Simultanes nichtinvasives Monitoring mit Laser-Doppler-Flussmessung und Gewebespektrometrie bei fasziokutanen Radialislappen und osteokutanen Fibulatransplantaten

Evaluation of peri-implant perfusion in patients who underwent avascular augmentation or microvascular reconstruction using laser Doppler flowmetry and tissue spectrophotometry: a prospective comparative clinical study

OBJECTIVES

The aim of this study was to evaluate the peri-implant perfusion, such as oxygen saturation, the relative amount of hemoglobin, and blood flow, in implants placed in pristine bone and avascular and microvascular grafts using a non-invasive measurement method.

MATERIALS AND METHODS

A total of 58 patients with 241 implants were included. Among them, 106 implants were based in native bone (group I), 75 implants were inserted into avascular bone grafts (group II), and 60 implants were placed in microvascular bone grafts (group III). Gingival perfusion was measured using laser Doppler flowmetry and tissue spectrophotometry (LDF-TS). Implants with signs of gingival inflammation were excluded to analyze healthy implant perfusion in different bony envelopes.

RESULTS

The mean values for oxygen saturation, relative hemoglobin levels, and blood flow did not differ significantly between the groups (p = 0.404, p = 0.081, and p = 0.291, respectively). There was no significant difference in perfusion between implants that were surrounded by mucosa and implants based within cutaneous transplants (p = 0.456; p = 0.628, and p = 0.091, respectively).

CONCLUSION

No differences in perfusion were found between implants inserted into native bone and implants involving bone or soft tissue augmentation. However, implants based in avascular and microvascular transplants showed higher rates of peri-implant inflammation.

CLINICAL RELEVANCE

Peri-implant perfusion seems to be comparable for all implants after they heal, irrespective of their bony surroundings. Although perfusion does not differ significantly, other factors may make implants in avascular and microvascular transplants vulnerable to peri-implant inflammation.

Evaluation of perfusion parameters of gingival inflammation using laser Doppler flowmetry and tissue spectrophotometry- a prospective comparative clinical study

BACKGROUND

The aim of this study was to determine the values of different perfusion parameters- such as oxygen saturation, the relative amount of hemoglobin, and blood flow- in healthy subjects compared to patients with gingivitis as a non-invasive measurement method.

METHODS

A total of 114 subjects were enrolled in this study and separated into subjects with gingivitis (50) and without gingivitis (64) based on clinical examination. Gingival perfusion was measured at 22 points in the maxilla and mandible using laser Doppler flowmetry and tissue spectrophotometry (LDF-TS) with the "oxygen to see" device. All patients underwent measurement of gingival perfusion, followed by the clinical evaluation (measurement of probing depths, evaluation of bleeding on probing, plaque level, and biotype). Perfusion parameters were compared between the groups, associations between the non-invasive and clinical measurements were analyzed, and theoretical optimal cut-off values for predicting gingivitis were calculated with receiver operating characteristics.

RESULTS

The mean oxygen saturation, mean relative amount of hemoglobin, and mean blood flow all significantly differed between the groups with and without gingivitis (p = 0.005, p < 0.001, and p < 0.001, respectively). The cut-off value for predicting gingivitis was > 40 AU (p < 0.001; sensitivity 0.90, specificity 0.67).

CONCLUSIONS

As a non-invasive method, LDF-TS can help determine gingival hyperemia. Flow values above 40 AU indicate a higher risk of hyperemia, which can be associated with inflammation. The LDF-TS method can be used for the objective evaluation of perfusion parameters during routine examinations and can signal the progression of hyperperfusion before any change in clinical parameters is observed.

TRIAL REGISTRATION

All procedures performed in this study involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. The study was approved by the institutional Clinical Research Ethics Committee (Ethik-Kommission der Medizinischen Fakultät der RWTH Aachen, Decision Number 286/20) and retrospectively registered by the German Clinical Trials Register (File Number DRKS00024048, registered on the 15th of October 2021).

Recipient bed perfusion as a predictor for postoperative complications in irradiated patients with microvascular free tissue transfer of the head and neck area: a clinical analysis of 191 microvascular free flaps

PURPOSE

Despite microvascular free tissue transfer being the mainstay of care in the reconstruction of larger maxillofacial defects, a significant number of patients experience postoperative complications due to impaired blood supply of the flap. In this context, the early influence of recipient bed perfusion remains unclear, but there is evidence that it is associated with free flap viability immediately after surgery.

METHODS

We analyzed flap and recipient bed perfusion within the first 2 weeks after surgery by using the oxygen-to-see device. One hundred ninety-one patients who underwent free flap surgery in our department were included.

RESULTS

Flow parameters were higher and postoperative complications were less frequent in radial forearm free flaps compared to any other type of flap. Flow parameters of the recipient bed were higher than transferred tissue at all times, implicating flap autonomization is not completed within 2 weeks. Previous radiotherapy significantly decreased flow parameters of the recipient bed but not of the flaps. Furthermore, irradiated patients with postoperative complications were found to have reduced flow parameters of their recipient bed compared to non-irradiated patients with postoperative complications.

CONCLUSION

We conclude that monitoring of recipient bed perfusion is useful for detecting flap compromise of irradiated patients in the early postoperative period.

Evaluation of a Novel System for Hypothermic Oxygenated Pulsatile Perfusion Preservation

Background

Recently, a novel innovative machine perfusion (MP) system for hypothermic oxygenated pulsatile perfusion called the Airdrive (AD) has been developed. The aim of the study was to evaluate the biological safety of the AD system for perfusion preservation of kidney grafts in a porcine autotransplantation model using the low-viscosity perfusion solution Polysol (PS) in comparison with cold storage (CS) using PS or the University of Wisconsin solution (UW). In addition, we evaluated real-time microcirculation parameters. At sacrifice, grafts were retrieved for histological analysis and immunohistochemistry

Methods

After assessment of the microcirculation, left kidneys were retrieved. Following the washout, kidneys were preserved for 20 hr using AD-PS, CS-PS or CS-UW. Thereafter, contralateral kidneys were removed followed by heterotopic autotransplantation of the preserved graft. Seven days after transplantation animals were sacrificed with retrieval of the grafts for histological analysis. Renal function, renal microcirculation and tissue injury including the proliferative response of tubular epithelial cells (TECs) were compared.

Results

Preservation using AD-PS or CS-PS resulted in higher microcirculatory flow compared with CS-UW. Improved recovery of renal function was seen in the AD-PS and CS-PS groups compared with CS-UW. Structural integrity was better preserved using AD-PS compared with both CS groups. Proliferative response of TECs was higher in CS-UW preserved grafts compared to grafts preserved using AD-PS.

Conclusion

This study demonstrates the biological safety of the AD system in a porcine autotransplantation model. Also, the microcirculation was better preserved and less morphological injury was observed after 20 hr MP compared with CS.

Argon and helium plasma coagulation of porcine liver tissue

Objective

Argon plasma coagulation (APC) and helium plasma coagulation (HPC) are electrosurgical techniques that provide noncontact monopolar electrothermal haemostasis. Although these techniques have been widely used clinically during the last three decades, their in vivo effects on liver tissue remain unclear.

Methods

We investigated the effects of different power levels (10–100 W) of APC and HPC on liver coagulation in 11 Landrace pigs. Capillary blood flow and capillary blood flow velocity were recorded with a combined laser Doppler flowmeter and spectrophotometer. The temperature, clinical biochemical parameters, blood gas parameters, bile duct-sealing effect, and coagulation depth were measured.

Results

APC and HPC significantly reduced the capillary blood flow and capillary blood flow velocity compared with baseline flow. No significant temperature change was measured on the liver surface immediately after coagulation. The clinical biochemical and blood gas parameters were not different before and after coagulation. The coagulation depth was positively correlated with the device power setting.

Conclusions

These results prove that APC and HPC provide sufficient superficial haemostasis. No significant systemic effects occurred following coagulation. The depth of the coagulation effect can be controlled through selection of the output power level.

Impact of radiotherapy on microsurgical reconstruction of the head and neck

PURPOSE

To examine tissue oxygenation and perfusion of free microvascular grafts after primary reconstruction, regarding outcome for patients received adjuvant radiotherapy and different types of grafts.

PATIENTS AND METHODS

Free microvascular grafts (n = 48) after primary reconstruction of the head and neck were examined for tissue oxygenation and perfusion over a period of 6 months. 28 patients received adjuvant radiotherapy. Using a laser doppler flowmetry combined with tissue spectroscopy of the Oxygen-to-see(®)--equipment (LEA Medizintechnik, Giessen), we were able to determine oxygen saturation, hemoglobin concentration, blood flow and blood flow velocity in the graft in each of two tissue depths (2, 8 mm). Different types of graft were compared.

RESULT

Comparison of irradiated and non-irradiated grafts showed significant differences in tissue perfusion and oxygenation. Results for all radiated radial and fibula flaps showed no significant (p > 0.05) differences for all reviewed parameters. However, it showed no dose-volume effect with impaired functionality was found for irradiated grafts.

CONCLUSION

Mircovascular free tissue grafts show an increased perfusion and oxygenation after radiation compared to non-irradiated grafts.

Physiological influence of basic perturbations assessed by non-invasive optical techniques in humans

New non-invasive techniques enabling frequent or continuous assessments of various pathophysiological conditions might be used to improve in-hospital outcome by enabling earlier and more reliable bedside detection of medical deterioration. In this preclinical study, three modern non-invasive optical techniques, laser Doppler imaging (LDI), near-infrared spectroscopy (NIRS), and tissue viability imaging (TVI), were all evaluated with respect to the influence of basic physiological perturbations (including local changes in arm positioning, skin temperature, and regional blood flow conditions) on quasi simultaneously obtained values of skin perfusion, muscle tissue oxygenation (StO2), and skin blood volume, recorded in eighteen healthy volunteers. Skin perfusion measured by LDI responded prominently to changes in positioning of the arm, whereas muscle StO2 measured by NIRS did not change significantly. Total haemoglobin count (HbT) measured by NIRS and blood volume estimated by TVI both increased significantly on lowering of the limb. On local cooling, the perfusion and blood volume were both found to increase considerably, while StO2 and HbT did not change. Local heating induced a more than 10-fold increase in skin perfusion and a small increase in blood volume. On progressive venoarterial occlusion, the perfusion, StO2, HbT, and blood volume values decreased, after transient increases in HbT and blood volume before full arterial occlusion occurred, and all values approached the baseline level on release of the occlusion with a slight overshoot of the StO2. The results obtained have potential bearing on future utilization of these non-invasive techniques in the management of severely injured and (or) critically ill patients.

Palmar microcirculation does not deteriorate 2 years after radial artery harvesting—implications for reconstructive free forearm flap transfer

BACKGROUND

The functional consequences after radial artery-based forearm flaps for hand microcirculation remain unclear. We hypothesized that palmar microcirculation is compromised after radial artery removal in arteriosclerotic patients.

MATERIALS AND METHODS

A total number of 114 patients were included undergoing elective coronary revascularization using the radial artery of the nondominant forearm with non-pathological Allen's test. Palmar microcirculatory mapping with 1596 measurements was applied 2 years after removal of the radial artery regarding capillary flow, finger tip oxygenation, as well as postcapillary venous filling pressures throughout both hands using combined noninvasive real-time laser Doppler flowmetry and spectrophotometry.

RESULTS

Only 2/56 positions revealed a difference beyond a 5% threshold 25 +/- 5 months after radial artery removal. Superficial capillary blood flow decreased by 13% at the hypothenar eminence (242.0 +/- 153.6 vs 275.6 +/- 169.2, p = 0.009). Deep postcapillary venous filling pressure (8 mm) was significantly increased by 9% only at the fingertip of the fifth finger (112.4 +/- 49.7 vs 103.0 +/- 25.0, p = 0.033). No clinical signs of malperfusion were found after radial artery removal, and no patient was impaired in his daily palmar motor activity.

CONCLUSIONS

Pedicled removal of the radial artery does not compromise superficial or deep palmar capillary blood flow, finger tip oxygenation, or postcapillary venous filling pressures in a long-term perspective in arteriosclerotic patients. No clinical relevant signs of malperfusion or any deterioration of palmar motor function was encountered. The blood flow via the ulnar artery and the interosseal artery compensates palmar perfusion without microcirculatory deterioration even more than 2 years after removal of the radial artery.