Accuracy of a mixed venous saturation catheter during acutely induced changes in hematocrit in humans

OBJECTIVE

To determine the accuracy of in vivo mixed venous hemoglobin saturation (Svo2) measurements with a fiber optic thermodilution catheter during acute changes in hematocrit.

DESIGN

Comparison of fiberoptic in vivo Svo2 values with in vitro Svo2 values obtained with a multiwavelength spectrophotometer.

SETTING

Operating room in a university hospital.

PATIENTS

Six consecutive patients who are Jehovah's Witnesses.

MEASUREMENTS AND MAIN RESULTS

Before and after each step of hypervolemic hemodilution and after every 500 mL of blood loss, blood gases were analyzed and hemodynamic, hemoglobin, hematocrit, and in vitro and in vivo Svo2 measurements were made. Hematocrit values were measured in the range of 40% to 18%. Plotting all in vivo Svo2 values (n = 74) against the in vitro Svo2 measurements obtained during the entire study period gives r2 = .86. The accuracy of in vivo Svo2 measurements was not affected by changes in hematocrit or cardiac output. The Svo2 catheter value at the beginning of the study differed from the in vitro Svo2 value by -0.86 +/- 2.56% and at the end of the study period of 8 to 10 hrs by 0.71 +/- 3.04%.

CONCLUSIONS

The accuracy of the studied fiberoptic continuous measuring Svo2 system was not affected by changes in hematocrit or cardiac output. No significant drift in the in vitro Svo2 measurements was observed.

Ultrathin arthroscope for use in the lower compartment of the temporomandibular joint

Arthroscopy of the temporomandibular joint has been performed mainly in the upper joint space because the instruments available have been too thick to be safely inserted into the lower joint space. This article describes a newly developed ultrathin arthroscope with an outer diameter of 0.69 mm that has been specifically developed to be used in the lower space of the temporomandibular joint. This arthroscope can be inserted into the lower joint space with a standard 18-gauge needle. The article describes the arthroscope in its initial application to patient and cadaver material.

Pneumomediastinum after a transbronchial biopsy

A pneumomediastinum occurred after a transbronchial biopsy in a woman with pulmonary fibrosis and was confirmed by computed tomography. Although pneumomediastinum has a pathogenesis similar to that of pneumothorax it has not been reported after transbronchial biopsy.

Continuous measurement of intraarterial pHa, PaCO2, and PaO2 in the operating room

Miniaturized sensors based upon the principles of optical fluorescence can measure the pH, PCO2, and PO2 of liquid or gas media. A prototype of a three-component fiberoptic sensor has been developed for intraarterial application by CDI, 3M Health Care, Irvine, California. We report the first study of this continuous intraarterial monitor in patients undergoing surgical procedures under general anesthesia. Fourteen patients participated in the study. The fiberoptic sensor was calibrated before insertion and then passed through an existing 18-gauge radial artery cannula. Blood samples were drawn at frequent intervals through the same cannula for in vitro blood gas analysis. For each of the 87 arterial blood gas samples obtained, the in vitro values of pHa, PaCO2, and PaO2 were compared with simultaneous readings from the fiberoptic sensor. For pHa, the mean error (error = fiberoptic value minus in vitro value) or "bias" of the fiberoptic data was -0.032 and the standard deviation of error or "precision" was 0.042. For PaCO2, the bias was -3.8 mm Hg and the precision was 4.7 mm Hg. For PaO2, the bias was -9.0 mm Hg and the precision was 23.3 mm Hg. For PaO2 values less than 175 mm Hg, the bias was -8.5 mm Hg and the precision was 8.3 mm Hg. Expressed in terms of percentage errors, the bias +/- precision values were -11.5% +/- 13.3% for PaCO2, and -6.2% +/- 10.0% for PaO2. The duration of the surgical procedures ranged from 1.6 to 8 h with an average of 4.2 h.(ABSTRACT TRUNCATED AT 250 WORDS)

Histamine-induced constriction of canine peripheral lung: an airway or tissue response?

We compared the histamine responsiveness of peripheral airways (less than 6.0 mm diam) and parenchymal tissues in eight anesthetized paralyzed open-chest mongrel dogs. We measured pressure in a peripheral bronchus by using an antegrade wedged catheter and pressure in the alveolar region subtended by the wedged bronchus by using an alveolar capsule. Sinusoidal volume oscillations at a frequency of 0.5 Hz were delivered by a linear motor pump into the segment through the wedged catheter. We calculated the resistance of the segment (Rseg) and partitioned Rseg into tissue viscance (i.e., proportional to the resistive pressure drop between the alveolus and the pleura) and peripheral airway resistance. Measurements were taken under baseline conditions and after delivery of increasing concentrations of aerosolized histamine (0.1 micrograms/ml to 100.0 mg/ml) into the segment. We found that the histamine responsiveness of the peripheral airways and lung tissues varied markedly within a given dog. In four of eight dogs the airways were more responsive to histamine, in three of eight the tissues were more responsive, and in one of eight the response was equivalent at the two sites. We conclude that in a given animal, there is marked heterogeneity in the histamine responsiveness of the peripheral airways and parenchymal tissues and that either may dominate responsiveness in the peripheral lung.

Intracranial pressure and brain redox balance in rabbits

The effects of elevated intracranial pressure (ICP) on intracellular oxygenation and cerebrocortical blood volume (CBV) were studied in rabbits. Intracellular oxygen (O2) concentration was assessed as the level of pyridine nucleotide concentration ([NADH]) oxidation/reduction balance and relative cerebrocortical blood volume (CBV) were measured with a fibreoptic fluororeflectometer probe placed on the cerebrocortical surface. Experiments were conducted in six urethane anaesthetized, normocarbic animals at different fractions of inspired O2 (FIO2). During gradual increases in ICP, [NADH] began to increase (representing decreased intracellular mitochondrial PO2) for all values of FIO2 as ICP exceeded a threshold of 18 +/- 2.2 cmH2O (P less than 0.05). The decline in intracellular oxygenation with elevated ICP was inversely related to FIO2 (P less than 0.05). With ICP greater than 18 +/- 2.2 cmH2O, intracellular mitochondrial oxygenation showed an improvement between an FIO2 of 0.21 and 0.5 (P less than 0.05) but increasing FIO2 from 0.5 to 1.0 resulted in no statistically significant improvement in tissue redox balance. The CBV, largely representing tissue capillary blood, increased when ICP reached greater 18 +/- 1.2 cmH2O probably reflecting local autoregulation or venous distension (P less than 0.05). However, above 30 +/- 1.1 cmH2O, CBV decreased (P less than 0.05). The results demonstrate the interdependence of inspired oxygen concentration, elevated ICP, and brain intracellular oxygenation, and suggest that brain oxygen utilization deteriorates above an ICP of about 18 cmH2O.

A user's guide to flexible cystoscopes

This survey, carried out on behalf of the BAUS Instruments Committee, aims to assist the urologist in choosing a flexible cystoscope. The 5 most commonly available flexible cystoscopes (from ACMI, Olympus, Pentax, Storz and Wolf) were assessed in a clinical setting for handling, image quality and user satisfaction. Several technical characteristics, including deflection range, irrigant flow rate and optics, were tested in the laboratory. Whilst all instruments were satisfactory, the favourite of our testing panel was the Olympus CYF-2, which also came out best in the technical assessment and has the most comprehensive service support. The cheaper Storz instrument also performed well.

Percutaneous fiberoptic cardioscopy of the left ventricle

The feasibility of percutaneous transluminal cardioscopy of the left ventricle was examined in 35 patients with or without various heart diseases. A guiding balloon catheter (7 or 9 French) was introduced through the right femoral artery into the left ventricle. The balloon was inflated, and a fiberscope (1.6 or 4.3 French) was advanced to the distal tip of the catheter. The balloon was then manipulated against the portion of the ventricle targeted for examination, and heparinized saline (10 U/ml) at body temperature was infused through the catheter at 5 ml/sec for 3 to 6 sec. The images were recorded on videotape and 16 mm cinefilm. In 4 patients without demonstrable heart disease, the endocardial surface of the left ventricle was brown and the trabeculae became prominent during systole. The chordae connected to the mitral leaflets were white. In 3 of 5 patients with dilated cardiomyopathy, the endocardium was light yellow with thin trabeculae which barely contracted during systole. The endocardium was red or reddish-brown in 3 patients with acute myocarditis. In patients with rheumatic mitral stenosis white patches were scattered on the endocardial surface. In 7 of 8 patients the akinetic or dyskinetic segments representing prior infarctions were white. No complications other than transient ventricular arrhythmias were noted. We conclude that percutaneous fiberscopic imaging with a guiding balloon catheter is feasible and safe, and yields highly detailed images of the endocardium.

Sputum induction for the diagnosis of pulmonary disease in HIV positive patients

We prospectively compared sputum induction with bronchoalveolar lavage (BAL) in HIV positive patients presenting with acute respiratory episodes and also assessed the effects of using an experienced respiratory physiotherapist on the diagnostic yield from induced sputum. One hundred and fifty-one consecutive patients underwent sputum induction, in 96 the procedure was supervised by nursing and medical staff with no specific expertise (group I); in 55 patients a physiotherapist supervised sputum induction (group 2). Nine patients refused BAL having undergone sputum induction. Of the remaining 142 patients sputum induction failed (no sample expectorated) in 28 patients (25 from group 1 and three from group 2), the sample was inadequate (the material expectorated was not from the lower respiratory tract) in 29, and was adequate in 85 patients. Pneumocystis carinii was diagnosed in 82 patients (51 from group 1 and 31 from group 2). The sensitivity of induced sputum for the diagnosis of P. carinii was 13% and of BAL was 77%. In the subgroup of patients with an adequate induced sputum sample, the sensitivity of induced sputum was 28% and of BAL was 73%. Of the remaining 60 patients, 27 had other diagnoses made by induced sputum and BAL (eight patients), BAL only (15 patients) and induced sputum only (four patients). Eleven patients had bronchitis and responded to oral antibiotics. In 22 patients induced sputum and BAL were negative; alternative diagnoses were established by lung biopsy or by culture of blood, urine or CSF. During sputum induction, 15 patients had nausea and vomiting, eight became dyspnoeic, three had intractable cough and one developed acute bronchoconstriction; 17 patients found the procedure unpleasant. Compared with BAL, induced sputum has a lower diagnostic yield for P. carinii and other pathogens. Use of experienced, dedicated personnel increases the number of successful attempts at sputum induction but does not increase the diagnostic yield. Fibreoptic bronchoscopy and bronchoalveolar lavage remain necessary for patients with negative results from induced sputum and those whose disease course is at variance with the diagnosis made by sputum induction.

Fibre-optic bronchoscopic evaluation of tracheal tube position

Verification of tracheal tube position by fibre-optic bronchoscopy was evaluated in 20 critically ill adult patients. The distance between the carina and the tube was measured by direct visualization with a fibre-optic bronchoscope and compared with the corresponding measurement obtained from a concomitant chest radiograph. The measured values did not differ significantly and in 18 out of 20 patients the accuracy was within 2 cm. No adverse effects were observed. We conclude that verification of tracheal tube position by fibre-optic bronchoscopy is a safe alternative to chest X-ray.

[Chemiluminescence fiber optic immunosensor for detecting antibodies to the influenza virus]

A new variant of an optoimmunosensor for determination of antibodies to the influenza virus has been elaborated. Its advantages as compared to the traditional solid phase immunoenzyme analysis in respect to sensitivity and expressiveness are demonstrated. Time of the sensor response is below 17 min. When analyzing the 1:320 diluted serum, about 80% of response value is implemented after 6 min. Optimum conditions of the optoimmunosensor transducer regeneration are chosen. They permit reusing it for 20-30 cycles of measurements. A conclusion is made on the prospects of the developed variant of the optosensor for the immunoanalysis of antigens and antibodies under the equilibrium and kinetic conditions.

Transendoscopic Nd:YAG laser ablation of vaginal septa in a bitch

A vaginal septum was diagnosed in an English bulldog bitch during routine estrous cycle staging. The septum extended 16 cm from the vestibulo-vaginal junction to just caudal to the cervix. The septum was removed by two applications of an Nd:YAG laser via a flexible fiberoptic endoscope. Complete healing occurred over a 5-week period and was uneventful. The bitch was bred and subsequently delivered four puppies vaginally. Transendoscopic laser ablation provided a noninvasive approach to surgically remove a vaginal septum in the dog.

Site of upper airway obstruction in preterm infants with problematical apnoea

Airway obstruction is an important factor predisposing to the development of apnoea in preterm infants. An ultrafine fibreoptic scope was used to examine the upper airway of 12 preterm infants with recurrent problematical apnoea. Continuous visualisation of the airway was possible and recorded on to videotape together with simultaneous cardiorespiratory monitoring to detect apnoeic episodes in 12 infants studied. In seven infants obstruction was observed at laryngeal level with the arytenoid masses and aryepiglottic folds closing across the vocal cords. This was not only observed in obstructive apnoea but also during mixed apnoea in periods where no respiratory effort was detectable and again in apparently pure central apnoea. The findings confirm the larynx as an anatomical site of upper airway obstruction. They agree with other indirect methods of assessing airway patency that obstruction has an important role in the pathophysiology of apnoea of prematurity.

An apparatus for recording synaptic potentials from neuronal cultures using voltage-sensitive fluorescent dyes

Voltage-sensitive dyes offer the promise of noninvasive multicell recording of electrical activity, and should therefore be useful for studying the synaptic interactions of small networks of cultured neurons. We have designed and built a system for recording from microcultures of 1-15 neurons from the rat superior cervical ganglion (SCG), using voltage-sensitive fluorescent dyes of the styryl class. The apparatus comprises a standard inverted epifluorescence microscope; a mercury arc lamp with an optical feedback regulator; a 256-pixel fiber-optic camera with individual photodiode detectors and very low-noise amplifiers; and a personal computer-based data acquisition system. Its dark noise and illumination fluctuations are low enough that at typical fluorescence levels for these cells, it is limited by shot noise (the inherent physical limit of detection). Recording from SCG neurons, the signal-to-noise ratio is high enough to see large subthreshold synaptic potentials without signal averaging. This apparatus should be useful for studying long-term synaptic plasticity in cultures of vertebrate neurons, and several of its features should apply to optical recording from other preparations.

Flexible sigmoidoscopy may be ineffective for secondary prevention of colorectal cancer in asymptomatic, average-risk men

Asymptomatic men (N = 114) 50 years of age or older had screening for colorectal neoplasia with flexible sigmoidoscopy followed by colonoscopy regardless of the sigmoidoscopic result. Our study objective was to determine the prevalence of patients having isolated adenomatous polyps in a proximal colonic segment in the absence of a distal index neoplasm within reach of the sigmoidoscope. Through the combined use of sigmoidoscopy and colonoscopy, adenomatous polyps were detected in 47 of 114 individuals (41%). A total of 88 adenomas was found. Seventeen patients had isolated neoplasms in proximal colonic segments in the absence of distal adenomas. These patients represented 15% of screened subjects (17 of 114) and 20% of individuals who lacked adenomas on sigmoidoscopy (17 of 84). The majority of proximal neoplasms were small (less than 1.0 cm), tubular adenomas. Flexible sigmoidoscopy may be ineffective for screening asymptomatic men for neoplasia. However, it remains to be determined if a 20% miss rate (for those with a normal sigmoidoscopic examination) is significant and whether small proximal adenomas are worth finding.