Siamak Rahman

Phosphorylation of GSK-3β Mediates Intralipid-induced Cardioprotection against Ischemia/Reperfusion Injury

Background:Intralipid (Sigma, St. Louis, MO), a brand name for the first safe fat emulsion for human use, has been shown to be cardioprotective. However, the mechanism of this protection is not known. The authors investigated the molecular mechanism(s) of Intralipid-induced cardioprotection against ischemia/reperfusion injury, particularly the role of glycogen synthase kinase-3&bgr; (GSK-3&bgr;) and mitochondrial permeability transition pore in this protective action. Methods:In vivo rat hearts or isolated Langendorff-perfused mouse hearts were subjected to ischemia followed by reperfusion with Intralipid (1% in ex vivo and one bolus of 20% in in vivo) or vehicle. The hemodynamic function, infarct size, threshold for the opening of mitochondrial permeability transition pore, and phosphorylation levels of protein kinase B (Akt)/extracellular signal regulating kinase (ERK)/GSK-3&bgr; were measured. Results:Administration of Intralipid at the onset of reperfusion resulted in approximately 70% reduction in infarct size in the in vivo rat model. Intralipid also significantly improved functional recovery of isolated Langendorff-perfused mouse hearts as the rate pressure product was increased from 2,999 ± 863 mmHg*beats/min in the control group to 13,676 ± 611 mmHg*beats/min (mean±SEM) and the infarct size was markedly smaller (18.3 ± 2.4% vs. 54.8 ± 2.9% in the control group, P < 0.01). The Intralipid-induced cardioprotection was fully abolished by LY294002, a specific inhibitor of PI3K, but only partially by PD98059, a specific ERK inhibitor. Intralipid also increased the phosphorylation levels of Akt/ERK1/glycogen synthase kinase-3&bgr; by eightfold, threefold, and ninefold, respectively. The opening of mitochondrial permeability transition pore was inhibited by Intralipid because calcium retention capacity was higher in the Intralipid group (274.3 ± 8.4 nM/mg vs. 168.6 ± 9.6 nM/mg in the control group). Conclusions:Postischemic treatment with Intralipid inhibits the opening of mitochondiral permeability transition pore and protects the heart through glycogen synthase kinase-3&bgr; via PI3K/Akt/ERK pathways.

Fatty-acid oxidation and calcium homeostasis are involved in the rescue of bupivacaine-induced cardiotoxicity by lipid emulsion in rats.

Objectives: Lipid emulsion has been shown to be effective in resuscitating bupivacaine-induced cardiac arrest but its mechanism of action is not clear. Here we investigated whether fatty-acid oxidation is required for rescue of bupivacaine-induced cardiotoxicity by lipid emulsion in rats. We also compared the mitochondrial function and calcium threshold for triggering of mitochondrial permeability transition pore opening in bupivacaine-induced cardiac arrest before and after resuscitation with lipid emulsion. Design: Prospective, randomized animal study. Setting: University research laboratory. Subjects: Adult male Sprague-Dawley rats. Interventions: Asystole was achieved with a single dose of bupivacaine (10 mg/kg over 20 secs, intravenously) and 20% lipid emulsion infusion (5 mL/kg bolus, and 0.5 mL/kg/min maintenance), and cardiac massage started immediately. The rats in CVT-4325 (CVT) group were pretreated with a single dose of fatty-acid oxidation inhibitor CVT (0.5, 0.25, 0.125, or 0.0625 mg/kg bolus intravenously) 5mins prior to inducing asystole by bupivacaine overdose. Heart rate, ejection fraction, fractional shortening, the threshold for opening of mitochondrial permeability transition pore, oxygen consumption, and membrane potential were measured. The values are mean ± SEM. Measurements and Main Results: Administration of bupivacaine resulted in asystole. Lipid Emulsion infusion improved the cardiac function gradually as the ejection fraction was fully recovered within 5 mins (ejection fraction = 64 ± 4% and fractional shortening = 36 ± 3%, n = 6) and heart rate increased to 239 ± 9 beats/min (71% recovery, n = 6) within 10 mins. Lipid emulsion was only able to rescue rats pretreated with low dose of CVT (0.0625 mg/kg; heart rate ~ 181 ± 11 beats/min at 10 mins, recovery of 56%; ejection fraction = 50 ± 1%; fractional shortening = 26 ± 0.6% at 5 mins, n = 3), but was unable to resuscitate rats pretreated with higher doses of CVT (0.5, 0.25, or 0.125 mg/kg). The calcium-retention capacity in response to Ca2+ overload was significantly higher in cardiac mitochondria isolated from rats resuscitated with 20% lipid emulsion compared to the group that did not receive Lipid Emulsion after bupivacaine overdose (330 ± 42 nmol/mg vs. 180 ± 8.2 nmol/mg of mitochondrial protein, p < .05, n = 3 in each group). The mitochondrial oxidative rate and membrane potential were similar in the bupivacaine group before and after resuscitation with lipid emulsion infusion. Conclusions: Fatty-acid oxidation is required for successful rescue of bupivacaine-induced cardiotoxicity by lipid emulsion. This rescue action is associated with inhibition of mitochondrial permeability transition pore opening.

Intralipid, a Clinically Safe Compound, Protects the Heart Against Ischemia-Reperfusion Injury More Efficiently Than Cyclosporine-A

Background:We have recently shown that postischemic administration of intralipid protects the heart against ischemia-reperfusion injury. Here we compared the cardioprotective effects of intralipid with cyclosporine-A, a potent inhibitor of the mitochondrial permeability transition pore opening. Methods:In vivo rat hearts or isolated Langendorff-perfused mouse hearts were subjected to ischemia followed by reperfusion with intralipid (0.5%, 1% and 2% ex-vivo, and 20% in vivo), cyclosporine-A (0.2 &mgr;M, 0.8 &mgr;M, and 1.5 &mgr;M ex- vivo and 10 mg/kg in vivo), or vehicle. The hemodynamic function, infarct size, calcium retention capacity, mitochodrial superoxide production, and phosphorylation levels of protein kinase B (Akt)/glycogen synthase kinase-3&bgr; (GSK-3&bgr;) were measured. The values are mean ± SEM. Results:Administration of intralipid at reperfusion significantly reduced myocardial infarct size compared with cyclosporine-A in vivo (infarct size/area at risk)%: 22.9 ± 2.5% vs. 35.2 ± 3.5%; P = 0.030, n = 7/group). Postischemic administration of intralipid at its optimal dose (1%) was more effective than cyclosporine-A (0.8 &mgr;M) in protecting the ex vivo heart against ischemia-reperfusion injury, as the rate pressure product at the end of reperfusion was significantly higher (mmHg · beats/min: 12,740 ± 675 [n = 7] vs. 9,203 ± 10,781 [n = 5], P = 0.024), and the infarct size was markedly smaller (17.3 ± 2.9 [n = 7] vs. 29.2 ± 2.7 [n = 5], P = 0.014). Intralipid was as efficient as cyclosporine-A in inhibiting the mitochondrial permeability transition pore opening (calcium retention capacity = 280 ± 8.2 vs. 260.3 ± 2.9 nmol/mg mitochondria protein in cyclosporine-A, P = 0.454, n = 6) and in reducing cardiac mitochondrial superoxide production. Unlike intralipid, which increased phosphorlyation of Akt (6-fold) and GSK-3&bgr; (5-fold), cyclosporine-A had no effect on the activation of these prosurvival kinases. Conclusions:Although intralipid inhibits the opening of the mitochondrial permeability transition pore as efficiently as cyclosporine-A, intralipid is more effective in reducing the infarct size and improving the cardiac functional recovery.

Impact of Enhanced Recovery After Surgery and Opioid-Free Anesthesia on Opioid Prescriptions at Discharge From the Hospital: A Historical-Prospective Study.

BACKGROUND: The United States is in the midst of an opioid epidemic, and opioid use disorder often begins with a prescription for acute pain. The perioperative period represents an important opportunity to prevent chronic opioid use, and recently there has been a paradigm shift toward implementation of enhanced recovery after surgery (ERAS) protocols that promote opioid-free and multimodal analgesia. The objective of this study was to assess the impact of an ERAS intervention for colorectal surgery on discharge opioid prescribing practices. METHODS: We conducted a historical-prospective quality improvement study of an ERAS protocol implemented for patients undergoing colorectal surgery with a focus on the opioid-free and multimodal analgesia components of the pathway. We compared patients undergoing colorectal surgery 1 year before implementation (June 15, 2015, to June 14, 2016) and 1 year after implementation (June 15, 2016, to June 14, 2017). RESULTS: Before the ERAS intervention, opioids at discharge were not significantly increasing (1% per month; 95% confidence interval [CI], −1% to 3%; P = .199). Immediately after the ERAS intervention, opioid prescriptions were not significantly lower (13%; 95% CI, −30% to 3%; P = .110). After the intervention, the rate of opioid prescriptions at discharge did not decrease significantly 1% (95% CI, −3% to 1%) compared to the pre-period rate (P = .399). Subgroup analysis showed that in patients with a combination of low discharge pain scores, no preoperative opioid use, and low morphine milligram equivalents consumption before discharge, the rate of discharge opioid prescription was 72% (95% CI, 61%–83%). CONCLUSIONS: This study is the first to report discharge opioid prescribing practices in an ERAS setting. Although an ERAS intervention for colorectal surgery led to an increase in opioid-free anesthesia and multimodal analgesia, we did not observe an impact on discharge opioid prescribing practices. The majority of patients were discharged with an opioid prescription, including those with a combination of low discharge pain scores, no preoperative opioid use, and low morphine milligram equivalents consumption before discharge. This observation in the setting of an ERAS pathway that promotes multimodal analgesia suggests that our findings are very likely to also be observed in non-ERAS settings and offers an opportunity to modify opioid prescribing practices on discharge after surgery. For opioid-free anesthesia and multimodal analgesia to influence the opioid epidemic, the dose and quantity of the opioids prescribed should be modified based on the information gathered by in-hospital pain scores and opioid use as well as pain history before admission.

A heat map of superior cervical ganglion location relative to the common carotid artery bifurcation

BACKGROUND: Determining the superior cervical ganglions precise anatomical location for local anesthetic block, when stellate block is not feasible or is contraindicated, is difficult. METHODS: We dissected the superior cervical ganglion in 60 embalmed cadaveric specimens. Multiple regressions determined whether subject characteristics predicted the distance between the superior cervical ganglion and common carotid artery bifurcation and the superior cervical ganglion dimensional width and area. Based on these regressions, we mapped the ganglion and common carotid artery bifurcation using a pseudocolor statistical heat map. RESULTS: The statistical model significantly predicted the superior cervical ganglion–common carotid artery bifurcation distance (P = 0.01), and the superior cervical ganglion dimensional width (P = 0.02). CONCLUSION: This study determined that the common carotid artery bifurcation is a good landmark for localizing the superior cervical ganglion for anesthetic block.

Involvement of Opioid Receptors in the Lipid Rescue of Bupivacaine-Induced Cardiotoxicity.

BACKGROUND:Lipid emulsion (LE) has been successfully used for resuscitation of local anesthetic cardiotoxicity caused by bupivacaine overdose. Opioid receptors have been shown to play a key role in cardio protection. We explored whether this rescue action of LE is mediated through opioid receptors. METHODS:Asystole was induced by bupivacaine (10 mg/kg over 20 seconds, IV) in young male Sprague-Dawley rats, and resuscitation with LE (intralipid 20%; 5 mL/kg bolus and 0.5 mL/kg/min maintenance) was started immediately. The rats were pretreated 2 minutes before inducing asystole with nonselective opioid receptor antagonists such as naloxone and naloxone methiodide, as well as highly selective opioid receptor antagonists for subtype &kgr;, &dgr;, and µ or phosphate buffer solution as a control. Heart rates and ejection fractions were measured using echocardiography. RESULTS:LE rescue of bupivacaine cardiotoxicity was prevented by high-dose (1 mg/kg) naloxone but not by lower doses of naloxone (1, 5, and 10 µg/kg), by naloxone methiodide (which does not cross the blood–brain barrier), and by a selective &dgr;- and &kgr;-opioid receptor antagonists at a higher (10 mg/kg) dose. Successful LE rescue was not affected by highly selective µ-opioid receptor antagonists. &dgr;-Opioid receptor antagonist (10 mg/kg) pretreatment also resulted in reduced phosphorylation level of cardiac glycogen synthase kinase-3&bgr; in rats that were not resuscitated by LE compared with control. CONCLUSIONS:Our data highlight the involvement of peripheral &dgr;- and &kgr;-opioid receptors in the rescue action of LE.

Thoracic Epidural Anesthesia Can Be Effective for the Short‐Term Management of Ventricular Tachycardia Storm

Background Novel therapies aimed at modulating the autonomic nervous system, including thoracic epidural anesthesia (TEA), have been shown in small case series to be beneficial in treating medically refractory ventricular tachycardia (VT) storm. However, it is not clear when these options should be considered. We reviewed a multicenter experience with TEA in the management of VT storm to determine its optimal therapeutic use. Methods and Results Data for 11 patients in whom TEA was instituted for VT storm between July 2005 and March 2016 were reviewed to determine the clinical characteristics, outcomes, and role in management. The clinical presentation was incessant VT in 7 (64%), with polymorphic VT in 3 (27%) and monomorphic VT in 8 (73%). The underlying conditions were nonischemic cardiomyopathy in 5 (45%), ischemic cardiomyopathy in 3 (27%), and hypertrophic cardiomyopathy, Brugada syndrome, and cardiac lipoma in 1 (9%) each. Five (45%) had a complete and 1 (9%) had a partial response to TEA; 4 of the complete responders had incessant VT. All 4 patients with a documented response to deep sedation demonstrated a complete response to TEA. Conclusions More than half of the patients with VT storm in our series responded to TEA. TEA may be effective and should be considered as a therapeutic option in patients with VT storm, especially incessant VT, who are refractory to initial management. Improvement in VT burden with deep sedation may suggest that sympathoexcitation plays a key role in perpetuating VT and predict a positive response to TEA.

Inotropic effect of lipid emulsion: a new perspective*.

August 2013 • Volume 41 • Number 8 It is not every day that the medical and scientific communities come across a medicine with so many potentials and therapeutic indications. Lipid emulsion, which was used for several decades mainly as parenteral nutrition, has recently emerged as a promising cardioprotective agent. Dr. Weinberg’s group discovered for the first time in 1998 that lipid emulsion can also be very effective in rescuing acute and deadly cardiotoxicity of local anesthetics, such as bupivacaine, in an experimental rat model (1). Later, lipid emulsion has also been used to resuscitate patients from toxicities caused by a wide range of factors, such as calcium channel blockers, β-blockers, and psycho-active agents (2–9). However, the underlying mechanisms involved in lipid rescue are complex and so far partitioning (10), and metabolic effects through the fatty acid oxidation pathway (11) and modulation of cardiac sodium channels (12) seem to be the major mechanisms. The article by Fettiplace et al (13) from Dr. Weinberg’s group, a pioneer in this field, investigated the fast inotropic effect (within a few minutes) of lipid emulsion in the absence of a pathologic insult. They found that one bolus of lipid emulsion infusion increases the arterial pressure and aortic flow and improves cardiac hemodynamics in the rat. Therefore, they speculated that rapid inotropic effect of lipid emulsion could also contribute to its resuscitative effect. The inotropic effect of lipid emulsion on cardiac contractility reported by Fettiplace et al could be due to increased intracellular calcium (14, 15). Application of both saturated and unsaturated long-chain-free fatty acids has been demonstrated to rapidly activate voltage-gated calcium channels (mainly L type) in isolated cardiomyocytes (16). Direct activation of the calcium current by fatty acids could partly explain the early effects of lipid emulsions on resuscitation of myocardial toxicity triggered by local anesthetics. In this issue of Critical Care Medicine, Fettiplace et al (13) observed the fast beneficial effect of a bolus infusion of lipid emulsion on systemic hemodynamics. The inotropy and increased aortic flow offered by lipid emulsion in the study conducted by Fettiplace et al is only sustained for several minutes after lipid emulsion withdrawal. However, in the context of cardiac pharmacotoxicity, a bolus infusion of lipid emulsion is sufficient to fully restore cardiac function both in experimental and in clinical settings. These data seem to make the rapid inotropic effect of lipid emulsion a less likely contributor to the long-term effect of lipid emulsion on resuscitation. In light of these findings, it can be concluded that either the effect of lipid emulsion on cardiac hemodynamics is transient under physiologic conditions or the fast inotropic benefit contributes only to the initial phase of the resuscitation. Future studies are needed to explore whether lipid emulsion can also exert rapid inotropic action in the pathologic setting. Both human and animal studies have shown that lipid emulsion is able to improve blood pressure mainly by increasing vascular resistance (17, 18). In contrast to these studies, Fettiplace et al (13) did not observe any change in peripheral vascular resistance following lipid emulsion infusion and claimed that the positive flow and rapid inotropic effects of lipid infusion are not caused by changes in peripheral resistance. The metabolic changes (increasing the cardiac utilization of glucose and fatty acid) result in appreciable alterations on myocardial contractile function (19). Thus, Fettiplace et al speculated that the improved hemodynamic performance offered by lipid emulsion infusion could be in part due to a metabolic benefit. In agreement with the metabolic effect of lipid emulsion, a recent study from our group showed that inhibition of fatty acid oxidation with CVT-4325 completely abolishes lipid-induced rescue of bupivacaine overdose (11). Taken together, lipidbased oxidative phosphorylation plays a role in maintaining the cardiac mechanical function, and the effect of lipid emulsion on contractile properties of the myocardium is actually the consequence of metabolic changes induced by lipid emulsion. Some of the cardioprotective action of lipid emulsion in the acute setting, such as ischemia-reperfusion injury, could be mediated via activation of the well-known signaling pathways. Our group has shown that lipid emulsion activates protein kinase B (AKT)/extracellular signal-regulated kinase/glycogen synthase kinase signaling pathways to restore cardiac hemodynamics and contractility in ischemia-reperfusion injury (20, 21). Our group has also highlighted the involvement of G protein–coupled receptors in mediating the rescue action of lipid emulsion in resuscitating the heart, as in the presence of opioid receptor antagonists, lipid emulsion failed to rescue bupivacaine-induced cardiac arrest (22). Fettiplace et al (13) speculate that activation of some of the known protective pathways could underlie the rapid inotropic effect of lipid emulsion observed under physiologic conditions. We should, however, keep in mind Inotropic Effect of Lipid Emulsion: A New Perspective*

Phosphorylation of GSK-3b is Required for Intralipid to Protect the Heart Against Ischemia/Reperfusion Injury

Recently we found that administration of Intralipid (ILP) during reperfusion significantly improves post-ischemic cardiac function and reduces the myocardial infarct size by ∼70% , both in the isolated mouse heart and in-vivo rat heart. Here we investigated whether ILP-induced cardioprotection is mediated through the inhibition of GSK-3b. Wild type (WT) C57BL/6 male mice and GSK-3b Knockin (KI) were used. The isolated hearts were subjected to 20 min of global normothermic ischemia followed by reperfusion with 1% ILP (40 min for heart function and infarct size and 10 min for calcium retention capacity (CRC) experiments). The left ventricular (LV) systolic pressure, LV end-diastolic pressure (LVDP), heart rate, maximum velocity of contraction (dP/dt max) and maximum velocity of relaxation (dP/dt min) were recorded. Myocardial necrosis was assessed using TTC staining. Mitochondria were isolated to measure CRC by calculating the number of pulses required to trigger the opening of the mitochondrial transition permeability pore as a result of calcium overload. Before ischemia, the baseline RPP, LVDP, dP/dtmax and dP/dtmin in GSK-3b KI mice were similar to WT. However, the functional recovery during reperfusion was very poor in GSK-3b KI mice. At the end of 40 min of reperfusion, the RPP was 1990±499 in GSK-3b KI mice vs. 15405±1011mmHg∗beats/min in WT, the LV dP/dtmax was 239.7±17.8 in GSK-3b KI vs. 2703±145 mmHg/s in WT and the LV dP/dtmin was 219±14 in GSK-3b KI vs. 1683±66 mmHg/s in WT. The infarct size was significantly larger compared to WT (45.3±10.3 vs. 16.7±2.33% in WT, P<0.001). Postischemic administration of ILP in GSK-3b KI mice demonstrated lower CRC than WT (1.3±0.1 vs. 2.7±0.06 µM/mg-mitochondrial protein in WT). In conclusions, these data demonstrate that phosphoryltaion of GSK-3b is required for the cardioprotective action of ILP.

CVT Inhibits the Intralipid Rescue of Bupivacaine-Induced Cardiotoxicity in a Dose-Dependant Manner

Intralipid (ILP) is effective in resuscitating Bupivacaine-induced cardiac arrest, but its mechanism of action is not clear. Here we investigated whether protective action of ILP is mediated through fatty acid oxidation pathway using CVT-4325, a fatty acid oxidation inhibitor. Male Sprague-Dawley rats (300-350 g) were anesthetized (ketamine (80mg/kg) and xylazine (8mg/kg, i.p.)) and then ventilated. In control (CTRL, n=8), asystole was achieved with a single dose of Bupivacaine (10mg/kg over 20 seconds, i.v.) and then resuscitation was started immediately using ILP (5ml/kg bolus, and 0.5ml/kg/min maintenance) together with cardiac massage. In CVT group (n=12), the protocol was identical to CTRL, except that rats were pre-treated with different doses of CVT (0.5, 0.25, 0.125 and 0.0625mg/kg bolus i.v.) for 5 min. The heart rate (HR), ejection fraction (EF) and fractional shortening (FS) were measured by echocardiography. As expected, in CTRL group, administration of Bupivacaine resulted in asystole and ILP improved HR and cardiac function gradually within 10 min; HR increased from 73±3beats/min at 1 min to 180±23beats/min at 5min, and further to 243±20beats/min at 10min. The left ventricular systolic function fully recovered in all rats within 5min of ILP treatment (EF=70±3%, FS=40±3%). In CVT pretreated group, however, there was no recovery of cardiac function with ILP at CVT doses of 0.5, 0.25 and 0.125mg/kg within 10min of ILP therapy. ILP was only able to rescue Bupivacaine-induced cardiotoxicity at lowest dose of 0.0625 mg/kg CVT as cardiac function improved gradually within 10min (HR from 65 at 1min to ∼170min at 10 min; EF=∼55%, FS=∼29% at 10min and QRS from 33 ms at 1 min to 27 ms at 10 min). In conclusion CVT-4325 prevents intralipid rescue of Bupivacaine-induced cardiotoxicity in a dose dependant manner.