Preoperative and perioperative use of levosimendan in cardiac surgery: European expert opinion.

In cardiac surgery, postoperative low cardiac output has been shown to correlate with increased rates of organ failure and mortality. Catecholamines have been the standard therapy for many years, although they carry substantial risk for adverse cardiac and systemic effects, and have been reported to be associated with increased mortality. On the other hand, the calcium sensitiser and potassium channel opener levosimendan has been shown to improve cardiac function with no imbalance in oxygen consumption, and to have protective effects in other organs. Numerous clinical trials have indicated favourable cardiac and non-cardiac effects of preoperative and perioperative administration of levosimendan. A panel of 27 experts from 18 countries has now reviewed the literature on the use of levosimendan in on-pump and off-pump coronary artery bypass grafting and in heart valve surgery. This panel discussed the published evidence in these various settings, and agreed to vote on a set of questions related to the cardioprotective effects of levosimendan when administered preoperatively, with the purpose of reaching a consensus on which patients could benefit from the preoperative use of levosimendan and in which kind of procedures, and at which doses and timing should levosimendan be administered. Here, we present a systematic review of the literature to report on the completed and ongoing studies on levosimendan, including the newly commenced LEVO-CTS phase III study (NCT02025621), and on the consensus reached on the recommendations proposed for the use of preoperative levosimendan.

Cardiac outcome after sevoflurane versus propofol sedation following coronary bypass surgery: a pilot study.

BACKGROUND: Studies of volatile anesthetic administration during coronary artery bypass grafting (CABG) report reduced serum levels of post-operative cardiac troponin-T (cTnT). Our primary objective was to evaluate whether short-term sedation with sevoflurane in the intensive care unit (ICU)--after CABG--could affect the release of cTnT, compared with propofol sedation. METHODS: Following isolated CABG with cardiopulmonary bypass, 100 patients were randomized to either sevoflurane via the Anesthetic Conserving Device (AnaConDa(®)) or propofol for ICU sedation. Study drugs were administered for 2 h during mechanical ventilation and thereafter until extubation criteria were met. The primary endpoint was cTnT 12 h post-operatively. Crude cTnT data were not normally distributed and therefore compared with the Mann-Whitney U-test. Because of the skewed pre-operative and post-operative cTnT data, we performed a post hoc analysis of the change in cTnT between pre-operative values and 12 h post-operatively. RESULTS: There was no statistically significant difference between groups in the primary endpoint cTnT values at 12 h post-operatively, cardiac events or the need for hemodynamic support. In the post hoc analysis, the cTnT increase from pre-operative values to 12 h post-operatively was less pronounced in the sevoflurane group (P=0.008). CONCLUSION: Post-operative short-term sevoflurane sedation following CABG, in comparison with propofol, did not affect the cTnT values at 12 h post-operatively and clinical outcome was equal between groups. The result from the post hoc analysis, with less cTnT change over time, is nevertheless hypothesis-generating and warrants a larger study.

Plasma concentrations following repeated rectal or intravenous administration of paracetamol after heart surgery.

BACKGROUND: Paracetamol is commonly used for post-operative pain management in combination with more potent analgesics. The best route of paracetamol administration after major surgery, when oral intake may not be optimal, is not known. Our primary purpose was to study plasma concentrations after the 1st and 4th dose of 1 g of paracetamol given either rectally or intravenously (i.v.) after major surgery. METHODS: In this prospective, randomized study, 48 patients undergoing heart surgery were randomized upon arrival to the intensive care unit (ICU) to receive paracetamol every 6th hour either as suppositories or intravenous injections. In half the patients (n = 24), blood samples for paracetamol concentration were obtained before and 20, 40 and 80 min after the first dose. In the other patients (n = 24), additional samples were taken prior to, and at 20, 40, 80 min and 4 and 6 h after, the 4th dose. RESULTS: Plasma paracetamol concentration peaked (95 +/- 36 micromol/l) within 40 min after initial i.v. administration but did not increase within 80 min after the 1st suppository. Plasma concentration before the 4th dose was 74 +/- 51 and 50 +/- 27 in the rectal and i.v. groups, respectively. Paracetamol concentration peaked 20 min after the 4th dose for the i.v. patients (210 +/- 84 micromol/l) and declined to 99 +/- 27 micromol/l at 80 min as compared with the rectal patients 69 +/- 44 to 77 +/- 48 micromol/l. CONCLUSION: Both time course and peak plasma concentrations of paracetamol given rectally differ from the one seen after intravenous administration. The clinical impact of these differences needs further investigation.

Effects of thoracic epidural analgesia on glucose homeostasis after cardiac surgery in patients with and without diabetes mellitus.

BACKGROUND AND OBJECTIVE: Even moderate hyperglycaemia increases mortality/morbidity after coronary artery bypass grafting, stroke and myocardial infarction. The goal of this prospective study was to determine if using thoracic epidural analgesia from start of surgery until the end of the third postoperative day would blunt postoperative hyperglycaemia. METHODS: Forty-four patients had diabetes mellitus, 60 did not; half of each group had an epidural with continuous local anaesthetics. All patients received continuous insulin infusions during the initial 24 h period beginning with surgery. Blood glucose was measured four times daily (fasting or 2-3 h post-prandial) until end of the third postoperative day. RESULTS: For patients without diabetes, the epidural group had lower mean blood glucose and insulin requirements (P < 0.02) than controls during the initial 24 h period beginning with surgery. For patients with diabetes mellitus, thoracic epidural analgesia reduced mean blood glucose (P = 0.017) with unchanged insulin requirements. Epidural did not diminish the increase (vs. preoperative) in fasting blood glucose on the third postoperative day (32% vs. 22%, P < 0.001) for non-diabetics. Epidural analgesia was not able to attenuate hyperglycaemia during the first 3 postoperative days. CONCLUSIONS: Epidural analgesia improved glucose homeostasis minimally during the initial 24 postoperative hours but did not attenuate hyperglycaemia during the subsequent 3 postoperative days.

Are even impaired fasting blood glucose levels preoperatively associated with increased mortality after CABG surgery?

AIMS: Impaired fasting glucose (IFG) below the diagnostic threshold for diabetes mellitus (DM) is associated with macrovascular pathology and increased mortality after percutaneous coronary interventions. The study goal was to determine whether pre-operative fasting blood glucose (fB-glu) is associated with an increased mortality after coronary artery bypass grafting (CABG). METHODS AND RESULTS: During 2001-03, 1895 patients underwent primary CABG [clinical DM (CDM) in 440/1895; complete data on fB-glu for n=1375/1455]. Using pre-operative fB-glu, non-diabetics were categorized as having normal fB-glu (<5.6 mmol/L), IFG (5.6< or =fB-glu<6.1 mmol/L), or suspected DM (SDM) (> or =6.1 mmol/L). fB-glu was normal in 59%. The relative risks of 30 day and 1 year mortality compared with patients with normal fB-glu was 1.7 [95% confidence interval (CI): 0.5-5.5] and 2.9 (CI: 0.8-11.2) with IFG, 2.8 (CI: 1.1-7.2) and 1.9 (CI: 0.5-6.3) with SDM vs. 1.8 (CI: 0.8-4.0) and 1.6 (CI: 0.6-4.3) if CDM, respectively. The receiver operator characteristic area for the continuous variable fB-glu and 1 year mortality was 0.65 (P=0.002). CONCLUSION: The elevated risk of death after CABG surgery known previously to be associated with CDM seems also to be shared by a group of similar size that includes patients with IFG and undiagnosed DM.

Clinical comparison of three different anaesthetic depth monitors during cardiopulmonary bypass.

The lack of a gold standard complicates the evaluation and comparison of anaesthetic depth monitors. This randomised study compares three different depth-of-anaesthesia monitors during cardiopulmonary bypass (CPB) at 34 degrees C with fentanyl/propofol anaesthesia adjusted clinically and blinded to the monitors. Coronary artery bypass grafting patients (n = 21) were randomly assigned to all three possible paired combinations of three monitors: Bispectral Index (Aspect Medical), AAI auditory evoked potential (Danmeter), Entropy (Datex-Ohmeda). Indices were manually recorded every 5 min during CPB. Agreement between paired indices was classified as good, non-, or disagreement. Anaesthesia was classed as adequate, inadequate, or excessive according to recommended index values. Of the 255 paired indices recorded, 62% showed good agreement, 33% showed non-agreement, and 5% showed disagreement. Using good agreement between two monitors as a gold standard, a quarter of the measurements indicate inappropriate anaesthetic depth monitoring during CPB with clinically titrated anaesthetic depth.

Early bioavailability of paracetamol after oral or intravenous administration.

BACKGROUND: Paracetamol is a peripherally acting analgesic commonly used in multimodal post-operative pain management to reduce the need for more potent analgesics with their unwanted side-effects. The dose and optimal galenical form for achieving analgesic concentrations is not well defined. The primary aim of this pilot project was to study the early bioavailability for two fixed doses of orally administrated paracetamol and one dose of intravenous propacetamol, all of which were given after minor surgery. METHODS: Thirty-five patients undergoing day surgery were divided into five groups, seven patients each. Groups received either 1 g of an ordinary paracetamol tablet, 2 g of an ordinary paracetamol tablet, 1 g of a bicarbonate paracetamol tablet, 2 g of a bicarbonate paracetamol tablet or 2 g intravenously of prodrug propacetamol. We studied the plasma concentration of paracetamol during the first 80 min after administration. RESULTS: Within 40 min, intravenous propacetamol gave a median plasma paracetamol concentration of 85 micromol/l (range 65-161) and decreased thereafter. After oral administration, median plasma paracetamol concentration increased with increasing dose and time, but there were huge inter-individual differences at all time points studied. At 80 min after oral paracetamol the median plasma concentrations were 36 and 129 micromol/l for the 1- and 2-g groups, respectively, with an overall range between 0 and 306 micromol/l. CONCLUSION: Oral administration of paracetamol as part of multimodal pain management immediately post-operatively resulted in a huge and unpredictable variation in plasma concentration compared with the intravenous administration.

Entropy during propofol hypnosis, including an episode of wakefulness.

Depth of anaesthesia has proved to be a complex process to quantify. Monitors based on bispectral analysis of the electroencephalogram and auditory evoked potential have been available, but only recently has a monitor based on entropy become available. This study determined state entropy and response entropy in nine healthy volunteers during propofol hypnosis with a brief intervening period of wakefulness. Both the calculated entropy indices decreased with increasing levels of sedation (r2 = 0.58 and 0.61, respectively) and they showed a high correlation with each other (r2 = 0.94). However, an overlap was observed in real time indices between different stages of the Observer's Assessment of Alertness/Sedation Scale. Only three of the nine volunteers had explicit memories from the episode of wakefulness. Electroencephalographic entropy monitors seem to have potential for staging clinical hypnotic effects.

Being awake intermittently during propofol-induced hypnosis: a study of BIS, explicit and implicit memory.

BACKGROUND: Being awake during anaesthesia is a serious complication. An anaesthetic depth monitor must discriminate in real time between wakefulness and unconsciousness. The present study created a period of wakefulness during propofol-induced hypnosis. Bispectral index (BIS), explicit and implicit memories of the awake period were investigated. METHODS: Ten volunteers were studied. The calculated brain concentration of a target controlled infusion of propofol was increased until loss of response (LOR) to verbal command and then propofol was stopped. When fully awake, volunteers were presented with a picture, sound and smell. Propofol infusion was restarted until LOR and then ceased. BIS and the calculated brain concentration of propofol were recorded every minute. A structured interview was conducted for explicit memories after awakening and for explicit as well as implicit memories the day after. RESULTS: Median BIS-index for the transition between awake and asleep and vice versa differed significantly. It was not possible, however, to establish any threshold value or zone for discriminating between wakefulness and LOR due to the large inter-individual variations in BIS-index. No volunteer could explicitly recall any of the stimuli presented during the period of wakefulness. CONCLUSION: The BIS-index decreases with increasing sedation but because of the large individual variations, the real-time BIS-index for the individual subject cannot reliably discriminate wakefulness from unconsciousness during propofol infusion. Propofol causes such profound amnesia that lack of postoperative recall does not assure that episodes of awareness have not occurred during propofol-induced hypnosis.

Retrograde crystalloid cardioplegia preserves left ventricular systolic function better than antegrade cardioplegia in patients with occluded coronary arteries.

OBJECTIVE: To investigate retrograde and antegrade crystalloid cardioplegia in terms of cardiac cooling and postoperative cardiac function. DESIGN: Prospective, randomized, and blinded. SETTING: University hospital. PARTICIPANTS: Twenty male patients with triple-vessel disease and proximal occlusion of the circumflex or the left anterior descending coronary artery. INTERVENTIONS: Left ventricular ejection fraction at rest and during exercise was evaluated by nuclear ventriculography the day before and 3 months after surgery. After induction of anesthesia and hourly for the first 5 postoperative hours, hemodynamic, echocardiographic, and electrocardiographic data were acquired. Myocardial temperature was measured with needle thermistors in 3 myocardial regions. MEASUREMENTS AND MAIN RESULTS: Demographic and temperature data were analyzed by t-test. Hemodynamic and echocardiographic data were analyzed by analysis of variance. The groups were similar in baseline characteristics. Retrograde cardioplegia cooled the region distal to an occlusion better than antegrade cardioplegia (9.6 degrees C +/- 4.8 degrees C v 21.8 degrees C +/- 5.9 degrees C; p < 0.01). Hemodynamic, echocardiographic, and electrocardiographic data did not differ between the groups. Three months after surgery, the retrograde cardioplegia group showed a higher left ventricular ejection fraction at rest (58% +/- 10% v 47% +/- 10%; p < 0.02) and during exercise (58% +/- 13% v 47% +/- 10%; p < 0.05) compared with the antegrade cardioplegia group. CONCLUSIONS: Retrograde cardioplegia provides more homogenous myocardial cooling than antegrade cardioplegia in hearts with coronary artery occlusions. The use of retrograde cardioplegia seems to benefit long-term left ventricular function.

Effects on the bispectral index during medium-high dose fentanyl induction with or without propofol supplement.

BACKGROUND: The search for a drug-independent monitor to determine depth of anaesthesia and hypnosis continues. The bispectral analysis (BIS) of the EEG correlates well with the clinical dose-response of hypnotic drugs during induction, but the effect on BIS of an opiate induction, as for coronary bypass surgery, is not known. METHODS: Fourteen patients scheduled for elective coronary bypass surgery were studied. BIS was recorded during induction in 7 patients receiving 10 microg/kg fentanyl without any hypnotic agent and in 7 patients receiving 0.5 mg/kg propofol before the fentanyl dose. RESULTS: The effect of fentanyl was very variable both regarding BIS and clinical response. Five of the 7 patients that received only fentanyl lost their response to verbal command within 8 min. BIS values at loss of response varied between 45 and 94. One patient remained awake with BIS 43. All 7 patients receiving propofol before the fentanyl dose lost their response to verbal command within 5 min. BIS values at the time for loss of response varied between 78 and 98. CONCLUSION: Loss of response to verbal command when a medium-high dose of fentanyl is used for induction cannot be distinguished from wakefulness with adequate sensitivity by BIS. The current BIS algorithm seems not to accurately reflect the hypnotic effects of fentanyl.

Myocardial outflow of prostacyclin in relation to metabolic stress during off-pump coronary artery bypass grafting.

BACKGROUND: The metabolic changes, possible myocardial damage, and influence on the vascular endothelium during off-pump coronary artery bypass grafting have been investigated. METHODS: Coronary sinus and arterial blood samples were obtained before coronary arterial occlusion, after 10 minutes of ischemia, and after 1 and 10 minutes of reperfusion in 9 patients who had an anastomosis performed to the left anterior descending coronary artery off-pump bypass RESULTS: The mean ischemic time was 14 +/- 1 minutes. The arteriovenous difference in lactate decreased during ischemia to reach a minimum at 1 minute of reperfusion (-0.15 +/- 0.06 micromol/L compared to 0.21 +/- 10 micromol/L before ischemia; p < 0.01). Myocardial lactate extraction decreased from 14.2 +/- 6.8 micromol/min before ischemia to -10.9 +/- 6.5 micromol/min after 1 minute of reperfusion (p < 0.01). Simultaneously, the arteriovenous difference in 6-keto-PGF(1alpha), the stable metabolite of prostacyclin, decreased from -30 +/- 26 pg/mL to -258 +/- 80 pg/mL at 1 minute of reperfusion (p < 0.05), and the 6-keto-PGF(1alpha) extraction over the heart decreased -556 +/- 466 pg/min to -18,560 +/- 5,683 pg/min (p < 0.01). CONCLUSIONS: The localized myocardial ischemia associated with these procedures causes changes in the myocardium and endothelial influence. Coronary bypass surgery performed on the beating heart may not be superior in preventing cardiac ischemia and endothelial disturbance, compared with conventional bypass surgery.

Fentanyl and midazolam anaesthesia for coronary bypass surgery: a clinical study of bispectral electroencephalogram analysis, drug concentrations and recall.

Bispectral index (BIS) was assessed as a monitor of depth of anaesthesia during fentanyl and midazolam anaesthesia for coronary bypass surgery. In 10 patients given morphine premedication, anaesthesia was induced with a combination of midazolam and fentanyl and thereafter maintained with a continuous infusion of a mixture of midazolam and fentanyl 5 and 50 micrograms kg-1 h-1, respectively. BIS was recorded continuously but not shown to the attending anaesthetist. Plasma concentrations of midazolam and fentanyl were measured five times during the procedure. An auditory stimulus was given during bypass. All patients were interviewed twice after operation for explicit and implicit recall. No patient had any anaesthetic complications. BIS decreased during anaesthesia, but varied considerably during surgery (range 36-91) with eight patients having values > 60. Midazolam and fentanyl drug concentrations did not correlate with BIS. No patient reported explicit or implicit recall. During clinically adequate anaesthesia with midazolam and fentanyl BIS varies considerably. The most likely reason is that BIS is not an accurate measure of the depth of anaesthesia when using this combination of agents.

Patient-controlled versus nurse-controlled pain treatment after coronary artery bypass surgery.

BACKGROUND: Pain after coronary artery bypass surgery persists for several days. A continuous intravenous infusion of an opioid adequately accomplishes good pain control in the intensive care unit, but it is often not suitable on the ordinary ward. Patient-controlled analgesia (PCA) with intermittent injections delivered by one of the new devices now available could be an alternative to conventional nurse-controlled analgesia (NCA) based on intermittent injections. The aim was to compare these two techniques with respect to efficacy and the amount of opioid used. METHODS: Forty-eight patients randomly received PCA or NCA with ketobemidone following extubation after coronary artery bypass grafting. Drug consumption, pain assessment with the visual analogue score (VAS) and possible side effects were evaluated from extubation to the end of the second postoperative day. RESULTS: On the day of surgery the VAS scores did not differ between the groups. From the afternoon of the first postoperative day the VAS scores were higher in the NCA group with mean values at 3-4 out of 10 as compared with mean values around 2 in the PCA group (P<0.01). During the study period the patients in the PCA group received more ketobemidone as compared with the NCA group, 61.9+/-24.0 mg and 36.3+/-20.2 mg, respectively (P<0.01). Additional oral analgesics were used in 12 of the patients in the NCA group compared with none in the PCA group. The few side effects reported were equally distributed between the two groups. CONCLUSION: PCA treatment after coronary artery bypass surgery resulted in better pain treatment and the use of more opioid without an increase in side effects compared with traditional NCA treatment.

Nitrous oxide does not alter bispectral index: study with nitrous oxide as sole agent and as an adjunct to i.v. anaesthesia.

We have studied the effect of nitrous oxide on bispectral index (BIS), calculated from a bipolar encephalogram. Inhalation of 70% nitrous oxide resulted in loss of consciousness in all healthy volunteers (n = 10) but no change in BIS. Brief inhalation up to 1.2% sevoflurane also resulted in loss of consciousness in volunteers (n = 5), but with sevoflurane, BIS decreased. BIS and the haemodynamic effects of adding nitrous oxide were also measured during coronary artery bypass surgery in patients (n = 10) receiving midazolam and fentanyl infusions. Measurements were made after 0%, 33%, 66% and 0% nitrous oxide, just before skin incision and after sternotomy. Nitrous oxide caused no change in BIS. BIS may indicate a sufficient hypnotic depth to prevent awareness during surgery, but our study demonstrated that pharmacological unconsciousness-hypnosis can also be reached by mechanisms to which BIS is not sensitive. Thus BIS is a sufficient but not a necessary criterion for adequate depth of anaesthesia or prevention of awareness.

Myocardial outflow of calcitonin gene-related peptide in relation to metabolic stress during coronary artery bypass grafting without cardiopulmonary bypass.

OBJECTIVE: Because of adverse effects of cardiopulmonary bypass and the prospect of shortening intensive care and hospital stay, coronary artery bypass grafting without cardiopulmonary bypass is gaining increased attention. The impact of the localized myocardial ischemia that is inherent in these procedures has not been thoroughly investigated in human beings. We have investigated metabolic changes, possible myocardial damage, and myocardial outflow of the vasodilator calcitonin gene-related peptide during coronary artery bypass grafting without cardiopulmonary bypass. METHODS: Coronary sinus and arterial blood was sampled before coronary arterial occlusion, after 10 minutes of ischemia, and after 1 and 10 minutes of reperfusion in 9 consecutive patients (mean age 70 +/- 5 years) who had an anastomosis performed to the left anterior descending artery without cardiopulmonary bypass. RESULTS: No perioperative myocardial infarctions occurred. The arteriovenous difference in lactate decreased during ischemia, to reach a minimum after 1 minute of reperfusion (-0.17 +/- 0.25 vs 0.15 +/- 0.25 mmol/L before ischemia; P =.008). Myocardial lactate extraction decreased (from 11.2 +/- 13.6 micromol/min before ischemia to -3.0 +/- 7.0 micromol/min after 1 minute of reperfusion; P =.012), that is, a net production of lactate. The arteriovenous difference in calcitonin gene-related peptide decreased from -0.1 +/- 2.6 pmol/L before ischemia to -30.5 +/- 26.5 pmol/L (P =.008) after 1 minute of reperfusion. CONCLUSIONS: The localized myocardial ischemia associated with these procedures causes metabolic changes in the myocardium, but no myocardial damage. The ischemia-related outflow of calcitonin gene-related peptide indicates that the vasodilating and cardioprotective properties of this peptide that are known from animal studies may be of importance in myocardial ischemia in human beings.

Myocardial perfusion after coronary artery bypass surgery. A study using ectomographic myocardial scintigraphy and adenosine provocation.

A study was conducted to determine the time dependency of myocardial perfusion improvement after coronary artery bypass graft (CABG) surgery. Seventeen 3-vessel diseased patients (16 male, 1 female) scheduled for CABG surgery from a cardiac surgical and intensive-care unit were examined. Ten of the 17 patients returned for examination after 1 year. A titrated adenosine infusion was used to expose reversible ischemia. Tc99m-sestamibi was injected at rest and at maximum adenosine infusion rate, and isotope distribution was determined using ectomographic myocardial scintigraphy. Visually scored percent isotope uptake defect size and percent uptake reduction were assessed. It was found that resting isotope uptake defects were unchanged 1 h after surgery, increased in severity after 1 week, and after 1 year were 24% less than the preoperative scores (p < 0.01) and 55% less than after 1 week (p < 0.001). It was found that adenosine infusion induced a 57% increase in average defect score preoperatively (p < 0.001) but no increase postoperatively. No differences were seen between regions supplied by arterial or venous grafts. Isotope uptake defects increased between 1 h and 1 week after CABG surgery, and after 1 year the scores were less than those recorded preoperatively and after 1 week. Adenosine-induced reversible isotope uptake changes seen preoperatively were eliminated postoperatively in all vessel regions.

Changes in human coronary sinus blood flow and myocardial metabolism induced by ventricular fibrillation and defibrillation.

BACKGROUND: During implantation of cardioverter-defibrillators, repeated inductions of ventricular fibrillation and defibrillation are performed. Little is known about the myocardial metabolism associated with ventricular fibrillation and defibrillation in humans. METHODS: Sixteen patients scheduled for transvenous cardioverter-defibrillator implantation were included in the study. In 10 of the patients, blood samples were taken simultaneously in the coronary sinus and radial artery and analyzed for PO2, PCO2, standard bicarbonate, pH, lactate, alanine, glucose, and glycerol. Oxygen saturation, base excess, and oxygen content were calculated. The patients were studied before, shortly after, and 2 and 5 minutes after successful defibrillation. In six of the patients, coronary sinus blood flow was registered continuously. RESULTS: The coronary sinus blood flow declined from a basal value of 93 +/- 16 mL/min to 35 +/- 6 mL/min 14 +/- 2 seconds after induction of ventricular fibrillation. Following termination of ventricular fibrillation, coronary sinus blood flow increased to a peak value of 227 +/- 75 mL/min. Oxygen saturation, PO2, and oxygen content in the coronary sinus increased by approximately 25% shortly after each episode of ventricular fibrillation and defibrillation. The coronary sinus lactate increased and the arterio-coronary sinus lactate difference decreased shortly after each of the four episodes, but was normalized within 2 minutes. CONCLUSIONS: Repeated threshold tests during defibrillator implantation did not cause any long-lasting or cumulative metabolic effects, indicating that the described technique, with a 5-minute recovery period in between episodes, is safe as regards myocardial metabolism.

Brief episodes of ventricular fibrillation do not influence postischemic cerebral perfusion assessed by positron emission tomography.

OBJECTIVES: To establish the defibrillation threshold in patients receiving an implantable cardioverter defibrillator, at least three episodes of ventricular fibrillation are induced and converted back to regular rhythm, using direct current countershocks. The aim of this study was to examine the influence of repeated short episodes of ventricular fibrillation on global and regional cerebral perfusion. DESIGN: A prospective, descriptive study. SETTING: A positron emission tomography laboratory at a university hospital. PATIENTS: Four patients, admitted for defibrillation threshold tests 2 yrs after the implantation of a cardioverter defibrillator, were included in the study. Global and regional cerebral blood flow was measured by cerebral positron emission tomography, using an 15O-labeled tracer under propofol-induced general anesthesia. Electroencephalograms (EEGs) were concomitantly recorded. INTERVENTIONS: Induction and conversion of ventricular fibrillation. MEASUREMENTS AND MAIN RESULTS: No effect on global cerebral perfusion was observed after induced ventricular fibrillation lasting 21 +/- 3 secs. The average global cerebral perfusion was 23 +/- 1 mL/100 g/min after induction of anesthesia and 31 +/- 8 mL/100 g/min and 24 +/- 2 mL/100 g/min immediately after the termination of the first and second ventricular fibrillation episodes, respectively. Ten minutes after the second and the third threshold tests, global cerebral perfusion was 21 +/- 1 mL/100 g/min and 21 +/- 2 mL/100 g/min, respectively. Regional cerebral perfusion and EEGs were not influenced. CONCLUSION: Short episodes of ventricular fibrillation did not induce any measurable effects on global and regional cerebral perfusion detectable by positron emission tomography 30 secs and 10 mins after restitution of sinus rhythm.

Hemodynamic response to adenosine infusion before and after coronary artery bypass surgery.

This study describes the hemodynamic dose-response characteristics of a titrated, continuous adenosine infusion before and 1 h (anesthetized), 1 week, and 1 year after coronary artery bypass graft (CABG) surgery. Average tolerated adenosine infusion rates were less 1 h and 1 week after surgery (128 +/- 23 and 118 +/- 27 microg/kg/min, respectively) than before (156 +/- 29 microg/kg/min) and 1 year after surgery (156 +/- 24 microg/kg/min). Heart rate (HR) increased with a 120-microg/kg/min adenosine infusion rate both preoperatively (21 +/- 11%) and 1 year postoperatively (16 +/- 8%). Systolic blood pressure (BP) decreased 26 +/- 11%, 14 +/- 7%, and 9 +/- 6% with 120 microg/kg/min adenosine for the three postoperative examinations. The integral of the outflow tract velocity with 120 microg/kg/min adenosine increased 49 +/- 22% and 29 +/- 12% after 1 h and 1 week, respectively, whereas its product with HR increased equally for all examinations (40 +/- 22%, 62 +/- 27%, 46 +/- 13%, and 39 +/- 11%). The average preoperative left ventricular area shortening was 45 +/- 10% and neither it nor end-diastolic left ventricular area (preload) changed with surgery, time after surgery, or with adenosine. A titrated adenosine infusion is well suited to patients requiring a pharmacologic provocation to expose reversible myocardial ischemia during the first hours or days after CABG surgery. The anesthetized and anemic patient are particularly unsuited for the commonly used fixed-infusion-rate protocol.