Duration of extremity tourniquet application profoundly impacts soft-tissue antibiotic exposure in a rat model of ischemia-reperfusion injury

Prophylactic antibiotic use for penetrating trauma in prolonged casualty care: A review of the literature and current guidelines

ABSTRACT

Prolonged casualty care (PCC), previously known as prolonged field care, is a system to provide patient care for extended periods of time when evacuation or mission requirements surpass available capabilities. Current guidelines recommend a 7- to 10-day course of ertapenem or moxifloxacin, with vancomycin if methicillin-resistant Staphylococcus aureus is suspected, for all penetrating trauma in PCC. Data from civilian and military trauma have demonstrated benefit for antibiotic prophylaxis in multiple types of penetrating trauma, but the recommended regimens and durations differ from those used in PCC, with the PCC guidelines generally recommending broader coverage. We present a review of the available civilian and military literature on antibiotic prophylaxis in penetrating trauma to discuss whether a strategy of broader coverage is necessary in the PCC setting, with the goal of optimizing patient outcomes and antibiotic stewardship, while remaining cognizant of the challenges of moving medical material to and through combat zones. Empiric extended gram-negative coverage is unlikely to be necessary for thoracic, maxillofacial, extremity, and central nervous system trauma in most medical settings. However, providing the narrowest appropriate antimicrobial coverage is challenging in PCC because of limited resources, most notably, delay to surgical debridement. Antibiotic prophylaxis regimen must be determined on a case-by-case basis based on individual patient factors while still considering antibiotic stewardship. Narrower regimens, which focus on matching up the site of infection to the antibiotic chosen, may be appropriate based on available resources and expertise of treating providers. When resources permit in PCC, the narrower cefazolin-based regimens (with the addition of metronidazole for esophageal or abdominal involvement, or gross contamination of central nervous system trauma) likely provide adequate coverage. Levofloxacin is appropriate for ocular trauma. Ideally, cefazolin and metronidazole should be carried by medics in addition to first-line antibiotics (moxifloxacin and ertapenem, Literature Synthesis and Expert Opinion; Level V).

Intravenous Cefazolin Achieves Sustained High Interstitial Concentrations in Open Lower Extremity Fractures

BACKGROUND

Infection remains a serious clinical concern in patients with open fractures, despite timely antibiotic administration and surgical debridement. Soft tissue and periosteal stripping may alter local tissue homeostasis and antibiotic pharmacokinetics in the injured limb. The tissue (interstitial) concentration of intravenously administered antibiotics at an open fracture site has not been characterized using direct sampling techniques.

QUESTION/PURPOSE

We performed this study to evaluate the concentration and pharmacokinetics of intravenously delivered cefazolin at an open fracture site after surgical debridement.

METHODS

Twelve patients with an open fracture distal to the knee who presented at a regional Level I trauma center were approached for enrollment in this nonrandomized, observational study. Of the 12 patients, eight adults (one female, seven male) with a median age of 32 years (range 23 to 51 years) were enrolled and underwent successful sample collection for analysis. Three patients had incomplete datasets because of equipment malfunction and one elected not to participate. Seven patients had open tibia fractures, and one patient had an open fibula fracture associated with a closed tibia fracture. There were six Gustilo-Anderson Type II injuries and two Type IIIA injuries. Empiric antibiotics were administered in the prehospital setting or in the emergency department according to institutional protocol. When patients were taken to the operating room, a 2-g intravenous dose of cefazolin was administered. After surgical debridement, fracture stabilization, and wound closure, a microdialysis catheter was placed transdermally into the injury zone (within 5 cm of the fracture site) and a second catheter was placed in the contralateral uninjured (control) limb. Additional doses of cefazolin were administered every 8 hours postoperatively. Baseline and periodic interstitial fluid and whole blood (plasma) samples were collected in the operating room and at prespecified times for 24 hours postoperatively. Free cefazolin in the interstitial fluid and plasma samples were analyzed by ultra-high-performance liquid chromatography using C 18 column separation with quadrupole time-of-flight mass spectrometry detection. Data from the second postoperative dose of cefazolin were used to characterize pharmacokinetic parameters through a noncompartmental analysis using time-concentration curves of free cefazolin and assuming first-order elimination. For pharmacodynamic analyses, the modal cefazolin minimum inhibitory concentration (MIC) of Staphylococcus aureus (1 µg/mL) was used.

RESULTS

With the samples available, no difference was observed in the median free cefazolin exposure over 24 hours ( f area under the curve [AUC] 0→24hrs ) between injured limbs (352 μg∙hr/mL [IQR 284 to 594 μg∙hr/mL]) and uninjured limbs (341 μg∙hr/mL [IQR 263 to 438 μg∙hr/mL]; p = 0.64). The median time to achieve the maximum concentration of free cefazolin ( f T max ) for injured limbs was delayed (2.7 hours [IQR 2.2 to 3.1 hours]) compared with control limbs (1.7 hours [IQR 1.2 to 2.0 hours]; p = 0.046). The time to the maximum concentration for plasma was not different from that of control limbs (p = 0.08). The time the cefazolin concentration was above the modal S. aureus MIC (T > MIC) in the injured and control limbs over 24 hours was 100% (IQR 100% to 100%) and 100% (IQR 97% to 100%), respectively.

CONCLUSION

These preliminary findings suggest that current prophylactic cefazolin dosing regimens result in successful antibiotic delivery to the traumatized limb in moderately severe open fractures. Although cefazolin delivery to open-fracture wound beds was delayed compared with healthy tissues, the cefazolin concentration was sustained above the European Union Committee Antimicrobial Susceptibility Testing modal MIC for S. aureus , demonstrating a high likelihood of a prophylactic antimicrobial environment at an open fracture site with this empiric antimicrobial regimen. Importantly, patients in this analysis had Gustilo-Anderson Types II and IIIA injuries. Further research with a larger patient cohort is needed to determine whether antibiotic delivery to traumatized soft tissues in patients with higher-grade open fractures (Gustilo-Anderson Types IIIB and IIIC) demonstrates similar pharmacokinetic characteristics.

LEVEL OF EVIDENCE

Level II, therapeutic study.

The optimized tourniquet versus no tourniquet in total knee arthroplasty. Analysis of muscle injury, functional recovery, and knee strength

Background

Tourniquet is widely used in total knee replacement surgery because it reduces intraoperative hemorrhage and provides a comfortable surgical area for the surgeon. It's possible that its use could lead to impaired postoperative functional and motor recovery, as well as local and systemic complications. Our goal was to compare the outcomes of total knee replacement without ischemia using an optimized protocol, consisting of tourniquet inflation before skin incision and deflation after cementing, with a pressure of one hundred millimeters above systolic blood pressure and without postoperative articular suction drains.). We believed that tourniquet effectively would result in no additional muscle damage and no functional or knee strength impairment compared to no tourniquet.

Methods

In a prospective and randomized study, 60 patients with osteoarthritis were evaluated for total knee replacement, divided in two groups: 'without tourniquet' and 'optimized tourniquet'. Outcomes were mean creatine phosphokinase levels, Knee Society Score and knee isokinetic strength. Data were considered significant when p < 0.05.

Results

Creatine phosphokinase levels and functional score were similar between groups. There were no differences between groups regarding knee extension strength on the operated limbs, although the knee flexors' peak torque in the operated limb in the optimized tourniquet group was significantly higher at 6 months relative to preoperative and 3 months assessments.

Conclusions

The optimized tourniquet protocol use in total knee replacement combines the benefits of tourniquet use without compromising functional recovery and without additional muscle damage and strength deficits compared to surgery without its use.

The safety and efficacy of unicompartmental knee arthroplasty in outpatient surgical centers: A systematic review and meta-analysis

BACKGROUND

Unicompartmental knee arthroplasty (UKA) is an effective treatment method for knee osteoarthritis. With the development and implementation of enhanced recovery after surgery, UKA is now increasingly performed in outpatient surgical centers. However, there is ongoing debate regarding the safety and effectiveness of performing UKA in outpatient settings.

METHODS

The search was performed to retrieve randomized controlled trials and cohort studies on outpatient UKA from PubMed, Cochrane Library, EMbase, CNKI, and WanFangData databases. The search was conducted from the inception of the databases until August 31, 2023. After independent screening, data extraction, and risk of bias evaluation by two researchers, meta-analysis was performed using RevMan 5.4 software.

RESULTS

A total of eight studies involving 18,411 patients were included. The results showed that the postoperative transfusion rate in the outpatient group was lower than that in the inpatient group [OR = 0.36, 95%CI (0.24, 0.54), p < 0.00001], and the difference was statistically significant. However, there was no significant difference between the two groups in terms of readmission rate, reoperation rate, surgical site infection, and periprosthetic fracture. The differences were not statistically significant.

CONCLUSION

Compared to the traditional inpatient route, the blood transfusion rate for single-condyle replacement in the outpatient operation center is lower, and there is no significant difference in readmission rate, reoperation rate, surgical site infection, and periprosthesis fracture. The outpatient approach to UKA is safe, feasible, and highly satisfactory for patients. However, the results have certain limitations, and a rigorous preoperative complication risk assessment can minimize the risk of UKA in outpatient surgery centers.

TRIAL REGISTRATION

PROSPERO number CRD42023405373.

Reverse traction with Kirschner wires and bilateral external fixation device combined with minimally invasive plate oseoynthesis technique for tibial plateau fractures of type Schatzker V and VI

PURPOSE

Complex bicondylar tibial plateau fracture (TPF) has always been a tricky problem for surgeons. We created a novel external device used intraoperatively consisting of Kirschner wires, and combined with minimally invasive plate oseoynthesis (MIPO) technique to treat complex bicondylar TPFs, and the clinical effect and feasibility were further evaluated.

METHODS

From March 2016 to February 2021, 49 cases (29 males and 20 females) were identified as bicondylar TPF, the mean age 47.2 (27-69). All patients adopted the device and MIPO technique. A series of score, complications, and radiographs in the follow-up period, from three months, six months, one year, and two years and the last follow-up, were recorded, from visual analogue score (VAS), hospital for special surgery (HSS), and Short-Form 36 (SF-36), containing physical (PCS) and mental (MCS), and Rasmussen score.

RESULTS

Forty-seven patients showed good functional recovery. No patients were lost, mean follow-up time was 28.17 ± 2.81 (24.2-35.4) months. Operation time was 89.80 ± 13.46 (58-110) min. At the last follow-up, VAS was 1.3 ± 0.92 (0-4), HHS was 93.10 ± 2.63 (89-99), PCS was 49.20 ± 7.40 (38-65), and MCS was 50.08 ± 4.77 (43-62). Complications were as follows: cutaneous necrosis (3, 6%), asymptomatic arthritis (3, 6%), symptomatic arthritis (1, 2%), and deep venous thrombosis (1, 2%). Mean fracture healing time was 11.82 ± 1.5 (10-15.4) weeks. All patients got recovery without extra surgery and removed the implants at 12.85 ± 0.76 (11.2-15.4) months.

CONCLUSION

Temporary traction device of bilateral external fixator combined with MIPO technique was simple and convenient, with a smaller soft-tissue damage, an easier operational approach, and its worth being promoted.

Effect of Vacuum Sealing Drainage on Soft Tissue Injury of Traumatic Fracture and Its Effect on Wound Recovery

Purpose

The current work is mainly to explore the effect of vacuum sealing drainage (VSD) on soft tissue injury (STI) caused by traumatic fractures (TFs) and its effect on wound recovery.

Methods

We first selected 90 patients with TF STI from May 2019 to May 2021, of which 40 patients (control group) received routine treatment, and the other 50 patients (observation group) were treated with VSD. The curative effect, rehabilitation (changing dressing frequency, healing time, and hospitalization time), pain severity, patient comfort, and complications were evaluated and compared.

Results

The observation group exhibited a higher total effective rate, lower dressing change frequency, complication rate, and shorter healing time and hospital stay than the control group, which are statistically significant. Statistically milder pain sensation and better patient comfort were also determined in the observation group.

Conclusions

VSD is effective and safe in the treatment of TF-induced sexually transmitted infections, which can effectively accelerate wound recovery while reducing pain sensation and improving patient comfort, with clinical promotion value.

Effects of tourniquet inflation on peri- and postoperative cefuroxime concentrations in bone and tissue

Background and purpose - Tourniquet is widely used in orthopedic surgery to reduce intraoperative bleeding and improve visualization. We evaluated the effect of tourniquet application on peri- and postoperative cefuroxime concentrations in subcutaneous tissue, skeletal muscle, calcaneal cancellous bone, and plasma. The primary endpoint was the time for which the free cefuroxime concentration was maintained above the clinical breakpoint minimal inhibitory concentration (T > MIC) for Staphylococcus aureus (4 µg/mL).Patients and methods - 10 patients scheduled for hallux valgus or hallux rigidus surgery were included. Microdialysis catheters were placed for sampling of cefuroxime concentrations bilaterally in subcutaneous tissue, skeletal muscle, and calcaneal cancellous bone. A tourniquet was applied on the thigh of the leg scheduled for surgery (tourniquet duration time [range]: 65 minutes [58-77]). Cefuroxime (1.5 g) was administered intravenously 15 minutes prior to tourniquet inflation, followed by a second dose 6 hours later. Dialysates and venous blood samples were collected for 12 hours.Results - A cefuroxime concentration of 4 µg/mL was reached within 23 minutes in all compartments and patients. For cefuroxime the T > MIC (4 µg/mL) ranged between 4.8 and 5.4 hours across compartments, with similar results for the tourniquet and non-tourniquet leg. Comparable T > MIC and penetration ratios were found for the first and second dosing intervals.Interpretation - Administration of cefuroxime (1.5 g) 15 minutes prior to tourniquet inflation is safe in order to achieve tissue concentrations above 4 µg/mL throughout surgery. A tourniquet application time of approximately 1 hour did not affect the cefuroxime tissue penetration in the following dosing interval.

Antibiotics in Necrotizing Soft Tissue Infections

Necrotizing soft tissue infections (NSTIs) are rare life-threatening bacterial infections characterized by an extensive necrosis of skin and subcutaneous tissues. Initial urgent management of NSTIs relies on broad-spectrum antibiotic therapy, rapid surgical debridement of all infected tissues and, when present, treatment of associated organ failures in the intensive care unit. Antibiotic therapy for NSTI patients faces several challenges and should (1) carry broad-spectrum activity against gram-positive and gram-negative pathogens because of frequent polymicrobial infections, considering extended coverage for multidrug resistance in selected cases. In practice, a broad-spectrum beta-lactam antibiotic (e.g., piperacillin-tazobactam) is the mainstay of empirical therapy; (2) decrease toxin production, typically using a clindamycin combination, mainly in proven or suspected group A streptococcus infections; and (3) achieve the best possible tissue diffusion with regards to impaired regional perfusion, tissue necrosis, and pharmacokinetic and pharmacodynamic alterations. The best duration of antibiotic treatment has not been well established and is generally comprised between 7 and 15 days. This article reviews the currently available knowledge regarding antibiotic use in NSTIs.

Semimechanistic Modeling of the Effects of Blast Overpressure Exposure on Cefazolin Pharmacokinetics in Mice

Cefazolin is a first-line antibiotic to treat infection related to deployment-associated blast injuries. Prior literature demonstrated a 331% increase cefazolin liver area under the curve (AUC) in mice exposed to a survivable blast compared with controls. We repeated the experiment, validated the findings, and established a semimechanistic two-compartment pharmacokinetic (PK) model with effect compartments representing the liver and skin. We found that blast statistically significantly increased the pseudo-partition coefficient to the liver by 326% (95% confidence interval: 76-737%), which corresponds to the observed 331% increase in cefazolin liver AUC described previously. To a lesser extent, plasma AUC in blasted mice increased 14-45% compared with controls. Nevertheless, the effects of blast on cefazolin PK were transient, normalizing by 10 hours after the dose. It is unclear as to how this blast effect t emporally translates to humans; however, given the short-lived effect on PK, there is insufficient evidence to recommend cefazolin dosing changes based on blast overpressure injury alone. Clinicians should be aware that cefazolin may cause drug-induced liver injury with a single dose and the risk may be higher in patients with blast overpressure injury based on our findings. SIGNIFICANCE STATEMENT: Blast exposure significantly, but transiently, alters cefazolin pharmacokinetics in mice. The questions of whether other medications or potential long-term consequences in humans need further exploration.

Low-molecular-weight heparin calcium attenuates the tourniquet-induced ischemia-reperfusion injury in rats

Ischemia-reperfusion injury (IRI) is a common postoperative complication of the tourniquet used surgery; low-molecular-weight heparin calcium (LMWH) is frequently used postoperatively to prevent the formation of deep venous thrombosis. However, subcutaneous hemorrhage can usually be seen in patients who underwent lower limb surgery, especially in total knee arthroplasty, the influence of LMWH on IRI remains controversial. In this experiment, we designed an animal model to observe the influence of LMWH on the skeletal muscle injury induced by tourniquets. Sprague-Dawley (SD) rats underwent either 2 h of unilateral hindlimb ischemia or anesthesia alone, at different time points of reperfusion interval, animals received either 4mg/kg LMWH or normal saline subcutaneously twice a day. The levels of inflammatory markers in serum, the expression of apoptosis proteins, as well as histological examination of skeletal muscles, were detected at 48-h reperfusion. We found that the injury of skeletal muscle and the systemic inflammatory response was less severe in LMWH-treated animals, indicating that LMWH could attenuate the tourniquet-induced IRI. In conclusion, LMWH given postoperatively after limb surgery may be clinically beneficial.

Evaluation of Pseudomonas aeruginosa pathogenesis and therapeutics in military-relevant animal infection models

Modern combat-related injuries are often associated with acute polytrauma. As a consequence of severe combat-related injuries, a dysregulated immune response results in serious infectious complications. The gram-negative bacterium Pseudomonas aeruginosa is an opportunistic pathogen that often causes life-threatening bloodstream, lung, bone, urinary tract, and wound infections following combat-related injuries. The rise in the number of multidrug-resistant P. aeruginosa strains has elevated its importance to civilian clinicians and military medicine. Development of novel therapeutics and treatment options for P. aeruginosa infections is urgently needed. During the process of drug discovery and therapeutic testing, in vivo testing in animal models is a critical step in the bench-to-bedside approach, and required for Food and Drug Administration approval. Here, we review current and past literature with a focus on combat injury-relevant animal models often used to understand infection development, the interplay between P. aeruginosa and the host, and evaluation of novel treatments. Specifically, this review focuses on the following animal infection models: wound, burn, bone, lung, urinary tract, foreign body, and sepsis.

A Retrospective Study of Factors Influencing the Survival of Modified Meek Micrografting in Severe Burn Patients

Modified Meek micrografting is a common method for treating severe burn patients. This study was to analyze the factors affecting the survival of modified Meek micrografting, thereby improving the survival rate of skin grafts. Eighty-three patients who underwent modified Meek micrografting were analyzed. According to the survival rate of skin graft after operation, the patients were divided into good skin survival group (GSSG, survival rate ≥ 70%, 47 cases) and poor skin survival group (PSSG, survival rate < 70%, 36 cases). The baseline data, surgical information, perioperative laboratory indicators, and prognosis of the patients were statistically analyzed. The univariate analysis and repeated measurement showed the burn severity, Meek skin graft area, duration of anesthesia, the postoperative sepsis shock, the mortality, the neutrophils percentage on the third day after surgery (NEU3), and the growth rate of neutrophils percentage from the first to third day after surgery (NEU3-1%) in the GSSG were significantly lower than those in the PSSG, whereas the perioperative average albumin levels and the perioperative average pre-albumin levels were higher. Receiver operating characteristic curve showed that the NEU3 had a good predictive value for the survival of skin slices. Maintaining perioperative albumin levels at a high level, controlling perioperative infection, and shortening the operation time as much as possible may improve the survival rate of modified Meek micrografting.