Biomedical subjects

Michael W Varner

Publications and source records attributed to Michael W Varner.

41 records · Page 3Linked to original sources

PubMed2003

Changing prevalence of prenatal substance abuse in Utah.

OBJECTIVE: To estimate the current prevalence of prenatal exposure to methamphetamines and other drugs of abuse among infants born in Utah and compare the results with those of a maternal substance abuse prevalence study performed in 1991 in the same geographic area. METHODS: Thirteen well baby nurseries in calendar year 2000 and six neonatal intensive care units (NICUs) in 2001-2002 collected anonymous meconium samples and associated, but nonidentifiable, demographic data on consecutively born infants. Samples were screened by enzyme immunoassay and confirmed by gas chromotography/mass spectroscopy for methamphetamines, cannabinoids, and benzoylecognine. RESULTS: Meconium samples were collected from 1202 well baby nursery infants and 317 NICU infants. There were no significant differences in the rates of positivity for methamphetamines (0.6% versus 0.4%) or marijuana (2.9% versus 1.8%) between the 1991 and 2000/2001 studies. Cocaine prevalence declined from 1.1% in 1991 to 0.3% in 2000/2001 (P =.04). The prevalence of positivity for any of these three drugs declined over the 10-year period from 4.4% to 2.4% (P =.02). The prevalence for positivity for any of these three drugs was higher in the NICUs (4.7%) than in the well baby nurseries (1.9%, P =.008). CONCLUSION: The rate of drug-positive infants declined during the decade of the 1990s in a geographic area that is experiencing a sharp rise in the use of methamphetamine among women of childbearing age. Further studies that focus on women of childbearing age who use methamphetamine may help determine factors that impact their drug use during pregnancy and after the infant is born.

Cohort Studies↗

PubMed2003

Asthma morbidity during pregnancy can be predicted by severity classification.

BACKGROUND: The 1993 National Asthma Education Program Working Group on Asthma and Pregnancy defined asthma severity as mild, moderate, or severe on the basis of symptoms and spirometry, but no studies have evaluated the relationship between this classification system and subsequent asthma morbidity during pregnancy. OBJECTIVE: The objective of this study was to evaluate the relationship between asthma severity classification during pregnancy and gestational asthma exacerbations. METHODS: Asthma severity was defined according to the 1993 classification, adjusted to include medication requirements, in a volunteer sample of 1739 pregnant asthmatic patients who were less than 26 weeks' gestation. RESULTS: Initial asthma classification (mild, moderate, or severe) was significantly related to subsequent asthma morbidity during pregnancy (hospitalizations, unscheduled visits, corticosteroid requirements, and asthma symptoms during labor and delivery). Exacerbations during pregnancy occurred in 12.6% of patients initially classified as mild, 25.7% of patients classified as moderate, and 51.9% of patients classified as severe (P <.001). Asthma morbidity was similar, whether patients were classified as moderate or severe by symptoms and spirometry or by medication requirement. Thirty percent of initially mild patients were reclassified as moderate-severe during pregnancy, and 23% of the initially moderate-severe patients were reclassified as mild later in pregnancy; asthma morbidity in these patients changed accordingly. CONCLUSION: The National Asthma Education Program Working Group on Asthma and Pregnancy classification of asthma severity, adapted to include medication use, predicts subsequent asthma morbidity during pregnancy.

Adult↗

PubMed2003

The management of acardiac twins: a conservative approach.

OBJECTIVE: Optimal management of acardiac twin pregnancies is controversial. Data suggest a 50% mortality rate in the "pump" twin when the pregnancy is managed expectantly. Because of increased antenatal diagnosis, outcomes in expectantly managed cases may be better than reported. Our objective was to determine the outcome of expectantly managed acardiac twin pregnancies. STUDY DESIGN: All cases of antenatally diagnosed acardiac twins delivered in our community between 1994 and 2001 were ascertained. All were managed expectantly. Perinatal outcome of pump twins was the primary outcome variable. RESULTS: Ten cases were identified. Nine women were delivered of healthy pump twins. There was one neonatal death. The mean gestational age at delivery was 34.2 weeks. The mean weights of the pump and acardiac twins were 2279 g and 1372 g, respectively. CONCLUSION: Neonatal mortality of pump twins in antenatally diagnosed acardiac twin pregnancies may be considerably less than reported. Expectant management with close antepartum surveillance deserves consideration.

Diseases in Twins↗

PubMed2003

Robust estimation of fetal heart rate variability using Doppler ultrasound.

This paper presents a new measure of heart rate variability (HRV) that can be estimated using Doppler ultrasound techniques and is robust to variations in the angle of incidence of the ultrasound beam and the measurement noise. This measure employs the multiple signal characterization (MUSIC) algorithm which is a high-resolution method for estimating the frequencies of sinusoidal signals embedded in white noise from short-duration measurements. We show that the product of the square-root of the estimated signal-to-noise ratio (SNR) and the mean-square error of the frequency estimates is independent of the noise level in the signal. Since varying angles of incidence effectively changes the input SNR, this measure of HRV is robust to the input noise as well as the angle of incidence. This paper includes the results of analyzing synthetic and real Doppler ultrasound data that demonstrates the usefulness of the new measure in HRV analysis.

Aging↗

PubMed2002

Cerebral perfusion pressure, and not cerebral blood flow, may be the critical determinant of intracranial injury in preeclampsia: a new hypothesis.

OBJECTIVE: The relationship between cerebral perfusion pressure (CPP) and cerebral blood flow is unclear in preeclampsia. Our objective was to clarify this issue by comparing normal pregnant women to those with mild and severe preeclampsia. STUDY DESIGN: Patients with mild (n = 72) and severe (n = 120) preeclampsia underwent transcranial Doppler (TCD) imaging of the maternal middle cerebral artery (MCA). At the same time, blood pressure was taken with a Dinamap monitor (Dinamap; Criticon Inc, Tampa, Fla). CPP, resistance area product (RAP), and the cerebral flow index (CFI) were calculated by standard formulas. Data were plotted on normative curves for pregnancy (5% and 95%) and compared by chi(2) and Mann-Whitney U tests. RESULTS: CFI is usually normal in both severe (75%) and mild (72%) cases. If CFI is abnormal in severe cases, it may be either increased (14%) or decreased (10%), although in mild cases almost all abnormal CFI (25%) is lower than normal. In those cases with low or normal CFI, severe cases are associated with a significantly higher CPP, RAP, and MAP than mild cases (P <.05), although the CFI is not significantly different. A significant proportion of severe cases have high CPP (52%), whereas in mild cases the CPP is almost always normal (87%). Overall, in severe cases the RAP is abnormally high, although it is within the normal range in mild cases. CONCLUSIONS: One of the fundamental differences between mild and severe cases relates to the degree of cerebral perfusion pressure that the MCAs are subjected to. Because most preeclamptic women, regardless of degree of severity, have a normal CFI, it appears that autoregulation is generally intact. Because women with severe cases are more prone to cerebral catastrophe than those with mild preeclampsia, uncontrolled CPP may cause barotrauma and vessel damage, leading to hypertensive encephalopathy and overperfusion injury. Therapeutic strategies that ensure reduction of the CPP with maintenance of the CFI seem most likely to prevent the cerebral injuries (overperfusion or underperfusion) that cause seizures or death in women with preeclampsia.

Adult↗