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

Lidocaine administration before tracheal extubation cannot reduce post-operative cognition disorders in elderly patients

Background:

Cognitive dysfunction after surgery is common in elderly patients. Many factors such as anesthetic drugs can cause complication in this surgery. Lidocaine is one of the drugs commonly used during anesthesia. So, we designed this study to find out cognitive effect of lidocaine in elderly patients undergoing non-cardiac surgeries.

Materials and Methods:

In this double-blinded clinical trial, we enrolled 70 patients older than 65 years age undergoing urologic or orthopedic surgeries, were divided in two groups. Patients randomly received intravenous lidocaine (1.5 mg/kg) or normal saline in the same volume immediately before extubation. Mini mental state examination (MMSE) test was used to evaluate cognitive state at discharge time, 6 and 24 h after surgery.

Results:

Mean MMSE scores at the time of discharge from recovery room in lidocaine and saline groups were 22.4 ± 4.5 vs. 22.1 ± 4.4, P = 0.755, respectively. It was significantly lower than MMSE before surgery, 6 and 24 h after the operation. The mean MMSE scores and frequency distribution of intensity of cognitive impairments were not significantly different between two groups at different times.

Conclusion:

Bolus intravenous lidocaine before extubation, did not affect cognitive states in elders undergoing non-cardiac surgery. Effect of lidocaine on cardiac surgeries is clear, but in non-cardiac surgeries, lidocaine has no clinical effects. So, more studies with different doses of lidocaine and different assessment methods are recommended.

Medical management of acute pain in patients with chronic pain

The number of patients with chronic pain has increased over the years, as well as the number of patients who manage chronic pain with opioids. As prescribed opioid use has increased, so has its abuse and misuse. It has also been estimated that the number of people using opioids illicitly has doubled worldwide over the last 20 years. Management of chronic pain with opioids is associated with pathophysiological phenomena such as tolerance, dependence and hyperalgesia. They can become a problem when chronic pain patients present for a surgical procedure. Furthermore, patients who are on opioids on a regular basis require higher amounts during the perioperative period. The perioperative management of the chronic pain patient is difficult and complex. Developing an appropriate plan that can fulfill patients' and surgical team's needs requires skills and experience. The aim of this review is to describe the options available for the optimal perioperative management of acute pain in patients with a history of chronic pain.

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.

Cognitive deficit in first-time coronary artery bypass graft patients: a randomized clinical trial of lidocaine versus procaine hydrochloride

Introduction:

Cognitive dysfunction increasingly has been recognized as a complication after cardiac surgery. Different methods have been considered for the reduction of cognitive dysfunction after cardiac surgery. One of these methods is by using lidocaine during surgery. The aim of this study was to determine the effects of adding lidocaine to the cardioplegia solution on cognitive impairment after coronary artery surgery.

Design and methods:

In a prospective, randomized, double-blind trial, 110 patients aged between 20-70 years, scheduled for elective CABG surgery using cardiopulmonary bypass, were recruited into the study. They were randomized into two groups who received either cardioplegia solution containing lidocaine 2 mg/kg or procaine hydrochloride 5 mg/kg. The neurocognitive test used in this study was the Mini Mental State Examination (MMSE) or Folstein test. The test was done on the day before and 10 days and 2 months after the operation.

Results:

In the procaine group, the total score after 10 days decreased significantly compared to the preoperative score (mean difference 0.68; 95% CI: 0.20 to 1.17, p=0.006). Comparison between mean differences after 10 and 60 days of operation between the lidocaine and procaine groups were statistically significant, p-value 0.017 and 0.013, respectively. There was no cognitive impairment in the lidocaine group, but, in the procaine group, four patients (7.7%) after 10 days and one patient (1.9%) after both 10 and 60 days had cognitive impairment, p=0.051.

Conclusions:

Administration of lidocaine compared to that of procaine through the cardioplegia solution had a better effect on cognitive function after coronary artery bypass graft surgery.

Brain damage in cardiac surgery patients

Neuropsychological disorders and brain injury are still a serious problem in cardiac surgery patients. Owing to multifactorial mechanism of brain injury during extracorporeal circulation, the effective and safe protection is extremely difficult. Despite several studies, the ideal neuroprotective treatment has not been found. Based on literature we analysed the main mechanisms of brain injury and new methods of brain protection.

Can postoperative cognitive dysfunction be avoided?

Postoperative cognitive dysfunction (POCD) refers to a postoperative decline in cognitive function compared with preoperative cognitive function. Diagnosis requires pre- and postoperative testing, the latter of which is usually performed both 7 days and 3 months postoperatively. Although several risk factors for POCD have been described, age is the only consistently reported risk factor. Postoperative cognitive dysfunction is often transient. It may last several months, and is associated with leaving the labor market prematurely and increased mortality. As the pathophysiology of POCD is still a matter of debate and is likely to be multifactorial, there are no widely accepted prophylactic and therapeutic interventions. In this article, we discuss POCD's definition, risk factors, long-term significance, and pathophysiology. We also present data on prophylactic interventions that have been investigated in clinical trials.

Delayed treatment with lidocaine reduces mouse microglial cell injury and cytokine production after stimulation with lipopolysaccharide and interferon γ

BACKGROUND

Neuroinflammation is an important pathological process for almost all acquired neurological diseases. Microglial cells play a critical role in neuroinflammation. We determined whether lidocaine, a local anesthetic with anti-inflammatory property, protected microglial cells and attenuated cytokine production from activated microglial cells.

METHODS

Mouse microglial cultures were incubated with or without 1 μg/mL lipopolysaccharide and 10 U/mL interferon γ (IFNγ) for 24 hours in the presence or absence of lidocaine for 1 hour started at 2, 3, or 4 hours after the onset of lipopolysaccharide and IFNγ stimulation. Lactate dehydrogenase release and cytokine production were determined after the cells were stimulated by lipopolysaccharide and IFNγ for 24 hours.

RESULTS

Lidocaine dose-dependently reduced lipopolysaccharide and IFNγ-induced microglial cell injury as measured by lactate dehydrogenase release. This effect was apparent with lidocaine at 2 μg/mL (30.3% ± 5.8% and 23.1% ± 9.7%, respectively, for stimulation alone and the stimulation in the presence of lidocaine, n = 18, P = 0.025). Lidocaine applied at 2, 3, or 4 hours after the onset of lipopolysaccharide and IFNγ stimulation reduced the cell injury. This lidocaine effect was not affected by the mitochondrial K(ATP) channel inhibitor 5-hydroxydecanoate. Similar to lidocaine, QX314, a permanently charged lidocaine analog that usually does not permeate through the plasma membrane, reduced lipopolysaccharide and IFNγ-induced microglial cell injury. QX314 also attenuated the stimulation-induced interleukin-1β production.

CONCLUSIONS

Delayed treatment with lidocaine protects microglial cells and reduces cytokine production from these cells. These effects may involve action site(s) on the cell surface.

Intravenous antiarrhythmic doses of lidocaine increase the survival rate of CA1 neurons and improve cognitive outcome after transient global cerebral ischemia in rats

Brain ischemia is often a consequence of cardiac or neurologic surgery. Prophylactic pharmacological neuroprotection would be beneficial for patients undergoing surgery to reduce brain damage due to ischemia. We examined the effects of two antiarrhythmic doses of lidocaine (2 or 4 mg/kg) on rats in a model of transient global cerebral ischemia. The occlusion of both common carotid arteries combined with hypotension for 10 min induced neuronal loss in the CA1 region of the hippocampus (18±12 vs. 31±4 neurons/200 μm linear distance of the cell body layer, X±SD; P<0.01). Lidocaine (4 mg/kg) 30 min before, during and 60 min after ischemia increased dorsal hippocampal CA1 neuronal survival 4 weeks after global cerebral ischemia (30±9 vs. 18±12 neurons/200 μm; P<0.01). There was no significant cell loss after 10 min of ischemia in the CA3 region, the dentate region or the amygdalae; these regions were less sensitive than the CA1 region to ischemic damage. Lidocaine not only increased hippocampal CA1 neuronal survival, but also preserved cognitive function associated with the CA1 region. Using an active place avoidance task, there were fewer entrances into an avoidance zone, defined by relevant distal room-bound cues, in the lidocaine groups. The untreated ischemic group had an average, over the nine sessions, of 21±12 (X±SD) entrances into the avoidance zone per session; the 4 mg/kg lidocaine group had 7±8 entrances (P<0.05 vs. untreated ischemic) and the non-ischemic control group 7±5 entrances (P<0.01 vs. untreated ischemic). Thus, a clinical antiarrhythmic dose of lidocaine increased the number of surviving CA1 pyramidal neurons and preserved cognitive function; this indicates that lidocaine is a good candidate for clinical brain protection.

Inhibition of acid sensing ion channel currents by lidocaine in cultured mouse cortical neurons

BACKGROUND

Lidocaine is a local anesthetic that has multiple pharmacological effects including antiarrhythmia, antinociception, and neuroprotection. Acid sensing ion channels (ASICs) are proton-gated cation channels that belong to the epithelial sodium channel/degenerin superfamily. Activation of ASICs by protons results in sodium and calcium influx. ASICs have been implicated in various physiological processes including learning/memory, nociception, and in acidosis-mediated neuron injury. In this study, we examined the effect of lidocaine on ASICs in cultured mouse cortical neurons.

METHODS

ASIC currents were activated and recorded using a whole-cell patch-clamp technique in cultured mouse cortical neurons. The effects of lidocaine at different concentrations were examined. To determine whether the inhibition of lidocaine on ASIC currents is subunit specific, we examined the effect of lidocaine on homomeric ASIC1a and ASIC2a currents expressed in Chinese hamster ovary cells.

RESULTS

Lidocaine significantly inhibits the ASIC currents in mouse cortical neurons. The inhibition was reversible and dose dependent. A detectable effect was noticed at a concentration of 0.3 mM lidocaine. At 30 mM, ASIC current was inhibited by approximately 90%. Analysis of the complete dose-response relationship yielded a half-maximal inhibitory concentration of 11.79 ± 1.74 mM and a Hill coefficient of 2.7 ± 0.5 (n = 10). The effect is rapid and does not depend on pH. In Chinese hamster ovary cells expressing different ASIC subunits, lidocaine inhibits the ASIC1a current without affecting the ASIC2a current.

CONCLUSION

ASIC currents are significantly inhibited by lidocaine. Our finding reveals a new pharmacological effect of lidocaine in neurons.

Avoiding stroke during cardiac surgery

The life saving benefits of cardiac surgery are frequently accompanied by negative side effects such as stroke, that occurs with an incidence of 2%-13% dependent to type of surgery. The etiology is most likely multifactorial with embolic events considered as main contributor. Although stroke presents a common complication, no guidelines for any routine use of pharmacological substances or non-pharmacological strategies exist to date. Non-pharmacological strategies include monitoring of brain oxygenation and perfusion with devices such as near infrared spectroscopy and Transcranial Doppler help. Epiaortic and transesophageal echocardiography visualize aorta pathology, enabling the surgeon to sidestep atheromatous segments. Additionally can the use of specially designed aortic cannulae and filters help to reduce embolization. Brain perfusion can be improved by using antero- or retrograde cerebral perfusion during deep hypothermic circulatory arrest, by tightly monitoring mean arterial blood pressure and hemodilution. Controlling perioperative temperature and glucose levels may additionally help to ameliorate secondary damage. Many pharmacological compounds have been shown to be neuroprotective in preclinical models, but clinical studies failed to confirm these results so far. Remacemide, an NMDA-receptor-antagonist showed a significant drug-based neuroprotection during cardiac surgery. Other substances currently assessed in clinical trials whose results are still pending are acadesine, an adenosine-regulating substance, the free radical scavenger edaravone and the local anesthetic lidocaine. Stroke remains as significant complication after cardiac surgery. Non-pharmacological strategies allow perioperative caregivers to detect injurious events and to ameliorate stroke and its sequelae. Considering the multi-factorial etiology though, stroke prevention will likely have to be addressed with an individualistic combination of different strategies and substances.

Measurement of post-operative cognitive dysfunction after cardiac surgery: a systematic review

Post-operative cognitive dysfunction (POCD) is a decline in cognitive function from pre-operative levels, which has been frequently described after cardiac surgery. The purpose of this study was to examine the variability in the measurement and definitions for POCD using the framework of a 1995 Consensus Statement on measurement of POCD. Electronic medical literature databases were searched for the intersection of the search terms 'thoracic surgery' and 'cognition, dementia, and neuropsychological test.' Abstracts were reviewed independently by two reviewers. English articles with >50 participants published since 1995 that performed pre-operative and post-operative psychometric testing in patients undergoing cardiac surgery were reviewed. Data relevant to the measurement and definition of POCD were abstracted and compared with the recommendations of the Consensus Statement. Sixty-two studies of POCD in patients undergoing cardiac surgery were identified. Of these studies, the recommended neuropsychological tests were carried out in less than half of the studies. The cognitive domains measured most frequently were attention (n=56; 93%) and memory (n=57; 95%); motor skills were measured less frequently (n=36; 60%). Additionally, less than half of the studies examined anxiety and depression, performed neurological exam, or accounted for learning. Four definitions of POCD emerged: per cent decline (n=15), standard deviation decline (n=14), factor analysis (n=13), and analysis of performance on individual tests (n=12). There is marked variability in the measurement and definition of POCD. This heterogeneity may impede progress by reducing the ability to compare studies on the causes and treatment of POCD.

Is There a Future for Neuroprotective Agents in Cardiac Surgery?

This article gives an overview of neuroprotective drugs that were recently tested in clinical trials in cardiac surgery. Also, recommendations are given for successful translational research and considerations for management during cardiac surgery.

N-ethyl lidocaine (QX-314) protects striatal neurons against ischemia: an in vitro electrophysiological study

In this study, we have investigated the neuroprotective actions of the membrane impermeable, lidocaine analog, N-ethyl lidocaine (QX-314) in the striatum. The effects of this drug were compared with those caused by the strictly-related-compound and sodium channel blocker lidocaine. To address this issue, electrophysiological recordings were performed in striatal slices, in control condition (normoxia) and during combined oxygen and glucose deprivation (in vitro ischemia). Either QX-314 or lidocaine induced, to some extent, a protection of the permanent electrophysiological alteration (field potential loss) caused by a period (12 min) of ischemia. Thus, both compounds permitted a partial recovery of the ischemic depression of the corticostriatal transmission and reduced the amplitude of the ischemic depolarization in medium spiny neurons. However, while QX-314, at the effective concentration of 100 microM, slightly reduced the amplitude of the excitatory field potential and did not affect the current-evoked spikes discharge of medium spiny striatal neurons, equimolar lidocaine depressed the field potential and eliminated repetitive spikes on a depolarizing step. On the basis of these observations, our results suggest the use of QX-314 as a neuroprotective agent in ischemic brain disorders.

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.

Comparison of two patient-controlled analgesia techniques on neuropsychological functioning in the immediate postoperative period

Pain may contribute to cognitive decline, which is a common complication in the early postoperative period. We compared the effects of two common pain management techniques, intravenous patient-controlled analgesia (PCA-IV) and patient-controlled epidural analgesia (PCEA), on cognitive functioning in the immediate postoperative period. Patients hospitalized for elective surgery were randomly assigned to one of the treatment groups (30 patients per group). A battery of objective, standardized neuropsychological tests was administered preoperatively and 24 hours after surgery. Pain intensity was also evaluated. Nonoperated volunteers served as controls. Patients of the PCA-IV group exhibited significantly higher pain scores than did patients of the PCEA group. PCA-IV patients exhibited significant deterioration in the postoperative period in all the neuropsychological measures, while the PCEA patients exhibited significant deterioration only in one cognitive index, compared to controls.

Intraoperative cerebral high-intensity transient signals and postoperative cognitive function: a systematic review

BACKGROUND

Much attention in the literature has focused on the relationship between perioperative microemboli during cardiac and vascular surgery and postoperative cognitive decline. Transcranial Doppler ultrasonography (TCD) has been used to measure high-intensity transient signals (HITS), which represent microemboli during cardiac, vascular, and orthopedic surgery. The purpose of this study was to systematically examine the literature with respect to HITS and postoperative cognitive function.

METHODS

Systematic PubMed searches identified articles related to the use of TCD and cognitive function in the surgical setting.

RESULTS

The literature remains largely undecided on the role of HITS and cognitive impairment after surgery, with most studies being underpowered to show a relationship. Although the cognitive effects of HITS may be difficult to detect, subclinical microemboli present potential harm, which may be modifiable.

CONCLUSIONS

TCD represents a tool for intraoperative cerebral monitoring to reduce the number of HITS during surgery.

Neuroprotection during cardiac surgery

Cardiac surgery continues to be associated with significant adverse cerebral outcomes, ranging from stroke to cognitive decline. The underlying mechanism of the associated cerebral injury is incompletely understood but is believed to be primarily caused by cerebral embolism and hypoperfusion, exacerbated by ischemia/reperfusion injury. Extensive research has been undertaken in an attempt to minimize the incidence of perioperative cerebral injury, and both pharmacological and nonpharmacological strategies have been investigated. Although many agents demonstrated promise in preclinical studies, there is currently insufficient evidence from clinical trials to recommend the routine administration of any pharmacological agents for neuroprotection during cardiac surgery. The nonpharmacological strategies that can be recommended on the basis of evidence include transesophageal echocardiography and epiaortic ultrasound-guided assessment of the atheromatous ascending aorta with appropriate modification of cannulation, clamping or anastomotic technique and optimal temperature management. Large-scale randomized controlled trials are still required to address further the issues of optimal pH management, glycemic control, blood pressure management and hematocrit during cardiopulmonary bypass. Past, present and future directions in the field of neuroprotection in cardiac surgery will be discussed.

Arterial gas embolism: a review of cases at Prince of Wales Hospital, Sydney, 1996 to 2006

Arterial gas embolism may occur as a complication of diving or certain medical procedures. Although relatively rare, the consequences may be disastrous. Recent articles in the critical care literature suggest the non-hyperbaric medical community may not be aware of the role for hyperbaric oxygen therapy in non-diving related gas embolism. This review is part of an Australian appraisal of experience in the management of arterial gas embolism over the last 10 years. We identified all patients referred to Prince of Wales Hospital Department of Diving and Hyperbaric Medicine with a diagnosis of arterial gas embolism from 1996 to 2006. Twenty-six patient records met our selection criteria, eight iatrogenic and 18 diving related. All patients were treated initially with a 280 kPa compression schedule. At discharge six patients were left with residual symptoms. Four were left with minor symptoms that did not significantly impact quality of life. Two remained severely affected with major neurological injury. Both had non-diving-related arterial gas embolism. There was a good outcome in the majority of patients who presented with arterial gas embolism and were treated with compression.

Dexmedetomidine during coronary artery bypass grafting surgery: is it neuroprotective?--A preliminary study

BACKGROUND

In the present study, we aimed to determine whether during coronary artery bypass grafting (CABG) surgery, dexmedetomidine has protective effects against cerebral ischemic injury.

METHOD

Twenty-four patients, aged 50-70 years, undergoing CABG surgery were randomized into two groups of 12 patients each: those receiving dexmedetomidine (group D) and those not receiving it (group C). As basal blood samples from arterial and jugular bulb catheters were drawn, dexmedetomidine (1 microg/kg bolus and infusion at a rate of 0.7 microg/kg/h) was administered to patients in group D. Arterial and jugular venous blood gas analyses, serum S-100B protein (S-100B), neuron-specific enolase (NSE) and lactate measurements were performed after induction, 10 min after the initiation of cardiopulmonary bypass (CPB), 1 min after declamping, at the end of CPB, at the end of the operation and 24 h after surgery. Mann-Whitney U- and Wilcoxon's tests were used for statistical analyses.

RESULTS

No significant between-group differences were found regarding arterial and jugular venous pH, PO(2), PCO(2) and O(2) saturations. S-100B, NSE and lactate levels were also similar between groups D and C. During the post-operative period, there were no clinically overt neurological complications in any patient.

CONCLUSION

Cerebral ischemia marker (S-100B, NSE, lactate) patterns were as expected during CPB; however, there were no differences between the groups, which led us to believe that during CABG surgery dexmedetomidine has no neuroprotective effects. Future studies with larger populations are recommended to further establish the effects of this drug.

Neuroprotection during cardiac surgery

Cerebral injury following cardiac surgery continues to be a significant source of morbidity and mortality after cardiac surgery. A spectrum of injuries ranging from subtle neurocognitive dysfunction to fatal strokes are caused by a complex series of multifactorial mechanisms. Protecting the brain from these injuries has focused on intervening on each of the various etiologic factors. Although numerous studies have focused on a pharmacologic solution, more success has been found with nonpharmacologic strategies, including optimal temperature management and reducing emboli generation.

The risk of vertebral canal complications in 2837 cardiac surgery patients with thoracic epidurals

BACKGROUND

Recent communications in the medical press have suggested that the rate of vertebral canal complications following epidural catheter placement is increasing in frequency, in particular the incidence of epidural abscess (Hearn M. Epidural abscess complicating insertion of epidural catheters. Br J Anaesth 2003; 90 (5): 706-7; Govasi C, Bland D, Poddar R, Horst C. Epidural abscess complicating insertion of epidural catheters. Br J Anaesth 2004; 92 (2): 294-5). We wished to investigate this in our population of cardiac surgical patients.

METHODS

We performed a retrospective review of the data from all patients who had undergone coronary artery bypass grafting or valve replacement surgery in our hospital over the past 8 years. This involved a review of computer databases, logbooks, radiology records, admission records, intensive care transfers, pain team ward round data and follow-up outpatient data referrals.

RESULTS

In total, 2837 patient admissions were examined and reviewed by the authors. No episodes of vertebral canal haematoma or abscess were observed.

CONCLUSIONS

Retrospective analysis of our working practice indicates that thoracic epidural anaesthesia and analgesia are safe in patients receiving cardiac surgery. We found no epidural haematoma or abscess in 2837 patients.

Lidocaine, MK-801, and MAC

BACKGROUND

Previous studies have found that the local anesthetic/sodium channel blocker lidocaine decreased MAC by maximum amounts approximately equal to the decreases produced by dizocilpine (MK-801), a N-methyl-d-aspartate (NMDA) receptor antagonist. Blockade of sodium channels by inhaled anesthetics has been suggested as a possible cause for impairment of transmission through NMDA receptors. We postulated that the net effect of lidocaine and MK-801 on MAC would be the same, albeit by affecting NMDA neurotransmission at different points.

METHODS

We measured the effect of various lidocaine infusions on the MAC of cyclopropane, halothane, isoflurane, and o-difluorobenzene in rats. We also measured the effect of concurrent lidocaine-MK-801 infusion on the MAC of isoflurane and o-difluorobenzene.

RESULTS

Our data contradicted our predictions. (a) We found no limit to the effect of lidocaine infusion, in some cases finding that lidocaine, alone, produced immobility; (b) lidocaine infusion did not decrease the MAC of o-difluorobenzene differently from the MAC of other inhaled anesthetics; and (c) the addition of MK-801 equally affected the decrease in MAC produced by lidocaine infusion for isoflurane versus o-difluorobenzene.

CONCLUSION

Lidocaine does not primarily decrease MAC by decreasing the release of glutamate from nerve terminals.

Piracetam Prevents Cognitive Decline in Coronary Artery Bypass: A Randomized Trial Versus Placebo

BACKGROUND

Coronary artery bypass grafting (CABG) can be associated with postoperative cognitive impairment and ischemic stroke. No effective treatment is currently available. The aim of this study was to evaluate the effectiveness of piracetam to treat the cognitive impairment after CABG in an investigator-initiated, double-blind, placebo-controlled, randomized clinical trial.

METHODS

Patients undergoing CABG (n = 98) were randomized to placebo (n = 48) or piracetam (n = 50). Study drugs were administered intravenously (150 mg/kg daily; 300 mg/kg on the day of surgery) from the day before surgery to 6 days after surgery, then orally (12 g/day) up to 6 weeks after surgery. Cognitive function was assessed before surgery (baseline) and 6 weeks after surgery (outcome) by using a battery of 12 neuropsychologic tests. The Spielberger Anxiety Inventory and the Beck Depression Inventory were also administered. The combined score derived from the standardized neuropsychologic assessments was analyzed by using an analysis of covariance with baseline and education as covariates.

RESULTS

Six weeks after surgery, the combined score indicated a statistically significant treatment effect in the per protocol population (1.848, p = 0.041) and a tendency towards statistical significance in the intent-to-treat population (1.624, p = 0.064) in the group treated with piracetam, but no statistically significant treatment effect was seen in the placebo. The state of anxiety measured by the Spielberger Anxiety Inventory was decreased in both groups (-9.27 and -6.37 in the placebo and piracetam groups, respectively).

CONCLUSIONS

Six weeks after CABG, cognition was significantly improved in patients treated with piracetam. Additional trials are required to confirm these effects.

Pharmacologic modulation of operative risk in patients who have cardiac disease

Cardiac complications continue to compose a major proportion of serious postoperative morbidity and mortality, and it is appropriate, therefore, that this area has received a lot of attention in the search for pharmacologic modulation of surgical outcomes. Despite numerous studies, conclusive data does not exist, making it difficult to recommend a course of action. beta-blockade has not only made it into national protocols, but is even considered as a quality assessment measure. However, the data are not quite as conclusive as it may sometimes appear. There have been few studies, with a small number of negative outcomes, and, at times, significant methodological concerns. The positive outcomes of meta-analyses rest essentially on a single trial in a highly selected patient population. Although use of beta-blockers in patients who have documented coronary artery disease and are undergoing major vascular procedures appears supported, it is premature to recommend beta-blockade for all patients with cardiac risk. Because these drugs are not without risks, it might be advisable to be restrained in their use until the results of the large-scale randomized POISE trial are available. For clonidine and statins, the data are even more tenuous, and largely based on retrospective reviews (with the exception of postprocedure use of statins, which is well supported). Here again, the results of large-scale prospective trials must become available before recommendations can be made. Finally, promising data indicate that it might be possible to modulate by pharmacologic means the neurocognitive decline that is frequently associated with cardiac surgery, and which is often considered by patients to be the most troublesome complication of the intervention.

Cardiopulmonary bypass management and neurologic outcomes: an evidence-based appraisal of current practices

Neurologic complications after cardiac surgery are of growing importance for an aging surgical population. In this review, we provide a critical appraisal of the impact of current cardiopulmonary bypass (CPB) management strategies on neurologic complications. Other than the use of 20-40 microm arterial line filters and membrane oxygenators, newer modifications of the basic CPB apparatus or the use of specialized equipment or procedures (including hypothermia and "tight" glucose control) have unproven benefit on neurologic outcomes. Epiaortic ultrasound can be considered for ascending aorta manipulations to avoid atheroma, although available clinical trials assessing this maneuver are limited. Current approaches for managing flow, arterial blood pressure, and pH during CPB are supported by data from clinical investigations, but these studies included few elderly or high-risk patients and predated many other contemporary practices. Although there are promising data on the benefits of some drugs blocking excitatory amino acid signaling pathways and inflammation, there are currently no drugs that can be recommended for neuroprotection during CPB. Together, the reviewed data highlight the deficiencies of the current knowledge base that physicians are dependent on to guide patient care during CPB. Multicenter clinical trials assessing measures to reduce the frequency of neurologic complications are needed to develop evidence-based strategies to avoid increasing patient morbidity and mortality.

A population-based study of the association between coronary artery bypass graft surgery (CABG) and cognitive decline: the Cache County study

BACKGROUND

The relationship between coronary artery bypass graft (CABG) surgery and cognitive decline remains uncertain, in particular with regard to whether there is delayed cognitive decline associated with this procedure.

METHODS

This was a population-based cohort study involving participants in the Cache County Study of Memory Health and Aging. At baseline the study enrolled 5,092 persons age 65 and older and followed them up three years later and again four years after that. Individuals who reported having undergone CABG surgery at study baseline or had this surgery in between follow-up waves were compared to individuals who never reported having the surgery. The main outcome measure was the Modified Mini Mental State (3MS). Multilevel models were used to examine the relationship between CABG surgery and cognitive decline over time.

RESULTS

Study participants who had CABG surgery evidenced 0.95 points of greater decline relative to baseline on the 3MS at the first follow-up interview after CABG, and an average of 1.9 points of greater decline at the second follow-up interview, than those without CABG (t = -2.51, df = 2,316, p = 0.0121), after adjusting for several covariates, including number of vascular conditions. This decline was restricted to individuals who were more than five years past the procedure and was not evident in the early years after the surgery.

CONCLUSIONS

CABG surgery is associated with accelerated cognitive decline more than five years after the procedure in a long-lived population. This decline is small and its clinical significance is uncertain. We could not find an association between CABG and decline in the first five post-operative years.

Desflurane improves the recovery of the evoked postsynaptic population spike from CA1 pyramidal cells after hypoxia in rat hippocampal slices

Desflurane is a volatile anesthetic that allows rapid induction and emergence, reduces cerebral metabolism, and enhances tissue perfusion. We studied the effect of treatment with 4%, 6%, and 12% desflurane on hypoxic neuronal damage by comparing the size of the postsynaptic evoked population spike recorded from the cornu ammonis 1 (CA1) pyramidal cell layer of rat hippocampal slices before and 2 hours after a hypoxic insult. When the tissue was treated with 6% desflurane before, during, and after 3.5 minutes of hypoxia, recovery was significantly better in slices exposed to desflurane (37% +/- 9%) compared with untreated hypoxic slices (15% +/- 5%). A lower (4%) or higher (12%) concentration of desflurane did not significantly improve recovery after 3.5 minutes of hypoxia. In the period before hypoxia, 12% and 6% desflurane significantly increased the latency and decreased the amplitude of the postsynaptic population spike; 4% desflurane had a similar but nonsignificant effect on latency and amplitude. We conclude that 6% desflurane, a clinically useful concentration (1 minimal alveolar concentration), improved the recovery of postsynaptic evoked responses in rat hippocampal slices after 3.5 minutes of hypoxia. In vivo studies must be conducted to assess the potential clinical significance of 6% desflurane's neuroprotective activity.

Attempted control of hyperglycemia during cardiopulmonary bypass fails to improve neurologic or neurobehavioral outcomes in patients without diabetes mellitus undergoing coronary artery bypass grafting

OBJECTIVE

Hyperglycemia worsens outcomes in critical illness. This randomized, double-blind, placebo-controlled clinical trial tested whether insulin treatment of hyperglycemia during cardiopulmonary bypass would reduce neurologic, neuro-ophthalmologic, and neurobehavioral outcomes after coronary artery bypass grafting.

METHODS

Three hundred eighty-one nondiabetic patients undergoing isolated coronary artery bypass grafting were given infusions of insulin or placebo when their blood glucose concentration exceeded 100 mg/dL during cardiopulmonary bypass. The primary outcome measure was the combined incidence of new neurologic, neuro-ophthalmologic, or neurobehavioral deficits or neurologic death observed at 4 to 8 days postoperatively. This same measure was assessed secondarily at 6 weeks and 6 months. Length of hospital stay was also compared as a secondary assessment.

RESULTS

The 2 groups were well matched at baseline. The insulin-treated group had significantly lower blood glucose concentrations during bypass. Sixty-six percent of subjects in the insulin-treated group and 67% of subjects in the control group demonstrated a new or worsening neurologic, neuro-ophthalmologic, or neurobehavioral deficit or neurologic death at the 4- to 8-day assessment. Outcomes were also similar in the 2 groups at 6 weeks (37% and 39% incidence, respectively) and 6 months (30% and 25%, respectively). Median lengths of stay were 7 and 6 days, respectively, in the treatment and control groups. None of these outcome differences was statistically significant.

CONCLUSION

Attempted control of hyperglycemia during cardiopulmonary bypass had no significant effect on the combined incidence of neurologic, neuro-ophthalmologic, or neurobehavioral deficits or neurologic death and failed to shorten the length of hospital stay. These results do not contradict those of other studies showing that aggressive control of hyperglycemia in the postoperative period will improve outcome.

KTX 0101: a potential metabolic approach to cytoprotection in major surgery and neurological disorders

KTX 0101 is the sodium salt of the physiological ketone, D-beta-hydroxybutyrate (betaOHB). This neuroprotectant, which has recently successfully completed clinical Phase IA evaluation, is being developed as an intravenous infusion fluid to prevent the cognitive deficits caused by ischemic foci in the brain during cardiopulmonary bypass (CPB) surgery. KTX 0101 maintains cellular viability under conditions of physiological stress by acting as a "superfuel" for efficient ATP production in the brain and peripheral tissues. Unlike glucose, this ketone does not require phosphorylation before entering the TCA cycle, thereby sparing vital ATP stores. Although no reliable models of CPB-induced ischemia exist, KTX 0101 is powerfully cytoprotectant under the more severe ischemic conditions of global and focal cerebral ischemia, cardiac ischemia and lung hemorrhage. Neuroprotection has been demonstrated by reductions in infarct volume, edema, markers of apoptosis and functional impairment. One significant difference between KTX 0101 and other potential neuroprotectants in development is that betaOHB is a component of human metabolic physiology which exploits the body's own neuroprotective mechanisms. KTX 0101 also protects hippocampal organotypic cultures against early and delayed cell death in an in vitro model of status epilepticus, indicating that acute KTX 0101 intervention in this condition could help prevent the development of epileptiform foci, a key mechanism in the etiology of intractable epilepsy. In models of chronic neurodegenerative disorders, KTX 0101 protects neurons against damage caused by dopaminergic neurotoxins and by the fragment of beta-amyloid, Abeta(1-42), implying possible therapeutic applications for ketogenic strategies in treating Parkinson's and Alzheimer's diseases. Major obstacles to the use of KTX 0101 for long term therapy in chronic disorders, e.g., Parkinson's and Alzheimer's diseases, are the sodium loading problem and the need to administer it in relatively large amounts because of its rapid mitochondrial metabolism. These issues are being addressed by designing and synthesizing orally bioavailable multimers of betaOHB with improved pharmacokinetics.

Neural correlates of cognitive dysfunction after cardiac surgery

Patients who underwent cardiac surgery and their relatives often complain on postoperative memory impairment. Most prospective neuropsychological studies also found postoperative cognitive decline early after surgery. Nevertheless, recently several reports questioned the existence of long-term brain alterations in these patient cohorts. The present review was aimed to clear up the true cardiac surgery effects on brain and cognitive functions. The reviewed data evidence that cardiac surgery interventions induce persistent localized brain ischemic lesions along with rapidly reversing global brain swelling and decreased metabolism. A range of studies showed that left temporal region was especially prone to perioperative ischemic injury, and these findings might explain persistent verbal short-term memory decline in a considerable proportion of cardiac surgery patient cohorts. Speed/time of cognitive performance is commonly decreased early after on-pump surgery either. Nevertheless, no association between psychomotor speed slowing and intraoperative embolic load was found. The rapid recovery of the latter cognitive domain might be better explained by surgery related acute global brain metabolism changes rather than ischemic injury effects. Hence, analyses of performance on separate cognitive tests rather than summarized cognitive indexes are strongly recommended for future neuropsychological studies of cardiac surgery outcomes.

Pre- or Postinsult Administration of Lidocaine or Thiopental Attenuates Cell Death in Rat Hippocampal Slice Cultures Caused by Oxygen-Glucose Deprivation

Lidocaine and thiopental improve recovery when administrated during hypoxia and ischemia; however, the effect of pre- or postinsult treatment alone is unknown. We applied either lidocaine or thiopental to hippocampal slice cultures from 20-day-old rats either before or after 10 min of oxygen-glucose deprivation (OGD). Propidium iodide (PI) fluorescence was used as an indicator of neuronal death for 7 days after OGD. OGD-induced neuronal death, in both the Cornus Ammonis 1 (CA1) and the dentate gyrus regions, peaked the first day after ischemia. Preinsult administration of either lidocaine (10, 100 microM) or thiopental (250, 600 microM) significantly reduced the damage measured on the first and second days after OGD; these drugs also significantly decreased the summed daily post-OGD PI fluorescence in both regions. Postinsult administration of lidocaine (10, 100 microM) or thiopental (250, 600 microM) significantly decreased the PI fluorescence on the first day after OGD; postinsult administration of these drugs also attenuated the summed daily post-OGD PI. These data indicate that the administration of lidocaine or thiopental either before or directly after OGD reduced neuronal damage in this in vitro model of cerebral ischemia. Postischemic administration is frequently the first opportunity for treatment.

IMPLICATIONS

Lidocaine or thiopental applied either 10 min before or 10 min directly after oxygen-glucose deprivation reduced neuronal cell death in rat hippocampal slice cultures. Postinsult administration is often the first opportunity for treatment after stroke; lidocaine and thiopental reduced damage caused by oxygen-glucose deprivation, an in vitro model of stroke.

Neuroprotective mechanisms of lidocaine against in vitro ischemic insult of the rat hippocampal CA1 pyramidal neurons

To compare neuroprotective effects of lidocaine and procaine against ischemic insult, intracellular recordings were made from rat hippocampal CA1 pyramidal neurons in slice preparations. Superfusion of the slices with oxygen- and glucose-deprived medium (in vitro ischemia) produced a rapid depolarization 6 min from the onset. When oxygen and glucose were reintroduced, the membrane depolarized further until it reached 0 mV, and thereafter the membrane showed no functional recovery. Pretreatment with lidocaine (10 microM), but not procaine (50 microM), restored the membrane potential after the reintroduction of oxygen and glucose. Lidocaine, compared to procaine, significantly inhibited the reduction in both tissue ATP content and flavoprotein fluorescence during and after in vitro ischemia. Under electron microscopy, only lidocaine well preserved the structure of mitochondria in the CA1 pyramidal cell body. Extracellular recordings revealed that procaine reduced the field postsynaptic potential whereas lidocaine augmented it. Both drugs reduced the presynaptic volley dose-dependently. Neither lidocaine nor procaine significantly affected a rapid rise of the intracellular Ca2+ level produced by in vitro ischemia in the CA1 region. All the results suggest that the neuroprotective lidocaine action is due to the protection of the mitochondria to maintain the tissue ATP content during and after in vitro ischemia.

Aprotinin decreases the incidence of cognitive deficit following CABG and cardiopulmonary bypass: a pilot randomized controlled study

PURPOSE

Cognitive deficit after coronary artery bypass surgery (CABG) has a high prevalence and is persistent. Meta-analysis of clinical trials demonstrates a decreased incidence of stroke after CABG when aprotinin is administrated perioperatively. We hypothesized that aprotinin administration would decrease the incidence of cognitive deficit after CABG.

METHODS

Thirty-six ASA III-IV patients undergoing elective CABG were included in a prospective, randomized, single-blinded pilot study. Eighteen patients received aprotinin 2 x 10(6) KIU (loading dose), 2 x 10(6) KIU (added to circuit prime) and a continuous infusion of 5 x 10(5) KIU.hr(-1). A battery of cognitive tests was administered to patients and spouses (n = 18) the day before surgery, four days and six weeks postoperatively.

RESULTS

Four days postoperatively new cognitive deficit (defined by a change in one or more cognitive domains using the Reliable Change Index method) was present in ten (58%) patients in the aprotinin group compared to 17 (94%) in the placebo group [95% confidence interval (CI) 0.10-0.62, P = 0.005); (P = 0.01)]. Six weeks postoperatively, four (23%) patients in the aprotinin group had cognitive deficit compared to ten (55%) in the placebo group (95% CI 0.80-0.16, P = 0.005); (P = 0.05).

CONCLUSION

In this prospective pilot study, the incidence of cognitive deficit after CABG and cardiopulmonary bypass is decreased by the administration of high-dose aprotinin.

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.