Measurement of spin-correlation parameters ANN, ASS, and ASL at 2.1 GeV in proton-proton elastic scattering.

At the Cooler Synchrotron COSY/Jülich spin-correlation parameters in elastic proton-proton (pp) scattering have been measured with a 2.11 GeV polarized proton beam and a polarized hydrogen atomic beam target. We report results for A(NN), A(SS), and A(SL) for c.m. scattering angles between 30 degrees and 90 degrees. Our data on A(SS)--the first measurement of this observable above 800 MeV--clearly disagrees with predictions of available pp scattering phase-shift solutions while A(NN) and A(SL) are reproduced reasonably well. We show that in the direct reconstruction of the scattering amplitudes from the body of available pp elastic scattering data at 2.1 GeV the number of possible solutions is considerably reduced.

Exclusive measurement of the pp --> pppi(+)pi(-) reaction near threshold.

The pp-->pp pi(+) pi(-) reaction has been measured exclusively near threshold at CELSIUS. The total cross sections are nearly an order of magnitude lower than expected from previous inclusive measurements. The differential cross sections reveal pp-->pp(*)(1440)-->pp sigma = pp(pi(+)pi(-))(I = l = 0) as the dominant process as well as significant contributions from p(*)-->Delta(++)pi(-)-->psigma. The observed anisotropy in the proton angular dependence is consistent with heavy-meson exchange. In the invariant mass spectra, no narrow structures of statistical relevance (3sigma) are found.

Excitation functions of the analyzing power in pp--> scattering from 0.45 to 2.5 GeV

Excitation functions A(N)(p(p),Theta(c.m.)) of the analyzing power in pp--> elastic scattering have been measured with a polarized atomic hydrogen target for projectile momenta p(p) between 1000 and 3300 MeV/ c. The experiment was performed for scattering angles 30 degrees

Postal survey on the long-term use of neuromuscular block in the intensive care.

OBJECTIVE: To assess the long-term use of neuromuscular blocking (NMB) agents in intensive care, especially with reference to the potential problems of the long-term use of NMB drugs in the intensive care unit (ICU). METHOD: A postal survey questionnaire was sent to 409 ICUs in Great Britain. RESULTS: Two hundred thirty-eight completed questionnaires were returned and analysed. Most ICUs were anaesthetist-led (85.8%) with only five ICUs being staffed by full-time intensivists. Facilitation of mechanical ventilation and increased intracranial pressure were the main indications for the prolonged use of neuromuscular blockade. Atracurium and vecuronium (83%) were administered most commonly by bolus alone (13.8%), bolus followed by continuous infusion (23.9%) or continuous infusion only (60.9%). The most frequently cited criteria for the use of either vecuronium or stracurium were their pharmacokinetics and haemodynamic stability. Neuromuscular block was most commonly monitored clinically (91.7%), with only 8.3% of the responders using a peripheral nerve stimulator. All responders indicated the concomitant use of sedatives (propofol/midazolam alone or in combination in 89.4% of responders) and/or opioids (morphine, fentanyl or alfentanil in 74.8% of respondents) with muscle relaxants. CONCLUSION: Most responders agreed that while neuromuscular block in the ICU population may provide advantages, it cannot be considered benign. Indeed, a great majority consider that NMB agents should be used only as a last option and -for as short a period as possible.

Anaesthetic implications of aortic stent surgery.

We present a case of abdominal aortic aneurysm repair using a new technique of aortic stenting and discuss the anaesthetic technique used and the perioperative advantages of the technique.

Inhibition by halothane of potassium-stimulated acetylcholine release from rat cortical slices.

1. Cholinergic neurones in the basal forebrain are linked to cortical activation and arousal. 2. The present study was designed to examine the hypothesis that clinically relevant doses of halothane (0.1 to 5%) would significantly reduce depolarization-evoked acetylcholine (ACh) release from rat cortical slices. 3. ACh release was measured from rat cortical slices by a chemiluminescent technique. 4. Depolarization-evoked ACh release was inhibited significantly by halothane with an IC50 of 0.38%. This value equates to 0.3 MAC (the minimum alveolar concentration at which no movement occurs to a standard surgical stimulus in 50% of subjects) for the rat. 5. The potent effect of halothane on ACh release suggests that this mechanism may be a target for the action of volatile anaesthetic agents. This in vitro effect on ACh release is consistent with effects of halothane reported in vivo.

Pharmacokinetic drug interactions with gastrointestinal motility modifying agents.

Drugs may affect gastrointestinal motility and, therefore, absorption of other concomitantly administered drugs. Gastrointestinal prokinetic agents increase the rate of gastric emptying and also upper intestinal motility. These effects would be expected to increase the initial rate of absorption of orally administered drugs, but reduce total bioavailability of the agents. Metoclopramide has been shown to increase the rate of absorption of several classes of drug, reflected by reduced time taken to achieve maximal plasma concentration (tmax) and increased maximal plasma concentration (Cmax). However, the effect of these agents on the area under the plasma concentration-time curve from zero to infinity (AUC0-infinity), when measured, is not consistent. Cisapride and domperidone appear to have similar effects, but there are relatively less data available regarding these products. Opioids may delay gastric emptying considerably, an effect which will often have significant clinical and therapeutic implications. Most of the data confirming this observation concern oral analgesics, but the effect should be considered when prescribing any oral medication. Drugs with anticholinergic or sympathomimetic activity are likely to have a similar effect and this is confirmed, in the main, by the limited data available. Although many effects reported in the literature are of limited clinical importance, they may be significant when prescribing a drug with a narrow therapeutic index, especially if it is absorbed poorly.

Volatile anesthetic agents inhibit choline uptake into rat synaptosomes.

BACKGROUND: Acetylcholine is an excitatory neurotransmitter associated with the maintenance of consciousness. Choline uptake is the rate-limiting step in acetylcholine synthesis and may be a target for the action of volatile anesthetic agents. METHODS: [Methyl-3H]choline uptake was investigated using rat cortical synaptosomes. The preparation was exposed to air, as control, or equipotent partial pressures (2.4 rat MAC) of enflurane, halothane or isoflurane. In addition, the dose-response relation for halothane on [methyl-3H]choline uptake was studied. RESULTS: The maximum rate of uptake was reduced significantly by 24% in the presence of enflurane (5.5%, 2.4 rat MAC) and isoflurane (3.5%, 2.4 rat MAC) and by 38% in the presence of halothane (3%, 2.4 rat MAC) with no change in Michaelis constant in the presence of each agent. A linear relation between the inhibition of [methyl-3H]choline uptake and the concentration of halothane was observed up to 3% halothane above which there was no further inhibition. The concentration of halothane resulting in half-maximum inhibition of total choline uptake was 1.5%. CONCLUSIONS: Noncompetitive inhibition of [methyl-3H]choline uptake by volatile anesthetic agents has been demonstrated in the in vitro synaptosome preparation. If present in vivo reduction in anesthetic-sensitive choline uptake may reduce the presynaptic availability of acetylcholine and hence contribute to the process of anesthesia.

Acid aspiration prophylaxis in 202 obstetric anaesthetic units in the UK.

A postal survey of obstetric anaesthetic units in the UK was conducted by questionnaire to gain information about current acid aspiration prophylaxis. Information regarding the delivery rate and the caesarean section rate under regional techniques was also requested. Replies were received from 202 obstetric anaesthetic units in the UK, a 75% response rate. The results are compared to similar surveys carried out in 1984 and 1988. Sodium citrate and the H(2) antagonist ranitidine remain the drugs most commonly used for acid aspiration prophylaxis. However, the number of departments carrying out routine prophylaxis for patients in active labour has fallen from 75% in 1988 to 57% in the current survey.

Choline acetyltransferase activity of rat synaptosomes is sensitive to enflurane, but not halothane or isoflurane.

We have examined the activity of choline acetyltransferase (ChAT) in rat cortical synaptosomes in the presence of three volatile anaesthetic agents: enflurane, halothane and isoflurane. The Michaelis constant Km, for choline was reduced significantly (P = 0.012) in the presence of 6.5% enflurane (3 rat MAC) compared with control samples exposed to carrier air only, while maximum reaction velocity (Vmax) remained unaltered. The reduction in Km was also significant at enflurane concentrations of 4.4% (2 rat MAC) (P = 0.043) and 2.2% (1 rat MAC) (P = 0.043). Halothane 3% (2.5 rat MAC) and 4.5% isoflurane (3 rat MAC) had no effect on either kinetic property. If present in vivo, an enflurane-induced alteration in acetylcholine metabolism, through modified ChAT, may contribute to the convulsive properties of this anaesthetic.

The stability of the tibio-fibular syndesmosis following rigid internal fixation for type C malleolar fractures: an experimental and clinical study.

In 5 cadavers, type C malleolar fractures of the pronation-eversion rotation type, were produced. The stability of the ankle mortice under stress was tested before and after rigid internal fixation of the fracture in the fibula. The intact interosseous membrane above the fracture in combination with the internal fixation of the fibula was sufficient to keep the lateral malleolus in place. A clinical series of 8 equivalent fractures treated with rigid internal fixation without suture of the syndesmodesis was collected and evaluated clinically and radiologically 3 years after the injury. None of the patients had significant complaints and all ankle joints were stable.

The 99Tcm-Sn-polyphosphate scintimetric time course of human tibial fractures with delayed union or pseudarthrosis.

In 17 fractures of the human tibia, showing delayed union or the development of pseudarthrosis, the amount of callus formed was assessed monthly by scintimetry following intravenous administration of 99Tcm-Sn-polyphosphate. The mean scintimetric time course of the group of fractures with the atrophic type of delayed union was statistically significantly lower between the fourth and fourteenth week than that of fractures with uncomplicated healing. Nearly two-thirds of the fractures showed scintimetric ratios below the lower normal confidence limit (2 s.d.). The mean scintimetric time course of the fractures with the hypertrophic type of delayed union showed a normal scintimetric time course up to the eighth week, but from the tenth week a statistically significantly higher scintimetric ratio than the fractures with uncomplicated healing was found. The scintimetric ratio after the fourteenth week was below 2.5 for fractures with the atrophic type of delayed union, and above 2.5 for fractures with the hypertrophic type. The scintimetric time course of fractures which developed pseudarthroses was not different from those showing delayed union. The scintimetric method allows early detection of a pathological course of fracture healing. It supplies information about the functional state of the healing process and serves as an indicator of the correct treatment.

Fractures of the shaft of the tibia treated with AO-compression osteosynthesis.

Ninety-six displaced fractures of the shaft of the tibia in a series of 162 consecutive fractures were treated by AO internal fixation. Forty per cent were open fractures, of which 93 per cent received prophylactic treatment with antibiotics at the time of admission. The average time between the accident and the operation was 10 hours in closed fractures and 5 hours in open fractures. All cases were operated on by senior surgeons. The infection rate was 5.3 per cent in closed fractures, and 0 in open fractures. The average stay in hospital was 13 days. More than 90 per cent returned to work within 6 months after the accident. No case of pseudarthrosis or re-fracture was seen. The median time to final review was 36 months. Rigid internal fixation is advocated for all displaced fractures of the shaft of the tibia and is advocated as an urgent procedure especially in open fractures, and should be performed by experienced surgeons only. Rigid internal fixation appears to provide effective prophylaxis against secondary soft-tissue damage and limits the consequences of the initial soft-tissue damage.

Malleolar fractures treated with rigid internal fixation and immediate mobilization.

Twenty=eight consecutive patients with displaced malleolar fractures were treated with anatomically exact open reduction, rigid internal fixation and immediate postoperative exercises, following the principles of the Swiss ASIF group. There were no operative or postoperative complications. One patient had a minor abscess over a loosened screw, while 1 patient developed pes equinus that required treatment. AT follow-up 2 to 12 months after the operation, 25 patients were walking normally. The movements of the ankle joint were excellent or good in 25 patients. The method is recommended.

Bone healing in rabbits after compression osteosynthesis, studied by Tc-99m(Sn)polyphosphate scintimetry and autoradiography.

The purpose of the present study was to determine the scintimetric time course (STC) for Tc-99m(Sn) polyphosphate in rabbit tibias after various osteosynthetic procedures, and to correlate the findings with those from serial radiographs and with autoradiographic and histologic evaluation of the bone. The STC was similar for all treatment groups, with a peak value within the second week after surgery. Significantly different levels of the STC were found after subperiosteal exploration, plate insertion, osteotomy and compression plating, or osteotomy and medullary nailing. The radiological, autoradiographic, and histological findings revealed that Tc-99m scintimetry monitors callus formation. The STC thus appears to be a valuable tool for the quantitative study of bone healing.