Medizinische Universität Graz Austria/Österreich - Forschungsportal - Medical University of Graz
Gewählte Publikation:
Heschl, S.
The influence of diabetic neuropathy on current settings during peripheral nerve stimulation for popliteal sciatic nerve block
Doktoratsstudium der Medizinischen Wissenschaft; Humanmedizin; [ Dissertation ] ; 2015. pp.
[OPEN ACCESS]
FullText
- Autor*innen der Med Uni Graz:
- Heschl Stefan
- Betreuer*innen:
- Gemes Geza
- Kresse Adelheid
- Rigaud Marcel
- Altmetrics:
- Abstract:
- Background Peripheral nerve stimulation (PNS) is a common technique for nerve localization in regional anesthesia, but the generally recommended stimulation threshold of 0.3-0.5mA does not reliably produce distal motor response in the absence of potentially harmful, intraneural needle placement. Since this may be particularly true in patients with diabetic neuropathy, this study examined the relationship of motor activity threshold and needle location at both branches of the sciatic nerve in patients with and without diabetic neuropathy. Methods Preoperative evaluation included a detailed neurological exam, laboratory testing and electroneurography. During ultrasound (US) guided popliteal sciatic nerve block, the current required to produce distal motor activity for the tibial nerve (TN) and common peroneal nerve (CPN) in diabetic and non-diabetic patients was measured. Proximity of the needle to the nerve was evaluated post-hoc using US imaging. Results Average stimulation currents did not differ between diabetic patients (n=55) and non-diabetic patients (n=52). Subjects with diminished pressure perception showed increased threshold for the CPN (median 1.30mA vs. 0.57mA in subjects with normal perception, p=0.042), as did subjects with decreased pain sensation (1.60mA vs. 0.50mA in subjects with normal pain sensation, p=0.038). Reduced ulnar nerve conduction velocity predicted elevated mean stimulation current (r=-0.35, p=0.002). Finally, 15 diabetic patients required more than 0.5mA to evoke a motor distal response despite unintentional, intraneural needle placement (n=4) or required current =2mA despite needle-nerve contact, versus 3 such patients (1 intraneural, 2 with =2mA) among non-diabetic patients (p=0.003). Discussion The diagnosis of diabetes mellitus per se did not alter the required stimulation thresholds for PNS. Patients with clinically evident signs of neuropathy, however, required substantially increased stimulation currents to elicit a motor response. Stimulation currents showed a high degree of variability for both diabetic patients and healthy controls and stimulation currents >0.5mA, the currently recommended threshold, were frequently observed. Diabetic patients are at significantly higher risk of potential intraneural needle positioning if PNS is used as the sole method of nerve localization. Simple clinical tests could help identifying patients who require increased stimulation thresholds. Conclusions These findings suggest that stimulation thresholds of 0.3-0.5mA may not reliably determine close needle-nerve contact during popliteal sciatic nerve block, particularly in patients with neuronal dysfunction due to diabetes mellitus.