The effect of lidocaine on early postoperative cognitive dysfunction after coronary artery bypass surgery

Carbon Monoxide Research Group, LDS Hospital, Utah in reply to Scheinkestel et al. and Emerson: The role of hyperbaric oxygen in carbon monoxide poisoning

This comprehensive response was invited by the Editor of Emergency Medicine Australasia to allow our Group from Salt Lake City, Utah to review the two articles 'Where to now with carbon monoxide poisoning?' by Scheinkestel et al. and the accompanying

COMMENTARY

'The dilemma of managing carbon monoxide poisoning' by Emerson published in the April issue of Emergency Medicine Australasia.

Cognitive deficits following coronary artery bypass grafting: prevalence, prognosis, and therapeutic strategies

There is increasing recognition that coronary artery bypass grafting (CABG) may be a risk factor for subtle cognitive decline although the presence and pattern of such decline has varied across studies. Cognitive deficits may present as short-term memory loss, executive dysfunction and psychomotor slowing. Although they are usually are not severe enough to meet criteria for mild cognitive impairment or vascular dementia, they lower quality of life and add to hospitalization and out-of-hospital costs. Proposed mechanisms include surgical-related trauma, genetic susceptibility (eg, apolipoprotein E4 allele), microembolization, other vascular or ischemic changes, and temperature during surgery. Depression and anxiety levels predict subjective perception of these deficits more than objective cognitive performance. Both nonpharmacologic (eg, emboli reduction, temperature, or glucose management) and pharmacologic (eg, dexanabinol, glypromate, nootropics) strategies to prevent post-CABG cognitive deficits are under investigation. Given the large numbers of subjects who may already have CABG associated cognitive deficits, clinical trials of agents being tested for Alzheimer's disease (eg, donepezil, rivastigmine, memantine, neramexane, ginkgo) may also be informative. The results of multicenter long-term outcome studies (with matched control groups) as well as ongoing treatment trials will more conclusively address some of these issues. These data emphasize the need for clinicians to monitor cognitive function before and after coronary bypass surgery, and to educate patients.

Evaluation of the neuroprotective effects of S(+)-ketamine during open-heart surgery

We compared the effect of S(+)-ketamine to remifentanil, both in combination with propofol, on the neurocognitive outcome after open-heart surgery in 106 patients. A battery of neurocognitive tests was administered before surgery and 1 and 10 wk after surgery. Fourteen patients (25%) in the control group and 10 patients (20%) in the S(+)-ketamine group had 2 or more tests with a cognitive deficit (decline by at least one preoperative SD of that test in all patients) 10 wk after surgery (P = 0.54). Z-scores were calculated for all tests. No significantly better performance could be detected in the S(+)-ketamine group, except for the Trailmaking B test 10 wk after surgery. We conclude that S(+)-ketamine offers no greater neuroprotection compared with remifentanil during open-heart surgery.

IMPLICATIONS

N-methyl-D-aspartic acid receptors play an important role during ischemic brain injury. We could not demonstrate that S(+)-ketamine resulted in greater neuroprotective effects compared with remifentanil during cardiopulmonary bypass procedures when both were combined with propofol.

["Alternative" effects of local anesthetic agents]

The following article summarizes different aspects of local anesthetic effects that cannot be explained purely by a sodium channel blockade. Particularly remarkable is hereby their antiinflammatory activity, e.g. the inhibition of pathological changes such as excessive stimulation of the inflammatory system, without compromising the host defense system. In contrast to other immunosuppressive drugs commonly used for treating such conditions, local anesthetics look promising for the future as a new therapeutic option. Besides general anesthetic activity, local anesthetics exert cerebroprotective effects and are furthermore, in consideration of their cardiovascular stability, of interest during neuroanesthetic procedures. In addition, local anesthetics are known for their potency to minimize bronchial hyperreactivity, although details of the underlying mechanisms are not yet elucidated. These effects of local anesthetics may represent interesting prospects for which their relevance has to be determined.

Lidocaine attenuates apoptosis in the ischemic penumbra and reduces infarct size after transient focal cerebral ischemia in rats

Lidocaine is a local anesthetic and antiarrhythmic agent. Although clinical and experimental studies have shown that an antiarrhythmic dose of lidocaine can protect the brain from ischemic damage, the underlying mechanisms are unknown. In the present study, we examined whether lidocaine inhibits neuronal apoptosis in the penumbra in a rat model of transient focal cerebral ischemia. Male Wistar rats underwent a 90-min temporary occlusion of middle cerebral artery. Lidocaine was given as an i.v. bolus (1.5 mg/kg) followed by an i.v. infusion (2 mg/kg/h) for 180 min, starting 30 min before ischemia. Rats were killed and brain samples were collected at 4 and 24 h after ischemia. Apoptotic changes were evaluated by immunohistochemistry for cytochrome c release and caspase-3 activation and terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) for DNA fragmentation. Cytochrome c release and caspase-3 activation were detected at 4 and 24 h after ischemia and DNA fragmentation was detected at 24 h. Double-labeling with NeuN, a neuronal marker, demonstrated that cytochrome c, caspase-3, and TUNEL were confined to neurons. Lidocaine reduced cytochrome c release and caspase-3 activation in the penumbra at 4 h and diminished DNA fragmentation in the penumbra at 24 h. Lidocaine treatment improved early electrophysiological recovery and reduced the size of the cortical infarct at 24 h, but had no significant effect on cerebral blood flow in either the penumbra or core during ischemia. These findings suggest that lidocaine attenuates apoptosis in the penumbra after transient focal cerebral ischemia. The infarct-reducing effects of lidocaine may be due, in part, to the inhibition of apoptotic cell death in the penumbra.

Brain injury after adult cardiac surgery

Despite remarkable progress in surgical, cardiopulmonary bypass and anaesthetic techniques during the last three decades, brain damage remains an important complication of adult cardiac surgery. Effective brain protection strategies are already implemented today, but ongoing research is needed to meet the challenges faced in operating on increasingly old and disabled patients. The incidence of brain injury may be reduced by modifying the surgical procedure according to carotid duplex scanning and epiaortic echocardiography, by using techniques to reduce microembolization during cardiopulmonary bypass and by optimizing patient temperature during and after surgery. Increased knowledge will aid in choosing the best procedure or combination of procedures in each case to ensure that risks do not outweigh benefits.

The poor man's epidural: systemic local anesthetics for improving postoperative outcomes

The inflammatory response is an important determinant of outcome after major surgery. Perioperative excessive stimulation of the inflammatory and hemostatic systems plays a role in the development of postoperative ileus, ischemia-reperfusion syndromes (e.g. myocardial infarction), hypercoagulation syndromes (e.g. deep venous thrombosis) and pain; together, these represent a significant fraction of major postoperative disorders. Epidurally administered local anesthetics prevent or modulate many of these processes. Since local anesthetics show inflammatory modulating properties in vitro and in vivo, they might also prevent these postoperative inflammatory processes when administered intravenously. Clinical studies have shown that perioperative local anesthetic administration significantly reduces the incidence of thrombosis and postoperative pain, shortens postoperative ileus and decreases hospital stay. On this basis we hypothesize that continuous intravenous administration of local anesthetic perioperatively might prevent or reduce several postoperative disorders resulting from excessive stimulation of inflammatory and hemostatic systems, and thereby improve surgical outcome.

Anaesthesia: the patient's point of view

Patients scheduled for surgical procedures continue to express concerns about their safety, outcome, and comfort. All medical interventions carry risks, but the patient often considers anaesthesia as the intervention with the greatest risk. Many still worry that they will not wake up after their surgery, or that they will be awake during the operation. Such events have received attention from the media, but are very rare. Challenges to improve the comfort of patients continue, especially with regard to the almost universal problems of nausea, vomiting, and pain after surgery. A newer concern is that patients will develop some degree of mental impairment that may delay return to a full work and social lifestyle for days and weeks. Developments in technology, education, and training have had a major effect on anaesthetic practice, so that anaesthesia is increasingly regarded as safe for the patient. This article explores patients' concerns, and considers whether science and technology help to provide solutions to these complex difficulties.

A lignocaine infusion worsens the leukoencephalopathy due to a carbon monoxide exposure in sheep

Poisoning by carbon monoxide (CO) is common and conventional treatment of affected people is frequently unsuccessful. Lignocaine was identified as a potential therapy in this context because of the benefit shown for it in other brain injuries for which the received toxic mechanisms are similar. Twelve Romney ewes were exposed to 1% CO for 120 min were then infused intravenously with either lignocaine (N=6) or saline for 72 h, and were killed 5 days after the exposure for histological and immunohistochemical examination. This dose of CO was narcotic and caused white matter brain infarcts, with associated glial cell activation, axonal dysfunction and induction of both neuronal and glial haeme oxygenase and nitric oxide synthetase. The frequency of the white matter infarcts was significantly greater in the lignocaine-treated group. The mechanism of this adverse interaction is neither established here nor is it deducible from other published data; alternative antidotes to CO clearly need to be tested.