Hemolytic Uremic Syndrome Occurred after Esophagectomy: A Case Report / 대한구급학회지

Hemolytic uremic syndrome is an unusual and uncommon disease in adults but more common in children, which is defined by the triad of acute renal failure, thrombocytopenia, and microangiopathic hemolytic anemia. We report a 64-year-old man who developed hemolytic uremic syndrome after esophagectomy and esophagogastrostomy due to esophageal cancer. We treated him using continuous renal replacement therapy and plasmapheresis with large volume fresh frozen plasma transfusion for 9 days. We could not find the cause of hemolytic uremic syndrome, and so finally concluded that it is idiopathic. Bleeding continuously without a particular reason after an operation, it needs an early diagnosis and treatment with considering a possibility of the hemolytic uremic syndrome.

Effects of Remifentanil and Alfentanil on Cardiovascular Responses to Laryngoscopy and Double-lumen Endobronchial Intubation / 대한마취과학회지

BACKGROUND: This study examined the cardiovascular responses to double-lumen endobronchial intubation during rapid sequence induction of anesthesia, and compared the effect of remifentanil and alfentanil in a randomized, double-blind, placebo-controlled study in three groups of 20 elderly patients each. METHODS: Anesthesia was induced with intravenous thiopental (4-6 mg/kg) immediately followed by either remifentanil 2 microgram/kg, alfentanil 30microgram/kg, or saline (placebo) given over 30 sec. Succinylcholine 1.5 mg/kg was given for neuromuscular block. The laryngoscopy and intubation were performed 60 sec later. RESULTS: The intubation significantly increased systolic arterial pressure (SAP) and heart rate (HR) in all groups. The maximum pressure changes in the remifentanil and alfentanil groups (36 +/- 26 and 33 +/- 30 mmHg, respectively) were significantly lower than the 83 +/- 35 mmHg in the control group. The maximum HR in the remifentanil (77 +/- 13 bpm) and alfentanil (80 +/- 13 bpm) groups was lower when compared to controls (93 +/- 11 bpm). The norepinephrine and epinephrine concentrations increased after intubation in the control group but remained unaltered in both the alfentanil and remifentanil groups. There were no significant differences between the remifentanil and alfentanil groups in HR, SAP or catecholamines at any time. Five patients in the remifentanil group and three in the alfentanil group received ephedrine for hypotension. CONCLUSIONS: Endobronchial intubation elicited a significant pressor response, and that both remifentanil and alfentanil similarly attenuated the pressor response. However, the incidence of hypotension confirms that both drugs should be used with caution in elderly patients.

The Effect of Doxapram Hydrochloride on the Ventilation Responses during Total Intravenous Anesthesia by Laryngeal Mask Airway / 대한마취과학회지

BACKGROUND: Intravenous anesthetics causes depression of ventilatory response to hypercapnea. Doxapram stimulates ventilation via peripheral and central chemoreceptors. This study was aimed to evaluate the effect of doxapram on ventilation during total intravenous anesthesia (TIVA). METHODS: 60 patients undergoing operation under spontaneous ventilation via laryngeal mask airwaywere randomly divided into 3 groups: Control group received 5% dextrous infusion, D-2 group received doxapram injection of 1 mg/kg followed by continuous infusion of 2 mg/kg/hr, and D-4 group received doxapram injection of 2 mg/kg followed by continuous infusion of 4 mg/kg/hr. Anesthesia was induced and maintained with propofol and remifentanil. Respiratory rate, tidal volume (VT) and arterial carbon dioxide tension (PaCO2) were measured before and 15 min after induction of anesthesia, 0(15 min after start of operation), 1, 2, 3, 5, 15, 30, 45, and 60 min after start of doxapram infusion during TIVA. RESULTS: VT was significantly increased 1 min after start of doxapram infusion and returned to the value of pre-doxapram infusion immediately. In D-4 group, VT was significantly (P < 0.05) increased again 5 min after doxapram infusion compared with the value of pre-doxapram infusion and control group. PaCO2 was decreased 1 min after start of doxapram infusion and then increased again 2 min after doxapram infusion. In D-4 group, the degree of increase of PaCO2 was significantly (P < 0.05) less than those of D-2 group. CONCLUSIONS: Doxapram injection of 2 mg/kg followed by continuous infusion of 4 mg/kg/hr improved the depression of ventilatory response during TIVA.

The Role of Adrenergic and Cholinergic Receptors on the Antinociception of Intrathecal Zaprinast in the Formalin Test of Rats / 대한마취과학회지

BACKGROUND: Spinal zaprinast, phospodiesterase inhibitor, has been shown to have an antinociception through an increase of cGMP. The aim of this study was to examine the role of spinal adrenergic and cholinergic receptors on the antinociceptive action of intrathecal zaprinast. METHODS: Rats were implanted with lumbar intrathecal catheters. After formalin injection, formalin-induced nociceptive behavior (flinching response) was observed for 60 min. After observing the effect of intrathecal zaprinast, antagonism of intrathecal prazosin, yohimbine, atropine and mecamylamine for the effect of zaprinast were evaluated. RESULTS: Intrathecal zaprinast produced a dose-dependent suppression of formalin-induced flinches in both phases of the formalin test. Intrathecal prazosin reversed the antinociception of zaprinast in phase 2, but not phase 1. Intrathecal yohimbine reversed the antinociception of zaprinast in both phases. Neither atropine nor mecamylamine reversed the antinocicetive action of zaprinast. CONCLUSIONS: Intrathecal zaprinast is against the nociceptive state evoked by formalin stimulus. Alpha 2 or alpha 1 adrenergic receptor, but not cholinergic receptors, may be related to the action of zaprinast in the spinal cord.

Optimal Dose of Remifentanil to Blunt Hemodynamic Response to Laryngoscopy and Endotracheal Intubation during Induction of Anesthesia with Propofol / 대한마취과학회지

BACKGROUND: A laryngoscopy and endotracheal intubation cause an increase in the blood pressure and heart rate. Remifentanil is an opioid that is often used to reduce the hemodynamic responses after tracheal intubation. This study evaluated the effect of three bolus doses of remifentanil on the hemodynamic responses to a laryngoscopy and tracheal intubation. METHODS: Eighty patients, aged 35-65 years, with an ASA physical status of I and II were randomly divided into four groups containing 20 patients each. Anesthesia was induced with propofol 2 mg/kg followed 30 s later by saline (control) or remifentanil 0.5 (R0.5), 1 (R1) or 2 (R2)microgram/kg given as a bolus over a 30 s period. A laryngoscopy and tracheal intubation were performed 90 s later (corresponding to 3 min after induction), and anesthesia was maintained using 2% sevoflurane and 50% nitrous oxide in oxygen. Rocuronium 1 mg/kg was given as a neuromuscular block. The systolic arterial blood pressure (SAP) and heart rate (HR) were recorded until 5 min after intubation. RESULTS: In all groups, the SAP decreased after inducing anesthesia and then increased after intubation in all groups (P < 0.05), but the maximum increases (46, 15, and 9 mmHg in the R0.5, R1, and R2 groups, respectively) after intubation were lower in the remifentanil groups than that of the control group (73 mmHg) (P < 0.05). The HR decreased in the remifentanil groups while it remained stable in the controls after the induction of anesthesia. However, it increased after intubation in all groups. The mean maximum HR (83, 71, and 69 bpm in the R0.5, R1 and R2 groups, respectively) was significantly lower in the remifentanil groups than that in the controls (98 bpm) (P < 0.05). All remifentanil doses significantly attenuated the pressor and tachycardiac responses (P < 0.05). CONCLUSIONS: All remifentanil doses were effective in controlling the pressor and tachycardiac response to endotracheal intubation in patients in whom anesthesia was induced with propofol. However, the use of the 1 and 2microgram/kg dose was associated with a decrease in the SAP to less than 85 mm Hg in 10 patients (50%) each. Therefore, 0.5microgram/kg appears to be the optimal dose to attenuate the cardiovascular responses to endotracheal intubation in patients.

Optimal Dose of Remifentanil to Blunt Hemodynamic Response to Laryngoscopy and Endotracheal Intubation during Induction of Anesthesia with Propofol / 대한마취과학회지

BACKGROUND: A laryngoscopy and endotracheal intubation cause an increase in the blood pressure and heart rate. Remifentanil is an opioid that is often used to reduce the hemodynamic responses after tracheal intubation. This study evaluated the effect of three bolus doses of remifentanil on the hemodynamic responses to a laryngoscopy and tracheal intubation. METHODS: Eighty patients, aged 35-65 years, with an ASA physical status of I and II were randomly divided into four groups containing 20 patients each. Anesthesia was induced with propofol 2 mg/kg followed 30 s later by saline (control) or remifentanil 0.5 (R0.5), 1 (R1) or 2 (R2)microgram/kg given as a bolus over a 30 s period. A laryngoscopy and tracheal intubation were performed 90 s later (corresponding to 3 min after induction), and anesthesia was maintained using 2% sevoflurane and 50% nitrous oxide in oxygen. Rocuronium 1 mg/kg was given as a neuromuscular block. The systolic arterial blood pressure (SAP) and heart rate (HR) were recorded until 5 min after intubation. RESULTS: In all groups, the SAP decreased after inducing anesthesia and then increased after intubation in all groups (P < 0.05), but the maximum increases (46, 15, and 9 mmHg in the R0.5, R1, and R2 groups, respectively) after intubation were lower in the remifentanil groups than that of the control group (73 mmHg) (P < 0.05). The HR decreased in the remifentanil groups while it remained stable in the controls after the induction of anesthesia. However, it increased after intubation in all groups. The mean maximum HR (83, 71, and 69 bpm in the R0.5, R1 and R2 groups, respectively) was significantly lower in the remifentanil groups than that in the controls (98 bpm) (P < 0.05). All remifentanil doses significantly attenuated the pressor and tachycardiac responses (P < 0.05). CONCLUSIONS: All remifentanil doses were effective in controlling the pressor and tachycardiac response to endotracheal intubation in patients in whom anesthesia was induced with propofol. However, the use of the 1 and 2microgram/kg dose was associated with a decrease in the SAP to less than 85 mm Hg in 10 patients (50%) each. Therefore, 0.5microgram/kg appears to be the optimal dose to attenuate the cardiovascular responses to endotracheal intubation in patients.

Anesthetic Experience of Patients with a Congenital Tracheal Bronchus: A report of two cases / 대한마취과학회지

A tracheal bronchus is an aberrant, accessory or ectopic bronchus arising almost always from the right lateral wall of the trachea at the level less than 2 cm above the carina. An endotracheal or endobronchial tube can obstruct or migrate into a tracheal bronchus, resulting in pulmonary atelectasis, hypoxemia, or both during general anesthesia. We report two patients in whom the anomalous tracheal bronchus had been surgically resected under general anesthesia. The anomaly was identified before surgery in each patient and anesthesia was uneventful.

Evaluation for the Effects of Intrathecal Sildenafil on the Formalin- and Thermal-induced Nociception of Rats / 대한통증학회지

BACKGROUND: Cyclic guanosine monophosphate (cGMP) plays an important role in the modulation of nociception. Although local sildenafil produces antinociception, by increasing cGMP through the inhibition of phosphodiesterase 5, the effect of spinal sildenafil has not been determined. The authors evaluated the effects of intrathecal sildenafil on the nociceptive behavior evoked by formalin injection and thermal stimulation. METHODS: Lumbar intrathecal catheters were implanted into rats, with formalin and Hot-Box tests used as nociceptive models. The formalin-induced nociceptive behavior (flinching response) and withdrawal latency to radiant heat were measured, and the general behaviors also observed. RESULTS: The intrathecal administration of sildenafil produced dose-dependent suppression of the flinches in both phases in the formalin test, and increased the withdrawal latency in the Hot-Box test. No abnormal behaviors were noted. CONCLUSIONS: Sildenafil, an inhibitor of phosphodiesterase 5, is active against the nociceptive state evoked in the spinal cord by formalin and thermal stimulations. Accordingly, spinal sildenafil may be useful in the management of pain.

Antinociceptive Effect of the Intrathecal Phosphodiesterase Inhibitor, Zaprinast, in a Rat Formalin Test / 대한통증학회지

BACKGROUND: Cyclic guanosine monophosphate (cGMP) and opioid receptors are involved in the modulation of nociception. Although the opioid receptors agonists are active in pain, the effect of an phospodiesterase inhibitor (zaprinast) for increasing the level of cGMP has not been thoroughly investigated at the spinal level. This study examined the effects of intrathecal zaprinast and morphine in a nociceptive test and we also examined the nature of the pharmacological interaction after the coadministration of zaprinast with morphine. The role of the nitric oxide(NO)-cGMP-potassium channel pathway on the effect of zaprinast was further clarified. METHODS: Catheters were inserted into the intrathecal space of male SD rats. For the induction of pain, 50microliter of 5% formalin solution was applied to the hindpaw. Isobolographic analysis was used for the evaluation of the drug interaction between zaprinast and morphine. Furthermore, NO synthase inhibitor (L-NMMA), guanylyl cyclase inhibitor (ODQ) or a potassium channel blocker (glibenclamide) were intrathecally administered to verify the involvement of the NO-cGMP-potassium channel pathway on the antinociception effect of zaprinast. RESULTS: Both zaprinast and morphine produced an antinociceptive effect during phase 1 and phase 2 in the formalin test. Isobolographic analysis revealed a synergistic interaction after the intrathecal administration of the zaprinast-morphine mixture in both phases. Intrathecal L-NMMA, ODQ and glibenclamide did not reverse the antinociception of zaprinast in either phase. CONCLUSIONS: These results suggest that zaprinast, morphine and the mixture of the two drugs are effective against acute pain and they facilitated pain state at the spinal level. Thus, the spinal combination of zaprinast with morphine may be useful for the management of pain. However, the NO-sensitive cGMP-potassium channel pathway did not contribute to the antinocieptive mechanism of zaprinast in the spinal cord.

Assessment for the Role of Serotonin Receptor Subtype 3 for the Analgesic Action of Morphine at the Spinal Level / 대한통증학회지

BACKGROUND: Serotonin 3 receptor is involved in the modulation of nociceptive transmission in the spinal cord. The serotonin 3 receptor antagonist has been used for the management of opioid-induced nausea and vomiting. The aim of this study was to examine whether the analgesic effect of morphine is antagonized by serotonin 3 receptor antagonists at the spinal level. METHODS: Rats were implanted with lumbar intrathecal catheters. For nociception, a formalin solution (5%, 50microliter) was injected into the hind paw of male Sprague-Dawley rats. To determine whether the effect of intrathecal morphine was mediated via serotonin 3 receptors, serotonin 3 receptor antagonists were intrathecally administered 10 min prior to the morphine delivery. Following the formalin injection, formalin-induced nociceptive behavior (flinching response) was observed for 60 min. RESULTS: Intrathecal morphine produced a dose-dependent suppression of the flinches in both phases during the formalin test. The analgesic action of morphine was not reversed by serotonin 3 receptor antagonists (LY-278, 584, ondansetron), which had little per se effect on the formalin-induced nociception. CONCLUSIONS: Spinal serotonin 3 receptors may not be involved in the analgesia of morphine on a nociceptive state evoked by a formalin stimulus.

Study for the Antinociceptive Effect and Toxicity of Chronic Intrathecal Infusion of Cannabinoids in Rats / 대한통증학회지

BACKGROUND: Cannabinoids have shown antinociceptive action. The aims of this study were to examine the effect of chronic infusion of a cannabinoids receptors agonist (WIN 55, 212-2) for thermal nociception at the spinal level, and to also observe the development of toxicity. METHODS: Male Sprague-Dawley rats were implanted with lumbar intrathecal catheters with the nociceptive response (withdrawal response latency) determined by exposing the plantar surface of the hindpaw to radiant heat. Initially, the effect of intrathecal WIN 55, 212-2 was evaluated followed by the change in the effect at 1, 2, 3 and 4 weeks after repeated infusion. Finally, the histopathological findings were assessed 1 and 4 weeks following the infusion of WIN 55, 212-2. RESULTS: Intrathecal WIN 55, 212-2 was found to produce a limited antinociception during the thermal test. %MPE of WIN 55, 212-2 at 1, 2, 3, and 4 weeks after infusion was not different from each other. No abnormal pathological findings were observed following a chronic intrathecal infusion of WIN 55, 212-2. CONCLUSIONS: WIN 55, 212-2, a cannabinoids receptors agonist, may be useful in the management of thermal nociception, without changing the effectiveness or causing the toxicity following a chronic infusion at the spinal level.

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 a Combination of Nicardipine and Alfentanil on Hemodynamic Response after Endotracheal Intubation / 대한마취과학회지

BACKGROUND: The present study was designed to examine the effect of a combination of nicardipine and low dose alfentanil on hemodynamic response following endotracheal intubation. METHODS: Thirty patients (20-65 yr) were assigned randomly to receive nicardipine (N: 20microgram/kg) or a combination of nicardipine and low dose of alfentanil (NA: nicardipine 10microgram/kg and alfentanil 5microgram/kg). Systolic blood pressure (SBP), diastolic blood pressure (DBP) and heart rate (HR) were measured at 1, 2 min after anesthetic induction, and every minute for 5 min after intubation. RESULTS: The magnitude of increases in SBP and DBP were non-significantly smaller in the NA group than in the N group, and increase in HR were significantly lower in the NA group. CONCLUSIONS: These results indicate that the nicardipine with alfentanil combination was more effective than nicardipine alone at attenuating blood pressure and heart rate increases following intubation.

Effect of Zaprinast, a Phosphodiesterse Inhibitor, on Formalin-induced Nociception and Hemodynamics in the Rat Spinal Cord / 대한마취과학회지

BACKGROUND: Cyclic guanosine monophosphate (cGMP) is involved in antinociception and vascular relaxation. The effects of zaprinast, which increases the level of cGMP by inhibiting phosphodiesterase, in the spinal cord have not been reported. The aims of this study were to evaluate the effects of intrathecal zaprinast on stimulus evoked by formalin injection, and to observe hemodynamic change in the absence of formalin stimulation. METHODS: Rats were implanted with lumbar intrathecal catheters. Intrathecal zaprinast was administered 10 min before formalin injection. After formalin injection, formalin-induced nociceptive behavior (flinching response) was observed for 60 min. Mean arterial pressure (MAP) and heart rate (HR) were measured after intrathecal delivery of zaprinast for a period of 60 min. RESULTS: Intrathecal administration of zaprinast produced a dose-dependent suppression of flinches in both phases. Zaprinast had no evident effects on baseline MAP or HR. CONCLUSIONS: Zaprinast, a phosphodiesterase inhibitor, is active against the nociceptive state evoked by formalin stimulus without affecting resting MAP or HR. Accordingly, spinal zaprinast may be useful in the management of tissue-injury induced pain.

Hypertrophic Scar with Chronic Pain after Acute Herpes Zoster: A case report / 대한통증학회지

The most common and cumbersome complication of herpes zoster is postherpetic neuralgia, which typically presents as neuropathic pain. However, the painful symptoms of the postherpetic period might be associated with other causes, such as skin lesions of the herpes zoster. We report a case of a hypertrophic scar that developed in the lesion of an acute herpes zoster patient and was accompanied by pain.

Effects of Nitrous Oxide on Cardiovascular Response to Laryngoscopy and Endotracheal intubation / 대한마취과학회지

BACKGORUND: Endotracheal intubation in patients undergoing general anesthesia often causes hypertension and tachycardia. Nitrous oxide (N2O), which is frequently used during the induction of anesthesia, is known to augment sympathetic nervous activity in humans. The aim of the present study was to investigate whether N2O affects cardiovascular response to intubation. METHODS: After iRB approval, 100 ASA i patients (aged 35 60 yr) were assigned randomly to receive one of four concentrations (0, 25, 50 or 75%; n = 25 for each) of N2O in oxygen throughout the study period, beginning 3 min before intubation. Anesthesia was induced with iV thiopental (5-7mg/kg) and tracheal intubation was faciliated with iV vecuronium (0.12 mg/kg), while patients were ventilated with the designated concentrations of N2O in oxygen. After intubation, all patients received 2% sevoflurane and N2O in oxygen via a semiclosed anesthesia circuit. Systolic arterial pressure (SAP), heart rate (HR) and rhythm were recorded before and after intubation at intervals for up to 5 min. Plasma concentrations of catecholamines were measured before and 3 min after induction, and 1 and 5 min after intubation. RESULTS: The intubation caused significant increases in SAP and HR in all groups (P<0.05). increasing concentrations of N2O gradually attenuated the pressor response to intubation, without affecting the tachycardiac response. No significant differences were observed between the groups in plasma concentrations of either norepinephrine or epinephrine:norepinephrine concentration increased significantly 1 min after intubation in all N2O-treated groups, while it remained unchanged in the control group. in contrast, the epinephrine concentration remained unaltered in all N2O-treated groups, but increased significantly in the control group. incidence of tachycardia, bradycardia, and arrhythmia was not different among the groups. CONCLUSiONS: These results indicate that N2O suppresses the pressor but not the tachycardiac response associated with endotracheal intubation, while it enhances the increases in plasma norepinephrine concentrations.

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 Dobutamine and Epinephrine on Myocardial Function and Oxygen Balance in Normal and Stunned Myocardium in Dogs / 대한마취과학회지

BACKGROUND: Myocardial ischemia is known to depress systolic and diastolic functions for a prolonged period of time. Dobutamine and epinephrine are frequently administered to improve myocardial function during cardiac surgery. The vascular response to vasopressors might be altered by ischemia and reperfusion, since alterations in vascular control mechanisms have been demonstrated even after a short period of ischemia. The present study was aimed to investigate the effects of dobutamine and epinephrine on regional and global myocardial functions, coronary blood flow (CBF) and myocardial oxygen consumption (MVO2) in normal and stunned myocardium in an open-chest canine model. METHODS: Forty-eight dogs were acutely instrumented under enflurane anesthesia to measure aortic and left ventricular pressures, and pulmonary (cardiac output) and left anterior descending (LAD) blood flows via a Doppler flowmeter, and a subendocardial segment length in the region supplied by the LAD. In series 1, incremental doses of dobutamine (1, 2, 5, 10microgram/kg/min, n = 9) or epinephrine (0.02, 0.04, 0.1, 0.2microgram/kg/min, n = 10) were infused intravenously (IV) for 10 min before (normal) and after 15 min of LAD occlusion and subsequent 1 hr-reperfusion (stunned). In series 2, incremental doses of dobutamine (50, 125, 250, 375 ng/mL of LAD flow, n = 14) or epinephrine (4, 10, 20, 30 ng/mL of LAD flow, n = 15) were infused directly into the LAD (IC) for 3 5 min before (normal) and after myocardial ischemia (stunned). Segment shortening (%SS), as an index of regional myocardial contractility, and the peak segment lengthening rate (dL/dt max), as an index of regional diastolic function, were evaluated. Simultaneous arterial and coronary venous contents of oxygen and lactate were measured to calculate MVO2 and oxygen (EO2) and lactate extraction (Elac) ratios during IV or IC infusions of epinephrine or dobutamine. Effectiveness of metabolic vasodilation was determined from EO2. RESULTS: IV or IC infusions of dobutamine or epinephrine before ischemia resulted in dose-dependent increases in mechanical functions (%SS and dL/dt max) and MVO2. These changes were accompanied by parallel increases in CBF resulting in unaltered EO2 with an infusion of dobutamine, while CBF increased more than MVO2 with epinephrine, resulting in decreased EO2. After the ischemia and reperfusion, %SS and dL/dt max were depressed and Elac was reduced, but similar mechanical responses (%SS and dL/dt max) to both dobutamine & epinephrine were observed. Also, in the stunned myocardium, CBF increased in parallel with mechanical function and MVO2 with either IC or IV dobutamine, resulting in an unaltered EO2. However, IC but not IV epinephrine did not affect EO2, suggesting abolishment of its direct vasodilating effect in stunned myocardium. In addition, IC epinephrine infusion further decreased Elac, while IC dobutamine did not affect it in stunned myocardium. During IV infusions, dobutamine caused a dose-dependent increase in the heart rate but epinephrine did not affect it, despite the comparable increase in cardiac index and mean aortic pressure. CONCLUSIONS: The results indicate that dobutamine and epinephrine exert similar positive inotropic and lusitropic effects in normal and stunned myocardium in dogs. However, epinephrine causes direct coronary vasodilation in normal myocardium, but it does not directly affect coronary vascular tone in stunned myocardium. In addition, epinephrine infusion dose-dependently depresses Elac in stunned myocardium. In contrast, dobutamine affects neither direct coronary vascular tone nor Elac regardless of ischemia and reperfusion injury.