Reduced air leakage by adjusting the cuff pressure in pediatric laryngeal mask airways during spontaneous ventilation.

BACKGROUND: Optimal inflation of the laryngeal mask airway (LMA) cuff should allow ventilation with low leakage volumes and minimal airway morbidity. Manufacturer's recommendations vary, and clinical end-points have been shown to be associated with cuff hyperinflation and increased leak around the LMA. However, measurement of the intra-cuff pressure of the LMA is not routine in most pediatric institutions, and the optimal intra-cuff pressure in the LMA has not been determined in clinical studies. METHODS: This was a prospective audit in 100 pediatric patients undergoing elective general anesthesia breathing spontaneously via LMA (size 1.5-3). Cuff pressure within the LMA was adjusted using a calibrated pressure gauge to three different values (60, 40, and 20 cmH2O) within the manufacturers' recommended LMA cuff pressure range (< or = 60 cmH2O). Three corresponding inspiratory and expiratory tidal volumes were recorded, and the differences were calculated as the 'leak volume'. RESULTS: Compared with 20 and 60 cmH2O intra-cuff pressure, measured leakage volumes were the lowest at cuff inflation pressures of 40 cmH2O [median (range) 0.42 (0.09-1.00) ml x kg(-1)] in most patients (83%), while 17% of children demonstrated minimally smaller leakages at 20 cmH2O [0.51 (0.11-1.79) ml x kg(-1)]. Maximum leakage values occurred with cuff pressures of 60 cmH2O in all groups [0.65 (0.18-1.27) ml x kg(-1)] and were not associated with the smallest value of air leakage in any patient. CONCLUSION: Using cuff manometry, an intra-cuff pressure of 40 cmH2O was associated with reduced leak around the LMA while higher (60 cmH2O) and lower (20 cmH2O) cuff pressures resulted in higher leak volumes during spontaneous ventilation. In spontaneously breathing children, reducing the intra-cuff pressure of pediatric-sized LMAs even below the manufacturers' recommendations allows ventilation with minimized leakage around the LMA cuff.

Laryngeal mask airways--to inflate or to deflate after insertion?

BACKGROUND: Hyperinflation of the laryngeal mask airway (LMA) cuff is known to be a risk factor for airway morbidity and increased leakage around the LMA. While the manufacturers' recommendation is to inflate the cuff with the maximum recommended volumes and/or to adjust the cuff pressure to <60 cmH2O, cuff pressures below 40 cmH2O have been shown to be associated with a minimal rate of sore throat and minimal leakage. However, it remains to be determined whether inflation or deflation is needed to achieve favorable pressures. Therefore, we assessed the need for cuff-volume adjustment following insertion of the LMA unchanged straight from the sterile packaging in a prospective audit. METHODS: One thousand children (0-16 years) undergoing elective surgery were consecutively included in this quality of care audit. After taking the LMA from its sterile packaging, the LMA cuff was emptied and the amount of air recorded. Then, the same amount of air was returned into the LMA, the LMA was inserted into the patient, and the cuff pressure was measured using a calibrated cuff manometer. RESULTS: Following insertion of the LMA (without further inflation or deflation of the cuff), 20.5% of children had cuff pressures > or = 60 cmH2, while 55.7% had LMA cuff pressures <40 cmH2O. Cuff pressures were also significantly higher in size 1 LMAs (66.6% had cuff pressures > or = 60 cmH2O and 2% <40 cmH2O) compared with all other sizes (P < 0.05). Furthermore, cuff pressures in LMAs with a poly vinyl chloride (PVC) surface were higher compared to LMAs with a silicone surface (65.2% > or = 60 cmH2O and 9.3% <40 cmH2O vs 9% > or = 60 cmH2O and 67.6% <40 cmH2O, respectively). CONCLUSIONS: This study demonstrates that LMAs, particularly when using small-sized LMAs or LMAs with a more rigid PVC surface, need to be deflated following insertion of the device rather than inflated to avoid cuff hyperinflation. Hence, cuff pressures should be measured routinely using a manometer to minimize potential pressure-related airway complications.

Salbutamol premedication in children with a recent respiratory tract infection.

BACKGROUND: Premedication with beta-2 agonists (e.g. salbutamol) is effective in preventing increases in total respiratory resistance and in decreasing the incidence of perioperative bronchospasm in asthmatic children. Because children with recent respiratory tract infection (RTI) exhibit bronchial hyperreactivity similar to that observed in asthmatic children, the use of salbutamol in children with RTI has become popular among pediatric anesthetists for the prevention of perioperative respiratory adverse events (PRAE). In a prospective observational study, we therefore assessed the usefulness of salbutamol premedication on the occurrence of PRAE. METHODS: Results from 600 children (0-16 years) undergoing general anesthesia were analyzed: 200 children with a recent RTI who received preoperative salbutamol 10-30 min prior to surgery, 200 children with a recent RTI without salbutamol premedication, and 200 children without a RTI during the last 4 weeks. All PRAE (laryngospasm, bronchospasm, oxygen desaturation [<95%], severe coughing) were recorded. RESULTS: Children with a recent RTI who received salbutamol demonstrated a significantly reduced incidence of perioperative bronchospasm (5.5% vs 11%, P = 0.0270) and severe coughing (5.5% vs 11.5%, P = 0.0314) compared with children who had an RTI but did not receive salbutamol. However, healthy children presented with the lowest rate (bronchospasm 1.5%, severe coughing 4.5%) of respiratory complications compared with children with a recent RTI independent whether or not they received salbutamol preoperatively. CONCLUSIONS: The results from this audit suggest that children with a history of a recent RTI have significantly less PRAE following a premedication with salbutamol compared with no premedication. Therefore, premedication with salbutamol might be considered in children with recent RTI.

Impact of laryngeal mask airway cuff pressures on the incidence of sore throat in children.

BACKGROUND: Hyperinflation of laryngeal mask airway cuffs can cause harm to the upper airway mainly by exerting high pressures on pharyngeal and laryngeal structures thus impairing mucosal perfusion. Although cuff manometers can be used to guide the monitoring of cuff pressures, their use is not routine in many institutions. In a prospective audit, we assessed the incidence of sore throat following day-case-surgery in relation to the intracuff pressure within the laryngeal mask airway. METHODS: Four hundred children (3-21 years) were consecutively included in this study. The laryngeal mask airway was inflated as deemed necessary by the attending anesthetist. Cuff pressures were measured using a calibrated cuff manometer (Portex Limited, Hythe, Kent, UK, 0-120 cm H2O, pressures exceeding the measurement range were set at 140 cm H2O for statistical purposes) at induction of anesthesia. RESULTS: Forty-five children (11.25%) developed sore throat, 32 (8%) sore neck and 17 (4.25%) sore jaw. Of those that developed sore throat, 56.5% had cuff pressures exceeding >100 cm H2O. In contrast, when cuff pressures were <40 cm H2O, there were no episodes of sore throat, whilst there was only a 4.6% occurrence of sore throat if cuff pressures were between 40-60 cm H2O. CONCLUSION: We have demonstrated that intra cuff pressure in laryngeal mask airways is closely related to the development of sore throat with higher pressures increasing its likelihood. Hence, cuff pressures should be measured routinely using a manometer to minimize the incidence of sore throat.

Sequential clot strength analyses following diclofenac in pediatric adenotonsillectomy.

BACKGROUND: Tonsillectomy is a common pediatric surgical procedure resulting in significant postoperative pain. There is ongoing controversy as to the most satisfactory analgesic regimen. Nonsteroidal antiinflammatory drugs (NSAIDs) are an alternative to opioids in this setting. NSAID use in tonsillectomy has been shown to be opioid sparing in the recovery period and to have similar analgesic effects to opioids in pediatric patients. Because of their nonspecific action on the enzyme cyclo-oxygenase there is potential for increased bleeding which has led many practitioners to avoid NSAIDs completely in this patient population potentially resulting in suboptimal pain control. Our aim in this study was to assess the effect of preoperatively administered diclofenac on the blood clot strength in children undergoing (adeno-) tonsillectomy. METHODS: Twenty patients undergoing (adeno-) tonsillectomy were recruited into this prospective observational study. All patients received 2 mg.kg(-1) of diclofenac rectally immediately preoperatively. Blood was taken for thromboelastograph analysis pre-diclofenac and 1 and 4 h post-diclofenac administration. RESULTS: There was a statistically significant increase in maximal clot strength (MA) at 1 and 4 h after diclofenac. Similarly there was a statistically significant reduction in time to initial fibrin formation (R time) post-diclofenac. There was no primary or secondary hemorrhage. CONCLUSIONS: Diclofenac when given preoperatively does not adversely affect clot strength in the immediate postoperative period when the risk of primary hemorrhage is greatest.

Ocular microtremor during general anesthesia: results of a multicenter trial using automated signal analysis.

Ocular microtremor (OMT) is a fine physiologic tremor of the eye related to neuronal activity in the reticular formation of the brainstem. The frequency of OMT is suppressed by propofol and sevoflurane and predicts the response to command at emergence from anesthesia. Previous studies have relied on post hoc computer analysis of OMT wave forms or on real-time measurements confirmed visually on an oscilloscope. Our overall aim was to evaluate an automated system of OMT signal analysis in a diverse patient population undergoing general anesthesia. In a multicenter trial involving four centers in three countries, we examined the accuracy of OMT to identify the unconscious state and to predict movement in response to airway instrumentation and surgical stimulation. We also tested the effects of neuromuscular blockade and patient position on OMT. We measured OMT continuously by using the closed-eye piezoelectric technique in 214 patients undergoing extracranial surgery with general anesthesia using a variety of anesthetics. OMT decreased at induction in all patients, increased transiently in response to surgical incision or airway instrumentation, and increased at emergence. The frequency of OMT predicted movement in response to laryngeal mask airway insertion and response to command at emergence. Neuromuscular blockade did not affect the frequency of OMT but decreased its amplitude. OMT frequency was unaffected by changes in patient position. We conclude that OMT, measured by an automated signal analysis module, accurately determines the anesthetic state in surgical patients, even during profound neuromuscular blockade and after changes in patient position.