Association between exposure to anaesthesia and surgery and long-term cognitive trajectories in older adults: report from the Mayo Clinic Study of Aging.

BACKGROUND: The link between exposure to general anaesthesia and surgery (exposure) and cognitive decline in older adults is debated. We hypothesised that it is associated with cognitive decline. METHODS: We analysed the longitudinal cognitive function trajectory in a cohort of older adults. Models assessed the rate of change in cognition over time, and its association with exposure to anaesthesia and surgery. Analyses assessed whether exposure in the 20 yr before enrolment is associated with cognitive decline when compared with those unexposed, and whether post-enrolment exposure is associated with a change in cognition in those unexposed before enrolment. RESULTS: We included 1819 subjects with median (25th and 75th percentiles) follow-up of 5.1 (2.7-7.6) yr and 4 (3-6) cognitive assessments. Exposure in the previous 20 yr was associated with a greater negative slope compared with not exposed (slope: -0.077 vs -0.059; difference: -0.018; 95% confidence interval: -0.032, -0.003; P=0.015). Post-enrolment exposure in those previously unexposed was associated with a change in slope after exposure (slope: -0.100 vs -0.059 for post-exposure vs pre-exposure, respectively; difference: -0.041; 95% confidence interval: -0.074, -0.008; P=0.016). Cognitive impairment could be attributed to declines in memory and attention/executive cognitive domains. CONCLUSIONS: In older adults, exposure to general anaesthesia and surgery was associated with a subtle decline in cognitive z-scores. For an individual with no prior exposure and with exposure after enrolment, the decline in cognitive function over a 5 yr period after the exposure would be 0.2 standard deviations more than the expected decline as a result of ageing. This small cognitive decline could be meaningful for individuals with already low baseline cognition.

Physical activity as a determinant of fasting and 2-h post-challenge glucose: a prospective cohort analysis of the NAVIGATOR trial.

AIM: To investigate whether previous physical activity levels are associated with blood glucose levels in individuals with impaired glucose tolerance in the context of an international pharmaceutical trial. METHODS: Data were analysed from the NAVIGATOR trial, which involved 9306 individuals with impaired glucose tolerance and high cardiovascular risk from 40 different countries, recruited in the period 2002-2004. Fasting glucose, 2-h post-challenge glucose and physical activity (pedometer) were assessed annually. A longitudinal regression analysis was used to determine whether physical activity levels 2 years (t-2 ) and 1 year (t-1 ) previously were associated with levels of glucose, after adjusting for previous glucose levels and other patient characteristics. Those participants with four consecutive annual measures of glucose and two consecutive measures of physical activity were included in the analysis. RESULTS: The analysis included 3964 individuals. Change in physical activity from t-2 to t-1 and activity levels at t-2 were both associated with 2-h glucose levels after adjustment for previous glucose levels and baseline characteristics; however, the associations were weak: a 100% increase in physical activity was associated with a 0.9% reduction in 2-h glucose levels. In addition, previous physical activity only explained an additional 0.05% of the variance in 2-h glucose over the variance explained by the history of 2-h glucose alone (R(2)  = 0.3473 vs. 0.3468). There was no association with fasting glucose. CONCLUSIONS: In the context of a large international clinical trial, previous physical activity levels did not meaningfully influence glucose levels in those with a high risk of chronic disease, after taking into account participants' previous trajectory of glucose control.

Creating a model to predict time intervals from induction of labor to induction of anesthesia and delivery to coordinate workload.

BACKGROUND: Induction of labor continues to become more common. We analyzed induction of labor and timing of obstetric and anesthesia work to create a model to predict the induction-anesthesia interval and the induction-delivery interval in order to co-ordinate workload to occur when staff are most available. METHODS: Patients who underwent induction of labor at a single medical center were identified and multivariable linear regression was used to model anesthesia and delivery times. Data were collected on date of birth, race/ethnicity, body mass index, gestational age, gravidity, parity, indication for labor induction, number of prior deliveries, time of induction, induction agent, cervical dilation, effacement, and fetal station on admission, date and time of anesthesia administration, date and time of delivery, and delivery type. RESULTS: A total of 1746 women met inclusion criteria. Associations which significantly influenced time from induction of labor to anesthesia and delivery included maternal age (anesthesia P <0.001, delivery P =0.002), body mass index (both P <0.001), prior vaginal delivery (both P <0.001), gestational age (anesthesia P <0.001, delivery P <0.018), simplified Bishop score (both P <0.001), and first induction agent (both P <0.001). Induction of labor of nulliparous women at 02:00 h and parous women at 04:00 or 05:00 h had the highest estimated probability of the mother having her first anesthesia encounter and delivering during optimally staffed hours when our institution's specialty personnel are most available. CONCLUSIONS: Time to obstetric and anesthesia tasks can be estimated to optimize induction of labor start times, and shift anesthesia and delivery workload to hours when staff are most available.

Pressure-volume analysis of tissue water relations parameters for individual fascicles of loblolly pine (Pinus taeda L.).

A technique was tested for obtaining water relations parameters from individual fascicles of loblolly pine needles by the pressure-volume curve method. Comparisons were made between parameters derived from (1) individual fascicles that were rehydrated in a pressure chamber after being removed from the shoot and (2) fascicles that were rehydrated on the shoot. Estimates of tissue osmotic potential for needles rehydrated by the two methods were significantly different for needles from terminal shoots, but not significantly different for needles from lateral shoots. Similarly, a significant difference in the estimated tissue elasticity at zero water potential was noted for needles on terminal shoots, but not for those on lateral shoots. It is suggested that differences due to rehydration method are related to the duration of the rehydration period and not the choice of technique. The use of fascicles of needles, rehydrated after detachment, allows repeated estimation of the tissue water relations of a single conifer shoot.

Abscisic acid relations and the response of Populus trichocarpa stomata to leaf water potential.

The role of abscisic acid (ABA) in the mediation of stomatal responses to low leaf water potential was examined with intact plants and epidermal strips of Populus trichocarpa Torr. & A. Gray. Clones of this species grown under well-watered conditions maintain a high leaf conductance when the foliage wilts. However, foliar ABA concentration in P. trichocarpa increased manyfold in response to water stress as it did also in P. deltoides Bartr. ex Marsh. and P. trichocarpa x deltoides hybrids. Application of ABA to epidermal strips appeared to cause solute leakage, however stomata of P. trichocarpa remained partially open even when the guard cells were plasmolyzed. Foliar application of ABA induced closure of stomata in young expanding leaves, but not in fully expanded foliage. Ten days after ABA application, stomata on young leaves were open at high water potential but closed at low water potential. These characteristics are discussed with respect to wilty mutants of tomato and potato, which also have stomata unresponsive to leaf wilting.