Tracheostomy decannulation failure rate following critical illness : a prospective descriptive study

Background : Tracheostomy is a well established and practical approach to airway management for patients requiring extended periods of mechanical ventilation or airway protection. Little evidence is available to guide the process of weaning and optimal timing of tracheostomy tube removal. Thus, decannulation decisions are based on clinical judgement. The aim of this study was to describe decannulation practice and failure rates in patients with tracheostomy following critical illness.

Methods : A prospective descriptive study was conducted of consecutive patients who received a tracheostomy at a tertiary metropolitan public hospital intensive care unit (ICU) between March 2002 and December 2006. Data were analysed using descriptive and inferential tests.

Results : Of the 823 decannulation decisions, there were 40 episodes of failed decannulation, a failure rate of 4.8%. These 40 episodes occurred in 35 patients: 31 patients failed once, 3 patients failed twice and 1 patient failed three times. There was no associated mortality. Simple stoma recannulation was required in 25 episodes, with none of these patients readmitted to ICU. Translaryngeal intubation and readmission to ICU took place for the remaining 15 episodes. The primary reason for decannulation failure was sputum retention. Twenty-four patients (60%) failed decannulation within 24 h, with 14 of these occurring within 4 h.

Conclusions : Clinical assessments coupled with professional judgement to decide the optimal time to remove tracheostomy tubes in patients following critical illness resulted in a failure rate comparable with published data. Although reintubation and readmission to ICU was required in just over one third of failed decannulation episodes, there was no associated mortality or other significant adverse events. Our data suggest nurses need to exercise high levels of clinical vigilance during the first 24 h following decannulation, particularly the first 4 h to detect early signs of respiratory compromise to avoid adverse outcomes.

Glycemic index and glycogen

INTRODUCTION : Fatigue in sports is often associated with depletion of muscle glycogen storage. Obesity is considered to be a major barrier against physical activity in sports. In order to bring the glycogen storage to a satisfactory level sports persons tend to increase consumption carbohydrates, preferred consumption of high glycemic index (HGI) than low glycemic index (LGI) diets. But HGI foods may promote postprandial carbohydrate oxidation at the expense of fat oxidation and increase body fat gain. LGI diets that produce a low and slow glycemic response may enhance higher glycogen storage instead of fat deposition.

METHODOLOGY : To test this hypothesis, 30 male Wistar rats after weaning were given either a high glycemic index (HGI) or low glycemic index (LGI) diet for until their age of 12 weeks. Then the subjects were scarified and their plasma, serum, and muscle samples were collected. RESULTS-The study revealed that HGI diets fed rats had higher plasma cholesterol and Leptin (LGI Leptin 1.34 +/- 0.13ng/ml, HGI Leptin 2.12 +/- .20ng/ml) concentrations. It also found the liver and muscle glycogen storage in LGI diets showed higher level (LGI-liver 108 +/-3.0 mg/100g, LGI-muscle 22.6+/- 2.3g/100g) than that of HGI (HGI-liver 96 +/- 2.0mg/100g, HGI-muscle 18+/- 1.5g/100g) diets.

CONCLUSION : the long term feeding of LGI carbohydrate encourages more glycogen storage while HGI increases fat deposition. Consumption of LGI diets has an advantage over HGI diets of higher physical activity while elevating glycogen storage and reducing chances of obesity.

Leptin and the development of obesity

The focus of this thesis was leptin and its role in the development of obesity and non-insulin-dependent diabetes mellitus (NIDDM). Studies in Psammomys obesus, a polygenic animal model of obesity and NIDDM, showed that ob gene expression and plasma leptin concentration correlated significantly with body weight, percentage body fat and plasma insulin concentration. In addition, plasma leptin concentrations were significantly elevated in insulin resistant Psammomys obesus independent of body weight. Dietary energy restriction from weaning in Psammomys obesus prevented excessive body weight gain, hyperleptinemia and hyperglycemia compared with ad libitum fed animals. Interestingly, 19% of the energy-restricted animals still developed hyperinsulinemia and tended to have increased plasma leplin compared with normoinsulinemic energy-restricted Psammomys obesus. Fasting for 24 hours significantly reduced plasma leptin concentration in lean, insulin-sensitive but not obese, insulin-resistant P. obesus, suggesting a dysregulation in the response of leptin to acute caloric deprivation in these animals. The effects of leptin administration to P. obesus were also investigated. Single daily intraperitoneal injection of 5 mg leptin/kg body weight for 14 days had no significant effect in lean or obese P. obesus. This dose had previously been shown to rapidly and significantly reduce food intake and body weight in ob/ob and wild-type mice, suggesting relative leptin resistance in P. obesus. Acute (8 hour) effects of administration of 5 mg leptin/kg body weight were also investigated. No significant effects on food intake or plasma insulin were detected, however blood glucose concentrations were significantly elevated in obese, glucose intolerant P. obexus, suggesting an exacerbation of insulin resistance in susceptible animals. Treatment of lean, healthy P. obesus with 45 mg leptin/kg body weight/day for 7 days resulted in significant decreases in food intake and percentage body fat, showing that the leptin resistance observed in this species could be overcome by the administration of very large doses of leptin. In another study, leplin was shown to significantly inhibit maximal insulin binding to isolated adipocytes, suggesting that leptin may respresent an important link between obesity and NIDDM. Links between aspects of obesity and NIDDM and polymorphisms in the ob and p3-adrencrgic receptor genes were also investigated in two human populations.

Terrestrial apnoeas and the development of cardiac control in Australian fur seal (Arctocephalus pusillus doriferus) pups

The development of cardiac control in association with terrestrial respiration patterns was examined throughout the period of maternal dependence in Australian fur seal pups. Resting eupnoic heart rate and respiration rate were significantly correlated (r² = 0.49) and both decreased with age (P < 0.05 in both cases). From an early age (1 month), pups displayed terrestrial apnoeas (18.1 ± 0.5 s) accompanied by substantial bradycardia (127 beats min^-1, a 13% decrease from eupnoic HR). Terrestrial apnoea duration increased significantly with age reaching a mean of 41 s just prior to weaning, slightly lower than the mean dive duration (52 s) previously recorded for pups of the same age. Correspondingly, mean apnoic heart rate decreased with age to 74 beats min^-1 just prior to weaning, representing a 25% decrease on eupnoic heart rate. Importantly, concomitant with the decrease in mean apnoic heart rate with age, an increase in the control
of bradycardia was evident with the variability in instantaneous apnoic heart decreasing such that older pups were able to maintain a low steady heart rate for the duration of the apnoea. The changes seen in these parameters are similar to those reported during postnatal development in elephant seals (Mirounga spp.) and harbour seals (Phoca vitulina), and are considered indicative of the development of cardiac control. These findings suggest a common strategy for the development of bradycardia control in both otariid and phocid seals.

Hypertension induced by ω-3 polyunsaturated fatty acid deficiency is alleviated by α-linolenic acid regardless of dietary source

Ω-3 polyunsaturated fatty acid deficiency, particularly during the prenatal period, can cause hypertension in later life. This study examined the effect of different sources of α-linolenic acid (canola oil or flaxseed oil) in the prevention of hypertension and other metabolic symptoms induced by an ω-3 fatty acid-deficient diet. Dams were provided one of three experimental diets from 1 week before mating. Diets were either deficient (10% safflower oil-DEF) or sufficient (7% safflower oil+3% flaxseed oil-SUF-F; or 10% canola oil-SUF-C) in ω-3 fatty acids. The male offspring were continued on the maternal diet from weaning for the duration of the study. Body weight, ingestive behaviors, blood pressure, body composition, metabolic rate, plasma leptin and brain fatty acids were all assessed. The DEF animals were hypertensive at 24 weeks of age compared with SUF-F or SUF-C animals; this was not evident at 12 weeks. These results suggest that different sources of ALA are effective in preventing hypertension related to ω-3 fatty acid deficiency. However, there were other marked differences between the DEF and, in particular, the SUF-C phenotype including lowered body weight, adiposity, leptin and food intake in SUF-C animals. SUF-F animals also had lower, but less marked reductions in adiposity and leptin compared with DEF animals. The differences observed between DEF, SUF-F and SUF-C phenotypes indicate that body fat and leptin may be involved in ω-3 fatty acid deficiency hypertension.

Influences on fecundity in Australian fur seals (Arctocephalus pusillus doriferus)

Recovery of the Australian fur seal (Arctocephalus pusillus doriferus) population has been slower than that of other fur seals, perhaps due to nutritional constraints on fecundity. However, the population doubled in recent decades, suggesting that reproductive rates may have changed. Pregnancy rates and birthrates were estimated and the influences of maternal age, size, condition, and lactation status were investigated over 3 consecutive breeding seasons (2003–2005). Mid-gestation pregnancy rate, estimated from plasma progesterone concentrations, was 84% ± 3% (mean ± SE) and was negatively influenced only by age (P< 0.001). Birthrate, estimated from observations of females with newborn offspring during the breeding season, was 53% 6 3% (mean ± SE) and was influenced negatively by lactation status (P = 0.035). The difference between pregnancy rates and birthrates suggests that a high degree of late-gestation abortion occurs, especially in younger females. Lactation status was not influenced by any variables, and the high rate (86% ± 2%; mean ± SE) suggests that many offspring are suckled beyond the typical weaning period. Although relationships between reproductive rates and body condition were not found, the results are consistent with a nutritional stress hypothesis. The recent increase in population growth is not due to increased fecundity, which remains low compared to other otariids. Paradoxically, high pregnancy rates were observed in young females (3 years), suggesting that rapid maturity is adaptive for benthic foragers.

Review : nurses can improve patient nutrition in intensive care

Aims and objectives. To review the literature and identify opportunities for nutritional practice improvement in the critically ill and opportunities to improve nurses’ knowledge relating to enteral feeding.

Background. The literature reports varying nutritional practices in intensive care.

Design. Systematic review.

Methods. A systematic search, selection, analysis and review of nursing, medical and dietetic primary research articles was undertaken. Fifteen studies met the selection criteria.

Results. Delivery of nutrition to the critically ill varied widely. Patients were frequently underfed and less frequently, overfed. Both under- and overfeeding have been linked with unacceptable consequences including infections, extended weaning from mechanical ventilation, increased length of stay and increased mortality. Underfeeding was related to slow initiation and advancement of nutrition support and avoidable feed interruptions. The most common reasons for interrupting feeds were gastrointestinal intolerance and fasting for procedures. Certain nursing practices contributed to underfeeding such as the management of gastric residual volumes.

Conclusions. Consistent and reliable nutrition support in intensive care units is hampered by a lack of evidence leading to varying nutrition practices. Factors impeding delivery of enteral nutrition were considered avoidable. A new concept of a therapeutic range of energy delivery in the critically ill has emerged implying the need for re-evaluation of energy recommendations and improved delivery of enteral nutrition.

Relevance to clinical practice. This review supports the multi-disciplinary development and implementation of an evidence-based enteral feeding protocol in intensive care units as a strategy to improve adequacy of nutritional intake. Critical care nurses are well placed to improve this process.

Life histories of the Insectivora : the role of phylogeny, metabolism and sex differences

Life-history data for 63 species from the mammalian order Insectivora have been collated from the literature. These data were analysed for covariation and for correlations with body mass, brain mass and mass-specific resting metabolic rate. An independent contrasts method has been used to remove the effect of phylogeny. Due to uncertainties surrounding their evolutionary relationships, 22 different phylogenies of insectivores have been used as a basis for comparative analysis. The results show that several key correlations between life-history variables are only significant when certain phylogenies are used, highlighting the problems of such analyses when the phylogeny used is inaccurate. After removing the effect of phylogeny, relatively few significant correlations remain. Insectivores that have a high body mass have relatively lower metabolic rates, longer lifespans and longer gestation lengths. There is some support for a fast±slow continuum in insectivore life-history evolution: there are some significant positive correlations between measures of growth rates (e.g. gestation length and age at weaning) and lifespan, and some negative correlations between growth rates and measures of reproductive output. It is suggested that the seasonality of life of many insectivores may have played an influential role in the evolution of the group, in particular in delaying the onset of sexual maturity. There is little indication that brain size influences life-history evolution in this order, but metabolism may play an important role. The energetic requirements of maintaining high metabolic rates in small mammals such as insectivores may be constraining life histories to a greater extent than occurs in larger mammals. This effect may have obscured the relationship between metabolic rate and life histories in wider inter-order analyses. Finally, there is considerable evidence that sex differences play a large role in shaping insectivore evolution, and it is suggested that this factor must be considered more often in future studies of mammalian life histories in general.

Influence of maternal mass and condition on energy transfer in Weddell seals

* 1
Environmental variation influences food abundance and availability, which is reflected in the reproductive success of top predators. We examined maternal expenditure, offspring mass and condition for Weddell seals in 2 years when individuals exhibited marked differences in these traits.
* 2
For females weighing 355 kg there was a positive relationship between maternal post-partum mass (MPPM) and lactation length, but below this there was no relationship, suggesting that heavier females were able to increase lactation length but lighter females were restricted to a minimum lactation period of 33 days.
* 3
Overall, females were heavier in 2002, but in 2003 shorter females were lighter than similar-sized females in 2002 suggesting that the effects of environmental variability on foraging success and condition are more pronounced in smaller individuals.
* 4
There was no relationship between MPPM and pup birth mass, indicating pre-partum investment did not differ between years. However, there was a positive relationship between MPPM and pup mass gain. Mass and energy transfer efficiency were 10·2 and 5·4% higher in 2002 than 2003, which suggests costs associated with a putatively poor-resource year were delayed until lactation.
* 5
Heavier females lost a higher proportion of mass during lactation in both years, so smaller females may not have been able to provide more to their offspring to wean a pup of similar size to larger females.
* 6
MPPM had only a small influence on total body lipid; therefore, regardless of mass, females had the same relative body composition. Females with male pups lost a higher percentage of lipid than those with female pups, but by the end of lactation female pups had 4·5% higher lipid content than males.
* 7
It appears that for Weddell seals the consequences of environmentally induced variation in food availability are manifested in differences in maternal mass and expenditure during lactation. These differences translate to changes in pup mass and condition at weaning with potential consequences for future survival and recruitment.

Determinants of permanent first incisor eruption in grazing Australian Angora goats

Objective: To investigate the effects of live weight, sex and other factors on deciduous (first incisor) loss and permanent first incisor development in Angora goats. Design: Goats were part of a pen study on the effects of energy intake in Angora does during pregnancy and lactation on kid growth and development. The design was three levels of nutrition in mid-pregnancy × two levels of postnatal nutrition in 17 randomised blocks. Methods: Conception times were calculated by using artificial insemination, with ultrasound examination 43 days after insemination. Does were fed different amounts of a formulated diet in their pens. After weaning, goats were grazed in sex groups. Deciduous first incisor loss and permanent first incisor development were recorded at 11 time points from 14 to 20 months of age. Results: For each sex, the time for visible eruption and full development of permanent first incisor declined linearly with increased live weight by 5.9 and 5.4 days/kg live weight, respectively. The time to reach similar development stages for first permanent incisors eruption was 3 months longer for the lightest animals compared with the heaviest animals. Date of birth, birth weight, doe age, growth rates, mid-pregnancy and postnatal nutrition, parity, day of weaning and weaning weight had no detectable effect. Conclusions: The results explain much of the substantial range in reported first permanent incisor eruption dates for small ruminants and have application in ageing of goats, marketing of kids for meat, in the selection of animals for breeding flocks and in educational material.

Stage of perinatal development regulates skeletal muscle mitochondrial biogenesis and myogenic regulatory factor genes with little impact of growth restriction or cross-fostering

Foetal growth restriction impairs skeletal muscle development and adult muscle mitochondrial biogenesis. We hypothesized that key genes involved in muscle development and mitochondrial biogenesis would be altered following uteroplacental insufficiency in rat pups, and improving postnatal nutrition by cross-fostering would ameliorate these deficits. Bilateral uterine vessel ligation (Restricted) or sham (Control) surgery was performed on day 18 of gestation. Males and females were investigated at day 20 of gestation (E20), 1 (PN1), 7 (PN7) and 35 (PN35) days postnatally. A separate cohort of Control and Restricted pups were cross-fostered onto a different Control or Restricted mother and examined at PN7. In both sexes, peroxisome proliferator-activated receptor (PPAR)-γ coactivator-1α (PGC-1α), cytochrome c oxidase subunits 3 and 4 (COX III and IV) and myogenic regulatory factor 4 expression increased from late gestation to postnatal life, whereas mitochondrial transcription factor A, myogenic differentiation 1 (MyoD), myogenin and insulin-like growth factor I (IGF-I) decreased. Foetal growth restriction increased MyoD mRNA in females at PN7, whereas in males IGF-I mRNA was higher at E20 and PN1. Cross-fostering Restricted pups onto a Control mother significantly increased COX III mRNA in males and COX IV mRNA in both sexes above controls with little effect on other genes. Developmental age appears to be a major factor regulating skeletal muscle mitochondrial and developmental genes, with growth restriction and cross-fostering having only subtle effects. It therefore appears that reductions in adult mitochondrial biogenesis markers likely develop after weaning.

The allometric relationship between mean fibre diameter of mohair and the fleece-free liveweight of Angora goats over their lifetime

As mean fibre diameter (MFD) is the primary determinant of mohair price we aimed to quantify the lifetime changes in mohair MFDas Angora goats aged and grew. Measurements were made over 12 shearing periods on a population of Angora goats representing the current range and diversity of genetic origins including South African, Texan and interbred admixtures of these and Australian sources. Records of sire, dam, birthweight, birth parity, liveweight, fleece growth and fleece quality were taken for does and castrated males (wethers) (n = 267 animals). Fleece-free liveweights (FFL_wt) were determined for each goat at shearing time by subtracting the greasy fleece weight from the liveweight recorded immediately before shearing. A restricted maximum likelihood growth curve model was developed for relating MFD to FFL_wt, age and other measurements.Asimple way of describing the results is:MFD= k (FFL_wt)b E; where k is a parameter that can vary in a systematic way with shearing(age), breed, weaning weight, sire, dam and individual; b is a parameter that is the same for nearly the whole study; and E are independent errors from a log-normal distribution. The analysis shows that ^b = 0.34, with s.e. (^b) = 0.021. Thus, mohair MFD was allometrically related to the cube root of FFLwt over the lifetime of Angora goats. However, the allometric proportionality constant differed in a systematic way with age at shearing, genetic strain, weaning weight, sire, dam and individual. For Texan-breed goats, MFD decreased as weaning weight increased (P = 0.00016). The findings indicate that management factors that affect liveweight and weaning weight have lifetime effects on mohair fibre diameter and therefore the value of mohair and the profitability of the mohair enterprise.

The allometric relationship between clean mohair growth and the fleece-free liveweight of Angora goats is affected by liveweight change

Clean fleece weight (CFWt) is affected by liveweight and change in liveweight in Merino sheep, Angora and cashmere goats. However, how these relationships progress as animals age has not been elucidated. Measurements were made over 12 shearing periods on a population of Angora goats representing the current range and diversity of genetic origins including South African, Texan and interbred admixtures of these and Australian sources. Records of breed, sire, dam, date of birth, dam age, birthweight, birth parity, weaning weight, liveweight, fleece growth and fleece quality were taken for does and castrated males (wethers) (n = 267 animals). Fleece-free liveweights (FFLwt) were determined for each goat at shearing time by subtracting the greasy fleece weight from the liveweight recorded immediately before shearing. The average of the FFLwt at the start of the period and the FFLWt at the end of the period was calculated (AvFFLwt). Liveweight change (LwtCh) was the change in FFLwt over the period between shearings. A restricted maximum likelihood model was developed for CFWt, after log10 transformation, which allowed the observations of the same animal at different ages to be correlated in an unstructured manner. A simple way of describing the results is: CFWt = κ (AvFFLwt)β, where κ is a parameter that can vary in a systematic way with shearing age, shearing treatment and LwtCh; and β is an allometric coefficient that only varies with LwtCh. CFWt was proportional to FFLwt0.67 but only when liveweight was lost at the rate of 5–10 kg during a shearing interval of 6 months. The allometric coefficient declined to 0.3 as LwtCh increased from 10 kg loss to 20 kg gain during a shearing interval. A consequence is that, within an age group of Angora goats, the largest animals will be the least efficient in converting improved nutrition to mohair.

Association between maternal education and diet of children at 9 months is partially explained by mothers' diet

Infants of mothers of low educational background display consistently poorer outcomes, including suboptimal weaning diets. Less is known about the different causal pathways that relate maternal education to infants' diet. The present study aimed to test the hypothesis that the relationship between maternal education and infants' diet is mediated by mothers' diet. The analyses included 421 mother–infant pairs from the Melbourne Infant Feeding Activity and Nutrition Trial (InFANT) Program. Dietary intakes were collected from mothers when infants were aged 3 months, using a validated food frequency questionnaire relating to the past year, and in infants aged 9 months using 3 × 24-h recalls. Principal component analysis was used to derive dietary pattern scores, based on frequencies of 55 food groups in mothers, and intakes of 23 food groups in infants. Associations were assessed with multivariable linear regression. We tested the product ‘ab’ to address the mediation hypothesis, where ‘a’ refers to the relationship between the predictor variable (education) and the mediator variable (mothers' diet), and ‘b’ refers to the association between the mediator variable and the outcome variable (infants' diet), controlling for the predictor variable. Maternal scores on the ‘Fruit and vegetables’ dietary pattern partially mediated the relationships between maternal education and two infant dietary patterns, namely ‘Balanced weaning diet’ [ab = 0.11; 95% confidence interval (CI): 0.04; 0.18] and ‘Formula’ (ab = −0.08; 95%CI: −0.15; −0.02). These findings suggest that targeting pregnant mothers of low education level with the aim of improving their own diet may also promote better weaning diets in their infants.