Peripheral-central interplay for fatiguing unresisted repetitive movements: a study using muscle ischaemia and M1 neuromodulation

Maximal-rate rhythmic repetitive movements cannot be sustained for very long, even if unresisted. Peripheral and central mechanisms of fatigue, such as the slowing of muscle relaxation and an increase in M1-GABAb inhibition, act alongside the reduction of maximal execution rates. However, maximal muscle force appears unaffected, and it is unknown whether the increased excitability of M1 GABAergic interneurons is an adaptation to the waning of muscle contractility in these movements. Here, we observed increased M1 GABAb inhibition at the end of 30 s of a maximal-rate finger-tapping (FT) task that caused fatigue and muscle slowdown in a sample of 19 healthy participants. The former recovered a few seconds after FT ended, regardless of whether muscle ischaemia was used to keep the muscle slowed down. Therefore, the increased excitability of M1-GABAb circuits does not appear to be mediated by afferent feedback from the muscle. In the same subjects, continuous (inhibitory) and intermittent (excitatory) theta-burst stimulation (TBS) was used to modulate M1 excitability and to understand the underlying central mechanisms within the motor cortex. The effect produced by TBS on M1 excitability did not affect FT performance. We conclude that fatigue during brief, maximal-rate unresisted repetitive movements has supraspinal components, with origins upstream of the motor cortex.

A serious complication after forearm replantation caused by a cord tightened on the stump during transportation – a case report

In amputations of an upper extremity, an adequate preservation of the amputated part during its transport to a replantation centre is very important: it needs to be maintained at about 4°C. Providing adequate haemostasis of the extremity stump is also important for the patient’s safety, to avoid bleeding on the journey. The article presents the case of a patient who had sustained a hand amputation at the forearm, in which bleeding from the stump was stopped with a cord that has been tightened on the forearm, 10 cm above the amputation site. Transport for the patient took over 6 h and resulted in a critical ischaemia ofthe forearm stump. Replantation was successfully performed, but an excessive oedema of the ischaemically injured part of the stump developed in the post-operative course, requiring a fasciotomy, resection of the necrotic muscles, following by coverage of the defects with skin grafts. No complications were observed in the replanted part of the forearm, and the prognosis towards recovery of good hand function is moderate, due to the loss of a portion of the forearm muscles.Keywords: hand replantation; postoperative complications; muscle ischaemia; malpractice.

Demonstration of the temporal evolution of serum markers of skeletal muscle ischaemia reperfusion injury - An observational clinical study.

Objective The study aimed to investigate the temporal evolution of markers of skeletal muscle ischaemia reperfusion injury (IRI) to shed more light into its pathogenesis towards finding a clinical therapeutic intervention. P-selectin, Myeloperoxidase and TNF-alpha were selected as markers of IRI based on their role in its pathogenesis. An observational study was conducted on patients with skeletal muscle ischaemia requiring revascularization. Loco-regional venous sampling was performed at 0, +2, +4, +6, +12 and +24 hours post-reperfusion to demonstrate the temporal evolution of surrogate markers of IRI.Results Levels of P-Selectin, Myeloperoxidase and TNF-alpha demonstrated a significant peak elevation during 2h - 4h following reperfusion when compared to baseline values. (P-selectin 59.48pg/ml to 125.91pg/ml, p=0.008; Myeloperoxidase 78.84pg/ml to 116.86pg/ml, p=0.051; TNF-alpha 1.80pg/ml to 34.53pg/ml, p=0.002) All three markers gradually subsided with time and reached baseline pre-perfusion values between 6h – 8h from time of reperfusion. The study suggests that skeletal muscle IRI in humans is associated with an early exaggerated pro-inflammatory response, as supported by increased expression of reperfusion injury markers in the venous effluent. They demonstrate potential for use as markers of IRI for future clinical trials.

Successful Reduction of Creatine Kinase and Myoglobin Levels in Severe Rhabdomyolysis Using Extracorporeal Blood Purification (CytoSorb®)

Rhabdomyolysis, if severe, can lead to acute kidney injury (AKI). Myoglobin is an iron and oxygen-binding protein that is freely filtered by the glomerulus. Precipitation of myoglobin in the nephrons’ distal parts is responsible for tubular damage with AKI as a consequence. Extracorporeal clearance of myoglobin is conventionally attempted by the use of continuous renal replacement therapy (CRRT) with high cut-off dialysis membranes to limit the extent of the damage. We describe a case of a 56-year-old man with traumatic crush injury and a persistent source of muscle ischaemia unresponsive to high dose CRRT with EMiC-2 filter. Due to therapy failure, he was subsequently treated with the addition of a haemoadsorber (CytoSorb®) to the circuit. This reduced myoglobin and creatine kinase levels successfully despite ongoing tissue ischaemia. However, CytoSorb® was not enough to maintain microcirculatory perfusion, resulting in the eventual demise of the patient due to severity of the injury. Our report indicates that myoglobin was efficiently removed with CytoSorb® following exchange with the conventional high cut-off filter in continuous venovenous haemodialysis in severe traumatic rhabdomyolysis.