Diabetic Peripheral Neuropathy Increases Electrical Stimulation Threshold of Sciatic Nerve: A Prospective Parallel Cohort Study.

PURPOSE: To investigate the impact of diabetic peripheral neuropathy and its severity on the threshold of sciatic nerve electrical stimulation in diabetic patients. PATIENTS AND METHODS: The case-control study included 60 patients that were divided into non-diabetic patients (control group, n = 26) and diabetic patients (diabetes group, n = 34). All the patients who were scheduled for lower leg, foot, and ankle surgery received a popliteal sciatic nerve block. We recorded the minimum current required to produce motor activity of the sciatic nerve during ultrasound-guided popliteal sciatic nerve block. RESULTS: Among the 60 patients, the sciatic nerve innervated muscle contractile response was successfully elicited in 57 patients (dorsiflexion of foot, plantar flexion, foot valgus or adduction, toe flexion, etc.) under electric stimulation. We failed to elicit the motor response in three patients with diabetic peripheral neuropathy, even when the stimulation current was 3 mA. The average electrical stimulation threshold (1.0 ± 0.7 mA) in the diabetes group was significantly higher than that of the control group (0.4 ± 0.1 mA). Diabetic patients with peripheral neuropathy had a higher electrical stimulation threshold (1.2 ± 0.7 mA) than patients without peripheral neuropathy (0.4 ± 0.1 mA). Furthermore, the electrical stimulation threshold of the sciatic nerve in diabetic patients had a linear dependence on the Toronto Clinical Scoring System (TCSS) peripheral neuropathy score (electrical stimulation threshold [in mA] = 0.125 TCSS score) (P < 0.001). CONCLUSION: The threshold of electrical stimulation to elicit a motor response of the sciatic nerve was increased in diabetic patients, and the threshold of electrical stimulation of the sciatic nerve increased with the severity of diabetic nerve dysfunction.

Dose-dependent neurotoxicity caused by the addition of perineural dexmedetomidine to ropivacaine for continuous femoral nerve block in rabbits.

OBJECTIVE: This study was designed to evaluate the neurotoxicity of dexmedetomidine combined with ropivacaine for continuous femoral nerve block in rabbits. METHODS: Thirty New Zealand rabbits were randomly divided into 5 groups of 6 rabbits each and received a continuous femoral nerve block with saline; 0.25% ropivacaine; or 1, 2, or 3 µg/mL of dexmedetomidine added to 0.25% ropivacaine (Groups A-E, respectively). Sensory and motor function was assessed after the nerve block. The rabbits were anesthetized and killed after 48 hours of a continuous femoral nerve block, and the femoral nerves were removed for light and electron microscopy analyses. RESULTS: The behavior scores were highest in Group A at 2 and 6 hours after injection. The scores were higher in Groups B and C than in Groups D and E at these same time points. All groups showed normal pathological tissues in the femoral nerves under optical microscopy. Under electron microscopy, histological abnormalities were observed only in Group E; none of the other groups exhibited pathological abnormalities. Quantitative analysis of the myelin sheath area revealed no significant difference in the axonal area, total area of the myelin sheath, or ratio of the total axonal area to the total area of the myelin sheath in all groups. CONCLUSION: The lowest doses of dexmedetomidine (1 and 2 µg/mL) combined with 0.25% ropivacaine for continuous femoral nerve block resulted in no neurotoxic lesions, but the higher dose (3 µg/mL) resulted in neurotoxic lesions in this rabbit experimental model.

Optimal central venous pressure during partial hepatectomy for hepatocellular carcinoma.

BACKGROUND: Low central venous pressure (CVP) affects hemodynamic stability and tissue perfusion. This prospective study aimed to evaluate the optimal CVP during partial hepatectomy for hepatocellular carcinoma (HCC). METHODS: Ninety-seven patients who underwent partial hepatectomy for HCC had their CVP controlled at a level of 0 to 5 mmHg during hepatic parenchymal transection. The systolic blood pressure (SBP) was maintained, if possible, at 90 mmHg or higher. Hepatitis B surface antigen was positive in 90 patients (92.8%) and cirrhosis in 84 patients (86.6%). Pringle maneuver was used routinely in these patients with clamp/unclamp cycles of 15/5 minutes. The average clamp time was 21.4+/-8.0 minutes. These patients were divided into 5 groups based on the CVP: group A: 0-1 mmHg; B: 1.1-2 mmHg; C: 2.1-3 mmHg; D: 3.1-4 mmHg and E: 4.1-5 mmHg. The blood loss per transection area during hepatic parenchymal transection and the arterial blood gas before and after liver transection were analyzed. RESULTS: With active fluid load, a constant SBP ≥90 mmHg which was considered as optimal was maintained in 18.6% in group A (95% CI: 10.8%-26.3%); 39.2% in group B (95% CI: 29.5%-48.9%); 72.2% in group C (95% CI: 63.2%-81.1%); 89.7% in group D (95% CI: 83.6%-95.7%); and 100% in group E (95% CI: 100%-100%). The blood loss per transection area during hepatic parenchymal transection decreased with a decrease in CVP. Compared to groups D and E, blood loss in groups A, B and C was significantly less (analysis of variance test, P<0.05). Compared with the baseline, the blood oxygenation decreased significantly when the CVP was reduced. Base excess and HCO3- in groups A and B were significantly decreased compared with those in groups C, D and E (P<0.05). CONCLUSION: In consideration of blood loss, SBP, base excess and HCO3-, a CVP of 2.1-3 mmHg was optimal in patients undergoing partial hepatectomy for HCC.

Hemodynamics and oxygen transport dynamics during hepatic resection at different central venous pressures in a pig model.

BACKGROUND: Although low central venous pressure (CVP) has been used to minimize blood loss during hepatectomy, the impact of variations of CVP on the rate of blood loss and on the perfusion of end-organs has not been evaluated. This animal study aimed to evaluate the hemodynamics and oxygen transport changes during hepatic resection at different CVP levels. METHODS: Forty-eight anesthetized Bama miniature pigs were divided into 8 groups with CVP during hepatic resection controlled at 0 to <1, 1 to <2, 2 to <3, 3 to <4, 4 to <5, 5 to <6, 6 to <7, and 7 to <8 cmH2O. Intergroup comparisons were made for hemodynamic parameters, oxygen transport dynamics, and the rate of blood loss. RESULTS: The rate of blood loss and the hepatic venous pressure during hepatic resection were almost linearly related to the CVP. A significant drop in the mean arterial pressure, cardiac output, and cardiac index occurred between CVP ≥2 and <2 cmH2O. Oxygen delivery (DO2), oxygen consumption (VO2) and oxygen extraction ratio (ERO2) remained relatively constant between CVPs of 2 to <8 cmH2O. There was a significant drop in DO2 when the CVP was <2 cmH2O. There was also a significant drop in VO2 and ExO2 when the CVP was <1 cmH2O. CONCLUSION: The optimal CVP for hepatic resection is 2 to 3 cmH2O.