Comparison of the hemodynamic effects of sevoflurane anesthesia induction and maintenance vs TIVA in CABG surgery

PURPOSE

To compare the hemodynamic effects of sevoflurane when used for induction and maintenance of anesthesia with a total intravenous technique in patients with known coronary artery disease (CAD).

METHODS

Thirty patients undergoing elective coronary artery bypass graft (CABG) were randomly allocated to receive either sevoflurane (S group, n = 15) at a minimal concentration of 4% in oxygen for induction and at 0.5-2 MAC end-tidal concentration for maintenance, or a total intravenous technique (T group, n = 15) consisting of midazolam for induction and propofol for maintenance. In both groups, anesthesia was supplemented with sufentanil and muscle relaxation with cis-atracurium. Hemodynamic measurements included systemic and pulmonary pressures, heart rate, mixed venous oxygen saturation and cardiac output at the following times: pre-induction, 7 and 25 min post-induction, chest closure, one hour after surgery and pre and post tracheal extubation.

RESULTS

More patients in the S group (8/15) presented bradycardia in the induction period (T:2/15) (P = 0.05). During maintenance of anesthesia, treatment of hypertension was more frequent in the T group (12/15) than in the S group (6/15) (P = 0.025). All other parameters were comparable.

CONCLUSION

Induction of anesthesia in patients with CAD, VCRII with sevoflurane supplemented by sufentanil provided hemodynamic responses comparable with those of TIVA although bradycardia was observed more often with sevoflurane. Intraoperative control of systemic blood pressure was achieved with fewer interventions with a sevoflurane/sufentanil maintenance than with a propofol/sufentanil technique in CABG surgery.

A two-center study evaluating the hemodynamic and pharmacodynamic effects of cisatracurium and vecuronium in patients undergoing coronary artery bypass surgery

OBJECTIVE

To determine the hemodynamic and pharmacodynamic effects of rapid bolus administration of cisatracurium compared with vecuronium.

DESIGN

A randomized, prospective, double-blind study.

SETTING

Tertiary-care university hospitals.

PARTICIPANTS

Seventy-nine adult patients with diagnosed coronary artery disease (CAD).

INTERVENTION

Elective coronary artery bypass graft surgery (CABG).

MEASUREMENTS AND MAIN RESULTS

Patients were randomly divided into four groups. Patients received a rapid bolus of two or four times the 95% peak depression of twitch (ED95) of either cisatracurium (groups 1 and 2) or vecuronium (groups 3 and 4). Three minutes after a midazolam induction, all patients received a rapid bolus administration of either study drug. Maintenance of anesthesia was with a standardized propofol-sufentanil-oxygen anesthetic. Patients were monitored with radial and pulmonary artery catheters and electromyography. End points of the study were hemodynamic stability at induction, after bolus administration of study drugs, and after intubation; the quality of intubating conditions; drug interventions to correct hemodynamic instability; the onset, duration, and recovery of neuromuscular function; and drug cost. Mean arterial pressure (MAP) and heart rate (HR) decreased in a similar proportion in all four groups after induction while, following study drug administration, MAP and HR did not change significantly. Both cisatracurium groups required more boluses to maintain neuromuscular block, but spontaneous recovery rates were faster. Both agents, but cisatracurium to a lesser degree, showed increased duration with repeated maintenance doses. Both agents afforded good to excellent intubating conditions, but the cost of cisatracurium was significantly less.

CONCLUSION

The authors conclude there is no evidence of a hemodynamic difference between the two neuromuscular blocking drugs (NMBDs). There are some clinical and cost advantages in favor of cisatracurium.

Can L-arginine improve myocardial protection during cardioplegic arrest? Results of a phase I pilot study

BACKGROUND

L-arginine appears to improve myocardial protection during cardioplegic arrest in animal models.

METHODS

To study the clinical effect and safety of L-arginine in humans, a phase I pilot study was performed with 50 patients who underwent coronary artery bypass grafting. We randomly assigned half to a treatment group, which received 1 g of L-arginine administered during the first 30 minutes of cardioplegic arrest induced by either warm or cold blood cardioplegia, and half to a control group, which did not receive L-arginine supplementation.

RESULTS

Age, sex, and preoperative clinical status were similar in both groups. Seventeen patients of each group were administered intermittent warm antegrade blood cardioplegia, whereas the solution needed to be cooled to obtain complete standstill of the remaining eight hearts in each group. An internal thoracic artery graft to the left anterior descending coronary artery was performed in all patients. There was no death and no myocardial infarction in the treatment group, but there were one death and two infarctions in the control group. The amount of serial release of troponin I during the first 72 hours after the operation was similar between the L-arginine group and the control group (p > 0.05). Peak serum troponin levels averaged 4.9 +/- 1.0 microg/L in the arginine group and 3.9 +/- 1.0 microg/L in the control group (p > 0.05). A multivariate analysis of variance showed no effect of L-arginine (p > 0.05) but a significant effect of the temperature of the cardioplegic solution on the release of troponin I (p < 0.05). Serum troponin I levels averaged 2.2 +/- 0.4 microg/L, 4.5 +/- 0.4 microg/L, and 6.9 +/- 0.4 microg/L in the patients with cold cardioplegia and 1.4 +/- 0.3 microg/L, 2.4 +/- 0.3 microg/L, and 3.3 +/- 0.3 microg/L in the patients with warm cardioplegia 1, 2, and 6 hours, respectively, postoperatively.

CONCLUSIONS

The administration of 1 g of L-arginine during the first 30 minutes of blood cardioplegic arrest did not result in a decrease in the postoperative release of cardiac enzyme; however, cold cardioplegic arrest significantly increased the release of cardiac troponin I postoperatively. There was no significant side effect related to the addition of L-arginine to the cardioplegic solution.

Does retrograde administration of blood cardioplegia improve myocardial protection during first operation for coronary artery bypass grafting?

BACKGROUND

The objective of this study was to evaluate the value of retrograde blood cardioplegia in coronary artery bypass grafting.

METHODS

In 1994 and 1995, 224 patients undergoing first-time isolated coronary artery bypass grafting were randomized to antegrade (112 patients, group 1) or retrograde (112 patients, group 2) administration of blood cardioplegia. In group 1, 76 patients were given warm cardioplegia (at 33 degrees C) and 36 had cold cardioplegia (< 20 degrees C), whereas in group 2 cardioplegia was warm in 77 patients and cold in 35. The two randomization groups had similar demographic and angiographic characteristics. The number of grafted coronary arteries averaged 2.9 +/- 0.7 in group 1 and 2.8 +/- 0.7 in group 2. Total duration of cardiopulmonary bypass (78 +/- 23 and 75 +/- 21 minutes) and of aortic cross-clamping (47 +/- 16 and 46 +/- 16 minutes), total volume of infusion of the crystalloid component of cardioplegia (988 +/- 297 and 1016 +/- 595 mL), and total duration of infusion of cardioplegia (23 +/- 10 and 22 +/- 11 minutes) were similar (p > 0.05).

RESULTS

There was no death in group 1 and one in group 2 as a result of a pulmonary embolus, for a global early mortality of 0.45%. The numbers of perioperative myocardial infarction (5 versus 3), congestive heart failure (4 versus 5), postoperative hemorrhage (4 versus 4), and stroke (1 versus 2) were also similar (p > 0.05). Release curves of total creatine kinase, creatine kinase-MB by serum activity and mass concentration, and troponin T were not significantly different (p > 0.05) between the two groups. For the 216 patients without perioperative myocardial infarction, peak enzyme release of creatine kinase-MB at 24 hours averaged 23 +/- 22 and 20 +/- 18 IU/L, and that of troponin T averaged 1.1 +/- 1.1 and 1.3 +/- 1.5 micrograms/L at 6 hours for the antegrade and the retrograde groups, respectively (p > 0.05).

CONCLUSIONS

Our results indicate no evidence that the retrograde method of cardioplegic infusion improves myocardial protection during first operation for isolated coronary revascularization compared with the usual antegrade route.

Propofol or midazolam for sedation and early extubation following cardiac surgery

PURPOSE

The purpose of this randomized, double-blind study was to evaluate the efficacy of midazolam and propofol for postoperative sedation and early extubation following cardiac surgery.

METHODS

ASA physical status II-III patients scheduled to undergo elective first-time cardiac surgery with an ejection fraction > 45% were eligible. All patients received a standardized sufentanil/isoflurane anaesthesia. During cardiopulmonary bypass 100 micrograms.kg-1.min-1 propofol was substituted for isoflurane. Upon arrival in the Intensive Care Unit (ICU), patients were randomized to either 10 micrograms.kg-1.min-1 propofol (n = 21) or 0.25 microgram.kg-1.min-1 midazolam (n = 20). Infusion rates were adjusted to maintain sedation within a predetermined range (Ramsay 2-4). The infusion was terminated after four hours. Patients were weaned from mechanical ventilation and their tracheas extubated when Haemodynamic stability, haemostasis, normothermia and mental orientation were confirmed. Haemodynamic measurements, arterial blood gas tensions and pulmonary function tests were recorded at specified times.

RESULTS

There were no differences between the two groups for the time spent at each level of sedation, number of infusion rate adjustments, amount of analgesic and vasoactive drugs, times to awakening and extubation. The costs of propofol were higher than those of midazolam. There were no differences in haemodynamic values, arterial blood gas tensions and pulmonary function.

CONCLUSION

We conclude that midazolam and propofol are safe and effective sedative agents permitting early extubation in this selected cardiac patient population but propofol costs were higher.

Comparison of sevoflurane/fentanyl and isoflurane/fentanyl during elective coronary artery bypass surgery. Sevoflurane Venture Group

PURPOSE

Due to the progressive aging of the surgical population, the proportion of patients with coronary artery disease (CAD) is likely to increase. The effects of the new inhalational anaesthetic sevoflurane must be determined in patients with known CAD.

METHODS

This multicentre, randomized, open-label study compared the haemodynamic and cardiovascular effects of sevoflurane and isoflurane with fentanyl in 284 ASA physical status II-IV patients undergoing elective coronary artery bypass graft (CABG).

RESULTS

Satisfactory records were available in 272 patients, 139 sevoflurane (Group S) and 133 isoflurane (Group I). There were no differences between groups for demographic data except that more patients in Group S were taking preoperative beta-blockers (P = 0.03). The mean end-tidal MAC and MAC.hr requirements between groups were not different (Group S received 0.63 +/- 0.02 MAC and 1.00 +/- 0.05 MAC. hr while Group I received 0.58 +/- 0.02 MAC and 0.92 +/- 0.05 MAC. hr P = NS). The preCPB use of intravenous fentanyl was not different between groups. There was a similar decrease in haemodynamic variables in both groups after induction that persisted throughout the preCPB period. The incidence of preCPB myocardial ischaemia, adverse haemodynamic events and use of vasoactive drugs did not differ between groups. The incidence of postoperative myocardial infarction was 2.2% for Group S and Group I was 4.5% (P = NS). There were five postoperative deaths, one of which was attributed to a cardiac cause (Group I).

CONCLUSION

In patients undergoing elective CABG with low risk factors, either sevoflurane or isoflurane, combined with fentanyl, provided an acceptable preCPB haemodynamic profile and cardiac outcomes.

An evaluation of the N-CAT, a new arterial tonometer

The N-CAT is a newly developed arterial tonometer (TBP) monitor able to determine systolic, diastolic and mean blood pressures continuously and noninvasively. The aim of this study was to evaluate the accuracy and reliability of the TBP compared with directly measured invasive blood pressure (IBP) in 14 patients before and after elective coronary artery bypass surgery. Although the TBP was able to track changes in systemic pressure, before and after CPB, bias and precision for TBP monitoring did not meet the standard criteria for equivalency for noninvasive blood pressure to invasive blood pressure. We were unable to monitor TBP in two patients. Approximately 40% of all before and after CPB mean TBP pressure values differed from mean IBP by more than 10 mmHg. Moreover, there were discrepancies of sufficient magnitude and duration that limits the clinical usefulness of the N-CAT. Potential users should not rely exclusively on TBP values when making clinical decisions. Technological improvement is needed before its clinical use is recommended.

Hemodynamic and pharmacodynamic comparison of doxacurium and high-dose vecuronium during coronary artery bypass surgery: a cost-benefit study

Doxacurium (DOX), a new nondepolarizing neuromuscular blocking drug (NMBD), was compared in a randomized, double-blind fashion to high-dose vecuronium (VEC) in 60 coronary artery bypass grafting (CABG) patients. A third group of 15 patients older than 70 years of age (DOX-70) was added to compare the effects of DOX to VEC in the older population. Endpoints of the study were hemodynamic stability, ease of ventilation and intubation, anesthesiologist's satisfaction, drug interventions to correct hemodynamic instability, and total cost of the drug. Anesthesia was induced with fentanyl (30 micrograms/kg) along with the NMBD (DOX 80 micrograms/kg, VEC 400 micrograms/kg) over a 2-minute period. Following induction, heart rate (HR) and mean arterial pressure (MAP) were decreased (P < 0.01) in all groups. Tracheal intubation caused the HR to return to baseline in the DOX-70 group. There was no difference in central venous pressure, pulmonary artery occlusive pressure, cardiac index, systemic vascular resistance, and drug intervention for DOX and VEC. None of the patients had evidence of myocardial ischemia. There was a statistically significant but clinically irrelevant decrease in central venous pressure and systemic vascular resistance in the DOX-70 group. The durations of the induction and maintenance doses of DOX were similar in the younger and older patients. Although the intubating dose of VEC had a faster onset of action, this had no effect on the ease of ventilation, conditions for tracheal intubation, and overall anesthesiologist satisfaction. The total cost for each NMBD was not different.(ABSTRACT TRUNCATED AT 250 WORDS)

Hydromorphone patient-controlled analgesia (PCA) after coronary artery bypass surgery

We conducted a study to compare the effectiveness of patient-controlled analgesia (PCA) technique to conventional analgesic therapy (CAT) after coronary artery bypass graft (CABG). The PCA group received hydromorphone 0.1 mg.hr-1 basal infusion and bolus doses of 0.2 mg Q 5 min (maximum 1.2 mg.hr-1) while the CAT group received morphine 2.5 mg iv Q 30 min prn until extubation followed by prn meperidine 1 mg.kg-1 im Q 4 hr or acetaminophen 325 mg with codeine 30 mg po (1 or 2 tablets) when oral intake was possible. The degree of pain was assessed using a Visual Analogue Scale (VAS) starting after extubation and every 6-8 hr for the next 60 hr. Holter monitoring was initiated one hour after patient arrival in the Intensive Care Unit (ICU) and continued for 72 hr. Other measured variables were pulmonary function, sedation, side effects and total opioid requirements. Results show that the day-to-day VAS pain score decreased in the PCA group (P < 0.001) while it remained unchanged in CAT patients. The PCA patients had lower VAS pain scores at extubation (P < 0.05). During the third postoperative day, the PCA group had a lower VAS pain score, a lower incidence of severe pain defined as a score > 5 on the VAS scale, and a reduced incidence of myocardial ischaemia (P < 0.01). However, there was no difference in the duration, severity, area under the curve (AUC), or heart rate during ischaemic events. Postoperative pulmonary function was abnormal in both groups (NS) with minimal recovery by the fourth day.(ABSTRACT TRUNCATED AT 250 WORDS)

Propofol in patients with cardiac disease

Propofol is an intravenous anaesthetic which is chemically unrelated to other iv anaesthetics. Most anaesthetists are now becoming familiar with propofol's pharmacokinetic and pharmacodynamic properties. It has proved to be a reliable drug that can be used safely for induction and maintenance of anaesthesia for most surgical procedures and unlike other anaesthetic agents, it can especially be extended into the postoperative setting or intensive care unit for sedation. Propofol's greatest attributes are its pharmacokinetic properties which result in a rapid, clear emergence and lack of cumulative effects even after prolonged administration. Compared with other iv anaesthetics, the induction dose of propofol has a relatively higher incidence of respiratory depression, short-lived apnoea and blood pressure reduction that may occasionally be marked. Possible mechanisms for the hypotension may relate to (1) its action on peripheral vasculature (vasodilatation), (2) decreased myocardial contractility, (3) resetting of the baroreflex activity and (4) inhibition of the sympathetic nervous system outflow. In vitro studies indicate that propofol depresses the immunological reaction to bacterial challenge as well as the chemotactic activity. Clinical studies, in cardiac surgery, have demonstrated that propofol, in association with an opioid, is a logical anaesthetic choice. Propofol is about to receive approval for continuous iv sedation. Comparative studies of propofol and midazolam have clearly demonstrated the superiority of propofol in terms of rapid recovery and precise control of the level of sedation.

Assessment of the arterial tonometer (N-CAT) for the continuous blood pressure measurement in rapid atrial fibrillation

The N-CAT is a newly developed arterial tonometer (TBP) able to determine systolic, diastolic and mean arterial blood pressures continuously and noninvasively. The aim of this study was to evaluate the accuracy and reliability of TBP relative to directly measured invasive blood pressure (IBP) in ten haemodynamically stable postoperative cardiac patients who were in rapid atrial fibrillation (HR > or = 100 bpm). There were differences between TBP and IBP for systolic (-1.7 mmHg) and diastolic (+0.9 mmHg) values but not for the mean arterial blood pressures. The N-CAT was able to follow blood pressure changes closely and demonstrated an average systolic, diastolic and mean bias (+/-SD) of -1.71 +/- 4.6, 0.99 +/- 4.6 and 0.33 +/- 4.2 mmHg, respectively. Although these biases are within the required standards for equivalency for noninvasive blood pressure to invasively determined blood pressure, approximately 20% of the readings were > +/- 10 mmHg while only 5% were > +/- 20 mmHg. Moreover, there were occasional discrepancies of sufficient magnitude and duration which may limit the clinical usefulness of the N-CAT in patients in whom continuous and accurate blood pressure measurement is required.

Endothelial vasomotor regulation in health and disease

The purpose of this review is to provide the anaesthetists with a comprehensive update on the endothelial-cell control of local blood flow. This single cell layer was originally thought to represent only a passive barrier. It is now evident that it plays an active role in a broad variety of biological functions. Since the discovery of the endothelial-derived relaxing factor (EDRF), it has been the subject of a considerable amount of research. It is established that EDRF is secreted continuously at a basal state and that many physical stimuli as well as vasoactive substances can modulate its secretion. Evidence presented indicates that the endogenous vasodilatation produced by EDRF is similar to that of the exogenous nitrovasodilator nitroglycerin and nitroprusside (i.e., nitric oxide). Aside from EDRF, the endothelium produces other vasodilating as well as vasoconstricting factors. A review of the physiology of the endothelium regarding the local control of blood flow is provided along with its influence upon several pathophysiological states. Also included is an overview of the influence of anaesthetic agents on endothelial function. These findings linking vasomotor control to endothelial function will help to explain pathophysiological process and may lead to new therapeutic modalities.