Muscle Oxygenation Level Might Trigger the Regulation of Capillary Venous Blood Filling during Fatiguing Isometric Muscle Actions

Characteristics and Limitations of Video-capillaroscopy in Reconstructive Microsurgery for Different Histologic Components of Flaps

Indocyanine green, ultrasonography, and handheld Doppler can be used to evaluate blood flow at the donor and recipient site during microvascular reconstruction. However, these methods do not provide direct visualization and assessment of real-time blood flow. Video-capillaroscopy has been shown to be useful in clinical practice to assess microcirculation in rheumatologic disorders. In this report we used video-capillaroscopy to assess different tissue components involved in microvascular surgery. Seven patients who underwent head and neck oncologic microvascular reconstruction between November 2021 and February 2022 were included in this study. Video-capillaroscopy (GOKO-BscanZD, GOKO Imaging Devices Co., Ltd., Japan) was used to evaluate the donor-site and recipient-site tissue components. Optimal red blood cell movement was graded with a score of four, while no flow was graded with a score of 0. Seven myocutaneous flaps and seven recipient sites were evaluated. For the donor-site, our analysis demonstrated a significantly higher video-capillaroscopy quality for skin (3.43), adipose tissue (3.7) and perforators (3.7) when compared with muscle (0.429), muscle fascia (0.857), and de-epithelialized skin (1) (P < 0.001). For the recipient-site, a significantly higher video-capillaroscopy quality for skin (2.7), adipose tissue (3.5), and the periosteum (2.1) was noted when compared with muscle (0) (P < 0.001). Video-capillaroscopy efficiency is limited in the muscular component and injured (de-epithelialized) skin surface areas of flaps. Herein, we provide evidence that assessment of flap perfusion with video-capillaroscopy can be reliably achieved in the skin, periosteum, perforators, and adipose tissue. Video-capillaroscopy is expected to be applied for intraoperative real-time blood flow evaluation.

Muscle oxygenation and time to task failure of submaximal holding and pulling isometric muscle actions and influence of intermittent voluntary muscle twitches

Background

Isometric muscle actions can be performed either by initiating the action, e.g., pulling on an immovable resistance (PIMA), or by reacting to an external load, e.g., holding a weight (HIMA). In the present study, it was mainly examined if these modalities could be differentiated by oxygenation variables as well as by time to task failure (TTF). Furthermore, it was analyzed if variables are changed by intermittent voluntary muscle twitches during weight holding (Twitch). It was assumed that twitches during a weight holding task change the character of the isometric muscle action from reacting (≙ HIMA) to acting (≙ PIMA).

Methods

Twelve subjects (two drop outs) randomly performed two tasks (HIMA vs. PIMA or HIMA vs. Twitch, n = 5 each) with the elbow flexors at 60% of maximal torque maintained until muscle failure with each arm. Local capillary venous oxygen saturation (SvO₂) and relative hemoglobin amount (rHb) were measured by light spectrometry.

Results

Within subjects, no significant differences were found between tasks regarding the behavior of SvO₂ and rHb, the slope and extent of deoxygenation (max. SvO₂ decrease), SvO₂ level at global rHb minimum, and time to SvO₂ steady states. The TTF was significantly longer during Twitch and PIMA (incl. Twitch) compared to HIMA (p = 0.043 and 0.047, respectively). There was no substantial correlation between TTF and maximal deoxygenation independently of the task (r = − 0.13).

Conclusions

HIMA and PIMA seem to have a similar microvascular oxygen and blood supply. The supply might be sufficient, which is expressed by homeostatic steady states of SvO₂ in all trials and increases in rHb in most of the trials. Intermittent voluntary muscle twitches might not serve as a further support but extend the TTF. A changed neuromuscular control is discussed as possible explanation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13102-022-00447-9.