Skin perfusion and oxygen saturation after mastectomy and radiation therapy in breast cancer patients.

The pathophysiological mechanism behind complications associated with postmastectomy radiotherapy (PMRT) and subsequent implant-based breast reconstruction are not completely understood. The aim of this study was to examine if there is a relationship between PMRT and microvascular perfusion and saturation in the skin after mastectomy and assess if there is impaired responsiveness to a topically applied vasodilator (Methyl nicotinate - MN). Skin microvascular perfusion and oxygenation >2 years after PMRT were measured using white light diffuse reflectance spectroscopy (DRS) and laser Doppler flowmetry (LDF) in the irradiated chest wall of 31 women with the contralateral breast as a control. In the non-irradiated breast, the perfusion after application of MN (median 0.84, 25th-75th centile 0.59-1.02 % RBC × mm/s) was higher compared to the irradiated chest wall (median 0.51, 25th-75th centile 0.21-0.68 % RBC × mm/s, p < 0.001). The same phenomenon was noted for saturation (median 91 %, 25th-75th centile 89-94 % compared to 89 % 25th-75th centile 77-93 %, p = 0.001). Eight of the women (26%) had a ≥10 % difference in skin oxygenation between the non-irradiated breast and the irradiated chest wall. These results indicate that late microvascular changes caused by radiotherapy of the chest wall significantly affect skin perfusion and oxygenation.

Microcirculatory changes in the skin after postmastectomy radiotherapy in women with breast cancer.

Postmastectomy radiotherapy (PMRT) increases the risk for complications after breast reconstruction. The pathophysiological mechanism underlying this increased risk is not completely understood. The aim of this study was to examine if there is a relationship between PMRT and microvascular perfusion in the skin directly after, and at 2 and 6 months after PMRT and to assess if there is impaired responsiveness to a topically applied vasodilator (Methyl nicotinate-MN) after PMRT. Skin microvascular responses after PMRT were measured on two sites in the irradiated chest wall of 22 women before, immediately after, and at 2 and 6 months after unilateral PMRT with the contralateral breast as a control. A significant increase in basal skin perfusion was observed in the irradiated chest wall immediately after RT (p < 0.0001). At 2 and 6 months after RT, there was no longer a difference in basal skin perfusion compared to the contralateral breast and compared to baseline. Similarly, the blood flow response in the skin after application of MN was stronger immediately after RT compared to before RT (p < 0.0001), but there was no difference at later time points. These results indicate that the increased risk for complications after surgical procedures are not directly related to changes in skin perfusion and microvascular responsiveness observed after postmastectomy RT.

Correlation between Indocyanine Green Fluorescence Angiography and Laser Speckle Contrast Imaging in a Flap Model.

Background: Indocyanine green fluorescence angiography (ICG-FA) is used to assess tissue intraoperatively in reconstructive surgery. This requires an intra-venous dye injection for each assessment. This is not necessary in laser speckle contrast imaging (LSCI); therefore, this method may be better suited for tissue evaluation. To determine this, we compared the two methods in a porcine flap model. Methods: One random and one pedicled flap were raised on each buttock of six animals. They were assessed with LSCI at baseline, when raised (T0), at 30 minutes (T30) and with ICG-FA at T0 and T30. Regions of interest (ROI) were chosen along the flap axis. Perfusion, measured as perfusion units (PU) in the LSCI assessment and pixel-intensity for the ICG-FA video uptake, was calculated in the ROI. Correlation was calculated between PU and pixel-intensity measured as time to peak (TTP) and area under curve for 60 seconds (AUC60). Results: Correlation between LSCI and AUC60 for the ICG-FA in corresponding ROI could be seen in all flaps at all time points. The correlation was higher for T0 (r=0.7 for random flap and r=0.6 for pedicled flap) than for T30 (r=0.57 for random flap and r=0.59 for pedicled flap). Even higher correlation could be seen PU and TTP (T0: random flap r=-0.8 and pedicled flap r=0.76. T30: random flap r=-0.8 and pedicled flap r=0.71). Conclusion: There is a correlation between PU from LSCI and TTP and AUC60 for ICG-FA, indicating that LSCI could be considered for intraoperative tissue assessment.

Sympathetic and vagal interaction in the control of cardiac pacemaker rhythm in the guinea-pig heart: Importance of expressing heart rhythm using an appropriate metric.

There are many reports that, through pre- and post-junctional mechanisms, sympathetic and parasympathetic (vagal) nerves can interact in the control of heart rate. The predominant interaction is accentuated antagonism (AA), where the bradycardia produced by vagal stimulation (VNS) is amplified when heart rate has been increased by sympathetic stimulation (SNS) or beta-adrenergic agonists. The acetylcholine-activated potassium current (IK,Ach), is the primary driver of vagal bradycardia. To examine the participation of IK,Ach in AA, a series of experiments was performed on isolated, double innervated, guinea-pig atrial preparations. Vagal bradycardia was elicited by 10-s trains (1, 2, 5 and 7.5 Hz) or single bursts of VNS (3 stimuli at 50 Hz) before and during acceleration of HR by either SNS (1-3 Hz) or isoprenaline (ISO), in both absence and presence of tertiapin-Q (TQ-IK,Ach blocker). When expressed as an absolute change in HR (beats/min), bradycardia produced by VNS trains was amplified (AA) at all frequencies of VNS in ISO, and at 5 and 7.5 Hz during SNS. Bradycardia in response to 1 and 2 Hz VNS was reduced during SNS. In TQ, only the bradycardia produced by 5 and 7.5 Hz VNS in ISO was amplified. The bradycardia produced by a single burst of VNS was amplified in both ISO and SNS. After TQ the bradycardia in response to a VNS burst was unchanged in ISO, while it was reduced during SNS. When these data were adjusted to account for the increase in baseline HR brought about by SNS and ISO, there was no longer evidence of AA. Diminished responses to low frequencies of VNS (1 and 2 Hz) persisted, and were also seen during IK,Ach block by TQ. We applied the same adjustment to data from 20 published studies. In 8 studies all data indicated AA; 3 studies provided no evidence for AA, and in 9 studies evidence was mixed. There is no doubt that AA can occur in the control of heart rhythm during simultaneous SNS and VNS, but conditions which determine its occurrence, and the mechanisms involved in this interaction remain unclear.

Biosynthetic cellulose compared to porcine xenograft in the treatment of partial-thickness burns: A randomised clinical trial.

AIM: The aim was to compare two dressing treatments for partial-thickness burns: biosynthetic cellulose dressing (BsC) (Epiprotect® S2Medical AB, Linköping, Sweden) and porcine xenograft (EZ Derm®, Mölnlycke Health Care, Gothenburg, Sweden). METHODS: Twenty-four adults with partial-thickness burns were included in this randomized clinical trial conducted at The Burn Centers in Linköping and Uppsala, Sweden between June 2016 and November 2018. Time to healing was the primary outcome. Secondary outcomes were wound infection, pain, impact on everyday life, length of hospital stay, cost, and burn scar outcome (evaluated with POSAS). RESULTS: We found no significant differences between the two dressing groups regarding time to healing, wound infection, pain, impact on everyday life, duration of hospital stay, cost, or burn scar outcome at the first follow up. Burn scar outcome at the 12-month follow up showed that the porcine xenograft group patients scored their scars higher on the POSAS items thickness (p = 0.048) and relief (p = 0.050). This difference was, however, not confirmed by the observer. CONCLUSIONS: The results showed the dressings performed similarly when used in adults with burns evaluated as partial thickness.

Skin blood flow response to topically applied methyl nicotinate: Possible mechanisms.

BACKGROUND: Methyl nicotinate (MN) induces a local cutaneous erythema in the skin and may be valuable as a local provocation in the assessment of microcirculation and skin viability. The mechanisms through which MN mediates its vascular effect are not fully known. The aim of this study was to characterize the vasodilatory effects of topically applied MN and to study the involvement of nitric oxide (NO), local sensory nerves, and prostaglandin-mediated pathways. METHODS: MN was applied on the skin of healthy subjects in which NO-mediated (L-NMMA), nerve-mediated (lidocaine/prilocaine), and cyclooxygenase-mediated (NSAID) pathways were selectively inhibited. Microvascular responses in the skin were measured using laser speckle contrast imaging (LSCI). RESULTS: NSAID reduced the MN-induced perfusion increase with 82% (P < .01), whereas lidocaine/prilocaine reduced it with 32% (P < .01). L-NMMA did not affect the microvascular response to MN. CONCLUSION: The prostaglandin pathway and local sensory nerves are involved in the vasodilatory actions of MN in the skin.

The microvascular response in the skin to topical application of methyl nicotinate: Effect of concentration and variation between skin sites.

BACKGROUND: Methyl nicotinate (MN) induces a local cutaneous erythema in the skin and may be used as a local provocation in the assessment of microcirculation and skin viability. The aims were to measure the effects of increasing doses of MN, to find the concentration that yields the most reproducible effect from day to day and between sites, and to study the variation between skin sites. METHODS: Microvascular responses to topically applied MN at different concentrations were measured in 12 subjects on separate days and on contralateral sides, using laser speckle contrast imaging (LSCI). MN effects were measured in four different body sites. RESULTS: At 20 mmol/L, the response to MN was most reproducible day-to-day and site-to-site, and resulted in a plateau response between 5 and 20 min after application. The skin region of the lower back had a lower perfusion value compared to the epigastric region (p = 0.007). When responses were compared to nearby, unprovoked areas, a significantly larger increase in perfusion was seen in the forearm, compared to all other anatomical sites (p < 0.03). CONCLUSION: A concentration of 20 mmol/L MN generated the most reproducible microvascular response in the skin. The response varies between different body sites.

Intestinal obstruction following harvest of VRAM-flap for reconstruction of a large perineal defect.

A patient with locally advanced adenocarcinoma of the rectum was operated with abdominoperineal resection and perineal reconstruction with a vertical rectus abdominis musculocutaneous flap. Six days postoperatively, there was herniation of the small bowel, between the anterior and posterior rectus sheaths, to a subcutaneous location.