Wound tissue oxygen tension predicts the risk of wound infection in surgical patients

Empiric evidence for a genetic contribution to predisposition to surgical site infection

The genetics of microbial pathogens have been extensively studied, but there has been little work on human genetic susceptibility to surgical site infection (SSI). We analyzed a large genealogical population database to study the familial contribution to SSI. We analyzed 651 individuals with International Classification of Disease, Ninth Revision codes indicating the presence of SSI. Matched hospital controls were randomly selected from the database based on birth year, sex, and birthplace. The average relatedness of all possible pairs of cases and separately of controls (×1000 sets) was compared empirically. The relative risk (RR) for SSI was estimated by comparing the number of observed affected individuals among the relatives of cases to the number of affected individuals observed among relatives of matched hospital controls. The genealogical index of familiality test for patients with SSI showed significant excess relatedness (p < 0.010); this excess was still observed when close relationships were ignored (p =  0.019). The RR for third-degree relatives of cases was significantly elevated (1.62, p = 0.029). The significant excess relatedness and the significantly elevated RR to distant relatives support a genetic predisposition to acquiring SSI.

Safety in the operating theatre--a transition to systems-based care

All surgeons want the best, safest care for their patients, but providing this requires the complex coordination of multiple disciplines to ensure that all elements of care are timely, appropriate, and well organized. Quality-improvement initiatives are beginning to lead to improvements in the quality of care and coordination amongst teams in the operating room. As the population ages and patients present with more complex disease pathology, the demands for efficient systematization will increase. Although evidence suggests that postoperative mortality rates are declining, there is substantial room for improvement. Multiple quality metrics are used as surrogates for safe care, but surgical teams--including surgeons, anaesthetists, and nurses--must think beyond these simple interventions if they are to effectively communicate and coordinate in the face of increasing demands.

Activated lymphocytes as a metabolic model for carcinogenesis

Metabolic reprogramming is a key event in tumorigenesis to support cell growth, and cancer cells frequently become both highly glycolytic and glutamine dependent. Similarly, T lymphocytes (T cells) modify their metabolism after activation by foreign antigens to shift from an energetically efficient oxidative metabolism to a highly glycolytic and glutamine-dependent metabolic program. This metabolic transition enables T cell growth, proliferation, and differentiation. In both activated T cells and cancer cells metabolic reprogramming is achieved by similar mechanisms and offers similar survival and cell growth advantages. Activated T cells thus present a useful model with which to study the development of tumor metabolism. Here, we review the metabolic similarities and distinctions between activated T cells and cancer cells, and discuss both the common signaling pathways and master metabolic regulators that lead to metabolic rewiring. Ultimately, understanding how and why T cells adopt a cancer cell-like metabolic profile may identify new therapeutic strategies to selectively target tumor metabolism or inflammatory immune responses.

Review article: the anesthesiologist's role in the prevention of surgical site infections

PURPOSE

To highlight the role of anesthesiologists in the prophylaxis of surgical site infections (SSIs) and to recognize the central role they play in quality improvement initiatives for the prevention of SSIs.

SOURCE

The medical literature was searched with a focus on three interventions affecting the risk of SSIs: preoperative antibiotic administration, perioperative normothermia, and perioperative hyperoxia. The literature was also searched for examples of initiatives in patient safety and quality improvement that highlight the role of anesthesiologists in preventing SSIs.

PRINCIPAL FINDINGS

The timely administration of preoperative antibiotics and the maintenance of perioperative normothermia have been shown to reduce the risk of SSI significantly. Perioperative hyperoxia in the prevention of SSIs remains controversial but may improve outcomes in specific subsets of the surgical population. Initiatives in quality improvement show the challenges faced by many centres to improve upon these processes of care, but they also highlight the role of anesthesiologists as champions in the multidisciplinary efforts for the prevention of SSIs.

CONCLUSIONS

Anesthesiologists are responsible for many of the processes of care shown to impact the risk for SSIs, and they play an important role in the prevention of SSIs. Their leadership in the multidisciplinary efforts to improve the quality of the surgical patient is of critical importance.

Should perioperative supplemental oxygen be routinely recommended for surgery patients? A Bayesian meta-analysis

OBJECTIVE

The purpose of this study is to use updated data and Bayesian methods to evaluate the effectiveness of hyperoxia to reduce surgical site infections (SSIs) and/or mortality in both colorectal and all surgery patients. Because few trials assessed potential harms of hyperoxia, hazards were not included.

BACKGROUND

Use of hyperoxia to reduce SSIs is controversial. Three recent meta-analyses have had conflicting conclusions.

METHODS

A systematic literature search and review were performed. Traditional fixed-effect and random-effect meta-analyses and Bayesian meta-analysis were performed to evaluate SSIs and mortality.

RESULTS

Traditional meta-analysis yielded a relative risk of an SSI with hyperoxia among all surgery patients of 0.84 [95% confidence interval (CI): 0.73-0.97] and 0.84 (95% CI: 0.61-1.16) for the fixed-effect and random-effect models, respectively. The probabilities of any risk reduction in SSIs among all surgery patients were 77%, 81%, and 83% for skeptical, neutral, and enthusiastic priors. The subset analysis of colorectal surgery patients increased the probabilities to 86%, 89%, and 92%. The probabilities of at least a 10% reduction were 57%, 62%, and 68% for all surgery patients and 71%, 75%, and 80% among the colorectal surgery subset.

CONCLUSIONS

There is a moderately high probability of a benefit to hyperoxia in reducing SSIs in colorectal surgery patients; however, the magnitude of benefit is relatively small and might not exceed treatment hazards. Further studies should focus on generalizability to other patient populations or on treatment hazards and other outcomes.

Changes in tissue oxygenation following caudal epidural blockade in infants and children

BACKGROUND

Adequate tissue oxygenation is required for effective white blood cell function and bactericidal activity. Decreased tissue oxygenation has been shown to be a risk factor for perioperative wound infections. Regional anesthetic techniques result in a functional sympathetic block and may increase tissue oxygenation. The purpose of the current study is to prospectively evaluate changes in tissue oxygenation using a non-invasive near-infrared spectroscopy (NIRS) device following caudal epidural block in infants and children.

METHODS

Following standard anesthetic induction and general anesthesia with an endotracheal tube or laryngeal mask airway, the NIRS sensors were placed on two sites. One sensor was placed at a site affected by the caudal block (lower extremity), and the other sensor was placed on the arm, a site unaffected by the caudal block (upper extremity). The NIRS value was recorded at baseline and then again at 15, 30, and 45 min after the block. The caudal block was performed, after anesthetic induction and NIRS sensor placement, using bupivacaine 0.25% with epinephrine 1 : 200,000 or ropivacaine 0.2% with epinephrine 1 : 200,000 at a dose of 1 ml · kg(-1). The inspired oxygen concentration after induction was held constant at 30%, and anesthesia was maintained with sevoflurane at 1 MAC. No other pharmacologic agents were administered.

RESULTS

Following the caudal epidural block, there was a statistically significant increase in the tissue oxygenation from the affected site. The NIRS value increased from a baseline of 83 ± 4 to 87 ± 3 at 15 min (P = 0.0001 vs baseline), 88 ± 4 at 30 min (P < 0.0001 vs baseline), and 87 ± 4 at 45 min (P < 0.0001 vs baseline). No change was noted on the unaffected site (upper extremity).

CONCLUSION

There was a statistically significant increase in tissue oxygenation as measured by NIRS following caudal anesthesia in infants and children. Although the magnitude of the change was less, this study confirms the results of previous studies in adults showing an increase in tissue oxygenation following regional blockade.

[Improving patient safety in perioperative care for major surgeries]

The Helsinki Declaration was created and signed by the European Board of Anaesthesiology (EBA) and the European Society of Anaesthesiology (ESA). It was initiated in June 2010, and it implies a European consensus on those medical practices which improve patient safety and provide higher quality perioperative care. Authors focus on four elements of this initiative, which can be easily implemented, and provide almost instant benefit: use of preoperative checklist, prevention of perioperative infections, goal-directed fluid therapy and perioperative nutrition. The literature review emphasizes that well organized perioperative care plays the most important role in improving patient safety.

An analysis of risk factors associated with traumatic extremity amputation stump wound infection in a Nigerian setting

PURPOSE

We aimed to determine the risk factors associated with traumatic extremity amputation stump wound infection in our environment.

METHOD

This was a retrospective analysis of databases that included the entire patient population with traumatic extremity amputation seen in Ebonyi State University Teaching Hospital and Federal Medical Centre Abakaliki from January 2001 to December 2011.

RESULT

There were 63 patients studied and stump wound infection was a complication in 38 (60 %) of them. Stump wound infection rate significantly correlated with the form of amputation, i.e., a higher rate in crushing than guillotine (sharp clear-cut) amputation (80.5 vs. 22.7 % p < 0.000); severity, i.e., a higher rate in major than minor amputation (80.6 vs. 33.3 % p < 0.000); and limb involvement, i.e., a higher rate in lower than upper extremity amputation (71.1 vs. 60.7 % p < 0.002). Haematocrit level on admission (p < 0.002), injury to hospital admission interval (p < 0.012) and injury to first surgical debridement / amputation interval (p < 0.02) were all significantly related to incidence of wound infection. Multivariate analysis identified crushing amputation as an independent risk factor (p < 0.009) for traumatic amputation stump wound infection.

CONCLUSION

The only independent predictor of traumatic extremity amputation stump wound infection is a crushing form of amputation; it should be accorded a high priority in interventions aimed at reducing infection rate.

Rational use of oxygen in medical disease and anesthesia

PURPOSE OF REVIEW

Supplemental oxygen is often administered during anesthesia and in critical illness to treat hypoxia, but high oxygen concentrations are also given for a number of other reasons such as prevention of surgical site infection (SSI). The decision to use supplemental oxygen is, however, controversial, because of large heterogeneity in the reported results and emerging reports of side-effects. The aim of this article is to review the recent findings regarding benefits and harms of oxygen therapy in anesthesia and acute medical conditions.

RECENT FINDINGS

Large randomized trials have not found significant reductions in SSI with 80% oxygen during and after abdominal surgery and cesarean section. There is no documented benefit of hyperbaric oxygen treatment for acute ischemic stroke, and there is emerging data to suggest increased mortality with normobaric supplemental oxygen for myocardial infarction without heart failure. Survival and neurologic outcome seem to be adversely affected by hyperoxia in patients with return of spontaneous circulation after cardiac arrest.

SUMMARY

The benefits of supplemental oxygen are not yet confirmed, and new findings suggest that potential side-effects should be considered if the inspired oxygen concentration is increased above what is needed to maintain normal arterial oxygen saturation.

Supplemental oxygen therapy: Important considerations in oral and maxillofacial surgery

The administration of supplemental oxygen is an essential element of appropriate management for a wide range of clinical conditions; crossing different medical and surgical specialities. The present review summarizes the role of supportive oxygen therapy in various clinical conditions encountered in our day-to-day practice in the speciality of oral and maxillofacial surgery; including major trauma, shock, sepsis; perioperative and postoperative considerations and in patients with various other medical comorbidities. Regular and judicious use of oxygen as a drug is thus recommended in our day-to-day practice in oral and maxillofacial surgery to reduce the morbidity and improve the prognosis of patients.

A review of epidural catheter-related infections

Spinal drug delivery is a generally safe and effective therapy for the treatment of both acute and chronic pain. However, it can be occasionally associated with significant complications, including neurologic injury, as a result of bleeding and infection in a confined space. This article focuses on risk factors for developing epidural catheter-related infections as well as strategies to minimize risks. Additionally, the diagnosis and management of epidural catheter-related infections, both superficial and deep, are discussed.

Comparison of tissue oxygen saturation in ovariohysterectomized dogs recovering on room air versus nasal oxygen insufflation

OBJECTIVE

To compare tissue oxygen saturation in ovariohysterectomized dogs recovering postoperatively on room air versus nasal oxygen insufflation.

DESIGN

Prospective clinical study.

SETTING

University teaching hospital.

ANIMALS

Twenty dogs undergoing ovariohysterectomy.

INTERVENTIONS

Dogs were randomized to breathe either room air or 100 mL/kg/min of nasal oxygen insufflation for 2 hours postoperatively. Tissue oxygen saturation (StO(2)) was evaluated at 2 mm and 20 mm lateral to the surgical incision, as well as in the inguinal region using a noninvasive tissue oximeter.

MEASUREMENTS AND MAIN RESULTS

In dogs recovered on nasal oxygen insufflation (n = 10), tissue oxygen saturation was significantly higher--20 mm from the surgical site (88.44 ± 2.50%, P = 0.02) and in the inguinal region (83.56 ± 1.91%, P = 0.032)-- compared to dogs recovered on room air (n = 10, 79.11% ± 2.50 and 77.12% ± 1.91, respectively).

CONCLUSIONS

In ovariohysterectomized dogs, oxygen supplementation for 2 hours postoperatively improves tissue oxygen saturation 20 mm adjacent to the linea alba and in the inguinal region. Oxygen supplementation in postoperative dogs is an inexpensive and easily applicable method to improve tissue oxygen saturation.

The role of perioperative care in reducing rates of methicillin resistant Staphylococcus aureus

Methicillin resistant Staphylococcus aureus (MRSA) is defined as any strain of Staphylococcus aureus resistant to beta-lactam antibiotics, including the penicillins and cephalosporins. Over the past ten years the UK has seen a dramatic increase in MRSA prevalence in healthcare facilities and the community, with an estimated 30-50% of healthy adults thought to be colonised with MRSA. Surgical patients are among those at highest risk. With potential sequelae including septicaemia, septic shock, septic arthritis, osteomyelitis, meningitis, pneumonia or endocarditis, it is vital that all care facilities have up to date evidence-based guidelines to tackle this problem. The purpose of this review is to highlight the current evidence supporting some of the key perioperative measures which may be implemented in preventing MRSA.

Impact of obesity on surgical site infection in colon and rectal surgery

Obesity affects over 30% of the United States population. Over the past 10 years, there has been increased recognition of the prevalence of obesity and its contribution to worse outcomes among medical and surgical patients. In particular, obesity has been validated as a risk factor for surgical site infection (SSI) among patients undergoing major abdominal surgery with some reports demonstrating an increased risk of SSI as high as sixty percent (60%) among obese patients. For patients undergoing elective colon and rectal surgery, a higher incidence of SSI (up to 45%) has been reported in comparison to outcomes of other surgical procedures. Obesity, as well as numerous other variables, have been implicated as a potential source for this increased incidence. Although the pathophysiology of obesity-related SSI has been suggested (decreased wound oxygen tension, impaired tissue antibiotic penetration, altered immune function, etc.), the true effect of obesity has not been clearly described. The purpose of this review is to examine the growing epidemic of obesity and its specific impact on SSI for both general and colorectal surgical patients. The proposed mechanisms for why obesity increases the risk of SSI will be briefly discussed, as well.

Preventing surgical-site infections after colorectal surgery

Surgical-site infection (SSI) is a major contributor to patient mortality rates and health care costs. Due to the high risk of bacterial contamination, colorectal surgery is associated with a particularly high risk of postoperative infection. The surveillance reported here was conducted at Aichi Medical University Hospital on 304 patients who underwent elective colorectal resection--total or partial--from June 2006 to May 2009. To determine risk factors for SSI, multivariate analysis was used. Forty-six (15.1%) patients were diagnosed with SSI. Patients who received cefotiam for prophylaxis showed the highest incidence of SSI (26.6%), and patients who were administered flomoxef showed the lowest incidence (8.1%). Patients who developed SSI were more likely to intraoperative blood loss (308.1 ± 29.8 vs. 153.9 ± 12.2; p < 0.05), longer postoperative antimicrobial administration (5.3 ± 2.2 vs. 4.5 ± 1.5; p < 0.05), and longer operative time (3.3 ± 1.6 vs. 2.7 ± 1.2; p < 0.05). Intraoperative bleeding, antimicrobial choices to cover both anaerobic and aerobic bacteria, and length of antimicrobial administration were independently predictive of SSI development according to multivariate logistic regression analysis. These results suggest that the degree of operative invasion and anaerobic bacteria contribute to SSI following colorectal surgery.

Supplemental oxygen for the prevention of postcesarean infectious morbidity: a randomized controlled trial

OBJECTIVE

The purpose of this study was to investigate whether supplemental oxygen during and for 2 hours after cesarean delivery reduces the incidence of postcesarean infectious morbidity.

STUDY DESIGN

We conducted a randomized, controlled trial from 2008-2010. Women who underwent cesarean delivery were randomly assigned to receive either 2 L of oxygen by nasal cannula during cesarean delivery only (standard care) or 10 L of oxygen by nonrebreather mask (intervention group) during and for 2 hours after cesarean delivery. Women who underwent scheduled or intrapartum cesarean delivery were eligible and were observed for 1 month after the procedure. The primary composite outcome was maternal infectious morbidity, which included endometritis and wound infection.

RESULTS

Five hundred eighty-five women were included in the final analysis. Infectious morbidity occurred in 8.8% of patients in the standard care group and in 12.2% of patients in the supplemental oxygen group. There was no significant difference in the rate of infectious morbidity between the standard care and intervention groups (relative risk, 1.4; 95% confidence interval, 0.9-2.3).

CONCLUSION

Supplemental oxygen does not reduce the rate of postcesarean delivery infectious morbidity, including endometritis and wound infection.

Evaluation of skin graft take following post-burn raw area in normovolaemic anaemia

Background:

Traditional wisdom is that wound healing is directly related to haemoglobin level in the blood; therefore blood transfusion is given in anaemic patients to raise the haemoglobin level for better wound healing.

Methods:

Evaluation of wound healing in the form of split thickness skin graft take was done in 35 normovolaemic anaemic patients (haemoglobin level of < 10 gm/ dl) and compared with control group (patients with haemoglobin level of 10 or > 10 gm/ dl).

Results:

There was no statistically significant difference in mean graft take between the two groups.

Conclusion:

It is not mandatory to keep haemoglobin level at or >10 g/dL or PCV value at or >30% for skin graft take, as mild to moderate anaemia per se does not cause any deleterious effect on wound healing; provided perfusion is maintained by adequate circulatory volume. Prophylactic transfusion to increase the oxygen carrying capacity of the blood for the purpose of wound healing is not indicated in asymptomatic normovolemic anaemic patients (with haemoglobin levels greater than 6g/dL) without significant cardiovascular or pulmonary disease.

Role of oxygen in wound healing: a review of evidence

OBJECTIVE

To review the evidence regarding the influence of oxygen as an intrinsic factor on cutaneous wound healing.

METHOD

A literature search was performed using Ovid and the Cochrane Database with the search terms: 'Wound healing', 'Oxygen', 'Collagen', 'Angiogenesis', 'Inflammation' and 'Surgical Site Infection'. Human and animal studies were included if relevant and examined for methodological quality.

RESULTS

There are no meta-analyses of the use of oxygen in wound healing and only two randomised controlled trials (RCTs). Studies vary in methodological quality. The majority of the data comes from animal models. In total 1568 studies on wound healing and oxygen were found.

CONCLUSION

Oxygen is vital throughout wound healing, especially in the inflammatory and proliferative phases. Research suggests that patient supplementation with oxygen could enhance bacterial killing and angiogenesis, reduce surgical site infection rates and increase wound tensile strength, facilitating improved healing.

CONFLICT OF INTEREST

None.

Haemodynamic goal-directed therapy and postoperative infections: earlier is better. A systematic review and meta-analysis

Introduction

Infectious complications are the main causes of postoperative morbidity. The early timing of their promoting factors is the rationale for perioperative strategies attempting to reduce them. Our aim was to determine the effects of perioperative haemodynamic goal-directed therapy on postoperative infection rates.

Methods

We performed a systematic review and meta-analysis. MEDLINE, EMBASE, The Cochrane Library and the DARE databases were searched up to March 2011. Randomised, controlled trials of major surgery in adult patients managed with perioperative goal-directed therapy or according to routine haemodynamic practice were included. Primary outcome measure was specific type of infection.

Results

Twenty-six randomised, controlled trials with a combined total of 4,188 participants met our inclusion criteria. Perioperative goal-directed therapy significantly reduced surgical site infections (pooled OR 0.58, 95% CI 0.46 to 0.74; P < 0.0001), pneumonia (pooled OR 0.71, 95% CI 0.55 to 0.92; P = 0.009), and urinary tract infections (pooled OR 0.44, 95% CI 0.22 to 0.84; P = 0.02). A significant benefit was found regarding total infectious episodes (OR 0.40, 95% CI 0.28 to 0.58; P < 0.00001).

Conclusions

Flow-directed haemodynamic therapy designed to optimise oxygen delivery protects surgical patients against postoperative hospital-acquired infections and must be strongly encouraged, particularly in the high-risk surgical population.

Correction of Hypoxia, a Critical Element for Wound Bed Preparation Guidelines: TIMEO2 Principle of Wound Bed Preparation

Wound bed preparation is an organized approach to create an optimal environment for wound healing by the use of the most cost-effective therapeutic options. It has become an essential part of wound management and seeks to use the latest findings from molecular and cellular research to maximize the benefits of today's advanced wound care products. The international advisory panel on wound bed preparation met in 2002 to develop a systemic approach to wound management. These principles of this approach are referred to by the mnemonic TIME, which stands for the management of nonviable or deficient tissue (T), infection or inflammation (I), prolonged moisture imbalance (M), and nonadvancing or undermined epidermal edge (E). One critical element of pathophysiology, understanding of the hypoxic nature of the wound and correction of hypoxia as a critical element of wound bed preparation, is not covered. This article proposes to add correction of hypoxia to the TIME principle (TIMEO2 principle) based on the evidence. The evidence that will support the reason and the need for modification of the wound bed preparation protocol is discussed.

Are oral health complaints related to smoking cessation intentions?

OBJECTIVE

Smoking influences oral health in several ways (such as the occurrence of periodontitis, teeth discolouration and oral cancer); therefore, smoking behaviour should be addressed in dental care. Dentists can play a role in primary and secondary prevention of tobacco dependence. They see their patients repeatedly over time. This study investigates whether oral health complaints can be seized as an opportunity to start smoking cessation counselling.

METHODS

A structured patient questionnaire in a sample of 1101 smokers (52.1% women, mean age 40.4 years) in a convenience sample of 87 primary care dental practices. The I-change model was used to describe factors influencing behavioural change. Dependent factors such as intention to quit smoking and related factors (attitude, social support and self-efficacy) were analysed in relation to independent factors such as oral health complaints (gingiva problems, gingiva inflammation, oral cancer and discoloured teeth) using a general linear model (univariate analysis), multinomial logistic regression analysis and multiple linear regression analysis.

RESULTS

A total of 56.3% had discoloured teeth, 27% of the smokers had a problem with their gums and 15.7% had gingiva inflammation. We found no direct relation between oral health complaints and the intention to quit smoking. However, teeth discolouration was positively related to attitudes towards smoking cessation [β, Confidential interval (95%); 1.92 (1.45-2.40 for advantages and -0.86(-1.18 to -0.53) for disadvantages] and negatively to self-efficacy regarding quitting [-2.69 (-3.49 to 1.88)].

CONCLUSIONS

We found no direct relation between oral health complaints and the intention to quit smoking, but oral health complaints and especially teeth discolouration were related to factors influencing the quit intention. Patients with discoloured teeth are more likely to have a positive attitude towards smoking cessation but are uncertain to persist smoking cessation. It is suggested that teeth discolouration can be a good entrance for addressing smoking cessation in daily dental practice.

Hyperoxia may be beneficial

The current practice of mechanical ventilation comprises the use of the least inspiratory O2 fraction associated with an arterial O2 tension of 55 to 80 mm Hg or an arterial hemoglobin O2 saturation of 88% to 95%. Early goal-directed therapy for septic shock, however, attempts to balance O2 delivery and demand by optimizing cardiac function and hemoglobin concentration, without making use of hyperoxia. Clearly, it has been well-established for more than a century that long-term exposure to pure O2 results in pulmonary and, under hyperbaric conditions, central nervous O2 toxicity. Nevertheless, several arguments support the use of ventilation with 100% O2 as a supportive measure during the first 12 to 24 hrs of septic shock. In contrast to patients without lung disease undergoing anesthesia, ventilation with 100% O2 does not worsen intrapulmonary shunt under conditions of hyperinflammation, particularly when low tidal volume-high positive end-expiratory pressure ventilation is used. In healthy volunteers and experimental animals, exposure to hyperoxia may cause pulmonary inflammation, enhanced oxidative stress, and tissue apoptosis. This, however, requires long-term exposure or injurious tidal volumes. In contrast, within the timeframe of a perioperative administration, direct O2 toxicity only plays a negligible role. Pure O2 ventilation induces peripheral vasoconstriction and thus may counteract shock-induced hypotension and reduce vasopressor requirements. Furthermore, in experimental animals, a redistribution of cardiac output toward the kidney and the hepato-splanchnic organs was observed. Hyperoxia not only reverses the anesthesia-related impairment of the host defense but also is an antibiotic. In fact, perioperative hyperoxia significantly reduced wound infections, and this effect was directly related to the tissue O2 tension. Therefore, we advocate mechanical ventilation with 100% O2 during the first 12 to 24 hrs of septic shock. However, controlled clinical trials are mandatory to test the safety and efficacy of this approach.

[Postoperative wound infections. Pathophysiology, risk factors and preventive concepts]

Postoperative wound infections are the third most common type of nosocomial infection in German emergency hospitals after pneumonia and urinary infections. They are associated with increased morbidity and mortality, prolonged hospital stay and increased costs. The most important risk factors include the microbiological state of the skin surrounding the incision, delayed or premature prophylaxis with antibiotics, duration of surgery, emergency surgery, poorly controlled diabetes mellitus, malignant disease, smoking and advanced age. Anesthesiological measures to decrease the incidence of wound infections are maintaining normothermia, strict indications for allogenic blood transfusions and timely prophylaxis with antibiotics. Blood glucose concentrations should be kept in the range of 8.3-10 mmol/l (150-180 mg/dl) as lower values are associated with increased complications. Intraoperative and postoperative hyperoxia with 80% O(2) has not been shown to effectively decrease wound infections. The application of local anesthetics into the surgical wound in clinically relevant doses for postoperative analgesia does not impair wound healing.

Ankle injuries and fractures in the obese patient

Ankle fractures are a common orthopedic injury. Certain ankle injuries have been associated with patient demographics such as obesity and smoking. Obese patients are more prone to severe ankle injuries. Naturally, these injuries affect the lower extremity mobility significantly, which itself is a risk factor for obesity. Although obese patients have increased complications across the board, there are specific techniques that can be used to assure the best possible outcome. The perioperative, surgical, and postoperative considerations as well as the outcomes are discussed in this article.

Supplemental postoperative oxygen and tissue oxygen tension in morbidly obese patients

BACKGROUND

Subcutaneous tissue oxygen tension (PsqO(2)) is a major predictor for wound healing and the occurrence of wound infections. Perioperative subcutaneous wound and tissue oxygen tension is significantly reduced in morbidly obese patients. Even during intraoperative supplemental oxygen administration, PsqO(2) remains low. Tissue hypoxia is pronounced during surgery and might explain the substantial increase in infection risk in obese patients. It remains unknown whether long-term supplemental postoperative oxygen augments tissue oxygen tension. Consequently, we tested the hypothesis that 80% inspired oxygen administration during 12-18 postoperative hours significantly increases PsqO(2) compared to 30% inspired oxygen fraction.

METHODS

After IRB approval and informed consent, 42 patients undergoing laparoscopic bariatric surgery were randomly assigned to receive either 80% inspired oxygen via a PULMANEX Hi-Ox Mask (Viasys MedSystems, Wheeling, IL) (10 L/min) or 30% oxygen via nasal cannula (2 L/min) after surgery until the next morning. PsqO(2) was measured with a temperature-corrected Clark-type electrode in the subcutaneous tissue of the upper arm and adjacent to the wound.

RESULTS

Postoperative subcutaneous tissue oxygen tension was significantly increased in the Hi-Ox group: 58 (47.7, 74.1) mmHg vs. 43 (38.7, 55.2) mmHg, P = 0.002. Also, wound tissue oxygen tension was improved during supplemental oxygen administration: 75.2 (69.8, 95.5) mmHg vs. 52.4 (46.3, 66.1) mmHg, P < 0.001.

CONCLUSION

Subcutaneous tissue oxygen tension was significantly increased by supplemental postoperative oxygen administration. Whether there is an effect on the incidence of wound infection in morbidly obese patients is matter of further research.

CO2 insufflation influences the temperature of the open surgical wound

In open surgery, heat is lost due to radiation and evaporation through the wound. Hypothermia causes tissue hypoxia and impairs various cellular immune functions that increases the risk for postoperative wound infections and delayed wound healing. The patient's body is usually well protected with heating arrangements, but the open wound is left unprotected and until now no practical method has been available to protect it thermically. We therefore investigated if insufflation of an open surgical wound with carbon dioxide would affect wound temperature. In 10 patients undergoing cardiac surgery, the sternotomy wound was insufflated with dry, room temperature carbon dioxide via a gas diffuser for 2 minutes. A heat-sensitive camera measured the wound temperature before, during, and after insufflation. Exposure to carbon dioxide increased the median temperature of the whole wound by 0.5 degrees C (p=0.01). The temperature of the area distant to the diffuser increased by 1.2 degrees C (p<0.01) whereas in the area close to the diffuser it decreased by 1.8 degrees C (p<0.01). In conclusion, short-term insufflation of dry room temperature carbon dioxide in an open wound increases the surface temperature significantly. Although a small increase, it may reduce the incidence of postoperative wound infections in the future.

Bone and wound healing in the diabetic patient

Impaired soft tissue regeneration and delayed osseous healing are known complications associated with diabetes mellitus with regard to orthopedic surgery, making the management and treatment of diabetic patients undergoing foot and ankle surgery more complex and difficult. At the moment several options are available to address the known issues that complicate the clinical outcomes in these high-risk patients. Using a multifaceted approach, with close attention to intraoperative and perioperative considerations including modification of surgical technique to supplement fixation, local application of orthobiologics, tight glycemic control, administration of supplementary oxygen, and biophysical stimulation via low-intensity pulsed ultrasound and electrical bone stimulation, the impediments associated with diabetic healing can potentially be overcome, to yield improved clinical results for diabetic patients after acute or elective foot and ankle surgery.

Haemodynamic optimisation improves tissue microvascular flow and oxygenation after major surgery: a randomised controlled trial

INTRODUCTION

Post-operative outcomes may be improved by the use of flow related end-points for intra-venous fluid and/or low dose inotropic therapy. The mechanisms underlying this benefit remain uncertain. The objective of this study was to assess the effects of stroke volume guided intra-venous fluid and low dose dopexamine on tissue microvascular flow and oxygenation and inflammatory markers in patients undergoing major gastrointestinal surgery.

METHODS

Randomised, controlled, single blind study of patients admitted to a university hospital critical care unit following major gastrointestinal surgery. For eight hours after surgery, intra-venous fluid therapy was guided by measurements of central venous pressure (CVP group), or stroke volume (SV group). In a third group stroke volume guided fluid therapy was combined with dopexamine (0.5 mcg/kg/min) (SV & DPX group).

RESULTS

135 patients were recruited (n = 45 per group). In the SV & DPX group, increased global oxygen delivery was associated with improved sublingual (P < 0.05) and cutaneous microvascular flow (P < 0.005) (sublingual microscopy and laser Doppler flowmetry). Microvascular flow remained constant in the SV group but deteriorated in the CVP group (P < 0.05). Cutaneous tissue oxygen partial pressure (PtO2) (Clark electrode) improved only in the SV & DPX group (P < 0.001). There were no differences in serum inflammatory markers. There were no differences in overall complication rates between the groups although acute kidney injury was more frequent in the CVP group (CVP group ten patients (22%); pooled SV and SV & DPX groups seven patients (8%); P = 0.03) (post hoc analysis).

CONCLUSIONS

Stroke volume guided fluid and low dose inotropic therapy was associated with improved global oxygen delivery, microvascular flow and tissue oxygenation but no differences in the inflammatory response to surgery. These observations may explain improved clinical outcomes associated with this treatment in previous trials.

TRIAL REGISTRATION NUMBER

ISRCTN 94850719.

Temperature control and the role of supplemental oxygen

Unrecognized and untreated intraoperative hypothermia remains a common avoidable scenario in the modern operating room. Failure to properly address this seemingly small aspect of the total operative care has been shown to have profound negative patient consequences including increased incidence of postoperative discomfort, surgical bleeding, requirement of allogenic blood transfusion, wound infections, and morbid cardiac events. All of these ultimately lead to longer hospitalizations and higher mortality. To avoid such problems, simple methods can be employed by the surgeon, anesthesiologist, and ancillary personnel to ensure euthermia. Similarly, another effortless method to potentially improve surgical outcomes is the liberal use of supplemental oxygen. Promising preliminary data suggests that high-concentration oxygen during and after surgery may decrease the rate of surgical site infections and gastrointestinal anastomotic failure. The precise role of supplemental oxygen in the perioperative period represents an exciting area of potential research that awaits further validation and analysis. In this article, the authors explore the data regarding both temperature regulation and supplemental oxygen use in an attempt to define further their emerging role in the perioperative care of patients undergoing colorectal surgery.

Early postoperative subcutaneous tissue oxygen predicts surgical site infection

BACKGROUND

Subcutaneous oxygen partial pressure is one of several determinants of surgical site infections (SSIs). However, tissue partial pressure is difficult to measure and requires invasive techniques. We tested the hypothesis that early postoperative tissue oxygen saturation (Sto(2)) measured with near-infrared spectroscopy predicts SSI.

METHODS

We evaluated Sto(2) in 116 patients undergoing elective colon resection. Saturation was measured near the surgical incision, at the upper arm, and at the thenar muscle with an InSpectra™ tissue spectrometer model 650 (Hutchinson Technology Inc., Hutchinson, MN) 75 minutes after the end of surgery and on the first postoperative day. An investigator blinded to Sto(2) assessed patients daily for wound infection. Receiver operating characteristic curves were used to analyze the performance of Sto(2) measurements as a predictor of SSI.

RESULTS

In 23 patients (≈ 20%), SSI was diagnosed 9 ± 5 days (mean ± SD) after surgery. Patients who did and did not develop an SSI had similar age (48 ± 14 vs 48 ± 15 years, respectively; P = 0.97) and gender (female:male, 15:8 vs 46:47, respectively), but patients who developed SSI weighed more (body mass index 32 ± 7 vs 27 ± 6 kg/m(2); P < 0.01). Sto(2) at the upper arm was lower in patients who developed SSI than in those who did not develop SSI (52 ± 22 vs 66 ± 21; P = 0.033), and these measurements had a sensitivity of 71% and specificity of 60% for predicting SSI, using Sto(2) of 66% as the cutoff point.

CONCLUSION

Sto(2) measured at the upper arm only 75 minutes after colorectal surgery predicted development of postoperative SSI, although the infections were typically diagnosed more than a week later. Although further testing is required, Sto(2) measurements may be able to predict SSI and thus allow earlier preventive measures to be implemented.

Nitrous oxide makes me sick: or does it? Nitrous oxide and postoperative nausea and vomiting

This article evaluates whether avoidance of nitrous oxide in general anaesthesia can improve clinical outcomes in surgical patients by reducing postoperative nausea and vomiting, and whether avoidance should become part of a routine clinical management strategy. Despite some controversy, the greatest strength of evidence suggests that avoidance of nitrous oxide may be justified as a pre-emptive perioperative strategy as part of a multimodal approach to postoperative nausea and vomiting, especially in those patients known to have a higher baseline risk.