Comparison of the effects of inhalation, epidural, spinal, and combined anesthesia techniques on rat cremaster muscle flap microcirculation

HOW SHOULD TRANEXAMIC ACID BE ADMINISTERED IN HEMORRHAGIC SHOCK? CONTINUOUS SERUM CONCENTRATION MEASUREMENTS IN A SWINE MODEL

ABSTRACT

Background : Tranexamic acid (TXA) reduces mortality in trauma patients. Intramuscular (IM) administration could be advantageous in low-resource and military settings. Achieving the same serum concentration as intravenous (IV) administration is important to achieve equal mortality reduction. Therefore, we aimed to investigate whether dividing an IM dose of TXA between two injection sites and whether an increase in dose would lead to serum concentrations comparable to those achieved by IV administration. Methods : Norwegian landrace pigs (n = 29) from a course in hemostatic emergency surgery were given TXA 1 h after start of surgery. Blood samples were drawn at 0, 5, 10, 15, 20, 25, 35, 45, 60, and 85 min. The samples were centrifuged and serum TXA concentrations quantified with liquid chromatography-tandem mass spectrometry. The use of two injection sites was compared with distributing the dose on one injection site, and a dose of 15 mg/kg was compared with a dose of 30 mg/kg. All IM groups were compared with IV administration. Results : The groups were in a similar degree of shock. Increasing the IM dose from the standard of 15 mg/kg to 30 mg/kg resulted in significantly higher serum concentrations of TXA, comparable to those achieved by IV administration. Distributing the IM dose on two injection sites did not affect drug uptake, as shown by equal serum concentrations. Conclusions : For IM administration of TXA, 30 mg/kg should be the standard dose. With a short delay, IM administration will provide equal serum concentrations as IV administration, above what is considered necessary to inhibit fibrinolysis.

Efficacy of Combined Spinal-Epidural Anesthesia for Lower Extremity Microvascular Reconstruction

INTRODUCTION

Some surgeons have raised concerns regarding the sympathectomy-like effect of epidural anesthesia during lower limb microvascular reconstruction. The combined spinal-epidural (CSE) anesthetic technique incorporates several benefits of spinal and epidural techniques in a single approach. The aim of this study was to analyze the postoperative outcomes of patients undergoing soft-tissue reconstruction of the lower limb by implementing the CSE anesthesia approach.

METHODS

We reviewed medical records from patients who underwent lower limb reconstructive procedures under CSE anesthesia with free tissue transfer from January 2017 to December 2020. We evaluated the postoperative outcomes.

RESULTS

Thirty-eight patients underwent microvascular reconstructive procedures of the lower extremity over the study period. The average age and BMI were 38.4-year and 28 kg/m2. All patients only had one postoperative rescue dose with epidural anesthesia. The most common type of flap used was the anterolateral thigh flap (53%). The average splinting time and length of stay (LoS) were 8.4 days and 18.4 days, respectively. Donor-site complications included wound dehiscence (3%) and surgical site infection (3%). Recipient-site complications included partial flap loss (8%) and total flap loss (10%). No pro re nata morphine analgesia was used. Tramadol and/or ketoprofen were administered for postoperative analgesia. The average time to start physiotherapy and to resume daily activities were 10 days and 29 days, respectively.

CONCLUSIONS

The CSE anesthesia for microvascular reconstruction of the lower limb demonstrated a similar success rate compared to historical records. CSE provided adequate pain management and none of the patients required postoperative monitoring in the ICU.

The effect of dobutamine treatment on salvage of digital replantation and revascularization

PURPOSE

One of the most common causes of a failure after replantation and revascularization surgeries is 'no reflow' from proximal artery that occurs, especially following crush and avulsion injuries. In this study, we aimed to evaluate the effect of dobutamine treatment on salvage of replanted and revascularized digits.

METHODS

The patients with no reflow phenomenon detected in the salvage operations of replanted/revascularized digits between the years 2017 and 2020 were included in the study. Dobutamine treatment was infused at a rate of 4 µg·kg-1·min-1 intraoperatively and of 2 µg·kg-1 min-1 postoperatively. Demographic data (age, sex), digit survival rate, ischemia time, and level of injury were retrospectively analysed. Pre-infusion, intraoperative and postoperative values of cardiac index (CI), mean arterial pressure (MAP), and heart rate (HR) were recorded.

RESULTS

The phenomenon of 'no reflow' was encountered in 35 digits of 22 patients who underwent salvage surgery due to vascular compromise. The survival rate in the revascularization group was 75%, while it was 42.1% in the replanted digits. Metaphysis level of proximal phalanx was the most common localization for 'no reflow' phenomenon. The least values of CI, MAP and HR to obtain sufficient perfusion in salvaged digits were as follows: 4.2 l.min-1.m-2, 76 mm Hg, and 83 beat·min-1, respectively.

CONCLUSIONS

It was demonstrated that dobutamine infusion at a rate of 4 µg·kg-1·min-1 intraoperatively and at 2 µg·kg-1·min-1 postoperatively has favorable effects on the vascular compromise derived from no reflow of proximal artery.

Safety and effectiveness of regional anesthesia compared with anesthetic techniques not using regional anesthesia on outcomes after free tissue flap surgery: a systematic review protocol

OBJECTIVE

This systematic review will aim to evaluate the evidence on the effectiveness of regional anesthesia, when compared with general anesthesia alone, on the outcomes of free flap surgeries.

INTRODUCTION

Free flap procedures involve complete separation of a flap of tissue from its native vascular bed, followed by reimplantation to a recipient site on the body. Optimal perfusion and successful neovascularization are crucial to survival of the grafted flap. Currently, no best-practice recommendations exist regarding the use of regional anesthesia in free flap surgeries. Regional anesthesia techniques have the potential to alter blood flow and neuroendocrine responses to surgical stress, which may impact perfusion and survival of free flap grafts. This potential for augmentation or hindrance of flap perfusion may have a significant impact on patient outcomes, thus meriting systematic review.

INCLUSION CRITERIA

The review will include both experimental and observational (analytical only) study designs that examine the vascular outcomes of regional anesthesia compared with general anesthesia alone in free flap surgery.

METHODS

The databases to be searched include PubMed, CINAHL, Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science Core Collection, Embase, and gray literature sources. Identified studies will be independently assessed by two reviewers utilizing JBI critical appraisal tools. Data will be extracted using a standardized data matrix. Certainty of findings will be conducted using the Grading of Recommendations Assessment, Development and Evaluation approach. Narrative synthesis will be compiled and meta-analysis completed, where possible.

SYSTEMATIC REVIEW REGISTRATION NUMBER

PROSPERO CRD42021283584.

Intramuscular uptake of tranexamic acid during haemorrhagic shock in a swine model

Background

Tranexamic acid (TXA) reduce mortality in bleeding trauma patients, with greater effect if administered early. Serum concentrations above 10 µg/mL are considered sufficient to inhibit fibrinolysis. Normally administered intravenously (i.v.), TXA can also be administered intramuscularly (i.m.). This could be advantageous in low resource and military settings, if sufficient serum concentrations can be reached in shocked patients with reduced muscular blood perfusion. Accordingly, we aimed to: (1) Determine the impact of shock on the pharmacokinetics of i.m. TXA, and (2) Compare the pharmacokinetics of i.v. versus i.m. TXA in ongoing shock.

Materials and methods

In a prospective experimental study, N = 18 Norwegian landrace pigs (40–50 kg), utilised in a surgical course in haemostatic emergency surgery, were subjected to various abdominal and thoracic trauma. After 1 h of surgery the animals were given 15 mg/kg TXA either i.v. or i.m. A control group without injury, or surgery, received intramuscular TXA. Blood samples were drawn at 0, 5, 15, 25, 35, 45, 60 and 85 min. The samples were centrifuged and analysed with liquid chromatography–tandem mass spectrometry (LC–MS/MS) for TXA serum-concentrations.

Results

In shocked pigs, i.m. administration resulted in a mean maximum serum concentration (C_max) of 20.9 µg/mL, and i.v. administration a C_max of 48.1 µg/mL. C_max occurred 15 min after i.m. administration and 5 min after i.v. administration. In non-shocked swine, i.m. administration resulted in a C_max of 36.9 µg/mL after 15 min. In all groups, mean TXA serum concentrations stayed above 10 µg/mL from administration to end of experiments.

Conclusions

I.m. administration of TXA in shocked pigs provides serum concentrations associated with inhibition of fibrinolysis. It may be an alternative to i.v. and intraosseous administration during stabilisation and transport of trauma patients to advanced medical care.

Changes in the microvascular reactivity during spinal anesthesia

PURPOSE

Anesthesia alters microcirculation and tissue oxygen saturation (StO₂). We sought to examine changes in StO₂ using near-infrared spectroscopy and a vascular occlusion test (VOT) during spinal anesthesia.

METHODS

This prospective observational study was included 51 patients without comorbidities who underwent elective surgery under spinal anesthesia. We measured the StO₂ in the lower extremity during VOT before and after intrathecal injection.

RESULTS

The baseline, minimum, and maximum StO₂ values during VOT significantly increased after intrathecal injection (baseline StO₂ from 68.6 ± 7.3% to 77.1 ± 10.1%, minimum StO₂ from 39.7 ± 14.9% to 48.8 ± 17.6%, and maximum StO₂ from 74.2 ± 7.5% to 80.2 ± 10.0%, all P < 0.0001). The occlusion slope and ischemic stimulus did not significantly change after intrathecal injection. The reperfusion slope was 1.38 ± 0.69%/sec before intrathecal injection and significantly decreased to 1.15 ± 0.61%/sec after intrathecal injection (P = 0.0001).

CONCLUSIONS

Our results showed that despite an increased perfusion, reperfusion rate was significantly decreased by spinal anesthesia. Further studies are required to confirm how these contradictory results (improving oxygenation while reducing microvascular reactivity) actually affect the clinical impact of spinal anesthesia on microvascular function.

Dexmedetomidine as an Alternative Anesthetic Agent for Flap Surgery: An Intravital Evaluation in the Cremaster Muscle Flap

INTRODUCTION

Flap surgery is one of the most commonly used techniques of reconstructive surgery for effective repair of damaged tissue. Optimal anesthetic technique and anesthetic agent plays an important role in flap perfusion. This study aimed to evaluate the effects of dexmedetomidine infusion on the microcirculation in the cremaster muscle flap by direct in vivo monitoring.

MATERIALS AND METHODS

We randomly divided 9 Wistar albino rats into 3 groups. The rats in the control group underwent the surgical procedure (isolation of the cremaster muscle) alone; the rats in the experimental groups 1 and 2 received an infusion of dexmedetomidine (10 and 30 min) after the surgical procedure.

RESULTS

The means of vessel diameters, number of functional capillaries, and movements of leukocytes in all groups were evaluated using intravital microscopic examination. The diameters of the arterioles and venules of the cremaster muscle significantly increased in the dexmedetomidine groups. The number of functional capillaries was higher in the dexmedetomidine groups than in the control group. No difference was observed in the movements of leukocytes between the control and experimental groups. Dexmedetomidine significantly increased the diameters of the arterioles and venules of the cremaster flap and the number of functional capillaries.

CONCLUSION

On the basis of the effects of dexmedetomidine on microcirculation, we suggest that dexmedetomidine continue to be used as an anesthetic agent, and may be considered also for reconstructive procedures, particularly flap surgery.

Emerging paradigms in perioperative management for microsurgical free tissue transfer: review of the literature and evidence-based guidelines

BACKGROUND

Microsurgical free tissue transfer has become an increasingly valuable technique in reconstructive surgery. However, there is a paucity of evidence-based guidelines to direct management. A systematic review was performed to define strategies to optimize perioperative management.

METHODS

A systematic review of the literature was performed using key search terms. Strategies to guide patient management were identified, classified according to level of evidence, and used to devise recommendations in seven categories: patient temperature, anesthesia, fluid administration/blood transfusion, vasodilators, vasopressors, and anticoagulation.

RESULTS

A total of 106 articles were selected and reviewed. High-level evidence was identified to guide practices in several key areas, including patient temperature, fluid management, vasopressor use, anticoagulation, and analgesic use.

CONCLUSIONS

Current practices remain exceedingly diverse. Key strategies to improve patient outcomes can be defined from the available literature. Key evidence-based guidelines included that normothermia should be maintained perioperatively to improve outcomes (level of evidence 2b), and volume replacement should be maintained between 3.5 and 6.0 ml/kg per hour (level of evidence 2b). Vasopressors do not harm outcomes and may improve flap flow (level of evidence 1b), with most evidence supporting the use of norepinephrine over other vasopressors (level of evidence 1b). Dextran should be avoided (level of evidence 1b), and pump systems for local anesthetic infusion are beneficial following free flap breast reconstruction (level of evidence 1b). Further prospective studies will improve the quality of available evidence.

A comparison of the effects of epidural and spinal anesthesia with ischemia-reperfusion injury on the rat transverse rectus abdominis musculocutaneous flap

The purpose of this study is to compare the effects of spinal and epidural anesthesia on a rat transverse rectus abdominus myocutaneous flap ischemia-reperfusion injury model.Forty Sprague-Dawley rats were divided into 4 experimental groups: group I (n = 10), sham group; group II (n = 10), control group; group III (n = 10), epidural group; and group IV (n = 10), spinal group. After the elevation of the transverse rectus abdominus myocutaneous flaps, all groups except for the sham group were subjected to normothermic no-flow ischemia for 4 hours, followed by a reperfusion period of 2 hours. At the end of the reperfusion period, biochemical and histopathological evaluations were performed on tissue samples.Although there was no significant difference concerning the malonyldialdehyde, nitric oxide, and paraoxonase levels in the spinal and epidural groups, the total antioxidant state levels were significantly increased, and the total oxidative stress levels were significantly decreased in the epidural group in comparison to the spinal group. The pathological evaluation showed that findings related to inflammation, nuclear change rates and hyalinization were significantly higher in the spinal group compared with the epidural group.Epidural anesthesia can be considered as a more suitable method that enables a decrease in ischemia-reperfusion injuries in the muscle flaps.