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Biomedical subjects

M Lopez-Gil

Publications and source records attributed to M Lopez-Gil.

9 recordsLinked to original sources
PubMed2001

Bundle-branch reentry and the postpacing interval after entrainment by right ventricular apex stimulation: a new approach to elucidate the mechanism of wide-QRS-complex tachycardia with atrioventricular dissociation.

BACKGROUND: Diagnosis of bundle-branch reentry ventricular tachycardia (BBR-VT) by the standard approach is challenging, and this may lead to nonrecognition of this tachycardia mechanism. Because the postpacing interval (PPI) after entrainment has been correlated with the distance from the pacing site to the reentrant circuit, BBR-VT entrainment by pacing from the right ventricular apex (RVA) should result in a PPI similar to the tachycardia cycle length (TCL). This factor may differentiate BBR-VT from other mechanisms of wide-QRS-complex tachycardia with AV dissociation, such as myocardial reentrant VT (MR-VT) or AV nodal reentrant tachycardia (AVNRT), in which the circuit is usually located away from the RVA. METHODS AND RESULTS: Transient entrainment by RVA pacing was attempted in 18 consecutive BBR-VTs and finally achieved in 13. Results were compared with those found in 59 consecutive MR-VTs and 50 consecutive AVNRTs. The mean PPI-TCL difference was significantly (P:<0.0001) shorter in the BBR-VT group (9+/-11 ms) than in the MR-VT (109+/-48 ms) and the AVNRT (150+/-29 ms) groups. No BBR-VT showed a PPI-TCL >30 ms (range -12 to 24 ms). Except for 2 MR-VTs, no MR-VT (range 21 to 211 ms) or AVNRT (range 100 to 215 ms) showed a PPI-TCL <30 ms. CONCLUSIONS: A PPI-TCL >30 ms, after entrainment by RVA stimulation, makes BBR-VT unlikely. Conversely, a PPI-TCL <30 ms is suggestive of BBR-VT but should lead to further investigation by use of conventional criteria.

Bundle-Branch Block↗
PubMed2001

A comparison of four methods for assessing oropharyngeal leak pressure with the laryngeal mask airway (LMA) in paediatric patients.

BACKGROUND: This study compares four tests for assessing oropharyngeal leak pressure with the laryngeal mask airway (LMA). We tested the hypothesis that the oropharyngeal leak pressure and interobserver reliability differs between tests. METHODS: Eighty paralysed anaesthetized paediatric patients (weight 10-30 kg) were studied with the intracuff pressure set at 60 cmH2O. Four different oropharyngeal leak pressure tests were performed in random order on each patient by two observers blinded to each other's measurements. Test 1 involved detection of an audible noise. Test 2 involved detection of endtidal CO2 in the oral cavity. Test 3 involved observation of the aneroid manometer dial as the pressure increased and noting the airway pressure at which the dial reaches stability. Test 4 involved detection of an audible noise by neck stethoscopy. RESULTS: The mean oropharyngeal leak pressure was 12.5 cmH2O and was similar between tests. The intraclass correlation coefficient was 0.99 for all tests and was classed as excellent. CONCLUSIONS: We conclude that all four tests provide accurate and reliable information about oropharyngeal leak pressure in children.

Air Pressure↗
PubMed1999

Preliminary evaluation of a new prototype laryngeal mask in children.

We have assessed a prototype laryngeal mask airway (pLMA) in 50 anaesthetized children for ease of insertion, oropharyngeal leak pressures, gastric insufflation and fibreoptic position. The pLMA has a second smaller mask, which rests against the upper oesophageal sphincter, and a second cuff to increase the seal pressure of the glottic mask. All insertions were graded as easy and an effective airway was achieved in all patients. Oropharyngeal leak pressure was > 40 cm H2O in 49 of 50 patients. Gastric insufflation was not detected by epigastric auscultation. In 46 of 50 patients, the vocal cords were seen via a fibreoptic laryngoscope. One patient regurgitated clear fluid, but aspiration did not occur. On removal, blood staining was detected in three of 50 children. We conclude that the pLMA was easy to insert, facilitated high airway pressure ventilation and may provide some protection against gastric insufflation.

Air Pressure↗
PubMed1996

Laryngeal mask airway in pediatric practice: a prospective study of skill acquisition by anesthesia residents.

BACKGROUND: A prospective study was conducted to determine the rate of skill acquisition with the laryngeal mask airway in pediatric anesthesiology practice. The aim of the study was to provide information about the amount of supervised training required before satisfactory levels of skill were achieved. METHODS: Eight anesthesia residents in their third year of training with no prior experience using the laryngeal mask airway were observed using the device in 75 pediatric patients each (600 patients in total). Residents were given standardized guidelines for laryngeal mask airway usage in accordance with the manufacturer's recommendations and followed a predetermined protocol for anesthetic management. Induction was achieved with propofol followed by either a propofol infusion or isoflurane and either controlled or spontaneous ventilation as clinically indicated. Predefined major and minor problems were documented during the induction, maintenance, and recovery phases of anesthesia by a randomly selected supervising consultant trained in the study protocol and problem definitions. RESULTS: The total number of problems was 189 occurring in 121 children. Fifty-five children had one problem, sixty-four children had two problems, and two children had three problems. Of the problems, 77 were major and 112 were minor. The problem rate per patient for overall, major, and minor problems was 31.5%, 12.8%, and 18.7%, respectively. The problem rate comparing the first to last epochs of 15 uses decreased from 62% to 2% for overall problems, 23% to 2% for major problems, and 39 to 1% for minor problems. The residents with the most problems in the final epoch had problem rates of less than 10% after 60 uses. There was a significant decrease in the overall problem rate for induction, maintenance, and recovery (P < 0.05). The major problem rate decreased significantly for induction and maintenance (p < 0.05), but not for recovery. The minor problem rate decreased significantly for induction and recovery (P < 0.05). CONCLUSIONS: This study confirms that there is a rapid improvement in laryngeal mask airway skills when the standard recommended technique is employed and that a low problem rate can be achieved within 75 uses. Pediatric anesthesiologists with problem rates greater than 10% should determine if they are using the device suboptimally.

Adolescent↗
PubMed1996

Safety and efficacy of the laryngeal mask airway. A prospective survey of 1400 children.

A survey of laryngeal mask airway usage in 1400 infants and children by ten trainee anaesthetists was undertaken to provide information about insertion and complication rates using the standard insertion technique and a limited range of standardised anaesthetic techniques. Placement was successful in 90% (1258/1400) at the first attempt, 8% (112/1400) at the second attempt and 2% (29/1400) required an alternative technique of insertion. One patient vomited during insertion and the procedure was abandoned, but aspiration did not occur. The overall problem rate was 11.5% and there were significantly more problems during induction of anaesthesia (p < 0.02). Oxygen saturation decreased below 90% briefly on 23 occasions (1.7%). The incidence of problems was unrelated to the mode of ventilation, or whether isoflurane or total intravenous anaesthesia with propofol was used for maintenance. Most problems came with use of the size 1 laryngeal mask (p < 0.001). The subspecialty with the highest problem rate was ear, nose and throat surgery (p < 0.001). There was a significant decrease in problems with increasing experience (p < 0.001). There was no major morbidity associated with use of the device. We conclude that the laryngeal mask provides a safe and effective form of airway management for infants and children in the hands of supervised anaesthesia trainees both for spontaneous and controlled ventilation using either isoflurane or total intravenous anaesthesia.

Adolescent↗
PubMed1996

Radiofrequency ablation of atrial flutter.

Activation mapping in common atrial flutter has shown circular (reentrant) activation of the right atrium around anatomic structures and areas of functional block. The direction of rotation is counterclockwise (in a frontal view), and in the low right atrium the myocardium between the inferior vena cava (IVC) and the tricuspid valve (TV) is critical to close the activation circle. The circuit can be interrupted by radiofrequency ablation of the myocardium between the TV and the IVC, and, in some cases, by ablation between the coronary sinus and TV. Flutter interruption does not mean complete isthmus ablation, as it may remain inducible, requiring further ablation. Despite attaining noninducibility, flutter may recur, and new procedures may be needed for complete ablation. Atrial fibrillation occurs in up to 30% of the cases during follow-up but is generally well controlled with antiarrhythmic drugs that were ineffective in treating flutter before ablation. Some noncommon atrial flutters show circular right atrial activation in a reversed (clockwise) direction, with the same critical areas in the low right atrium, and in these isthmus ablation is effective. Other noncommon flutters have different substrates in the right or left atrium, and mapping has to define specific critical isthmuses as ablation targets in each case. Left atrial flutter circuits remain inaccessible to ablation.

Atrial Fibrillation↗
PubMed1986

Fragmented electrograms and continuous electrical activity in atrial flutter.

Multiple endocardial bipolar electrograms were recorded in 13 patients with atrial flutter (AF) to locate areas of fragmented electrical activity. Stable fragmentation patterns were found in each case, covering between 36% and 100% of the flutter cycle. Double or triple spike patterns were common. The direction of atrial activation was approximately defined in 11 patients, and in all of them at least part of the areas showing fragmentation was included in the circuit. In 1 patient an area of continuous electrical activity was found. AF circuits appeared to be included in the right atrium in 12 patients and in the left atrium in 1 patient. During atrial stimulation changes in fragmented electrograms coincided with changes in AF pattern before its interruption, while restoration of stable AF after stimulation was accompanied by reappearance of previous stable fragmented electrograms. In 6 patients electrograms were recorded after sinus rhythm was reestablished, and all showed marked decreases or disappearance of fragmentation. It is concluded that fragmented electrograms are often found in AF and may be related to abnormal local conduction in relation to the reentrant activation circuits.

Adult↗
PubMed1986

Effects of intravenous ajmaline on atrial excitability and conduction in man.

Slow conduction of early extrastimuli and short refractory periods are some of the factors underlying atrial fibrillation in man. In order to study the effect of ajmaline, a class I antiarrhythmic agent, on these variables, we have performed electrophysiologic studies in 13 patients with and without atrial arrhythmias, before and after the intravenous administration of 1 mg kg-1 of ajmaline chlorhydrate. During paced rhythm with a 600 ms cycle length, extrastimuli were applied to the right atrial appendage, and conduction to the low septal right atrium and the coronary sinus were measured. Ajmaline prolonged P wave duration from 111 +/- 15 to 140 +/- 24 ms (P less than 0.001), conduction of baseline stimuli to low septal right atrium from 69 +/- 14 to 95 +/- 21 ms (P less than 0.001) and to coronary sinus from 127 +/- 18 to 165 +/- 29 ms (P less than 0.001). Atrial effective refractory period increased from 207 +/- 23 to 255 +/- 27 ms (P less than 0.001). Maximum conduction delay of early extrastimuli decreased at the low septal right atrium from 43 +/- 22 to 29 +/- 16 ms (P less than 0.25) and at the coronary sinus from 47 +/- 22 to 21 +/- 14 ms (P less than 0.001). These results show interesting electrophysiologic effects of ajmaline on atrial tissue, with reversion of some of the abnormalities underlying atrial fibrillation, and suggest an antiarrhythmic effect.

Ajmaline↗