The Effect of Season and Weather on Orthopaedic Trauma: Consult Volume Is Significantly Correlated with Daily Weather.

INTRODUCTION: On-call orthopedic clinicians have long speculated that daily consult volume is closely correlated with weather. While prior studies have demonstrated a relationship between weather and certain fracture types, the effect of weather on total orthopaedic consult volume has not yet been examined. The aim of this study was to investigate this relationship. METHODS: We retrospectively reviewed orthopaedic consult data from 405 consecutive days at an urban, level one trauma center. The number, mechanism of injury, and type of consult were collected, along with daily weather data (temperature, wind, and precipitation). Statistical analysis was then performed to determine the relationship between weather and orthopaedic trauma consults. RESULTS: A total of 4543 consults were received during the study period. There was a significant difference in total number of consults between months of the year (p<0.001). A post hoc analysis revealed that this was due to increased volume in the summer months relative to the winter months (i.e., August 13.7 consults/day; January 9.3 consults/day). Average daily temperature and consult volume were also positively correlated (p<0.001, r= 0.30). While there was no significant association between precipitation and total consult volume, when there was over 0.25 inches of rain, there were less penetrating trauma (p=0.034) and motorcycle collision consults (p=0.013). CONCLUSION: Weather parameters, specifically average temperature and precipitation, were found to be associated with daily orthopedic consult type and volume. Additionally, consult volume varies significantly between months of the year. Because trauma centers are often resource scarce, this is an important relationship to understand for proper resource allocation.

Platelet concentrates transfusion in cardiac surgery and platelet function assessment by multiple electrode aggregometry.

BACKGROUND: Platelet dysfunction contributes to the pathophysiology of bleeding complications during and after cardiac surgery. In most surgical institutions, no peri-operative point-of-care monitoring of platelet function is used. We evaluated the usefulness of the Multiplate platelet function analyser based on impedance aggregometry for identifying groups of patients at a high risk of transfusion of platelet concentrates (PC). METHODS: Platelet function parameters were determined in 60 patients before and after routine cardiac surgery. Impedance aggregometry measurements were performed on Multiplate using ADP (ADPtest), collagen (COLtest) and thrombin receptor activating peptide (TRAPtest) as platelet activators. The correlations between the aggregometry results and the transfusion of PC were calculated. The results of the aggregation tests were also divided into tertiles and the differences in PC transfusion between the low and the high tertile were assessed. RESULTS: Low aggregometry delimited groups of patients with significantly higher PC transfusion. In the receiver operating characteristic curve, low pre-operative aggregation in the ADPtest identified patients with high total transfusion of PC (area under the curve 0.74, P=0.001), while the ADPtest performed at the end of the operation identified patients with high PC transfusion on the intensive care unit (ICU) (area under the curve 0.76, P=0.002). CONCLUSIONS: Near-patient platelet aggregation may allow the identification of patients with enhanced risk of PC transfusion, both pre-operatively and upon arrival on the ICU.

The preoptic area in the hypothalamus is the source of the additional respiratory drive at raised body temperature in anaesthetised rats.

In mammals that use the ventilatory system as the principal means of increasing heat loss, raising body temperature causes the adoption of a specialised breathing pattern known as panting and this is mediated by the thermoregulatory system in the preoptic area of the hypothalamus. In these species an additional respiratory drive is also present at raised body temperature, since breathing can reappear at low Pa,CO2 levels, when stimulation of chemoreceptors is minimal. It is not known whether the preoptic area is also the source of this additional drive. Rats do not pant but do possess this additional respiratory drive at raised body temperatures. We have therefore tested whether the preoptic area of the hypothalamus is the source of this additional respiratory drive in rats. Urethane anaesthesia and hyperoxia were used in eleven rats to minimise behavioural and chemical drives to breathe. The presence of the additional respiratory drive was indicated if rhythmic diaphragmatic EMG activity reappeared during hypocapnia (a mean Pa,CO2 level of 21+/-2 mm Hg, n = 11), induced by mechanical ventilation. The additional respiratory drive was absent at normal body temperature (37¿C). When the temperature of the whole body was raised using an external source of radiant heat, the additional respiratory drive appeared at 40.6+/-0.5 degrees C (n = 3). In two further rats this drive was induced at normal body temperature by localised warming in the preoptic area of the intact hypothalamus. The additional respiratory drive appeared at similar temperatures to those in control rats in three rats following isolation of the hypothalamus from more rostral areas of the brain. In contrast, the additional respiratory drive failed to appear at these temperatures in three rats after isolating the hypothalamus from the caudal brainstem, by sectioning pathways medial to the medial forebrain bundle. Since the preoptic area is known to contain thermoreceptors and to receive afferents from peripheral thermoreceptors, the results show that this area is also the source of the additional respiratory drive at raised body temperature in anaesthetised rats.

Direct detection of pulsations of the Cepheid star zeta Gem and an independent calibration of the period-luminosity relation.

Cepheids are a class of variable (pulsating) stars whose absolute luminosities are related in a simple manner to their pulsational periods. By measuring the period and using the 'period-luminosity' relationship, astronomers can use the observed visual brightness to determine the distance to the star. Because these stars are very luminous, they can be observed in other galaxies, and therefore can be used to help determine the expansion rate of the Universe (the Hubble constant). Calibration of the period-luminosity relation is a necessary first step, but the small number of sufficiently nearby Cepheids has forced the use of a number of indirect means, with associated systematic uncertainties. Here we present a distance to the Cepheid zeta Geminorum, determined using a direct measurement (by an optical interferometer) of its changes in diameter as it pulsates. Within our uncertainty of 15 per cent, our distance is in agreement with previous indirect determinations. Planned improvements to the instrument will allow us to calibrate directly the period-luminosity relation to better than a few per cent.

A respiratory drive in addition to the increase in CO(2) production at raised body temperature in rats.

Mammals that use the ventilatory system as the principal means of increasing heat loss, i.e. that pant, show two fundamental changes in the control of breathing at raised temperatures. First, alveolar ventilation increases by more than, rather than in proportion to, the increase in CO2 production. Second, hypocapnia no longer causes apnoea. Rats do not use the ventilatory system as the principal means of increasing heat loss, so we have investigated whether rats also show these two changes at raised temperatures. Breathing was detected from diaphragmatic electromyogram (EMG) activity. Anaesthesia and hyperoxia were used to minimise behavioural and hypoxic drives to ventilation and arterial PCO2 (Pa,CO2) was controlled using mechanical ventilation. At 36.6 +/- 0.1 >C, breathing was absent as long as Pa,CO2 was held below a threshold level of 32.9 +/- 0.7 mm Hg (n = 14) under steady-state conditions. When body temperature in rats was raised above 37 >C, both fundamental changes in the control of breathing became apparent. First, at 39 >C the mean Pa,CO2 level during spontaneous breathing (39.6 +/- 5.4 mm Hg, n = 4) fell by 3.9 +/- 1.4 mm Hg (P < 0.05, Student's paired t test). Second, at 39.9 +/- 0.1 >C breathing was present when mean Pa,CO2 levels were only 18.2 +/- 1.5 mm Hg (n = 14), the lowest mean Pa,CO2 level we could achieve with mechanical ventilation. We calculate, however, that at 39.9 >C, the drive to breathe from the increased CO2 production alone would not sustain breathing below a Pa,CO2 level of 27.8 +/- 1.4 mm Hg (n = 13). In rats at raised body temperatures therefore a respiratory drive exists that is in addition to that related to the increase in CO2 production.

Torque resistance of the passive tissues of the trunk at axial rotation.

Sitting in a twisted working posture is common when driving an agricultural tractor in the field. To be able to twist backwards, the driver has to overcome the torque from the passive tissues (passive resistance). The purpose of this investigation was to determine the relationship between passive resistance at axial rotation and twisting angle of the trunk when a person is seated. Ten healthy tractor drivers and 10 healthy office workers were passively twisted about the cranio-sacral axis with simultaneous measurements of the torque needed to twist them and the twisting angle. Surface electromyogram was used to control the relaxation of the muscles of the subjects. An exponential function was fitted to the data, which shows that passive resistance increases progressively with twisting angle. No significant differences in trunk passive resistance due to the subject's occupation, direction of twist or their interactions could be found. The fitted function is useful when assessing the load in the trunk in tractor driving, but also for other occupational activities where the trunk is twisted.

Apneic threshold for CO2 in the anesthetized rat: fundamental properties under steady-state conditions.

Experiments were performed to measure the apneic threshold for CO2 and its fundamental properties in anesthetized rats under steady-state conditions. Breathing was detected from diaphragmatic electromyogram activity. Mechanical hyperventilation resulted in apnea once arterial PCO2 (PaCO2) had fallen far enough. Apnea was not a reflex response to lung inflation because it did not occur immediately, was not prevented by vagotomy, and was reversed by raising PaCO2 without changing mechanical hyperventilation. The apneic threshold was measured by hyperventilating rats mechanically with O2 until apnea had occurred and then raising PaCO2 at constant hyperventilation until breathing reappeared. The mean PaCO2 level of the apneic threshold in 42 rats was 32.8 +/- 0.4 Torr. The level of the threshold did not depend on the volume at which the lungs were inflated. The level of the threshold, under steady-state conditions, was the same when approached from hypocapnia as from eupnea. The level of the threshold could be raised by 9 Torr by chronic elevation of the eupneic PaCO2 level by 18 Torr.

Human placental cytochrome P450 and quinone reductase enzyme induction in relation to maternal smoking.

Components of cigarette smoke such as cadmium and polycyclic aromatic hydrocarbons have been shown to induce quinone reductase (QR) activity in placental explants. This study examines the relationship of maternal smoking habit and maternal plasma cotinine concentration with the activities in vitro of both QR and the cytochrome P450 (CYP1A) marker ethoxyresorufin O-deethylase (EROD) in placental tissue. Maternal plasma samples were taken at Week 34 of gestation, and placental tissues were obtained at term. Plasma cotinine concentrations were determined by high-performance liquid chromatography. Trophoblast cytosolic QR and microsomal EROD activities were measured by resazurin reduction and ethoxyresorufin O-dealkylation respectively. QR activity was inhibited 70% by a mixture of dicoumarol (1 microM) and rutin (20 microM). Plasma cotinine concentrations correlated significantly (P < 0.001) with both declared smoking rate (r = 0.67, N = 37) and placental EROD activity (r = 0.63, N = 36), but not with QR activity, whether measured as total QR activity or specifically as either DT-diaphorase or carbonyl reductase. It is concluded that smoking up to 40 cigarettes per day induces EROD but does not affect QR activity in the placenta at term.