Pharmacokinetics of three doses of epidural ropivacaine during hysterectomy and comparison with bupivacaine.

PURPOSE: Ropivacaine is a new long-acting aminoamide local anaesthetic, structurally related to bupivacaine. The clinical efficacy of 125 mg, 187.5 mg and 250 mg ropivacaine have been reported and compared with 125 mg bupivacaine for epidural analgesia during hysterectomy. In the pharmacokinetic part of this study the objectives were to 1) determine the dose proportionality in the pharmacokinetics of epidural ropivacaine, and 2) compare the pharmacokinetics of 125 mg ropivacaine and 125 mg bupivacaine. METHODS: In a randomized, double-blind controlled study, patients received one of four treatment regimens with ropivacaine (125, 187.5 or 250 mg) or bupivacaine (125 mg) as a 25 ml epidural bolus administered over three minutes. Peripheral venous blood samples were collected over 24 hr for ropivacaine or bupivacaine quantification using gas chromatography with nitrogen sensitive detection. Pharmacokinetic variables were derived from plasma concentration-time curve data. RESULTS: Fifty two women entered the study. Demographic characteristics were similar among groups. Six patients were excluded due to inadequate sensory block or an insufficient number of plasma samples. The peak plasma concentration (Cmax) of ropivacaine and the total area under the plasma concentration-time curve (AUC) increased proportionally with the dose. Apparent plasma clearance (CL) and the terminal half-life (t1/2) were similar in the three ropivacaine groups. When compared with the 125 mg ropivacaine group, the bupivacaine group had a longer terminal half life (P < 0.05). CONCLUSIONS: Epidural ropivacaine displays dose-proportional pharmacokinetic behaviour for doses of 125 mg to 250 mg. Ropivacaine has a shorter terminal half-life than bupivacaine.

A double-blind comparison of ropivacaine 0.5%, 0.75%, 1.0% and bupivacaine 0.5%, injected epidurally, in patients undergoing abdominal hysterectomy.

PURPOSE: Ropivacaine is a new long-acting, injectable local anaesthetic currently undergoing clinical investigation world wide. It is structurally very similar to bupivacaine, but with less potential for central nervous system or cardiac toxicity. The purpose of this double-blind study was: to investigate the dose-response relationship of increasing doses of ropivacaine on the quality of anaesthesia and the duration of both motor and sensory blockade, and to compare these results with an established local anaesthetic, bupivacaine. METHODS: One hundred and twenty five patients were randomly assigned to one of four treatment groups and 116 completed the study. Epidural anaesthesia was established using 25 ml test solution, injected over three minutes following a satisfactory test dose. Sensory onset, spread and duration, using the pin prick method, and motor scores using a modified Bromage scoring system were compared. RESULTS: A dose/response relationship was observed with increasing doses of ropivacaine for all variables tested except analgesia and muscle relaxation (P < 0.01). There were differences in: (i) motor onset (Levels 1 and 2), when ropivacaine 1.0% was compared with ropivacaine 0.75% and 0.5% (P < 0.05); (ii) in sensory duration at all levels except T6 when ropivacaine was compared with ropivacaine 0.5% (P < 0.05); (iii) differences in sensory duration at T12 and S1 when ropivacaine 1.0% was compared with bupivacaine 0.5% (P < 0.05); (iv) differences in motor duration at all levels when ropivacaine 1.0% was compared with ropivacaine 0.5% (P < 0.05). No serious adverse events were reported in this study. CONCLUSION: Increasing doses of ropivacaine were associated with an increased clinical effect. The most consistent differences occurred when ropivacaine 1.0% was compared with 0.5% and the least consistent between ropivacaine 0.5%, 0.75% and bupivacaine 0.5%. The main difference between ropivacaine 1.0% and bupivacaine was in sensory duration. No serious adverse events were reported.

Flexible endoscopic intubation of the neonate.

The development of the ultrathin bronchoscope has provided a means of providing flexible endoscopic intubation for the neonate and small infant. We report our experience of 26 such endoscopic intubations in 23 neonates with birth weights from 1,200 to 4,600 g and post-conceptional ages varying from 31.5 to 60 weeks. The most common indications for the procedure were dysmorphic airways with variable degrees of micrognathia, acquired airway lesions, and severe degrees of hydrocephalus. With the use of the current 2.2 mm and 2.7 mm diameter instruments, it is now possible to utilize this technique with 2.5 mm endotracheal tubes. There were no failed procedures and no evidence of laryngospasm, the most frequent adverse effect being a transient fall in oxygen saturation. The procedure as practiced by experienced individuals is well tolerated and is an important adjunct for intubation of neonates with dysmorphic upper airways or other disorders that prevent adequate visualization of the larynx.

Silicon vidicon spectrometry and its infrared capabilities for solar research.

A rapid-scanning silicon vidicon spectrometer is described; its sensitivity extends from 300 nm to 1080 nm, where even at that wavelength it has enough sensitivity to allow observation under eclipse conditions of a pair of forbidden spectral lines from twelve-times ionized iron that are sensitive indicators of the electron density in the solar corona. Past observational work on these ir lines is reviewed, and our vidicon observations made during the 1973 total solar eclipse are discussed. The vidicon target, the scanning procedure, and the advantages of the spectrometer are described. At the 1973 eclipse, the 1074.7-nm line was detected and an upper limit set for the 1079.8-nm line at a height of 1.4 solar radii. The resultant limit to the ratio of intensities gives electron densities in agreement with those derived from other methods and is consistent with observations made at lower heights; this indicates that the only previous eclipse observation of the ratio at this height was contaminated by scattered light. Our 1973 eclipse observations were limited by the high ambient temperature of the vidicon, by the less-than-optimum match of the focal ratios of the telescope and spectrometer optics, and by problems with the pointing during totality. These difficulties can be overcome, and the silicon vidicon spectrometer will be useful in both eclipse and noneclipse solar observing to map the coronal ir spectrum and also to study the [Fe XIII] ir and interlocking uv lines.