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

Perioperative risk assessment - focus on functional capacity

PURPOSE OF REVIEW

This review examines how functional capacity informs preoperative risk stratification, as well as strengths and limitations of options for estimating functional capacity.

RECENT FINDINGS

Functional capacity (or cardiopulmonary fitness) overlaps with other important characteristics, including muscular strength, balance, and frailty. Poor functional capacity is associated with postoperative morbidity, especially noncardiovascular complications. Both patient interviews and exercise tests are used to assess functional capacity. The usual approach of an unstructured patient interview does not predict outcomes. Structured interviews that incorporate validated questionnaires (Duke Activity Status Index) or standardized questions about physical activity (ability to climb stairs) do predict moderate-or-severe complications and cardiovascular complications. Among exercise tests, cardiopulmonary exercise testing (CPET) has shown the most consistent association with risks of complications. Other tests (6-min walk test, incremental shuttle walk test, stair climbing) might predict complications, but still require further high-quality evaluation.

SUMMARY

A straightforward way to better assess functional capacity is a structured interview with validated questionnaires or standardized questions about physical activities. Functional capacity can also be assessed by exercise tests, with the strongest evidence supporting CPET. Although some simpler exercise tests have shown promise, more research remains needed to better define their role in preoperative evaluation.

Continuous wound infiltration of ropivacaine for reducing of postoperative pain after anterior lumbar fusion surgery: a clinical retrospective comparative study

Background

Local anesthetic infiltration at the site of a surgical wound is commonly used to control postoperative pain. In this study, we examined the effectiveness of continuous local infiltration at an abdominal surgical site in patients undergoing anterior lumbar interbody fusion (ALIF) surgery.

Methods

Sixty-one patients who underwent ALIF surgery were enrolled. For thirty-one of them, a continuous local anesthetics infiltration system was used at the abdominal site. We collected data regarding the patients’ sleep quality; satisfaction with pain control after surgery; abilities to perform physical tasks and the additional application of opioids in the postoperative 48 hours.

Results

The On-Q system group showed reduced visual analogue scale scores for pain at the surgical site during rest and movement at 0, 12, 24, and 48 hours; and more was satisfied with pain control management at the first postoperative day (7.0 ± 1.2 vs. 6.0 ± 1.4; P = 0.003) and week (8.1 ± 1.6 vs. 7.0 ± 1.8; P = 0.010) than the control group. The number of additional patient-controlled analgesia (PCA) bolus and pethidine injections was lower in the On-Q group (PCA 3.67 ± 1.35 vs. 4.60 ± 1.88; P = 0.049 and pethidine 2.09 ± 1.07 vs. 2.73 ± 1.38; P = 0.032). Patients who used the On-Q system performed more diverse activity and achieved earlier ambulation than those in the control group.

Conclusions

Continuous wound infiltration with ropivacaine using an On-Q system may be effective for controlling postoperative pain after ALIF surgery.

Liposomal Bupivacaine Infiltration After Median Sternotomy in Pediatric Cardiac Surgery

OBJECTIVE

The present study retrospectively ascertained whether liposomal bupivacaine (LB) injected subcutaneously after median sternotomy incisions in pediatric cardiac surgery patients is as efficacious as the ON-Q PainBuster pump (ON-Q) (Avonas Medical, Alpharetta, GA).

DESIGN

Retrospective cohort comparison.

SETTING

Pediatric hospital.

PARTICIPANTS

Cardiac surgery patients who were treated with LB for elective cardiac surgery.

INTERVENTIONS

Patients received 4 mg/kg of LB admixed with 0.25% bupivacaine and 0.9% normal saline. These patients were compared with an age- and procedure-matched control group of similar size treated with the ON-Q pump (continuous infusion 0.25% bupivacaine via subcutaneous catheter). Total analgesics used and route, other analgesics or sedatives, and pain scores (first 24 hours and cumulative) were tracked for 96 hours after surgery.

MEASUREMENTS AND MAIN RESULTS

A total of 222 patients were equally divided between the two groups. Overall, the median (interquartile range) age was 6.5 (3.8-12.7) years. Unadjusted analysis suggested that patients in the LB group were administered a significantly higher dose of intravenous acetaminophen (77.4 v 60.0 mg/kg; p < 0.05). Extubation in the operating room was significantly higher in the LB patients (p < 0.05). Narcotic (morphine) administration was significantly higher in the ON-Q group (100.0% v 95.5%; p < 0.05). Although the median pain score within the first 24 hours was higher in LB patients (27.0 v 17.0; p < 0.05), there was a significantly greater difference observed in the Numeric Rating Scale area under the curve for the ON-Q group.

CONCLUSIONS

LB is at least as effective as the ON-Q is for providing analgesia after median sternotomy incision in children.

Effects of intraoperative high versus low inspiratory oxygen fraction (FiO2) on patient's outcome: A systematic review of evidence from the last 20 years

Despite numerous studies, controversies about the best intraoperative FiO2 remain. In 2016, the World Health Organization (WHO) recommended that adult patients undergoing general anaesthesia should be ventilated intraoperatively with an 80% FiO2 to reduce surgical site infection (SSI). However, several data suggest that hyperoxia could have adverse effects. In order to determine the potential effect of FiO2 on SSI, we included in this systematic review 23 studies (among which 21 randomised controlled trials [RCT]) published between 1999 and 2020, comparing intraoperative high versus low FiO2. Results were heterogeneous but most recent studies on one hand, and the largest RCTs on the other hand, reported no difference on the incidence of SSI regarding intraoperative FiO2 during general anaesthesia. There was also no difference in the incidence of SSI depending of intraoperative FiO2 in patients receiving regional anaesthesia. The review on secondary endpoints (respiratory and cardiovascular adverse events, postoperative nausea and vomiting, postoperative length-of-stay and mortality) also failed to support the use of high FiO2. On the opposite, some data from follow-up analyses and registry studies suggested a possible negative effect of high intraoperative FiO2 on long-term outcomes. In conclusion, the systematic administration of a high intraoperative FiO2 in order to decrease SSI or improve other perioperative outcomes seems unjustified in the light of the evidence currently available in the literature.

Effect of Intraoperative Goal-Directed Fluid Management on Tissue Oxygen Tension in Obese Patients: a Randomized Controlled Trial

Background

Perioperative subcutaneous tissue oxygen tension (PsqO₂) is substantially reduced in obese surgical patients. Goal-directed fluid therapy optimizes cardiac performance and thus tissue perfusion and oxygen delivery. We therefore tested the hypothesis that intra- and postoperative PsqO₂ is significantly reduced in obese patients undergoing standard fluid management compared to goal-directed fluid administration.

Methods

We randomly assigned 60 obese patients (BMI ≥ 30 kg/m²) undergoing laparoscopic bariatric surgery to receive either esophageal Doppler-guided goal-directed fluid management or conventional fluid treatment. Our primary outcome parameter was intra- and postoperative PsqO₂ measured with a polarographic electrode in the subcutaneous tissue of the upper arm. A random effects linear regression model was used to analyze the effect of intervention.

Results

Overall, mean (± SD) PsqO₂ was significantly higher in obese patients receiving goal-directed therapy compared to conventional fluid therapy (65.8 ± 28.0 mmHg vs. 53.7 ± 21.7, respectively; repeated measures design adjusted difference: 13.0 mmHg [95% CI 2.3 to 23.7; p = 0.017]). No effect was seen intraoperatively (69.6 ± 27.9 mmHg vs. 61.4 ± 28.8, difference: 9.7 mmHg [95% CI -3.8 to 23.2; p = 0.160]); however, goal-directed fluid management improved PsqO₂ in the early postoperative phase (63.1 ± 27.9 mmHg vs. 48.4 ± 12.5, difference: 14.5 mmHg [95% CI 4.1 to 24.9; p = 0.006]). Intraoperative fluid requirements did not differ between the two groups.

Conclusions

Goal-directed fluid therapy improved subcutaneous tissue oxygenation in obese patients. This effect was more pronounced in the early postoperative period.

Clinical Trial Number and Registry

The study was registered at ClinicalTrials.gov (NCT 01052519).

wIRA: hyperthermia as a treatment option for intracellular bacteria, with special focus on Chlamydiae and Mycobacteria

The emergence of antibiotic-resistant bacteria in the last century is alarming and calls for alternative, nonchemical treatment strategies. Thermal medicine uses heat for the treatment of infectious diseases but its use in facultative and obligate intracellular bacteria remains poorly studied. In this review, we summarize previous research on reducing the infectious burden of Mycobacterium ulcerans and Chlamydia trachomatis by using water-filtered infrared A-radiation (wIRA), a special form of heat radiation with high tissue penetration and low thermal load on the skin surface. Mycobacterium ulcerans is a thermosensitive bacterium causing chronic necrotizing skin disease. Therefore, previous data on wIRA-induced improvement of wound healing and reduction of wound infections is summarized first. Then, pathogenesis and treatment of infections with M. ulcerans causing Buruli ulcer and of those with C. trachomatis infecting the ocular conjunctiva and resulting in blinding trachoma are discussed. Both bacteria cause neglected tropical diseases and have similar geographical distributions. Results of previous in vitro and in vivo studies using wIRA on M. ulcerans and C. trachomatis infections are presented. Finally, technical aspects of using wIRA in patients are critically reviewed and open questions driving future research are highlighted. In conclusion, wIRA is a promising tool for reducing infectious burden due to intracellular bacteria such as M. ulcerans and C. trachomatis.

Micron Scale Spatial Measurement of the O2 Gradient Surrounding a Bacterial Biofilm in Real Time

O₂ is a fundamental environmental metabolite that affects all life on earth. While toxic to many microbes and obligately required by others, those that have appropriate physiological responses survive and can even benefit from various levels of O₂, particularly in biofilm communities. Although most studies have focused on measuring O₂ within biofilms, little is known about O₂ gradients surrounding biofilms. Here, we developed electrochemical methodology based on scanning electrochemical microscopy to measure the O₂ gradients surrounding biofilms in real time on the micron scale. Our results reveal that P. aeruginosa biofilms produce a hypoxic zone that can extend hundreds of microns from the biofilm surface and that this gradient remains even after the addition of antibiotic concentrations that eradicated 99% of viable cells. Our results provide a high resolution of the O₂ gradients produced by P. aeruginosa biofilms and reveal sustained O₂ consumption in the presence of antibiotics.

Bacteria alter their local chemical environment through both consumption and the production of a variety of molecules, ultimately shaping the local ecology. Molecular oxygen (O₂) is a key metabolite that affects the physiology and behavior of virtually all bacteria, and its consumption often results in O₂ gradients within sessile bacterial communities (biofilms). O₂ plays a critical role in several bacterial phenotypes, including antibiotic tolerance; however, our understanding of O₂ levels within and surrounding biofilms has been hampered by the difficulties in measuring O₂ levels in real-time for extended durations and at the micron scale. Here, we developed electrochemical methodology based on scanning electrochemical microscopy to quantify the O₂ gradients present above a Pseudomonas aeruginosa biofilm. These results reveal that a biofilm produces a hypoxic zone that extends hundreds of microns from the biofilm surface within minutes and that the biofilm consumes O₂ at a maximum rate. Treating the biofilm with levels of the antibiotic ciprofloxacin that kill 99% of the bacteria did not affect the O₂ gradient, indicating that the biofilm is highly resilient to antimicrobial treatment in regard to O₂ consumption.

Perioperative and anesthetic risk factors of surgical site infection in patients undergoing pancreaticoduodenectomy: A retrospective cohort study

Background

Surgical site infection is a major perioperative issue. The morbidity of surgical site infection is high in major digestive surgery, such as pancreaticoduodenectomy. The comprehensive risk factors, including anesthetic factors, for surgical site infection in pancreaticoduodenectomy are unknown. The aim of this study was to investigate the perioperative and anesthetic risk factors of surgical site infection in pancreaticoduodenectomy.

Methods

This was a retrospective cohort study conducted in a single tertiary care center. A total of 326 consecutive patients who underwent pancreaticoduodenectomy between January 2009 and March 2018 were evaluated. Patients who underwent resection of other organs were excluded. The primary outcome was the incidence of surgical site infection, based on a Clavien-Dindo classification of grade 2 or higher. Multivariable logistic regression analysis was performed to investigate the association between surgical site infection and perioperative and anesthetic factors.

Results

Of the 326 patients, 116 (35.6%) were women. The median age was 70 years (interquartile range; 64–75). The median duration of surgery was 10.9 hours (interquartile range; 9.5–12.4). Surgical site infection occurred in 60 patients (18.4%). The multivariable analysis revealed that the use of desflurane as a maintenance anesthetic was associated with a significantly lower risk of surgical site infection than sevoflurane (odds ratio, 0.503; 95% confidence interval [CI], 0.260–0.973). In contrast, the duration of surgery (odds ratio, 1.162; 95% CI, 1.017–1.328), cerebrovascular disease (odds ratio, 3.544; 95% CI, 1.326–9.469), and ischemic heart disease (odds ratio, 10.839; 95% CI, 1.887–62.249) were identified as significant risk factors of surgical site infection.

Conclusions

Desflurane may be better than sevoflurane in preventing surgical site infection in pancreaticoduodenectomy. Cerebrovascular disease and ischemic heart disease are potential newly-identified risk factors of surgical site infection in pancreaticoduodenectomy.

Personalised haemodynamic management targeting baseline cardiac index in high-risk patients undergoing major abdominal surgery: a randomised single-centre clinical trial

BACKGROUND

Despite several clinical trials on haemodynamic therapy, the optimal intraoperative haemodynamic management for high-risk patients undergoing major abdominal surgery remains unclear. We tested the hypothesis that personalised haemodynamic management targeting each individual's baseline cardiac index at rest reduces postoperative morbidity.

METHODS

In this single-centre trial, 188 high-risk patients undergoing major abdominal surgery were randomised to either routine management or personalised haemodynamic management requiring clinicians to maintain personal baseline cardiac index (determined at rest preoperatively) using an algorithm that guided intraoperative i.v. fluid and/or dobutamine administration. The primary outcome was a composite of major complications (European Perioperative Clinical Outcome definitions) or death within 30 days of surgery. Secondary outcomes included postoperative morbidity (assessed by a postoperative morbidity survey), hospital length of stay, mortality within 90 days of surgery, and neurocognitive function assessed after postoperative Day 3.

RESULTS

The primary outcome occurred in 29.8% (28/94) of patients in the personalised management group, compared with 55.3% (52/94) of patients in the routine management group (relative risk: 0.54, 95% confidence interval [CI]: 0.38 to 0.77; absolute risk reduction: -25.5%, 95% CI: -39.2% to -11.9%; P<0.001). One patient assigned to the personalised management group, compared with five assigned to the routine management group, died within 30 days after surgery (P=0.097). There were no clinically relevant differences between the two groups for secondary outcomes.

CONCLUSIONS

In high-risk patients undergoing major abdominal surgery, personalised haemodynamic management reduces a composite outcome of major postoperative complications or death within 30 days after surgery compared with routine care.

CLINICAL TRIAL REGISTRATION

NCT02834377.

Impact of body mass index on postoperative outcomes in patients undergoing radical resection for hilar cholangiocarcinoma

BACKGROUND

Body mass index (BMI) has been widely used as a prognostic indicator. The association between preoperative BMI and postoperative morbidity in patients with hilar cholangiocarcinoma (HCCA) has not been proved. This study aimed to identify the association between preoperative BMI and postoperative morbidity following radical resection of HCCA.

METHODS

Patients were divided into three groups according to preoperative BMI: low BMI (≤18.4 kg/m² ), normal BMI (18.4-24.9 kg/m² ), and high BMI (≥24.9 kg/m² ). Baseline characteristics, operative variables, postoperative 30-day mortality, and morbidity were compared. Risk factors associated with postoperative morbidity were assessed using univariable and multivariable logistic analyses.

RESULTS

Among 260 patients, 183 (70.4%) had normal BMI, 32 (12.3%) had low BMI, and 45 (17.3%) had high BMI. Compared to the patients with normal-BMI, both low and high BMI patients exhibited a significantly higher postoperative morbidity (87.5% and 82.2% vs 63.9%, P = .019 and P = .025, respectively). Additionally, the multivariable analysis revealed that both low and high BMI patients remained independently associated with an increased risk of postoperative morbidity. (OR: 3.707, 95% CI: 1.080-12.725, P = .037; and OR: 2.858, 95% CI: 1.167-7.002, P = .022, respectively).

CONCLUSION

BMI is an independent risk factor for higher postoperative morbidity in patients who undergo surgical treatment of hilar cholangiocarcinoma.

Risk factors for Staphylococcus aureus surgical site infections after orthopaedic and trauma surgery in a French university hospital

BACKGROUND

Surgical site infections (SSI) after orthopaedic surgery are responsible for reduced quality of life, increased length of hospital stay and costs. The most commonly identified organism is Staphylococcus aureus but risk factors for S. aureus SSI are not well-known. The aim of this study was to evaluate the incidence rate trend of S. aureus SSI over the years and risk factors of these infections in a French University Hospital.

METHODS

SSI rates were expressed as cumulative incidence rates per year. A case-control study nested within a prospective cohort of patients undergoing orthopaedic or trauma surgery from January 1st^, 2012 to April 30th^, 2015 was performed. Cases were patients with S. aureus SSI; controls were patients without SSI. Risk factors of S. aureus SSI were identified by univariate and multivariable analysis.

RESULTS

Of 7438 interventions, 50 (0.7%) S. aureus SSI were identified, without significant increase by years. A total of 46 S. aureus SSI was matched to 91 controls. Risk factors for S. aureus SSI were smoking (odds-ratio (OR) = 8.4, 95%CI 1.2-59.6) and National Nosocomial Infections Surveillance System score (NNISS) ≥1 (OR = 5.8, 95%CI 1.8-19.1). Having 1 or 2 preoperative antiseptic showers (OR = 0.3, 95%CI 0.1-0.7) was a protective factor.

CONCLUSION

The rate of S. aureus SSI is not negligible after orthopaedic and trauma surgery. It seems imperative to strengthen smoking cessation recommendations, and to recall the importance of preoperative antiseptic showers. Systematic screening and decolonization for S. aureus carriage before orthopaedic and trauma surgery could be a means to prevent these infections.

Role of oxygen in wound healing

Not only does oxygen play an essential role in each stage of the wound healing process. It also helps to increases host resistance to infection. Any impairment to the oxygen supply can therefore delay healing. This article explores the affects of oxygen on the wound cells and tissue, and explains how an adequate supply is required for granulation tissue formation and epithelialisation to occur

Current Strategies in Prevention of Postoperative Infections in Spine Surgery

STUDY DESIGN

Narrative review.

OBJECTIVES

Postoperative surgical site infections (SSIs) are among the most common acute complications in spine surgery and have a devastating impact on outcomes. They can lead to increased morbidity and mortality as well as greater economic burden. Hence, preventive strategies to reduce the rate of SSIs after spine surgery have become vitally important. The purpose of this article was to summarize and critically analyze the available evidence related to current strategies in the prevention of SSIs after spine surgery.

METHODS

A literature search utilizing Medline database was performed. Relevant studies from all the evidence levels have been included. Recommendations to decrease the risk of SSIs have been provided based on the results from studies with the highest level of evidence.

RESULTS

SSI prevention occurs at each phase of care including the preoperative, intraoperative, and postoperative periods. Meticulous patient selection, tight glycemic control in diabetics, smoking cessation, and screening/eradication of Staphylococcus aureus are some of the main preoperative patient-related preventive strategies. Currently used intraoperative measures include alcohol-based skin preparation, topical vancomycin powder, and betadine irrigation of the surgical site before closure. Postoperative infection prophylaxis can be performed by administration of silver-impregnated or vacuum dressings, extended intravenous antibiotics, and supplemental oxygen therapy.

CONCLUSIONS

Although preventive strategies are already in use alone or in combination, further high-level research is required to prove their efficacy in reducing the rate of SSIs in spine surgery before evidence-based standard infection prophylaxis guidelines can be built.

Association Between Body Mass Index and Complications in Acoustic Neuroma Surgery

Objectives

Elevated body mass index (BMI) is a risk factor for surgical complications, but data in acoustic neuroma surgery are conflicting and limited to small single-institution studies. This work evaluates associations between BMI and complications in surgery for acoustic neuroma (AN).

Study Design

Retrospective review.

Setting:

Two tertiary otology referral institutions.

Subjects and Methods

Patients undergoing surgery for AN. Univariate and multivariate analysis of association between BMI and complications was performed using two-tailed t tests and binary logistic regression.

Results

BMI ranged from 18.0 kg/m2 to 63.9 kg/m2 with mean of 29.2 kg/m2 among 362 included patients. High BMI was associated with increased risk of cerebrospinal fluid (CSF) leak ( p = 0.003) and need for revision surgery within 6 months ( p = 0.03). CSF leak occurred in 11.6% of obese patients (BMI ≥ 30.0) and 5.1% of patients with BMI < 30.0. There was no association between BMI and post-operative intracranial hemorrhage, wound infection, or incomplete resection ( p > 0.05). Multivariate analysis revealed BMI was associated with CSF leak (odds ratio 1.11 per BMI point, p = 0.002) and need for revision surgery (odds ratio 1.07 per BMI point, p = 0.02) independent of age, gender, tumor size, or surgical approach.

Conclusions

The largest series to date investigating BMI in acoustic surgery is presented. Elevated BMI is strongly associated with CSF leak and need for revision surgery but not with other complications. Obese or overweight patients undergoing acoustic neuroma resection should be counseled of their increased risk of CSF leak.

Therapeutic Effects of Hyperbaric Oxygen in the Process of Wound Healing

Chronic and non-healing wounds, especially diabetic foot ulcers and radiation injuries, imply remarkable morbidity with a significant effect on the quality of life and a high sanitary cost. The management of these wounds requires complex actions such as surgical debris, antibiotic treatment, dressings and even revascularization. These wounds are characterized by poor oxygen supply resulting in inadequate oxygenation of the affected tissue. The adjuvant treatment with hyperbaric oxygen therapy (HBOT) may increase tissue oxygenation favoring the healing of wounds which do not respond to the usual clinical care. The increase in the partial pressure of oxygen contributes to cover the energy demands necessary for the healing process and reduces the incidence of infections. Moreover, the increase in oxygen leads to the production of reactive species with hormetic activity, acting on signaling pathways that modulate the synthesis of inflammation mediators, antioxidants and growth factors which can contribute to the healing process. Studies performed with cell cultures and in animal models seem to demonstrate the beneficial effects of HBOT. However, clinical trials do not show such conclusive results; thus, additional randomized placebo-controlled studies are necessary to determine the real efficacy of HBOT and the mechanism of action for various types of wounds.

Perioperative Hyperoxyphobia: Justified or Not? Benefits and Harms of Hyperoxia during Surgery

The use of an inspiratory oxygen fraction of 0.80 during surgery is a topic of ongoing debate. Opponents claim that increased oxidative stress, atelectasis, and impaired oxygen delivery due to hyperoxic vasoconstriction are detrimental. Proponents point to the beneficial effects on the incidence of surgical site infections and postoperative nausea and vomiting. Also, hyperoxygenation is thought to extend the safety margin in case of acute intraoperative emergencies. This review provides a comprehensive risk-benefit analysis for the use of perioperative hyperoxia in noncritically ill adults based on clinical evidence and supported by physiological deduction where needed. Data from the field of hyperbaric medicine, as a model of extreme hyperoxygenation, are extrapolated to the perioperative setting. We ultimately conclude that current evidence is in favour of hyperoxia in noncritically ill intubated adult surgical patients.

Oxygen-Independent Antimicrobial Photoinactivation: Type III Photochemical Mechanism?

Since the early work of the 1900s it has been axiomatic that photodynamic action requires the presence of sufficient ambient oxygen. The Type I photochemical pathway involves electron transfer reactions leading to the production of reactive oxygen species (superoxide, hydrogen peroxide, and hydroxyl radicals), while the Type II pathway involves energy transfer from the PS (photosensitizer) triplet state, leading to production of reactive singlet oxygen. The purpose of the present review is to highlight the possibility of oxygen-independent photoinactivation leading to the killing of pathogenic bacteria, which may be termed the "Type III photochemical pathway". Psoralens can be photoactivated by ultraviolet A (UVA) light to produce DNA monoadducts and inter-strand cross-links that kill bacteria and may actually be more effective in the absence of oxygen. Tetracyclines can function as light-activated antibiotics, working by a mixture of oxygen-dependent and oxygen independent pathways. Again, covalent adducts may be formed in bacterial ribosomes. Antimicrobial photodynamic inactivation can be potentiated by addition of several different inorganic salts, and in the case of potassium iodide and sodium azide, bacterial killing can be achieved in the absence of oxygen. The proposed mechanism involves photoinduced electron transfer that produces reactive inorganic radicals. These new approaches might be useful to treat anaerobic infections or infections in hypoxic tissue.

Factors associated with infection of primary total knee prosthesis in older adults in a referral hospital in Peru. 2012-2015

OBJECTIVE

To determine the risk factors associated with prosthetic knee infection in elderly patients in a referral hospital in Peru.

PATIENTS AND METHODS

A case and control study was performed. The calculated sample was 44 cases and 132 controls. The data were collected retrospectively from clinical records. U-Mann Whitney and Chi-square tests were performed in the comparison of cases and controls. Odds ratios (OR) were calculated in a binary logistic regression analysis to identify the risk factors, a P<.05 and a 95% confidence interval (CI) were considered significant.

RESULTS

Significant (P<.05) risk factors evidenced in the bivariate analysis were obesity (OR=9.72; 95%CI: 4.47-21.14), smoking (OR=4.06; 95%CI: 1.59-10.39), rheumatoid arthritis (OR=4.66; 95%CI: 1.52-14.32), diabetes mellitus type2 (OR=5.63; 95%CI: 2.69-11.78), persistent drainage (OR=9.27; 95%CI: 3.85-22.31), superficial infection (OR=6.87; 95%CI: 3.25-14.49) and prolonged hospital stay (OR=4.67; 95%CI: 2.26-9.64). In the multivariate analysis where it was adjusted for confounding variables, it was determined that risk factors were obesity (ORa=9.14; 95%CI: 3.28-25.48), diabetes mellitus (ORa=3.77; 95%CI: 1.38-10.32), persistent drainage (ORa=4.64; 95%CI: 1.03-20.80) and superficial wound infection (ORa=27.35; 95%CI: 2.57-290.64).

CONCLUSIONS

Risk factors for prosthetic knee infection identified in this study are preventable. The main risk factors were obesity, diabetes mellitus type2, superficial wound infection and persistent drainage, which were considered together or separately to be risk factors in the population studied.

Effects of oxygen on post-surgical infections during an individualised perioperative open-lung ventilatory strategy: a randomised controlled trial

BACKGROUND

We aimed to examine whether using a high fraction of inspired oxygen (FIO₂) in the context of an individualised intra- and postoperative open-lung ventilation approach could decrease surgical site infection (SSI) in patients scheduled for abdominal surgery.

METHODS

We performed a multicentre, randomised controlled clinical trial in a network of 21 university hospitals from June 6, 2017 to July 19, 2018. Patients undergoing abdominal surgery were randomly assigned to receive a high (0.80) or conventional (0.3) FIO₂ during the intraoperative period and during the first 3 postoperative hours. All patients were mechanically ventilated with an open-lung strategy, which included recruitment manoeuvres and individualised positive end-expiratory pressure for the best respiratory-system compliance, and individualised continuous postoperative airway pressure for adequate peripheral oxyhaemoglobin saturation. The primary outcome was the prevalence of SSI within the first 7 postoperative days. The secondary outcomes were composites of systemic complications, length of intensive care and hospital stay, and 6-month mortality.

RESULTS

We enrolled 740 subjects: 371 in the high FIO₂ group and 369 in the low FIO₂ group. Data from 717 subjects were available for final analysis. The rate of SSI during the first postoperative week did not differ between high (8.9%) and low (9.4%) FIO₂ groups (relative risk [RR]: 0.94; 95% confidence interval [CI]: 0.59-1.50; P=0.90]). Secondary outcomes, such as atelectasis (7.7% vs 9.8%; RR: 0.77; 95% CI: 0.48-1.25; P=0.38) and myocardial ischaemia (0.6% [n=2] vs 0% [n=0]; P=0.47) did not differ between groups.

CONCLUSIONS

An oxygenation strategy using high FIO₂ compared with conventional FIO₂ did not reduce postoperative SSIs in abdominal surgery. No differences in secondary outcomes or adverse events were found.

CLINICAL TRIAL REGISTRATION

NCT02776046.

Obstetric perineal tears: risk factors, wound infection and dehiscence: a prospective cohort study

PURPOSE

To assess risk factors for perineal tears, wound infection and dehiscence among primiparous women.

METHODS

A prospective cohort study at four Danish hospitals (Odense, Esbjerg, Aarhus and Kolding) among 603 primiparous women sampled in three groups: 203 with none/labia/1st degree, 200 with 2nd degree, and 200 with 3rd/4th degree tears included between July 2015 and January 2018. Baseline data were obtained and a clinical examination of perineal wound healing was performed 11-21 days postpartum. Main outcome measurements were as follows: degree of perineal tear, 1st to 4th, analyzed with a case-control approach, infection (purulent drainage or wound abscess), and wound dehiscence (a gap between wound edges > 0.5 cm).

RESULTS

Instrumental delivery and birthweight > 4000 g increased the risk of 3rd/4th degree tears (adjusted Odds Ratio [aOR] 13.7, 95% confidence interval [CI] 5.48-34.1 and aOR 3.27, 95% CI 1.52-7.04, respectively). BMI > 35 kg/m2 increased the risk of wound infection and dehiscence (aOR 7.66, 95% CI 2.13-27.5 and aOR 3.46, 95% CI 1.10-10.9, respectively). Episiotomy tripled the risk of infection (aOR 2.97, 95% CI 1.05-8.41). Treatment with antibiotics during delivery and postpartum seemed to decrease the risk of dehiscence (aOR 0.32, 95% CI 0.15-0.70).

CONCLUSIONS

Instrumental delivery and high birth weight increased the risk of perineal tears. Severe obesity and episiotomy increased the risk of perineal wound complications. More focus on these women may be warranted postpartum. The use of prophylactic antibiotics among women in high risk of wound complications should be further investigated in interventional studies.

Does Revascularization Prior to Foot and Ankle Surgery Reduce the Incidence of Surgical Site Infection (SSI)?

RECOMMENDATION

Several studies support the effect of peripheral vascular disease (PVD) on wound healing and surgical site infection (SSI). Despite this, there have been no specific studies proving the beneficial effect of revascularization on SSI prior to operative intervention in the setting of traumatic or elective foot and ankle surgery. The majority of studies on revascularization are in the setting of diabetic foot infection or established ischemia. We recommend that in the presence of an inadequate vascularization in the foot and ankle, vascular optimization should be undertaken prior to elective surgery.

LEVEL OF EVIDENCE

Limited.

DELEGATE VOTE

Agree: 100%, Disagree: 0%, Abstain: 0% (Unanimous, Strongest Consensus).

Intraoperative Hyperoxia Does Not Reduce Postoperative Pain: Subanalysis of an Alternating Cohort Trial

BACKGROUND

Postoperative pain is common and promotes opioid use. Surgical wounds are hypoxic because normal perfusion is impaired. Local wound ischemia and acidosis promote incisional pain. Some evidence suggests that improving oxygen supply to surgical wounds might reduce pain. We therefore tested the hypothesis that supplemental (80% inspired) intraoperative oxygen reduces postoperative pain and opioid consumption.

METHODS

We conducted a post hoc analysis of a large, single-center alternating cohort trial allocating surgical patients having general anesthesia for colorectal surgery to either 30% or 80% intraoperative oxygen concentration in 2-week blocks for a total of 39 months. Irrespective of allocation, patients were given sufficient oxygen to maintain saturation ≥95%. Patients who had regional anesthesia or nerve blocks were excluded. The primary outcome was pain and opioid consumption during the initial 2 postoperative hours, analyzed jointly. The secondary outcome was pain and opioid consumption over the subsequent 24 postoperative hours. Subgroup analyses of the primary outcome were conducted for open versus laparoscopic procedures and for patients with versus without chronic pain.

RESULTS

A total of 4702 cases were eligible for analysis: 2415 were assigned to 80% oxygen and 2287 to 30% oxygen. The groups were well balanced on potential confounding factors. Average pain scores and opioid consumption were similar between the groups (mean difference in pain scores, -0.01 [97.5% CI, -0.16 to 0.14; P = .45], median difference in opioid consumption, 0.0 [97.5% CI, 0 to 0] mg morphine equivalents; P = .82). There were also no significant differences in the secondary outcome or subgroup analyses.

CONCLUSIONS

Supplemental intraoperative oxygen does not reduce acute postoperative pain or reduce opioid consumption.

Body Mass Index does not affect intraoperative goal-directed fluid requirements

BACKGROUND

Perioperative normovolemia is a major determinant of tissue oxygen availability and postoperative outcome. Thus, adequate volume replacement therapy remains an essential part of perioperative management. Nevertheless, volume optimization in overweight and obese surgical patients with alterations in cardiovascular function, peripheral perfusion, and body composition remains challenging. We, therefore, tested the hypothesis that Body Mass Index (BMI) correlates with fluid requirements during goal-directed management. Furthermore, we evaluated subcutaneous tissue oxygen tension (PsqO2) as an indicator of intravascular volume status and peripheral perfusion.

METHODS

Ninety women, undergoing open gynecologic surgery, were assigned to three groups according to their BMI, (lean: BMI 18.5 to 24.9 kg/m2, overweight: BMI 25 to 29.9 kg/m2, obese: BMI>30 kg/m2). Esophageal Doppler monitoring guided intraoperative crystalloid administration. Tissue oxygen tension was measured with a polarographic electrode in the subcutaneous tissue of the upper arm and served as a secondary outcome parameter.

RESULTS

BMI and fluid requirements did not correlate (r=0.093, P=0.384). Total amounts of administered crystalloids were comparable. Lean patients received 2223±1811 mL in total, while overweight patients received 1866±1261 mL. Obese patients required 2416±1143 mL of total crystalloids (P=0.327). Intra- and postoperative PsqO2 did not differ significantly (97.3 vs. 86.8 vs. 79.6 mmHg, P=0.06 and 74.5 vs. 83 vs. 81.5 mmHg, P=0.63, respectively).

CONCLUSIONS

BMI did not affect intraoperative fluid requirements. Doppler-guided intravascular volume optimization was associated with well-maintained subcutaneous tissue oxygen availability in all BMI groups.

Effect of Hyperoxygenation During Surgery on Surgical Site Infection in Colorectal Surgery

Purpose

Despite the use of different surgical methods, surgical site infection is still an important cause of mortality and morbidity in patients and imposes a considerable cost on the healthcare system. Administration of supplemental oxygen during surgery has been reported to reduce surgical site infection (SSI); however, that result is still controversial. This study was performed to evaluate the effect of hyperoxygenation during colorectal surgery on the incidence of wound infection.

Methods

This study was a prospective double-blind case-control study. The main aim of the study was to evaluate the effect of hyperoxygenation during colorectal surgery on the incidence of SSI. Also, secondary outcomes, such as atelectasis, pneumonia, respiratory failure, length of hospital stay, and required hospitalization in the intensive care unit were evaluated.

Results

SSI was recorded in 2 patients (2 of 40, 5%) in the hyperoxygenation group (FiO₂ 80%) and 6 patients (6 of 40, 15%) in the control group (FiO₂ 30%) (P < 0.05). Time of hospitalization was 6 ± 6.4 days in the hyperoxygenation group and 9.2 ± 2.4 days in the control group (P < 0.05).

Conclusion

This study showed a positive effect of hyperoxygenation in reducing SSI in colorectal surgery, especially surgery in an emergency setting. When the low risk, low cost, and effectiveness of this method in patients undergoing a laparotomy are considered, it is recommended for all patients undergoing colorectal surgery.

Subcutaneous Radiographic Measurement: A Marker to Evaluate Surgical Site Infection Risk in Elderly Hip Fracture Patients

Objectives: Obesity is a documented comorbidity that is prevalent in the elderly population and a known predictor for surgical site infection (SSI). Body mass index is a convenient method to classify obesity, but it fails to account for fat distribution. The objective of our study was to evaluate the association between surgical site infection and a subcutaneous radiographic measurement (SRM) in elderly hip fracture patients. Materials and Methods: A retrospective case-control study was conducted to compare SRMs at the hip in patients diagnosed with surgical site infection after hip fracture surgery with patients that were not diagnosed with surgical site infection. Each case was matched to two controls. An SRM was defined as the distance from the tip of the greater trochanter to the skin following a perpendicular line to the femoral diaphysis in anteroposterior hip radiographs. Clinical diagnosis of acute surgical site infection was based on Tsukayama criteria. Results: Patients with an SRM greater than 6.27cm had a 7-fold increase in the odds of surgical site infection (OR=7.42, 95% Confidence Interval (CI)=3.01-18.28, p<0.001) compared to those with smaller measurements. The odds ratio (OR) for infection of patients with an ASA score of 3 was 15.82(95% CI=5.11-48.9, p-value<0.001) A statistically significant difference between cases and controls was also found when SRM at the hip was analyzed as a continuous variable. Patients with an infection had a 2.24cm (95% CI=1.59 - 2.90; p<0.001) greater mean SRM. Conclusion: Results of our study suggest an association between the SRM at the hip and the risk of SSI in elderly patients with surgically treated hip fractures. SRM may be a helpful tool for evaluating the risk of SSI in elderly hip fracture patients.

Effectiveness of 80% vs 30-35% fraction of inspired oxygen in patients undergoing surgery: an updated systematic review and meta-analysis

BACKGROUND

In 2016, the World Health Organization (WHO) strongly recommended the use of a high fraction of inspired oxygen (FiO₂) in adult patients undergoing general anaesthesia to reduce the risk of surgical site infection (SSI). Since then, further trials have been published, trials included previously have come under scrutiny, and one article was retracted. We updated the systematic review on which the recommendation was based.

METHODS

We performed a systematic literature search from January 1990 to April 2018 for RCTs comparing the effect of high (80%) vs standard (30-35%) FiO₂ on the incidence of SSI. Studies retracted or under investigation were excluded. A random effects model was used for meta-analyses; the sources of heterogeneity were explored using meta-regression.

RESULTS

Of 21 RCTs included, six were newly identified since the publication of the WHO guideline review; 17 could be included in the final analyses. Overall, no evidence for a reduction of SSI after the use of high FiO₂ was found [relative risk (RR): 0.89; 95% confidence interval (CI): 0.73-1.07]. There was evidence that high FiO₂ was beneficial in intubated patients [RR: 0.80 (95% CI: 0.64-0.99)], but not in non-intubated patients [RR: 1.20 (95% CI: 0.91-1.58); test of interaction; P=0.048].

CONCLUSIONS

The WHO updated analyses did not show definite beneficial effect of the use of high perioperative FiO₂, overall, but there was evidence of effect of reducing the SSI risk in surgical patients under general anaesthesia with tracheal intubation. However, the evidence for this beneficial effect has become weaker and the strength of the recommendation needs to be reconsidered.

Decreases in Oral Tissue Blood Flow Induced by Remifentanil Are Not Accompanied by Deterioration of Oral Tissue Oxygen Tension in Rabbits

PURPOSE

The purpose of this study was to investigate the effects of remifentanil infusion on tissue blood flow and tissue oxygen tension in the mandibular bone marrow and masseter muscle in rabbits. In addition, changes in tissue oxygen consumption in those tissues during remifentanil infusion were investigated.

MATERIALS AND METHODS

Sixteen male tracheotomized Japanese White rabbits were anesthetized with sevoflurane under mechanical ventilation. Under oxygen and air inhalation, fraction of inspiratory oxygen was set at 0.4 and remifentanil was infused at a rate of 0.4 μg ∙ kg^-1 ∙ min^-1. Measurements were performed before remifentanil infusion, 20 minutes after the start of remifentanil infusion, and 20 and 60 minutes after the completion of remifentanil infusion (n = 8). The observed variables included heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), mandibular bone marrow tissue blood flow (BBF), masseter muscle tissue blood flow (MBF), mandibular bone marrow tissue oxygen tension (PbO₂), and masseter muscle tissue oxygen tension (PmO₂). Another 8 rabbits were observed for arterial pH, lactate, base excess (BE), and tissue oxygen consumption in the region from which the retromandibular vein received venous blood. Measurements were performed before remifentanil infusion and 20 minutes after the start of remifentanil infusion.

RESULTS

HR, SBP, DBP, MAP, BBF, and MBF decreased during remifentanil infusion. PbO₂ increased 20 minutes after remifentanil infusion and returned to almost the baseline value 60 minutes after remifentanil infusion. PmO₂ did not change throughout the experiment. The difference between the arterial oxygen content of the femoral artery and the venous oxygen content of the retromandibular vein decreased during remifentanil infusion. Arterial pH, lactate, and BE did not change during remifentanil infusion.

CONCLUSIONS

Remifentanil decreased BBF and MBF but did not decrease PbO₂ and PmO₂. It is suggested that tissue oxygen consumption decreased during remifentanil infusion.

Mathematical modeling of oxygen release from hyperbarically loaded polymers

Polymer-based scaffolds are used extensively in the field of regenerative medicine. These biomaterials may induce therapeutic responses through modulating a wound microenvironment with or without the addition of cells. It has long been known that oxygen is a crucial component of the microenvironment that influences cellular and physiological processes such as metabolism, proliferation, differentiation, matrix deposition, phagocytic killing, and wound healing. Consequently, several studies have investigated the potential for using oxygen-eluting biomaterials to regulate the oxygen tension within a wound microenvironment and to tune the regenerative response. We recently demonstrated that hyperbarically loaded polymers could be used as oxygen delivery devices for biomedical uses. To further develop this strategy, it is important to quantitatively characterize the spatiotemporal oxygen diffusion profile from scaffolds. Here, we use analytical and numerical solutions to describe the profiles of oxygen diffusion from hyperbarically loaded polymers as a function of different scaffold geometries, material compositions, and ambient temperatures. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018 © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 35: e2751, 2019.

Surgical site infection: the "Achilles Heel" of all types of abdominal wall hernia reconstruction

PURPOSE

Surgical site infection is the most common hospital-acquired infection in surgical patients. Recently, public health organizations have updated prevention guidelines. This review discusses surgical site infections as a complication of abdominal wall reconstruction.

METHODS

The authors reviewed guidelines on prevention of surgical site infections from the Center for Disease Control and Prevention, World Health Organization, and National Institute for Health and Care Excellence and put them into context with the relevant abdominal wall reconstruction literature. This was the subject of the Nyhus-Wantz lecture given at The International Hernia Congress on March 14, 2018 in Miami, FL and is summarized here.

RESULTS

Routine use of preoperative antibiotics in prosthetic groin hernia repair is not supported by the available literature. High-quality data on antibiotic prophylaxis in ventral (both primary and incisional) hernia repair is lacking, but it is widely utilized and may reduce SSIs. Recommended preventative strategies discussed in this manuscript include: treatment of remote site infections, perioperative normothermia and normoglycemia, avoidance of hypoxemia, antiseptic preparation of surgical team hands and patient skin, treatment of obesity, smoking cessation, correction of malnutrition, and physical conditioning.

CONCLUSION

Surgical site infections lead to significant morbidity and mortality, hernia recurrences, prolonged hospital stay, and increased hospital costs. This makes surgical site infections the "Achilles Heel" of abdominal wall reconstruction. Strict adherence to standardized guidelines and preoperative optimization of patients' risk profiles are crucial to decrease the incidence of surgical site infections.

Development of a novel in situ gelling skin dressing: Delivering high levels of dissolved oxygen at pH 5.5

BACKGROUND AND AIMS

Wound healing requires appropriate oxygen and pH levels. Oxygen therapy and pH-modulating treatments have shown positive effects on wound healing. Thus, a dressing, which combines high levels of dissolved oxygen (DO) with the pH of intact skin, may improve wound healing. Our aims were to (1) formulate an in situ gelling dressing with high levels of DO and with the pH level of intact skin, (2) evaluate physical and chemical properties of the dressing, and (3) elucidate basic effects of elevated levels of DO on human skin cells in vitro.

METHODS

A dressing was formulated with 15 to 16 wt% poloxamer 407, acetate buffer, and oxygenated water. Stability of pH and DO, rheology, and shelf life were analysed. Furthermore, in vitro studies of the effect of increased levels of DO were performed.

RESULTS

An in situ gelling wound dressing, with a DO concentration ranging between 25 and 35 mg/L and a pH of 5.5, was formulated. The DO concentration was stable above 22 mg/L for at least 30 hours when applied on a surface at 35°C and covered for directed diffusion into the intended wound area. At storage, the dressing had stable pH for 3 months and stable DO concentration over 30 mg/L for 7 weeks. Increasing DO significantly enhanced intracellular ATP in human skin cells, without changing reactive oxygen species production, proliferation rate, or viability.

CONCLUSION

The developed dressing may facilitate wound healing by delivering controlled and stable oxygen levels, providing adjustable pH for optimized healing, and increasing intracellular ATP availability.

Periarticular Soft Tissue Envelope Size and Postoperative Wound Complications Following Total Knee Arthroplasty

BACKGROUND

Periprosthetic joint infection following total knee arthroplasty (TKA) is a serious complication often related to obesity which leads to poor patient outcomes and increased resource utilization. A periarticular soft tissue index (PASTI) may help predict postoperative wound complications than BMI alone.

METHODS

Three hundred seventy-six TKA patients with a preoperative, lateral knee X-ray radiograph and 1 year of follow up were analyzed. We used 2 pairs of soft tissue and bony measurements, one referencing the femur and the other the tibia. A high PASTI was defined as a ratio >3.0. Minor complications involved clinical interventions related to the surgical wound. Major complications involved return to the operating room.

RESULTS

More minor complications occurred in high PASTI for both tibial (20.9% vs 6.4%; odds ratio 3.89, 95% confidence interval 1.94-7.79, P < .001) and femoral measurements (15.3% vs 7.2%; odds ratio 2.09, 95% confidence interval 1.06-4.15, P = .013). Major complications were also more frequent in high PASTI, though not statistically significant. The proportion of obesity (BMI > 30) in both minor (12.4% vs 7.7%, P = .140) and major complications (2.8% vs 3.3%, P = .788) was not statistically different.

CONCLUSION

More wound complications occurred in patients with high PASTI, while no difference was seen using BMI. BMI has traditionally approximated patient size, but does not describe variations in body habitus. PASTI is a more reliable and direct way to assess the periarticular soft tissue envelope size, which is associated with postoperative wound complications in the knee.

Unilateral application of an external pneumatic compression therapy improves skin blood flow and vascular reactivity bilaterally

Background

We sought to determine the effects of unilateral lower-limb external pneumatic compression (EPC) on bilateral lower-limb vascular reactivity and skin blood flow.

Methods

Thirty-two participants completed this two-aim study. In AIM1 (n = 18, age: 25.5 ± 4.7 years; BMI: 25.6 ± 3.5 kg/m²), bilateral femoral artery blood flow and reactivity (flow mediated dilation [FMD]) measurements were performed via ultrasonography at baseline (PRE) and immediately following 30-min of unilateral EPC treatment (POST). AIM2 (n = 14, age: 25.9 ± 4.5; BMI: 27.2 ± 2.7 kg/m²) involved 30-min unilateral EPC (n = 7) or sham (n = 7) treatment with thermographic bilateral lower-limb mean skin temperature (MST) measurements at baseline, 15-min of treatment (T15) and 0, 30 and 60-min (R0, R30, R60) following treatment.

Results

Comparative data herein are presented as mean ± 95% confidence interval. AIM1: No significant effects on total reactive hyperemia blood flow were observed for the treated (i.e., compressed) or untreated (i.e., non-compressed) leg. A significant effect of time, but no time*leg interaction, was observed for relative FMD indicating higher reactivity bilaterally with unilateral EPC treatment (FMD: +0.41 ± 0.09% across both legs; p < 0.05). AIM2: Unilateral EPC treatment was associated with significant increases in whole-leg MST from baseline during (T15: +0.63 ± 0.56 °C in the visible untreated/contralateral leg, p < 0.025) and immediately following treatment (i.e., R0) in both treated (+1.53 ± 0.59 °C) and untreated (+0.60 ± 0.45 °C) legs (p < 0.0125). Across both legs, MST remained elevated with EPC at 30-min post-treatment (+0.60 ± 0.45 °C; p < 0.0167) but not at 60-min post (+0.27 ± 0.46 °C; p = 0.165). Sham treatment was associated with a significant increase in the treated leg immediately post-treatment (+1.12 ± 0.31 °C; p < 0.0167), but not in the untreated leg (−0.27 ± 0.12 °C). MST in neither the treated or untreated leg were increased relative to baseline at R30 or R60 (p > 0.05). Finally, during treatment and at all post-treatment time points (i.e., R0, R30 and R60), independent of treatment group (EPC vs. sham), there was a significant effect of region. The maximum increase in MST was observed at the R0 time point and was significantly (p < 0.05) larger in the thigh region (+1.02 ± 0.31 °C) than the lower-leg (+0.47 ± 0.29 °C) region. However, similar rates of MST decline from R0 in the thigh and lower leg regions were observed at the R30 and R60 time points.

Discussion

Unilateral EPC may be an effective intervention for increasing skin blood flow and/or peripheral conduit vascular reactivity in the contralateral limb. While EPC was effective in increasing whole-leg MST bilaterally, there appeared to be a more robust response in the thigh compared to the lower-leg. Thus, proximity along the leg may be an important consideration in prospective treatment strategies.

Neonatal brain resting-state functional connectivity imaging modalities

Infancy is the most critical period in human brain development. Studies demonstrate that subtle brain abnormalities during this state of life may greatly affect the developmental processes of the newborn infants. One of the rapidly developing methods for early characterization of abnormal brain development is functional connectivity of the brain at rest. While the majority of resting-state studies have been conducted using magnetic resonance imaging (MRI), there is clear evidence that resting-state functional connectivity (rs-FC) can also be evaluated using other imaging modalities. The aim of this review is to compare the advantages and limitations of different modalities used for the mapping of infants' brain functional connectivity at rest. In addition, we introduce photoacoustic tomography, a novel functional neuroimaging modality, as a complementary modality for functional mapping of infants' brain.

Postoperative Analgesia After Wound Infiltration With Tramadol and Dexmedetomidine as an Adjuvant to Ropivacaine for Lumbar Discectomies: A Randomized-controlled Clinical Trial

INTRODUCTION

Crippling postoperative pain linked with lumbar discectomies not only shackles patient's normal daily activities but also lengthens their hospital stay. So, allaying postoperative pain in these patients has become a substantive component in neuroanesthesia to expedite neurological recovery. Wound infiltration with local anesthetics is widely used to optimize postoperative pain. Different adjuvants like dexmedetomidine and tramadol when added to local anesthetics prolongs postoperative analgesia. The aim of this trial was to evaluate the analgesic efficacy of tramadol and dexmedetomidine when added to ropivacaine for wound infiltration in lumbar discectomies.

METHODOLOGY

This study was prospective, randomized, double-blind, controlled in nature conducted among 45 adult patients belonging to American Society of Anesthesiologists' physical status 1 and 2, of either sex aged between 30 and 70 years undergoing elective lumbar discectomies. They were randomly allocated into 3 equal groups: group R received 100 mg of 0.5% ropivacaine (20 mL) and 2 mL normal saline, group RT received 100 mg of 0.5% ropivacaine (20 mL) and 2 mg/kg tramadol (2 mL), and group RD received 100 mg of 0.5% ropivacaine (20 mL) and 0.5 μg/kg dexmedetomidine (2 mL) (total volume, 22 mL). Visual analog scale at 0, 2, 4, 6, 12, 18, and 24 hours; time to first rescue analgesia, total supplemental analgesic consumption and side effects (if any) were assessed during first 24 hours postoperatively.

RESULTS

The median time to first rescue analgesia (median; 95% confidence interval [CI]) in group RD was 930 (854.3 to 1005.7) minutes. This was significantly longer (P=0.000) than group RT (420 [366.3 to 473.7] min) or group R (270 [243.2 to 296.8] min). Postoperative diclofenac consumed (median [interquartile range]) was 150 (150 to 200) mg in group R, 150 (75 to 150) mg in group RT and 75 (75 to 150) mg in group RD (P=0.008). Significant differences in mean visual analog scale scores were observed among the 3 groups at hours 0 (P=0.033), 2 (P=0.001), 4 (P=0.000), 6 (P=0.001), and 24 (P=0.013). No statistical significant side effects could be discerned among the groups.

CONCLUSIONS

We concluded that wound infiltration with combined ropivacaine and dexmedetomidine found to be significantly superior for postoperative analgesia compared with either combined ropivacaine and tramadol or ropivacaine alone for lumbar discectomies.

Infection and Rerupture After Surgical Repair of Achilles Tendons

Background:

Surgical repair of an Achilles tendon rupture has been shown to decrease rerupture rates. However, surgery also increases the risk of complications, including infection.

Purpose:

To determine the risk factors for infection and rerupture after primary repair of Achilles tendon ruptures.

Study Design:

Cohort study; Level of evidence, 3.

Methods:

A retrospective review was performed on 423 patients who underwent operative treatment of Achilles tendon ruptures between the years 2008 and 2014. The primary outcome of interest was the total rate of infection, and the secondary outcome of interest was the incidence of rerupture within 2 years of operation.

Results:

A total of 423 patients were analyzed, with a mean age of 46 years (range, 16-83 years) and a mean body mass index of 31.4 kg/m² (range, 17-55 kg/m²). The overall infection rate was 2.8%, and the rerupture rate was 1%. The median time between surgery and superficial surgical site infection was 30 days, and the median time between surgery and rerupture was 38 days. Longer tourniquet times (100.3 ± 34.7 minutes vs 69.9 ± 21.4 minutes; P = .04) and greater estimated blood loss (15.0 ± 9.1 mL vs 5.1 ± 12.0 mL; P = .01) were associated with an increased rate of deep surgical site infections. Patients who had longer operation and tourniquet times trended toward higher rerupture rates (P = .06 and .08, respectively). When compared with nonsmokers, current and previous smokers had an increased incidence of superficial or deep surgical site infections (6.25% vs 1.42%; P = .02). Age, sex, race, body mass index, alcohol use, diabetes, past steroid injections, and mechanism of injury did not contribute to complication rates.

Conclusion:

Achilles tendon repairs were associated with a low risk of infection and rerupture. Patients with longer tourniquet times, higher estimated blood loss, and a history of smoking were at increased risk for surgical site infections. Patients with longer operative times had increased rates of rerupture.

Design of a portable phantom device to simulate tissue oxygenation and blood perfusion

We propose a portable phantom system for calibration and validation of medical optical devices in a clinical setting. The phantom system comprises a perfusion module and an exchangeable tissue-simulating phantom that simulates tissue oxygenation and blood perfusion. The perfusion module consists of a peristaltic pump, two liquid storage units, and two pressure suppressors. The tissue-simulating phantom is fabricated by a three-dimensional (3D) printing process with microchannels embedded to simulate blood vessels. Optical scattering and absorption properties of biologic tissue are simulated by mixing graphite powder and titanium dioxide powder with clear photoreactive resin at specific ratios. Tissue oxygen saturation (StO₂) and blood perfusion are simulated by circulating the mixture of blood and intralipid at different oxygenation levels and flow rates. A house-made multimodal imaging system that combines multispectral imaging and laser speckle imaging are used for non-invasive detection of phantom oxygenation and perfusion, and the measurements are compared with those of a commercial Moor device as well as numerical simulation. By acquiring multimodal imaging data from one phantom and applying the calibration factors in different settings, we demonstrate the technical feasibility to calibrate optical devices for consistent measurements. By simulating retina tissue vasculature and acquiring functional images at different tissue oxygenation and blood perfusion levels, we demonstrate the clinical potential to simulate tissue anomalies. Our experiments imply the clinical potential of a portable, low-cost, and traceable phantom standard to calibrate and validate medical optical devices for improved performance.

Effect of intraoperative hyperoxia on the incidence of surgical site infections: a meta-analysis

BACKGROUND

Whether supplemental intraoperative oxygen reduces surgical site infections remains unclear. Recent recommendations from the World Health Organization and Center for Disease Control to routinely use high inspired oxygen concentrations to reduce infection risk have been widely criticized. We therefore performed a meta-analysis to evaluate the influence of inspired oxygen on infection risk, including a recent large trial.

METHODS

A systematic literature search was performed. Primary analysis included all eligible trials. Sensitivity analyses distinguished studies of colorectal and non-colorectal surgeries, and excluded studies with high risk of bias. Another post-hoc sensitivity analysis excluded studies from one author that appear questionable.

RESULTS

The primary analysis included 26 trials (N=14,710). The RR [95%CI] for wound infection was 0.81 [0.70, 0.94] in the high vs. low inspired oxygen groups. The effect remained significant in colorectal patients (N=10,469), 0.79 [0.66, 0.96], but not in other patients (N=4,241), 0.86 [0.69, 1.09]. When restricting the analysis to studies with low risk of bias, either by strict inclusion criteria (N=5,047) or by researchers' judgment (N=12,547), no significant benefit remained: 0.84 [0.67, 1.06] and 0.89 [0.76, 1.05], respectively.

CONCLUSIONS

When considering all available data, intraoperative hyperoxia reduced wound infection incidence. However, no significant benefit remained when analysis was restricted to objective- or investigator-identified low-bias studies, although those analyses were not as well-powered. Meta-analysis of the most reliable studies does not suggest that supplemental oxygen substantively reduces wound infection risk, but more research is needed to fully answer this question.

Increased visceral tissue perfusion with heated, humidified carbon dioxide insufflation during open abdominal surgery in a rodent model

Tissue perfusion during surgery is important in reducing surgical site infections and promoting healing. This study aimed to determine if insufflation of the open abdomen with heated, humidified (HH) carbon dioxide (CO2) increased visceral tissue perfusion and core body temperature during open abdominal surgery in a rodent model. Using two different rodent models of open abdominal surgery, visceral perfusion and core temperature were measured. Visceral perfusion was investigated using a repeated measures crossover experiment with rodents receiving the same sequence of two alternating treatments: exposure to ambient air (no insufflation) and insufflation with HH CO2. Core body temperature was measured using an independent experimental design with three treatment groups: ambient air, HH CO2 and cold, dry (CD) CO2. Visceral perfusion was measured by laser speckle contrast analysis (LASCA) and core body temperature was measured with a rectal thermometer. Insufflation with HH CO2 into a rodent open abdominal cavity significantly increased visceral tissue perfusion (2.4 perfusion units (PU)/min (95% CI 1.23-3.58); p<0.0001) compared with ambient air, which significantly reduced visceral blood flow (-5.20 PU/min (95% CI -6.83- -3.58); p<0.0001). Insufflation of HH CO2 into the open abdominal cavity significantly increased core body temperature (+1.15 ± 0.14°C) compared with open cavities exposed to ambient air (-0.65 ± 0.52°C; p = 0.037), or cavities insufflated with CD CO2 (-0.73 ± 0.33°C; p = 0.006). Abdominal visceral temperatures also increased with HH CO2 insufflation compared with ambient air or CD CO2, as shown by infrared thermography. This study reports for the first time the use of LASCA to measure visceral perfusion in open abdominal surgery and shows that insufflation of open abdominal cavities with HH CO2 significantly increases visceral tissue perfusion and core body temperature.