Biomedical subjects

David G Nichols

Publications and source records attributed to David G Nichols.

3 recordsLinked to original sources

PubMed2003

Bronchodilator premedication does not decrease respiratory adverse events in pediatric general anesthesia.

PURPOSE: Upper respiratory infections (URI) presage perioperative respiratory complications, but thresholds to cancel surgery vary widely. We hypothesized that autonomically-mediated complications seen during emergence from anesthesia would be predicted by capnometry and reduced with preoperative bronchodilator administration. METHODS: Afebrile outpatient tertiary-care children (age two months to 18 yr, n = 109) without lung disease or findings, having non-cavitary, non-airway surgery for under three hours, were randomized to bronchodilator premedication vs placebo and had preoperative capnometry. After halothane via mask, laryngeal mask airway, or endotracheal tube, and regional anesthesia as appropriate, patients recovered breathing room air while cough, wheeze, stridor, laryngospasm, and cumulative desaturations were recorded for 15 min. RESULTS: In this specific population, there was no association between adverse events and either URI within six weeks (n = 76) or URI within seven days (n = 21). Neither albuterol nor ipratropium premedication decreased adverse events. Endotracheal intubation was associated with increased emergence desaturations and placebo nebulized saline increased emergence coughing. Neither anesthesiologists nor preoperative capnometry predicted adverse events. CONCLUSIONS: Adverse events were neither predicted nor prevented. In afebrile outpatient ASA I and II children with no lung disease or findings, having non-cavitary, non-airway surgery for under three hours, there was no association between either recent URI or active URI and desaturation, wheeze, cough, stridor, or laryngospasm causing desaturation (all P > 0.05). In this highly selected population of afebrile patients, the results suggest that anesthesiologists may proceed with surgery using specific criteria in the presence of a URI.

Anesthesia, General↗

PubMed2002

Effects of prolonged mechanical ventilation and inactivity on piglet diaphragm function.

OBJECTIVES: Muscle weakness is associated with immobilization, prolonged mechanical ventilation, critical illness and various critical care therapies. This study used an animal model simulating the critical care environment to investigate the effects of 5 days' mechanical ventilation and inactivity on diaphragm contractility and neurophysiologic function. DESIGN: Prospective laboratory study. SETTING: Animal research laboratory. SUBJECTS: Seven 2-3 month old piglets weighing 20-25 kg. INTERVENTIONS: The animals received constant-flow, volume-controlled mechanical ventilation (Tv 12-15 ml/kg, PEEP 3-5 cmH2O, I:E 1:2) and sedation without paralysis, and spontaneous breathing efforts were prevented. Evoked diaphragm contractions were achieved by transvenous phrenic nerve pacing. MEASUREMENTS AND MAIN FINDINGS: Transdiaphragmatic pressure (Pdi) measurements were used to assess force frequency relationships. Evoked electrophysiologic measures included lowest stimulus threshold and latency, compound muscle action potential (CMAP) amplitude and duration, and amplitude during repetitive nerve stimulation at 3 Hz. Lung function measures included airway pressures, tidal and minute volumes, and dynamic compliance and resistance. There were no clinically significant changes in hemodynamics, oxygenation or ventilation. Indirect measures of lung volume remained stable. Pdi decreased by 20% at all frequencies tested and was accompanied by a 30% decrease in evoked CMAP amplitude, (6.7+/-4.7 mV to 4.5+/-3.9 mV, p=0.01) while CMAP threshold, latency and duration were unchanged and no significant decrement in amplitude was seen during repetitive stimulation at 3 Hz. CONCLUSION: In this in-vivo model of prolonged mechanical ventilation in an intensive caring setting, 5 days of mechanical ventilation with sedation and complete diaphragm inactivity resulted in disturbed diaphragm contractility and activation, while nerve conduction and neuromuscular transmission were not affected. Based on these findings, it is likely that the changes seen occur at the level of peripheral muscle.

Action Potentials↗

PubMed2002

Pilot study of antibiotic cycling in a pediatric intensive care unit.

OBJECTIVE: This pilot study was performed to determine the safety and size of effect of antibiotic cycling to reduce colonization and infection with antibiotic-resistant bacteria. DESIGN: Open, observational study. SETTING: The study was performed in a 16-bed pediatric medical-surgical intensive care unit. PATIENTS: Critically ill children requiring antibiotic therapy. INTERVENTIONS: Three antibiotic classes were systematically cycled for 3-month intervals over 18 months. Antibiotic regimens were used for all empirical therapy and continued if the bacterial isolate was susceptible. MEASUREMENTS: The primary outcome was colonization with antibiotic-resistant bacteria, determined by surveillance cultures obtained twice monthly from all patients in the unit. Rates of antibiotic-resistant, nosocomial blood stream infections, and risks of colonization over calendar time in the intensive care unit were also evaluated. MAIN RESULTS: The cycling of broad-spectrum, empirical antibiotics was safe and did not generate increased antibiotic resistance nor select for new organisms. Over the study period, the trend in prevalence of children colonized with antibiotic-resistant bacteria was from 29% to 24% (p =.41). The effect on prevalence of resistant blood stream infections was similar (p =.29). Changes in individual risks of colonization with resistant bacteria over calendar time were consistent with the ecologic effect in size and direction. CONCLUSIONS: Results of this pilot intervention suggest that cycling antibiotics may be a safe and viable strategy to minimize the emergence of antibiotic resistance in intensive care units. A definitive study will require a randomized and controlled trial of only four pediatric intensive care units over an 18-month period.

Anti-Bacterial Agents↗