Diagnosis of ventilator-associated pneumonia: comparison between ante-mortem and post-mortem cultures in trauma patients

PURPOSE

To evaluate the diagnostic utility of ante-mortem tracheal aspirates for diagnosis of ventilator-associated pneumonia (VAP). Trauma victims represent an otherwise healthy population, who are on multiple invasive life-support devices, which predispose them to severe infections like VAP. The diagnosis of VAP is challenging, due to the difficulty in obtaining a representative sample from lungs. We studied the diagnostic utility of tracheal aspirates by comparing its results with the post-mortem lung cultures.

MATERIALS AND METHODS

A total of 106 fatal trauma patients were included in the study. Lung samples and cardiac blood were taken for culture at the time of autopsy. The results of ante-mortem and post-mortem cultures were compared.

RESULTS

Septicemia was the cause of death in 51 (48%) of the fatal cases and VAP was identified in 36 (34%) cases. A total of 96 (90.5%) cases had pathogens isolated from lung samples. In 62 (58%) cases, the same organism was isolated from ante-mortem and post-mortem respiratory samples.

CONCLUSIONS

Culture results of a properly collected tracheal aspirate should be taken into consideration along with Centre for Disease Control and Prevention (CDC's) diagnostic criteria to maximise the diagnosis of VAP.

Mortality profile of patients with traumatic spinal injuries at a level I trauma care centre in India

BACKGROUND & OBJECTIVES

There is no national spinal trauma registry available in India at present and the research on epidemiology of these injuries is also very limited. The purpose of this study was to describe the mortality profile of patients with spinal injuries brought to a level I trauma centre in India, and to understand the predictive factors which identify patients at an increased risk of spinal trauma mortality.

METHODS

Retrospective data were collected from computerized patients records and autopsy reports maintained in the department of Forensic Medicine. All the cases with spinal injuries whether in isolation or as a part of polytrauma were reviewed. A total of 341 such cases were identified between January 2008 to December 2011. The demographic data, type of trauma, duration of survival, body areas involved, level of spinal injury and associated injuries if any, were recorded.

RESULTS

There were 288 (84.45%) males and 53 (15.55%) females. Most victims (73%) were between 25 and 64 yr of age, followed by young adults between 16 and 24 yr (19.35%). Male: female ratio was 5.4:1. Fifty five per cent cases had spinal injuries in isolation. Injury to the cervical spine occurred in 259 (75.95%) patients, thoracic spine in 56 (16.42%) and thoraco-lumbar spine in 26 (7.62%) patients. The commonest cause of injury was high energy falls (44.28%), followed by road traffic accidents (41.93%). The majority of deaths (51.6%) occurred in the phase IV (secondary to tertiary complications of trauma, i.e. >1 wk). Forty patients died in phase I (brought dead or surviving <3 h), 55 in phase II (>3 to 24 h) and 70 in phase III (> 24 h to 7 days).

INTERPRETATION & CONCLUSIONS

Our data suggest that there is an urgent need to take steps to prevent major injuries, strengthen the pre-hospital care, transportation network, treatment in specialized trauma care units and to improve injury surveillance and the quality of data collected which can guide prevention efforts to avoid loss of young active lives.

NaCl thresholds: relationship to anterior tongue locus, area of stimulation, and number of fungiform papillae

NaCl detection thresholds were determined for 12.5- and 50-mm(2) lingual areas at four anterior tongue locations in eight subjects using a device that allowed for accurate temporal and spatial presentation of tastants to small regions of the anterior tongue. The locations, all on the right side of the tongue, were the tongue tip, an area 1.7 cm posterior to the tongue tip, and regions 1.7 and 3.4 cm posterior to the tip along the tongue's lateral margin. Stimulus duration was 0.75 s. Thresholds were established using a two-alternative forced-choice single-staircase procedure, and the number of fungiform papillae at each stimulation site was counted with the aid of videomicroscopy. NaCl thresholds were lower for the 50-mm(2) than the 12.5-mm(2) stimulation area at all target sites, and were directly related to papillary number among and within the stimulated regions. For a given number of papillae, thresholds were lower within the 12.5-mm(2) than within the 50-mm(2) stimulation region, likely reflecting taste bud density and activation of common afferent pathways. The tongue tip was more sensitive than any other tongue region, and the lateral margins were seemingly more sensitive than the lingual centrum. Large individual differences in taste sensitivity and tongue papilla numbers were noted, and some subjects were insensitive to the highest tastant concentrations at the nontip loci. This study empirically demonstrates that NaCl detection sensitivity varies across discrete regions of the anterior tongue and is related to the relative number and density of fungiform papillae.

Effects of a pressure surround on the regional taste detection threshold for sodium chloride

The question as to whether tactile stimulation alters proximal taste function in humans has never been answered, despite the suggestion of anatomical and physiological associations between somatosensory and gustatory function in a number of species. In this study, we established NaCl detection thresholds for a 25 mm2 anterior tongue region on four test occasions in each of 12 men and 12 women. Testing was performed using the Regional Automated Taste Testing System (RATTS), a device that allows for accurate temporal and spatial presentation of tastants to the lingual surface. On each test occasion, a different negative pressure (vacuum suction) was applied around the stimulus presentation field of the glass stimulation device (i.e. 40, 50, 60 and 70 mmHg). The order of presentation of the vacua was systematically counterbalanced among subjects across sessions using 4 x 4 Latin square sequences. Neither the vacua nor their order of presentation meaningfully altered the taste threshold values, even though the higher vacua produced persistent discernible discomfort in most subjects. On average, taste thresholds tended to be marginally lower in women than in men. These data indicate that static vacuum-induced tactile stimulation around a discrete anterior taste field has no meaningful influence on NaCl detection threshold sensitivity.

An automated regional taste-testing system

A fully programmable and portable automated regional taste-testing system is described. This system utilizes a glass stimulator held to the surface of the tongue by a mild vacuum. Temporally and spatially discrete trains of stimuli, delivered from a bank of glass reservoirs through microprocessor-controlled Teflon solenoid valves and both glass and Tygon tubing, can be delivered to the lingual surface at millisecond durations. Rinses between stimuli are similarly programmed. The stimulus delivery is monitored at the surface of the tongue, using a capacitance sensor to alert the subject of stimulus delivery. An example of the application of this system is shown, in which we demonstrate that the detection threshold for NaCl is inversely related to stimulus duration by a power function.

Physostigmine enhances performance on an odor mixture discrimination test

Acetylcholine is found within key sectors of the olfactory pathway, and is the neurotransmitter for many bulbopetal axons terminating in the glomerular and internal plexiform layers of the olfactory bulb. The present study determined whether systemically administered physostigmine, a cholinesterase inhibitor, alters the rat's ability to discern among odorant mixtures. Following appropriate training, the performance of eight rats was measured every third day on an odor mixture discrimination test with six levels of difficulty. On each test day (separated from one another by 3 days), a different drug treatment was administered [i.e., 0.00 (saline), 0.05, 0.10, or 0.20 mg/kg physostigmine]. The presentation order of the treatments was counterbalanced across subjects using 4 x 4 Latin squares. The mixture discrimination test consisted of discerning the odor of an airstream coming from the saturated head space of a 1% concentration of ethyl acetate from an airstream saturated with a 1% concentration of ethyl acetate and various concentrations of butanol (i.e., 1, 0.5, 0.1, 0.05, 0.01, or 0.005%). Physostigmine was found to enhance odor discrimination performance on the more difficult discrimination tasks in a dose-related manner, suggesting that cholinergic activation may sharpen the ability of rats to discern subtle differences among complex odor stimuli.

SKF 38393 enhances odor detection performance

The purpose of this study was to determine the influence of the D1-selective partial agonist SKF 38393 on the odor detection performance of rats using high precision olfactometry and a go/no-go operant task. Previous studies have found that the D2 receptor partial agonist quinpirole decreases such performance, but the influences of D1 receptor activation are unknown. In experiment 1, such detection performance to the odorant ethyl acetate was enhanced by SKF 38393, relative to saline, in male rats at 7.5 and 10.0 mg/kg i.p. dose levels, but not at the lower doses of 1.0, 2.5, and 5.0 mg/kg. In experiment 2, this enhancement was replicated at the 7.5 and 10.0 mg/kg doses and was shown to occur at the 12.5 mg/kg dose as well. In experiment 3, similar enhancement was shown for the odorant eugenol in female rats at the 7.5, 10.0 and 12.5 mg/kg doses, suggesting this effect is neither sex-specific nor confined to the odorant ethyl acetate. In experiment 4, a 0.025 mg/kg dose of the D1 receptor antagonist SCH 23390 depressed the enhancement produced to ethyl acetate by 7.5 mg/kg SKF 38393 to control levels. Overall, these data demonstrate that, in contrast to quinpirole, SKF 38393 improves odor detection performance in the rat and that this phenomenon can be attenuated by the D1 receptor blocker SCH 23390.

Influence of stimulus duration on a regional measure of NaCl taste sensitivity

The present study demonstrates that perithreshold temporal integration occurs in the human taste system across stimulus durations ranging from 200 to 1500 ms in a manner analogous to that seen in other major sensory systems. Thus, the notion that gustation is comparatively insensitive to temporal stimulus parameters at threshold levels is disproved.