Lidocaine reduces the hypoxia-induced release of an excitatory amino acid analog from rat striatal slices in superfusion

Intravenous Lidocaine Does Not Improve Neurologic Outcomes after Cardiac Surgery: A Randomized Controlled Trial

BACKGROUND

Cognitive decline after cardiac surgery occurs frequently and persists in a significant proportion of patients. Preclinical studies and human trials suggest that intravenous lidocaine may confer protection in the setting of neurologic injury. It was hypothesized that lidocaine administration would reduce cognitive decline after cardiac surgery compared to placebo.

METHODS

After institutional review board approval, 478 patients undergoing cardiac surgery were enrolled into this multicenter, prospective, randomized, double-blinded, placebo-controlled, parallel group trial. Subjects were randomized to lidocaine 1 mg/kg bolus after the induction of anesthesia followed by a continuous infusion (48 μg · kg · min for the first hour, 24 μg · kg · min for the second hour, and 10 μg · kg · min for the next 46 h) or saline with identical volume and rate changes to preserve blinding. Cognitive function was assessed preoperatively and at 6 weeks and 1 yr postoperatively using a standard neurocognitive test battery. The primary outcome was change in cognitive function between baseline and 6 weeks postoperatively, adjusting for age, years of education, baseline cognition, race, and procedure type.

RESULTS

Among the 420 allocated subjects who returned for 6-week follow-up (lidocaine: N = 211; placebo: N = 209), there was no difference in the continuous cognitive score change (adjusted mean difference [95% CI], 0.02 (-0.05, 0.08); P = 0.626). Cognitive deficit (greater than 1 SD decline in at least one cognitive domain) at 6 weeks occurred in 41% (87 of 211) in the lidocaine group versus 40% (83 of 209) in the placebo group (adjusted odds ratio [95% CI], 0.94 [0.63, 1.41]; P = 0.766). There were no differences in any quality of life outcomes between treatment groups. At the 1-yr follow-up, there continued to be no difference in cognitive score change, cognitive deficit, or quality of life.

CONCLUSIONS

Intravenous lidocaine administered during and after cardiac surgery did not reduce postoperative cognitive decline at 6 weeks.

Regionally infused lidocaine can dose-dependently protect the ischemic spinal cord in rabbits and may be associated with the EAA changes

OBJECTIVE

In our previous study, we found that lidocaine, infused through the abdominal aorta, could protect the spinal cord against the ischemia-reperfusion (I/R) injury caused by aortic occlusion. However, whether lidocaine protective effects have dose-dependent properties and its underlying mechanisms still remain unclear. This study was designed to investigate whether regionally infused lidocaine could dose-dependently protect spinal cord against I/R injury in rabbits and its underlying mechanism.

METHODS

46 New Zealand white rabbits were randomized into six groups: Group NS (normal saline control); Group L10 (lidocaine 10 mg/kg); Group L20 (lidocaine 20 mg/kg); Group L40 (lidocaine 40 mg/kg); Group L80 (lidocaine 80 mg/kg) and Group Sham. In Group NS, Group L10, Group L20, Group L40 and Group L80, spinal cord ischemia was induced by infrarenal aortic occlusion for 30 min. The sham group did not receive spinal cord ischemia. During the occlusion, normal saline or lidocaine at different doses was infused continuously through a catheter into the clamped abdominal aorta respectively. Neurologic behavior functions were assessed according to the Tarlov scale system at the moments of 0, 6, 24 and 48 h after reperfusion. The neural injuries were evaluated by the histological examination and the count of normal α-motor neurons in the ventral horn. The levels of excitatory amino acids (EAAs) in the spinal cord, including glutamate (Glu) and aspartic acid (Asp), were analyzed by high performance liquid chromatography with fluorescence detection.

RESULTS

The Tarlov scales in the Group L20 and the Group L40 were significantly higher than those in the Group NS at 24 and 48 h after reperfusion (P < 0.05). 12.5 % animals in Group L40 and 25 % animals in Group L20 were paraplegic versus 75 % animals in Group NS at 48 h after reperfusion (P < 0.05). The median of normal α-motor neurons in the L20, L40 and L80 groups was 7.5, 9 and 5 respectively which was significantly higher than in the NS group (count 0, P < 0.05). The levels of L-ASP and L-Glu remarkably decreased in the Group L10 and the Group L40 compared to Group NS (P < 0.05).

CONCLUSIONS

These data revealed that regional administration of lidocaine through the abdominal aorta can provide dose-dependent protection on spinal cord I/R in rabbits. Inhibition of EAA release may be one of the underlying mechanisms.

Effect of lidocaine on dynamic changes in cortical reduced nicotinamide adenine dinucleotide fluorescence during transient focal cerebral ischemia in rats

Rats were subjected to 90min of focal ischemia by occluding the left middle cerebral and both common carotid arteries. The dynamic changes in the formation of brain ischemic areas were analyzed by measuring the direct current (DC) potential and reduced nicotinamide adenine dinucleotide (NADH) fluorescence with ultraviolet irradiation. In the lidocaine group (n=10), 30min before ischemia, an intravenous bolus (1.5mg/kg) of lidocaine was administered, followed by a continuous infusion (2mg/kg/h) for 150min. In the control group (n=10), an equivalent amount of saline was administered. Following the initiation of ischemia, an area of high-intensity NADH fluorescence rapidly developed in the middle cerebral artery territory in both groups and the DC potential in this area showed ischemic depolarization. An increase in NADH fluorescence closely correlated with the DC depolarization. The blood flow in the marginal zone of both groups showed a similar decrease. Five minutes after the onset of ischemia, the area of high-intensity NADH fluorescence was significantly smaller in the lidocaine group (67% of the control; P=0.01). This was likely due to the suppression of ischemic depolarization by blockage of voltage-dependent sodium channels with lidocaine. Although lidocaine administration did not attenuate the number of peri-infarct depolarizations during ischemia, the high-intensity area and infarct volume were significantly smaller in the lidocaine group both at the end of ischemia (78% of the control; P=0.046) and 24h later (P=0.02). A logistic regression analysis demonstrated a relationship between the duration of ischemic depolarization and histologic damage and revealed that lidocaine administration did not attenuate neuronal damage when the duration of depolarization was identical. These findings indicate that the mechanism by which lidocaine decreases infarct volume is primarily through a reduction of the brain area undergoing NADH fluorescence increases which closely correlates with depolarization.

Randomized, double-blinded, placebo controlled study of neuroprotection with lidocaine in cardiac surgery

BACKGROUND AND PURPOSE

Cognitive decline after cardiac surgery remains common and diminishes patients' quality of life. Based on experimental and clinical evidence, this study assessed the potential of intravenously administered lidocaine to reduce postoperative cognitive dysfunction after cardiac surgery using cardiopulmonary bypass.

METHODS

After IRB approval, 277 patients undergoing cardiac surgery were enrolled into this prospective, randomized, double-blinded placebo controlled clinical trial. Subjects were randomized to receive: (1) Lidocaine as a 1 mg/kg bolus followed by a continuous infusion through 48 hours postoperatively, or (2) Placebo bolus and infusion. Cognitive function was assessed preoperatively and again at 6 weeks and 1 year postoperatively. The effect of lidocaine on postoperative cognition was tested using multivariable regression modeling; P<0.05 was considered significant.

RESULTS

Among the 241 allocated subjects (Lidocaine: n=114; Placebo: n=127), the incidence of cognitive deficit in the lidocaine group was 45.5% versus 45.7% in the placebo group (P=0.97). Multivariable analysis revealed a significant interaction between treatment group and diabetes, such that diabetic subjects receiving lidocaine were more likely to suffer cognitive decline (P=0.004). Secondary analysis identified total lidocaine dose (mg/kg) as a significant predictor of cognitive decline and also revealed a protective effect of lower dose lidocaine in nondiabetic subjects.

CONCLUSIONS

Lidocaine administered during and after cardiac surgery does not reduce the high rate of postoperative cognitive dysfunction. Higher doses of lidocaine and diabetic status were independent predictors of cognitive decline. Protective effects of lower dose lidocaine in nondiabetic subjects need to be further evaluated.