Haemodynamic Stability during Anaesthesia Induction and Sternotomy in Patients with Ischaemic Heart Disease

A comparison of haemodynamic stability with respect to arterial pressure, heart rate and cardiac output between six commonly used anaesthetic techniques: fentanyl (FE), halothane (HAL), morphine (MO), fentanyl/droperidol (NLA), and thiopentone (two dose levels: PE 3 and PE 6), all supplemented with nitrous oxide, was performed during induction of anaesthesia and sternotomy in 47 patients with good left ventricular function and maintained beta-blockers undergoing coronary bypass surgery. Interventions were kept to a minimum in order to characterize each anaesthesia group. Statistically, the material fell into two parts. The MO, PE 3 and PE 6 groups showed good stability under steady-state anaesthesia, but variable and often extensive hyperdynamic responses were seen to endotracheal intubation and surgical stimulation. The FE, HAL and NLA groups were characterized by a good stability during the induction-intubation phase but were unstable when combined with nitrous oxide in the absence of noxious stimuli.     

High-dose fentanyl for rapid induction of anaesthesia in patients with coronary artery disease

Nine premedicated patients, chronically maintained on beta-adrenergic blocking agents and demonstrating good ventricular function without significant valvular or left main coronary artery disease, were investigated to determine their haemodynamic responses to rapid induction of anaesthesia and tracheal intubation during elective coronary artery bypass surgery. Fentanyl 50 micrograms X kg-1 and pancuronium 0.15 mg X kg-1 were administered intravenously over 20 seconds followed by tracheal intubation 90 seconds thereafter. The rapid sequence of anaesthetic induction and tracheal intubation was well tolerated by all patients. Though statistically significant changes were detected in heart rate, pulmonary capillary wedge pressure and systemic vascular resistance, these changes were small and not considered clinically significant and no signs of ischaemia were detected on the ECG. The present study demonstrates that high-dose fentanyl is capable of inducing anaesthesia rapidly and protecting against the haemodynamic changes associated with tracheal intubation.     

Etomidate modifies hemodynamic response to fentanyl in patients with impaired left ventricular function]

The haemodynamic effects and the side-effects of anaesthesia using high doses of fentanyl were compared in two groups of 12 patients each. All the patients had poor left ventricular function and were scheduled for elective coronary artery bypass graft surgery or valvular replacement. Patients were randomly assigned to either group. In group EF, patients were given 5 micrograms.kg-1 of fentanyl, followed by 0.3 mg.kg-1 of etomidate. Once they had lost consciousness, they were given 15 mg of pancuronium and 25 micrograms.kg-1 of fentanyl over a 5 min period. Patients in group F received the full 30 micrograms.kg-1 dose of fentanyl over a 5 min period, followed by 15 mg of pancuronium. The patients were intubated 2 min after the end of the fentanyl infusion. They were mechanically ventilated with 100% oxygen. Anaesthesia was maintained with a continuous infusion of fentanyl (total dose 100 micrograms.kg-1). The usual haemodynamic parameters were monitored and calculated, as well as pain during injection of the drugs, myoclonia, chest wall rigidity and the time to loss of consciousness. The two groups were comparable with respect to age, weight, height and surgery. One third of the patients in group EF complained of pain during etomidate injection. The time required to loose consciousness was shorter in group EF (55 +/- 16 sec) than in group F (177 +/- 56 sec) (p < 0.001). The cardiac index decrease in group EF (2.0 +/- 0.4 l.min-1.m-2 vs. 1.9 +/- 0.4 l.min-1.m-2) (p < 0.05), respectively between the time just before tracheal intubation (T1), and 10 min after tracheal intubation (T3).(ABSTRACT TRUNCATED AT 250 WORDS)     

Haemodynamic stability with midazolamsufentanil analgesia in cardiac surgical patients

Since the administration of both diazepam and midazolam are claimed to cause adverse haemodynamic effects following fentanyl or sufentanil intravenous injection, we evaluated the effectiveness and safety of the reverse sequence, (midazolam-sufentanil) on haemodynamic variables, adequacy of analgesia, amnesia and recovery in 15 adult patients undergoing coronary artery surgery (with a mean +/- SEM ejection fraction of 0.41 +/- 0.03). After routine premedication, midazolam 0.14 +/- 0.01 mg.kg-1 IV was given over one min followed 5 min later by sufentanil in incremental IV doses of 1.5 micrograms.kg-1 to a total pre-intubation dose of 4.0-5.0 micrograms.kg-1 injected in 10 min. One minute after the initial dose of sufentanil, pancuronium 0.1 mg.kg-1 IV was given in 30 seconds. The incremental doses of sufentanil were based on a greater than 15 per cent increase in rate-pressure product. The mean dose of sufentanil before cardiopulmonary bypass was 9.6 +/- 2.1 micrograms.kg-1 and 13.9 +/- 1.3 micrograms.kg-1 for the entire procedure. A significant decrease in systolic and diastolic blood pressures occurred after midazolam administration which was sustained until sternotomy. A significant reduction in systemic vascular resistance occurred following midazolam. Sufentanil reduced the left ventricular stroke-work index. Tracheal intubation, skin incision and sternotomy elicited no adverse haemodynamic responses. Adequate analgesia, complete amnesia and early recovery of wakefulness were observed.     

Thiopentone reduces the haemodynamic response to induction of high–dose fentanyl–pancuronium anaesthesia in coronary artery surgical patients

Thirty-three coronary artery bypass graft patients anaesthetized with high-dose fentanyl (50 micrograms/kg)-pancuronium-oxygen were divided into one control group receiving additional saline and two groups receiving additional 1 mg/kg or 2.5 mg/kg of thiopentone before laryngoscopy and intubation. During laryngoscopy and intubation, systemic arterial pressures, heart rate and rate-pressure-product remained at considerably elevated levels caused by pancuronium in the control group. Both doses of thiopentone reduced these haemodynamic values close to their initial levels. Cardiac index and left ventricular stroke work index were significantly decreased, especially by the higher thiopentone dose, as compared with the control group. However, there were no statistical differences between the haemodynamic changes produced by the two doses of thiopentone. Sedative or hypnotic supplementation of high-dose fentanyl anaesthesia seems to be necessary if pancuronium is used as a muscle relaxant. A small increment of thiopentone, 1 mg/kg, was enough to return haemodynamic parameters almost to their initial levels, whereas the effect of 2.5 mg/kg of thiopentone was unnecessarily strong.     

Catecholamine response to laryngoscopy and intubation

The haemodynamic response and changes in plasma catecholamine concentrations associated with laryngoscopy and tracheal intubation were compared during anaesthesia employing three strictly standardised techniques with commonly used drug combinations. Thirty-six patients were investigated consecutively resulting in 12 patients in each of three study groups. Anaesthesia was induced with thiopentone 5 mg.kg-1 (group 1), fentanyl 6 micrograms.kg-1 with thiopentone 5 mg.kg-1 (group 2), or midazolam 0.2 mg.kg-1 with fentanyl 6 micrograms.kg-1 (group 3). Undesirable changes in haemodynamic effects and an elevation of plasma catecholamine concentrations during laryngoscopy and intubation occurred in group 1. Heart rate and mean arterial pressure increased significantly (34% and 23% respectively). Noradrenaline concentration increased by a maximum of 147%. The addition of fentanyl (groups 2 and 3) attenuated the adverse haemodynamic response and elevation of plasma catecholamine concentrations; heart rate and mean arterial pressure did not differ from pre-intubation values and plasma catecholamine concentrations decreased steadily. Substitution of thiopentone by midazolam in combination with fentanyl abolished the adverse haemodynamic response and modified the increase in plasma catecholamine concentrations. 'High-dose' opioid anaesthesia is not necessary to produce optimal conditions during laryngoscopy and intubation.     

Plasma concentrations of fentanyl in infants,children and adults

To evaluate whether there are age-related differences in the plasma concentration-vs-time course of fentanyl, the authors administered fentanyl to seven infants (3-10 months), seven children (1-9 years) and seven adults (18-41 years). Anaesthesia was induced with thiopentone, nitrous oxide, and pancuronium; following tracheal intubation, fentanyl (approximately 30 micrograms X kg-1 for infants and children, 20 micrograms X kg-1 for adults) was administered as a 2-min IV infusion. Anaesthesia was maintained with nitrous oxide, pancuronium, and morphine sulphate as clinically indicated. Plasma samples were obtained for 4 h and fentanyl concentrations determined by radioimmunoassay. Plasma concentrations per microgram X kg-1 fentanyl administered were lowest in infants 4-10 and 60-240 min after the start of the 2-min infusion; values for children were lower than those for adults 4, 180 and 210 min after the start of the 2-min infusion. These findings are consistent with the authors' clinical observation that infants tolerate larger doses of fentanyl than do adults.     

Randomized comparison of outcome after propofol-nitrous oxide or enflurane-nitrous oxide anaesthesia in operations of long duration

A randomized, prospective, comparative study was performed to evaluate induction characteristics, haemodynamic changes and recovery in 60 ASA I-II patients undergoing mainly gynaecological laparotomies with either propofol or thiopentone-enflurane anaesthesia. The propofol group (n = 30) received 2 mg.kg-1 propofol for induction of anaesthesia followed by propofol infusion. The thiopentone-enflurane group (n = 30) received thiopentone 4 mg.kg-1 for induction followed by enflurane (0.5-2 per cent). All patients received nitrous oxide (66 per cent] in oxygen begun one minute after tracheal intubation, and fentanyl (1.5 micrograms.kg-1) four minutes prior to induction. Other drugs administered during or after anaesthesia were similar among the groups. Haemodynamic measurements were similar between propofol and enflurane groups except after tracheal intubation when the mean arterial pressure was lower in the propofol group (P less than 0.05). The propofol group had significantly less (P less than 0.01) emesis in the recovery room than the enflurane group. The propofol group experienced significantly less (P less than 0.05) dizziness, depression/sadness and hunger than the enflurane group in the postoperative period as assessed with a visual analogue questionnaire. We conclude that propofol provided better outcome than enflurane in terms of these nonvital but annoying outcome measures after relatively long intra-abdominal operations.     

Anaesthesia for myocardial revascularisation

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.     

Haemodynamic responses to tracheal intubation following etomidate and fentanyl for anaesthetic induction

The haemodynamic response to anaesthetic induction and tracheal intubation was studied in 29 patients undergoing elective myocardial revascularization surgery. All patients included in the study were anaesthetized with etomidate, 0.3 mg.kg-1. The patients were randomized to three groups: Group I received fentanyl, 2.5 micrograms.kg-1; Group II received fentanyl, 5 micrograms.kg-1; and Group III received fentanyl, 10 micrograms.kg-1. Haemodynamic variables were measured at baseline (awake), after anaesthetic induction, and at one, three, five, and ten minutes after tracheal intubation. The number of patients with haemodynamic responses to intubation (> 20% increase in heart rate or mean arterial pressure) was greater (P < 0.05) in Group I than in Groups II and III. Statistically significant, but clinically minor, decreases in mean arterial pressure and cardiac output occurred in all groups at the last three study times. The frequency of involuntary muscle movements was 14%, and all of these events occurred in patients in Group I. In conclusion, the authors recommend using fentanyl, 5-10 micrograms.kg-1 to blunt the haemodynamic response to tracheal intubation following anaesthetic induction with etomidate, 0.3 mg.kg-1.     

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.     

Comparison of nicardipine, diltiazem and verapamil for controlling the cardiovascular responses to tracheal intubation

We have compared the efficacy of three calcium channel blockers, nicardipine, diltiazem and verapamil, in attenuating the cardiovascular responses to laryngoscopy and intubation in 60 normotensive patients (ASA I) undergoing rapid sequence induction of anaesthesia with thiopentone and fentanyl. We also examined whether or not these blockers inhibited catecholamine release induced by intubation. The patients were allocated to one of four groups (n = 15 for each): saline (control), nicardipine 30 micrograms kg-1, diltiazem 0.2 mg kg-1 or verapamil 0.1 mg kg-1. Verapamil and the three other drugs were administered 45 s and 60 s before the start of direct laryngoscopy, respectively, in a double-dummy design. Anaesthesia was induced with thiopentone 4 mg kg-1 i.v. and fentanyl 2 micrograms kg-1 i.v. Tracheal intubation was facilitated with vecuronium 0.2 mg kg-1. During anaesthesia, ventilation was assisted or controlled with 1% isoflurane and 50% nitrous oxide in oxygen. Laryngoscopy lasting 30 s was attempted 2 min after administration of thiopentone and vecuronium. Patients receiving saline exhibited significant increases in systolic and diastolic arterial pressures (AP), heart rate (HR) and plasma concentrations of catecholamines associated with tracheal intubation. The increase in AP was attenuated in patients treated with any calcium channel blocker. The greatest effect was elicited by verapamil, which attenuated the increase in HR, although nicardipine seemed to enhance tachycardia. All three drugs failed to suppress the increase in plasma catecholamine concentrations in response to tracheal intubation. These findings suggest that bolus injection of verapamil 0.1 mg kg-1 was a more effective method of controlling hypertension and tachycardia associated with intubation than diltiazem 0.2 mg kg-1 or nicardipine 30 micrograms kg-1, and that these prophylactic effects were not caused by inhibition of the catecholamine response.      

Effect of fentanyl on the circulatory responses to orotracheal fibreoptic intubation

The effectiveness of fentanyl in attenuating the pressor and heart rate response to orotracheal fibreoptic intubation under general anaesthesia was assessed in 60 healthy patients undergoing elective surgery. Patients were randomly assigned to receive either fibreoptic intubation with or without fentanyl 6 micrograms.kg-1 or traditional Macintosh intubation with fentanyl 6 micrograms.kg-1. A standardised general anaesthetic was administered which included temazepam premedication, thiopentone, atracurium, oxygen, nitrous oxide and isoflurane. The pressor response to fibreoptic intubation was suppressed in those patients who received fentanyl and was similar to that seen in the Macintosh-fentanyl group of patients. The heart rate response to fibreoptic intubation was also significantly reduced in the patients who received fentanyl, but, in contrast, was still significantly greater than that in the Macintosh-fentanyl group. Fentanyl 6 micrograms.kg-1 appears to have a useful place in attenuating the cardiovascular effects of fibreoptic intubation under general anaesthesia.     

A comparison of fentanyl,esmolol, and their combination for blunting the haemodynamic responses during rapid-sequence induction

The purpose of this randomized, double-blind study was to compare the ability of a combination of fentanyl and esmolol to blunt the haemodynamic effects of intubation with that of either agent alone. Patients received fentanyl or saline four minutes before, and esmolol or saline two minutes before rapid-sequence induction of anaesthesia. The F2 group (n = 24) received fentanyl 2 micrograms.kg-1, the E2 group (n = 24) received esmolol 2 mg.kg-1, the F2/E2 group (n = 25) received a combination of fentanyl 2 micrograms.kg-1 and esmolol 2 mg.kg-1, and the F5 group (n = 26) received fentanyl 5 micrograms.kg-1. Following tracheal intubation, the maximum percent change from baseline heart rate was less in the F2/E2 and F5 groups (12% and 16% respectively) than in the E2 group (34%)(P < 0.05). The maximum percent changes from baseline systolic blood pressure in the F2/E2 and F5 groups (15% and 6% respectively) were less than in the F2 and E2 groups (24% and 33% respectively) (P < 0.05). The combination of a low dose of fentanyl and esmolol provides an alternative to a higher dose of fentanyl for blunting the haemodynamic responses to laryngoscopy and tracheal intubation during rapid-sequence induction in healthy patients.     

Hemodynamic effects of fentanyl and sufentanil combined with flunitrazepam in coronary artery surgery

Because sufentanil has been reported as being able to prevent or treat peroperative hypertensive crises during aorto-coronary artery graft surgery, a study was carried out to compare the haemodynamic effects of sufentanil with those of fentanyl. 20 patients who were to undergo aortocoronary bypass grafting (CABG) were randomly allocated to two equal groups, sufentanil (Sf) and fentanyl (F) groups. A 1 to 5 dose ratio was used so as to have equipotent doses of sufentanil and fentanyl. Induction doses were 10 micrograms.kg-1 sufentanil and 50 micrograms.kg-1 fentanyl. Up to 20 micrograms.kg-1 sufentanil and 100 micrograms.kg-1 fentanyl were then used between intubation and the setting-up of cardiopulmonary bypass (CPB). A bolus of 10 micrograms.kg-1 flunitrazepam was given if necessary, so as to lower the mean arterial pressure (Pa) to below 100 mmHg after intubation, and under 80 mmHg during CPB. Heart rate, Pa, mean pulmonary arterial pressure, pulmonary wedge pressure (Ppw), central venous pressure and cardiac output were measured before anaesthesia, 2 min after intubation, before incision, 2 min after sternotomy, 10 min after the end of CPB, after chest closure, 30 min and 2h after arrival of the patient in the intensive care unit. The only difference found between the two groups was a more rapid drop in left ventricular preload after induction with sufentanil; 2 min after intubation, there was a 26% fall in Ppw with sufentanil (p less than 0.01) and 8% with fentanyl. Before skin incision, this drop was of 32% (p less than 0.01) and 24% (p less than 0.01) respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Fentanyl-Droperidol-Nitrous Oxide Anaesthesia in Patients with Ischaemic Heart Disease and Various Degrees of Left Ventricular Functional Impairment

Haemodynamic stability and left ventricular function (LVF) during induction of anaesthesia and sternotomy were compared in three groups of patients with ischaemic heart disease, angiographically classified as having good, poor and depressed LVF. Anaesthesia was given with fentanyl-droperidol and nitrous oxide. The group with good LVF showed large variations in arterial pressure and heart rate between stimulated and unstimulated states with a reasonable preservation of LVF, expressed as stroke volume, through the whole observation period. The group with poor LVF showed monotonously falling arterial pressure, and no heart rate response to tracheal intubation. These patients maintained remarkably stable stroke volumes in connection with low afterloads. After nitrous oxide, additional volume loading was required because of profound hypotension. The majority of the patients in the intermediate group, labelled "depressed LVF", reacted to intubation and sternotomy with signs of left ventricular failure in connection with tachycardia and increased afterloads. The individual variations between patients with different degrees of left ventricular impairment were considerable, and these haemodynamic patterns need to be confirmed with a larger material.     

Haemodynamic and biochemical variables after induction of anaesthesia with fentanyl and nitrous oxide in patients undergoing coronary artery by-pass surgery

The effects on the haemodynamic and biochemical parameters of three different anaesthetic induction regimes, namely fentanyl (4.1 μg · kg^-1 or 15 μg · kg^-1) plus 60 percent nitrous oxide with oxygen and fentanyl 15 μg · kg^-1 plus 60 per cent nitrogen with oxygen, were studied in patients undergoing coronary artery surgery. Fentanyl 15 μg · kg^-1 with nitrous oxide and oxygen produced simultaneous reductions in oxygen uptake, cardiac index and left ventricular stroke work with an unaltered oxygen extraction. Diastolic blood pressure (an index of coronary artery perfusion) was only slightly reduced, and there were no changes in arterial lactate, glucose and free fatty acids. The lower dose of fentanyl (4.1 μg · kg^-1) with nitrous oxide produced no haemodynamic changes but decreased the oxygen uptake and extraction. The patients receiving fentanyl 15 μg · kg^-1 with nitrogen and oxygen showed increases in heart rate, blood pressure, cardiac index and left ventricular stroke work, together with a significant fall in oxygen extraction. Moreover, in the patients who received fentanyl 4.1 μg · kg^-1 with nitrous oxide and oxygen and fentanyl 15 μg · kg^-1 with nitrogen and oxygen there were significant increases in blood lactate, glucose and free fatty acids, indicating increased sympathetic activity. We conclude that fentanyl 15 μg · kg^-1, together with 60 per cent nitrous oxide with oxygen provides a satisfactory haemodynamic and biochemical state during induction of anaesthesia in patients with myocardial function prejudiced by coronary artery insufficiency.     

Bolus administration of esmolol for controlling the haemodynamic response to tracheal intubation: the canadian multicentre trial

A multicentre trial was designed to determine the dose-response and side-effects of esmolol when administered as a single iv bolus prior to induction of anaesthesia for controlling the haemodynamic response to tracheal intubation. Five hundred and forty-eight patients from 12 university-affiliated centres across Canada were randomized prospectively to receive either placebo (PLAC) or esmolol (E) in a dose of 100 mg (E100) or 200 mg (E200). Study medication was given immediately before induction of anaesthesia with thiopentone 3-5 mg.kg-1 and succinylcholine 1.5 mg.kg-1. Low-dose narcotic (fentanyl 2-3 micrograms.kg-1 or sufentanil 0.3 micrograms.kg-1) or moderate dose narcotic (fentanyl 4-7 micrograms.kg-1) was also given at five of the participating centres, whereas patients in the remaining seven centres received no narcotic. Patients who received PLAC and no narcotic had greater HR and SBP values after tracheal intubation than patients who received either E100 or E200 (P less than 0.005). The proportion of patients whose maximum HR exceeded 110 min-1 was also greater in the PLAC group (22/180) than in either the E100 (10/187) or E200 (9/181) groups (P less than 0.05), but was not different when comparing E100 with E200. Esmolol was less effective in controlling blood pressure, but, in combination with low-dose narcotic, esmolol suppressed the SBP response to tracheal intubation. In the presence of moderate-dose narcotic, however, a decrease in SBP occurred in all three groups following induction of anaesthesia (P less than 0.003), with the largest decrease (17 +/- 4%) occurring in patients who had received E200. The overall incidence of hypotension (SBP less than 90 mmHg) was greater in the E200 group (33%) than either the E100 (25%) or PLAC (16%) groups (P less than 0.05). Other side-effects, such as bradycardia, bronchospasm or pain on injection, occurred no more frequently in either esmolol group than with placebo. It is concluded that a 100 mg bolus of esmolol is safe and effective for controlling the haemodynamic response to tracheal intubation. This dose of esmolol combined with a low dose of narcotic (fentanyl 2-3 micrograms.kg-1 or equivalent) results in effective control of both heart rate and blood pressure, while avoiding important side-effects.     

Comparison of Alfentanil and Fentanyl as Supplements to Induction of Anaesthesia with Thiopentone

In 120 premedicated patients undergoing general surgery, anaesthesia was induced with thiopentone 3 mg kg-1, preceded by alfentanil 4.5, 9.0 or 13.5 micrograms kg-1 or fentanyl 1.5 micrograms kg-1. The largest alfentanil dose attenuated the arterial blood pressure response to laryngoscopy and intubation better than the smaller doses of alfentanil. Changes in frontal muscle electromyogram or plasma cortisol and prolactin levels were not dependent on the adjuvant used. After thiopentone, 30, 7 and 17% of the patients given alfentanil 9.0 and 13.5 micrograms kg-1 and fentanyl 1.5 micrograms kg-1, respectively, reacted to pinching of the lower abdomen. Patients given alfentanil 4.5 micrograms kg-1 did not tolerate the endotracheal tube after recovery from suxamethonium block and their heart rate was increased 12 min after alfentanil administration. We conclude that the antinociceptive effect of alfentanil is distinctly shorter than that of fentanyl. The analgesic potency of alfentanil is between one sixth and one ninth of that of fentanyl.     

Haemodynamic response to induction of anaesthesia with ketamine/midazolam

The haemodynamic responses following induction of anaesthesia with ketamine and midazolam have not been determined previously. Twenty adult patients for elective myocardial revascularization were randomized to two regimens for induction of anaesthesia. Patients in Group I received ketamine, 2 mg.kg-1, and midazolam, 0.2 mg.kg-1 and those in Group II received ketamine, 2 mg.kg-1, and midazolam, 0.4 mg.kg-1. Measurements were recorded at baseline, 1 min post-induction, and at one, three, five and ten minutes after tracheal intubation. Tachycardia and hypertension (greater than 20% increases from awake baseline values) were treated with esmolol, 250 micrograms.kg-1. There were 11 patients in Group I and nine patients in Group II. There were no significant intergroup differences in demographic or haemodynamic variables. Both groups had decreases (P less than 0.05), in stroke volume, pulmonary capillary wedge pressure, and right ventricular end-diastolic volume at multiple study intervals following anaesthetic induction. None of these changes required clinical intervention. Five patients (all in Group II) had hypertensive responses to tracheal intubation. Preoperative hypertension (mean arterial pressure greater than or equal to 100 mmHg) was a predictor (P less than 0.05) of a hypertensive response to intubation, independent of the midazolam dose. Intravenous ketamine and midazolam was associated with a high incidence (25%) of haemodynamic responses to tracheal intubation. The higher dose of midazolam did not provide any haemodynamic advantage.