Evaluation of oesophageal pulse oximetry in patients undergoing cardiothoracic surgery.

Pulse oximetry probes placed peripherally may fail to give accurate values of blood oxygen saturation when the peripheral circulation is poor. Because central blood flow may be preferentially preserved, we investigated the oesophagus as an alternative monitoring site. A reflectance blood oxygen saturation probe was developed and evaluated in 49 patients undergoing cardiothoracic surgery. The oesophageal pulse oximeter results were in good agreement with oxygen saturation measurements obtained by a blood gas analyser, a CO-oximeter and a commercial finger pulse oximeter. The median (IQR [range]) difference between the oesophageal oxygen saturation results and those from blood gas analysis were 0.00 (-0.30 to 0.30 [-4.47 to 2.60]), and between the oesophageal oxygen saturation results and those from CO-oximetry were 0.75 (0.30 to 1.20 [-1.80 to 1.80]). Bland-Altman analysis showed that the bias and the limits of agreement between the oesophageal and finger pulse oximeters were -0.3% and -3.3 to 2.7%, respectively. In five (10.2%) patients, the finger pulse oximeter failed for at least 10 min, whereas the oesophageal readings remained reliable. The results suggest that the oesophagus may be used as an alternative monitoring site for pulse oximetry even in patients with compromised peripheral perfusion.

Temperature limit values for gripping cold surfaces.

OBJECTIVES: At the request of the European Commission and in the framework of the European Machinery Directive, research was conducted jointly in five different laboratories to develop specifications for surface temperature limit values for the gripping and handling of cold items. METHODS: Four hundred and fourteen experiments were run where male and female subjects were invited to grip for up to 20 min cold bars of different contact coefficients, i.e. polished wood, nylon, stone, steel and aluminium. The air temperature and the bars' initial surface temperatures ranged between 0 and -30 degrees C for the various experiments. While gripping the bars, either only the hand or the whole body was exposed to cold. RESULTS: The data were used to develop a prediction formula and a graph of the surface temperature limit values in order for the skin contact temperature not to reach <15 degrees C. This duration is shown to offer a significant degree of safety with respect to the minimal surface temperature spontaneously tolerated by the subjects. CONCLUSIONS: Experiments and modelling must be pursued to extend these data to other conditions of exposure.

Dental nerve blocks. Toothache remedies for the acute-care setting.

Ideally, tooth pain is managed by a competent dentist, who can provide definitive care. However, timely access to such care may not be available late at night, on weekends, or in rural practice settings. This article introduces primary care physicians to dental nerve blocks that can be learned without extensive training and use in the acute-care setting to provide temporary relief of oral, dental, and facial pain.

Prodrugs. Part 3. 2-Formylphenyl esters of indomethacin, ketoprofen and ibuprofen and 6-substituted 2-formyl and 2-acylphenyl esters of aspirin.

The synthesis and study of a novel series of potential prodrugs of indomethacin, ketoprofen, ibuprofen and aspirin are reported. 2-Formylphenyl esters of the NSAIDs, together with two 6-substituted 2-formyl and two 2-acylphenyl aspirins and 4-formylphenyl indomethacin, have been prepared. A study of their alkaline and neutral hydrolysis shows that these compounds, with the exception of 2-acetylphenyl aspirin, act as true prodrugs of the NSAIDs, giving the NSAID and acylphenol. The rates of hydrolysis and activation parameters indicate that the 2-acylphenyl esters employ an intramolecular catalytic route. The 2-formylphenyl esters were more potent as anti-inflammatory agents than the parent compounds in the carragheenan-induced paw oedema test.

Recent changes in delivery site of low-birth-weight infants in Washington: impact on birth weight-specific mortality.

OBJECTIVES: Our purpose was to ascertain whether the proportion of low-birth-weight infants delivered in Washington at tertiary hospitals changed between 1980 and 1991 and whether mortality differed by level of birth hospital. STUDY DESIGN: A retrospective cohort study was performed of 500 to 2499 gm infants born to Washington residents between 1980 and 1991 (n = 43,228). RESULTS: Overall, the percentage of low-birth-weight infants born at tertiary centers rose from 1980 to 1982 through 1986 to 1988 and subsequently declined significantly. Among infants weighing < 2000 gm nontertiary delivery was associated with greater potentially preventable mortality (500 to 999 gm, relative risk 1.5, 95% confidence interval 1.3 to 1.8; 1000 to 1499 gm, relative risk 2.1, 95% confidence interval 1.3 to 3.3; 1500 to 1999 gm, relative risk 1.6, 95% confidence interval 1.0 to 2.6). Nontertiary delivery of 2000 to 2499 gm infants was associated with lower overall mortality (relative risk 0.5, 95% confidence interval 0.3 to 0.8), but higher-risk deliveries in this birth weight range were apparently concentrated at tertiary hospitals. CONCLUSIONS: In light of the apparent benefit of tertiary center birth for infants weighing < 2000 gm, the possible erosion of effective regionalized perinatal care networks should be monitored closely.

Absence of competitive interactions among axon terminals of regenerating motor neurons.

Competition among axon terminals is usually considered to contribute to the formation of patterned synaptic connections. During axonal regeneration of motor neurons in the cockroach, leg muscles initially become innervated by appropriate and inappropriate motor neurons. All axon terminals from inappropriate neurons eventually are eliminated, resulting in the reformation of the original innervation pattern. Destruction of an identified motor neuron by the intracellular injection of pronase did not prevent the elimination of inappropriate axon terminals in the muscle normally innervated by that motor neuron. Therefore, competition does not play a role in the reinnervation of the leg muscles. This indicates a major role for specific cell-cell recognition.

Intravenous cyclosporine activates afferent and efferent renal nerves and causes sodium retention in innervated kidneys in rats.

The effect of acute intravenous infusion of cyclosporine (10 mg/kg) on efferent renal and genitofemoral nerve activity and afferent renal nerve activity was studied in anesthetized rats. All animals were studied after unilateral renal denervation and extracellular fluid volume expansion. Activity of both efferent sympathetic nerves was increased significantly by cyclosporine infusion (renal, 69%; genitofemoral, 60%). Afferent renal nerve activity was increased 82% after cyclosporine (P less than 0.05). Urine flow rate and both absolute and fractional sodium excretion from the innervated kidney were reduced 50% after cyclosporine infusion (P less than 0.01). Absolute and fractional sodium excretion from the denervated kidney were significantly increased after cyclosporine. Infusion of vehicle had no significant effect on any measured variable in innervated or denervated kidneys. These studies demonstrate the capacity of cyclosporine to increase efferent sympathetic nerve activity and afferent nerve activity. It is also shown that sodium retention resulting from acute infusion of cyclosporine can be attributed to the increase in efferent renal nerve activity.

The Gore-Tex peritoneal catheter: a clinical evaluation and comparison with the Tenckhoff catheter.

In January of 1983, the Gore-Tex (W.L. Gore & Associates, Inc, Flagstaff, Ariz) peritoneal catheter was introduced into the dialysis market. Presently, there is no other peritoneal catheter that offers this unique subcutaneous tunnel design. This catheter has an external and intra-abdominal Silastic (Dow Corning, Midland, Mich) segment and a transcutaneous segment with a flange and cuff of expanded polytetrafluoroethylene (PTFE). This catheter was designed to decrease the incidence of tunnel infections, catheter cuff extrusions, and exit site infections. The clinical experience with 57 Gore-Tex catheters and 47 Tenckhoff catheters at Ohio State University from May 1980 through April 1983 is presented. In addition, the Gore-Tex catheter's surgical insertion technique and postoperative care procedures are described. There was a significant decrease in the incidence of tunnel infections with the Gore-Tex catheter versus the Tenckhoff catheter (0.03 versus 0.21 infections per patient-year, respectively; P less than .05). There was no significant difference between the Gore-Tex catheter and the Tenckhoff catheter with regard to the patient peritonitis rate (1.12 versus 1.38 episodes of peritonitis per patient-year, respectively) or the exit site infection rate (0.65 versus 0.50 infections per patient-year, respectively). There were no cuff extrusions with the Gore-Tex catheter. The decrease in the incidence of tunnel infections with the Gore-Tex catheter suggests that the PTFE barrier inhibits longitudinal bacterial movement and avoids bacterial sequestration. Patients with repeat tunnel infections may benefit from a Gore-Tex catheter placement.

The absence of specific dye-coupling among frog spinal neurons.

A double fluorescence labeling technique was developed to study the specificity of dye-coupling among frog spinal neurons. A pool of motoneurons known to be electrically coupled was prelabeled with a large molecule (rhodamine conjugated to horseradish peroxidase) that was not expected to pass through gap junctions. Then a single sensory or motor neuron within or outside this pool was injected with lucifer yellow to see if the dye spread specifically among neurons that are electrically coupled. We observed almost no examples of specific dye-coupling.

Selective reinnervation of limb muscles by regenerating frog motor axons.

The selectivity of reinnervation of limb muscles by the regenerating axons of adult, frog spinal cord motoneurons was determined. Reinnervation patterns were compared following axotomy when the ventral root was crushed or cut. Appropriate peripheral connections were reformed only after a nerve crush. The results suggest that selective reinnervation occurs if alignment of the nerve sheath is maintained.

Brain neurons which project to the spinal cord in young larvae of the zebrafish.

A small number of brain neurons project to caudal levels of the spinal cord in the larva of the teleost Brachydanio rerio. These cells were identified in animals 6 days after fertilization by backfilling with horseradish peroxidase following transection of the cord at the level of the cloaca. In preparations with the most labeled cells a total of 30-40 were present on each side of the midline. They were located within three regions of the brainstem: the midbrain nucleus of origin of the medial longitudinal fascicle (mlf), the hindbrain reticular formation, and the hindbrain vestibular nucleus. A total of 15 classes of cells could be distinguished by soma positions, dendritic fields, and axonal pathways. For some of these classes only one or two cells were usually present on each side of the brain. Most of the labeled cells contributed axons to the mlf ipsilateral to the soma; however, the Mauthner cells and three new types of hindbrain reticulospinal reticulospinal cells have decussating axons that enter the contralateral mlf. The observed distribution of labeled reticulospinal cells is similar to that previously described for large reticular cells in adult teleosts and to the system of identified Mauthner and Müller cells in the lamprey.