Potent antioxidative potential of propofol during cardiopulmonary bypass in the adult

The potent antioxidative potential of propofol during cardiopulmonary bypass (CPB) in adults was investigated. The selected 30 patients receiving open heart surgery under CPB were randomly divided into group A and group B. The patients in the group A and group B were given propofol (0.1 mg.kg-1.min-1) and fentanyl (5 micrograms.kg-1.min-1) respectively to maintain anesthesia after aorta was cross-clamped. Blood samples were drawn pre-anesthesia, pre-CPB, at 30 min of CPB, at the end of CPB, at 1 h after CPB, at the end of operation, at 12 and 24 h postoperatively. RBC suspension was prepared and erythrocyte glucose-6-phosphate dehydrogenase (G-6-PD) and phosphofructokinase (PFK) activities, total erythrocyte reduced glutathione (GSH) and oxidized GSH (GSSG) were assayed and GSH/GSSG ratio was calculated. In the group A, G-6-PD and PFK activities and GSH/GSSG ratio were almost uneventfully during CPB and postoperatively. In the group B, G-6-PD activity was increased and PFK activity and GSH/GSSG ratio decreased significantly from 30 min of CPB until 12 h postoperatively. It was demonstrated that propofol could obviously attenuate free radical activity during CPB, while fentanyl has no effect on free radical reduction. Propofol could be beneficial as an anesthetic in patients presenting pathologies associated with free radical reactions during CPB.

[Pharyngolaryngoscopic findings in patients with obstructive sleep apnea syndrome and primary snoring]

BACKGROUND AND OBJECTIVE

The localization of an upper airway collapse in snorers and patients suffering from obstructive sleep apnea was a subject frequently discussed in the last few years. Pharyngolaryngoscopy during sleep or drug-induced sleep allows evaluation of upper airway conditions.

PATIENTS/METHODS

A total of 324 patients suffering from snoring or obstructive sleep apnea underwent flexible pharyngolaryngoscopy while awake and under propofol-induced sedation in the course of routine diagnostic procedures in the sleeping lab. In this study, the results of pharyngolaryngoscopy are compared to results of the Müller maneuver and polysomnographic recordings. The therapeutic consequences of this additional investigation are discussed.

RESULTS

In 95% of cases snoring was observed during drug-induced sleep. A significant discrepancy was seen between results of the endoscopy while being awake (Müller maneuver) and during drug-induced sleep. The degree of collapse differed significantly in the area of the base of the tongue. Severe collapse was seen much more often with pharyngoscopy during drug-induced sleep compared to the results during the Müller maneuver.

CONCLUSIONS

The collapsibility in the area of the base of the tongue correlated with higher results in the RDI (respiratory disturbance index) registered with standard polysomnography. Snoring and upper airway collapse were easily surveyed, and the pharyngolaryngoscopy during propofol-induced sleep proved to be a simple, safe, readily controllable and effective supplementary diagnostic device for the diagnosis and treatment of obstructive sleep apnea and snoring.

Auditory steady-state response and bispectral index for assessing level of consciousness during propofol sedation and hypnosis

We assessed the effect of propofol on the auditory steady-state response (ASSR), bispectral (BIS) index, and level of consciousness in two experiments. In Experiment 1, propofol was infused in 11 subjects to obtain effect-site concentrations of 1, 2, 3, and 4 microg/mL. The ASSR and BIS index were recorded during baseline and at each concentration. The ASSR was evoked by monaural stimuli. Propofol caused a concentration-dependent decrease of the ASSR and BIS index values (r(2) = 0.76 and 0.93, respectively; P<0.0001). The prediction probability for loss of consciousness was 0.89, 0.96, and 0.94 for ASSR, BIS, and arterial blood concentration of propofol, respectively. In Experiment 2, we compared the effects of binaural versus monaural stimulus delivery on the ASSR in six subjects during awake baseline and propofol-induced unconsciousness. During baseline, the ASSR amplitude with binaural stimulation (0.47+/-0.13 microV, mean +/- SD) was significantly (P<0.002) larger than with monaural stimulation (0.35+/-0.11 microV). During unconsciousness, the amplitude was 0.09+/-0.09 microV with monaural and 0.06+/-0.04 microV with binaural stimulation (NS). The prediction probability for loss of consciousness was 0.97 (0.04 SE) for monaural and 1.00 (0.00 SE) for binaural delivery. We conclude that the ASSR and BIS index are attenuated in a concentration-dependent manner by propofol and provide a useful measure of its sedative and hypnotic effect. BIS was easier to use and slightly more sensitive. The ASSR should be recorded with binaural stimulation. The ASSR and BIS index are both useful for assessing the level of consciousness during sedation and hypnosis with propofol. However, the BIS index was simpler to use and provided a more sensitive measure of sedation.

IMPLICATIONS

We have compared two methods for predicting whether the amount of propofol given to a human subject is sufficient to cause unconsciousness, defined as failure to respond to a simple verbal command. The two methods studied are the auditory steady-state response, which measures the electrical response of the brain to sound, and the bispectral index, which is a number derived from the electroencephalogram. The results showed that both methods are very good predictors of the level of consciousness; however, bispectral was easier to use.

[Anesthetic management of MIDCAB in a patient with Wolff-Parkinson-White syndrome]

We experienced the anesthetic management of a minimally invasive direct coronary artery bypass (MIDCAB) in a patient with Wolff-Parkinson-White (WPW) syndrome. A 55-year-old male had chest pain on effort and was diagnosed as having stenosis of the left coronary artery (#6). He was scheduled to undergo MIDCAB. Anesthesia was induced with midazolam 5 mg, fentanyl 300 micrograms, and vecuronium 10 mg and maintained with air-oxygen, propofol, and fentanyl (27 micrograms.kg-1). Diltiazem was continuously infused at a rate of 0.5-1.5 micrograms.kg-1.min-1 throughout the surgery. The hemodynamic parameters were maintained stable and paroxysmal supraventricular tachycardia was not observed during the procedure. We conclude that the administration of propofol and a medium dose of fentanyl is useful for the anesthetic management of MIDCAB in patients with WPW syndrome and that intraoperative administration of diltiazem might be needed to avoid paroxysmal supraventricular tachycardia.

Recovery from neuromuscular blockade after either bolus and prolonged infusions of cisatracurium or rocuronium using either isoflurane or propofol-based anesthetics

We examined the recovery characteristics of cisatracurium or rocuronium after bolus or prolonged infusion under either isoflurane or propofol anesthesia. Sixty patients undergoing neurosurgical procedures of at least 5 h were randomized to receive either isoflurane with fentanyl (Groups 1 and 2) or propofol and fentanyl (Groups 3 and 4) as their anesthetic. Groups 1 and 3 received cisatracurium 0.2 mg/kg IV bolus, spontaneously recovered, after which time an infusion was begun. Groups 2 and 4 received rocuronium 0.6 mg/kg IV, spontaneously recovered, and an infusion was begun. Before the end of surgery, the infusion was stopped and recovery of first twitch (T(1)), recovery index, clinical duration, and train-of-four (TOF) recovery was recorded and compared among groups by using appropriate statistical methods. Clinical duration was shorter for rocuronium compared with cisatracurium using either anesthetic. Cisatracurium T(1) 75% recovery after the infusion was shorter with propofol compared with isoflurane. Cisatracurium TOF 75% recovery was similar after either bolus or infusion, but rocuronium TOF 75% recovery after the infusion was delayed. Infusion rates decreased for cisatracurium but remained relatively constant for rocuronium regardless of the anesthetic used. Isoflurane enhances the effect of both muscle relaxants but prolonged cisatracurium recovery more than rocuronium. Of the two muscle relaxants studied, rocuronium's recovery was most affected by length of the infusion. Cisatracurium may be a more desired muscle relaxant for prolonged procedures because recovery was least affected by prolonged infusion.

IMPLICATIONS

This study describes the effect of different anesthetic techniques on the recovery of two different muscle relaxants, cisatracurium and rocuronium, when administered as either a single bolus or prolonged infusion during neurosurgery. This study demonstrates the feasibility of using these relaxants for these prolonged procedures.

Total intravenous anaesthesia without muscle relaxants in a child with diagnosed Duchenne muscular dystrophy

The case of a 3 year old child, affected by Duchenne muscular dystrophy, who underwent adenoidectomy and bilateral myringotomy, is reported. Total intravenous anaesthesia (propofol 1% infusion (160 micrograms kg-1min-1) and remifentanil (0.55 microgram kg-1min-1) without any muscle relaxants was used. The postoperative period was uneventful.

Dynamic cardiocirculatory control during propofol anesthesia in mechanically ventilated patients

We evaluated dynamic cardiovascular control by spectral analytical methods in 20 young adults anesthetized with propofol (2.5 mg/kg, followed by continuous infusion of 0.1 mg/kg/min) and in an awake control group during cyclic stimulation of the carotid baroreceptors via sinusoidal neck suction at 0.2 Hz (baroreflex response mediated mainly by vagal activity) and at 0.1 Hz (baroreflex response mediated by vagal and sympathetic activity). During anesthesia and mechanical ventilation at 0.25 Hz, major underdampened hemodynamic oscillations occurred at 0.055 +/- 0.012 Hz. The response of RR intervals to baroreceptor stimulation at 0.2 Hz was markedly decreased during anesthesia (median of transfer function magnitude between neck suction and RR intervals 3% of the awake control). Blood pressure response to baroreceptor stimulation at 0.1 Hz was significantly decreased during anesthesia to 26% (systolic blood pressure), and 44% (diastolic blood pressure) of the awake control. There was a significant delay in baroreflex effector responses during anesthesia. Our results demonstrate a markedly depressed vagally mediated heart rate response and an impaired blood pressure response to cyclic baroreceptor stimulation during propofol anesthesia in mechanically ventilated patients. The disturbed baroreflex control is accompanied by an irregular dynamic behavior of cardiovascular regulation, indicating a decreased stability of the control system.

IMPLICATIONS

An irregular dynamic behavior of the cardiovascular control system, associated with an impaired baroreflex control of heart rate and blood pressure, can be observed during propofol anesthesia in mechanically ventilated subjects.

Midazolam and 2% propofol in long-term sedation of traumatized critically ill patients: efficacy and safety comparison

OBJECTIVE

We proposed to compare the efficacy and safety of midazolam and propofol in its new preparation (2% propofol) when used for prolonged, deep sedation in traumatized, critically ill patients. We also retrospectively compared 2% propofol with its original preparation, 1% propofol, used in a previous study in a similar and contemporary set of patients.

DESIGN

A prospective, randomized, unblinded trial (midazolam and 2% propofol) and a retrospective, contemporary trial (2% propofol and 1% propofol).

SETTINGS

A trauma intensive care unit in a tertiary university hospital.

PATIENTS

A total of 63 consecutive trauma patients, admitted within a period of 5 months and requiring mechanical ventilatory support for >48 hrs, 43 of whom (73%) suffered severe head trauma. We also retrospectively compared the 2% propofol group with a series of patients in whom 1% propofol was used.

INTERVENTIONS

For the prospective trial, we randomized two groups--a midazolam group with continuous administration of midazolam at dosages 0.1-0.35 mg/kg/hr, and a 2% propofol group with continuous infusion at dosages 1.5-6 mg/kg/hr. Equal dosages of analgesics were administered. Similar management protocols were applied in the 1% propofol group, used in the retrospective analysis with 2% propofol.

MEASUREMENTS AND MAIN RESULTS

Epidemiologic and efficacy variables were recorded. Hemodynamic and biochemical variables were also monitored on a regular basis. Neuromonitoring was also performed on those patients with head trauma. Sedation adequacy was similar and patient behavior after drug discontinuation was not different in either prospective group (midazolam and 2% propofol). Hemodynamic or neuromonitoring variables were also similar for both groups. Triglyceride levels were significantly higher in the 2% propofol group compared with the midazolam group. A higher number of therapeutic failures because of sedative inefficacy was seen in the 2% propofol group compared with the midazolam group, especially during the first sedation days. When comparing 2% propofol and 1% propofol, a significantly higher number of therapeutic failures because of hypertriglyceridemia were found in the 1% propofol group, as opposed to a major number of therapeutic failures because of inefficacy, found in the 2% propofol group.

CONCLUSIONS

Propofol's new preparation is safe when used in severely traumatized patients. Its more concentrated formula improves the lipid overload problem seen with the prolonged use of the previous preparation. Nevertheless, a major number of therapeutic failures were detected with 2% propofol because of the need for dosage increase. This fact could be caused by a different disposition and tissue distribution pattern of both propofol preparations. New studies will be needed to confirm these results.

[Endocrine stress parameters during TIVA with remifentanil or sufentanil]

OBJECTIVE

Increases of heart rate and blood pressure during anaesthesia are interpreted as a response to surgical stimulation, although the endocrine response and the cardiovascular reaction can differ markedly. We compared remifentanil and sufentanil as part of a TIVA for retinal surgery with respect to the endocrine stress responses and haemodynamic reactions.

METHODS

After ethics committee approval and informed consent, 22 patients (ASA I-III) scheduled for retinal surgery were included in this patient-blind, randomized, prospective parallel-group study and allocated to one of the two groups receiving TIVA with propofol (4 mg/kg/h) and remifentanil (R-group) 0.25 microgram/kg/min, or sufentanil (S-group) 1 microgram/kg before surgery with dosage adjustments according to haemodynamic parameters. Prolactin, growth hormone, cortisol, epinephrine and norepinephrine were measured 60 min before anaesthesia, 30 min after start of surgery and 30 min after extubation.

RESULTS

(Significance level: P < 0.05) Only prolactin increased significantly in both groups during the surgical procedure, the S-group showing a greater increase than the R-group. Cortisol and norepinephrine concentrations decreased during surgery in both groups significantly. Growth hormone and epinephrine concentrations only decreased in the S-group during operation while there was no significant change in the R-group. The blood pressure dropped by about 30% in both groups intraoperatively while there was a tendency towards lower heart rates in the R-group with 58/min vs. 64/min in the S-group (mean).

CONCLUSION

The increase of prolactin concentrations could be interpreted as a result of the stimulation of mu 1-receptors. As all other measured stress hormones did not increase in both groups, remifentanil and sufentanil both provide an effective suppression of noxious stimulation induced endocrine response.

Advances in airway pharmacology. Emerging trends and evolving controversy

The practice of emergency medicine is a constant onslaught of decision making and challenges and the issues of airway management are no exception. Obtaining proper airway control requires thoughtful organization and planning, and necessitates a thorough working knowledge of the drugs or medications employed. Because there are so many agents available, expertise in airway pharmacology has become essential. The emergency physician who is well versed in the uses, and the physiologic effects, contraindications, and alternatives of drugs administered is both providing immediate intervention and positively affecting patient outcome, which is certainly a goal worth achieving.

The influence of the type of anaesthesia on postoperative pain after kidney transplantation

The postoperative pain treatment is one of important factors of a successful outcome after kidney transplantation. Improperly controlled pain leads to agitation, tachycardia, hypertension and increases risk of respiratory complications. Many studies have demonstrated good analgetic effect of morphine delivered by the method of patient controlled analgesia (PCA). Because the intensity of postoperative pain in end-stage kidney insufficiency patients can be modified by the type of received anaesthesia, it was decided to analyze the influence of standardized general anaesthesia on postoperative morphine consumption. 140 (ASA III) patients scheduled for kidney transplantation were included. Patients were divided into four groups; group K (control)--anaesthetised with fentanyl and N2O, group 1--fentanyl, N2O plus halothane, group 2--fentanyl, N2O plus propofol, group 3--fentanyl, N2O plus isoflurane. After operation and initial loading dose, PCA infusion of morphine was started. Bolus doses were set to 30 ug/kg, and lockout interval 10 min. Our results suggest that observed greater morphine consumption after GA with the use of propofol is connected with better psychomotor functions. In that group patients were better oriented and more efficiently controlled the PCA pump and pain.

Dose-response and onset/offset characteristics of rapacuronium

BACKGROUND

A rigorous study of the dose-response relation of rapacuronium has, to our knowledge, yet to be performed. In addition, there is little information available regarding the onset or offset profile of rapacuronium when administered in subparalyzing doses. These issues necessitate further study.

METHODS

Forty-seven adult patients, American Society Anesthesiologists physical status I or II, were studied. Tracheal intubation was accomplished without muscle relaxants. Anesthesia was maintained with use of nitrous oxide, propofol, and alfentanil. The electromyogram of the first dorsal interosseous muscle was measured using a monitor. Single stimuli at 0.10 Hz were administered. A single dose of rapacuronium was administered. After log-dose or logit transformation of the data, the best-fit line of regression was determined using the method of least squares. For each subject, the authors estimated the 50% effective dose (ED50) and 95% effective dose (ED95) from the Hill equation using the slope obtained from regression analysis. The onset times to 50 and 90% of peak effect were estimated in a subset of 10 individuals in which peak twitch depression decreased to the range of 90-99%.

RESULTS

The calculated ED50 and ED95 values for rapacuronium were 0.39 +/- 0.08 (SD) and 0.75 +/- 0.16 mg/kg, respectively. After a single ED95 dose, 90% of the drug's peak effect was evident in 77 +/- 17 s. After this dose, rapacuronium has a clinical duration of 6.1 +/- 1.1 min.

CONCLUSIONS

The authors found the ED95 of rapacuronium to be substantially less than suggested by previous estimates. Rapacuronium has an onset profile that is not different from that previously reported for succinylcholine. The rate of spontaneous recovery was faster after rapacuronium than the authors previously observed after mivacurium administration but was slower than after succinylcholine, using an identical protocol.

[The effect of propofol anesthesia on striatal dopamine of awake freely moving and anesthetized rats examined by in vivo microdialysis study]

We investigated the effect of propofol anesthesia on the level of interstitial dopamine in vivo awake free moving and anesthetized rats brain striatum using microdialysis techniques. Rats were implanted a microdialysis probe to right striatum of the brain and administered intravenously 20 mg.kg-1 of propofol for induction and followed by continuous infusion at 12.5, 25 and 50 mg.kg-1.hr-1 up to 1 hour. The microdialysis probe was perfused with artificial cerebrospinal fluid and dialysates from the probe were determined every 20 minutes by high performance liquid chromatography and electrochemical detection. Propofol anesthesia reduced the amount of dopamine derived from dialysate, but no prolonged increases of dopamine metabolites were observed, as we demonstrated in previous investigation for halothane, isoflurane or sevoflurane anesthesia. We hypothesize that the characteristics of propofol anesthesia for dopamine and its metabolites might contribute to low incidence of postoperative nausea and vomiting in its clinical use.

Propofol sedation for endoscopic procedures in children

BACKGROUND AND STUDY AIMS

Propofol sedation has been used successfully in various outpatient minor procedures in children. Limited data are available on the usefulness of propofol sedation during gastrointestinal endoscopic procedures in children. The aim of this study was to evaluate our experience of propofol sedation in pediatric gastrointestinal endoscopic procedures.

MATERIALS AND METHODS

The charts of all children who had undergone diagnostic endoscopic procedures, and were sedated by propofol, were retrospectively reviewed. Demographic data, cardiovascular monitoring, and drug dosages were recorded. Patients evaluated their sedation efficacy by answering a questionnaire before discharge.

RESULTS

A total of 104 children underwent 107 procedures. Propofol alone was given in 19 procedures and in combination with midazolam and/or fentanyl in 88 procedures. All procedures were completed and significant complication occurred in only one patient. No significant difference was observed in the amount of sedative drugs or recovery time between upper and lower endoscopic procedures. A lower propofol dosage was needed when a combination of drugs was given compared to propofol drug alone. Patients' assessment of their sedation showed that the vast majority had experienced postendoscopic amnesia.

CONCLUSION

Propofol sedation for endoscopic procedures is safe and acceptable for children. Propofol sedation should be offered to young children, especially those who express significant anxiety.

[Propofol and remifentanil in day surgery]

BACKGROUND

AIM OF THE STUDY

to compare AG versus MAC using propofol & remifentanil in a day surgery setting evaluating intra and postoperative clinical conditions and emergence times.

METHODS

Propofol and remifentanil, either for general anesthesia (AG) then conscious sedation (MAC), have been administered to 218 patients undergoing mainly plastic or proctologic surgery as day hospital. AG was induced with propofol 1.5-2 mg/kg followed by a continuous infusion of 10 mg/kg/h and remifentanil infused at 10 micrograms/kg/h; MAC was started with propofol 3 mg/kg/h and remifentanil 4-5 micrograms/kg/h; during the maintenance phase of both AG and MAC, infusion rates of both drugs were adjusted according to clinical needs. Diazepam (0.05-0.06 mg/kg) and/or midazolam (2-3 mg) were given as premedication or coinduction as necessary. All patients received field infiltration with local anesthetics (lidocaine or mepivacaine); patients under GA were artificially ventilated with O2/air through IOT or LMA. Surgical and anesthesiological data were collected on specially designed records, with special attention to time intervals between anesthesia (FA) and surgery (FC) end and eyes opening (EO), orientation (OR), return of spontaneous breathing (SR), extubation (EST), sitting (SED), walking (CAMM), dressing (VEST) and discharge (DIM); data were analyzed with parametric and non parametric analysis of variance.

RESULTS

All emergence intervals were longer under AG than under MAC: the earlier in the range of 4-5 vs 0.5-1 min; for the late intervals; FA-SED 24 +/- 18 vs 15 +/- 8, FA-PIED 65 +/- 48 vs 34 +/- 17, FA-VEST 69 +/- 58 vs 33 +/- 17, FA-CAMM 68 +/- 42 vs 39 +/- 19. Discharge times (83 +/- 67 vs 73 +/- 60) were similar between the two groups. Drugs consumption under AG were roughly double than under MAC; total dose infused of propofol (mg/kg/min) 0.118 +/- 0.044 vs 0.06 +/- 0.036; total dose of remifentanil (microgram/kg/min): 0.106 +/- 0.049 vs 0.066 +/- 0.027. AG resulted in a higher % incidence of intraoperative hypotension and bradycardia: hypotension 61.7 vs 25.7 and bradycardia 30.3 vs 12.4. SaO2 decreased more commonly during MAC than AG (20.9% vs 10.1); intraoperative itching was referred in 20% of MAC patients. Conversions rate from MAC to AG was 2.8%. Psychomotor agitation was more frequent following AG (14%) than MAC (2%); nausea (1%), vomiting, shivering (12%), headache (2%), ortostatic hypotension (2%) were similar between the two groups. Diazepam and/or midazolam caused a significant prolongation of recovery intervals, for both AG and MAC with a mean delay of the order of 100-200%.

CONCLUSIONS

Propofol- remifentanil gave excellent conditions for a wide variety of day surgery procedures, offering good anesthesia with quick emergence; the addition of bdz, even at low doses, prolongs significantly discharge times.

Intraoperative variables and early outcome after aneurysm surgery

BACKGROUND

The purpose of this study was to investigate the effects of blood pressure, temperature, and anesthetic agents on outcome in patients undergoing craniotomy for cerebral aneurysms.

METHODS

All ruptured and unruptured intracranial aneurysms operated on from 1992 to 1998 were reviewed retrospectively. The data included 297 aneurysms (190 ruptured and 107 unruptured). Data were collected on variables known to influence outcome after aneurysmal subarachnoid hemorrhage as well as on intraoperative factors that might influence outcome (intraoperative blood pressure, temperature, temporary clipping, anesthetic agents). Outcome was assessed at discharge using the Glasgow Outcome Scale.

RESULTS

In univariate analysis of patients with ruptured aneurysms, younger age, better clinical grade, lower Fisher grade, lower intraoperative blood pressure (maximum systolic and mean blood pressure), smaller decrease in intraoperative compared to preoperative systolic blood pressure, shorter duration of surgery, and use of propofol, pancuronium, or N(2)O were associated with significantly better outcome. In patients with unruptured aneurysms, increased intraoperative minimum diastolic and mean blood pressure, a decrease in the difference between multiple measures of preoperative and intraoperative blood pressure, and a shorter duration of surgery were associated with significantly better outcome. Intraoperative temperature did not affect outcome in either group. In multivariate analysis of patients with ruptured aneurysms, younger age, better clinical grade, lower maximum systolic intraoperative blood pressure, shorter duration of surgery, and use of propofol were independently associated with better outcome.

CONCLUSIONS

Multivariate analysis of intraoperative factors affecting outcome in patients undergoing craniotomy for ruptured aneurysms shows that decreased intraoperative blood pressure and use of propofol are associated with improved outcome. Univariate analysis suggests that decreasing the magnitude of drop in blood pressure intraoperatively from preoperative values in patients with ruptured or unruptured aneurysms is associated with better outcome. Intraoperative hypothermia did not affect outcome.

Airway management for carinal tumour resection

We describe the airway management during resection of a right main bronchial and carinal "pseudotumour" in a 16-year-old patient. Two 5 mm microlaryngoscopy tubes (Mallinckrodt) were inserted side by side in the trachea, with one positioned in the left main bronchus and the other just below the larynx. Independent ventilation of both lungs, with suctioning and fibreoptic inspection of the lower trachea, could easily be carried out. Current airway devices used to isolate lung ventilation are reviewed and their limitations considered.

Comparison of intubating conditions following propofol and succinylcholine with propofol and remifentanil 2 micrograms kg-1 or 4 micrograms kg-1

We evaluated the intubating conditions, haemodynamic responses and duration of apnoea in 60 healthy adult patients after propofol 2 mg kg-1 combined with either a bolus of remifentanil 2 micrograms kg-1 or 4 micrograms kg-1, or succinylcholine 1 mg kg-1. Patients intubated following remifentanil showed dose-dependent intubating conditions, similar at 4 micrograms kg-1 to the conditions produced with succinylcholine. Post-induction mean arterial pressure decreased from baseline values by 21% (P < 0.0001), 28% (P < 0.0001) and 8% (P > 0.05) in the remifentanil 2 micrograms kg-1, remifentanil 4 micrograms kg-1 and succinylcholine 1 mg kg-1 groups, respectively. The mean (SD) duration of apnoea following induction was 9.3 (2.6) min and 12.8 (2.9) min in the remifentanil 2 micrograms kg-1 and 4 micrograms kg-1 groups, and 6.0 (0.9) min in the succinylcholine group (P < 0.001 between groups).

Clinical comparison of either small doses of fentanyl or remifentanil for blunting cardiovascular changes induced by tracheal intubation

BACKGROUND

To compare in a prospective, randomized study the effects on cardiovascular changes after tracheal intubation produced by small doses of either remifentanil or fentanyl.

METHODS

With Ethical Committee approval, after intravenous midazolam premedication (0.05 mg.kg-1), 30 normotensive, ASA physical status I-II patients, without cardiovascular or respiratory diseases, and with a Mallampati score < 2, were randomly allocated to receive an intravenous bolus of either 3 micrograms.kg-1 fentanyl (n = 15) or 1 microgram.kg-1 remifentanil (n = 15) infused over 60 sec and followed by a 0.15 microgram.kg-1.min-1 continuous intravenous infusion. General anesthesia was then induced with propofol (2 mg.kg-1), followed by atracurium besilate (0.5 mg.kg-1) to facilitate tracheal intubation. Following intubation, the lungs were ventilated mechanically using a 60% nitrous oxide in oxygen mixture with a 1% inspired fraction of sevoflurane. Arterial blood pressure and heart rate were recorded before anesthesia induction (baseline), one minute after induction of anesthesia, immediately after tracheal intubation and every minute for the first five minutes after intubation.

RESULTS

Systolic arterial blood pressure values were significantly higher in the Fentanyl than in the Remifentanil group patients from 2 to 5 min after tracheal intubation (p < 0.01), while no differences were observed between the two groups in either diastolic arterial blood pressure or heart rate values. Four patients in the Remifentanil group (26%) but only one patient in the Fentanyl group (7%) showed systolic blood pressure values < 90 mmHg during the study period (p = not significant); however, the observed decreases in systolic arterial blood pressure values were transient and did not require treatment for any subject.

CONCLUSION

We conclude that in healthy normotensive patients, the control of cardiovascular responses to tracheal intubation obtained with a 1 microgram.kg-1 loading dose of remifentanil is more effective than that provided by a 3 micrograms.kg-1 bolus of fentanyl, with the advantage of no risks for postoperative respiratory depression.