Reduction of experimental intracranial hypertension by lidocaine

Vascular air embolism: A silent hazard to patient safety

PURPOSE

To narratively review published information on prevention, detection, pathophysiology, and appropriate treatment of vascular air embolism (VAE).

MATERIALS AND METHODS

MEDLINE, SCOPUS, Cochrane Central Register and Google Scholar databases were searched for data published through October 2016. The Manufacturer and User Facility Device Experience (MAUDE) database was queried for "air embolism" reports (years 2011-2016).

RESULTS

VAE may be introduced through disruption in the integrity of the venous circulation that occurs during insertion, maintenance, or removal of intravenous or central venous catheters. VAE impacts pulmonary circulation, respiratory and cardiac function, systemic inflammation and coagulation, often with serious or fatal consequences. When VAE enters arterial circulation, air emboli affect cerebral blood flow and the central nervous system. New medical devices remove air from intravenous infusions. Early recognition and treatment reduce the clinical sequelae of VAE. An organized team approach to treatment including clinical simulation can facilitate preparedness for VAE. The MAUDE database included 416 injuries and 95 fatalities from VAE. Data from the American Society of Anesthesiologists Closed Claims Project showed 100% of claims for VAE resulted in a median payment of $325,000.

CONCLUSIONS

VAE is an important and underappreciated complication of surgery, anesthesia and medical procedures.

Animal models of cerebral arterial gas embolism

Cerebral arterial gas embolism is a dreaded complication of diving and invasive medical procedures. Many different animal models have been used in research on cerebral arterial gas embolism. This review provides an overview of the most important characteristics of these animal models. The properties discussed are species, cerebrovascular anatomy, method of air embolization, amount of air, bubble size, outcome parameters, anesthesia, blood glucose, body temperature and blood pressure.

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.

Intravenous lidocaine as adjunctive therapy in the treatment of decompression illness

Two cases of severe decompression illness for which IV lidocaine was used as adjunctive therapy to recompression and hyperbaric oxygen therapy are described. The first patient demonstrated improvement only after lidocaine was added to her treatment; the second had essentially complete recovery after only a single treatment despite severe symptoms and a significant delay in presentation. These cases support the need for a controlled clinical trial of lidocaine as an adjunct to hyperbaric therapy in decompress on illness.

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

1. Lidocaine has been extensively investigated as a potential neuroprotective drug against ischemia-induced neurodegeneration without reaching any satisfactory conclusion. 2. The present work evaluates the effect of lidocaine -17 microM- on the hypoxia-induced release of tritiated D-aspartate from rat striatal slices in superfusion. 3. Hypoxia resulted in a significant increase in the amount of D-aspartate released from striatal slices preloaded with the tritiated excitatory amino acid analog. 4. The addition of lidocaine to the superfusion solution resulted in a drastic reduction in the amount of D-aspartate release evoked by hypoxia, rendering it close to normal values.

Prophylactic lidocaine use preintubation: a review

This article is a review of the use of prophylactic lidocaine as a preintubation medication. Intubation is associated with a cardiovascular response of elevated blood pressure and pulse, cough reflexes, occasional dysrhythmias, increased intracranial pressure, and increased intraocular pressure. In patients with atherosclerotic heart disease, potential intracranial lesions, and potential penetrating eye injuries, these responses to intubation are of greater risk. Various studies have reviewed the effect of lidocaine to blunt these responses. It is agreed that lidocaine blunts cough reflexes and dysrhythmias. Some studies note a response of lidocaine in blunting rises in pulse, blood pressure, intracranial and intraocular pressure. No studies document any harmful effects of prophylactic lidocaine given preintubation. A dose of prophylactic lidocaine of 1.5 mg/kg given intravenously 3 minutes before intubation is optimal. For suctioning of intubated patients, lidocaine can be given endotracheally in a 5-6 mg/kg dose diluted in 6 cc via simple administration at the entrance to the endotracheal tube.

Brain protection: physiological and pharmacological considerations. Part II: The pharmacology of brain protection

Neuroprotective agents may exert their effect by reducing cerebral oxygen demand (CMRO2), increasing cerebral oxygen delivery, or by altering ongoing pathological processes. Barbiturates provide neuroprotection by reducing the CMRO2 necessary for synaptic transmission while leaving the component necessary for cellular metabolism intact. Isoflurane may exert a neuroprotective effect by a similar mechanism but its efficacy is likely less than that of barbiturates due to adverse effects on cerebral blood flow. Lidocaine reduces CMRO2 by affecting both cellular metabolic processes and synaptic transmission and thus resembles hypothermia in its mechanism of action. Benzodiazepines reduce CMRO2 by reducing synaptic transmission and their use as neuroprotectants produces less haemodynamic compromise than barbiturates. The mechanism of protection by calcium entry blocking agents appears to be due to improved blood flow as opposed to altering abnormal Ca++ fluxes. In contrast, agents such as ketamine and MK-801 may prevent abnormal Ca++ fluxes through their competitive interaction with N-methyl-D-aspartate receptors. Phenytoin prevents K(+)-mediated ischaemic events from progressing. Agents worthy of further investigation include corticosteroids, free radical scavengers, prostaglandin inhibitors and iron chelators.

Effect of lidocaine after experimental cerebral ischemia induced by air embolism

To investigate possible approaches to the treatment of neural damage induced by air embolism and other forms of acute cerebral ischemia, somatosensory evoked potentials (SEP's) were measured after cerebral air embolism in the anesthetized cat. Air was introduced into the carotid artery in increments of 0.08 ml until the SEP amplitude was reduced to approximately 10% or less of baseline values. Either a saline or lidocaine infusion was begun 5 minutes after inducing cerebral ischemia. In the saline-treated group, SEP amplitude was reduced to 6.7% +/- 1.6% (mean +/- standard error of the mean) of baseline, with a return to 32.6% +/- 4.7% of baseline over a 2-hour period. In the lidocaine-treated group, SEP amplitude was reduced to 5.9% +/- 1.5%, with a return to 77.3% +/- 6.2% over a 2-hour period. The results suggest that lidocaine administration facilitates the return of neural function after acute cerebral ischemia induced by air embolism.