Microvascular endothelial dysfunction and its mechanism in a rat model of subarachnoid hemorrhage.

UNLABELLED: After subarachnoid hemorrhage (SAH), large cerebral arteries are prone to vasospasm. Using a rat model of SAH, we examined whether cortical microvessels demonstrate vasomotor changes that may make them prone to spasm and whether endothelial dysfunction may account for any observed changes. Two days after percutaneous catheterization into the cisterna magna, 0.3 mL of autologous blood was injected into the subarachnoid space. The brain tissue was harvested 20 min later, and microvessels were dissected from the parietal cortex. Vasomotor responses to the thromboxane analog U46619, the protein kinase C agonist phorbol acetate, endothelin-1, adenosine diphosphate, nitroprusside, and isoproterenol were examined in vitroin cerebral arterioles from the control, sham-operated, and SAH animals. Endothelial nitric oxide synthase (NOS3) messenger RNA and protein concentration was measured by northern and western blotting, respectively. Arterioles from the SAH animals demonstrated attenuated dilation to the endothelium-dependent dilator adenosine diphosphate and accentuated constriction to endothelin-1, while responses to the other agents tested were unchanged. NOS3 protein concentration was decreased, but NOS3 messenger RNA was increased after SAH. After SAH, cortical arterioles demonstrate endothelial dysfunction, which may be the basis for microvascular spasm. This is in part related to decreased NOS3, which occurs despite an increase in its transcription. IMPLICATIONS: Acute microvascular endothelial dysfunction may occur after subarachnoid hemorrhage and contribute to microvascular spasm.

The effect of heparin-coated pulmonary artery catheters on activated coagulation time in cardiac surgical patients.

OBJECTIVE: To investigate the effect of heparin-coated pulmonary artery catheters (HPACs) on activated coagulation time (ACT) drawn through a non-heparin-coated introducer sheath. DESIGN: A prospective, observational study. SETTING: University teaching hospital. PARTICIPANTS: Patients scheduled for surgical procedures requiring cardiopulmonary bypass. INTERVENTIONS: With institutional review board approval, 63 patients without prior coagulopathy undergoing procedures requiring cardiopulmonary bypass were studied. Jugular venous and radial arterial ACTs were measured before and immediately after insertion of an HPAC. Additional measurements were obtained 1 hour later and 4 minutes after completion of protamine infusion. MEASUREMENTS AND MAIN RESULTS: The ACT drawn from the introducer after placement of an HPAC was 48 seconds greater than the ACT drawn before the HPAC was placed (p < 0.0001). This difference was still present 1 hour later but not after the administration of protamine or in blood drawn at any time from another site. Baseline ACTs drawn from radial arterial catheters, kept patent using a heparin flush system, resulted in elevated measurements, despite withdrawing seven times the deadspace before taking a sample. CONCLUSIONS: Blood obtained from an introducer with an HPAC in situ provides a spuriously high ACT. ACTs drawn from catheters kept patent using heparin flush also result in prolonged measurements. Baseline ACT measurement from an introducer should be obtained before placement of the HPAC.

Dilation by isoflurane of preconstricted, very small arterioles from human right atrium is mediated in part by K(+)-ATP channel opening.

UNLABELLED: The adenosine triphosphate (ATP)-sensitive potassium channels (K(+)-ATP channels) are activated by decreases in intracellular ATP and help to match blood flow to tissue needs. Such metabolism-flow coupling occurs predominantly in the smallest arterioles measuring 50 microm or less in diameter. Previous studies demonstrated that isoflurane may activate the K(+)-ATP channels in larger arteries. We examined whether isoflurane also activates the channels in the smallest arterioles of approximately 50 microm. Microvessels of approximately 50 microm were dissected from right atrial appendages from patients undergoing coronary artery bypass surgery and were monitored in vitro for diameter changes by videomicroscopy. With or without preconstriction with the thromboxane analog U46619 1 microM, vessels were exposed to isoflurane 0%-3% either in the presence or absence of the K(+)-ATP channel blocker glibenclamide 1 microM. Without preconstriction, isoflurane neither dilated nor constricted the vessels significantly. After preconstriction, isoflurane had a concentration-dependent dilation of the small arterioles (39 +/- 13% [mean +/- SD] dilation at 3% isoflurane) (P < 0.001), and this effect was significantly attenuated by glibenclamide (18 +/- 5% dilation at 3% isoflurane) (P < 0.01). In comparison, nitroprusside 10(-4) M produced 79 +/- 6% dilation, and adenosine diphosphate 10(-4) M produced 29 +/- 7% dilation. We conclude that isoflurane-mediated dilation of the smallest resistance arterioles may be in part based on activation of the K(+)-ATP channels when the arterioles are relatively constricted. IMPLICATIONS: Vasodilation of very small coronary arterioles by isoflurane depends on preexisting tone and may in part be mediated by the K(+)-ATP channels.

Aprotinin decreases exposure to allogeneic blood during primary unilateral total hip replacement.

BACKGROUND: Aprotinin, a hemostatic agent, regulates fibrinolysis, modulates the intrinsic coagulation pathway, stabilizes platelet function, and exhibits anti-inflammatory properties through inhibition of serine proteases, such as trypsin, plasmin, and kallikrein. Aprotinin has been used successfully for many years in cardiac operations, and there have been preliminary investigations of its use in hip replacement operations. The objectives of this multicenter, randomized, placebo-controlled, double-blind trial were to evaluate the efficacy and safety of aprotinin as a blood-sparing agent in patients undergoing an elective primary unilateral total hip replacement and to examine its effect on the prevalence of deep-vein thrombosis in this population. METHODS: Seventy-three patients received a placebo; seventy-six patients, a low dose of aprotinin (a load of 500,000 kallikrein inhibitor units [KIU]); seventy-five, a medium dose of aprotinin (a load of 1,000,000 KIU, with infusion of 250,000 KIU per hour); and seventy-seven patients, a high dose of aprotinin (a load of 2,000,000 KIU, with infusion of 500,000 KIU per hour). The end points for the determination of efficacy were transfusion requirements and blood loss. Patients received standard prophylaxis against deep-vein thrombosis and underwent compression ultrasonography with color Doppler imaging of the proximal and distal venous systems of both legs to evaluate for the presence of deep-vein thrombosis. RESULTS: Aprotinin reduced the percentages of patients who required any form of blood transfusion (47 percent of the patients managed with a placebo needed a transfusion compared with 28 percent of those managed with low-dose aprotinin [p = 0.02],27 percent of those managed with high-dose aprotinin [p = 0.008], and 40 percent of those managed with medium-dose aprotinin [p = 0.5]). Only 6 percent (twelve) of the 212 patients treated with aprotinin required allogeneic blood compared with 15 percent (ten) of the sixty-eight patients treated with the placebo (p = 0.03). Aprotinin decreased the estimated intraoperative blood loss (p = 0.02 for the low-dose group, p = 0.04 for the medium-dose group, and p = 0.1 for the high-dose group), the measured postoperative drainage volume (p = 0.4 for the low-dose group, p = 0.006 for the medium-dose group, and p = 0.000 for the high-dose group), and the mean reduction in the hemoglobin level on the second postoperative day (thirty-four grams per liter for the placebo group, twenty-eight grams per liter for the low-dose group [p = 0.000], twenty-six grams per liter for the medium-dose group [p = 0.000], and twenty-three grams per liter for the high-dose group [p = 0.0001). The rate of deep-vein thrombosis was similar for all groups. CONCLUSIONS: We concluded that aprotinin is safe and effective for use as a hemostatic agent in primary unilateral total hip replacements. In patients who are at high risk of receiving allogeneic blood, use of aprotinin may be of particular clinical and economic benefit.

Epithelium-dependent bronchodilatory activity is preserved in pig bronchioles after normothermic cardiopulmonary bypass.

UNLABELLED: Analogous to vascular endothelium, bronchial epithelium modulates bronchomotor activity by releasing epithelium-derived relaxing factors. Cardiopulmonary bypass (CPB) is associated with endothelial dysfunction. We examined whether CPB may be associated with bronchiolar epithelial dysfunction in pigs. Pigs were exposed to normothermic CPB for 1.5 h and then separated from CPB. Lung tissues were biopsied before and 30 min after CPB. For time control, lung tissues were biopsied at baseline and after 2 hr of anesthesia. Bronchioles measuring about 100 microm were dissected, and the epithelium was either left intact or denuded. Each bronchiolar segment was preconstricted with 10 microM 5-hydroxytryptamine and relaxation responses to nitroprusside 10(-9)-10(-4) M, isoproterenol 10(-9)-10(-4) M, or the inhaled anesthetics halothane or isoflurane 0-2.5 minimum alveolar anesthetic concentration were examined in vitro by videomicroscopy. Bronchiolar segments demonstrated concentration-dependent relaxation responses to each of the dilators examined. Epithelial denudation reduced bronchodilation to isoproterenol, isoflurane, and halothane, but not to nitroprusside. Bronchodilation was not significantly affected by CPB. We conclude that, unlike vascular endothelial function, porcine bronchiolar epithelium-modulated bronchomotor activity is not significantly affected by normothermic CPB. IMPLICATIONS: Normothermic cardiopulmonary bypass does not result in epithelial dysfunction in pigs. Epithelium-dependent and epithelium-independent bronchodilators may be equally effective before and after cardiopulmonary bypass.

The effects of aprotinin on blood product transfusion associated with thoracic aortic surgery requiring deep hypothermic circulatory arrest.

OBJECTIVE: To compare the effects of aprotinin on blood product use and postoperative complications in patients undergoing thoracic aortic surgery requiring deep hypothermic circulatory arrest. DESIGN: A retrospective study. SETTING: A university hospital. PARTICIPANTS: Nineteen patients who underwent elective or urgent thoracic aortic surgery. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The total number of units of packed red blood cells, fresh frozen plasma, and platelets was significantly less in the group that received aprotinin (p = 0.01, 0.04, and 0.01). The intraoperative transfusion of packed red blood cells and platelets, collection and retransfusion of cell saver, and postoperative transfusion of fresh frozen plasma were also significantly less in the aprotinin group (p = 0.01, 0.02, 0.01, and 0.05). No patient in either group sustained renal dysfunction or a myocardial infarction. Two patients who had not received aprotinin suffered from chronic postoperative seizures, and one patient who had received aprotinin sustained a perioperative stroke. CONCLUSIONS: Low-dose aprotinin administration significantly decreases blood product transfusion requirements in the setting of thoracic aortic surgery requiring deep hypothermic circulatory arrest, and it does not appear to be associated with renal or myocardial dysfunction.

Potassium concentrations and ventricular ectopy: a prospective, observational study in post-cardiac surgery patients.

OBJECTIVE: To determine whether a correlation exists between concentrations of intracellular and extracellular potassium and to determine the frequency of ventricular ectopy in patients after cardiac operations. DESIGN: Prospective, observational clinical evaluation. SETTING: Surgical-respiratory intensive care unit of a university-affiliated tertiary care center. PATIENTS: Continuous 24-hr electrocardiographic monitoring was performed, and serum (extracellular) and erythrocyte (intracellular) potassium concentrations ([K+]e and [K+]i) were determined, before cardiopulmonary bypass, immediately postoperatively, and at 2, 4, 12, and 20 hrs after elective coronary bypass grafting in 31 patients. INTERVENTIONS: None. Potassium replacement was left to the discretion of the attending physicians. MEASUREMENTS AND MAIN RESULTS: Although the mean [K+]e varied significantly during the postoperative 24-hr period (p<.0001), the [K+]i did not (p = .953). No significant correlations were found between premature ventricular beats and [K+]i, [K+]e, or [K+]i/[K+]e (all p>.05). However, among the few patients who had one or more episodes of ventricular tachycardia (VT) within 30 mins of a study K+ sample, the mean [K+]e was significantly lower during the episode(s) of VT compared with the mean [K+]e in the absence of VT (p<.01). CONCLUSIONS: Although it is clear that over the clinically acceptable range of [K+]e and [K+]i concentrations seen in this population, there is no correlation between potassium concentrations and the occurrence of premature ventricular beats, the infrequent association of more serious ventricular ectopy, VT, with lower [K+]e concentrations supports the practice of using serum potassium to guide potassium replacement in patients after cardiac operations.

Attenuation of endothelium-dependent dilation of pig pulmonary arterioles after cardiopulmonary bypass is prevented by monoclonal antibody to complement C5a.

UNLABELLED: We examined whether pulmonary endothelial dysfunction associated with cardiopulmonary bypass (CPB) may be mediated by complement C5a in pigs. Pigs were placed on normothermic CPB for 1 h with or without a previous administration of 1.6 mg/kg anti-C5a monoclonal antibody (MAb), then reperfused for 2 h. Pulmonary tissue myeloperoxidase activity was measured. Expression of nitric oxide synthase (NOS) was measured by reverse transcriptase polymerase chain reaction and Western blotting. Pulmonary arterioles approximately 100 microm in diameter were preconstricted with the thromboxane analog U46619 1 microM, and relaxation responses to adenosine diphosphate 10(-9)-10(-4) M, substance P 10(-12)-10(-6) M, and sodium nitroprusside 10(-9)-10(-4) M were examined in vitro by videomicroscopy. Relaxation to the endothelium-dependent dilators adenosine diphosphate and substance P was attenuated after CPB; this attenuation was prevented by the previous administration of MAb. Relaxation to sodium nitroprusside was not affected by CPB. Neutrophil sequestration, as measured by MPO activity, increased after CPB, either with or without MAb. Transcription of NOS was unchanged by CPB, but translation of constitutive NOS was decreased after CPB, and this decrease was prevented by a previous administration of MAb. We conclude that pig pulmonary endothelial dysfunction associated with CPB may be mediated by C5a. The mechanism may involve changes in NOS translation. IMPLICATIONS: In pigs, pulmonary endothelial dysfunction may occur after cardiopulmonary bypass due to product(s) of complement activation.

Preoperative serum potassium levels and perioperative outcomes in cardiac surgery patients. Multicenter Study of Perioperative Ischemia Research Group.

CONTEXT: Although potassium is critical for normal electrophysiology, the association between abnormal preoperative serum potassium level and perioperative adverse events such as arrhythmias has not been examined rigorously. OBJECTIVE: To determine the prevalence of abnormal preoperative serum potassium levels and whether such abnormal levels are associated with adverse perioperative events. DESIGN AND SETTING: Prospective, observational, case-control study of data collected from 24 diverse US medical centers in a 2-year period from September 1, 1991, to September 1, 1993. PATIENTS: A total of 2402 patients (mean [SD] age, 65.1 [10.3] years; 24% female) undergoing elective coronary artery bypass grafting who were not enrolled in another protocol. The study population was identified using systematic sampling of every nth patient, in which n was based on expected total number of procedures at that center during the study period. MAIN OUTCOME MEASURES: Intraoperative and postoperative arrhythmias, the need for cardiopulmonary resuscitation (CPR), cardiac death, and death due to any cause prior to discharge, by preoperative serum potassium level. RESULTS: Perioperative arrhythmias occurred in 1290 (53.7%) of 2402 patients, with 238 patients (10.7%) having intraoperative arrhythmias, 329 (13.7%) having postoperative nonatrial arrhythmias, and 865 (36%) having postoperative atrial flutter or fibrillation. The incidence of adverse outcomes was 3.6% for death, 2.0% for cardiac death, and 3.5% for CPR. Serum potassium level less than 3.5 mmol/L was a predictor of serious perioperative arrhythmia (odds ratio [OR], 2.2; 95% confidence interval [CI], 1.2-4.0), intraoperative arrhythmia (OR, 2.0; 95% CI, 1.0-3.6), and postoperative atrial fibrillation/flutter (OR, 1.7; 95% CI, 1.0-2.7), and these relationships were unchanged after adjusting for confounders. The significant univariate association between increased need for CPR and serum potassium level less than 3.3 mmol/L (OR, 3.3; 95% CI, 1.2-9.5) and greater than 5.2 mmol/L (OR, 3.0; 95% CI, 1.1-8.7) became nonsignificant after adjusting for confounders. CONCLUSIONS: Perioperative arrhythmia and the need for CPR increased as preoperative serum potassium level decreased below 3.5 mmol/L. Although interventional trials are required to determine whether preoperative intervention mitigates these adverse associations, preoperative repletion is low cost and low risk, and our data suggest that screening and repletion be considered in patients scheduled for cardiac surgery.

Changes in plasma catecholamine concentrations and haemodynamic effects of rocuronium and vecuronium in elderly patients.

Rocuronium administration may cause tachycardia and an increase in cardiac index. Pancuronium, another steroidal non-depolarizing muscle relaxant, augments release of, and blocks re-uptake of catecholamines at adrenergic nerve endings. This study compared the haemodynamic effects of, and changes in catecholamine concentrations following administration of vecuronium (0.12 mg kg-1) or rocuronium (0.9 mg kg-1) to elderly patients. Thirty patients, 65 years or older, not receiving beta-blockers, were studied. During thiopentone, fentanyl, nitrous oxide anaesthesia, either rocuronium (0.9 mg kg-1) or vecuronium (0.12 mg kg-1) was administered, according to random allocation. In all 30 patients, blood pressure and heart rate were measured before induction of anaesthesia, immediately and 1 min after induction, 1 and 2 min after muscle relaxant administration, and immediately, 1 and 2 min after tracheal intubation. In the latter 20 patients, samples for plasma catecholamine estimation were obtained prior to, and 1 min after muscle relaxant administration and 1 min after tracheal intubation. Blood pressure and heart rate were similar in the two groups throughout the study. Plasma noradrenaline concentrations were similar in the vecuronium and rocuronium groups prior to muscle relaxant administration (589(SD240) and 444(SD213) pg mL-1, respectively), 1 min after muscle relaxant administration (602(SD220) and 520(SD392) pg mL-1, respectively) and 1 min after tracheal intubation (597(SD351) and 440(SD181) pg mL, respectively). There was no significant change in either plasma noradrenaline or adrenaline concentrations in either group following muscle relaxant administration or tracheal intubation. The use of rocuronium (0.9 mg kg-1) in elderly patients does not result in a clinically significant change in heart rate, blood pressure or plasma catecholamine concentration.

The concordance of intraoperative left ventricular wall-motion abnormalities and electrocardiographic S-T segment changes: association with outcome after coronary revascularization. Multicenter Study of Perioperative Ischemia (McSPI) Research Group.

BACKGROUND: Transesophageal echocardiography (TEE) and Holter electrocardiography (ECG) are used to detect intraoperative ischemia during coronary artery bypass graft surgery (CABG). Concordance of these modalities and sensitivity as indicators of adverse perioperative cardiac outcomes are poorly defined. The authors tried to determine whether routine use of Holter ECG and TEE in patients with CABGs has clinical value in identifying those patients in whom myocardial infarction (MI) is likely to develop. METHODS: A total of 351 patients with CABG and both ECG- and TEE-evaluable data were examined for the occurrence of ischemia and infarction. The TEE and five-lead Holter ECGs were performed continuously during cardiac surgery. The incidence of MI (creatine kinase-MB > or = 100 ng/ml) within 12 h of arrival in the intensive care [ICU] unit, new ECG Q wave on ICU admission or on the morning of postoperative day 1, or both, were recorded. RESULTS: Electrocardiographic or TEE evidence of intraoperative ischemia was present in 126 (36%) patients. The concordance between modalities was poor (positive concordance = 17%; Kappa statistic = 0.13). Myocardial infarction occurred in 62 (17%) patients, and 32 (52%) of them had previous intraoperative ischemia. Of these, 28 (88%) were identified by TEE, whereas 13 (41%) were identified by ECG. Prediction of MI was greater for TEE compared with ECG. CONCLUSIONS: Wall-motion abnormalities detected by TEE are more common than S-T segment changes detected by ECG, and concordance between the two modalities is low. One half of patients with MI had preceding ECG or TEE ischemia. Logistic regression revealed that TEE is twice as predictive as ECG in identifying patients who have MI.

Peri-operative dysrhythmias in patients undergoing major vascular surgery--a preliminary report.

The objective of this prospective study was to determine the nocturnal/diurnal distribution of peri-operative cardiac dysrhythmias in patients with coronary artery disease undergoing major vascular surgery. Eight patients with significant coronary artery disease undergoing major vascular surgery were studied. Continuous Holter monitoring was performed on each patient from approximately 1 h pre-operatively until 2-5 days post-operatively. Frequencies of isolated supraventricular and ventricular premature beats, and runs of supraventricular and ventricular premature beats were calculated for 6-h periods (00.00-06.00; 06.00-12.00; 12.00-18.00; 18.00-24.00 hours). Supraventricular tachycardia occurred significantly more frequently between 00.00 and 06.00 hours than during the other 6-h periods studied in the post-operative period following major vascular surgery.

Administration of magnesium sulphate before rocuronium: effects on speed of onset and duration of neuromuscular block.

The speeds of onset of pancuronium, atracurium and vecuronium are increased by prior administration of magnesium sulphate. A prospective, randomized, double-blind, controlled, clinical study was performed to examine the effects of prior i.v. administration of magnesium sulphate 60 mg kg-1 on the neuromuscular blocking effects of rocuronium 0.6 mg kg-1 during isoflurane anaesthesia. Neuromuscular function was measured electromyographically (Relaxograph) in 30 patients who received either magnesium sulphate 60 mg kg-1 or normal saline, 1-min before rocuronium 0.6 mg kg-1. Mean onset times were similar in the two groups (magnesium sulphate 71 (SD 20) s; normal saline 75 (23) s), but times to initial, 10% and 25% recovery from neuromuscular block were significantly longer in the magnesium sulphate group (42.1 (16.3), 49.0 (12.4) and 56.5 (13.2) min, respectively) than in the saline group (25.1 (9.1), 33.0 (11.1) and 35.6 (13.2) min, respectively) (P < 0.05 in all three cases). Administration of magnesium sulphate was not associated with adverse haemodynamic effects. Prior administration of magnesium sulphate, under the study conditions described, prolonged rocuronium-induced neuromuscular block but did not increase speed of onset.

Electrocardiographic and hemodynamic changes and their association with myocardial infarction during coronary artery bypass surgery. A multicenter study. Multicenter Study of Perioperative Ischemia (McSPI) Research Group.

BACKGROUND: Electrocardiographic (ECG) changes during coronary artery bypass graft surgery have not been described in detail in a large multicenter population. The authors describe these ECG changes and evaluate them, along with demographic and clinical characteristics and intraoperative hemodynamic alterations, as predictors of myocardial infarction (MI) as defined by two sets of criteria. METHODS: Data from 566 patients at 20 clinical sites, collected as part of a clinical trial to evaluate the efficacy of acadesine for reducing MI, were analyzed at core laboratories. Perioperative ECG changes were identified using continuous three-lead Holter ECG. Systolic blood pressure, diastolic blood pressure, and heart rate were recorded each minute during operation. The occurrence of MI by Q wave or myocardial fraction of creatine kinase (CK-MB) or autopsy criteria, and by (Q wave and CK-MB) or autopsy criteria was determined. RESULTS: During perioperative Holter monitoring, episodes of ST segment deviation, major cardiac conduction changes > or = 30 min, or use of ventricular pacing > or = 30 min occurred in 58% patients, primarily in the first 8 h after release of aortic occlusion. Of the 25% patients who met the Q wave or CK-MB or autopsy criteria for MI, 19% had increased CK-MB as well as ECG changes. (Q wave and CK-MB) or autopsy criteria for MI were met by 4% of patients. The CK-MB concentration generally peaked by 16 h after release of aortic occlusion. In patients with (n = 187) and without a perioperative episode of ST segment deviation, the incidence of MI was 36% and 19%, respectively (P < 0.01), by Q wave or CK-MB or autopsy criteria, and 6% and 3%, respectively (P = 0.055), by (Q wave and CK-MB) or autopsy criteria. Multiple logistic regression analysis showed that intraoperative ST segment deviation, intraventricular conduction defect, left bundle branch block, duration of hypotension (systolic blood pressure < 90 mmHg) after cardiopulmonary bypass, and duration of cardiopulmonary bypass are independent predictors of Q wave or CK-MB or autopsy MI. The independent predictors of (Q wave and CK-MB) or autopsy MI are intraoperative ST segment deviation and duration of aortic occlusion. CONCLUSIONS: Major ECG changes occurred in 58% of patients during coronary artery bypass graft surgery, primarily within 8 h after release of aortic occlusion. Multicenter data collection revealed a substantial variation in the incidence of MI and an overall incidence of up to 25%, with most MI occurring within 16 h after release of aortic occlusion. Intraoperative monitoring of ECG and hemodynamics has incremental value for predicting MI.

Minimally invasive direct coronary artery bypass: our experience with 32 patients.

From January 1996 to May 1997, minimally invasive direct coronary artery bypass (MIDCAB) through a small anterior thoracotomy without cardiopulmonary bypass was completed in 31 of 32 patients (Male: Female=1.9:1, mean age=64.6 years, 11 (34.4%)>70 years). Twenty, five, and seven patients had one, two, and three vessel disease respectively. Twelve patients presented with unstable angina, seven had prior myocardial infarction, one had a pre-operative intra-aortic balloon pump, and four had prior coronary artery bypass grafting (CABG). Eight were diabetic, five had chronic obstructive pulmonary disease, and one was morbidly obese. Our newly developed coronary artery immobilizing and occluding device facilitated the coronary anastomosis. There were no post-procedure deaths, no peri-operative myocardial infarctions, and no strokes. One patient required intra-operative conversion to conventional CABG for an intramyocardial target vessel. Two patients had conversion after post-operative angiogram demonstrated incorrect target identification and early graft occlusion. Four patients had limited access graft revision (two kinks, one graft injury, and one haemorrhage). Thirty-one of the 32 patients were followed from 0.5 to 16 months and 30 reported no post-operative cardiac events (one required PTCA to another vessel). We conclude that MIDCAB is safe and effective.

Pulsed wave Doppler measurement of cardiac output from the right ventricular outflow tract.

Doppler ultrasound can be used to measure cardiac output (CO). Intraoperative Doppler cardiac output (DCO) by transesophageal echocardiography (TEE) has been studied using blood flow velocity from the left ventricular outflow tract (LVOT), the mitral valve (MV), and the main pulmonary artery (MPA). The purpose of this study was to compare DCO, measured from a relatively new TEE view of the right ventricular outflow tract (RVOT), with thermodilution cardiac output (TDCO). We also compared changes in DCO from the RVOT to changes in TDCO. A 5.0/3.7 MHz multiplane TEE probe was placed in 45 adult cardiac surgical patients undergoing general anesthesia. Patients were excluded if there was greater than mild tricuspid valve insufficiency. From the transgastric view, at approximately 110-140 degrees, the RVOT was imaged. DCO was calculated from 1) the time-velocity integral (TVI) using pulse wave (PW) Doppler, 2) the area of the RVOT (measured in early systole using the diameter (pi(D/2)2) of the RVOT at the level of the PW Doppler sample volume), and 3) the heart rate. Simultaneous TDCO was performed by a separate examiner. The RVOT was imaged satisfactorily in 84% of patients (38/45). The mean bias between DCO and TDCO was -0.01 L/min (2 SD +/- 0.45 L/min; n = 38). There was good correlation between DCO and TDCO (R2 = 0.97). Changes in TDCO and changes in DCO were compared in 15 patients. The mean bias between changes in DCO and changes in TDCO was 0.04 L/min (2 SD +/- 0.66 L/min). Analysis of the changes in DCO and TDCO showed good correlation (R2 = 0.96). We conclude that there is a good correlation between DCO measured from the RVOT and TDCO. This technique permits cardiac output measurement without the necessity of placing a pulmonary artery catheter, and it also provides a method of evaluating RVOT blood flow.