Deep hypothermic circulatory arrest: I. Effects of cooling on electroencephalogram and evoked potentials.

BACKGROUND: Deep hypothermia is an important cerebral protectant and is critical in procedures requiring circulatory arrest. The purpose of this study was to determine the factors that influence the neurophysiologic changes during cooling before circulatory arrest, in particular the occurrence of electrocerebral silence. METHODS: In 109 patients undergoing hypothermic circulatory arrest with neurophysiologic monitoring, five electrophysiologic events were selected for detailed study. RESULTS: The mean nasopharyngeal temperature when periodic complexes appeared in the electroencephalogram after cooling was 29.6 degrees C +/- 3 degrees C, electroencephalogram burst-suppression appeared at 24.4 degrees C +/- 4 degrees C, and electrocerebral silence appeared at 17.8 degrees C +/- 4 degrees C. The N20-P22 complex of the somatosensory evoked response disappeared at 21.4 degrees C +/- 4 degrees C, and the somatosensory evoked response N13 wave disappeared at 17.3 degrees C +/- 4 degrees C. The temperatures of these various events were not significantly affected by any patient-specific or surgical variables, although the time to cool to electrocerebral silence was prolonged by high hemoglobin concentrations, low arterial partial pressure of carbon dioxide, and by slow cooling rates. Only 60% of patients demonstrated electrocerebral silence by either a nasopharyngeal temperature of 18 degrees C or a cooling time of 30 minutes. CONCLUSIONS: With the high degree of interpatient variability in these neurophysiologic measures, the only absolute predictors of electrocerebral silence were nasopharyngeal temperature below 12.5 degrees C and cooling longer than 50 minutes.

Deep hypothermic circulatory arrest: II. Changes in electroencephalogram and evoked potentials during rewarming.

BACKGROUND: Electrophysiologic studies during rewarming after deep hypothermic circulatory arrest probe the state of the brain during this critical period and may provide insight into the neurological effects of circulatory arrest and the neurologic outcome. METHODS: Electroencephalogram (EEG) and evoked potentials were monitored during rewarming in 109 patients undergoing aortic surgery with hypothermic circulatory arrest. RESULTS: The sequence of neurophysiologic events during rewarming did not mirror the events during cooling. The evoked potentials recovered first followed by EEG burst-suppression and then continuous EEG. The time to recovery of the evoked potentials N20-P22 complex was significantly correlated with the time of circulatory arrest even in patients without postoperative neurologic deficits (r = 0.37, (p = 0.002). The nasopharyngeal temperatures at which continuous EEG activity and the N20-P22 complex returned were strongly correlated (r = 0.44, p = 0.0002; r = 0.41, p = 0.00003) with postoperative neurologic impairment. Specifically, the relative risk for postoperative neurologic impairment increased by a factor of 1.56 (95% CI 1.1 to 2.2) for every degree increase in temperature at which the EEG first became continuous. CONCLUSIONS: No trend toward shortened recovery times or improved neurologic outcome was noted with lower temperatures at circulatory arrest, indicating that the process of cooling to electrocerebral silence produced a relatively uniform degree of cerebral protection, independent of the actual nasopharyngeal temperature.

Prevalence of human immunodeficiency virus infection in a sample of immigrants in the United States.

EDITOR'S NOTE: Years ago, experts predicted that the acquired immunodeficiency syndrome would spread to every part of the world and every part of society. The articles by Studemeister and Kent and Calonge and co-workers(*) that follow are further evidence that this is happening. These and other articles we will publish in the next few months confirm our worst fears and challenge all of us to continue engaging in basic, applied, and behavioral research and to continue providing the very best care, ranging from prevention through hospice, with an emphasis on compassion.

A large outbreak of acupuncture-associated hepatitis B.

An epidemiologic investigation of an acupuncturist's practice in Rhode Island identified 35 patients who were infected with hepatitis B virus during 1984. Of 366 patients seen by the acupuncturist during 1984, 316 (86%) completed questionnaires and submitted serum for hepatitis B serology. Use of tests for immunoglobulin M antibody to hepatitis B core antigen (IgM anti-HBc) identified 17 case-patients who otherwise may have gone undetected. Thirty-four of the 35 case-patients were treated in only one of the two clinics run by the acupuncturist. Patients who received a greater number of acupuncture needles during their treatment course were more likely to have been infected; the attack rate for patients who received less than 150 needles was 9%, compared with 33% for patients who received greater than or equal to 450 needles (p less than 0.001). Attack rates were higher during a one-month period when the index case-patient was more likely to have been viremic than during any other period in 1984 (relative risk = 4.1, 95% confidence interval = 2.3-7.3). While observing the acupuncturist's technique, the investigators noted several potential mechanisms for needle contamination. This study highlights the potential for transmission of hepatitis B in situations of repeated needle use.

Epidemic giardiasis caused by a contaminated public water supply.

In the period November 1, 1985 to January 31, 1986, 703 cases of giardiasis were reported in Pittsfield, Massachusetts (population 50,265). The community obtained its water from two main reservoirs (A and B) and an auxiliary reservoir (C). Potable water was chlorinated but not filtered. The incidence of illness peaked approximately two weeks after the city began obtaining a major portion of its water from reservoir C, which had not been used for three years. The attack rate of giardiasis for residents of areas supplied by reservoir C was 14.3/1000, compared with 7.0/1000 in areas that received no water from reservoir C. A case-control study showed that persons with giardiasis were more likely to be older and to have drunk more municipal water than household controls. A community telephone survey indicated that over 3,800 people could have had diarrhea that might have been caused by Giardia, and 95 per cent of households were either using alternate sources of drinking water or boiling municipal water. Environmental studies identified Giardia cysts in the water of reservoir C. Cysts were also detected in the two other reservoirs supplying the city, but at lower concentrations. This investigation highlights the risk of giardiasis associated with unfiltered surface water systems.

Screening for Chlamydia trachomatis infection in a sexually transmitted disease clinic: comparison of diagnostic tests with clinical and historical risk factors.

Of 212 consecutive male patients and 212 consecutive female patients attending a sexually transmitted disease (STD) clinic, 36 (17%) men and 28 (13%) women had urethral or cervical cultures positive for Chlamydia trachomatis. When compared with culture, the direct fluorescent antibody test (MicroTrak, Syva Co., Palo Alto, CA) had a sensitivity of 75% and a specificity of 97% in men; for women the sensitivity and specificity were 68% and 82%, respectively. One percent of test slides from men and 11% of slides from women were uninterpretable. Designation of high-risk patients for presumptive treatment, i.e., those with suggestive clinical syndromes, gonococcal infection, or exposure to others considered at high risk for chlamydial infection, as recommended by the Centers for Disease Control, proved to be 94% sensitive, 22% specific in men, and 82% sensitive, 35% specific in women when compared with results of culture. Three different screening methods using mucopurulent cervicitis, a cervicitis score, and a series of key risk factors were less sensitive than presumptive treatment and performed worse in our study than in those published previously. Our findings suggest that use of presumptive treatment guidelines appears to be effective in directing treatment to STD clinic patients with chlamydial infection.