An interchangeable Mapleson A-E breathing system is practical and cost effective.

BACKGROUND: In locations where oxygen and anesthesia gas supplies are limited, and where circle systems are not practical, means to reduce fresh gas flow during maintenance of inhalational anesthesia are of potential value. We investigated whether a common transport breathing apparatus could be modified to allow interchange between Mapleson D (Map-D) and Mapleson A (Map A) configurations. METHODS: A common Map-D transport system was converted to a Map-A system by switching positions of the exhaust valve and the elbow connector where fresh gas is delivered; these two breathing systems were compared in this study. The key question was whether rebreathing of CO2 could be eliminated at a lower fresh gas flow rate (FGF) with the Map-A design. A structured protocol was followed. RESULTS: A mean decrease in FGF of 2.8 l/min was seen with the Map-A apparatus when compared with the Map-D (P=0.003). With no significant differences in physiologic or anesthetic variables, FGF/V(E) was significantly lower with the Mapleson A configuration than with the Mapleson D system design (1.1 vs. 1.8; P=0.007). The extent to which FGF could be lowered when switching between Mapleson D and A systems correlated strongly with the patients' respiratory rate while under anesthesia (r=0.45, P<0.01). CONCLUSIONS: Cost and resource savings can be realized through the use of a breathing system modification that achieves appropriate ventilation at lower fresh gas flows.

Correction of intraoperative coagulopathy in a patient with neurofibromatosis type I with intravenous desmopressin (DDAVP).

A patient with the genetic condition neurofibromatosis type I and no known coagulopathy undergoing cesarean delivery, had diffuse uterine and surgical site bleeding that was not correctable by oxytocin, methylergonovine and PGF2 alpha. Despite good uterine tone, hemorrhage continued from the uterus and the surrounding tissues, persisting even after surgical ligation of the uterine arteries. With no change in her condition, which was behaving clinically as a coagulopathy, an infusion of desmopressin acetate (DDAVP) was begun. The patient's bleeding promptly resolved shortly after infusion of this agent. A review of relevant literature suggests that platelet reactivity of patients with neurofibromatosis type 1 is attenuated in some in vitro conditions. Thus, there may be some theoretical basis for using DDAVP in patients with neurofibromatosis type 1 who have bleeding problems with no other known source, such as in the case presented here.

Heme oxygenase type 2 modulates behavioral and molecular changes during chronic exposure to morphine.

The heme oxygenase (HO) enzyme system has been shown to participate in nociceptive signaling in a number of different models of pain. In these experiments we investigated the role of the HO type 2 (HO-2) isozyme in tolerance to the analgesic effects of morphine, and the hyperalgesia and allodynia which are measurable upon cessation of administration. Wild type C57Bl/6 wild type mice or HO-2 null mutants in that background strain were treated with morphine for 5 days. The morphine administration protocol consisted of either twice daily repeated s.c. boluses of 15 mg/kg or s.c. implantation of a morphine pellet. At the end of the treatment period wild type mice treated by either protocol exhibited tolerance, but the HO-2 null mutants did not. The HO-2 null mutants also exhibited less mechanical allodynia following cessation of morphine administration, though only modest differences in thermal hyperalgesia were noted. There was no correlation between the degree of tolerance obtained in the bolus and pellet protocols and the degree of hyperalgesia and allodynia observed after cessation of morphine administration in the wild type mice. Our final experiments analyzed increases in expression of mRNA for nitric oxide synthase type 1, N-methyl-D-aspartate (NMDA) receptor NMDAR1 subunit and prodynorphin in spinal cord tissue. In pellet-treated mice two- to three-fold increases were observed in the abundance of these species, but very little change was observed in the null-mutant mice. Taken together our results indicate that HO-2 participates in the acquisition of opioid tolerance, the expression of mechanical allodynia after cessation of opioid administration and in gene regulation occurring in the setting of treatment with morphine. Furthermore, these studies suggest that the mechanisms underlying analgesic tolerance and opioid-induced hypersensitivity are at least somewhat distinct.

A comparison of the onset and clinical duration of high doses of cisatracurium and rocuronium.

STUDY OBJECTIVE: To determine the onset and clinical duration of cisatracurium and rocuronium in equipotent doses in balanced opioid/isoflurane anesthesia. DESIGN: Randomized, controlled study. SETTING: University hospital. PATIENTS: 40 healthy patients scheduled for elective surgery. INTERVENTIONS: Patients underwent anesthesia induction with thiopental or propofol with a cisatracurium intubating dose of either 0.15 or 0.2 mg/kg or a rocuronium dose of either 0.9 or 1.2 mg/kg. These doses correspond to three and four times the ED95 dose. MEASUREMENTS AND MAIN RESULTS: The onset time and time to 25% recovery of baseline first twitch in a train-of-four were determined using an accelerometric sensor. Rocuronium had a faster onset time that cisatracurium at equipotent doses (3 x ED95: 134 vs. 220 sec respectively, and at 4 x ED95: 95 vs. 162 sec). Recovery tended to be faster, but not statistically different for cisatracurium compared to rocuronium. CONCLUSIONS: With equipotent intubating doses of rocuronium and cisatracurium, rocuronium produces a more rapid onset of muscle relaxation. The data suggest a tendency toward more rapid clinical recovery of cisatracurium compared to equipotent doses of rocuronium, although these differences were not statistically significant.

The chromosomes of Leishmania.

Chromosome size polymorphisms occur in Leishmania such that each strain of a given species has a distinctive molecular karyotype. Despite this variability, the chromosomal similarities among closely related strains of Leishmania are sufficiently characteristic to permit classification of unidentified clinical isolates. Mechanisms generating chromosome size polymorphisms are related to chromosomal evolution. In this review, Geoffrey Lighthall and Suzanne Giannini explain that the chromosomal profiles of members of different species may be diverging from a conserved 'consensus' karyotype at different rates, and present a current understanding of the genomic organization of Leishmania with emphasis on chromosomal elements.