Phenylephrine to increase blood flow in the radial artery used as a coronary bypass conduit

OBJECTIVE: The radial artery has more smooth muscle in its wall than the other arterial conduits and is known to be vasospastic. Because it is frequently necessary to use vasoconstrictors early after coronary bypass surgery we investigated the effects of phenylephrine on conduit flow in this setting. METHODS: Thirty patients undergoing coronary artery bypass with all arterial conduits in which the radial artery was used as a T-graft were randomly assigned to receive intravenous infusions of normal saline (n = 10); nitroglycerin, 0.5 microg x kg x min (n = 11); or nicardipine, 0.5 microg x kg x min (n = 9), beginning early in the operation. After discontinuation of cardiopulmonary bypass and achievement of stable hemodynamics, control measurements were obtained, and this was followed by phenylephrine infusion to achieve a 20% increase in mean arterial pressure, after which the measurements were repeated. RESULTS: Mean radial artery flow increased similarly in all groups: normal saline, 40% +/- 25%; nicardipine, 37% +/- 27%; nitroglycerin, 48% +/- 36% (P = .533). Comparable changes occurred in arterial pressure and systemic vascular resistance, whereas the cardiac index remained unchanged. CONCLUSION: Radial artery blood flow increases when the mean arterial pressure is increased with phenylephrine. There was no evidence of a conduit vasoconstrictive effect, which could limit or reduce conduit flow. Vasoconstriction with phenylephrine is appropriate to provide adequate perfusion pressure for radial artery grafts.     

Accuracy of radial arterial pressure measurement during surgery under controlled hypotension

BACKGROUND: Radial arterial pressure underestimates the pressure in the aorta in several clinical situations. A central-to-radial pressure gradient was attributed to intense vasodilation. The aim of this study was to evaluate the accuracy of radial pressure monitoring during controlled hypotension achieved with profound arterial vasodilation. METHODS: Ten patients with ASA physical status I and II undergoing maxillofacial surgery under general anesthesia were enrolled in this prospective study. Radial and femoral arteries were cannulated and connected to a pressure monitoring system. Controlled hypotension was achieved with an infusion of nicardipine titrated to maintain MAP between 50 and 60 mmHg. Simultaneous radial and femoral systolic, mean and diastolic arterial pressures were recorded before, during and after controlled hypotension. Results were expressed as mean +/- SD. Concomitant radial and femoral pressures were compared by a paired Student's test, P < 0.05 being significant. RESULTS: In all, 150 sets of arterial pressures measurement were obtained. There were no statistically significant differences between radial and femoral arterial pressures measured before, during or after controlled hypotension. CONCLUSION: Radial arterial pressure is an accurate measure of central arterial pressure during controlled hypotension achieved with arterial vasodilation.     

Deep hypothermic circulatory arrest and the femoral-to-radial arterial pressure gradient

OBJECTIVES: To determine the femoral-to-radial arterial pressure gradient, as well as the factors associated with them, in patients receiving cardiopulmonary bypass (CPB) with profound hypothermia and circulatory arrest. DESIGN: Retrospective automated hemodynamic record review. SETTING: University hospital. PARTICIPANTS: Patients undergoing pulmonary thromboendarterectomy with deep hypothermic circulatory arrest. MEASUREMENTS AND MAIN RESULTS: The automated hemodynamic records of 54 consecutive patients undergoing pulmonary thromboendarterectomy with deep hypothermic circulatory arrest were reviewed, comparing the femoral and radial arterial pressures throughout the intraoperative period. In 20 of the patients, the hemodynamic data from the first 16 postoperative hours were also studied. Forty-one of 54 (76%) of the patients exhibited a mean arterial gradient of at least 10 mmHg either during or after CPB, femoral being higher. Clinically significant gradients were noted throughout the CPB period and the post-CPB period in these patients. In the 54 patients studied, the systolic blood pressure (SBP) gradient was 32 +/- 19 mmHg after CPB (95% confidence limits 28.2 mmHg, 39.0 mmHg), and the mean arterial pressure (MAP) gradient was 6.3 +/- 4.9 mmHg (95% confidence limits 5.5 mmHg, 8.6 mmHg). The duration of clinically significant SBP (>10 mmHg) and MAP (>5 mmHg) gradients in the postoperative period were 5.2 +/- 5.7 hours and 5.8 +/- 7.2 hours, respectively. Advanced age correlated with high post-CPB pressure gradients in this population and was associated with prolonged postoperative resolution of the gradients. CONCLUSIONS: The femoral-to-radial arterial pressure gradients, particularly systolic, after CPB, were greater and of longer duration in these patients undergoing deep hypothermic circulatory arrest than gradients previously reported for routine CPB. Central arterial pressure monitoring is recommended for patients undergoing deep hypothermic circulatory arrest, being valuable both for intraoperative and postoperative care.     

Effect of vasodilators on femoral-to-radial arterial pressure gradient after cardiopulmonary bypass]

In 57 adult patients undergoing valve replacement surgery or valve plastic surgery, pressure gradient between the femoral and radial artery was evaluated after cardiopulmonary bypass (CPB). During CPB, the rectal temperature was kept at mild or moderate hypothermia. Nitrates and prostaglandin E1 were administered in all patients during operation. Patients were divided into two groups; Group A of 31 patients who had history of hypertension and received some vasodilators up to the operation, and Group B of 27 patients who had no history of such medication. There was no difference in patient's characteristics, anesthetic time, CPB time and aortic cross clamping time between the two groups. There was a significant difference between the pre-CPB and post-CPB in hematocrit data. Systemic vascular resistance (SVR) decreased significantly from the pre-CPB level to the post-CPB level. There was no significant difference between Group A and Group B in SVR, but a higher femoral-to-radial artery pressure gradient was observed in Group A until the end of operation. Hypertension and the use of vasodilator change the tone of peripheral blood vessels and intensify femoral-to-radial artery pressure gradient after CPB.     

A comparison of brachial, femoral, and aortic intra-arterial pressures before and after cardiopulmonary bypass

Following recent evidence that brachial and femoral artery pressures are more reliable than radial artery pressures after cardiopulmonary bypass, thirty-one adults had simultaneous pre- and post-bypass measurements of brachial, femoral, and ascending aortic pressures. Two minutes after cardiopulmonary bypass, brachial artery systolic pressure and mean arterial pressure fell significantly below corresponding pressures in the femoral artery and aorta. Five minutes after cardiopulmonary bypass, only brachial artery systolic pressure was still less than femoral and aortic systolic pressures. By ten minutes after bypass, all significant pressure differences had resolved except between brachial and femoral artery systolic pressures. Clinically significant (greater than or equal to 5 mmHg) aortic-to-brachial reductions in mean arterial pressures occurred in six (19%) patients at two minutes and in three (10%) patients at five and ten minutes after bypass. Equivalent aortic-to-femoral mean pressure diminution occurred in two (6%) patients at two minutes and one (3%) patient at five and ten minutes after bypass. Neither systemic vascular resistance nor body temperatures contributed significantly to post-bypass central-to-peripheral pressure reductions. Immediately following bypass, femoral artery pressures reproduce central aortic pressures more reliably than do radial or brachial artery pressures.     

Effects of nicardipine and nitroglycerin on perioperative myocardial ischemia in patients undergoing coronary artery bypass surgery.

Perioperative myocardial ischemic episodes are predictive of adverse cardiac outcomes after coronary artery bypass surgery. We compared the efficacy of continuous infusions of nicardipine (group NIC) and nitroglycerin (group NTG) in reducing the frequency and severity of myocardial ischemic episodes. Patients received either a nicardipine infusion, 0.7 to 1.4 microg/kg/min (n = 30), nitroglycerin infusion, 0.5 to 1 microg/kg/min (n = 30), or neither medication (group C; n = 17) after aortic occlusion clamp release and for 24 hours postoperatively. Myocardial ischemic episodes were considered as ST segment depressions or elevations of 1 mm or greater from baseline, each at J + 60 milliseconds and lasting 1 minute or greater, using a two-channel Holter monitor. Only nicardipine significantly decreased the duration (3.2 +/- 1.2 min/h) and the area under the ST time curve (AUC; 5.7 +/- 15.7 AUC/h) of 1-mm or greater myocardial ischemic episodes compared with group C (17.2 +/- 5.6 min/h and 30.1 +/- 49 AUC/h, respectively) during the intraoperative postbypass period. A trend toward lower frequency, duration, and area under the ST time curve of myocardial ischemic episodes was observed in group NIC compared with group NTG. Cardiac indices and mixed venous oxygen saturations were significantly greater, whereas systemic pressures were less in group NIC compared with group NTG for the same period. These results suggest that nicardipine, but not nitroglycerin, decreased the duration and area under the ST time curve of myocardial ischemic episodes shortly after coronary revascularization. Larger studies are required to verify the efficacy of nicardipine in reducing the severity of myocardial ischemia during cardiac surgery.     

The effect of calcium channel blockers on cerebral oxygenation during tracheal extubation

Calcium channel blockers are effective in stabilizing systemic hemodynamics during tracheal extubation. However, they may increase cerebral blood flow (CBF) during tracheal extubation because of cerebral vasodilation, even if systemic arterial blood pressure decreases. In this study, we observed changes in cerebral oxygenation during tracheal extubation by using near-infrared spectroscopy and evaluated the effect of nicardipine and diltiazem on the resultant changes. We studied 45 women undergoing elective gynecologic surgery. After surgery, the patients were randomly allocated to three groups (n = 15 each): saline (control), 0.02 mg/kg nicardipine, and 0.2 mg/kg diltiazem. After 2 min, we started to aspirate secretions for 2 min and then, extubated the trachea. Changes in cerebral oxygenated hemoglobin (HbO(2)) and deoxygenated hemoglobin were measured during the extubation procedure for 9 min after drug treatment. Systemic hemodynamics, including mean arterial blood pressure, heart rate, end-tidal CO(2), end-tidal sevoflurane concentration, and peripheral arterial oxygen saturation were also monitored. During extubation, HbO(2) increased significantly, presumably caused by the increase in CBF. Changes in deoxygenated hemoglobin were minimal. Compared with the control, nicardipine and diltiazem significantly inhibited the increase in mean arterial blood pressure. On the contrary, they significantly enhanced the increase in HbO(2). In conclusion, calcium channel blockers may increase CBF during extubation, even if these drugs stabilize systemic hemodynamics. Implications: This study is a preliminary report evaluating the changes in cerebral oxygenation during the tracheal extubation. Cerebral oxygenated hemoglobin increased significantly, presumably caused by the increase in cerebral blood flow during extubation. In addition, these changes were enhanced by calcium channel blockers.     

Nicardipine or nitroglycerin in patients with failed percutaneous coronary angioplasty: effect on myocardial diastolic function

OBJECTIVE: To evaluate whether intracoronary vasodilators can improve diastolic function in 32 patients with failed percutaneous transluminal coronary angioplasty (PTCA). DESIGN: Clinical trial. SETTING: Single-institution, academic hospital. PARTICIPANTS: Failed PTCA patients undergoing emergency coronary artery bypass grafting surgery. INTERVENTIONS: Patients were divided into 2 groups: group A received 0.1 mg of intracoronary nicardipine, and group B received 20 microg of intracoronary nitroglycerin. Both drugs were administrated via a coronary dilatation perfusion catheter inserted in the catheterization laboratory by the cardiologist. Subsequently, they were continuously infused via the side port of the introducer of the pulmonary artery catheter and titrated to keep systolic blood pressure at about two thirds of the control value. Transesophageal echocardiography (Power Vision/6000, 9-mm 5MHZ Probe; Toshiba, Elmsford, NY) was used in this study. MEASUREMENTS AND MAIN RESULTS: Left ventricular ejection fraction, cardiac index, tissue Doppler imaging velocity of the left ventricle and mitral annulus, and troponin levels were measured before and after administration of the 2 vasodilators and after cardiopulmonary bypass. Diastolic dysfunction was found preoperatively in all the patients and responded only to intracoronary nicardipine. Ea of mitral annulus velocity significantly increased in group A patients from 7.5 +/- 0.02 to 11.8 +/- 0.01 (p < 0.005) and decreased in group B patients from 8.0 +/- 0.03 to 7.5 +/- 0.02 after nicardipine or nitroglycerin administration. Left ventricular ejection fraction and cardiac index increased significantly (p < 0.005) only after nicardipine administration. Troponin levels were significantly lower in group A than in group B patients (p < 0.005). CONCLUSION: Intracoronary nicardipine improves diastolic function and myocardial flow velocity in patients with failed PTCA undergoing emergency coronary artery bypass graft surgery.     

米力农对心肺转流心瓣膜置换术患者心肌缺血-再灌注损伤的影响

目的比较心肺转流(CPB)下心瓣膜置换术使用米力农和硝酸甘油时患者血浆中心肌肌钙蛋白I(cTnI)及肌酸激酶同功酶MB(CK-MB)水平的变化,了解其对心肌缺血-再灌注损伤的影响.方法择期心内直视手术心瓣膜置换患者24例,分为米力农组(M组)和硝酸甘油组(N组),每组12例.分别于全麻诱导前(T0)、主动脉开放后10min(T1)和术毕(T2)抽取患者中心静脉血,测定cTnI和CK-MB血浆水平.结果M组cTnI在T1和T2均较N组低(P＜0.05).两组CK-MB组间比较M组略低于N组(P＞0.05).M组和N组内cTnI、CK-MB在T1和T2所测定值均高于T0(P＜0.05),且T2高于T1(P＜0.05).两组cTnI、CK-MB随时间推移呈明显上升趋势.结论CPB下行心瓣膜置换术时使用米力农比使用硝酸甘油更有可能改善心肌的缺血-再灌注损伤.     

Inaccuracy of radial artery pressure measurement after cardiac operations

The phenomenon of a pressure gradient between central and radial arteries was evaluated in 48 patients immediately after coronary artery bypass operations. All were in stable hemodynamic condition, none receiving catecholamine support. In eight patients (Group A) mean femoral pressure was significantly higher than mean radial pressure (range 10 to 30 mm Hg). In the remaining 40 (Group B) radial and femoral pressures were equal. Mean cardiac index (thermodilution) was 3.3 +/- 0.68 versus 2.1 +/- 0.4 L/min/m2, systemic vascular resistance 1,181 +/- 218.4 versus 2,049 +/- 501 dynes/sec/cm-5, toe temperature 23.8 degrees +/- 1.2 degrees C versus 24.02 degrees +/- 0.9 degrees C, core temperature 33.9 degrees +/- 0.5 degrees C versus 34.1 degrees +/- 0.6 degrees C, mixed venous oxygen saturation 78% +/- 3% versus 62% +/- 5%, and peak radial dP/dt 1,485 +/- 366 versus 2,028 +/- 392 in Groups A and B, respectively. These data indicate, first, that the low radial pressures measured in Group A patients did not represent the true central aortic pressures; that is, they were false. Second, these low pressures had nothing to do with compromised cardiac function; rather, they were due to peripheral constriction and volume factors and also probably to proximal shunting. It is therefore recommended that while the chest is still open, if a discrepancy exists between a low radial artery pressure, a high palpable aortic pressure, and a satisfactory cardiac contraction, a femoral cannula for pressure measurement should be inserted. Treatment is by blood infusion until the femoral-radial gradient has been abolished.     

Effects of chlorpromazine as a systemic vasodilator during cardiopulmonary bypass in neonates

OBJECTIVES: Vasodilator use during cardiopulmonary bypass is important in pediatric cardiac surgery, but the full range of their effects on hemodynamics remains to be clarified. We studied the effects of chlorpromazine, a potent alpha-blocking agent, in neonates. METHODS: Subjects were 60 neonates undergoing arterial switch operations for complete transposition of the great arteries with an intact ventricular septum. Of these, 37 received 2.1 to 6.5 mg/kg of chlorpromazine during cardiopulmonary bypass (CPZ group) and 23 received no vasodilator (control group). We then compared hemodynamic parameters between groups during and early after surgery. RESULTS: The systemic vascular resistance index and mean arterial pressure during cardiopulmonary bypass were significantly lower in the CPZ group (p < 0.05), but systolic pressure 15 minutes after cessation of cardiopulmonary bypass did not differ between groups. The rise in peripheral temperature during rewarming after hypothermia was significantly higher and the acid-base status 40 minutes after cardiopulmonary bypass less acidotic in the CPZ group. Urine output during cardiopulmonary bypass was higher in the CPZ group. CONCLUSIONS: Chlorpromazine effectively counteracts systemic vasoconstriction induced by cardiopulmonary bypass without serious side effects in neonatal cardiac surgery.     

A randomized, blinded, placebo-controlled evaluation of calcium chloride and epinephrine for inotropic support after emergence from cardiopulmonary bypass.

Forty hemodynamically stable patients were randomized to receive an intravenous bolus of either calcium chloride (5 mg/kg) (n = 20) or placebo (n = 20) (phase I). Six minutes later, they received either an epinephrine (30 ng.kg-1.min-1) (n = 20) or placebo (n = 20) infusion (phase II). Hemodynamic and ionized calcium measurements were obtained in phase I at baseline and at 3 and 6 min after the bolus, and in phase II, at 3 and 6 min (study times 9 and 12 min) after initiation of the infusion. Compared with placebo, calcium did not significantly increase cardiac index but significantly increased mean arterial pressure. Calcium improved cardiac index from 2.46 +/- 0.12 (mean +/- SEM) to 2.74 +/- 0.12 L.min-1.m-2; likewise, placebo improved cardiac index from 2.51 +/- 0.15 to 2.74 +/- 0.15 L.min-1.m-2. Mean arterial blood pressure increased with calcium from 74 +/- 2 to 82 +/- 3 mm Hg compared with a placebo change of 74 +/- 2 to 76 +/- 2 mm Hg. Patients who received the epinephrine infusion (n = 20) demonstrated a significant increase in cardiac index at time 12 min compared with patients receiving only placebo (n = 20). Cardiac index of the epinephrine group increased from 2.56 +/- 0.15 to 2.92 +/- 0.22 L.min-1.m-2, whereas in the placebo group it decreased from 2.86 +/- 0.13 to 2.78 +/- 0.12 L.min-1.m-2. Prior administration of calcium did not alter the subsequent response to epinephrine (n = 10) compared with patients receiving epinephrine alone (n = 10). We conclude that cardiac index improves with time without drug therapy after bypass. Calcium chloride increases mean arterial blood pressure but not cardiac index immediately after cardiopulmonary bypass, whereas low-dose epinephrine significantly increases both cardiac index and mean arterial blood pressure without causing tachycardia in these patients. Calcium chloride (5 mg/kg) did not augment or inhibit the hemodynamic response to an epinephrine infusion.     

Long-term hypotensive technique with nicardipine and nitroprusside during isoflurane anesthesia for spinal surgery.

Short-term infusion of nicardipine can be used to induce deliberate hypotension but may result in plasma drug accumulation. To assess long-term nicardipine administration for deliberate hypotension in 10 patients in a moderately hemodiluted state who were undergoing spinal surgery, hemodynamics and plasma nicardipine concentrations were concomitantly measured before and 20, 80, and 140 min after starting nicardipine, at drug discontinuation, and 20 and 80 min later. A dose of 6.2 +/- 0.9 mg (mean +/- SEM) of nicardipine was initially required to obtain mean arterial blood pressures at 55-60 mm Hg. Maintenance doses of nicardipine were 3-5 mg/h. The duration of nicardipine administration was 270 +/- 20 min (mean +/- SEM). Hypotension was associated with decreased systemic and pulmonary vascular resistances, increased cardiac index, and decreased arteriovenous difference in O2 contents. Only two patients required homologous blood transfusion. Plasma nicardipine concentrations peaked at 110 +/- 21 ng/mL (mean +/- SEM) and then decreased to 38 +/- 11 ng/mL (mean +/- SEM) without changes in arterial blood pressure. After vasodilator discontinuation, hypotension was observed during a mean time of 43 min (range 27-88 min) despite plasma concentrations less than 20 ng/mL. No relationship was found between plasma nicardipine concentrations and hemodynamics. These findings suggest that an increasing effect of nicardipine over time may occur during prolonged administration. Because the reasons for this hysteresis remain unclear, use of nicardipine infusion during major surgery and anesthesia requires particular caution.     

PEEP reverses nitroglycerin-induced hypoxemia following coronary artery bypass surgery

Intravenous nitroglycerin is increasingly used during and after cardiac surgery to control blood pressure and improve subendocardial and peripheral circulation. A dramatic decrease in arterial oxygenation has, however, been reported in a number of poorly controlled clinical trials. In the present investigation 16 patients were studied 2-4 h after coronary artery bypass procedures. All were treated with a continuous infusion of nitroglycerin (1 microgram X kg-1 X min-1). Utilizing an on-off-on drug design, it was clearly established that nitroglycerin depresses arterial oxygenation by increasing the pulmonary venous admixture. Three possible underlying mechanisms are discussed, but at the present time no firm conclusion can be drawn as to the nature of the changes. Eight patients were ventilated with 1 kPa (10 cmH2O) positive end-expiratory pressure (PEEP) during the nitroglycerin infusion. PEEP-ventilation reversed nitroglycerin-induced changes in arterial oxygenation and pulmonary shunting without adversely affecting hemodynamic stability.     

Nicardipine to control mean arterial pressure during extracorporeal membrane oxygenation

The authors present the use of nicardipine to control mean arterial pressure (MAP) in a 19–month-old boy who required venoarterial extracorporeal membrane oxygenation for 11 days for treatment of hydrocarbon aspiration. Nicardipine is an intravenously administered dihydropyridine calcium channel antagonist whose primary physiological action includes vasodilatation. Unlike other calcium channel blockers, it has limited effects on the inotropic and dromotropic function of the myocardium. Nicardipine was started at 5 μg·kg^?1·min^?1 and within five min lowered the MAP from a maximum value of 108 mmHg back to the baseline range of 60 to 80 mmHg. Once the MAP had returned to baseline values, infusion requirements varied from 1 to 3 μg·kg^?1·min^?1 to maintain the MAP at 60 to 80 mmHg during the 11 days of ECMO. No increase in dose requirements were noted during the 11 days.     

Aortic and radial pulse contour: different effects of nitroglycerin and prostacyclin.

Through vasorelaxation, nitroglycerin is considered to reduce arterial wave reflection and to cause a more pronounced decrease in systolic pressure in the aorta (AoSAP) than in the radial artery (RaSAP). Our aim was to study how radial and aortic pulse wave configurations and the gradient (RaSAP-AoSAP) were affected by nitroglycerin and by prostacyclin, and how these changes correlated to stroke volume, vascular resistance/impedance, and wave reflection. Prostacyclin has not been studied in this context and was chosen because, in contrast to nitroglycerin, it does not reduce stroke volume and reduces afterload by arteriolar dilation. In 18 patients (53-81 yr old; heavily premedicated before coronary artery surgery), blood pressure was measured in both the radial artery and the ascending aorta (tipmanometry), and cardiac output was measured by thermodilution. Mean arterial pressure was reduced stepwise with each drug (mean total decrease 10-12 mm Hg). The initial RaSAP-AoSAP gradient (6 mm Hg) was increased 10 mm Hg by nitroglycerin and was not affected by prostacyclin. The nitroglycerin-induced increase in systolic gradient RaSAP-AoSAP correlated to decreases in stroke volume index, mean arterial pressure, and arterial elastance, but not to decrease in pulse wave augmentation. Thus, decreases in stroke volume index, not wave reflection, seem to be the main reason for an increased RaSAP-AoSAP when nitroglycerin is used in the elderly, hypertensive patient. IMPLICATIONS: We studied ascending aortic and radial pulse contours in patients scheduled for coronary artery surgery. The radial pulse wave can be used for interpretation of central hemodynamic changes during nitroglycerin-, but not prostacyclin-, induced hypotension.     

Diltiazem infusion for renal protection in cardiac surgical patients with preexisting renal dysfunction

OBJECTIVE: To evaluate if the calcium channel blocker diltiazem protects postoperatively renal function in cardiac surgical patients with preexisting mild-to-moderate renal dysfunction. DESIGN: Prospective, randomized, placebo-controlled, double-blind, clinical study. SETTING: Cardiothoracic anesthesia department at a university hospital. PARTICIPANTS: Adult patients undergoing elective cardiac surgery using cardiopulmonary bypass, with a preoperatively elevated serum creatinine level (n = 24). INTERVENTIONS: Randomized infusions of diltiazem (bolus 0.25 mg/kg followed by a continuous infusion of 1.7 microg/kg/min) (DTZ, n = 12) or placebo (C, n = 12) were started 30 minutes before induction of anesthesia and continued for 24 hours. MEASUREMENTS AND MAIN RESULTS: Median plasma concentrations of diltiazem (DTZ group) were 79 microg/L before cardiopulmonary bypass, 67 microg/L at the end of cardiopulmonary bypass, and 164 microg/L at 24 hours postoperatively. Serum creatinine levels; on postoperative days 1, 3, and 5; and 3 weeks postoperatively were similar between groups. Iohexol clearance did not differ between the groups on day 5 but was higher in the DTZ group than in the placebo group 3 weeks after surgery (median, 51 v 40 mL/min/1.73 m(2); p < 0.05). Urinary N-acetyl-beta-glucosamidase concentrations were similar between the groups during the study but were increased from baseline on days 2 and 4 and 3 weeks postoperatively. CONCLUSION: Diltiazem can be safely used in patients who have mild-to-moderate renal dysfunction and undergo cardiac surgery using cardiopulmonary bypass. Within the limits of this study, the data suggest that addition of prophylactic diltiazem may prevent further glomerular damage resulting from cardiopulmonary bypass and may improve glomerular function 3 weeks after cardiac surgery.     

Central–to–peripheral arterial pressure gradient during cardiopulmonary bypass: relation to preand intra–operative data and effects of vasoactive agents

A significant central–to–peripheral arterial pressure gradient may exist during and after cardiopulmonary bypass (CPB). The etiology and mechanisms of this phenomenon remain controversial. We studied the pressure gradient between aorta, brachial artery and radial artery in 68 patients, scheduled for elective coronary artery bypass surgery. We evaluated whether choice of cardioprotection during CPB (use of cold cardioplegic solution or use of intermittent crossclamping under protection with lidoflazine), and choice of pulsatile or nonpulsatile flow during the course of CPB, affected the magnitude and duration of the systolic pressure gradient. We also studied whether central–to–peripheral pressure gradient was influenced by administration on CPB of different vasoactive drugs with different mode of action: sodium nitroprusside (direct action on the vessels), droperidol (alpha–adrenergic blocking action), ketanserin (5–hydroxytryptamine antagonist) and phenylephrine (selective alpha,–agonist).
It appeared that central–to–peripheral gradient occurred early during CPB and remained constant throughout the course of CPB. The gradient disappeared within 60 min after weaning from CPB. We found the main pressure gradient to occur between the brachial and the radial artery. There was no relation between magnitude of the gradient and sex, weight, length or age of the patient. There was also no relation between magnitude of the pressure gradient and type of cardioprotection, choice of pulsatile vs nonpulsatile flow on CPB and duration of CPB. We also found no relation between pressure gradients and changes in temperature, haematocrit and systemic vascular resistance. The pressure gradient was not affected by any of the vasoactive drugs.     

The use of dexmedetomidine in pediatric cardiac surgery

We tested dexmedetomidine, an alpha2 agonist, for its ability to decrease heart rate, arterial blood pressure, and neuroendocrinal responses during pediatric cardiac surgery. In a randomized, placebo-controlled study, 30 pediatric patients undergoing open heart surgery were randomly assigned to one of two equal groups. The control group received saline, whereas the treatment group (DEX group) received an initial bolus dose of dexmedetomidine (0.5 microg/kg) over 10 min, followed immediately by a continuous infusion of 0.5 microg.kg(-1).h(-1). Arterial blood pressure, heart rate, and sequential concentrations of circulating cortisol, epinephrine, norepinephrine, and blood glucose were measured. Relative to baseline, arterial blood pressure and heart rate decreased significantly after the administration of dexmedetomidine through skin incision. In the control group, patients' heart rate and arterial blood pressure measures increased after skin incision until the end of bypass (P < 0.05). In both groups, plasma cortisol, epinephrine, norepinephrine, and blood glucose increased significantly relative to baseline, after sternotomy, and after bypass. However, the values were significantly higher in the control group compared with the DEX group (P < 0.05). In conclusion, intraoperative dexmedetomidine infusion attenuated the hemodynamic and neuroendocrinal response to surgical trauma and cardiopulmonary bypass in pediatric patients undergoing corrective surgery for congenital heart disease.     

Postoperative intensive care in infants and children after cardiac surgery

Background The postoperative course of infants and children after open heart surgery is often complicated by cardiopulmonary insufficiency or low cardiac output. Methods From January 1989 to April 1992 441 infants and children with congenital heart disease underwent cardiac surgery. 128 of these patients (29%) required prolonged or extensive intensive care because of cardiopulmonary insufficiency or low cardiac output. Aortic cross clamp and cardiopulmonary bypass times were measured in all patients. In the postoperative period duration of mechanical ventilation, duration of intensive care, special monitoring and therapeutic strategies and clinical scores were documented. Results The overall mortality rate was 9.9%, the mortality rate in patients with postoperative cardiopulmonary insufficiency or low cardiac output was 34%. The mortality rate increased significantly up to 73% when the cardiopulmonary bypass time exceeded 200 min. Mean duration of intensive care of survivors (S) and nonsurvivors (NS) was 10.3±0.8 and 4.1±1.2 days, respectively (p<0.01), mean duration of mechanical ventilation was 7.1±0.5 (S) and 4.1±1.2 (NS) days, respectively (p<0.01). NS had a significantly higher degree of physiologic derangement assessed by the Acute Physiologic Score for Children and needed more monitoring and therapeutic interventions assessed by the Therapeutic Intervention Scoring System than S. Conclusion Complex cardiac surgery, a cardiopulmonary bypass time over 200 min, high catecholamine infusion rates combined with a persisting low mean arterial pressure are associated with a high postoperative mortality rate in infants and children with congenital heart defects.