunocompromised patients. The patients who had more complex surgery had increased healing time. The males had a longer healing time than the females. Overall, there was not a statistically significant difference between the steroid groups and the non-steroid group. Therefore, one-time postoperative intralesional steroid injections were not found to delay wound healing.

Local radiant heating increases subcutaneous oxygen tension

BACKGROUND

We evaluated a novel bandage that incorporates a thermostatically controlled radiant heater. We first determined optimal bandage temperature, based on increases in subcutaneous oxygen tension, a measure correlating well with resistance to infection and wound strength. We then tested the hypothesis that prolonged radiant heating would increase collagen deposition in experimental thigh wounds.

METHODS

The experimental bandages were positioned on the anterior thigh of 8 volunteers, and heated for 2 hours at 38 degrees C, 42 degrees C, or 46 degrees C, in a random order. Subcutaneous oxygen tension under the bandage was recorded from an electrode positioned within a subcutaneous tonometer. We studied 10 volunteers in the second protocol. For 1 week, the experimental bandage was continuously applied to one thigh, and heated to 38 degrees C using a 2-hour on/off cycle. On the alternate week, a standard gauze bandage was applied to the contralateral thigh. Treatment order was randomly assigned. Wound collagen deposition under each bandage was evaluated with subcutaneous polytetrafluoroethylene tubes, which were removed and assayed for hydroxyproline on the eighth day. Data are presented as means +/- SDs.

RESULTS

Skin temperature during heating ranged from 36 degrees C to 37.5 degrees C. Oxygen tension increased approximately 50% during heating, but the increase was comparable at the three tested temperatures. Even after heating was discontinued, subcutaneous oxygen tension remained elevated for the remaining 3 study hours. Collagen deposition after 1 week of active heating was 3.4 +/- 1.0 microg/ cm. After 1 week of control treatment, collagen deposition was 3.2 +/- 1.1 microg/cm (P = not significant).

CONCLUSIONS

Our data suggest that radiant heating at 38 degrees C significantly increases subcutaneous oxygen tension, and presumably resistance to infection. However, prolonged heating at this temperature does not increase wound collagen deposition.

Effects of shear stress on wound-healing angiogenesis in the rabbit ear chamber

Recent studies indicate that wall shear stress plays a significant role in the physiological adaptation of the vascular system. This study focused on the effect of sustained wall shear stress on wound-healing angiogenesis by exploring the morphologic and hemodynamic changes in developing microvessels in vivo through the tissue repair process. Rabbits were treated with the alpha 1 blocker prazosin (50 mg/L in water) orally from Day 0 to Day 23 after implantation of ear chambers to increase peripheral blood flow. The microvasculature in the chamber was recorded from Day 7 to Day 23 by using an intravital videomicroscope. The relative area of the chamber covered by vascularized tissue (%), the rate of ingrowth (mm2/day), the total vascular area (mm2), and the wall shear stress level (dyne/cm2) in venules (diameter in 20-40 microns) were quantified using a computerized image analysis system. The relative area increased significantly in the prazosin-treated animals from Days 7 to 19. The chamber of the treated group was completely covered with vascularized tissue earlier than that of the control group. The final total vascular area was larger by 21% in the treated group. The time course of shear stress in the treated group showed an initial elevation (1.44 times increase vs the control) followed by a gradual decrease toward the control level. These findings suggest that wound-healing angiogenesis may be partly involved in the adaptive response of microvasculature to shear stress.

The skin blood flow response in wound healing

Although vasodilation is conventionally held to be the predominant microvascular response to a wound, there has been no previous attempt to actually quantitate skin blood flow within and in the neighborhood of wounds. In particular, there has been no differentiation between sites with primarily nutritive (NUTR) blood flow and those with considerable arteriovenous (AV) perfusion. We used our previously described model of cutaneous blood flow in the rat to study the blood flow response to wounding. We measured skin blood flow at the centers and at the undisturbed perimeters of wounds placed at the back, a NUTR site, and at the paw, an AV site, in 11 Wistar Kyoto rats. Measurements were performed at baseline, and then at 3 hr, 24 hr, 72 hr, and 7 days postwounding. At 3 hr, flow at the center of the back wound had increased to 11.3 +/- 1.4 ml/min/100 g from a baseline of 2.1 +/- 0.1 ml/min/100 g and remained elevated at 7 days (8.3 ml/min/100 g). Flow at the perimeter of the back wound rose as well, but not as high as at wound center, to twice the baseline level (4.1 ml/min/ 100 g at Day 7). Flow values at control sites on the back did not increase from baseline. Flow at the center of the paw wound rose from 7.2 +/- 0.5 ml/min/100 g at baseline to 15.6 +/- 4.3 ml/min/100 g at Day 3 but then fell back to 6.9 +/- 0.9 ml/min/100 g at Day 7. There was only a very small increase in the basal temperature wound response at the paw perimeter. Blood flow at all wound sites showed a response to heat. At the back, heating to 44 degrees stimulated an 80% increase in blood flow at baseline. This degree of increase was maintained at both the center and the perimeter of the back wound. In contrast, although there was also a thermal response at the paw wound center, it was of much lower magnitude than the nonwounded baseline response. As a result, the heat-stimulated flow value actually fell over the 7 days to approximately half of the baseline level. At the paw wound periphery, there was an initial fall in the heat stimulated response, but it then recovered to the baseline level and remained stable over the 7 days. Thus, the skin blood flow response seen at the paw wound challenges the conventional concept of vasodilation as the expected wound blood flow response. The mechanisms of blood flow response in the healing wound may be more complex than the simple inflammatory vasodilation conventionally postulated.

Ageing and wounds. Part 1: Foetal and postnatal healing

The first in a two-part series of reviews outlines the physiology of wound healing in the normal adult and discusses how it differs from that of the foetus.

Effects of hypoxemia on early postoperative course of liver transplantation in pediatric patients with intrapulmonary shunting

Nine pediatric patients (mean age, 10 years) with biliary atresia, who had hypoxemia related to intrapulmonary shunting, underwent living related liver transplantation. The effects of hypoxemia during the early postoperative period after liver transplantation on cardiopulmonary and renal function, as well as on transplanted liver, were analyzed. Based on the degree of shunt ratio calculated by technetium-99m macroaggregated albumin scintigraphy, the nine patients were included in the moderate group (shunt ratio under 40%, n=4) or the severe group (shunt ratio over 40%, n=5). Partial pressure of arterial oxygen was maintained at normal range in the moderate group, while that in the severe group persistently had very low values (<50 mmHg), in spite of a high degree of oxygen supply. However, all patients in the severe group maintained stable cardiopulmonary vital signs, including systemic blood pressure, heart rate, respiratory rate, and cardiac index. They also demonstrated stable renal function. None of the patients died of cardiopulmonary or renal insufficiency after transplantation, but three patients died of portal vein thrombosis, sepsis, and intracranial hemorrhage (one each). The minimal adverse effect of hypoxemia on the transplanted liver was confirmed by a rapid increase of arterial ketone body ratio, low peak values (under 200 IU/L) of aspartate aminotransferase, and a steady decrease of serum total bilirubin. Four patients encountered surgical complications, including two bile leaks from the cut liver surface, two leaks from bilioenteric anastomosis, and one intestinal perforation. Six patients suffered from bacterial infections, including four wound infections, three right subphrenic abscesses, one cholangitis, and two systemic sepses. All patients in the moderate group recovered from hypoxemia, but four of five patients in the severe group have not recovered during the follow-up period between 4 and 9 months. It was concluded that the adverse effects of hypoxemia on cardiopulmonary and renal function and transplanted liver were minimal, so that patients with severe hypoxemia could tolerate the stress of liver transplantation without special management. However, the high incidence of surgical complication and infection suggested the adverse effects of hypoxemia on wound healing and resistance to bacteria infection.

Reduced collagen accumulation after major surgery

The preoperative and postoperative wound-healing capacity of 23 patients undergoing elective major abdominal, thoracic or urological surgery was tested objectively by the subcutaneous accumulation of hydroxyproline and proline in an expanded polytetrafluoroethylene (ePTFE) tube. Before scheduled surgery two ePTFE tubes were implanted for removal after 5 and 10 days. This was repeated for each patient immediately after surgery. After 10 days a higher amount of hydroxyproline was measured before than after operation (median 2.91 (range 0.37-14.45) versus 1.45 (range 0.26-6.94) micrograms/cm, P = 0.01)). This decline was significantly higher in the six patients who had a postoperative infection (median 3.02 (range -0.06 to 6.14) versus 0.36 (range -1.56 to 12.60) micrograms/cm, P = 0.02). This study shows that major surgery is associated with impairment of subcutaneous collagen accumulation in a test wound, suggesting diminished systemic wound-healing capacity in such patients.

Perioperative normothermia to reduce the incidence of surgical-wound infection and shorten hospitalization. Study of Wound Infection and Temperature Group

BACKGROUND

Mild perioperative hypothermia, which is common during major surgery, may promote surgical-wound infection by triggering thermoregulatory vasoconstriction, which decreases subcutaneous oxygen tension. Reduced levels of oxygen in tissue impair oxidative killing by neutrophils and decrease the strength of the healing wound by reducing the deposition of collagen. Hypothermia also directly impairs immune function. We tested the hypothesis that hypothermia both increases susceptibility to surgical-wound infection and lengthens hospitalization.

METHODS

Two hundred patients undergoing colorectal surgery were randomly assigned to routine intraoperative thermal care (the hypothermia group) or additional warming (the normothermia group). The patient's anesthetic care was standardized, and they were all given cefamandole and metronidazole. In a double-blind protocol, their wounds were evaluated daily until discharge from the hospital and in the clinic after two weeks; wounds containing culture-positive pus were considered infected. The patients' surgeons remained unaware of the patients' group assignments.

RESULTS

The mean (+/- SD) final intraoperative core temperature was 34.7 +/- 0.6 degrees C in the hypothermia group and 36.6 +/- 0.5 degrees C in the normothermia group (P < 0.001) Surgical-wound infections were found in 18 of 96 patients assigned to hypothermia (19 percent) but in only 6 of 104 patients assigned to normothermia (6 percent, P = 0.009). The sutures were removed one day later in the patients assigned to hypothermia than in those assigned to normothermia (P = 0.002), and the duration of hospitalization was prolonged by 2.6 days (approximately 20 percent) in hypothermia group (P = 0.01).

CONCLUSIONS

Hypothermia itself may delay healing and predispose patients to wound infections. Maintaining normothermia intraoperatively is likely to decrease the incidence of infectious complications in patients undergoing colorectal resection and to shorten their hospitalizations.