Ventilatory effects of continuous epidural infusion of fentanyl

The effects of a continuous epidural administration of fentanyl on pain and on ventilation were studied in eight patients scheduled for orthopedic surgery of the knee. In each subject, epidural fentanyl was given by a bolus dose of 1 microgram.kg-1, followed by a continuous infusion of 1 microgram.kg-1.h-1 over 18 hours. Ventilatory measurements were performed during quiet breathing and during CO2 stimulation tests before surgery. After surgery measurements were made before epidural administration of fentanyl; 1, 2, 5, 18 hours after the start of epidural fentanyl infusion; and 6 hours after its discontinuation. Adequate pain relief was achieved in all patients during fentanyl administration. No significant change in ventilation was noted during quiet breathing. The slope of the ventilatory response to CO2 (VE/PaCO2) decreased significantly from 1.46 +/- 0.2 to 0.75 +/- 0.1 L.min-1.mm Hg-1 (mean +/- SEM; P less than 0.05) one hour after the onset of fentanyl administration, and remained stable throughout the infusion. Eighteen hours after the onset of epidural fentanyl infusion, VE/PaCO2 was still 0.76 +/- 0.14 L.min-1.mm Hg-1. At the end of fentanyl administration, plasma fentanyl levels measured in six patients had progressively increased from 0.42 +/- 0.02 ng.ml one hour after the onset of the infusion to 1.54 +/- 0.19 ng.ml at the end of the infusion. These results suggest that a continuous epidural administration of fentanyl is a technique of analgesia that can provide adequate pain relief but which is associated with ventilatory depression. However, with the doses used in this study, the ventilatory depression remained moderate and of no demonstrable clinical consequence.     

Side effects during continuous epidural infusion of morphine and fentanyl

Respiratory effects, nausea, somnolence, and pruritus were compared during a 48-hr period of continuous epidural morphine (n = 34) and fentanyl (n = 32) infusion in 66 patients following elective total replacement of the hip or knee joint. Respiratory effects were assessed by PaCO2. Side effects were assessed by visual analogue scale and considered to be present when the score was above 30. Assessment was made at preoperative visits then 3, 6, 12, 24, 36, and 48 hr after the epidural injection. The bolus dose and subsequent infusion rate were 3,900 +/- 1,300 micrograms and 427 +/- 213 micrograms.hr-1 for morphine, and 85 +/- 46 micrograms and 56 +/- 27 micrograms.hr-1 for fentanyl. Pain relief was similar in both groups. In the morphine group, PaCO2 elevation and nausea occurred over a period of more than 12 hr (P less than 0.05). In the fentanyl group, there was no PaCO2 change, and nausea was confined to the first few hours. Nausea was more severe (P less than 0.01 at six hours and more frequent (24 hr cumulative incidence, 53 vs 28%, P less than 0.05) in the morphine group. Somnolence was prominent within several hours in two-thirds of patients in both groups. Somnolence continued to decline thereafter in the morphine group, but it was demonstrable in approximately half of the patients throughout the second day in the fentanyl group. The incidence was higher in the fentanyl group at the 48th hr (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Ventilatory changes during nitrous oxide isoflurane anaesthesia in children

The changes in ventilatory variables under nitrous oxide isoflurane anaesthesia were studied in 10 children (mean age 46 +/- 13.4 months, mean weight 16.2 +/- 2.1 kg). Measurements of flow and volume were performed by pneumotachography. PE'CO2 was measured by capnography. The following variables (VE, VT, TI/TTOT, VI, PE'CO2) were measured or calculated under three increasing inspired isoflurane concentrations (0.75%, 1.5%, 2.25%). At each level of anaesthesia, ventilatory changes during exposure to an inspired CO2 fraction of 2% were studied. The increase in the inspired concentration of isoflurane was associated with a decrease in alveolar ventilation. PE'CO2 increased significantly with increasing depth of anaesthesia. The respiratory rate was slightly increased under light nitrous oxide isoflurane anaesthesia, but no further changes were observed with increasing depth of anaesthesia, although the children were breathing a mixture of nitrous oxide and oxygen. The ventilatory response to a raised inspired CO2 is markedly decreased under light nitrous oxide isoflurane anaesthesia, and decreases significantly with increasing depth of anaesthesia. In response to a raised CO2, VE, VT and VI increase, but respiratory rate decreases or remains constant and TI/TTOT is unchanged.     

阿芬太尼与芬太尼静吸复合全麻时对血流动力学的影响

对比观察了阿芬太尼与芬太尼对血流动力学的影响。选择ＡＳＡⅠ～Ⅱ级成年患者３６例，随机分成阿芬太尼组（ＡＦ）和芬太尼组（Ｆ）。在诱导和维持时，ＡＦ组静脉泵入阿劳太尼４０μｇ／ｋｇ和每分钟１μｇ／ｋｇ，Ｆ组静脉泵入芬大尼 ４μｇ／ｋｇ和每分钟 ０．１μｇ／ｋｇ，皆吸入 ０．５％～１．５％安氟醚和氧，并辅助维库溴胺维持麻醉。观察入室、给药后１、３、５分钟、静脉注射维库澳铵、硫喷妥钠后、插管后１、５分钟、消毒、切皮、探查、关腹、拔管后１、３分钟的血压、心率变化及给药前后血浆血管紧张素Ⅱ和醛固酮的变化。实验结果发现，ＡＦ组与Ｆ组于各观察点之间均无显著性差异，各参数的变化趋势基本相似。由于阿芬太尼较芬大尼对交感神经系统抑制作用强，临床上血流动力学指标的变化更为稳定些，可以减轻但不能完全消除插管和拔管的应激反应。     

Variable rate infusion of alfentanil as a supplement to nitrous oxide anesthesia for general surgery

In this study we attempted to define the minimal dosage of alfentanil (AF) needed in combination with nitrous oxide to provide satisfactory anesthetic conditions for lower abdominal gynecologic surgery. General anesthesia was induced in 12 women with AF (150 micrograms X kg-1) and 66% N2O in O2. An infusion of AF was started immediately after the AF induction dose and was varied between 25-150 micrograms X kg-1 X hr-1 as indicated by the patient's responses to stimulation during operations lasting 208 +/- 22 (SEM) min. Small bolus doses of AF (7 micrograms X kg-1) were administered to rapidly suppress precisely defined somatic, hemodynamic, and other sympathetic responses to stimulation. With one exception, all responses in all patients were controlled rapidly by increments of AF. The mean dosages of AF needed during different stages of surgery are reported. The AF infusion was stopped 16.2 +/- 1.2 min before discontinuing N2O. Recovery of consciousness along with satisfactory spontaneous ventilation occurred promptly after completion of the operation (4.0 +/- 0.5 min after N2O; 20.3 +/- 1.4 min after stopping AF infusion). This study demonstrates the feasibility of maintaining general anesthesia with N2O and a continuous AF infusion at a rate varied according to the patient's responses and allowing for prompt recovery of consciousness and satisfactory spontaneous ventilation at the conclusion of operations lasting as long as 5 hr.     

Spinal monitoring during vertebral column surgery under continuous alfentanil infusion.

An anaesthetic technique for surgical procedures on the vertebral column is described consisting of a continuous infusion of a short acting opioid, alfentanil, and a muscle relaxant, vecuronium, in combination with positive pressure ventilation using a nitrous oxide/oxygen mixture. It is shown that the two standard forms of spinal monitoring, wake-up testing and somatosensory cortical evoked potentials, can be employed effectively using this anaesthetic technique. Wake-up testing was performed in 23 patients. Average wake-up time was 10 min (SD 3.7 min). Evoked responses suitable for spinal monitoring could be obtained in 60 of 61 patients.     

Use of continuous infusion versus intermittent bolus administration of fentanyl or ketamine during outpatient anesthesia

The intraoperative and postoperative effects of fentanyl and ketamine administered continuously by infusion were compared with those produced by conventional intermittent bolus administration in 100 patients. After a standardized induction with thiopental 4 mg/kg intravenously, patients received either fentanyl (50 micrograms boluses vs. 2 micrograms/ml infusion) or ketamine (25 mg boluses vs. 1 mg/ml infusion) as intravenous adjuvants to nitrous oxide, 70% in oxygen. With continuous infusion, the doses of fentanyl and ketamine required were decreased 45% and 43%, respectively. Similarly, the times to awakening were decreased significantly, 62% and 60%, in the fentanyl and ketamine infusion groups, respectively. Intraoperative side effects (e.g., hypoventilation, hypotension, rigidity) were less frequent in the fentanyl infusion (vs. bolus) group but did not differ in the ketamine groups. Trieger scores were consistent with a more rapid recovery in both infusion groups. Incidences of common postoperative side effects (e.g., nausea, vomiting, visual disturbances, dizziness) did not differ significantly between bolus and infusion groups. However, excessive sedation was noted in 48% and 52% of patients in the fentanyl and ketamine bolus groups, respectively, compared with 4% and 8%, respectively, in the infusion groups. Discharge times were decreased by 29% and 13% in the fentanyl and ketamine infusion groups, respectively. The author concludes that continuous infusion fentanyl (0.1 micrograms . kg-1 . min-1) or ketamine (50 micrograms . kg-1 . min-1) significantly decreases the drug dosage requirement, improves intraoperative conditions, and decreases recovery time compared with the traditional intermittent bolus technique.     

Respiratory effects of nitrous oxide during halothane or enflurane anaesthesia in children

The respiratory effects of nitrous oxide (N2O) were studied during halothane and enflurane anaesthesia in 12 children (mean age 46.4 +/- 29.3 months, mean weight 15.3 +/- 4.2 kg) during surgery under continuous extradural anaesthesia. Four equipotent anaesthetic states were studied in random order: 1) halothane 1 MAC in oxygen, 2) halothane 0.5 MAC + 50% N2O, 3) enflurane 1 MAC in oxygen, 4) enflurane 0.5 MAC +50% N2O. End-tidal fractions of CO2 (PetCO2) and halothane and enflurane were measured using infrared analysers. The respiratory variables (tidal volume VT, minute ventilation VE, respiratory frequency F, inspiratory time Ti, mean inspiratory flow VI, effective inspiratory time Ti/Ttot) were measured using a pneumotachograph. Significant changes were observed between the four states for VE, VI, F and PetCO2, whereas the values of VT, Ti and Ti/Tot did not differ significantly. The respiratory depressant effect of 1 MAC of either halothane alone or of the mixture of halothane and N2O was very similar. During enflurane anaesthesia, PetCO2 was less increased when N2O was substituted for enflurane, owing to a significant increase in respiratory frequency. A marked decrease in VE together with an increase in PetCO2 was observed during enflurane anaesthesia (states 3 and 4) when compared to the corresponding states during halothane anaesthesia (states 1 and 2). The respiratory depressant effect of enflurane is greater than that of halothane in unpremedicated children, even when substituting N2O for an equal MAC fraction of enflurane.2+ The effect of N2O on respiratory patterns seems to depend on the inhalational agent used and/or on the vesting respiratory frequency.     

Cerebrospinal fluid pressure in patients with brain tumors: impact of fentanyl versus alfentanil during nitrous oxide-oxygen anesthesia

The effects on the cerebrospinal fluid pressure (CSFP) of alfentanil and fentanyl were compared during nitrous oxide-oxygen (N2O-O2) anesthesia in 24 patients who had brain tumors. Monitored variables included CSFP (lumbar subarachnoid catheter), heart rate from electrocardiographic lead II, mean radial arterial blood pressure, and arterial blood gas tensions. General anesthesia was induced with thiopental, 5 mg/kg IV in divided doses, and maintained with 70% N2O in O2; ventilation was held constant (PaCO2 = 37.4 +/- 1.6 mm Hg [mean +/- SEM]). After baseline data were recorded, 16 subjects were randomly assigned to receive either 5 micrograms/kg fentanyl as an intravenous bolus or 50 micrograms/kg alfentanil as an intravenous bolus, followed by an infusion of alfentanil at 1 micrograms.kg-1.min-1. Monitored variables were continuously recorded for 15 min after opioid injection. A third group of 8 patients was studied subsequently; they received only N2O-O2 during a 15-min observation period and served as controls. Blood pressure was held constant with an intravenous infusion of 0.1% phenylephrine, as needed; noxious stimulation was carefully avoided. Cerebrospinal fluid pressure remained unchanged both in patients who received N2O-O2 alone and in those who received fentanyl-N2O-O2. By contrast, those who received alfentanil-N2O-O2 had a gradual increase in CSFP, reaching 30% above baseline values after 10 min and stabilizing thereafter. Although the absolute increase in CSFP during normocarbic alfentanil-N2O anesthesia was relatively small (9.5 +/- 1.3 mm Hg to 13.0 +/- 1.3 mm Hg [mean +/- SE], P less than 0.05), the absence of a similar effect after fentanyl administration suggests that precautionary measures such as hyperventilation are advisable if alfentanil is used for potentiating normocarbic N2O-O2 anesthesia in neurosurgical patients with intracranial mass lesions.     

Target-controlled infusion of remifentanil or fentanyl during extra-corporeal shock-wave lithotripsy

BACKGROUND AND OBJECTIVE: Target-controlled infusions (TCIs) of remifentanil and fentanyl in conscious sedation regimes for extra-corporeal shock-wave lithotripsy have not been reported. We estimated the effect site concentrations of remifentanil and fentanyl needed to obtain adequate analgesia in 50% of patients (EC50) and compared both drugs in terms of intra- and post-procedure complications. METHODS: Forty-four adult patients were randomly distributed into two groups: Group R received remifentanil and Group F received fentanyl TCI with initial effect site concentrations of 1.5 and 2 ng mL(-1), respectively. Pain was assessed using a 10-point verbal analogue scale and <3 was considered adequate analgesia. Increments or decrements of 0.5 ng mL(-1) were then introduced for subsequent patients according to Dixon's up and down method. During the rest of the procedure, TCI was adjusted to maintain verbal analogue scale <3. RESULTS: Remifentanil and fentanyl EC50 were 2.8 ng mL(-1) (95% confidence interval (CI): 1.8-3.7 ng mL(-1)) and 2.9 ng mL(-1) (95% CI: 1.7-4.1 ng mL(-1)), respectively (n.s.). At EC50, the probability of having a respiratory rate <10 was 4% (95% CI: 0-57%) for remifentanil and 56% (95% CI: 13-92%) for fentanyl. Hypoxaemia, vomiting and sedation were more frequent in Group F during and after the procedure (P < 0.05). CONCLUSIONS: A similar EC50 but more respiratory depression, sedation and PONV were found with fentanyl TCI than with remifentanil TCI.     

Respiratory mechanical properties during fentanyl and alfentanil anaesthesia

The purpose of this study was to assess the effects on respiratory mechanics of fentanyl and alfentanil in 20 subjects to be submitted to coronary artery bypass grafting. Using the end inflation occlusion method (EIOM) we obtained the elastance (E) and resistance (R) of the total respiratory system (_rs), thoracic wall (_w) and lungs (_{L). The total respiratory system was divided into thoracic wall and lungs by using an oesophageal catheter. The data were recorded before, immediately after, and two, five and ten minutes after fentanyl and alfentanil iv bolus, at doses of 30 and 120 μg · kg?I}, respectively. The Ers increased at two, five and ten minutes and the E_L at ten minutes after drug administration. The R_rs,min and R_L,min increased at two, five and ten minutes and the R_L,max at five and ten minutes. Both drugs provoked no change in Ew or Rw. It is concluded that the increases in R_rs.min and R_L.min could be explained by opioid bronchoconstriction. No differences were found between the effects of fentanyl and alfentanil on respiratory mechanics.     

Ventilatory effects of subarachnoid fentanyl in the elderly

Twenty-eight elderly patients scheduled for urological surgery were randomly assigned to receive, in a double-blind study, subarachnoid hyperbaric bupivacaine 15 mg with 50 micrograms (group A, n = 7), 25 micrograms (group B, n = 7), or 12.5 micrograms (group C, n = 7) of fentanyl or 1 ml of saline (group D, n = 7) in a total volume of 4 ml. The pattern of breathing and the ventilatory response to CO2 were studied before and 90, 150 and 480 min after the subarachnoid injection. In group A, mild pruritus and sedation occurred in five patients, while nausea, vomiting and periodic breathing occurred in two. In group B, mild pruritus and sedation were observed in four patients, while nausea and vomiting occurred in two. No significant differences in minute ventilation, respiratory drive and respiratory timing were observed between the groups. Patients receiving fentanyl 50 micrograms showed a percentual change from baseline values as function of time (slope VE/PE'CO2) significantly below baseline at 90 and 150 min (p less than 0.05). However, the baseline values in this group reverted after 480 min. No side effects were observed in groups C or D. It is concluded that subarachnoid fentanyl 50 micrograms can cause an early respiratory depression and its use as a postoperative analgesic should be avoided in the elderly.     

Ketorolac or fentanyl continuous infusion for post-operative analgesia in children undergoing ureteroneocystostomy

Background: Children undergoing ureteroneocystostomy suffer from post‐operative pain due to the surgical incision and bladder spasm. A single‐shot caudal block is a common technique for paediatric analgesia, but a disadvantage is the limitation of a short duration in spite of the additives co‐administered. A few clinical trials have shown that ketorolac provides an effective post‐operative analgesia and reduces the bladder spasms after ureteral implantation in children. We compared the efficacy of a continuous infusion of ketorolac and fentanyl in post‐operative analgesia and bladder spasm in children who underwent ureteroneocystostomy. Methods: Fifty‐two children were allocated to the ketorolac group (Group K, n=26) and fentanyl group (Group F, n=26). After general anaesthesia, a caudal block was performed with 1.5 ml/kg of 0.15% ropivacaine. At the beginning of surgery, an infusion was started after the bolus injection of ketorolac 0.5 mg/kg or fentanyl 1 μg/kg. An infusion device was programmed to deliver ketorolac 83.3 μg/kg/h or fentanyl 0.17 μg/kg/h for 48 h. Results: Two of Group F and three of Group K were excluded from the study. Post‐operative pain scores were similar between the two groups. One of Group K (4%) and seven of Group F (30.4%) experienced bladder spasms. The rescue analgesic requirements were significantly less in Group K. Conclusions: A Continuous infusion of ketorolac provided effective analgesia after operation in children who underwent ureteroneocystostomy as well as a low dosage of fentanyl. Ketorolac was more effective in reducing the frequency of bladder spasms and rescue analgesic requirements.     

Autonomic activity during dexmedetomidine or fentanyl infusion with desflurane anesthesia

Study ObjectiveTo evaluate autonomic activity with dexmedetomidine or fentanyl infusion and desflurane anesthesia during laparoscopic gastric banding.Study DesignRandomized, single-blinded, open-label study.SettingOperating rooms at a university hospital.Subjects40 patients scheduled for laparoscopic gastric banding with a mean body mass index of 50 kg/m².InterventionsPatients received either dexmedetomidine (0.5 μg/kg given intravenously over 10 minutes, 0.4 μg · kg⁻¹ · h⁻¹, n = 20) or fentanyl (0.5 μg · kg⁻¹ bolus, 1 μg · kg⁻¹ · h⁻¹, n = 20) during anesthesia. Response entropy of the electroencephalogram was maintained at 45 ± 5 by adjusting end-tidal desflurane concentration.MeasurementsIn the operating room, blood pressure, heart rate (HR), response entropy, end-tidal desflurane concentration, tone entropy, and power-spectral analysis of HR were measured with the patient awake; 20, 40, and 60 minutes from intubation and the start of drug infusion; and at extubation.Main ResultsThe mean end-tidal desflurane concentration during anesthesia was 4.0% ± 0.6% with dexmedetomidine and 4.1% ± 0.7% with fentanyl, indicating a similar anesthetic requirement in both groups. Autonomic activity, determined by tone entropy and spectral analysis of HR, decreased by 50% during anesthesia in both groups. The dexmedetomidine group showed a greater decrease in sympathovagal balance during anesthesia.ConclusionBoth dexmedetomidine and fentanyl facilitated anesthesia and attenuated autonomic activity. Dexmedetomidine produced a greater decrease in sympathovagal balance than fentanyl.     

EEG-assisted titration of propofol infusion during neuroanesthesia: effect of nitrous oxide

Total intravenous anesthesia (TIVA) with propofol is an alternative to standard techniques for neuroanesthesia. The present study compared the hemodynamic and recovery profiles of 46 neurosurgical patients randomly assigned to one of three different anesthetic treatment groups. Group 1 was anesthetized with a TIVA technique in which propofol was titrated using an EEG-assisted quantification method. Group 2 received a similar propofol-based infusion technique in combination with nitrous oxide. Group 3 (control) received a standard anesthetic technique consisting of thiopental, nitrous oxide, fentanyl, and isoflurane. Significantly less propofol was required in group 2 than in group 1 (7.4 +/- 1.9 vs. 9.0 +/- 1.0 mg/kg/h, respectively). The propofol blood concentration at the first appearance of EEG burst suppression was also higher in group 1 compared to group 2 (5.8 +/- 1.1 vs. 4.8 +/- 0.8 microg/ml). However, 25% of the patients in group 2 were treated for hypotension after induction, compared to none in groups 1 and 3. Hypertensive episodes, on the other hand, were more frequent in groups 1 (43%) and 3 (31%) than in group 2 (12%). Time to awakening was significantly shorter in the control group (6 +/- 6 min) than in groups 1 (14 +/- 10 min) or 2 (12 +/- 16 min). In conclusion, titration of propofol to achieve a burst suppressive EEG pattern resulted in a slower emergence from anesthesia than a standard "balanced" technique. Use of nitrous oxide with propofol produced more hypotension during induction; however, its use improved hemodynamic stability during the maintenance period.