Chronic Tempol treatment restores pharmacological preconditioning in the senescent rat heart.

Cardioprotective effects of anesthetic preconditioning and cyclosporine A (CsA) are lost with aging. To extend our previous work and address a possible mechanism underlying age-related differences, we investigated the role of oxidative stress in the aging heart by treating senescent animals with the oxygen free radical scavenger Tempol. Old male Fischer 344 rats (22-24 mo) were randomly assigned to control or Tempol treatment groups for 2 or 4 wk (T×2wk and T×4wk, respectively). Rats received isoflurane 30 min before ischemia-reperfusion injury or CsA just before reperfusion. Myocardial infarction sizes were significantly reduced by isoflurane or CsA in the aged rats treated with Tempol (T×4wk) compared with old control rats. In other experiments, young (4-6 mo) and old rats underwent either chronic Tempol or vehicle treatment, and the levels of myocardial protein oxidative damage, antioxidant enzymes, mitochondrial Ca(2+) uptake, cyclophilin D protein, and mitochondrial permeability transition pore opening times were measured. T×4wk significantly increased MnSOD enzyme activity, GSH-to-GSSH ratios, MnSOD protein level, mitochondrial Ca(2+) uptake capacity, reduced protein nitrotyrosine levels, and normalized cyclophilin D protein expression in the aged rat heart. T×4wk also significantly prolonged mitochondrial permeability transition pore opening times induced by reactive oxygen species in old cardiomyocytes. Our studies demonstrate that 4 wk of Tempol pretreatment restores anesthetic preconditioning and cardioprotection by CsA in the old rat and that this is associated with decreased oxidative stress and improved mitochondrial function. Our results point to a new protective strategy for the ischemic myocardium in the high-risk older population.

Interactions of GSK-3ß with mitochondrial permeability transition pore modulators during preconditioning: age-associated differences.

Anesthetic preconditioning (APC) and ischemic preconditioning (IPC) are lost with normal aging. Here, we investigated age-related difference between phosphoglycogen synthase kinase-3beta (pGSK-3ß) and pGSK-3ß with modulators of mitochondrial permeability transition pore, including adenine nucleotide translocase (ANT), cyclophilin-D, or voltage-dependent anion channel. APC or IPC significantly increased pGSK-3ß in the young groups in both the cytosol and the mitochondria and also significantly increased pGSK-3ß in co-immunoprecipitates with ANT. Importantly, the level of cyclophilin-D in co-immunoprecipitates with ANT was significantly decreased in the young APC and IPC groups, but not in old rats. We also found that APC or IPC significantly prolonged mitochondrial permeability transition pore opening time in the young cardiomyocytes under oxidative stress, but not in the elderly. Attenuation of APC or IPC protection in the aging heart is associated with failure to reduce ANT-cyclophilin-D interactions and to decreased pGSK-3ß responsiveness of ANT, critical modulators of mitochondrial permeability transition pore.

The metabolomic profile during isoflurane anesthesia differs from propofol anesthesia in the live rodent brain.

Development of noninvasive techniques to discover new biomarkers in the live brain is important to further understand the underlying metabolic pathways of significance for processes such as anesthesia-induced apoptosis and cognitive dysfunction observed in the undeveloped brain. We used in vivo proton magnetic resonance spectroscopy and two different signal processing approaches to test the hypothesis that volatile (isoflurane) and intravenous (propofol) anesthetics at equipotent doses produce distinct metabolomic profiles in the hippocampus and parietal cortex of the live rodent. For both brain regions, prolonged isoflurane anesthesia was characterized by higher levels of lactate (Lac) and glutamate compared with long-lasting propofol. In contrast, propofol anesthesia was characterized by very low concentrations of Lac ([lac]) as well as glucose. Quantitative analysis revealed that the [lac] was fivefold higher with isoflurane compared with propofol anesthesia and independent of [lac] in blood. The metabolomic profiling further demonstrated that for both brain regions, Lac was the most important metabolite for the observed differences, suggesting activation of distinct metabolic pathways that may impact mechanisms of action, background cellular functions, and possible agent-specific neurotoxicity.

Cardioprotection of the aged rat heart by GSK-3beta inhibitor is attenuated: age-related changes in mitochondrial permeability transition pore modulation.

It is well established that inhibition of glycogen synthase kinase (GSK)-3ß in the young adult myocardium protects against ischemia-reperfusion (I/R) injury through inhibition of mitochondrial permeability transition pore (mPTP) opening. Here, we investigated age-associated differences in the ability of GSK-3ß inhibitor [SB-216763 (SB)] to protect the heart and to modulate mPTP opening during I/R injury. Fischer 344 male rats were assigned from their respective young or old age groups. Animals were subjected to 30 min ischemia following 120 min reperfusion to determine myocardial infarction (MI) size in vivo. Ischemic tissues were collected 10 min after reperfusion for nicotinamide adenine dinucleotide (NAD(+)) measurements and immunoblotting. In parallel experiments, ventricular myocytes isolated from young or old rats were exposed to oxidative stress through generation of reactive oxygen species (ROS), and mPTP opening times were measured by using confocal microscopy. Our results showed that SB decreased MI in young SB-treated rats compared with young untreated I/R animals, whereas SB failed to significantly affect MI in the old animals. SB also significantly increased GSK-3ß phosphorylation in young rats, but phosphorylation levels were already highly elevated in old control groups. There were no significant differences observed between SB-treated and untreated old animals. NAD(+) levels were better maintained in young SB-treated animals compared with the young untreated group during I/R, but this relative improvement was not observed in old animals. SB also significantly prolonged the time to mPTP opening induced by ROS in young cardiomyocytes, but not in aged cardiomyocytes. These results demonstrate that this GSK-3ß inhibitor fails to protect the aged myocardium in response to I/R injury or prevent mPTP opening following a rise in ROS and suggest that healthy aging alters mPTP regulation by GSK-3ß.

Survey study of anesthesiologists' and surgeons' ordering of unnecessary preoperative laboratory tests.

BACKGROUND: Nearly 20 years ago it was shown that patients are exposed to unnecessary preoperative testing that is both costly and has associated morbidity. To determine whether such unnecessary testing persists, we performed internal and external surveys to quantify the incidence of unnecessary preoperative testing and to identify strategies for reduction. METHODS: The medical records of 1000 consecutive patients scheduled for surgery at our institution were examined for testing outside of our approved guidelines. Subsequently, 4 scenarios were constructed to solicit physician views of appropriate testing: a 45-year-old woman for a laparoscopic ovarian cystectomy, a 23-year-old woman for right inguinal herniorrhaphy, a 50-year-old man for a hemithyroidectomy, and a 50-year-old man for a total hip replacement. One or more of these scenarios were sent to directors of preoperative clinics (all), United States anesthesiologists (all), gynecologists (cystectomy), general surgeons (herniorrhaphy), otolaryngologists (thyroidectomy), and orthopedists (hip replacement). Potential predictors of ordering and demographic information were collected. RESULTS: More than half of our patients had at least 1 unnecessary test based on our testing guidelines (95% lower confidence limit = 52%). The 17 responding preoperative directors were unanimous for 36 of the 72 combinations of test or consult (henceforth "test") and scenario as being unnecessary. Among the 175 anesthesiologists responding to the survey, 46% ordered 1 or more of the tests unanimously considered unnecessary by the preoperative directors for the given scenario. Among 17 potential predictors of anesthesiologists' unnecessary ordering, only training completed before 1980 significantly increased the risk of ordering at least 1 unnecessary test (by 48%, 95% confidence limits >29%). Anesthesiologists were 53% less likely to order at least 1 unnecessary test relative to gynecologists for the cystectomy scenario, 64% less likely than general surgeons for the herniorrhaphy scenario, 66% less likely than otolaryngologists for the thyroidectomy scenario, and 67% less likely than orthopedists for the hip replacement scenario. The 95% lower confidence limits were all >40%. CONCLUSIONS: The percentage of patients with at least 1 unnecessary test is a suitable end point for monitoring providers' ordering. The incidence can be high despite efforts at improvement, but may be reduced if anesthesiologists rather than surgeons order presurgical tests and consults. However, anesthesia groups should be cognizant of potential heterogeneity among them based on time since training.

Age-associated differences in activation of Akt/GSK-3beta signaling pathways and inhibition of mitochondrial permeability transition pore opening in the rat heart.

Pretreatment with isoflurane decreased myocardial infarction size in young rats (3-5 months) but not in old rats (20-24 months). To understand the mechanisms underlying the failure to protect the old myocardium, differences in phosphorylation of Akt/GSK-3beta and age-associated differences in mitochondrial permeability transition pore (mPTP) opening in the aging heart in vivo were measured. Isoflurane significantly increased Akt and GSK-3beta phosphorylation in the young groups. In contrast, levels of p-Akt and p-GSK-3beta were highly elevated in the old sham control groups. Isoflurane preconditioning significantly reduced the fall in NAD(+) levels induced by ischemia/reperfusion injury in the young animals, reflecting the inhibition of mPTP opening. In the old animals, however, isoflurane failed to prevent the fall in NAD(+) levels induced by ischemia/reperfusion injury. Lack of isoflurane-induced cardioprotective effects, seen in the old animals, can be explained by age-related differences in Akt/GSK-3beta signaling pathway and the inability to reduce mPTP opening following ischemia/reperfusion injury.

Age-associated changes in cardiac gene expression after preconditioning.

BACKGROUND: Cardiac protection afforded by ischemic preconditioning (IPC) and anesthetic preconditioning (APC) are significantly reduced in the senescent myocardium. The authors hypothesized that age would differentially modulate gene expression induced by IPC and APC in vivo. METHODS: Affymetrix RAT EXON ST 1.0 gene chips (Affymetrix, Santa Clara, CA) were used to explore the transcriptional response to IPC and APC in Fisher 344 male rats (young, 3-5 months, and old, 20-24 months, respectively). Both cohorts, young and old, were divided into three groups: (1) sham control, (2) IPC, and (3) APC. After a total of 90 min, the heart was removed, and the total RNA and protein were extracted. RESULTS: Thirty-one transcripts were increased in the young animals subjected to IPC, particularly transcriptional regulators (Atf3, Egr-1, Btg2, Egr2), cytokines (interleukin 6, CSF1, Myd88), chemokines (Cxcl10, Ccl2, Ccl7), regulators of growth and inflammation (Reg3g, Hamp), remodeling and cell adhesion migration (Cyr61, Tfpi2, Timp1), regulators of apoptosis/cell death (Birc3, Arntl, Hamp, Phlda1), and cell cycle control/DNA repairs (Rrad, Gadd45b, Gadd45g). In contrast, only one transcript increased (Atf3) in the old animals subjected to IPC. No changes in gene expression were found in the young or the old animals subjected to APC. CONCLUSIONS: Early-phase IPC and APC induced different genomic responses. The absence of detectable changes associated with early-phase APC suggests a posttranscriptional or posttranslational mechanism. The absence of a genomic response in the senescent myocardium (except for IPC-induced Atf3) could underlie the failure of IPC to provide any cardiac protective benefit to older animals.

Pharmacokinetic-pharmacodynamic modeling in anesthesia, intensive care and pain medicine.

PURPOSE OF REVIEW: Studies from the anesthesiology literature published in the last 2 years were selected to illustrate the most important developments in the field of pharmacokinetic-pharmacodynamic modeling. RECENT FINDINGS: The pharmacokinetic models focused on incorporating covariate, especially age for pediatric-geriatric use, and altered physiological states. The pharmacodynamic models studied the effect of rate of anesthetic administration, age, experimental conditions, and delay within the monitor on estimation of drug concentration in the biophase. Models for the surrogate measure of the components of general anesthesia, hypnosis (bispectral index scale, entropy), immobility (limb tetanic stimulus-induced withdrawal reflex) and antinociception (surgical stress index, skin conductance algesimeter) were developed and validated. Response surface models were used to study drug interactions for important end-points during surgery and also to optimize dosing of anesthetic agents to maximize the desired/undesired effect ratio. The models for target-controlled infusions were improved by incorporating more covariates, and the closed-loop system was refined by using adaptive controllers that individualize the pharmacokinetic/pharmacodynamic parameters to the particular patient by using Bayesian, Kalman filters, fuzzy logic or neural networks. SUMMARY: Progress was made by improving population pharmacokinetic/pharmacodynamic models, developing new indexes to measure drug effect and using them in an adaptive delivery system to the individual patient.

A randomized, double-blind, multicenter trial comparing transdermal scopolamine plus ondansetron to ondansetron alone for the prevention of postoperative nausea and vomiting in the outpatient setting.

BACKGROUND: Postoperative nausea and vomiting (PONV) are common complications after ambulatory surgery. We sought to determine whether the use of transdermal scopolamine (TDS) in combination with IV ondansetron (OND) is more effective than one alone for reducing PONV in outpatient settings. METHODS: In a randomized, double blind, multicenter trial, 620 at-risk female patients undergoing outpatient laparoscopic or breast augmentation surgery received either an active TDS patch or a similar appearing sham 2 h before entering the operating room. All patients received IV OND (4 mg) 2-5 min before induction of anesthesia followed by a general anesthetic regimen. Complete antiemetic response, defined as no vomiting/retching or rescue medication use, was measured through 24 h and 48 h after surgery. The proportion of patients with vomiting/retching, nausea, or use of rescue medication, the time from the end of surgery to the first episode of these events and the time to discharge from the hospital/surgery center, as well as the number and severity of vomiting/retching and nausea episodes, and patient satisfaction with antiemetic therapy were also collected. RESULTS: The combination of TDS + OND statistically significantly reduced nausea and vomiting/retching compared with OND alone 24 h after surgery but not at 48 h. The proportion of patients who did not experience vomiting/retching and did not use rescue medication was 48% for TDS + OND and 39% for OND alone (P < 0.02). Total response (no nausea, no vomiting/retching, and no use of rescue medication) was also statistically higher for the TDS + OND group compared with the OND-only group (35% vs 25%, P < 0.01). The time to first nausea, vomiting/retching, or rescue episode was statistically significantly longer for the TDS + OND group compared with the OND-only group (P < 0.05). The cumulative overall incidence of adverse events was lower in the TDS + OND group compared with the OND group (36.7% vs 49%, P < 0.01). CONCLUSIONS: TDS + OND reduces PONV compared with OND alone. This is achieved with a reduction in adverse events.

The effect of intravenous lidocaine on brain activation during non-noxious and acute noxious stimulation of the forepaw: a functional magnetic resonance imaging study in the rat.

BACKGROUND: Lidocaine can alleviate acute as well as chronic neuropathic pain at very low plasma concentrations in humans and laboratory animals. The mechanism(s) underlying lidocaine's analgesic effect when administered systemically is poorly understood but clearly not related to interruption of peripheral nerve conduction. Other targets for lidocaine's analgesic action(s) have been suggested, including sodium channels and other receptor sites in the central rather than peripheral nervous system. To our knowledge, the effect of lidocaine on the brain's functional response to pain has never been investigated. Here, we therefore characterized the effect of systemic lidocaine on the brain's response to innocuous and acute noxious stimulation in the rat using functional magnetic resonance imaging (fMRI). METHODS: Alpha-chloralose anesthetized rats underwent fMRI to quantify brain activation patterns in response to innocuous and noxious forepaw stimulation before and after IV administration of lidocaine. RESULTS: Innocuous forepaw stimulation elicited brain activation only in the contralateral primary somatosensory (S1) cortex. Acute noxious forepaw stimulation induced activation in additional brain areas associated with pain perception, including the secondary somatosensory cortex (S2), thalamus, insula and limbic regions. Lidocaine administered at IV doses of either 1 mg/kg, 4 mg/kg or 10 mg/kg did not abolish or diminish brain activation in response to innocuous or noxious stimulation. In fact, IV doses of 4 mg/kg and 10 mg/kg lidocaine enhanced S1 and S2 responses to acute nociceptive stimulation, increasing the activated cortical volume by 50%-60%. CONCLUSION: The analgesic action of systemic lidocaine in acute pain is not reflected in a straightforward interruption of pain-induced fMRI brain activation as has been observed with opioids. The enhancement of cortical fMRI responses to acute pain by lidocaine observed here has also been reported for cocaine. We recently showed that both lidocaine and cocaine increased intracellular calcium concentrations in cortex, suggesting that this pharmacological effect could account for the enhanced sensitivity to somatosensory stimulation. As our model only measured physiological acute pain, it will be important to also test the response of these same pathways to lidocaine in a model of neuropathic pain to further investigate lidocaine's analgesic mechanism of action.

Attenuation of isoflurane-induced preconditioning and reactive oxygen species production in the senescent rat heart.

BACKGROUND: Although attenuation of anesthetic preconditioning in aged ex vivo heart models has been studied extensively, there are no comparable in vivo studies. To extend previous work and to address a possible mechanism underlying age-related differences, we investigated isoflurane-induced preconditioning and reactive oxygen species (ROS) production in the aged rat heart in vivo. METHODS: Male Fisher 344 rats were assigned from their respective age groups (young, 3-5 mo; old, 20-24 mo) to either receive 30 min of 1.0 minimum alveolar concentration isoflurane or to a control group. Rats were subjected to coronary artery occlusion for 30 min followed by 2 h of reperfusion. A fluorescent probe for superoxide anion production (dihydroethidium, 1 mg) was administered in the absence of the isoflurane or just before isoflurane exposure in four additional groups. Myocardial infarct size and superoxide anion production were assessed using triphenyltetrazolium staining and epifluorescence microscopy, respectively. RESULTS: Isoflurane decreased myocardial infarct size of young rats (26.7% +/- 3.0%) compared with young controls (50.9% +/- 1.9%; P < 0.001), whereas isoflurane did not significantly affect myocardial infarct size of old rats (39.1% +/- 0.9%) compared with old controls (46.5% +/- 2.4%; P > 0.05). Isoflurane increased ROS levels in young rats (430.5 +/- 95.9 arbitrary units [AU]) compared with young controls (162.7 +/- 25.5 AU; P < 0.01). In contrast, no significant changes in ROS levels were observed in old animals (316.4 +/- 56.3 AU isoflurane versus 233.8 +/- 59.2 AU control). CONCLUSIONS: Reduction in the cardioprotective effects of isoflurane and attenuation of isoflurane-stimulated ROS production were observed in the senescent myocardium in vivo.