Comparison of subhypnotic doses of thiopentone vs propofol on the incidence of postoperative nausea and vomiting following middle ear surgery

Background : Middle ear surgery is associated with a high incidence of emetic sequelae and propofol has been reported to have antiemetic activity in subhypnotic doses.
Methods : In a double-blind, randomized study, the patients received either thiopentone 1.0 mg.kg^-1 (n=26) or 0.5 mg.kg^-1 propofol (n=26) at the end of middle ear surgery under isoflurane-N₂O-fentanyl-vecuronium anaesthesia. Trained nurses, unaware of the group assignment, assessed postoperative nausea, retching and vomiting up to 24 h after the end of anaesthesia. Droperidol 10μg.kg^-1 was used as a "rescue" antiemetic.
Results : The main result was that the patients in the propofol group did not suffer from retching and vomiting (R&V) during the first 6 h, whereas these symptoms occurred in 46% ( P <0.001) of the patients in the thiopentone group. The patients in the propofol group needed significantly less droperidol during the first 24 h (mean number of doses 0.39 ± 0.57 (SD)) than the patients in the thiopentone group (1.35 ± 1.47, P <0.005). Treatment with propofol was a predictor for lowered incidence of R&V, as well as male gender and negative history of motion sickness.
Conclusion : Propofol at a subhypnotic dose of 0.5 mg.kg^-1 provides prophylaxis against retching and vomiting for the first 6 h postoperatively after middle ear surgery. The incidence of nausea was not reduced by propofol.     

Lack of effect of flumazenil on the reversal of propofol anaesthesia

Propofol, like the benzodiazepines, activates the GABA_A receptor-chloride ionophore complex; they potentiate one another. Since neither pharmacodynamic nor pharmacokinetic data concerning drug interaction between flumazenil and propofol is available, and especially considering the relationship of binding sites, flumazenil, the antagonist of benzodiazepines, was investigated to determine its effect upon recovery from propofol anaesthesia. Forty women receiving dilatation and curettage procedures were included in this double-blind test. After 50 μg fentanyl, propofol 2 mg · kg^-1 was injected for induction and followed by infusion at the rate of 15 mg · kg^-1 · hr^-1. After the operation, patients were given normal saline (Group A) or flumazenil 10 μg · kg^-1 (Group B) randomly.
Recovery time in Group A was 15.2±5.1 min and Group B 15.8±4.8 min. Propofol concentrations at the end of infusion were 4.17±1.33 μg ·ml^-1 (Group A) and 4.03±1.45 μg · ml^-1 (Group B); these then declined to 1.22±0.17 μg · ml^-1 (Group A) and 1.18±0.15 μg · ml^-1 (Group B) when patients were able to open their eyes on command. No significant differences were found between the groups based on propofol concentrations and recovery time, nor did haemodynamic changes differ between them after administration of reversal agents. It was concluded that flumazenil 10 μg · ml^-1 does not influence recovery from propofol anaesthesia.     

Intramuscular dexmedetomidine premedication—an alternative to midazolam-fentanyl-combination in elective hysterectomy?

Sedation, anxiolysis, intubation responses and fentanyl anaesthetic requirements were investigated in a double-blind, randomized study in twenty ASA I-II elective hysterectomy patients. Ten patients received dexmedetomidine 2.5 μg kg^-1 i.m. 60 min before induction and saline placebo i.v. 2 min prior to induction (= DP group). Ten patients received midazolam 0.08 mg kg^-1 i.m. 60 min and fentanyl 1.5 μg kg^-1 i.v. (= MF group) 2 min before induction of anaesthesia with thiopentone 4 mg kg^-1. Anaesthesia was maintained with 70% nitrous oxide in oxygen and with fentanyl 2 μg kg^-1 i.v. increments according to predetermined criteria. Both premedications induced sedation ( P < 0.01 in both groups) and anxiolysis ( P < 0.01 in DP vs <0.05 in MF group) without any differences between the groups. Haemodynamic changes following tracheal intubation did not significantly differ between the groups. Intraoperatively systolic and diastolic arterial pressure were 15% and 13% lower in DP group ( P < 0.01 and P < 0.05 for drug effect), the mean heart rate was approximately 9 beats min^-1 lower in DP group (n.s.). Fentanyl was required more often in MF group: median 3.5 (QD 1.5) vs. 2.5 (QD 0.5) times in DP group ( P < 0.05), the total amount being 57% smaller in DP group: 0.03 (QD 0.01) vs. 0.07 (QD 0.02) μg kg^-1 min^-1 ( P < 0.05). Postoperative course and analgesic requirements were similar in both groups. Dexmedetomidine premedication may offer an alternative to current anaesthesia practice in elective hysterectomy.     

Propofol influences the electroretinogram to a lesser degree than thiopentone

Background: The Electroretinogram (ERG) is used clinically to assess the function of retina. Anaesthetic agents are known to affect ERG, and as anaesthesia is often needed in children and uncooperative patients, knowledge about its effects is of clinical importance. Barbiturates selectively depress ERG components, and we compared thiopentone with propofol to assess if the latter preserved retinal function better.
Methods: Ten pigs, average weight 17 kg (SD ± 2 kg) were anaesthetized randomly with propofol 10 mg kg^-1 or thiopentone 30 mg kg^-1. Anaesthesia was maintained by 65% nitrous oxide in oxygen and continuous infusion of the induction agent, i.e. 10 mg kg^-1 h^-1 of propofol, or 10 mg kg^-1 h^-1 for the first hour, then 5 mg kg^-1 h^-1 of thiopentone, with doses being based on pilot studies. After an interval of one week the programme was repeated using the other agent. After 40 minutes dark-adaptation, responses to single flashes of graded intensities from a xenon flashlamp were recorded at five-minute intervals. The a- and b-wave amplitudes and implicit times (time to peak), and a-wave slopes were determined.
Results: The b-wave implicit time was significantly shorter during propofol anaesthesia than when using thiopentone. The effect was most pronounced at the lowest intensities (P < 0.01). No statistically significant differences were found in the amplitudes of the b-waves. The a-wave appeared at lower stimulus intensity (P < 0.05) and the a-wave slopes were significantly steeper (P < 0.01) during propofol anaesthesia.
Conclusion: Propofol accordingly appeared to preserve the photoreceptor response better than thiopentone, and may therefore be considered to be more suitable for ERG recordings than thiopentone.     

Cardiovascular Effects of Etomidate Used for Induction and in Combination with Fentanyl-Pancuronium for Maintenance of Anaesthesia in Patients with Valvular Heart Disease

The effects of induction of anaesthesia by etomidate 3 mg·kg-^-1 followed by continuous infusion of etomidate 2 mg·min^-1, fentanyl 0.01 mg·kg^-1 and pancuronium 0.1 mg·kg^-1 were studied in ten patients with valvular heart disease. No haemodynamic changes were seen after injection of etomidate, but after fentanyl was given thew was a significant decline in cardiac index (10%), in mean arterial systemic pressure (20%), in systemic vascular resistance (14%), in left ventricular minute work index (27%) and in right ventricular minute work index (21%) compared to the control values. After supplementing with pancuronium, no further significant changes were seen. There was no significant change in the pulmonary vascular resistance during the whole study. In conclusion, it appears that etomidate is a safe intravenous agent, and is worth further study, in particular in patients with minimal cardiac reserve requiring high inspired oxygen tension.     

Effects of propofol on ipecacuanha-induced nausea and vomiting

Background : The purpose of this study was to evaluate if propofol has 5-HT₃ antagonistic effects. Ipecacuanha is known to release serotonin (5-HT) in the gastrointestinal tract and therefore ipecacuanha syrup was used to induce nausea and vomiting. The 5-HT₃ antagonist ondansetron was used as a control substance.
Results : During the first 150 min after ingestion of ipecacuanha there were no retchings during the ondansetron infusion ( P = 0.01 vs placebo, P =0.02 vs propofol) and significantly fewer retchings during propofol infusion compared to placebo ( P <0.02). There was no nausea during the ondansetron infusion ( P <0.01 vs placebo and propofol) but the volunteers experienced nausea both during the placebo and propofol infusion (NS).
Conclusion : This study in volunteers has shown that propofol reduces the intensity of retching after oral intake of ipecacuanha syrup. As ipecacuanha releases 5-hydroxytryptamine, it can be concluded that propofol may have a weak 5-HT₃ antagonistic effect.
Method : Ten healthy male volunteers (20–37 years) were studied on three occasions and were randomly allocated to receive a concomitant infusion of propofol (initial bolus 0.1 mg kg^-1 then 1 mg kg^-1h^-1), ondansetron (initial bolus 0.11 mg kg^-1 then 14 μg kg^-1 h^-1) and placebo on either occasion. The infusions started 30 min before oral ingestion of 30 ml of ipecacuanha and continued until 150 min after the intake. The number of retchings was recorded and the intensity of nausea was estimated by the subjects on a visual analog scale.     

Desflurane versus propofol maintenance for outpatient laparoscopic cholecystectomy

Background : The aims of the study were to evaluate costs and clinical characteristics of desflurane-based anaesthetic maintenance versus propofol for outpatient cholecystectomy.
Methods : All 60 patients received ketamine 0.2 mg kg^-1, fentanyl 2 μg kg^-1 and propofol 2 mg kg^-1 for induction. Ketorolac 0.4 mg kg^-1 and ondansetron 0.05 mg kg^-1 +droperidol 20 μg Kg^-1 was given as prophylaxis for postoperative pain and emesis, respectively. The patients were randomly assigned into Group P with propofol maintenance and opioid supplements, or Group D with desflurane in a low-flow circuit system.
Results : All the patients were successfully discharged within 8 h without any serious complications. Emergence from anaesthesia was more rapid after desflurane; they opened their eyes and stated date of birth at mean 6.4 and 8.4 min respectively, compared with 9.6 and 12 min in the propofol group (P<0.05). Nausea and pain were more frequent in Group D, 40% and 80% respectively; versus 17% and 50% in Group P (P<0.05). By telephone interview at 24 h and 7 d after the procedure, there was no major difference between the groups. With desflurane, drug costs per case were 10 $ lower than with propofol.
Conclusion : We conclude that desflurane is cheaper and has a more rapid emergence than propofol for outpatient cholecystectomy. However, propofol results in less pain and nausea in the recovery unit. Despite ondansetron and droperidol prophylaxis, there was still a substantial amount of nausea and vomiting after desflurane.     

Effects of fentanyl or alfentanil as supplement to propofol anaesthesia for termination of pregnancy

One hundred and twenty patients undergoing early legal termination of pregnancy by dilatation and suction curettage before 12 weeks of pregnancy were randomly allocated to receive total intravenous propofol anaesthesia either alone or supplemented with fentanyl 1.5 μg·kg^-1 or alfentanil 15 μg kg^-1. Supplementation with fentanyl or alfentanil improved operating conditions ( P <0.01), reduced total propofol requirements ( P < 0.01) and reduced postoperative pain intensity ( P < 0.05). Immediate recovery, assessed by the time patients took to open the eyes, to give correct date of birth and by co–operation score, was more rapid in the alfentanil group compared to the control group ( P < 0.05), whereas there was no significant difference between the alfentanil and fentanyl groups. The three anaesthetic techniques did not differ with regard to side effects.
In conclusion, total intravenous propofol anaesthesia in patients undergoing early termination of pregnancy was improved by supplementation with either fentanyl 1.5 μg kg^-1 or alfentanil 15 μg–kg^-1. The benefit was slightly greater with alfentanil than with fentanyl.     

Intravenous propofol vs thiamylal-isoflurane for caesarean section, comparative maternal and neonatal effects

Several studies on propofol (Diprivan) for induction of anaesthesia during caesarean section have demonstrated its safety, however, its safely during maintenance of anaesthesia is not yet fully evaluated.
The present study was undertaken to compare the maternal and neonatal effects of propofol or isoflurane in 74 term parturients undergoing primary or repeat caesarean section. Patients were randomly assigned to two groups, propofol group (n = 37) received propofol 1.5–2.5 mg·kg^-1 for induction followed by a continuous infusion of propofol of 0.05–0.2 mg 4mD kg^-1 · min^-1. The isoflurane group (n=37) received thiamylal 3–4 mg · kg^-1 for induction followed by isollurane 0.25–0.75% for maintenance. All patients had rapid sequence induction using suceinyl-choline and endotracheal intubation, 50% N₂O and O₂ were used in all patients until delivery. After delivery N₂O concentration was increased to 67% and intravenous butorphanol (Stadol) was given as needed. Patients in the propofol group had less hypertension after intubation ( P <0.05) and this was also of shorter duration compared to patients in the isoflurane group (5 min vs 10 min respectively). Maternal blood loss as well as intraoperative awareness and recovery time did not differ significantly between the two groups. Neonatal status as ascertained by Apgar scores, cord acid base status and the neurological and adaptive capacity scores (NACS) was equally good in both groups. It is concluded that propofol used for induction and maintenance of anaesthesia is a safe alternative to thiamylal/isoflurane for patients undergoing caesarean section and is associated with less hypertensive response during laryngoscopy and intubation.     

Effects of propofol on the human heart electrical system: a transesophageal pacing electrophysiologic study

Previous studies have shown that infusion of propofol has sometimes been associated with bradyarrhythmias. To evaluate the effects of propofol on the electrical system of the heart, we carried out an electrophysiologic study with transesophageal pacing on ten healthy subjects scheduled for minor elective maxillo–facial surgery. By means of atrial pacing conducted by a progressive increase in stimulation cycles, we determined, in awake patients and during propofol anesthesia (2.5 mg kg^-1 for induction, followed by 100 μg kg^-1 min^-1 for maintenance), the correct sinus recovery time and the eventual appearance of Wenckebach atrio–ventricular block. We did not notice sinoatrial node depression or pathologic increase in the atrio–ventricular conduction.     

Influence of body compartments on propofol induction dose in female patients

Background: For induction of anaesthesia, drugs such as pro-pofol are commonly administered according to a per weight basis. However, drugs are primarily distributed to the fat-free mass. This study was undertaken to determine the relationship between propofol requirement for induction and body mass determined by bioimpedance analysis (BIA) or by body mass index (BMI).
Methods: Twenty-one ASA 1 female patients scheduled for gynaecologic surgery received propofol for induction at 133 mg. min^-1. Stepwise regression analysis was used to describe the relationships between propofol requirement for loss of consciousness and age, body weight, and lean body mass measured by BIA and BMI (independent variables).
Results: Loss of consciousness was obtained with a propofol dose (Mean (SEM)) of 2.170.10 mgkg^-1. Stepwise analysis showed that propofol requirement (total dose) was not proportional to weight or age but related to lean body mass as determined by BIA and to body mass index (r² = 0.447; global P - value <0.007). BMI was the only regressor variable when the propofol dose was expressed in mg. kg^-1 (r² = 0.661; P <0.001).
Conclusions: Our results indicate that propofol requirements for induction are proportional to the lean body mass rather than total body weight.     

Influence of Dixyrazine on Intestinal and Renal Vasoconstrictor Responses During Fentanyl-Nitrous Oxide Anaesthesia

In cats (n=24) anaesthetized with fentanyl-nitrous oxide and diazepam, stimulation of the hypothalamic defence-alarm area (DA) or afferent activation of somatic pain fibres (SA), elicited a pronounced increase in intestinal (DA 297%, SA 107%) and renal (DA 214%, SA 90%) vascular resistance as well as a decrease in diuresis. These stress-related responses were markedly counteracted by dixyrazine (0.15-0.5 mg · kg^-1 b.w. i.v.), especially in the kidney where the subsequent increase in vascular resistance to DA and SA stimulations amounted to only 25% and 13%, respectively, while diuresis increased. Corresponding data for stimulation-induced increases in intestinal vascular resistance after dixyrazine were DA 156% and SA 28%. Dixyrazine is suggested to act both through interaction with peripheral α-adrenergic mechanisms in control of vascular tone and through central nervous cardiovascular reflex depression. In man (n=7), during a similar form of anaesthesia, portal vein blood flow (1137±177 ml) was measured by the continuous thermodilution method. Preportal tissue vascular resistance during surgery decreased significantly (11.3 vs 8.7 kPa · min ml^-1 · 10^-3) after i.v. dixyrazine (0.15mg · kg^-1 b.w.). A concomitant increase in oxygen uptake in preportal tissues occurred (19.9 ml min^-1 vs 24.5 ml · min^-1).     

Cardiovascular Effects of High-Dose Fentanyl Anaesthesia

An anaesthetic technique using high-dose fentanyl for coronary artery surgery is described. Fentanyl 160 or 70 μg kg^-1 was used as the sole anaesthetic agent, and patients were ventilated with air/O₂ (fentanyl 70 μg kg^-1) or N₂O/O₂ (fentanyl 60 μg kg^-1). Cardiovascular data from 30 patients are presented. Fentanyl caused no significant cardiovascular depression. The only statistically significant changes in cardiovascular parameters were seen in the patients who received fentanyl 60 μg kg^-1. Five minutes after skin incision there was an increase in peripheral resistance. Diastolic pressure was increased following sternotomy. Problems associated with this technique of anaesthesia are a 50% incidence of hypertension following sternotomy (requiring treatment with sodium nitroprusside) and prolonged respiratory depression. The lack of cardiovascular depression produced by fentanyl and the ability of fentanyl to reduce hormonal and metabolic responses to surgery make it a satisfactory technique for cardiac anaesthesia.     

Contradictory effects of dopamine at 32°C in pigs anesthetized with ketamine

Background: In critically ill patients who were surface cooled to 332C, we have observed that dopamine sometimes causes a substantial decrease in blood pressure. The present study was designed to compare the effects of dopamine in normothermia to those seen after surface cooling to 32C.
Methods: Seven pigs with a mean body weight of 21 kg were anesthetized with ketamine and muscle relaxation was induced with pancuronium. They were mechanically ventilated and given dopamine infusions (5 and 12 μg · kg^-1 min^-1) in normothermia and after surface cooling by cold water immersion to a central blood temperature of 320C (range 31.6–32.6C).
Results: In normothermia, dopamine at a dose of 5 μg · kg^-1 min^-1 increased mean arterial blood pressure (MAP) by 16% ( P < 0.01) and cardiac output (CO) by 9% ( P =0.051); at 12 μg kg^-1 min^-1 dopamine increased MAP by 26% ( P < 0.01) and CO by 18% ( P < 0.01). In hypothermia, MAP and CO did not change at an administration rate of 5 μg kg^-l · min^-1; at 12 μg · kg^-1 min^-1 CO was unchanged but MAP was significantly reduced by 15% ( P < 0.01).
Conclusion: Dopamine increased CO and MAP in normothermia but not at 32C, where there was even a significant reduction of MAP in this porcine model.     

Recovery characteristics of propofol anaesthesia, with and without nitrous oxide: a comparison with halothane/nitrous oxide anaesthesia in children

Few studies have examined whether nitrous oxide influences the recovery characteristics of propofol anaesthesia. The present study examined the effect of nitrous oxide on the recovery characteristics of propofol anaesthesia, and compared these data with those for halothane/nitrous oxide anaesthesia. Sixty children aged 3–12 years were assigned at random to receive one of three maintenance regimens: propofol with or without nitrous oxide (70%) or halothane/nitrous oxide (70%). During propofol/N₂O anaesthesia, the infusion rate of propofol (180±39 μg·kg⁻¹·min⁻¹) required to maintain the mean arterial pressure and heart rate within 20% of the baseline values was significantly less than that during propofol/O₂ (220±37 μg·kg⁻¹·min⁻¹; P <0.005). The time from discontinuation of anaesthesia to eye-opening (11±6 min), to response to commands (12±6 min), and to return of full wakefulness (21±10 min) after propofol/N₂O were similar to those after propofol/O₂, but significantly less (by approximately 30%) than those after halothane ( P <0.05). The overall incidence of emesis after propofol/N₂O (53%) was greater than that after propofol/O₂ (17%, P <0.05) and comparable to that after halothane/N₂O (58%). These data suggest that N₂O has little effect on the rate of recovery after propofol, but significantly increases the incidence of postoperative emesis, thereby attenuating one of the main attributes of propofol anaesthesia.     

Comparison of propofol/alfentanil anaesthesia with isoflurane/N2O/fentanyl anaesthesia for renal transplantation

Total intavenous anaesthesia (TIVA) with propofol and alfentanil was compared with balanced anaesthesia (BA) in 30 uraemic patients undergoing renal transplantation. TIVA (n=15) was induced with propofol and alfentanil and maintained with propofol and alfentanil infusions, which were started immediately after induction. Thereafter the infusion rates were adjusted as needed. Ventilation was with oxygen in air. BA (n= 15) was induced with thiopentone and fentanyl and maintained with isoflurane/N20/fentanyl. Vecuronium was used for muscle relaxation in both groups. Mean infusion rates for propofol and alfentanil were 10 1.8 mg kg^-1 h^-1 and 70 9 μg kg^-1 h^-1, respectively. To control hypertension during TIVA, larger amounts of propofol and alfentanil were needed and slower recovery was observed than in previous studies in ASA 1–2 patients. Also, significantly more vecuronium was needed during TIVA than during BA ( P < 0.05). The recovery parameters were similar in both groups, except for the occurrence of nausea, which was less after TIVA. In conclusion, TIVA had no clinical advantages over BA.     

Multiple Dose Kinetics of Ketobemidone in Surgical Patients

Twelve patients scheduled for major abdominal surgery were selected for a study of the kinetics of ketobemidone during the day of surgery and in a follow-up study 3–5 days after surgery. In six patients ketobemidone was administered as ketobemidone plain and in the other six, it was given as Ketogin®, a combination formula containing a spasmolytic substance in addition to ketobemidone. Plasma samples were collected for approximately 24 h following induction of anesthesia, during which time multiple doses of ketobemidone were administered. A single-dose study was performed 3–5 days after surgery using the same drug. No significant differences were found between the two formulations of ketobemidone. Plasma clearance did not change significantly between the two periods of study, being 18.0±4.4 ml · kg^-1 · min^-1 peroperatively and 21.7±7.6 ml · kg^-1 · min^-1 postoperatively. Peroperative V_{d area} was significantly larger than post-operative V_{d area}, 5.84±2.621 · kg^-1 and 3.63±0.381 ·; kg^-1, respectively. T1/2 terminal decreased from 3.84±1.6 h peroperatively to 2.06±0.44 h postoperatively.     

Effects of induced hypotension on arterial blood–gases under spontaneous breathing

The effects of deliberate hypotension on both Pao₂ and Paco₂ were investigated under isoflurane anaesthesia with spontaneous breathing from a laryngeal mask. Lumbar epidural block was introduced; anaesthesia was induced with thiamylal (4 mg kg^-1) and maintained with 0.5% isoflurane in nitrous oxide (4 1 min^-1) and oxygen (2 1 min^-1) under spontaneous breathing. After that nitroglycerin, trimetaphan or prostaglandin E₁ were used to induce a hypotension of 70% of control. All three drugs significantly decreased Pao₂, from 19.9 ± 3.3, 19.2 ±2.7, and 19.6 ± 3.1 kPa to 14.6 ± 1.9, 16.6 ± 2.2, and 16.2 ± 2.4kPa (mean ± s.d.), respectively; none of them increased Paco₂. In spite of the sparing of functional residual capacity under spontaneous breathing, the levels of reduction of Pao₂ were the same as levels reported in paralyzed and mechanically ventilated subjects. In conclusion, under deliberate hypotension Pao₂ decreases to a considerable degree, even under spontaneous breathing, presumably not because of alveolar hypoventilation, but because of the suppression of hypoxic pulmonary vasoconstriction by the drugs used in this study.     

Propofol sedation and gastric emptying in volunteers

Background : The purpose of this study was to evaluate the effects of light propofol sedation on gastric emptying and orocecal transit time (OCT).
Methods : Ten healthy male volunteers were studied on 2 occasions separated by at least 1 week and were randomly allocated to receive either propofol sedation or i.v. saline as a control. During propofol sedation the volunteers were sedated to grade 2–3 on a 5-grade scale. This was achieved by a propofol infusion of 5 mg kg^-1 h^-1 initially, which was then titrated down to a dose of 2.4±0.7 mg kg^-1 h^-1 Paracetamol absorption was used as an indirect measure of the rate of gastric emptying and OCT was determined by use of the hydrogen breath test after ingestion of raffinose. Student's t -test for paired samples was used and the results are presented as means± SD.
Results: During propofol sedation the maximum concentration of paracetamol (C_max) was 115±26.8μl/L, time to peak concentration (T_max) 50±38.8 min, and the area under the curve during the first 60 min (AUC₆₀4793±1538 μmolXmin/L, versus C_max 99±20.8, T_max 69±41.9 and AUC₆₀ 3897±1310 during saline infusion. These differences were not statistically significant. OCT was significantly shorter during the control study, 180±32.4 min, than during propofol sedation, 217±64.9 min (P<0.05).
Conclusion : This study in volunteers has shown that gastric emptying of liquids seems uninfluenced by light propofol sedation. OCT was slightly prolonged during light propofol sedation.     

Cardiovascular depression by isoflurane and concomitant thoracic epidural anesthesia is reversed by dopamine

Interactive effects between exogenous dopamine (DA) and isoflurane (I) combined with thoracic epidural blockade (TEA) were studied in dogs during chloralose anesthesia. The I–TEA intervention per se decreased heart rate (HR; 28%), mean arterial pressure (MAP; 63%), cardiac output (CO; 54%), left ventricular dP/ dt (LVdP/dt; 75%) and LVdP/dt/systolic arterial pressure (SAP; 42%). Prior to the I–TEA intervention , dopamine increased MAP, CO, LVdP/dt, LVdP/dt/SAP and stroke volume (SV) already at the dose 10 μg–kg^-1. min^-1 and, additionally, increased mean pulmonary artery pressure (MPAP) at the dose 20 μg–kg^-1. min^-1. During the I–TEA intervention , the DA–induced increases in MAP and systemic vascular resistance (SVR) were significantly higher than prior to I–TEA, as indicated by significant ANOVA interactive effects. At the dose 10 μg–kg^-1 min^-1, DA restored MAP, CO, LVdP/dt, LVdP/dt/SAP and SV to levels found before the I–TEA intervention, while HR was restored first at the dose 20 μg–kg^-1 –min^-1. At the dose 20 μg–kg^-1–min^-1, DA also increased MAP (39%), LVdP/dt (119%), LVdP/dt/SAP (73%), SVR (28%) and MPAP (70%) above levels prior to I–TEA. To conclude, exogenous dopamine effectively and dose–dependently counters cardiovascular depression induced by the anesthetic technique of combining I and TEA. The pressor and systemic vasoconstrictor actions of dopamine are potentiated by conjoint administration of I and TEA.