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Biomedical subjects

A Esteban

Publications and source records attributed to A Esteban.

At least 37 records · Page 2Linked to original sources
PubMed2001

A comparison of two methods to perform a breathing trial before extubation in pediatric intensive care patients.

OBJECTIVE: To compare the percentage of infants and children successfully extubated after a trial of breathing performed with either pressure support or T-piece. DESIGN: Prospective and randomized study. SETTING: Three medical-surgical pediatric intensive care units (PICUs). PATIENTS: Two hundred fifty-seven consecutive infants and children who received mechanical ventilation for at least 48 h and were deemed ready to undergo a breathing trial by their primary physician. INTERVENTIONS: Patients were randomly assigned to undergo a trial of breathing in one of two ways: pressure support of 10 cmH2O or T-piece. Bedside measurements of respiratory function were obtained immediately before discontinuation of mechanical ventilation and within the first 5 min of breathing through a T-piece. The primary physicians were unaware of those measurements, and the decision to extubate a patient at the end of the breathing trial was made by them. MEASUREMENTS AND MAIN RESULTS: Of the 125 patients in the pressure support group, 99 (79.2%) completed the breathing trial and were extubated, but 15 of them (15.1%) required reintubation within 48 h. Of the 132 patients in the T-piece group, 102 (77.5%) completed the breathing trial and were extubated, but 13 of them (12.7%) required reintubation within 48 h. The percentage of patients who remained extubated for 48 h after the breathing trial did not differ in the pressure support and T-piece groups (67.2% versus 67.4%, p=0.97). CONCLUSIONS: In infants and children mechanically ventilated, successful extubation was achieved equally effectively after a first breathing trial performed with pressure support of 10 cmH2O or a T-piece.

Age Factors↗
PubMed2001

Botulinum toxin in motor disorders: practical considerations with emphasis on interventional neurophysiology.

After a brief review of the pharmacological properties of the botulinum toxin (BT), its mechanism of action on the nerve endings of the neuromuscular junctions, and the general therapeutic principles and adverse side effects, we discuss the advantages of interventional neurophysiology for the treatment of focal motor disorders by means of botulinum toxin A (BTA) muscle infiltration. Electromyography (EMG) provides a valuable objective information in the diagnosis of many motor disturbances and enables the precise identification of the muscles that contribute to the abnormal movement or posture. The use of EMG guidance for BTA injection seems advisable in every muscle but it become indispensable in those difficult to access, deeply located or partially atrophied by previous toxin infiltrations. The EMG study also serves to localise the areas with the highest abnormal activity and the motor point of the muscle, where the injection of toxin exerts its maximal effect. Consequently, lower doses of BTA can be employed without decreasing the efficacy of treatment but reducing the potential risk of side effects, antibody production and the cost of treatment. Electrophysiological diagnosis and BTA treatment may be performed during the same exploration. Considerations on the particular aspects and lines of action are given referring to the main focal muscular hyperactivity motor disorders such as cervical, oromandibular and laryngeal dystonias, blepharospasm, writer's cramp, hemifacial and hemimasticatory spasms, infantile and adult forms of spasticity and some other focal disturbances such as strabismus, detrusor-sphincter dyssynergia and anismus.

Anti-Dyskinesia Agents↗
PubMed2001

Predicting success in weaning from mechanical ventilation.

We identified 65 observational studies of weaning predictors that had been reported in 70 publications. After grouping predictors with similar names but different thresholds, the following predictors met our relevance criteria: heterogeneous populations, 51; COPD patients, 21; and cardiovascular ICU patients, 45. Many variables were of no use in predicting the results of weaning. Moreover, few variables had been studied in > 50 patients or had results presented to generate estimates of predictive power. For stepwise reductions in mechanical support, the most promising predictors were a rapid shallow breathing index (RSBI) < 65 breaths/min/L (measured using the ventilator settings that were in effect at the time that the prediction was made) and a pressure time product < 275 cm H2O/L/s. The pooled likelihood ratios (LRs) were 1.1 (95% confidence interval [CI], 0.95 to 1.28) for a respiratory rate [RR] of < 38 breaths/min and 0.32 (95% CI, 0.06 to 1.71) for an RR of > 38 breaths/min, which indicate that an RR of < 38 breaths/min leaves the probability of successful weaning virtually unchanged but that a value of > 38 breaths/min leads to a small reduction in the probability of success in weaning the level of mechanical support. For trials of unassisted breathing, the most promising weaning predictors include the following: RR; RSBI; a product of RSBI and occlusion pressure < 450 cm H2O breaths/min/L; maximal inspiratory pressure (PImax) < 20 cm H2O; and a knowledge-based system for adjusting pressure support. Pooled results for the power of a positive test result for both RR and RSBI were limited (highest LR, 2.23), while the power of a negative test result was substantial (ie, LR, 0.09 to 0.23). Summary data suggest a similar predictive power for RR and RSBI. In the prediction of successful extubation, an RR of < 38 breaths/min (sensitivity, 88%; specificity, 47%), an RSBI < 100 or 105 breaths/min/L (sensitivity, 65 to 96%; specificity, 0 to 73%), PImax, and APACHE (acute physiology and chronic health evaluation) II scores that are obtained at hospital admission appear to be the most promising. After pooling, two variables appeared to have some value. An RR of > 38 breaths/min and an RSBI of > 100 breaths/min/L appear to reduce the probability of successful extubation, and PImax < 0.3, for which the pooled LR is 2.23 (95% CI, 1.15 to 4.34), appears to marginally increase the likelihood of successful extubation. Judging by areas under the receiver operator curve for all variables, none of these variables demonstrate more than modest accuracy in predicting weaning outcome. Why do most of these tests perform so poorly? The likely explanation is that clinicians have already considered the results when they choose patients for trials of weaning.

APACHE↗
PubMed2001

Evolution in the utilization of the mechanical ventilation in the critical care unit.

Use of mechanical ventilation has increased in recent years and constitutes a major therapeutic modality in the intensive care unit (ICU). In the recent years, changes in the ventilatory modes, in the ventilatory strategies and in the weaning from mechanical ventilation have occurred. We have compared the data obtained from the Spanish ICUs in studies that were carried out in three periods of the nineties, with the aim to test whether the aforementioned innovations have modified the clinical practice. We analyzed demographic data, primary reason for mechanical ventilation, ventilatory parameters, mode of weaning and performance of tracheostomy. It was observed a decrease in the percentage of patients receiving mechanical ventilation. There was a significant trend to ventilate older patients over the course of the decade. In the mode of ventilation, we observed a significant decrease in the use of the synchronized intermittent mandatory ventilation with a increment in the use of assist-control ventilation. We did not find differences in the ventilatory settings. Concerning to weaning, over the course of the decade occurred an increase in use of pressure support ventilation and spontaneous breathing trial, being this method the most frequently used at the end of the decade. The performance of the tracheostomy has been lesser and earlier over the time. The results obtained suggest that findings from research on mechanical ventilation are incorporated into clinical practice at a very slow pace whereas the evidence obtained from the clinical trials about weaning has had a better reception.

Female↗
PubMed2000

Weaning from mechanical ventilation.

Practice guidelines on weaning should be based on the results of several well-designed randomized studies performed over the last decade. One of those studies demonstrated that immediate extubation after successful trials of spontaneous breathing expedites weaning and reduces the duration of mechanical ventilation as compared with a more gradual discontinuation of ventilatory support. Two other studies showed that the ability to breathe spontaneously can be adequately tested by performing a trial with either T-tube or pressure support of 7 cmH2O lasting either 30 or 120 min. In patients with unsuccessful weaning trials, a gradual withdrawal for mechanical ventilation can be attempted while factors responsible for the ventilatory dependence are corrected. Two randomized studies found that, in difficult-to-wean patients, synchronized intermittent mandatory ventilation (SIMV) is the most ineffective [corrected] method of weaning.

Aged↗
PubMed2000

Hemodynamic, biochemical and morphological changes induced by aminoguanidine in normal and septic sheep.

OBJECTIVE: To define the acute hemodynamic, metabolic, and morphological changes induced by aminoguanidine, a selective iNOS inhibitor, in septic sheep. DESIGN: Prospective, nonrandomized animal study. SETTING: Animal research facility in a University Hospital. INTERVENTIONS: Adult sheep, sedated and mechanically ventilated, were monitored with a pulmonary arterial catheter and an ultrasonic blood flow probe in the mesenteric artery, to measure the systemic (Q(TOT)I) and the mesenteric (Q(MES)I) blood flow indices, and an ileal tonometer. Four groups of sheep were studied: nonseptic, septic, nonseptic treated with aminoguanidine, and septic treated with aminoguanidine (100 mg kg(-1) h(-1)) (n = 6 for each group). Sepsis was induced by the intravenous administration of E. coli. Hemodynamic and biochemical parameters were measured during 300 min. Histological changes in the liver and small intestinal mucosa were analyzed at the end of the experiment. MEASUREMENTS AND MAIN RESULTS: In nonseptic animals, aminoguanidine slightly increased mean systemic arterial pressure (MAP), decreased Q(TOT)I, and increased vascular resistance index (SVRI) and pulmonary vascular resistance index. Q(MEs)I did not change and Q(MES)I/Q(ToT)I increased. Aminoguanidine also induced intestinal intramucosal hypercarbia, hyperlactatemia, acidemia, hypoglycemia, and morphological signs indicative of tissue ischemia in the small intestinal mucosa. In septic sheep, aminoguanidine increased SVRI and MAP only at 4 h after the septic challenge and thereafter, and worsened gas exchange. CONCLUSIONS: In this model, exogenous administration of aminoguanidine induces beneficial hemodynamic effects 4 h after the septic challenge. In normal animals, however, aminoguanidine was associated with hypoglycemia, acidosis, hyperlactatemia, and intestinal mucosal ischemia.

Acidosis↗
PubMed2000

Peroxidase activity in Aloe barbadensis commercial gel: probable role in skin protection.

A basic peroxidase (EC 1.11.1.7) (pl around 9.0) has been identified in commercial gel of Aloe barbadensis. In vivo, the activity is localised in the vascular system of inner aqueous leaf parenchyma. Some relevant properties of this basic peroxidase of Aloe have been investigated in leaf extract and in commercial gel where it is notably stable. The acid optimum pH (5.0) for activity and the low KM for H2O2 (0.14 mM) suggest that, when topically applied, Aloe peroxidase may scavenge H2O2 in skin surface.

Aloe↗
PubMed2000

Accidental removal of endotracheal and nasogastric tubes and intravascular catheters.

OBJECTIVES: To characterize the rates of accidental removal of endotracheal tubes, nasogastric tubes, central venous catheters, and arterial catheters. To assess the efficacy of corrective measures aimed at reducing the accidental removal of these devices. DESIGN: Prospective, observational, and interventional study. SETTING: Eighteen-bed medical-surgical intensive care unit of a 650-bed tertiary care hospital. PATIENTS: Patients admitted to the intensive care unit who had any of the following devices in place for more than 24 hrs: endotracheal tube, nasogastric tube, central venous catheter, arterial catheter. MEASUREMENTS AND INTERVENTIONS: Data were collected on the date of placement of tubes and catheters, position of vascular catheters, date of removal, and reason for removal. The study involved three consecutive 6-month periods. At the end of the first and the second periods, information about rates of accidental removal was provided to the physicians and nurses. In addition, the personnel were instructed to be more vigilant and specific measures aimed at reducing the accidental removal were introduced. MAIN RESULTS: In the first period, 289 endotracheal tubes were placed and 13.1% (24.7 per 1000 days) were removed accidentally. In the second and third periods, 17.1% (25.5 per 1000 days) and 11.4% (15.1 per 1000 days) were removed accidentally, respectively. In the first period, 368 nasogastric tubes were placed and 41% (73.9 per 1000 days) were removed accidentally. In both the second and the third period, a significant reduction in the rate of accidental removal was observed (32.4% or 41.2 per 1000 days and 25.8% or 29.8 per 1000 days, respectively). A significant decrease was observed in the rates of accidental removal of central venous catheters from 7.5% (12.4 per 1000 days) in the first period to 3.6% (5.4 per 1000 days) in the second period. The rate of arterial catheters accidentally removed expressed according to the time at risk significantly decreased from 46.5 per 1000 days in the first period to 19.1 per 1000 days in the second period and 25.3 per 1000 days in the third period. CONCLUSIONS: The information provided by the rates of accidental removal expressed by patient-days is helpful to compare results obtained in populations with different times of follow-up. Education of medical personnel and limiting upper-extremity access to within 20 cm from any catheter or tube resulted in a significant reduction of patient-related removal of tubes and catheters.

Catheterization, Central Venous↗
PubMed2000

Systemic hemodynamics, gastric intramucosal PCO2 changes, and outcome in critically ill burn patients.

OBJECTIVES: To define the hemodynamic and gastric intramucosal PCO2 (PiCO2) changes during the first 48 hrs after burn trauma and to analyze their relationship with outcome. DESIGN: Prospective, observational study in a cohort of consecutively admitted critically ill burn patients. SETTING: Intensive care burn unit in a university hospital. PATIENTS: Forty-two patients with burns covering >20% of body surface area or inhalation injury. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Patients were monitored with an oximetric pulmonary arterial catheter and a gastric tonometer to measure PiCO2. The difference between arterial and gastric mucosal PCO2 (P[i-a]CO2) was considered indicative of gastric mucosal hypoxia. Hemodynamic and PiCO2 measurements were performed during the first 48 hrs after admission. Patients suffered burns covering 36.1% +/- 14.3% (mean +/- SD) and 45.3% +/- 21.9% of body surface area (survivors and nonsurvivors, respectively). All patients were successfully resuscitated by conventional standards. Nonsurvivors (n = 16) died a median of 17 days after admission. In univariate analysis, the presence of shock during the resuscitation phase, age, mixed venous pH, P[i-a]CO2, right atrial pressure, pulmonary arterial pressure, pulmonary arterial occlusion pressure, cardiac index, systemic and pulmonary vascular resistance, left ventricular stroke work index, mixed venous oxygen saturation, and systemic oxygen delivery, consumption, and extraction ratio, measured over the first 12 hrs after admission, were significantly (p < .05) different between survivors and nonsurvivors. These differences disappeared after 12 hrs after admission. Multivariate analysis identified age, percentage body surface area burned, and oxygen delivery index (6 hrs after admission) as factors independently associated with a poor outcome. P[i-a]CO2 (12 hrs after admission) was significantly greater in patients with than in those without inhalation injury (17 +/- 13 torr [2.26 +/- 1.73 kPa] vs. 6 +/- 10 torr [0.79 +/- 1.33 kPa]; p = .005). Patients with a P[i-a]CO2 difference (6 hrs after admission) > or =10 torr (1.33 kPa) had a mortality rate of 56% vs. 25% of those patients with <10 torr (p = .044). CONCLUSIONS: Our data indicate that there are hemodynamic and biochemical changes that occur early after burn trauma that are associated with prognosis after an apparently successful resuscitation. Particularly, a hemodynamic profile characterized by systemic acidosis, low systemic blood flow, and systemic and pulmonary vasoconstriction early after trauma is associated with a poor outcome. Additionally, intestinal mucosal acidosis occurs after burn trauma, is influenced by inhalation injury, and is a variable related to outcome.

Adolescent↗
PubMed2000

How is mechanical ventilation employed in the intensive care unit? An international utilization review.

A 1-d point-prevalence study was performed with the aim of describing the characteristics of conventional mechanical ventilation in intensive care units ICUs from North America, South America, Spain, and Portugal. The study involved 412 medical-surgical ICUs and 1,638 patients receiving mechanical ventilation at the moment of the study. The main outcome measures were characterization of the indications for initiation of mechanical ventilation, the artificial airways used to deliver mechanical ventilation, the ventilator modes and settings, and the methods of weaning. The median age of the study patients was 61 yr, and the median duration of mechanical ventilation at the time of the study was 7 d. Common indications for the initiation of mechanical ventilation included acute respiratory failure (66%), acute exacerbation of chronic obstructive pulmonary disease (13%), coma (10%), and neuromuscular disorders (10%). Mechanical ventilation was delivered via an endotracheal tube in 75% of patients, a tracheostomy in 24%, and a facial mask in 1%. Ventilator modes consisted of assist/control ventilation in 47% of patients and 46% were ventilated with synchronized intermittent mandatory ventilation, pressure support, or the combination of both. The median tidal volume setting was 9 ml/kg in patients receiving assist/control and the median setting of pressure support was 18 cm H(2)O. Positive end-expiratory pressure was not employed in 31% of patients. Method of weaning varied considerably from country to country, and even within a country several methods were in use. We conclude that the primary indications for mechanical ventilation and the ventilator settings were remarkably similar across countries, but the selection of modes of mechanical ventilation and methods of weaning varied considerably from country to country.

Data Collection↗
PubMed2000

Thienothiadiazine 2,2-dioxide acyclonucleosides: synthesis and antiviral activity.

The synthesis of acyclonucleosides derived from thieno[3,2-c] and thieno[2,3-c][1,2,6]thiadiazine 2,2-dioxides was achieved following the silylation method. Lipase-mediated methodology was employed for deprotection of the acyclic moieties. The antiviral effects were determined against a broad spectrum of viruses, including cytomegalovirus (CMV) and varicella zoster virus (VZV). Only minor antiviral activity against VZV was observed for those acyclonucleosides carrying a benzyl group.

Antiviral Agents↗
PubMed2000

Effect of different doses of S-adenosyl-L-methionine on paracetamol hepatotoxicity in a mouse model.

This study investigated the hepatoprotective effects of N-acetylcysteine and different doses of S-adenosyl-L-methionine after a single intraperitoneal overdose of paracetamol in mice. Plasma concentrations of paracetamol metabolites were also determined. Female mice (Souris OFl strain) 16 weeks old and weighing 30 g were fasted for 18 h prior to intraperitoneal (i.p.) administration of 375 mg/kg (2.5 mmol/kg) of paracetamol. Experimental subgroups included mice administered paracetamol only (control group), those given of N-acetylcysteine 1 g/kg (6.13 mmol/kg) i.p. immediately after paracetamol overdose (T0) and 6 h after dosing (T6) and those administered S-adenosyl-L-methionine at doses of 20 mg/kg (0.05 mmol/kg) and 1 g/kg (2.5 mmol/kg) i.p. at T0 and T6. Twenty-four hours after paracetamol overdose, mortality and liver necrosis were significantly lower (p < 0.01) in mice treated with 2.5 mmol/kg of S-adenosyl-L-methionine and N-acetylcysteine at T0 as compared with the remaining subgroups. Plasma ALT concentrations were significantly lower (p < 0.01) in mice treated with 2.5 mmol/kg of S-adenosyl-L-methionine than in those given N-acetylcysteine. Plasma concentrations of paracetamol metabolites showed an increase in the glucuronide conjugate and a decrease in the mercapturic acid conjugate in N-acetylcysteine-treated mice and an overall decrease in the conjugation pathway without changes in the oxidative pathway in S-adenosyl-L-methionine-treated animals. We conclude that S-adenosyl-L-methionine at doses of 1 g/kg (2.5 mmol/kg) i.p. was equally effective as 1 g/kg (6.13 mmol/kg) N-acetylcysteine for preventing hepatotoxicity after paracetamol overdose in mice. S-adenosyl-L-methionine may be a therapeutic alternative to N-acetylcysteine as an antidote for poisoning with paracetamol.

Acetaminophen↗
PubMed2000

Prospective randomized trial comparing pressure-controlled ventilation and volume-controlled ventilation in ARDS. For the Spanish Lung Failure Collaborative Group.

STUDY OBJECTIVES: To compare in-hospital mortality of patients with ARDS ventilated with either pressure-controlled ventilation (PCV) or volume-controlled ventilation (VCV) with a square-wave inspiratory flow. DESIGN: : Multicenter and randomized trial. SETTING: Twelve medical-surgical ICUs located in tertiary-care hospitals. PATIENTS: Seventy-nine patients having ARDS, as defined by the American-European Consensus Conference. INTERVENTIONS: Patients were randomly assigned to be ventilated with either PCV (n = 37) or VCV (n = 42). In both instances, inspiratory plateau pressure was limited to < or = 35 cm H(2)O. MEASUREMENTS AND RESULTS: There were no significant differences among the studied groups at the moment of randomization, although there was a trend toward greater renal failure in patients assigned to VCV. Ventilatory settings and blood gases did not significantly differ over time between the two groups. Patients in the VCV group had both a significantly higher in-hospital mortality rate than those in the PCV group (78% vs 51%, respectively) and a higher number of extrapulmonary organ failures (median, 4 vs 2, respectively). The development of renal failure during the study period was also significantly more frequent among VCV patients (64% vs 32%, respectively). Multivariate analysis showed that factors independently associated with an increased mortality rate were the presence of two or more extrapulmonary organ failures (odds ratio [OR], 4.61; 95% confidence interval [CI], 1.38 to 15.40) and acute renal failure (OR, 3.96; 95% CI, 1.10 to 14.28) but not the ventilatory mode used. CONCLUSIONS: The increased number of extrapulmonary organ failures developed in patients of the VCV group was strongly associated with a higher mortality rate. The development of organ failures was probably not related to the ventilatory mode.

Adult↗
PubMed1999

A neurophysiological approach to brainstem reflexes. Blink reflex.

The blink reflex (BR) is a generalised phenomenon in mammals. Its teleological protective eye function is perhaps the reason why the BR can be provoked by a multitude of stimuli. As corneal and glabellar reflexes, BR has an inveterate use in the neurological exploration. Some of its physiopathological aspects were discussed more than 100 years ago, and soon half a century will have passed since the first electrophysiological study was published. This review focuses on the BR elicited by the electrical stimulation of the trigeminal supraorbital nerve, a controlled and reliable model in clinical neurophysiology. The electrically elicited BR is an exteroceptive-nociceptive reflex recorded on the orbicularis oculi muscle and formed by three components: the two principal ones, R1 and R2, of well-known characteristics, and a third, R3, of increasing interest, to which there is wide mention. The trigeminal afferent limb reaches the facial efferent one by means of a long and quite complex central pathway located at the brainstem bulbopontine level. The anatomical substrate and criteria of the rich topographical lesional semiology of the BR are established. The importance of the suprasegmental influences upon the reflex, coming mainly from the cerebral cortex and basal ganglia, as well as the impairment caused by their damage, will be emphasised. Special attention is paid to the relationship between the reflex and the dopaminergic system, and the consequences of its derangement. The methods of habituation and suppression-recovery of the BR are extensively and critically reviewed. These methods measure its excitability and serve in practice for the pathophysiological study of numerous diseases. The relationship of the BR with the spontaneous blinking is considered, and the existence of a primary inhibitory reflex on levator palpebrae muscles, previous to the active reflex response of the orbicularis, is proposed. The electrophysiological characteristics of the glabellar reflex, the corneal reflex, the acoustic, photic and somatosensory provoked BR, the ontogeny, and some of the common factors influencing the reflex, such as sleep, are also discussed. The strategic position of the neural structures of the BR, in an area involved in the gating of the various sensory-motor systems and the relative ease to its evaluation with common methodology used in clinical neurophysiology, makes the BR an essential tool for the diagnosis and pathophysiological insight into an important number of human neurological disorders.

Animals↗
PubMed1999

Modulation of systemic hemodynamics by exogenous L-arginine in normal and bacteremic sheep.

OBJECTIVE: To investigate whether exogenous L-arginine, the substrate for nitric oxide synthase, modulates systemic hemodynamics in sepsis. DESIGN: Prospective, controlled study in a sheep model of sepsis. SETTING: Animal research facility in a university hospital. SUBJECTS: Adult sheep weighing between 35 and 55 kg. INTERVENTIONS: Adult sheep sedated and mechanically ventilated, were monitored with a pulmonary arterial catheter and an ileal tonometer. Four groups of sheep were studied: nonseptic, septic, nonseptic treated with L-arginine, and septic treated with L-arginine. Sepsis was induced by the intravenous administration of Escherichia coli (1.5x10(8) colony-forming units/kg for 30 mins). L-arginine was administered as an intravenous bolus (200 mg/kg for 10 mins) before the septic challenge followed by 200 mg/kg/hr for 300 mins. MEASUREMENTS AND MAIN RESULTS: Sepsis induced a state of acidosis, hyperlactatemia, hypoxemia, and gastric intramucosal acidosis. During the first 30 mins after the septic challenge, there was a decrease in cardiac index and blood pressure, and an increase in systemic vascular resistance. Thereafter, blood pressure returned to baseline values, and systemic vascular resistance fell. Treatment with L-arginine in nonseptic sheep did not induce any biochemical or hemodynamic effect. In septic sheep, treatment with L-arginine was associated with a greater increase in systemic vascular resistance during the first 30 mins, and a more marked decrease in blood pressure and systemic vascular resistance after 180 mins. CONCLUSIONS: Exogenous administration of L-arginine does not induce hemodynamic effects in normal animals, exacerbates the acute vasoconstriction associated with the intravenous infusion of E. coli and potentiates the sepsis-induced vasodilation. Our results suggest that a) nitric oxide production is not constitutively modulated by exogenous L-arginine, b) L-arginine probably enhances the sepsis-induced sympathetic discharge, and c) L-arginine becomes rate-limiting for the formation of nitric oxide at approximately 3 hrs after the initiation of the septic challenge.

Acidosis↗
PubMed1999

Unmasking of the trigemino-accessory reflex in accessory facial anastomosis.

OBJECTIVE: To evaluate the possible blink reflex responses in facial muscles reinnervated by the accessory nerve. METHOD: Eleven patients with a complete facial palsy were submitted to a surgical repair by an accessory facial nerve anastomosis (AFA). In this pathological group, blink reflex was studied by means of percutaneous electrical stimulation of the supraorbital nerve and recording from the orbicularis oculi muscle. A control group comprised seven normal people and seven patients with a complete Bell's facial palsy; in this group, responses on the sternocleidomastoideus (SCM) muscles were studied after supraorbital nerve stimulation. RESULTS: All the patients with AFA showed a consistent degree of facial reinnervation. Ten out of the 11 patients with AFA showed reflex responses; in six, responses were configured by a double component pattern, resembling the R1 and R2 components of the blink reflex; three patients had an R1-like response and one patient showed a unique R2 component. Mean values of latencies were 15.2 (SD 4.6) ms for the R1 and 85.3 (SD 9.6) ms for the R2. In the control group, eight out of 14 people had evidence of reflex responses in the SCM muscles; these were almost exclusively configured by a bilateral late component (mean latency 63.5 (SD15.9) ms) and only one of the subjects showed an early response at 11 ms. CONCLUSION: The trigemino-accessory reflex response in the pathological group was more complex and of a significantly higher incidence than in the control group. These differences could be tentatively explained by a mechanism of synaptic plasticity induced by the impairment of the efferent portion of the reflex. This could unmask the central linking between the trigeminal and the accessory limbs of the reflex. The findings described could be a demonstration of neurobionomic function in the repairing process of the nervous system.

Accessory Nerve↗
PubMed1999

Effect of spontaneous breathing trial duration on outcome of attempts to discontinue mechanical ventilation. Spanish Lung Failure Collaborative Group.

The duration of spontaneous breathing trials before extubation has been set at 2 h in research studies, but the optimal duration is not known. We conducted a prospective, multicenter study involving 526 ventilator-supported patients considered ready for weaning, to compare clinical outcomes for trials of spontaneous breathing with target durations of 30 and 120 min. Of the 270 and 256 patients in the 30- and 120-min trial groups, respectively, 237 (87.8%) and 216 (84.8%), respectively, completed the trial without distress and were extubated (p = 0.32); 32 (13.5%) and 29 (13.4%), respectively, of these patients required reintubation within 48 h. The percentage of patients who remained extubated for 48 h after a spontaneous breathing trial did not differ in the 30- and 120-min trial groups (75.9% versus 73.0%, respectively, p = 0.43). The 30- and 120-min trial groups had similar within-unit mortality rates (13 and 9%, respectively) and in-hospital mortality rates (19 and 18%, respectively). Reintubation was required in 61 (13.5%) patients, and these patients had a higher mortality (20 of 61, 32.8%) than did patients who tolerated extubation (18 of 392, 4.6%) (p < 0.001). Neither measurements of respiratory frequency, heart rate, systolic blood pressure, and oxygen saturation during the trial, nor other functional measurements before the trial discriminated between patients who required reintubation from those who tolerated extubation. In conclusion, after a first trial of spontaneous breathing, successful extubation was achieved equally effectively with trials targeted to last 30 and 120 min.

Aged↗