Fentanyl-oxygen anaesthesia for coronary artery surgery: cardiovascular and antidiuretic hormone responses

Establishment and validation of a predictive nomogram for polyuria during general anesthesia in thoracic surgery

BACKGROUND

To develop and evaluate a predictive nomogram for polyuria during general anesthesia in thoracic surgery.

METHODS

A retrospective study was designed and performed. The whole dataset was used to develop the predictive nomogram and used a stepwise algorithm to screen variables. The stepwise algorithm was based on Akaike's information criterion (AIC). Multivariable logistic regression analysis was used to develop the nomogram. The receiver operating characteristic (ROC) curve was used to evaluate the model's discrimination ability. The Hosmer-Lemeshow (HL) test was performed to check if the model was well calibrated. Decision curve analysis (DCA) was performed to measure the nomogram's clinical usefulness and net benefits. P < 0.05 was considered to indicate statistical significance.

RESULTS

The sample included 529 subjects who had undergone thoracic surgery. Fentanyl use, gender, the difference between mean arterial pressure at admission and before the operation, operation type, total amount of fluids and blood products transfused, blood loss, vasopressor, and cisatracurium use were identified as predictors and incorporated into the nomogram. The nomogram showed good discrimination ability on the receiver operating characteristic curve (0.6937) and is well calibrated using the Hosmer-Lemeshow test. Decision curve analysis demonstrated that the nomogram was clinically useful.

CONCLUSIONS

Individualized and precise prediction of intraoperative polyuria allows for better anesthesia management and early prevention optimization.

The Genotoxicity of Acrylfentanyl, Ocfentanyl and Furanylfentanyl Raises the Concern of Long-Term Consequences

Three fentanyl analogues Acrylfentanyl, Ocfentanyl and Furanylfentanyl are potent, rapid-acting synthetic analgesics that recently appeared on the illicit market of new psychoactive substances (NPS) under the class of new synthetic opioids (NSO). Pharmacotoxicological data on these three non-pharmaceutical fentanyl analogues are limited and studies on their genotoxicity are not yet available. Therefore, the aim of the present study was to investigate this property. The ability to induce structural and numerical chromosomal aberrations in human lymphoblastoid TK6 cells was evaluated by employing the flow cytometric protocol of the in vitro mammalian cell micronucleus test. Our study demonstrated the non-genotoxicity of Fentanyl, i.e., the pharmaceutical progenitor of the class, while its illicit non-pharmaceutical analogues were found to be genotoxic. In particular, Acrylfentanyl led to a statistically significant increase in the MNi frequency at the highest concentration tested (75 μM), while Ocfentanyl and Furanylfentnyl each did so at both concentrations tested (150, 200 μM and 25, 50 μM, respectively). The study ended by investigating reactive oxygen species (ROS) induction as a possible mechanism linked to the proved genotoxic effect. The results showed a non-statistically significant increase in ROS levels in the cultures treated with all molecules under study. Overall, the proved genotoxicity raises concern about the possibility of serious long-term consequences.

Cardiothoracic Anesthesia and Critical Care in the United Kingdom (UK) Part 1: Some Insights Into the History and Development

This review is intended to highlight some of the historic events that contributed to the development of thoracic and cardiac anesthesia and surgery in Great Britain and Northern Ireland (UK). The aim of this first of two parts is to concentrate on the development of techniques, facilities, and pharmacology that allowed progress and advancement in patient management that were developed primarily in the UK. However, progress usually requires input from a wide variety of sources of knowledge, and cardiothoracic practice is no exception. Reference is, thus, made to sources outside of the UK that guided, influenced, or inspired changes in practice, such as the techniques of operating on the heart and great vessels in war casualties, developed by Dr. Dwight Harken, or the demonstration of the Blalock-Thomas-Taussig shunt by Alfred Blalock. In addition to advances in medical equipment, such as computed tomography, the UK contributed greatly to pharmacologic interventions that were unique at the time in such varied areas as nonflammable volatile anesthetic agents, heart failure treatments, and neuromuscular blocking agents for both cardiac and thoracic surgical practice.

The fentanyl story

Fentanyl, introduced more than 50 years ago, has become the most often used opioid for intraoperative analgesia. Since the early 1990s the fentanyl patch has been available for management of chronic pain of all forms of cancer as well as the persistent, intense pain from many noncancerous maladies. More than a half dozen rapid-onset transmucosal fentanyl preparations have been developed, approved, launched, and popularized for "breakthrough" pain syndromes in the past 20 years. The purpose of this article is to describe why this opioid has become so important in the treatment of pain in modern clinical practice. The data indicate that fentanyl's popularity has occurred because it has minimal cardiovascular effects, does not result in increases in plasma histamine, is relatively short in onset of action and duration of effect, is easy and inexpensive to synthesize and prepare for the marketplace, and is now familiar to clinicians working in pain and perioperative medicine throughout the world.

A case of transient central diabetes insipidus after aorto-coronary bypass operation

Diabetes insipidus (DI) is characterized by excessive urination and thirst. This disease results from inadequate output of antidiuretic hormone (ADH) from the pituitary gland or the absence of the normal response to ADH in the kidney. We present a case of transient central DI in a patient who underwent a cardiopulmonary bypass (CPB) for coronary artery bypass grafting (CABG). A 44-yr-old male underwent a CABG operation. An hour after the operation, the patient developed polyuria and was diagnosed with central DI. The patient responded to desmopressin and completely recovered five days after surgery. It is probable that transient cerebral ischemia resulted in the dysfunction of osmotic receptors in the hypothalamus or hypothalamus-pituitary axis during CPB. It is also possible that cardiac standstill altered the left atrial non-osmotic receptor function and suppressed ADH release. Therefore, we suggest that central DI is a possible cause of polyuria after CPB.

Dose-response relationship of propofol on mid-latency auditory evoked potentials (MLAEP) in cardiac surgery

BACKGROUND

Propofol-sufentanil anaesthesia has become popular during cardiac surgery for its titrability and short recovery time. Avoidance of awareness is a major goal during cardiac surgery. We therefore investigated the dose-response relationship of propofol and cortical responses (mid-latency auditory evoked potentials, MLAEP).

METHODS

One hundred patients undergoing cardiac surgery were investigated. Basic anaesthesia was performed with sufentanil (4.5 microg kg(-1) h(-1)) / flunitrazepam (9 microg kg(-1) h(-1)) infusion (control group); the other groups received in addition a loading dose of propofol 2 mg kg(-1) and a maintainance infusion of 1-3.5 mg kg(-1) h(-1). MLAEP were evaluated by using Pa/Nb-amplitudes and Nb-latencies. Haemodynamics were monitored by ECG, arterial blood pressure and cardiac function with pulmonary artery catheterization.

RESULTS

In the control group, median amplitude of MLAEP decreased by 50% with a wide range, but were detectable in >90% of patients throughout surgery. Propofol suppressed amplitude Pa/Nb of MLAEP dose dependently. With 3.5 mg kg(-1) h(-1) amplitudes disappeared in >40% of patients throughout cardiac surgery. Median Nb-latencies increased in the control group from 44 to a range from 50 to 60 ms. In groups with propofol >2 mg kg(-1) h(-1), Nb-latencies, detectable in the patients without complete suppression of MLAEP, increased to median 60 ms. Haemodynamic parameters and cardiac function did not differ among the groups. The use of vasopressors was not increased even with the highest propofol dose used.

CONCLUSION

The dose-response effect of propofol on auditory evoked potentials reveals that combining a loading dose of 2 mg kg-1 with a consecutive infusion of 3.5 mg kg(-1) h(-1) significantly suppresses MLAEP during cardiac surgery. Thus, auditory information may not be processed and awareness with recall becomes unlikely.

The effects of intrinsic vasopressin on urinary aquaporin-2 excretion and urine osmolality during surgery under general anesthesia

A radioimmunoassay has been established to measure urinary aquaporin-2 excretion (u-AQP2). To elucidate how u-AQP2 changes when endogenous vasopressin is increased independently of plasma osmolality, we estimated u-AQP2 during general anesthesia for surgery. We collected urine and blood samples from 50 patients before and 90 and 180 min after anesthetic induction. Plasma (29.1+/-12.6 pg/mL) and urinary (565.1+/-207.0 ng/gCr) vasopressin levels were markedly increased after anesthetic induction. Although no significant alteration of plasma osmolality or serum sodium concentration was observed during 180 min, u-AQP2 was significantly increased (preinduction 224.5+/-24.2 fmol/ mgCr; 90 min 243.3+/-31.8; 180 min 331.4+/-45.9), paralleling an increase of plasma and urinary vasopressin. The plasma vasopressin concentration after anesthetic induction was far in excess of that expected based on plasma osmolality. Individual plasma and urinary vasopressin concentrations correlated significantly with u-AQP2. At 180 min after anesthesia, plasma osmolality did not change, but urine osmolality decreased despite increased u-AQP2, and a preanesthetic positive correlation between urine osmolality and u-AQP2 disappeared. Thus, although u-AQP2 correlates with increased intrinsic vasopressin levels, the increase in u-AQP2 did not directly contribute to urine concentration. Apparently, an escape from the physiologic effects of high vasopressin level occurs during anesthesia via a mechanism independent of aquaporin-2. We conclude that the anesthetic would interfere with the urinary concentrating capacity at the level of AQP2-action.

IMPLICATIONS

The excessive increase of intrinsic vasopressin exactly augmented urinary aquaporin-2 excretion, resulting in urine concentration; however, anesthesia seemed to modify this process possibly by interfering with the aquaporin-2 action.

Effect of non-pulsatile renal blood flow on plasma erythropoietin

Erythropoietin is a hormone responsible for regulation of red blood cell production. Circulating erythropoietin values are regulated by renal oxygen supply, which is determined by hemoglobin concentration, hemoglobin oxygen saturation, and renal blood flow. Previous animal and human studies regarding erythropoietin regulation have assumed pulsatile renal blood flow. During cardiopulmonary bypass, non-pulsatile renal perfusion has been shown to result in decreased glomerular filtration rate and decreased renal blood flow in comparison to pulsatile perfusion. Repair of congenital heart disease during cardiopulmonary bypass is an attractive circumstance in which to study the effect of non-pulsatile blood flow on erythropoietin production. The hypothesis in this study was that non-pulsatile perfusion would result in increased erythropoietin production because of decreased renal oxygen supply. Fourteen children with congenital heart disease and without preoperative renal insufficiency or anemia were enrolled in the study. All patients underwent cardiopulmonary bypass with non-pulsatile flow. In addition, 10 control patients without congenital heart disease were enrolled. Six cardiopulmonary bypass patients had 1.5- to 6-fold increases in plasma erythropoietin concentrations from baseline. These patients had longer cardiopulmonary bypass times, more commonly performed under low flow deep hypothermic conditions. The remaining 8 patients with congenital heart disease, and all control patients, did not develop increased postoperative erythropoietin concentrations. The conditions under which cardiopulmonary bypass are performed appear to influence postoperative circulating erythropoietin concentrations.

Vasopressin Levels in Major Head and Neck Surgery

In an effort to further understand the perioperative intravascular volume status of major head and neck surgery patients, serum antidiuretic hormone (ADH) and osmolality levels were assessed at four perioperative junctures. Thirty-five major head and neck surgical patients were randomly selected for examination with placement of a central venous pressure monitor. Serum osmolality and serum vasopressin levels were obtained at four junctures perioperatively. ADH levels were lower both after patients were anesthetized and five hours into the procedure than at either baseline or 24 hours after the end of the procedure. ADH levels after patients were anesthetized did not differ from those at five hours into the procedure, nor did ADH levels at baseline differ from those 24 hours after the end of the procedure. In addition, osmolality levels did not change over time. Additional analyses examining relationships between preoperative, intraoperative, and postoperative characteristics and ADH levels after patients were anesthetized and five hours into the procedure, as well as changes from baseline at these times and the baseline levels themselves, detected no significant relationships. This study provides information about the perioperative intravascular volume status of major head and neck surgery patients which may be important to intraoperative care, especially to decisions regarding invasive intraoperative fluid monitoring. Specifically, the data provide additional evidence against the need for the routine placement of central venous catheters to guide fluid administration during major head and neck surgery.

Cardiovascular effects of different infusion rates of sufentanil in patients undergoing coronary surgery

OBJECTIVE

Pharmacokinetics and haemodynamic effects of a total dose of 15 micrograms.kg-1 sufentanil, an opioid anaesthetic agent, were studied in patients undergoing aortocoronary bypass surgery at three infusion rates of 30 (group I), 5 (group II), and 2 (group III) micrograms.kg-1.min-1, respectively.

RESULTS

Plasma concentrations of sufentanil could be optimally characterized by a linear biexponential pharmacokinetic model. Non-compartmental analyses indicated that there was no significant difference in the values of clearance (11.6, 13.3, 14.3 ml.min-1.kg-1), steady-state volume of distribution (0.220, 0.255 and 0.331 l.kg-1) and mean residence time (18.8, 13.3 and 14.3 min) among the groups. The observed mean Cmax values of 421 (group I), 125 (group II), and 53 (group III) ng.ml-1 and observed mean AUC values from 0 to 3 min were all consistent with the dosing regimens. There were large inter-individual variations in haemo-dynamic response. Compared to plasma data, a delay in haemodynamic effects was found. Times to reach peak haemodynamic effect ranged from 4.3 to 4.9 min for group I, from 4.6 to 6.1 min for group II, and from 9.9 to 11.3 for group III. Except heart rate, peak haemodynamic effects in these study patients generally ranged from 20.9% to 35.2%. Significant reductions in the area under the effect-time profiles of mean arterial blood pressure and systemic vascular resistance were observed in group II and group III, but not in group I. Significant reductions in the area under the effect-time profiles of left ventricular stroke work index were observed in group III only. No effect on heart rate was found in any group.

CONCLUSION

Our findings suggested that a slower infusion rate of sufentanil at a dose of 15 micrograms.kg-1 tends to give a greater reduction in mean arterial blood pressure, systemic vascular resistance, and left ventricular stroke work index than does a faster infusion rate.

Propofol-alfentanil versus fentanyl-midazolam in coronary artery surgery

OBJECTIVE

To compare intraoperative hemodynamics profiles and recovery characteristics of propofol-alfentanil with fentanyl-midazolam anesthesia in elective coronary artery surgery.

DESIGN

Prospective, randomized study.

SETTING

University hospital.

PARTICIPANTS

Fifty patients with impaired or good left ventricular function.

INTERVENTIONS

In group 1, (n = 25) anesthesia was induced with an infusion of propofol, 3 to 4 mg/kg/h, alfentanil, 500 micrograms, and pancuronium 0.1 mg/kg, and maintained with propofol, 3 to 6 mg/kg/h (variable rate), and alfentanil infusions, 30 micrograms/kg/h (fixed rate). Additional boluses of alfentanil, 1 mg, were administered before noxious stimuli; group 2 (n = 25) received a loading dose of fentanyl, 25 micrograms/kg, midazolam, 1.5 to 3 mg, and pancuronium, 0.1 mg/kg for induction, followed by an infusion of fentanyl, 7 micrograms/kg/h, for maintenance. Additional boluses of midazolam (1.5 to 3 mg) and fentanyl (250 micrograms) were administered before noxious stimuli. MEASUREMENTS AND MAIN RESULTS. Cardiovascular parameters at eight intraoperative time points as well as time to extubation, morphine consumption, and pain scores were recorded. Induction of anesthesia was associated in both groups with a small but significant decrease in mean arterial pressure (1: 15 mmHg (15%); 2: 8 mmHg (8%) with significant decreases in cardiac index (1: 8%; 2: 8%) and left ventricular stroke work index (1: 24%; 2: 21%). Throughout surgery, hemodynamic profiles were comparable between groups except after intubation when the MAP was significantly lower in group 1 (75 +/- 12 mmHg) than in group 2 (89 +/- 17 mmHg). Group 1 required less inotropic support. Extubation was performed faster in group 1 (7.6 h) than in group 2 (18.0 h). Morphine requirements and pain scores were comparable between groups.

CONCLUSIONS

Propofol-alfentanil anesthesia provides good intraoperative hemodynamics and allows early extubation after coronary artery surgery.

Haemodynamic effects of high-dose vecuronium compared with pancuronium in beta-blocked patients with coronary artery disease during fentanyl-diazepam-nitrous oxide anaesthesia

BACKGROUND

Different combinations of neuromuscular blockers and opioids have been used in patients with angina pectoris to provide cardiovascular stability and reduce risk of myocardial ischaemia during anaesthesia.

METHODS

We have compared the haemodynamic effects of high-dose vecuronium (0.3 mg kg-1) with those of a standard dose of pancuronium (0.1 mg kg-1) in patients scheduled for coronary artery bypass grafting during fentanyl-diazepam-nitrous oxide anaesthesia. All patients were receiving beta-adrenergic blocking agents. The given doses of vecuronium and pancuronium are equieffective with respect to duration of neuromuscular blockade.

RESULTS

During a 25-min experimental period following the administration of the randomly selected drug, no significant changes in the haemodynamic parameters were observed in the vecuronium group. The administration of pancuronium, however, resulted in a significant mean increase in heart rate (20%), rate-pressure product (23%) and cardiac index (21%). Following endotracheal intubation in the pancuronium group, we observed an additional significant increase in mean arterial pressure and rate-pressure product.

CONCLUSION

High-dose administration of vecuronium has minimal haemodynamic effects and may thus offer a better alternative than pancuronium for long-lasting neuromuscular blockade in patients with coronary artery disease during fentanyl-diazepam-nitrous oxide anaesthesia.

Haemodynamic interaction of high-dose fentanyl and increasing doses of vecuronium in patients undergoing myocardial revascularization

BACKGROUND

Bradyarrhythmia has been reported with vecuronium when given with high dose narcotics. We hypothesized that if the bradycardic response is dependent on a vagal reaction mediated by narcotics, it should be independent of the vecuronium dose. A dose-related response of vecuronium on heart rate (HR) would be in favour of a chronotropic action of this agent.

METHODS

We examined three induction techniques using high doses of fentanyl in which vecuronium was given in increasing doses. In addition, a reference group received a low dose of atracurium. Forty patients scheduled for elective CABG surgery were anaesthetized with fentanyl (50 mu g/kg) given over 5 min, and were randomly assigned to receive either 0.056, 0.14, 0.28 mg/kg of vecuronium or 0.28 mg/kg of atracurium. Haemodynamic measurements were obtained at the following intervals: before induction (time 0), after the administration of fentanyl (at 5 min), and 1, 2 and 5 min after tracheal intubation (at 10, 11 and 15 min).

RESULTS

In vecuronium-treated groups, there were significant decreases in HR, mean arterial pressure, and cardiac output (P<0.05). There were no differences between the three vecuronium groups. Although the atracurium-treated group displayed no significant haemodynamic changes, 2 patients of this group developed HR < 40 bpm.

CONCLUSIONS

Over the range of vecuronium doses studied, we observed a reduction in HR during induction for CABG surgery with high doses of fentanyl and vecuronium. This effect was not dose dependent and is likely related to a direct effect of a high-dose narcotic technique and/or due to a vagal stimulation regarding the airway procedure.

Antagonization of fentanyl-induced muscular rigidity by neurotensin at the locus coeruleus of the rat

We evaluated the interaction between neurotensin (NT) and mu-opioid receptors at the locus coeruleus (LC), using fentanyl-induced muscular rigidity as our experimental index. Adult, male Sprague-Dawley rats anesthetized with ketamine (120 mg/kg, i.p., with 24 mg/kg/h i.v. infusion supplements) were used. Intravenous injection of fentanyl (100 micrograms/kg) consistently promoted a significant increase in the electromyographic activity recorded from the sacrococcygeus dorsalis lateralis muscle. This implied muscular rigidity was appreciably and dose-dependently antagonized by prior intracerebroventricular (i.c.v.) application of NT (15, 30 or 60 nmol/5 microliter). Microinjection of the tridecapeptide (300 or 600 pmol/100 nl) into the bilateral LC produced similar results. This suppressive effect of NT on fentanyl-induced muscular rigidity was antagonized by simultaneously administered NT antiserum (1:80), or partially blocked by its antagonist, (D-Trp11)-NT (300 pmol), but not by normal rabbit serum (1:80). These results suggest that NT may interact with the mu-opioid receptors at the LC, resulting in the suppression of fentanyl-induced muscular rigidity in the rat.

Cardiac electrophysiologic effects of midazolam combined with fentanyl

Midazolam and fentanyl together produce better sedation, analgesia and amnesia than do either drug alone, but the electrophysiologic effects of the combination are unknown. Twenty patients undergoing electrophysiologic studies for clinical reasons were studied. Blood pressure, heart rate, respiratory rate, oxygen saturation, and standard variables related to atrioventricular and ventriculoatrial conduction, dual pathways, accessory pathway conduction, sinus node function, and the inducibility of tachycardia were examined before and after intravenous injections of midazolam (0.07 +/- 0.03 mg/kg) combined with fentanyl (0.8 +/- 0.4 micrograms/kg). There were no significant changes in the electrophysiologic variables or ease of inducibility of tachycardia. The drugs were well tolerated; they produced minor and clinically unimportant reductions in mean blood pressure (99 +/- 13 to 89 +/- 16 mm Hg; p < 0.001) and respiratory rate (18 +/- 4 to 16 +/- 3 breaths/min; p = 0.05). Excellent sedation was achieved. Major amnesia was reported by 95% of patients. In conclusion, midazolam combined with fentanyl provides safe and effective sedation for electrophysiologic studies without significantly affecting electrophysiologic variables or the inducibility of tachyarrhythmias.

Effects of fentanyl on coronary blood flow distribution and myocardial oxygen consumption in the dog

Little data exist on the effects of fentanyl on coronary blood flow (CBF), myocardial oxygen balance, and the regional distribution of blood flow. These studies were designed to determine whether fentanyl had any intrinsic effects on myocardial oxygen consumption (MVO2) and blood flow distribution. In anesthetized dogs, fentanyl was administered in a dose of 50 micrograms/kg and various measurements were made at 5 and 20 minutes. After hemodynamic recovery from the fentanyl, the animals were treated with atropine to block the known vagomimetic effect of fentanyl and challenged with acetylcholine (3.5 micrograms/kg); then fentanyl (50 micrograms/kg) was again administered and measurements made at 5 and 20 minutes. In the untreated dogs at 5 minutes post-fentanyl, heart rate (HR) decreased 30% and at 20 minutes decreased 29%. Treatment with atropine essentially eliminated HR changes at both time periods. Mean arterial pressure (MAP) fell by 20% and 22% at 5 minutes and 20 minutes, respectively, in the untreated group, but when atropine was administered, MAP was observed to be intermediate between baseline and the untreated animals. Left ventricular MVO2 at 5 minutes in the untreated group was modestly but not significantly reduced. However, at 20 minutes post-fentanyl, MVO2 decreased significantly. MVO2 was essentially unchanged after atropine. Regional CBF (measured by radiolabelled microspheres) was unchanged at 5 minutes, but all layers exhibited significant reductions at 20 minutes. In the atropine group, only the LV epicardial area appeared to show decreases in flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Anaesthesia for myocardial revascularisation. A comparison of fentanyl/propofol with fentanyl/enflurane

We studied the effects on myocardial performance and metabolism of fentanyl/propofol and fentanyl/enflurane anaesthesia in 20 patients before coronary artery bypass grafting. Anaesthesia was induced with fentanyl 20 micrograms.kg-1 and pancuronium 0.15 mg.kg-1. Patients received, by random allocation, either propofol by infusion, 6 mg.kg-1.h-1 reduced by half after 10 min then adjusted as necessary (mean rate 2.8 mg.kg-1.h-1), or enflurane 0.8% inspired concentration for 10 min reduced to 0.6% and adjusted as required (mean 0.7%). Measurements were made before induction, after tracheal intubation, after skin incision and after sternotomy. There were no significant differences between the groups in any haemodynamic variables during the study. Following intubation both groups showed a rise in heart rate (p < 0.01) and cardiac index (p < 0.05). Systemic vascular resistance decreased after intubation (p < 0.05) then returned to baseline during surgery; stroke index was unchanged after intubation but was reduced during surgery (p < 0.01) as systemic vascular resistance increased. Regional and global coronary blood flow were maintained in both groups, as were myocardial oxygen consumption and lactate extraction ratio. However, lactate production did occur in one patient receiving enflurane and Holter monitoring confirmed ischaemia. One patient receiving propofol showed lactate production not accompanied by any ECG changes. This study suggests that propofol may be a suitable alternative to enflurane as an adjunct to opioids in anaesthesia for coronary artery bypass grafting.

Fentanyl-induced muscle rigidity as affected by pretreatment with amantadine hydrochloride

STUDY OBJECTIVE

To determine whether the degree of muscle rigidity in humans caused by the administration of high-dose fentanyl is affected by pretreatment with amantadine hydrochloride, a drug that stimulates the release of dopamine in the basal ganglia.

DESIGN

Randomized, observer-blinded comparison of regimes.

SETTING

Inpatient surgery at a university-affiliated teaching hospital.

PATIENTS

Sixteen patients scheduled for elective surgery in whom the administration of high-dose fentanyl was felt to be appropriate.

INTERVENTIONS

Eight patients in the control group were given diazepam 5 mg orally 1 hour prior to induction of anesthesia. Eight patients in an experimental group were given the same dose of diazepam and also were treated with amantadine 1 g orally in divided doses over a period of 25 hours prior to their scheduled surgery. At the time of surgery, all patients were given fentanyl 50 micrograms/kg intravenously at a rate of 1 mg/min and were clinically evaluated for the degree of muscle rigidity of the chest wall, abdomen, and extremities.

MEASUREMENTS AND MAIN RESULTS

A single observer, blinded to the technique, evaluated and recorded the degree of muscle rigidity present in the chest wall, abdomen, and upper extremities immediately after administration of the fentanyl and 3 minutes later. The observer was the same individual in all instances. In no case did the muscle rigidity compromise our ability to adequately oxygenate the patient.

CONCLUSIONS

Muscle rigidity associated with the administration of high-dose fentanyl is not attenuated by prior administration of amantadine in the dose range studied.

Hemodynamic and hormonal responses to hypothermic and normothermic cardiopulmonary bypass

Normothermic cardiopulmonary bypass (CPB) is used in cardiac surgery at some institutions. To compare hemodynamic and hormonal responses to hypothermic (29 degrees C) and normothermic nonpulsatile CPB, 20 adults undergoing coronary artery bypass graft and/or aortic valve replacement were studied. Hemodynamic measurements and plasma hormone concentrations were obtained from preinduction to the third postoperative hour. The two groups were given similar amounts of anesthetics and vasodilators. Systemic vascular resistance increased only during hypothermic CPB, and heart rate was higher at the end of hypothermic CPB. Postoperative central venous pressure and pulmonary capillary wedge pressure were lower after hypothermic CPB. Oxygen consumption decreased by 45% during hypothermic CPB, did not change during normothermic CPB, but increased similarly in the two groups after surgery; mixed venous oxygen saturation (SvO2) was significantly lower during normothermic CPB. Urine output and composition were similar in the two groups. In both groups, plasma epinephrine, norepinephrine, renin activity, and arginine vasopressin concentrations increased during and after CPB. However, epinephrine, norepinephrine, and dopamine were 200%, 202%, and 165% higher during normothermic CPB than during hypothermic CPB, respectively. Dopamine and prolactin increased significantly during normothermic but not hypothermic CPB. Atrial natriuretic peptide increased at the end of CPB and total thyroxine decreased during and after CPB, with no difference between groups. This study suggests that higher systemic vascular resistance during hypothermic CPB is not caused by hormonal changes, but might be caused by other factors such as greater blood viscosity. A higher perfusion index during normothermic CPB might have allowed higher SvO2.

Coronary artery bypass grafting using two different anesthetic techniques: Part I: Hemodynamic results

Hemodynamic changes were studied during two different anesthetic techniques in 54 patients undergoing coronary artery bypass grafting (CABG). All patients had normal to moderately impaired left ventricular function and were randomly assigned to two groups. In 27 patients, high thoracic epidural analgesia (TEA) with bupivacaine 0.375% plus sufentanil 1:200,000 (ie, 5 micrograms/mL) was used in combination with general anesthesia with midazolam/N2O; in the other 27 patients, general anesthesia (GA) with midazolam and sufentanil was used. After induction of epidural analgesia, heart rate and mean arterial pressure (MAP) decreased. Changes in cardiac index, systemic vascular resistance, and pulmonary capillary wedge pressure were not observed, whereas the stroke volume index increased significantly. After induction of intravenous anesthesia MAP decreased (20%) in both groups. During the pre-bypass period, metaraminol was used in 7 of 27 patients in the GA group and in 5 of 27 patients in the TEA group to treat hypotension. Inotopic drugs were used in 5 patients in the GA group and in none in the TEA group to treat a low CO. Ten GA patients and 4 TEA patients developed hypertension after sternal spread and the GA patients required more nitroprusside. Four GA patients developed electrocardiographic evidence of prebypass ischemia and, therefore, more nitroglycerin was needed for treating myocardial ischemia. More sodium nitroprusside was needed in the GA group during cardiopulmonary bypass (CPB) and the post-bypass period to treat hypertension with a high SVR. In conclusion, hemodynamic stability was more pronounced in the TEA than the GA group before and after CPB.

The history and development of the fentanyl series

In the last two decades, opioid analgesics have assumed an important place in general anesthetic practice in the United States. Part of the reason for this has been the introduction of the potent new agonists fentanyl, sufentanil, and alfentanil. Because of problems with morphine-oxygen anesthesia (incomplete amnesia, occasional histamine-related reaction, marked increases in intra- and postoperative respiratory depression), a suitable alternative was sought but not found among existing opioids. A breakthrough came in 1960, when fentanyl was synthesized, laying the foundation for a better understanding of the structure-activity relationships of narcotic analgesics and stimulating interest in developing compounds with even greater potency and safety margins. Investigators interested in opioid anesthesia began to study fentanyl in animals and then in humans. Fentanyl (50-100 micrograms/kg) with oxygen (100%) was evaluated as an anesthetic in patients undergoing mitral valve and coronary artery surgery. Changes in cardiovascular dynamics with induction doses ranging from 8 to 30 micrograms/kg consisted of small decreases in heart rate and arterial blood pressure. All other cardiovascular variables studied, including cardiac output, remained unchanged, even with additional doses up to 100 micrograms/kg. It was determined that fentanyl had use as a narcotic anesthetic, despite its potential for cardiovascular depression and stimulation, respiratory depression, muscle rigidity, and, occasionally, incomplete anesthesia. Since the introduction of fentanyl, two other potent synthetic opioids have been introduced into clinical practice--sufentanil and alfentanil.

Correlation between myocardial ischemia and changes in arterial resistance during coronary artery bypass surgery

The arterial resistometer provides continuous on-line monitoring of changes in arterial resistance. Resistance index (Ri), which bears a direct relationship to systemic vascular resistance (SVR), is defined by the equation Ri = P'/(dP'/dt), where dP'/dt is the peak dP/dt of the arterial waveform, and P' is the pressure at dP'/dt. In 42 patients with unstable angina, changes in Ri were studied at six periods during aortocoronary bypass surgery before tracheal intubation, during tracheal intubation, leg elevation, presternotomy, sternotomy, and dissection of the internal mammary artery. Thirty-four episodes of ischemia (0.1 mV ST segment changes) were observed in 26 patients. All ischemic episodes were associated with increased Ri (mean increase, 102 +/- 52%). Elevation of the pulmonary capillary wedge pressure correlated with ischemia during the preintubation, intubation, and sternotomy periods, but not in the remaining periods. Changes in arterial pressure and heart rate were not good predictors of ischemia. The prevalence of ST segment changes increased markedly during all periods of anesthesia with increase in Ri (P less than 0.05). Ninety-one percent of ST segment changes were associated with a 25% increase from the baseline Ri. Raising the cutoff point to a greater than or equal to 75% increase in Ri improved the specificity of Ri in ischemia detection from 61% to 92%. An increase of greater than or equal to 75% in Ri occurred in only 8% of cases without ST segment changes. It was found that an increase in Ri as depicted by the arterial resistometer was the best hemodynamic correlate of myocardial ischemia.

A comparative study of five different techniques to reduce left ventricular dysfunction during endotracheal intubation

Thirty-five non-selected, consenting patients were studied during induction of anesthesia before coronary artery bypass grafting. Anesthesia was induced with diazepam, thiopentone and fentanyl, followed by pancuronium. Before induction, 200 MBq Tc 99 m - HSA was given i.v. and ejection fraction (EF) of the left ventricle was measured with a collimated single-crystal probe. The patients were allocated to five groups (seven patients in each) treated with: Group A: nitroglycerin i.v. bolus 4 micrograms x kg-1 given 30-60 s before laryngoscopy; Group B: nitroglycerin i.v. in continuous infusion, 1 micrograms x kg-1 x min-1 started before induction; Group C: two-stage topical anesthesia of the vallecula region and larynx with lidocain; Group D: a combination of nitroglycerin and topical anesthesia (as in Group B and C); and Group E: propranolol i.v. 0.01 mg x kg-1 given 5 min before intubation. All groups reacted in the same way during induction of anesthesia up to the point of laryngoscopy. End-diastolic volume and systemic arterial pressure decreased while cardiac index remained unchanged and EF increased. During laryngoscopy and intubation, however, differences between the groups were evident. Nitroglycerin i.v. as a bolus effectively prevented a reduction in EF and an increase in left ventricular volume. In addition to these beneficial hemodynamic effects, there was a moderate increase in heart rate and a reduction of stroke index. Continuous infusion of nitroglycerin and propranolol i.v. had no effect, since EF fell and left ventricular volume increased. Patients receiving topical anesthesia demonstrated a blunted response to endotracheal intubation with a moderate decrease in EF and an unchanged (Group C) or slightly increased (Group D) left ventricular volume.

Cardiovascular effects of large doses of pentamorphone in the dog

The cardiovascular effects of large doses of pentamorphone were evaluated in nine mongrel dogs basally anesthetized with sodium thiopental, 25 to 30 mg/kg, intravenously. All dogs were mechanically ventilated with 100% oxygen, and the PaCO2 was maintained between 35 and 40 mm Hg. Mean arterial pressure (MAP), central venous pressure, heart rate (HR), cardiac output (CO), pulmonary artery pressure, and pulmonary artery occluded pressure were measured, and stroke volume and systemic and pulmonary vascular resistances were calculated. Baseline measurements were obtained, then pentamorphone, 10 micrograms/mL, was given as an intravenous infusion at 2.5 micrograms/kg/min. Additional data were obtained after infusion of 25, 50, 75, 100, 125, 150, 200, 250, 300, and 350 micrograms/kg of pentamorphone. The inspired gases were then changed to 50% nitrous oxide in oxygen, and after a 20-minute equilibration period, an additional set of data was collected. Pentamorphone, 25 micrograms/kg, decreased HR 50%, MAP 65%, and CO 54%. No further changes in any measured or calculated variables were observed with additional doses of pentamorphone. The addition of 50% nitrous oxide to the inspired gas mixture had no effect on any measured or calculated hemodynamic variable. The minimal hemodynamic effects of pentamorphone in the dog suggest that further investigation into its use as an anesthetic is warranted.

Anticonvulsant therapy increases fentanyl requirements during anaesthesia for craniotomy

This study was designed to determine whether patients receiving chronic anticonvulsant therapy demonstrate an altered requirement for fentanyl during anaesthesia. Sixty-one patients undergoing craniotomy were studied; 20 controls (MED = 0) who had never received anticonvulsants and 41 epileptics in whom therapeutic plasma concentrations of either one (MED = 1), two (MED = 2), or three (MED = 3) different anticonvulsants were documented. During anaesthesia with 60-70 per cent N2O in O2 and 0.2 per cent isoflurane, a maintenance dose (MD) of fentanyl was administered using a continuous variable-rate IV fentanyl infusion, supplemented by intermittent 50 micrograms IV boluses. In order to define the minimal dosage of fentanyl required, the MD was titrated according to increases or decreases in the heart rate and/or mean arterial pressure exceeding 15 per cent of baseline ward values. A progressively higher fentanyl MD was required in the epileptic patients (MED = 1-4.3 +/- 0.5 microgram.kg-1.hr-1; MED = 2-5.4 +/- 0.6; MED = 3-7.6 +/- 0.6) compared with the control MD (MED = 0-2.6 +/- 0.5) (P less than 0.001). These findings indicate that there appears to be a dose-effect relationship between the number of anticonvulsants received and the maintenance dose of fentanyl required during balanced anaesthesia.

Muscle relaxants change myocardial metabolism in patients with ischemic heart disease during high-dose fentanyl anesthesia

Although not unanimously accepted, high-dose fentanyl anesthesia has been associated with hemodynamic stability and little derangement of myocardial oxygen balance. This apparent inconsistency inspired us to investigate the effects on cardiac function and myocardial metabolism of stepwise increasing doses of fentanyl, accumulating to 15, 30, and 50 micrograms.kg-1, with the least possible interference from other drugs. Subjects were unpremedicated patients with ischemic cardiac disease scheduled for coronary artery bypass grafting or major vascular surgery. In an initial study employing succinylcholine for muscle relaxation, we found that heart rate (HR), coronary sinus blood flow (CSF) and coronary vascular resistance (CVR) remained unchanged, while systemic arterial pressure (SBP), rate-pressure product (RPP), coronary perfusion pressure (CPP) and left ventricular work (LVW) decreased. Myocardial uptake of oxygen (MVO2) and free fatty acids (FFA) both decreased in a dose-dependent manner. Arterial lactate concentration and myocardial lactate uptake both increased. These findings opposed the postinduction myocardial ischemia noted by some other investigators. In most of these studies pancuronium bromide had been used for muscle relaxation. Since the latter agent has been claimed to increase cardiac work, a second group of correspondingly diseased patients was studied in which succinylcholine was replaced by pancuronium bromide. In this group HR, RPP, CSF and MVO2 all increased at the lowest dose of fentanyl and HR additionally also at 30 micrograms.kg-1. The cardiac index was higher in the pancuronium group at the lowest and middle dose steps of fentanyl. Lactate uptake decreased with higher doses of fentanyl and relative myocardial lactate extraction declined.(ABSTRACT TRUNCATED AT 250 WORDS)

Variations in hemodynamic and stress hormonal responses in open heart surgery with buprenorphine/diazepam anesthesia

The use of buprenorphine-diazepam-N2O (60%)-O2 anesthesia in open heart surgery was investigated. The authors examined the hemodynamic changes produced and the response of stress hormones. Twenty adult patients with atrial septal defects undergoing surgical correction were studied in two groups of 10, receiving either 6 micrograms/kg of buprenorphine (B6) or 12 micrograms/kg of buprenorphine (B12) for the induction of anesthesia. Both groups received a subsequent dose of 6 micrograms/kg of buprenorphine with the commencement of extracorporeal circulation (ECC). With surgery, mean arterial pressure showed a transient increase in both groups and thereafter was stable. Heart rate in the B6 group was increased from the onset of surgery to the day after, while the B12 group showed no significant change. Filling pressures showed no change in either group. Plasma catecholamine concentrations in the B6 group, in contrast to the B12 group, increased significantly from midoperation to after completion of the operation (ECC 10 minutes, B6 group v B12 group: plasma norepinephrine 616 +/- 231 v 195 +/- 38 pg/mL, plasma epinephrine 1385 +/- 392 v 572 +/- 132 pg/mL, P less than 0.05). Plasma ADH levels in both groups rose with the commencement of surgery, reaching a peak at ECC 10 minutes (B6 group 88.1 +/- 8.4 v B12 group 124.4 +/- 27.2 pg/mL). However, in contrast to plasma catecholamines, the antidiuretic hormone (ADH) levels in the B12 group remained higher until the first postoperative day. Therefore, patients who received the larger dose of buprenorphine had better control of hemodynamics and catecholamines, but a greater elevation of plasma ADH levels.

The neuroanatomy, neurophysiology, and neurochemistry of pain, stress, and analgesia in newborns and children

Beginning with a brief description of mature anatomic pathways and neurotransmitters in the "pain system," this article details their development in the human fetus, neonate, and child. Special emphasis is given to the basic mechanisms and physiologic effects of opioid analgesia. The clinical implications of these data are described, particularly with regard to the maintenance of cardiovascular stability and hormonal-metabolic homeostasis in newborns and children undergoing surgery or other forms of stress.

[Baroreflex activity in carotid endarterectomy during general anesthesia]

The baroreceptor reflex was studied in eleven patients, aged 69 +/- 6 years, scheduled for carotid endarterectomy under general anaesthesia. Nine were hypertensive. The anaesthetic protocol was the same for all the patients: premedication with morphine and scopolamine, induction with 5 mg.kg-1 thiopentone, 6 micrograms.kg-1 fentanyl and 0.01 mg.kg-1 pancuronium bromide. All the patients were intubated and ventilated with a mixture of nitrous oxide and oxygen. Fentanyl, 100 micrograms, was routinely given at the time of incision. Baroreflex sensitivity was tested using Smyth's method, with a bolus of 75 micrograms trinitrin and plotting changes in heart rate against those in systolic blood pressure. Electrocardiogram, invasive arterial blood pressure and airway pressure were simultaneously recorded. PaCO2 and PaO2 were measured during arterial clamping. The tests were carried out before clamping, 2 min later and 10 to 20 min after the last injection of fentanyl. In the seven patients for whom clamping lasted more than 15 min, a further test was carried out after administration of 0.4 +/- 0.05 vol% halothane (Datex analyser) for 5 min. During anaesthesia, baroreflex sensitivity was low (1.8 +/- 0.3 ms.mmHg-1). After clamping, there was only a significant change in Pasys, with no changes in heart rate or blood gas values (129 +/- 8 mmHg before clamping; 167 +/- 12 mmHg after clamping; n = 8; p less than 0.01). After halothane administration, the sensitivity slope decreased, but not significantly. Moreover, halothane decreased the R-R intervals (1140 +/- 84 after clamping; 963 +/- 76 under halothane; n = 6; p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Prebypass hemodynamic stability of sufentanil-O2, fentanyl-O2, and morphine-O2 anesthesia during cardiac surgery: A comparison of cardiovascular profiles

Cardiovascular responses and the need for intervention with vasoactive agents were measured prospectively in a randomized study of 50 adult patients receiving sufentanil (n = 20), fentanyl (n = 20), or morphine (n = 10) anesthesia for cardiac surgery. Measurements were recorded and compared during induction and prebypass at intervals during which airway or surgically induced stress responses were likely to be greatest. Randomized, double-blinded doses of opioids were administered slowly and titrated according to clinical responses (hemodynamics) and the electroencephalogram. Mean doses were as follows: from induction until time of incision, sufentanil, 9.1 microg/kg; fentanyl, 58 microg/kg; and morphine, 2.5 mg/kg; and total dose for surgery; sufentanil, 18.9 microg/kg; fentanyl, 95.4 microg/kg; and morphine, 4.4 mg/kg. Equi-anesthetic depth in patients receiving sufentanil or fentanyl was confirmed by continuous electroencephalographic monitoring. Patients anesthetized with sufentanil and fentanyl showed marked cardiovascular stability and rarely responded to stimuli. Systolic arterial pressure, mean arterial pressure, heart rate, cardiac index, systemic vascular resistance index, pulmonary vascular resistance index, stroke volume index, and stroke work index values were similar in the two groups. Patients receiving morphine experienced large changes in several variables. Pharmacologic intervention was made when systolic arterial pressure deviated more than 30% from pre-event values and was uncontrolled by additional opioids. Interventions were necessary more often in patients receiving morphine (nine of ten) or fentanyl (12 of 20) than in patients receiving sufentanil (six of 20), P < 0.05. Results from this study suggest that morphine is a relatively unsatisfactory anesthetic, while sufentanil and fentanyl, at equi-anesthetic depths, provide stable and satisfactory hemodynamics.

Changes in ejection fraction during induction of anesthesia with two different i.v. techniques

Two intravenous induction techniques were compared with respect to changes in ejection fraction (EF) and central hemodynamics in 30 patients scheduled for coronary artery surgery. Left ventricular EF was measured with a collimated single crystal probe linked to a microcomputer, after injection of 200 MBq Tc 99 m HSA. Stroke volume index (SI) determined by thermodilution and EF were used to calculate left ventricular volume in end-systole and end-diastole. In 20 patients (Group I), anesthesia was induced with diazepam (94 micrograms x kg-1), thiopentone (3 mg x kg-1) and fentanyl (3 micrograms x kg-1). In 10 patients (Group II), fentanyl (30 micrograms x kg-1) was used for induction. In Group I, EF decreased from 0.43 to 0.26 at intubation, while systemic vascular resistance index (SVRI) showed an increase. Left ventricular volume decreased during induction of anesthesia except during intubation. In Group II, EF and left ventricular volume remained unchanged during the study period. SVRI showed no increase at intubation. No change in contractility was indicated from the relation between the end-systolic pressure and volume, in any of the groups.