Cynthia Cupido

Central venous catheter replacement strategies: a systematic review of the literature.

OBJECTIVE To evaluate the effect of guidewire exchange and new-site replacement strategies on the frequency of catheter colonization and infection, catheter-related bacteremia, and mechanical complications in critically ill patients. DATA SOURCES We searched for published and unpublished research by means of MEDLINE and Science Citation Index, manual searching of Index Medicus, citation review of relevant primary and review articles, review of personal files, and contact with primary investigators. STUDY SELECTION From a pool of 151 randomized, controlled trials on central venous catheter management, we identified 12 relevant randomized trials of catheter replacement over a guidewire or at a new site. DATA EXTRACTION In duplicate and independently, we abstracted data on the population, intervention, outcome, and methodologic quality. DATA SYNTHESIS As compared with new-site replacement, guidewire exchange is associated with a trend toward a higher rate of catheter colonization (relative risk 1.26, 95% confidence interval 0.87 to 1.84), regardless of whether patients had a suspected infection. Guidewire exchange is also associated with trends toward a higher rate of catheter exit-site infection (relative risk 1.52, 95% confidence interval 0.34 to 6.73) and catheter-related bacteremia (relative risk 1.72, 95% confidence interval 0.89 to 3.33). However, guidewire exchange is associated with fewer mechanical complications (relative risk 0.48, 95% confidence interval 0.12 to 1.91) relative to new-site replacement. Exchanging catheters over guidewires or at new sites every 3 days is not beneficial in reducing infections, compared with catheter replacement on an as-needed basis. CONCLUSIONS Guidewire exchange of central venous catheters may be associated with a greater risk of catheter-related infection but fewer mechanical complications than new-site replacement. More studies on scheduled vs. as-needed replacement strategies using both techniques are warranted. If guidewire exchange is used, meticulous aseptic technique is necessary.

POTENTIATION AND DEPRESSION OF THE M WAVE IN HUMAN BICEPS BRACHII

1. The effects of repeated excitation on the compound action potential, or M wave, of mammalian muscle fibres have been investigated in the human biceps brachii. 2. During continuous indirect stimulation at 10 and 20 Hz the mean voltage‐time area of the M wave doubled within the first minute, while the mean peak‐to‐peak amplitude increased by approximately half. The enlargement of the M wave was sustained during stimulation at 10 Hz but not at 20 Hz. Stimulation at 3 Hz caused a small increase which was significant for M wave amplitude only. 3. When the 20 Hz stimulation was performed under ischaemic conditions, the M wave first enlarged and then gradually declined. After 20 Hz stimulation was discontinued, the M wave increased in size; in the ischaemic experiments the release of the cuff produced a further, rapid augmentation. In both the ischaemic and non‐ischaemic experiments, the amplitudes and areas of the M waves during the recovery period became significantly larger than the resting values (range, 15‐60% at the endplate zone). 4. The mean muscle fibre impulse conduction velocity decreased to less than half the resting value during 20 Hz stimulation, with or without ischaemia, and then increased above the resting value during recovery. 5. On the basis of previous experiments in animals, the augmentation of the M wave was attributed to enhanced electrogenic Na(+)‐K+ pumping, and the biceps brachii appeared to be an excellent preparation for studying the time course of this enhancement.

Neuromuscular fatigue during repetitive stimulation in elderly and young adults.

SummaryThe purpose of this investigation was to examine the integrity of neuromuscular transmission and impulse propagation during fatigue by examining the muscle compound action potential (M wave) in elderly and young adults. The tibialis anterior muscle of nine elderly [{ie567-1}=67.7 (SE 1.7) years] and nine young [{ie567-2}=26.7 (SE 1.2) years] adults was maximally stimulated repetitively at frequencies of 20, 30 or 40 Hz for 60 s on separate occasions. There was a significantly smaller resting M wave amplitude [7.9 (SE 0.4) mV versus 9.9 (SE 0.6) mV] and M wave area [0.038 (SE 0.005) mV s versus 0.06 (SE 0.004) mV · s] in the elderly versus the young adults respectively. Measurement of the evoked muscle contractile properties revealed significantly (P<0.05) longer twitch durations and a significantly (P<0.05) greater peak twitch torque [4.6 (SE 0.4) Nm versus 3.2 (SE 0.5) Nm] in the elderly versus the young adults, respectively. The elderly adults had a significantly greater torque decline during the 20-Hz trial; however, the decline in torque during the 30-Hz and 40-Hz trials was similar in the elderly and the young adults (30 Hz: 40%; 40 Hz: 56%). Throughout each of the stimulation trials, the decline in torque was accompanied by a significant reduction in M wave amplitude (20 Hz: 14%; 30 Hz: 53%; 40 Hz: 67%); M wave area also declined significantly during the 30-Hz (31%) and 40-Hz (53%) trials. There was no significant difference between the elderly and the young adults in the reduction in the M wave amplitude or area during each trial. The similar electrical responses of the tibialis anterior between the elderly and the young adults suggest that any age-associated changes that occur in the neuromuscular apparatus do not appear to affect the integrity of neuromuscular propagation of the development of fatigue during repetitive stimulation at these frequencies.

Twitch potentiation during fatiguing exercise in the elderly: the effects of training

SummaryTwitch potentiation was studied during a fatigue paradigm involving intermittent maximum voluntary contractions (MVCs) of the tibialis anterior muscle in the elderly and in young adults. Resting twitch torques were similar between groups, but twitch potentiation was significantly greater (241% vs 166%) in the young; the recovery of the twitch after fatigue was similar between groups. Contraction time, time to peak torque and half-relaxation time were all significantly slower in the elderly. Following 12 weeks of resistance training in the elderly, there was no significant change in the twitch contractile properties at rest, but there was a significant main effect of training on the degree of twitch potentiation during the same fatigue protocol (peak potentiation 192% post-training vs 165% pre-training). These data suggest that the mechanism(s) responsible for twitch potentiation following MVCs may be influenced by both aging and training.

The RULER model. Is this how the somatosensory cortex works

Despite a wealth of information, it is still not known how neurones in the different neocortical layers interact to produce a conscious perception. We now put forward a model for the somatosensory cortex in which a touch is perceived whenever superficial cortical pyramidal cells (in layers II and III) are made to discharge by a recurrent input from deep pyramidal neurones (in layer V). The superficial cells act as biological amplifiers and the number discharging will depend both on the strength of the message from the thalamus and on the variable background depolarisation of their apical dendrites. The recurrent volley arises in the layer V neurones at the end of an IPSP (inhibitory postsynaptic potential), which itself follows an excitatory response induced by the incoming thalamic signal; the IPSP is generated by local basket cells. The duration of the initial excitation--IPSP--late excitation sequence corresponds to a time chunk, that is, the period over which neural activity is integrated to produce a perception. During the time chunk, the superficial cortical pyramids, unlike the deeper ones, can accumulate information as subthreshold excitatory postsynaptic potentials (EPSPs). The relative time at which the information arrived in the cortex is roughly coded by the gradient of EPSPs among cells in an axis perpendicular to the cortical surface. Although developed for the somatosensory cortex, the basic features of the model may well apply to other sensory receiving areas of the cortex.

Acute rehabilitation in critically ill children

Immobility increases morbidity, while early mobilization improves outcomes in adults. Rehabilitation practices in critically ill children, and the degree to which they are immobilized, are currently not well understood. The objective of this retrospective cohort study was to evaluate acute rehabilitation practices and potential barriers to mobilization in a tertiary care pediatric critical care unit (PCCU). Children aged less than 18 yr with a greater than 24 h length of stay were eligible. Outcomes of interest were physical therapy (PT) practice patterns, predictors of immobility, and adverse sequelae attributable to immobility. Interventions were classified as non-mobility and mobility types of PT. Ninety-one patients were included, 46.2% (42/91) were males. The mean age was 6.4 ± 6.4 yrs. Thirty-six of ninety-one (39.6%) patients received some form of PT while in PCCU. The mean proportion of PCCU days during which PT occurred was 20% (SD 28.8), and 3% (3/91) of patients received PT daily. Sixteen patients (17.6%) received exclusively non-mobility PT, 20 (22.0%) received some form of mobility, and six (6.6%) received both non-mobility and mobility PT. Increased severity of illness, mechanical ventilation, baseline disability and young age were identified barriers to mobilization. Immobilization is common in critically ill children. PT was often delayed until the patient was stabilized, and when performed was focused on respiratory function. Mobility PT was reserved for less sick, older, and non-mechanically ventilated patients. Future research is necessary to evaluate the significance of immobility and its impact on clinical outcomes in this population.

Assessing family members' satisfaction with information sharing and communication during Hospital care at the end of life

CONTEXT Despite the fact that most deaths occur in hospital, problems remain with how patients and families experience care at the end of life when a death occurs in a hospital. OBJECTIVES (1) assess family member satisfaction with information sharing and communication, and (2) examine how satisfaction with information sharing and communication is associated with patient factors. METHODS Using a cross-sectional survey, data were collected from family members of adult patients who died in an acute care organization. Correlation and factor analysis were conducted, and internal consistency assessed using Cronbachs alpha. Linear regression was performed to determine the relationship among patient variables and satisfaction on the Information Sharing and Communication (ISC) scale. RESULTS There were 529 questionnaires available for analysis. Following correlation analysis and the dropping of redundant and conceptually irrelevant items, seven items remained for factor analysis. One factor was identified, described as information sharing and communication, that explained 76.3% of the variance. The questionnaire demonstrated good content and reliability (Cronbachs alpha 0.96). Overall, family members were satisfied with information sharing and communication (mean total satisfaction score 3.9, SD 1.1). The ISC total score was significantly associated with patient gender, the number of days in hospital before death, and the hospital program where the patient died. CONCLUSIONS The ISC scale demonstrated good content validity and reliability. The ISC scale offers acute care organizations a means to assess the quality of information sharing and communication that transpires in care at the end of life.