Somatosensory evoked potential spinal cord monitoring reduces neurologic deficits after scoliosis surgery: results of a large multicenter survey.

Neurologic deficits were compared to somatosensory evoked potential (SEP) spinal cord monitoring in a survey of spinal orthopedic surgeons. Experienced SEP spinal cord monitoring teams had fewer than one-half as many neurologic deficits per 100 cases compared to teams with relatively little monitoring experience. Experienced SEP monitoring teams also had fewer neurologic deficits than were seen in previous surveys of this group. Definite neurologic deficits, despite stable SEPs (false negative monitoring), occurred during surgery in only 0.063% of patients. Factors independently associated with fewer neurologic deficits also included the surgeon's years of experience in orthopedic surgery and the use of the wake-up test. Other technical survey results are also presented here. These results confirm the clinical efficacy of experienced SEP spinal cord monitoring for prevention of neurologic deficits during spinal surgery such as for scoliosis.

Effects of volume and periodicity on blood cultures.

Blood specimens collected for culture by using the high-volume resin-based BACTEC system over an 18-month period at the Seattle Veterans Administration Center were examined in this study. Of 7,783 cultures obtained, 624 were classified as true positives. Patients in this group had between 20 and 60 ml of blood drawn per culture and separated into 10-ml aliquots for incubation. Analysis of the results stratified by cultured volume and time interval between specimen collection accorded yield advantage to culture volume at the maximal amounts tested. No advantage was observed with any particular interval of collection. Increasing cultured volume from 20 to 40 ml increased yield by 19%. Increasing cultured volume from 40 to 60 ml increased yield by an additional 10%. The same effect was seen whether cultures were drawn simultaneously or serially within 24 h. These observations support other reports demonstrating increased yield with increased cultured blood volume. However, they demonstrate increases in yield at volumes much higher than previously considered. In conclusion, this study demonstrates that high-volume blood cultures drawn serially or simultaneously return the best yields.

A comparison of quantitative electroencephalography, computed tomography, and behavioral evaluations to localize impairment in patients with stroke and transient ischemic attacks.

Brain computed tomography and a structured behavioral assessment provided a better correlation than did quantitative electroencephalography to the presence of mild stroke or transient ischemic attacks in 21 patients. When electroencephalography did not correlate well, it tended to localize too laterally or miss deep lesions. Computed tomography did not identify 2 lesions when done early after disease onset. No test was uniformly more sensitive or accurate than others. They may complement each other.

Abnormal permanent pacemaker inhibition by a magnet: a case study.

Permanent pacemaker evaluation with a magnet is an essential and widely practiced procedure used by cardiologists and electrophysiology nurses for routine pacemaker follow-up. It is generally safely performed. We present a case of a prolonged period of pacemaker inhibition in a pacemaker-dependent patient after routine magnet placement over her permanent pulse generator.

Asymptomatic HIV infection does not cause EEG abnormalities: results from the Multicenter AIDS Cohort Study (MACS)

We conducted EEG testing in 200 asymptomatic homosexual men, half of whom were HIV seropositive. We chose to include half of the subjects because they were rated as impaired on a neuropsychological screening test. We used both traditional visual EEG interpretation and quantitative EEG analysis. Abnormal EEGs and borderline degrees of EEG slowing occurred in 32% of these men. These EEG changes were not related to HIV serostatus. EEG changes did correlate with the impaired neuropsychological test performance. Clinicians faced with abnormal EEG results or borderline EEG slowing in an asymptomatic HIV-seropositive patient should not attribute the EEG change to effects of the serostatus itself but should look for other causes.

Evaluation of autoSCAN-W/A automated microbiology system for the identification of non-glucose-fermenting gram-negative bacilli.

We evaluated the ability of the autoSCAN-W/A (MicroScan Division, Baxter Healthcare Corporation, West Sacramento, Calif.), in conjunction with the dried colorimetric Neg ID type 2 panel (DCP) and new rapid fluorometric Neg ID panel (RFP), to identify non-glucose-fermenting gram-negative bacilli by challenging the system with 310 previously identified reference strains. Of these 310 isolates, 286 organisms were in the DCP data base and 269 were in the RFP data base. Use of the DCP panels resulted in 118 (41.3%) correct and 64 (22.4%) incorrect first choice identifications at greater than or equal to 85% probability, 61 (21.3%) low-probability identifications, and 43 (15.0%) reports of unidentified organisms. The RFP system reported 135 (50.1%) correct and 25 (9.3%) incorrect identifications at greater than or equal to 85% probability and 109 (40.5%) low-probability identifications. Unidentified isolates (DCP system only) and isolates producing low-probability first choice identifications (both systems) required supplementary biochemical testing. Over half (37 of 64 [57.8%]) of the DCP misidentifications were due to four commonly isolated, saccharolytic organisms (Alcaligenes xylosoxidans subsp. xylosoxidans, Pseudomonas putida, Pseudomonas fluorescens, and Xanthomonas maltophilia), while 7 of 25 (28%) of misidentifications in the RFP system were due to P. fluorescens. Of note, the RFP system identified non-glucose-fermenting gram-negative bacilli within 2 h of panel inoculation, allowing additional conventional biochemical tests to be set up the same day on low-probability isolates, whereas only 13.5% of the DCPs could be read at 18 h, with the remainder requiring 42 h of incubation before reading. When organism identifications were recalculated with the updated RFP data base and revised software, only 8.1% of all 310 isolates were misidentified at greater than or equal to 85% probability while 77.1% of the isolates were now correctly reported at this same high probability.

Automated antibiotic susceptibility testing: comparative evaluation of four commercial systems and present state.

Automation of AST has come quite some way and is here to stay. In particular, fully automated, "hands off" instruments have great appeal to laboratories with a limited number of well-trained and experienced clinical microbiology personnel. None of the evaluated instruments is perfect, but then neither are the standard or reference techniques. Overnight incubation has been the yardstick since the early days of in vitro AST. Given the usually shorter therapeutic intervals of 4- to 12-hour dosage schedules, it is quite possible that shorter incubation times for in vitro tests will become more of a standard. Until that time, newer, including automatic, techniques need to be evaluated against the more traditional standard methods. Quality control is critical, and since no systematic approach aside from individual manufacturers' suggestions exists, it should be developed by the NCCLS or similar agencies. Quality control might include standards for the evaluation of such equipment and systems because the development of new technology in this area will continue. Overall, reproducibility and accuracy of the instruments and methods evaluated were quite promising and should encourage well-designed studies of clinical correlation and relevance. The AMS equipment has been in use for routine AST in the clinical laboratories of the Seattle Veterans Administration Medical Center and the University of Washington Hospital. Because of its simplicity and flexibility, the Kirby-Bauer method continues to be an alternate technique for certain important clinical isolates, for instance, blood cultures in both laboratories. Finally, it should be remembered that the most critical function of all such equipment is the reliable detection of resistance.

Critical evaluation of the AutoMicrobic system gram-negative identification card for identification of glucose-nonfermenting gram-negative rods.

During a 6-month study we critically evaluated the accuracy of the AutoMicrobic system Gram-Negative Identification Card (Vitek Systems, Inc., Hazelwood, Mo.) in identifying glucose-nonfermenting gram-negative bacilli by testing 419 selected isolates in parallel with a conventional reference method. Of 356 isolates included in the AutoMicrobic system profile, a total of 307 (86.2%) were correctly identified, 36 (10.1%) were not identified, and 13 (3.7%) were misidentified. Fifty-eight of 63 (92%) isolates not included in the profile were correctly reported as "unidentified organisms." Overall, if the first-choice identification was always accepted, only 18 (4.3%) isolates would have been incorrectly reported. When first-choice identifications appended with the special message "questionable biopattern" were rejected, and organisms were screened for characteristic odor and antimicrobial susceptibility before final acceptance of the AutoMicrobic system report, the number of misidentifications was reduced to 5 (1.2%). The average time to identification with the AutoMicrobic system Gram-Negative Identification Card was 15 h. This compares favorably with the 65 h required by the reference method.

Increased detection of staphylococcal bacteremia using an anti-microbial removal device.

During the period of August 16, 1981, through December 16, 1982, 15-mL blood culture specimens collected at the Seattle Veterans Administration Medical Center (SVAMC) were divided into two aliquots. The first 10-mL aliquot was inoculated directly into aerobic and anaerobic BACTEC (Johnston Laboratories, Towson, MD) vials (DIR); the remaining 5 mL was processed in an resin-containing Antimicrobial Removal Device (Marion Scientific, Kansas City, MO) before transfer to a second, identical set of aerobic and anaerobic vials (ARD). The final volume of inoculated blood from the ARD specimen was half that of the DIR specimen. Both sets of vials were processed using the BACTEC radiometric detection system. One hundred fifty specimen pairs grew 161 significant pathogens; 43 isolates were recovered only from the ARD sample, 39 only from the DIR samples, and 79 from both. Of the 35 isolates recovered from patients receiving anti-microbial agents active against the isolated pathogens, 21 were recovered only from the ARD specimen and 5 only from the DIR specimen (P less than 0.005). Of the 15 S. aureus strains isolated from patients on therapy, 12 were recovered only from the ARD specimen, 2 only from the DIR sample, and 1 from both samples (P less than 0.01). Ten of the 32 isolates of S. aureus recovered from antibiotic-free patients were found only in the ARD specimen and three only in the DIR specimen (P = 0.05). The ARD specimens recovered significantly more S. aureus from all patients regardless of antibiotic status.

Specimen volume versus yield in the BACTEC blood culture system.

During a 24-month period, 5,625 blood culture specimens were collected at the Seattle Veterans Administration Medical Center in 20-ml volumes and divided into separate 10-ml aliquots. The two aliquots were processed as duplicate sets (set 1, set 2) by the BACTEC system (Johnston Laboratories, Inc., Towson, Md.). Specimens (5 ml) from each set were inoculated into aerobic (6B) and anaerobic (7C/7D) vials. A total of 434 significantly positive blood cultures were found. In 342 of these positive cultures, yielding 379 isolates (112 members of the family Enterobacteriaceae, 104 staphylococci, 87 streptococci, 27 anaerobes, 20 yeasts, 14 pseudomonads, and 15 miscellaneous organisms), there was adequate specimen volume to fill all four vials. The utilization of set 1 would have resulted only in the failure to detect 65 of 379 (17.2%) significant isolates, 52 of 342 (15.2%) positive cultures, and 20 of 198 (10.1%) bacteremic episodes. There were no significant differences in the recovery of individual species in sets 1 and 2. Although the range of isolates recovered by the aerobic and anaerobic vials of each set differed, the percent yield of total isolates was similar, indicating total isolate yield was predominantly a function of specimen volume. The addition of set 2 most dramatically increased the recovery of Escherichia coli (30%), yeasts (33%), and anaerobes (42%).

Evaluation of the FIAX semiautomatic fluorescent immunoassay system for the detection of IgG antibodies to Toxoplasma gondii.

A commercially available solid phase fluoroimmunoassay system (FIAX, International Diagnostic Technology, Santa Clara, CA) was evaluated in parallel with a standard indirect fluorescent-antibody test (IFAT) for the detection of IgG antibodies to Toxoplasma gondii. Titers obtained by the FIAX method on the 101 patient samples correlated well with the standard procedure. Sensitivity of the FIAX system was 96% and specificity was 93%. A method for measuring serum titer reproducibility applicable to both conventional doubling dilution and to automated procedures was employed, allowing a meaningful comparison of precision in the two systems. It was found that titer reproducibility in the FIAX system was better than that of the IFAT and exceeded that expected with most conventional double-dilution serological procedures. The FIAX system will most benefit those laboratories with relatively large numbers of samples which can be batch tested.

Lack of clinical relevance in routine final subcultures of radiometrically negative BACTEC blood culture vials.

During a 38-month period, 10,106 blood specimens were received in the laboratory for culture. These were inoculated into 26,424 vials and processed using the BACTEC radiometric detection system. Of these vials, 1,914 were eventually found to be microbiologically positive. Isolates from 836 vials were judged to be contaminants. In the remaining 1,078 vials, growth was first detected visually or radiometrically in 1,062 and by final subculture in 16. Growth from these sixteen bottles represented 12 clinically significant bacteremic episodes in as many patients. In nine of these episodes, other culture vials from the same patient were positive radiometrically. Therefore, 358 of 361 (99.2%) bacteremic episodes were detected without the benefit of routine final subcultures. The three patients whose bacteremia was missed were diagnosed clinically and placed on appropriate therapy prior to the detection of the bacteremias by final subculture.

Influence of a blood culture inoculation technique on detection of bacteremia by the BACTEC system.

A 2-year study compared the influence of blood culture inoculation technique on the detection of bacteremia by an automated radiometric system (BACTEC; Johnston Laboratories, Inc.). A total of 4,690 specimens (20 ml each) were collected. Of each sample, 10 ml was inoculated into a pair of Bactec bottles at the bedside (BACTEC system). The remaining 10 ml was placed in an evacuated blood collection tube (VACUTAINER; Becton Dickinson VACUTAINER Systems) and transported to the laboratory for subsequent inoculation into an identical set of vials (VACUTAINER-BACTEC system). A total of 309 cultures grew organisms considered to be clinically significant. The recovery rate, time to positivity, and spectrum of isolates were similar for the two methods. There were substantially more sporeforming "contaminants" isolated in the VACUTAINER-BACTEC system.

Potential liabilities of gentamicin homogeneous enzyme immunoassay.

We report two potential liabilities of the homogeneous enzyme immunoassay for the determination of serum gentamicin. One is a considerable loss of precision and accuracy at the ends of the calibration curve, and the other is an apparent loss of gentamicin with storage at -60 degrees C.