The use of propofol and alfentanil by infusion in military anaesthesia

A total intravenous technique using propofol and alfentanil was used successfully in four battlefield casualties treated at a British Military Field Hospital during the recent Gulf conflict. All patients made a rapid recovery of adequate quality for prompt evacuation. We believe that the use of propofol and alfentanil as an induction and maintenance regimen for military anaesthesia merits further evaluation and comparison with established techniques.     

Intubating conditions provided by propofol and alfentanil - acceptable, but not ideal

Background: The use of muscle relaxants to facilitate intubation is associated with several side effects regardless of whether depolarizing or non-depolarizing drugs are used. In the present study we compared the intubating conditions, haemodynamic responses and changes in oxygen saturation following induction with alfentanil and propofol or alfentanil, thiopental and suxamethonium.
Methods: Eighty patients (ASA I or II) were in a double-blind manner assigned to receive either of the two induction methods. Intubating conditions were assessed on the basis of jaw relaxation, ease of insertion of the endotracheal tube and coughing on intubation. Heart rate, systolic arterial pressure and oxygen saturation were monitored throughout the procedure.
Results: The use of alfentanil and propofol resulted in significantly lower scored intubation points. Systolic arterial pressure decreased and heart rate increased significantly in the alfentanil-thiopental-suxamethonium group as compared to the alfentanil-propofol group. There were no significant changes in oxygen saturation.
Conclusion: The results show that propofol and alfentanil in combination provides haemodynamic stability and unaltered oxygen saturation but less optimal intubating conditions.     

Alfentanil infusion for sedation in infants and small children during cardiac catheterization

We have analyzed several sedation techniques for paediatric cardiac catheterization which offer stable conditions for a few hours investigation, and maintain spontaneous breathing. In the present study, after premedication with oral flunitrazepam 0.1 mg.kg-1, 14 children aged 1-17 mo were sedated with an individually titrated alfentanil infusion. Every patient was sedated to a level which produced no reaction to pain or any discomfort. The induction dose and the maintenance requirement of alfentanil were 24 +/- 8 micrograms.kg-1 and 32 +/- 8 micrograms.kg-1.hr-1 (mean +/- SD), respectively. These doses were less in cyanotic than in acyanotic patients: 21 +/- 6 vs 28 +/- 8 micrograms.kg-1 and 29 +/- 10 vs 34 +/- 3 micrograms.kg-1.hr-1, respectively (P less than 0.05). The mean plasma concentration of alfentanil during maintenance of sedation was 79 +/- 23 ng.ml-1. Ventilation of two children was assisted for a short time after an incremental bolus of alfentanil. It is concluded that an alfentanil infusion technique with close monitoring of breathing is a practical sedation method for paediatric cardiac catheterization.     

Closed loop control of anaesthesia: an assessment of the bispectral index as the target of control

We investigated the performance of a closed-loop system for administration of general anaesthesia, using the bispectral index as a target for control. One hundred patients undergoing gynaecological or general surgery were studied. In 60 patients, anaesthesia was maintained by intravenous infusion of a propofol/alfentanil mixture. In 40, an isoflurane/nitrous oxide based technique was used. For each technique, patients were randomly allocated to receive either closed-loop or manually controlled administration of the relevant agents (propofol/alfentanil or isoflurane), with an intra-operative target bispectral index of 50 in all cases. Closed-loop and manually controlled administration of anaesthesia resulted in similar intra-operative conditions and initial recovery characteristics. During maintenance of anaesthesia, cardiovascular and electro-encephalographic variables did not differ between closed-loop and manual control groups and deviation of bispectral index from the target value was similar. Intra-operative concentrations of propofol, alfentanil and isoflurane were within normal clinical ranges. Episodes of light anaesthesia were more common in the closed-loop group for patients receiving propofol/alfentanil anaesthesia and in the manual group for patients receiving isoflurane/nitrous oxide anaesthesia. Convenience aside, the closed-loop system showed no clinical advantage over conventional, manually adjusted techniques of anaesthetic administration.     

Electroencephalogram spectral edge frequency,lower esophageal contractility,and autonomic responsiveness during general anesthesia

Both the electroencephalogram (EEG) spectral edge frequency (SEF) and lower esophageal contractility (LEC) indices have been reported to be useful indicators of anesthetic depth. We designed a prospective study to evaluate the relationship between changes in these two variables and objective measurements of physiologic responsiveness to surgical stress (i.e., changes in hemódynamic variables and plasma levels of norepinephrine, epinephrine, total catecholamines, and vasopressin). Eighty-nine consenting adult males undergoing radical prostatectomy procedures under a standardized general anesthetic technique were studied according to a randomized, single-blinded protocol. General anesthesia was induced with 30 µg/kg intravenous (IV) alfentanil, 2.5 mg/kg IV thiopental, and 0.1 mg/kg IV vecuronium, and subsequently maintained with 0.5 µg/kg/min alfentanil, nitrous oxide (N₂O) 67% in oxygen, and 0.8 µg/kg/min vecuronium. Following retropubic dissection, 81 patients (92%) manifested acute hypertensive responses, with mean arterial pressure increasing from 90±14 to 122±14 mm Hg (mean ± SD). This acute hypertensive response was treated with one of three different treatment modalities (20 to 60 µg/kg IV alfentanil, 0.5 to 2.0% inspired isoflurane, or 0.05 to 0.15 mg/kg IV trimethaphan) to return the mean arterial pressure to within 10% of the preincisional (baseline) value within 5 to 10 minutes. Although the mean arterial pressure, heart rate, and plasma levels of catecholamines and vasopressin significantly increased following the surgical stimulus, and decreased after adjunctive therapy, the EEG-SEF and LEC index (LECI) values did not significantly change during these study intervals. Furthermore, using a logistic regression analysis, we observed that preincision EEG-SEF and LECI values could not predict whether patients would manifest a hypertensive response. Therefore, the EEG-SEF and LECI were unreliable indicators of anesthetic depth.This study was supported in part by a grant from the Ambulatory Anesthesia Research Foundation, Los Altos, CA. (Dr White is a member of the Board of Directors.)The authors would like to thank Dan Kuni (Baxter Healthcare) for his assistance in obtaining the equipment used to perform the study; Vinod Kothapa, MD, for his valuable assistance with the anesthetic management of the study patients; Alex K. Mills, MD, for his assistance with the EEG interpretation; and Steven A. Bai, PhD, for his assistance with the plasma alfentanil analyses.     

静脉注射利多卡因对丙泊酚麻醉下阿芬太尼抑制人流手术患者体动反应的半数有效剂量的影响

目的 研究静脉注射利多卡因对丙泊酚麻醉下阿芬太尼抑制人流手术患者体动反应的半数有效剂量（ED₅₀）的影响。方法 择期人工流产手术患者，年龄18~40岁，美国麻醉医师协会分级I~II级。随机分成2组，利多卡因联合阿芬太尼组（LA组）与阿芬太尼组（A组）。LA组患者静脉注射利多卡因1.0 mg·kg^-1后，缓慢注射丙泊酚2.0 mg·kg^-1及阿芬太尼（初始剂量为15.5 μg·kg^-1），A组患者则静脉注射0.1 mL·kg^-1生理盐水后，再依次缓慢注射丙泊酚2.0 mg·kg^-1与阿芬太尼。待患者意识消失后，消毒铺巾，观察患者置入宫颈探条的体动反应。采用序贯法计算阿芬太尼的剂量，若在置入宫腔探条时，发生体动阳性反应，则下一例患者剂量增加20%，反之则剂量降低20%。直至出现 ≥ 6个阳性反应和阴性反应的交替点，结束试验。采用概率单位回归分析法计算阿芬太尼抑制人流患者体动反应的ED₅₀、95%有效剂量（ED₉₅）及其95%可信区间（CI），记录术中生命体征，静脉注射痛，术后10 min、术后30 min、出院时疼痛评分及不良反应等指标。结果 LA组ED₅₀为6.55 μg·kg^-1（95%CI，2.10~8.07 μg·kg^-1），A组ED₅₀为8.24 μg·kg^-1（95%CI，6.75~9.75 μg·kg^-1），2组阿芬太尼的ED₅₀有差异；与A组比较，LA组术后10 min、术后30 min、出院时疼痛评分更低，差异有统计学意义（P<0.000 1或P<0.05）；LA组静脉注射痛发生率下降（减少44.2%），差异有统计学意义（P<0.01）；2组呼吸抑制发生例数、清醒时间与恶心呕吐等比较差异无统计学意义。结论 静脉注射利多卡因可显著降低阿芬太尼用于人流手术的ED₅₀，减少静脉注射痛发生率，缓解术后短期急性疼痛。     

ECG T-wave amplitude changes during thiopentone induction with or without alfentanil

The T-wave amplitude of ECG is thought to reflect the sympathetic tone of the heart but anaesthesia studies on this topic are rare. Haemodynamic and ECG T-wave amplitude changes were studied during induction of anaesthesia in 24 ASA I-II patients. Twelve patients were given alfentanil 30 μg kg^-1 at induction while physiologic saline was given to the rest (control). Thiopentone was then administered at the rate of 5 mg s^-1 until eyelash reflex disappeared. Vecuronium 0.1 mg kg^-1 was given thereafter. No anticholinergics were used. The lungs were ventilated with 40% oxygen in air. Haemodynamic parametres and T-wave amplitude were measured before induction, before intubation, 30 s, 3 min and 5 min after intubation. A significandy higher amount of thiopentone was needed to abolish the eyelash reflex in the control group than in the alfentanil group ( P <0.001). There were no changes in heart rate (HR) in the alfentanil group during the trial. Systolic and diastolic arterial pressures (SAP and DAP) were continuously below the preinduction levels in the alfentanil group. After baseline HR, SAP and DAP were significantly higher in the control group than in the alfentanil group at each data point. T-wave amplitude flattened significantly ( P <0.001) after intubation in the control group while no significant changes were seen in the alfentanil group. T-wave flattening correlated to the increases in HR ( P <0.01) and SAP ( P <0.01). Three control patients with flattened T-wave had a transient bigeminia period after intubation. It is concluded that ECG T-wave amplitude flattening was associated with pressure and heart rate response to laryngoscopy and intubation. Alfentanil blunted these responses and prevented T-wave changes after intubation.     

Comparison of alfetanil and ketamine in combination with propofol for patient-controlled sedation during fiberoptic bronchoscopy

BACKGROUND: During fiberoptic bronchoscopy, propofol, ketamine, benzodiazepines, and opiates are most commonly used, alone or in combination for sedation. The aim of this study was to compare the clinical efficacy of propofol/ketamine with propofol/alfentanil for patient-controlled sedation (PCS) during fiberoptic bronchoscopy. METHOD: Patients undergoing fiberoptic bronchoscopy were randomly assigned to receive either propofol/alfentanil (PA group; n = 138) or propofol/ketamine (PK group; n = 138) via a patient-controlled analgesia (PCA) device for sedation and analgesia. Changes in blood pressure, heart rate (HR), and oxygen saturation were monitored. Degree of patient and bronchoscopist satisfaction was evaluated using a 10-cm visual analog scale (VAS) (0 = extremely uncomfortable to 10 = extremely comfortable). RESULTS: After sedation, systolic arterial pressure (SAP) decreased in the PA group, but SAP was stable in the PK group. Compared with values immediately before starting bronchoscopy, SAP and HR increased during the procedure in both groups (P < 0.05). Patients in the PK group showed more satisfaction [(9.5 (6-10) vs. 9.0 (6-10)), P < 0.05] and amnesia (82% vs. 61%, P < 0.01). Despite these differences, the majority (greater than 90%) of the patients in both groups stated that they were comfortable during the procedure. CONCLUSION: Our results show that although both techniques proved effective for sedation in patients undergoing fiberoptic bronchoscopy, ketamine is superior to alfentanil when used in combination with propofol because of the high patient satisfaction and amnesia.