Cephalad Movement of Morphine and Fentanyl in Humans after Intrathecal Injection

Background: Despite decades of use, controversy remains regarding the extent and time course of cephalad spread of opioids in cerebrospinal fluid (CSF) after intrathecal injection. The purpose of this study was to examine differences between two often used opioids, morphine and fentanyl, in distribution in the CSF after intrathecal injection.

Methods: Eight healthy volunteers received intrathecal injection of morphine (50 [mu]g) plus fentanyl (50 [mu]g) at a lower lumbar interspace. CSF was sampled through a needle in an upper lumbar interspace for 60-120 min. At the end of this time, a sample was taken from the lower lumbar needle, and both needles were withdrawn. CSF volume was determined by magnetic resonance imaging. Pharmacokinetic modeling was performed with NONMEM.

Results: Morphine and fentanyl peaked in CSF at the cephalad needle at similar times (41 +/- 13 min for fentanyl, 57 +/- 12 min for morphine). The ratio of morphine to fentanyl in CSF at the cephalad needle increased with time, surpassing 2:1 by 36 min and 4:1 by 103 min. CSF concentrations did not correlate with weight, height, or lumbosacral CSF volume. The concentrations of morphine and fentanyl at both sampling sites were well described by a simple pharmacokinetic model. The individual model parameters did not correlate with the distance between the needles, CSF volume, patient height, or patient weight.     

Auricular Acupressure as a Treatment for Anxiety in Prehospital Transport Settings

Background: Auricular acupuncture at the relaxation point has been previously shown to be an effective treatment for anxiety in the preoperative setting. The purpose of this prospective, randomized, blinded study was to determine whether auricular acupressure can reduce stress and anxiety during ambulance transport.

Methods: Patients who required ambulance transport secondary to medical conditions were randomized to receive auricular acupressure at the relaxation point (n = 17) or at a sham point (n = 19). A visual analog scale was used to assess state anxiety as well as patient anticipation of hospital medical treatment (estimated waiting period for treatment, anticipated pain during treatment, attitude toward the physicians, and treatment outcomes). These variables were assessed at baseline and on arrival to the hospital.

Results: Patients in the relaxation group reported significantly less anxiety than patients in the sham group on arrival to the hospital (visual analog scale mean +/- SD: 37.6 +/- 20.6 to 12.4 +/- 7.8 mm vs. 42.5 +/- 29.9 to 46.7 +/- 25.9 mm, respectively;P = 0.002). Similarly, patient perception of pain during treatment (mean visual analog scale +/- SD: 32.7 +/- 27.7 to 14.5 +/- 8.1 mm vs. 17.2 +/- 26.1 to 28.8 +/- 21.9 mm, respectively;P = 0.006) and treatment outcomes of their illnesses (mean visual analog scale +/- SD: 46.7 +/- 29.4 to 19.1 +/- 10.4 mm vs. 35.0 +/- 25.7 to 31.5 +/- 20.5 mm, respectively;P = 0.014) were significantly more positive in the relaxation group than in the sham group. No differences were found in the other variables assessed.     

Melatonin‐evoked potentiation of the juvenile rat tail artery neurogenic reactivity depends on degree of the change in the reactivity

Aim: Dependence of the melatonin‐evoked potentiation of the rat tail artery neurogenic reactivity on degree of the change in the reactivity was studied. Method: Electrical field stimulation‐evoked contractile response of the juvenile rat tail artery segment under isometric conditions was recorded. 0.1 μm melatonin was administered after the change in the response produced both spontaneously and by acidification (pH 6.6) or alkalinization (pH 7.8) of the solution. Results: During the course of experiment, the contraction force continuously declined, being reduced by 12 ± 5, 24 ± 7 and 32 ± 6% at 20, 70, and 170 min after beginning of experiment, respectively. Melatonin applied at these time points increased the contraction by 20 ± 5, 41 ± 10, and 48 ± 8%, respectively, relative to control. This increase in potentiating effect of melatonin during the course of experiment was not because of sensitization of the segment to the hormone. Acidosis‐induced considerable decline in neurogenic contraction was counteracted by melatonin, while after alkalosis‐induced augmentation in the contraction the hormone was not effective. Melatonin increased the artery response to 0.1 μm noradrenaline. Conclusion: These data suggest that melatonin can restore an attenuated neurogenic reactivity of the juvenile rat tail artery. The effect is more pronounced with further decrease in reactivity and might be due to a change in sensitivity of the post‐junctional membrane to noradrenaline.