Edward A. Norfleet

Postconditioning Prevents Reperfusion Injury by Activating δ-Opioid Receptors

Background:While postconditioning has been proposed to protect the heart by targeting the mitochondrial permeability transition pore (mPTP), the detailed mechanism underlying this action is unknown. The authors hypothesized that postconditioning stimulates opioid receptors, which in turn protect the heart from reperfusion injury by targeting the mPTP. Methods:Rat hearts (both in vivo and in vitro) were subjected to 30 min of ischemia and 2 h of reperfusion. Postconditioning was elicited by six cycles of 10-s reperfusion and 10-s ischemia. To measure nitric oxide concentration, cardiomyocytes loaded with 4-amino-5-methylamino-2′,7′-difluorofluorescein were imaged using confocal microscopy. Mitochondrial membrane potential was determined by loading cardiomyocytes with tetramethylrhodamine ethyl ester. Results:In open chest rats, postconditioning reduced infarct size, an effect that was reversed by both naloxone and naltrindole. The antiinfarct effect of postconditioning was also blocked by the mPTP opener atractyloside. In isolated hearts, postconditioning reduced infarct size. Morphine mimicked postconditioning to reduce infarct size, which was abolished by both naltrindole and atractyloside. N-nitro-l-arginine methyl ester and guanylyl cyclase inhibitor 1H-[1,2,4] oxadiazolo [4,3-a] quinoxalin-1-one blocked the action of morphine. Further experiments showed that morphine produces nitric oxide in cardiomyocytes by activating &dgr;-opioid receptors. Moreover, morphine could prevent hydrogen peroxide–induced collapse of mitochondrial membrane potential in cardiomyocytes, which was reversed by naltrindole, N-nitro-l-arginine methyl ester, and the protein kinase G inhibitor KT5823. Conclusions:Postconditioning protects the heart by targeting the mPTP through activation of &dgr;-opioid receptors. The nitric oxide–cyclic guanosine monophosphate–protein kinase G pathway may account for the effect of postconditioning on the mPTP opening.

Mechanism for resveratrol-induced cardioprotection against reperfusion injury involves glycogen synthase kinase 3β and mitochondrial permeability transition pore

Resveratrol pretreatment can protect the heart by inducing pharmacological preconditioning. Whether resveratrol protects the heart when applied at reperfusion remains unknown. We examined the effect of resveratrol on myocardial infarct size when given at reperfusion and investigated the mechanism underlying the effect. Isolated rat hearts were subjected to 30 min ischemia followed by 2 h of reperfusion, and myocardial samples were collected from the risk zone for Western blot analysis. Mitochondrial swelling was spectrophotometrically measured as a decrease in absorbance at 520 nm (A(520)). Resveratrol reduced infarct size and prevented cardiac mitochondrial swelling. Resveratrol enhanced GSK-3beta phosphorylation upon reperfusion, an effect that was mediated by the cyclic guanosine monophosphate (cGMP)/protein kinase G (PKG) pathway. Resveratrol translocated GSK-3beta from cytosol to mitochondria via the cGMP/PKG pathway. Further studies showed that mitochondrial GSK-3beta was co-immunoprecipitated with cyclophilin D but not with VDAC (voltage dependent anion channel) or ANT (adenine nucleotide translocator). These data suggest that resveratrol prevents myocardial reperfusion injury presumably by targeting the mPTP through translocation of GSK-3beta from cytosol to mitochondria. Translocated GSK-3beta may ultimately interact with cyclophilin D to modulate the mPTP opening.

Exogenous zinc protects cardiac cells from reperfusion injury by targeting mitochondrial permeability transition pore through inactivation of glycogen synthase kinase-3β

The purpose of this study was to determine whether exogenous zinc prevents cardiac reperfusion injury by targeting the mitochondrial permeability transition pore (mPTP) via glycogen synthase kinase-3beta (GSK-3beta). The treatment of cardiac H9c2 cells with ZnCl2 (10 microM) in the presence of zinc ionophore pyrithione for 20 min significantly enhanced GSK-3beta phosphorylation at Ser9, indicating that exogenous zinc can inactivate GSK-3beta in H9c2 cells. The effect of zinc on GSK-3beta activity was blocked by the phosphatidylinositol 3-kinase (PI3K) inhibitor LY-294002 but not by the mammalian target of rapamycin (mTOR) inhibitor rapamycin or the PKC inhibitor chelerythrine, implying that PI3K but not mTOR or PKC accounts for the action of zinc. In support of this interpretation, zinc induced a significant increase in Akt but not mTOR phosphorylation. Further experiments found that zinc also increased mitochondrial GSK-3beta phosphorylation. This may indicate an involvement of the mitochondria in the action of zinc. The effect of zinc on mitochondrial GSK-3beta phosphorylation was not altered by the mitochondrial ATP-sensitive K+ channel blocker 5-hydroxydecanoic acid. Zinc applied at reperfusion reduced cell death in cells subjected to simulated ischemia/reperfusion, indicating that zinc can prevent reperfusion injury. However, zinc was not able to exert protection in cells transfected with the constitutively active GSK-3beta (GSK-3beta-S9A-HA) mutant, suggesting that zinc prevents reperfusion injury by inactivating GSK-3beta. Cells transfected with the catalytically inactive GSK-3beta (GSK-3beta-KM-HA) also revealed a significant decrease in cell death, strongly supporting the essential role of GSK-3beta inactivation in cardioprotection. Moreover, zinc prevented oxidant-induced mPTP opening through the inhibition of GSK-3beta. Taken together, these data suggest that zinc prevents reperfusion injury by modulating the mPTP opening through the inactivation of GSK-3beta. The PI3K/Akt signaling pathway is responsible for the inactivation of GSK-3beta by zinc.

Hyperkalemia and cardiovascular collapse after verapamil and dantrolene administration in swine

The cardiovascular and neuromuscular interactions of verapamil and dantrolene were evaluated in 20 chloralose-anesthetized swine. The animals were randomly divided into three groups. Group I, ten animals, received a bolus intravenous injection of 0.1 mg·kg−1 of verapamil followed by the continuous infusion of 5 μ·kg−1·min−1. This group was then randomly divided into two equal subgroups. Five of these animals, Group Ia, continued to receive the verapamil infusion alone. The other five animals, Group Ib, received dantrolene in incremental doses of 1.0, 3.3, and 5.6 mg·kg−1 while the verapamil infusion was continued. An additional group of five animals, Group II, received the same incremental doses of dantrolene but did not receive verapamil. Five control animals, Group III, received the α-chloralose anesthetic without dantrolene or verapamil. Neuromuscular function, as measured by twitch height, was affected only by dantrolene, which produced a dose-dependent depression. Verapamil resulted in initial decreases in heart rate, arterial blood pressure, cardiac output, left ventricular dP/dt, and an increase in PR interval. Dantrolene alone produced a mild increase in arterial blood pressure. Dantrolene administration to verapamil-pretreated animals resulted in a profound depression in cardiac function, marked elevation in serum K+ (8.0 ± 0.7 mEq·l−1), and no change in arterial pH (7.39 ± 0.02). Cardiac arrest preceded by complete atrioventricular heart block occurred in one animal before and in four animals after the final dantrolene dose was given to animals pretreated with verapamil. Although we cannot extrapolate data from our porcine model to humans, further studies are indicated to help evaluate a possible fatal drug interaction before verapamil and dantrolene are used concomitantly in a clinical setting

Comparative Cardiovascular Effects of Verapamil, Nifedipine, and Diltiazem during Halothane Anesthesia in Swine

&NA; The cardiovascular effects of the calcium channel blockers verapamil (V), nifedipine (N) and diltiazem (D) were compared in halothane‐anesthetized swine. Equipotent hypotensive doses of the three calcium channel blocking drugs were administered randomly by continuous infusion to three groups of six animals each to produce a uniform 25‐30% reduction in mean systemic arterial blood pressure (BP). An additional group of six animals received sodium nitroprusside (S) to demonstrate the effects of lowering blood pressure with a pure vasodilator on this experimental preparation. Hemodynamic indices monitored before and after drug administration included ECG, mean systemic and pulmonary artery blood pressure, mean central venous and pulmonary capillary wedge pressure, thermodilution cardiac output, left ventricular pressure, and left ventricular dP/dt. All four study drug infusions reduced BP an average of 28%. V and D reduced BP by decreasing cardiac output (41% and 42%, respectively) without affecting systemic vascular resistance. N and S produced hypotension by decreasing systemic vascular resistance (36% and 21%, respectively) without affecting cardiac output. D reduced heart rate (18%) and both D and V increased the PR interval (60% and 40%, respectively). Calcium chloride (20 mg • kg‐1 intravenous bolus) improved indices of myocardial contractility but did not affect drug‐induced changes in cardiac electrophysiology. These data demonstrate that in this halothane‐anesthetized swine model the administration of equihypotensive doses of verapamil or diltiazem has a more pronounced affect on cardiac conduction and myocardial contractility than does nifedipine, which predominantly reduces systemic vascular resistance with minimal effects on cardiac function.

Selective aortic arch perfusion during cardiac arrest: A new resuscitation technique

STUDY OBJECTIVES To demonstrate the technique of selective aortic arch perfusion during cardiac arrest and to observe the hemodynamic effects of volume infusion and aortic epinephrine administration. DESIGN Sequential series, nonrandomized, noncontrolled. TYPE OF PARTICIPANTS Fourteen mongrel dogs weighing 21 to 36 kg. INTERVENTIONS Animals had midaortic arch pressure, right atrial pressure, and descending aortic arch balloon occlusion catheters placed. After ten minutes of ventricular fibrillation, balloon inflation and aortic arch infusions were initiated as follows: group 1 (six), 30 mL/kg/min of 0.9% NaCl for two minutes; group 2 (four), 30 mL/kg/min of oxygenated lactated Ringers with 2 mg/L epinephrine for two minutes, followed by CPR; and group 3 (four), 20 mL/kg/min of oxygenated perfluorochemicals with 4 mg/L epinephrine for one minute, then CPR. MEASUREMENTS AND MAIN RESULTS Midaortic arch pressure, right atrial pressure, and coronary perfusion pressure each rose significantly in all groups. Midaortic arch pressure and coronary perfusion pressure increases were greater in groups 2 and 3 than in group 1. In groups 1 and 2, right atrial pressure increases at end-selective aortic arch perfusion were excessive as midaortic arch pressure and right atrial pressure increased linearly and similarly after 20 to 30 seconds. In groups 2 and 3, CPR-diastolic midaortic arch pressure and coronary perfusion pressure after selective aortic arch perfusion were good and similar to midaortic arch pressure and coronary perfusion pressure at end-selective aortic arch perfusion. CONCLUSION Selective aortic arch perfusion is technically feasible, but excessive right atrial pressure increases limit maximal infusion rates and volumes. Selective aortic arch perfusion infusates with epinephrine produce greater midaortic arch pressure and coronary perfusion pressure during infusion than infusate without epinephrine. Controlled studies are needed to determine if selective aortic arch perfusion improves resuscitation outcome.

Postoperative mortality after inpatient surgery: Incidence and risk factors.

Purpose: This study determined the incidence of and identified risk factors for 48 hour (h) and 30 day (d) postoperative mortality after inpatient operations. Methods: A retrospective cohort study was conducted using Anesthesiology’s Quality Indicator database as the main data source. The database was queried for data related to the surgical procedure, anesthetic care, perioperative adverse events, and birth/death/operation dates. The 48 h and 30 d cumulative incidence of postoperative mortality was calculated and data were analyzed using Chi-square or Fisher’s exact test and generalized estimating equations. Results: The 48 h and 30 d incidence of postoperative mortality was 0.57% and 2.1%, respectively. Higher American Society of Anesthesiologists physical status scores, extremes of age, emergencies, perioperative adverse events and postoperative Intensive Care Unit admission were identified as risk factors. The use of monitored anesthesia care or general anesthesia versus regional or combined anesthesia was a risk factor for 30 d postoperative mortality only. Time under anesthesia care, perioperative hypothermia, trauma, deliberate hypotension and invasive monitoring via arterial, pulmonary artery or cardiovascular catheters were not identified as risk factors. Conclusions: Our findings can be used to track postoperative mortality rates and to test preventative interventions at our institution and elsewhere.

Selective aortic arch perfusion during cardiac arrest: enhanced resuscitation using oxygenated perflubron emulsion, with and without aortic arch epinephrine.

STUDY OBJECTIVE To evaluate selective aortic arch perfusion (SAAP) with an oxygenated fluorocarbon emulsion, with and without aortic arch epinephrine during cardiac arrest. METHODS This randomized, controlled study, undertaken at a university research laboratory, involved 15 mixed-breed dogs. After 10 minutes of ventricular fibrillation and 30 seconds of CPR, the dogs were randomized to three groups, each comprising five dogs. Group 1 (controls) dogs were given CPR and intravenous epinephrine, .01 mg/kg, at 10.5 minutes and then every 3 minutes. Group 2 dogs (IVE-SAAP) were treated with CPR and intravenous epinephrine (IVE) in the same fashion as the control group but were also subjected to SAAP with 275 mL of oxygenated 60% wt/vol perflubron emulsion over 30 seconds. Group 3 dogs (AoE-SAAP) received the same treatment as the IVE-SAAP group, except that the first epinephrine dose was given intraaortically. RESULTS Coronary perfusion pressure (CPP) increased during SAAP in both the IVE-SAAP and AoE-SAAP groups but was greater in the AoE-SAAP group. CPR diastolic CPP after SAAP was significantly greater in the AoE-SAAP group than in the control group. Return of spontaneous circulation (ROSC) occurred in two control dogs, all five IVE-SAAP dogs, and all five AoE-SAAP dogs. The time elapsed from the initiation of CPR to ROSC was 6.1 +/- 1.9 minutes in the AoE-SAAP group, compared with 11.0 +/- 5.8 minutes in the IVE-SAAP group. CONCLUSION SAAP with oxygenated perflubron emulsion improved ROSC, both with and without aortic arch epinephrine. The combination of SAAP with perflubron emulsion and aortic arch epinephrine resulted in higher CPP and more rapid ROSC.

Aortic arch versus central venous epinephrine during CPR

STUDY OBJECTIVE To determine if delivery of epinephrine to the peripheral arterial system by an aortic arch catheter is more effective than central venous epinephrine administration during cardiac resuscitation. DESIGN Randomized, nonblinded, controlled trial. TYPE OF PARTICIPANTS Sixteen mongrel canines (25 to 31 kg). INTERVENTIONS Animals had aortic arch pressure, and right atrial pressure, superior vena cava infusion, and descending aortic arch infusion catheters placed using fluoroscopy. After ten minutes of ventricular fibrillation, three DC countershocks were delivered over one minute. If unsuccessful, CPR at 120 compressions per minute was begun, and at 60 seconds of CPR, epinephrine (1 mg/50 mL normal saline) was administered either through the superior vena cava or the aortic arch catheter followed by one more minute of CPR. Defibrillation then was attempted and, if unsuccessful, further resuscitative efforts followed advanced cardiac life support guidelines, except route and dose of epinephrine remained the same. MEASUREMENTS AND MAIN RESULTS Aortic arch pressure, right atrial pressure, and coronary perfusion pressure (diastolic aortic arch pressure minus diastolic right atrial pressure) were recorded continuously. Aortic arch pressure and coronary perfusion pressure increased more rapidly and to a greater magnitude with aortic arch-epinephrine than superior vena cava-epinephrine. Coronary perfusion pressure doubled by ten seconds in seven of eight in the aortic arch-epinephrine group versus none in the superior vena cava-epinephrine group. Aortic arch pressure and coronary perfusion pressure increases consistently plateaued within 60 seconds after aortic arch-epinephrine but not after superior vena cava-epinephrine. Return of spontaneous circulation was faster (P < .05) in the aortic arch-epinephrine group. Maximal coronary perfusion pressure after epinephrine correlated with the coronary perfusion pressure immediately before epinephrine administration in both groups, but more strongly in the aortic arch-epinephrine group (P = .0001). CONCLUSION For an equivalent dose of epinephrine, aortic arch administration produces a more rapid response and more rapid peak effect than central venous administration. The combination of aortic arch-epinephrine administration and aortic pressure monitoring may be useful when initial standard resuscitative measures have not been successful.

Subcutaneous emphysema producing airway compromise after anesthesia for reduction of a mandibular fracture: A case report and review of the literature

Subcutaneous emphysema can occur as the result of trauma, surgery, and anesthesia. A case is presented of extensive subcutaneous emphysema after anesthesia for oral surgical reduction of a mandibular fracture. A discussion of the diagnosis, pathophysiology, and treatment of subcutaneous emphysema follows.