The Effect of Phenylephrine on Cardiac Performance and Myocardial Oxygen Balance in Resuscitation from Hemorrhagic Shock / 대한마취과학회지

BACKGROUND: The issue of using phenylephrine in hemorrhagic shock treatment has been controversial because it is known that phenylephrine improves the tissue perfusion by increasing arterial blood pressure but deteriorates the myocardium by increasing afterload and decreasing myocardial oxygen delivery via coronary vasoconstriction. This study was aimed to assess the effects of phenylephrine on hemodynamic variables, cardiac performance, and myocardial oxygen balance in resuscitation from hemorrhagic shock. METHODS: Twenty anesthetized dogs were randomly divided into phenylephrine group and control group. After inducing hemorrhagic shock, resuscitation was done with phenylephrine and 0.9% normal saline respectively. We measured hemodynamic indices, blood gas parameter and cardiac enzymes which indicate myocardial demage. RESULTS: In both groups, cardiac output and hemodynamic indices improved. In phenylephrine group, the systemic oxygen delivery and consumption was much higher and the myocardial oxygen extraction ratio was maintained at the lower level than the control group. In addition, the CK-MB was higher at the early phase of resuscitation and the troponin T was also higher than the control group during the whole period of resuscitation. Creatine kinase-MB increased during early resuscitation in phenylephrine group but kept decreasing after that and there's no difference between two groups. Troponin T was higher in the phenylephrine group after resuscitation. CONCLUSIONS: We concluded that phenylephrine improves myocardial oxygen balance and contractility without serious myocardial demage during resuscitation from hemorrhagic shock.

The effects of Shenfu injection on brain injury in patients undergoing valve replacement / 重庆医科大学学报

Objective:To investigate the effects of Shenfu injection on cerebral oxygen balance and cerebral ischemia-reperfusion injury in patients undergoing valve replacement during cardiopulmonary bypass,in order to Explore its efficacy and find reasonable route of administration. Methods: 32 patients undergoing valve replacement,aged 25～54,with the heart function of 2～3 level,were randomly divided into four groups with eight in each. Patients in group E1 received SFI 1.5 ml/kg before blocking of the aorta;Patients in group E2 received SFI 1.5 ml/kg after opening of the aorta;Patients in group E3received SFI 0.75 ml/kg before blocking and after opening the aorta,too. Patients in group C received 0.9% NaCl. Blood samples were taken from internal jugular vein and arteria radialis after trachea cannula(T1),10 min after CPB(T2),cooling stability stage(T3),recovery temperature to 33℃(T4),the end of CPB(T5) and 1 hour after the end of CPB(T6)for blood gas analysis.Then,Plasma S100? protein concentration、MDA、Glu and the activity of SOD in jugular vein bulb were determined. Results: The CERO2,SjvO2 changes in Group E1,E2,E3 were stable,moreover,SjvO2 was significantly higher than that in group C (P 0.05),In group E3,SOD had the highest activity at T6(P

Effects of Amrinone and Dobutamine on Regional Myocardial Function and Oxygen Balance in Normal and Stunned Myocardium in Dogs / 대한구급학회지

BACKGROUND: We examined the effects of amrinone and dobutamine on regional mechanical function, coronary blood flow (CBF), and myocardial oxygen consumption (MVO2) in normal and stunned myocardium in an open-chest canine model. METHODS: Dogs were instrumented to measure aortic and left ventricular pressures, pulmonary and left anterior descending (LAD) coronary blood flows, and subendocardial segment length in the region supplied by LAD. Incremental doses of either amrinone (2~10microgram/ml of LAD flow, n=13) or dobutamine (0.05~0.375microgram/ml of LAD flow, n=14) were directly infused into a coronary artery before (normal) and after a 15 min of LAD occlusion and subsequent 30 min-reperfusion (stunned). Percent segment shortening (%SS) and percent post-systolic shortening (%PSS) were evaluated. Myocardial extraction of oxygen (EO2) and lactate (Elac) was calculated. RESULTS: Amrinone or dobutamine in the normal myocardium caused dose-dependent increases in %SS that were comparable (range, 20~40%) but had no effect on %PSS. MVO2 increased in parallel with %SS for both amrinone and dobutamine. With amrinone, CBF increased more than MVO2, resulting in a modest decrease in EO2, whereas with dobutamine, CBF increased in proportion to MVO2, resulting in no change in EO2. After the ischemia and reperfusion, %SS and Elac were reduced, but similar %SS and CBF responses to both agents were observed, except that both agents caused progressive reductions of %PSS. CONCLUSIONS: These results indicate that both amrinone and dobutamine exert positive inotropic effects in normal and stunned canine myocardium. It is also indicated that amrinone causes direct coronary vasodilation, which is not affected by ischemia and reperfusion, while dobutamine has no direct effect on coronary vascular tone in either normal or stunned myocardium.

Effects of Amrinone on Regional Myocardial Function and Oxygen Balance in Stunned Myocardium in Dogs / 대한마취과학회지

BACKGROUND: Brief myocardial ischaemia has been demonstrated to result in mechanical and coronary endothelial dysfunction. We examined whether the mechanical and vascular responses to amrinone are altered in the postischaemic, reperfused myocardium. The effects of amrinone were compared with those of dobutamine. METHODS: In an open-chest canine model, coronary blood flow (CBF), myocardial oxygen consumption (MVO2), and regional mechanical function in response to either amrinone (2, 5, 7.5, and 10 ng/mL of CBF) or dobutamine (0.05, 0.125, 0.25, 0.375, and 10ng/mL of CBF) directly infused into the left anterior descending (LAD) artery were determined before (normal) and 30 min after 15-min- period of LAD occlusion (stunned). Percent segment shortening (%SS), peak segment lengthening rate (dL/dt(max)), and percent post-systolic shortening (%PSS) in the LAD territory was determined using ultrasonic crystals and CBF using Doppler transducer. Myocardial extractions of oxygen (EO2) and lactate (Elac) were calculated. RESULTS: Both amrinone and dobutamine in the normal myocardium caused a dose-dependent increase in mechanical functions (%SS and dL/dt(max)) and MVO2 that were comparable (range, 20 40%), but they had no effects on %PSS. Amrinone caused an increase of CBF in excess of MVO2, resulting in a modest decrease in EO2, whereas dobutamine increased CBF in proportion to MVO2, resulting in no changes in EO2. The ischemia and reperfusion insult reduced %SS, dL/dt(max), and Elac, while it did not affect mechanical (%SS and dL/dt(max)) and CBF responses to either agent, except for progressive reductions of %PSS. CONCLUSIONS: These results indicate that amrinone, similar to dobutamine, exert positive inotropic and lusitropic effects in normal and stunned canine myocardium. It is also indicated that amrinone causes direct coronary vasodilation, which is not affected by an ischemia and reperfusion insult.

Effects of Blood-Brain Barrier Disruption on Cerebral Oxygen Balance / 대한구급학회지

BACKGOUND: Disruption of the blood-brain barrier (BBB) can alter the internal milieu and may increase the release of excitatory amino acid neurotransmitters or catecholamines, which may affect metabolic rate or coupling. This study was performed to evaluate whether disruption of BBB by unilateral intracarotid injection of hyperosmolar mannitol would alter oxygen supply/consumption balance in the ipsilateral cortex. METHODS: Rats were anesthetized with 1.4% isoflurane using mechanical ventilation via tracheostomy. 25% mannitol was administered at a rate of 0.25 mlxkg-1s-1 for 30 s through unilateral internal carotid artery. The BBB transfer coefficient (Ki) of 14C-alpha-aminoisobutyric acid was measured in one group (N=7) after administering mannitol. Regional cerebral blood flow (rCBF), regional arterial and venous O2 saturation and O2 consumption were measured in another group using a 14C-iodoantipyrine and microspectrophotometry (N=7). RESULTS: Vital signs were similar before and after administering mannitol. Ki was significantly higher in the ipsilateral cortex (IC) than in the contralateral cortex (CC), (22.3+/-8.4 vs 4.4+/-1.1 microliterxg-1min-1). rCBF was similar between IC (105+/-21 mlxg-1min-1) and the CC (93+/-20). Venous O2 saturation was lower in the IC (43+/-7%) than in the CC (55+/-4). O2 consumption was higher in the IC (9.6+/-3.0 mlx100 g-1min-1) than in the CC (6.7+/-1.5). CONCLUSIONS: Our data suggested that increasing permeability of the BBB increased cerebral O2 consumption and deteriorated cerebral oxygen balance.

Effects of Esmolol-induced Hypotension under Acute Normovolemic Hemodilution on the Cardiovascular System and Systemic Oxygen Balance in Dogs / 대한마취과학회지

BACKGREOUND: Acute normovolemic hemodilution (ANH) is one of the methods of autologous transfusion drawing much attention recently. It is economical and easy to apply to many surgeries requiring multiple transfusions. When used as a drug for induced hypotension, esmolol can avoid many drawbacks of sodium nitroprusside and reduce the amount of intraoperative bleeding with better operative field. Considering recent trend of combining ANH and induced hypotension to increase the success rate of autotransfusion, esmolol-induced hypotension with ANH will be used more frequently in the future. However, tissue oxygen balance may be in danger because of decreased tissue perfusion pressure by induced hypotension and reduced arterial oxygen content by ANH. Thus it is necessary to evaluate effects of induced hypotension combined with ANH on cardiovascular system and systemic oxygen balance. METHODS: In 8 mongrel dogs anesthetized with N2O-O2-enflurane and paralyzed with vecuronium, ANH was performed up to half of initial level of hemoglobin with isovolemic pentastarch infusion, and then mean arterial pressure (MAP) was lowered by 30% of the initial value by intravenous administration of esmolol. Various hemodynamic parameters were measured before and after ANH and 15, 30, 60 and 90 minutes after induction of hypotension and 30 minutes after the end of hypotension. RESULTS: Heart rate began to decrease after ANH and showed significant decrease at 60 and 90 minutes after hypotension compared with initial value. Central venous pressure increased significantly after ANH and hypotension. Pulmonary arterial pressure showed significant increase at 15 and 90 minutes after hypotension. Cardiac output was increased markedly by ANH but began to decrease after hypotension and showed significant decrease at 60 minutes after hypotension. Systemic vascular resistance showed significant decrease after ANH, 15 minutes after hypotension and 30 minutes after discontinuation ofesmolol. Pulmonary capillary wedge pressure and pulmonary vascular resistance showed no significant change. Oxygen flux was decreased markedly by esmolol but recovered after discontinuation of esmolol. Oxygen consumption was maintained throughout the study. Oxygen extraction ratio was increased dly after hypotension. There were no acidemia and hypoxemia throughout the study. CONCLUSION: In conclusion, the results of this study suggest that tissue oxygen delivery might be decreased by anemia but that systemic oxygen balance might be preserved by ANH and induced hypotension within the range used in this study.

Effects of Enflurane on the Left Ventricular Function in Isolated Diltiazem-Pretreated Rat Heart / 대한마취과학회지

BACKGROUND: Calcium channel blockers and volatile anesthetics have depressant effects on cardiac function. Both of them appear to exert, qualitatively and quantitatively, different effects on myocardial contractility, coronary flow, and myocardial oxygen balance. The aim of this study was to examine the direct cardiac effects of the enflurane in the presence of diltiazem. METHODS: Isolated Sprague-Dawley rat hearts (N=45) were perfused at constant pressure with oxygenated Modified-Krebs solution (pH 7.4, 37oC). Isovolumetric left ventricular pressure (LVP) and dP/dt were measured via a latex balloon and transducer. Also, coronary flow and oxygen tensions at the coronary inflow and outflow were measured. After stabilization period, all hearts were subjected to the application with diltiazem (100 ng/ml). Thereafter, they were subdivided into three groups; group 1, 2, 3. Groups subjected to the combination of diltiazem (100 ng/ml) with enflurane 1.1, 2.2, or 3.3 vol%, respectively. RESULTS: After the application of diltiazem, myocardial contractility and heart rate were significantly decreased, and coronary flow were significantly increased. The combination of diltiazem with enflurane depressed myocardial contractility, heart rate, myocardial O2 consumption, and percentage of O2 extraction more than diltiazem alone, and their effects were dependent on the concentration of enflurane. However, there was no difference in the change of coronary flow and oxygen delivery between diltiazem and the combination of diltiazem with enflurane. CONCLUSIONS: These in vitro findings demonstrate that the combination of diltiazem with enflurane shows greater direct negative inotropic and negative chronotropic effect, and is associated with less attenuation of coronary autoregulation, but with a larger reduction in O2 utilization. The present results suggest that high enflurane anesthesia in the diltiazem-pretreated patients could result in profound cardiac depression.

The Effects of Nitric Oxide on Oxygen Balance in Cerebral Ischemia / 대한구급학회지

Bockground: Nitric oxide (NO) is an important regulator of blood flow and also works as a neuronal messenger via cyclic GMP. Recent studies regarding the therapeutic utility of nitric oxide synthase (NOS) inhibitors in reducing ischemia-induced neuronal damage are very controversial. The possible neuroprotective effect of NO or NOS inhibitors in ischemic neuronal damage could occur at the vascular and or neuronal level. This study investigated whether the NOS inhibitor, NG-nitro-L-arginine-methyl ester (L-NAME) would alter oxygen balance in ischemic cerebrocortex of isoflurane-anesthetized rats. METHODS: Fifteen minutes after middle cerebral artery occlusion, L-NAME (1.5 mgxmin-1kg-1) was infused intravenously to the L-NAME group (n=14), and normal saline was given to the control group (n=14) for 45 minutes. Regional cerebral blood flow was determined with [14C]iodoantipyrine, and arterial and venous oxygen saturations were determined by microspectrophotometry. RESULTS: Regional cerebral blood flow of the ischemic cortex was significantly lower than that of the contralateral cortex in both groups. In the control group, ischemic cortex; 55+/-13, contralateral cortex; 110+/-29 mlxmin-1100 g-1, and in the L-NAME group, ischemic cortex; 35+/-13, contralateral cortex; 90+/-24 mlxmin-1100 g-1. Compared with the blood flow in the ischemic cortex of the control group, L-NAME significantly reduced ischemic blood flow by 36%. Venous oxygen saturation was significantly increased in the ischemic cortex (41+/-1% in control, 44+/-3% in L-NAME) but decreased in the contralateral cortex (65+/-3% in control, 61+/-3% in L-NAME) by L-NAME. Ischemic cortical oxygen consumption in the L-NAME group was 39% lower than that in the corresponding control group, whereas the difference was only 11% in the contralateral sides between groups. The ratio of oxygen supply to consumption was lower in the ischemic than in the nonischemic regions in both groups. In the ischemic cortex, this ratio was significantly lower in the control group (1.7+/-0.1) than in the L-NAME group (1.9+/-0.1). In contrast, the ratio tended to be decreased by L-NAME in nonischemic regions. CONCLUSIONS: These observations suggest that despite a decrease in cerebral blood flow, inhibition of nitric oxide synthesis mildly improves the oxygen supply and consumption balance in the ischemic cortex.