Remifentanil patient-controlled analgesia in labour: six-year audit of outcome data of the RemiPCA SAFE Network (2010-2015).

BACKGROUND: The RemiPCA SAFE Network was established to set standards and monitor maternal and neonatal outcomes when using remifentanil for labour analgesia. The aim of this analysis was to describe the development of the network standard and to report maternal and neonatal outcome data, including severe adverse events. METHODS: Data sets of the RemiPCA SAFE Network database from the initial six consecutive years (2010-2015) were retrospectively analysed. The data were analysed on an annual basis and set in context with changes of the network standard, i.e. adaptations of the network's standard operating procedure. Main outcomes reported are maternal and neonatal data regarding effectiveness and safety, such as satisfaction, need for bag/mask ventilation and/or cardiopulmonary resuscitation. RESULTS: Among 5740 data sets, no need for maternal ventilation or cardiopulmonary resuscitation was registered. Neonatal cardiopulmonary resuscitations, potentially related to remifentanil, occurred in 0.3%. In parallel with adaptations of the network standard, a moderate rate of maternal hypoxia (oxygen saturation <94% in 24.7%) was found, together with a low rate of supplemental oxygen requirement in neonates (5.0%). CONCLUSION: The RemiPCA SAFE Network data show that remifentanil patient-controlled analgesia can be applied safely. There is bias when data from real clinical settings are analysed retrospectively. Notwithstanding, the approach taken by the RemiPCA SAFE Network, with constant, systematic and standardised evaluation of multiple parameters during the course of labour, might identify trends and anomalies and guide the development and application of safety standards, when translating knowledge from scientific trials into clinical practice.

Post-discharge nausea and vomiting after total intravenous anaesthesia and standardised PONV prophylaxis for ambulatory surgery.

BACKGROUND: The incidence of post-discharge nausea and vomiting (PDNV) after ambulatory anaesthesia using total intravenous anaesthesia with a risk-stratified anti-emetic approach is not well documented in the literature. In this study, we outline such an approach. The goal was to achieve an acceptably low rate of PDNV both immediately and the day after surgery. METHODS: With ethics committee approval, adult patients undergoing outpatient surgery received a Propofol-based general anaesthetic plus standardised PONV-prophylaxis corresponding to their Apfel risk-score (0-4); ondansetron (risk-score 2), additional dexamethasone (risk-score 3), and additional droperidol (risk-score 4). On post-operative days one and two, patients scored PDNV and pain (numeric rating scale (NRS); 0 = none at all; 10 = worst imaginable). On post-operative day two, patients indicated the level of interference of PDNV and/or pain with their quality of life. Data are descriptive (%) or mean. RESULTS: There were 222 patients included (age 43 years, 44% female, anaesthesia time 95 min). On the day of surgery, 69.4% of patients did not experience any nausea, 10.4% complained about severe (NRS > 6) nausea, 6.3% experienced vomiting or retching. On the first and second postoperative day, nausea was absent in 88.7% of patients and 97.3%, respectively. Quality of life was impacted (NRS ≥ 4) more by pain (32.8% of cases), than by PDNV (13.6%). CONCLUSION: Acceptably low rates of PDNV were achieved with the proposed standardised approach to PDNV prophylaxis. For almost 90% of patients, PDNV was not an issue the first day after surgery. Pain after discharge was a more common problem.

Factors influencing the level of patients using the internet to gather information before anaesthesia: a single-centre survey of 815 patients in Switzerland : The internet for patient information before anaesthesia.

BACKGROUND: Aim of this study was to identify factors associated with patients using the internet to find information about their upcoming surgery in general, and more specifically about anaesthesia. METHODS: With Ethics committee approval, 1000 consecutive patients seen before elective surgery in the anaesthesia preoperative clinic of a Swiss Level 2 hospital were asked to complete a questionnaire. Primary outcome were patients using the internet to gather any medical information related to their upcoming hospital stay, secondary outcome patients using the internet to gather information regarding the upcoming anaesthesia. Multiple regression was performed to identify independent factors associated with internet use. RESULTS: Eighty-two percent of the patients (n = 815) participated. 97% of those were ASA physical status 1 or 2; 83% (n = 676) had experience with previous anaesthetics, 86% (n = 700) reported to use the internet in general. Overall, about one-third of the participants used the internet to learn more about their medical condition, 26% regarding their upcoming surgical procedure. Only 7% (n = 55) obtained information about the anaesthetic. In multivariate analyses, factors associated with internet use were generally doing so, and planned moderate compared to minor surgery; not using the internet was associated with previous anaesthetic experience. Of those who did not use the Internet to learn about their anaesthetic, 34% indicated that they would have visited a trusted website. CONCLUSION: Only few patients used the internet to obtain information about their upcoming procedure and the anaesthetic part played an even smaller role. However, many patients would have appreciated guidance to find trustworthy internet sites. TRIAL REGISTRATION: German Clinical Trials Register ( DRKS00005434 ; date of registration: 27th December 2013); date of enrolment of first patient: 1st August 2013; study retrospectively registered.

Midazolam plasma concentration after anesthesia premedication in clinical routine - an observational study : Midazolam plasma concentration after anesthesia premedication.

BACKGROUND: Midazolam is commonly used as a pre-anesthesia anxiolytic. It`s elimination may not be fast enough for short procedures. In orally premedicated patients we obtained midazolam plasma concentrations at the end of surgical procedures and compared those to concentrations at anesthesia induction. METHODS: The study was conducted prospectively with consent of the local ethics committee (Ethikkomission Kanton Thurgau, Switzerland) and carried out with written informed consent of each patient. Female patients aged 20 to 60 years undergoing elective procedures with general anesthesia were included, and were divided in two groups according to the planned surgical time: group S (<30 min) and group L (90-120 min), respectively. All patients received 7.5 mg Midazolam po as premedication. Blood samples were drawn at anesthesia induction, and at the end of surgery. Data were compared with t-test (independent samples; significance level p <0.05). RESULTS: Twenty-five patients per group were included. Four patients were excluded from analysis, since midazolam was not detectable in any samples. Time of premedication to the 1st blood sample was not statistically different between groups, neither were Midazolam plasma levels at this time point (p = 0.94). None of the patients from group L (n = 24), but five patients in group S (n = 22) did have a higher plasma level of Midazolam at the end of the case compared to the beginning. CONCLUSIONS: The elimination half-life of oral Midazolam can lead to higher plasma levels at the end of a short procedure compared to those at induction of anesthesia. TRIAL REGISTRATION: German Clinical Trials Register (Deutsches Register Klinischer Studien), DRKS00005429 ; date of registration 3rd January 2014.

Nasotracheal intubation depth in paediatric patients.

BACKGROUND: The aim of this study was to compare intubation depth using the Microcuff paediatric endotracheal tube (PET) placed with the intubation depth mark between the vocal cords with that of different published formulae/recommendations for nasotracheal intubation depth in children. METHODS: Children aged from birth to 10 yr undergoing elective surgery with nasotracheal intubation were included. Tracheal tubes were adjusted according to the intubation depth mark between the vocal cords using direct laryngoscopy. Nasal intubation depth was recorded and the distance 'tube tip to carina' was measured endoscopically. Based on the recorded nasal intubation depth and measured distance 'tube tip to carina', the position of tube tip and cuff was calculated according to six published formulae/recommendations. RESULTS: Seventy-six children were studied. For the Microcuff PET, the median tube tip advancement within the trachea was 52.9% (41.1-73.8%) of tracheal length. The shortest distance from the 'tube tip to carina' was 15 mm for a 3.5 mm internal diameter tube. If the six published formulae/recommendations had been used, this would have resulted in endobronchial tube placement in up to 9.1% of cases, and the tube tip would have been placed above the glottis in up to 2.6% of cases. The upper border of the cuff would have been placed in the subglottic area in up to 42.1% of cases and in a supraglottic position in up to 63.2% of cases. CONCLUSIONS: This study indicates that nasal intubation with the intubation depth mark placed between the vocal cords was superior to formula-based nasotracheal tube positioning. The latter would result in a high rate of endobronchial intubations, excessively high cuff positions and even tracheal extubations.

Tumescent anaesthesia in combination with femoral nerve block for surgery of varicose veins: prilocaine 0.1% versus 0.2%.

OBJECTIVE: Results of a prospective, randomized, double-blinded study about tumescent anaesthesia (TA) in combination with femoral nerve block (FNB) for surgery of varicose veins are reported. The aim is to compare two different concentrations of prilocaine in TA. METHOD: With approval of the ethical committee and informed consent, FNB (nerve stimulation, 20 mL prilocaine 0.75%) was performed followed by TA using prilocaine 0.1% versus 0.2% (groups P0.1 and P0.2). Further medication was standardized. Overall amount of prilocaine was recorded, plasma levels of 20 patients measured regularly. Side-effects, patient satisfaction and pain scores were compared (P < 0.05). RESULTS: Ninety patients were included. In one patient (P0.1), general anaesthesia was necessary. There was no difference in pain scores, need for rescue medication or patient satisfaction. More prilocaine was administered in P0.2 (P < 0.0001) with higher but far below toxic plasma levels. In three patients (P0.2) mild met-haemoglobinaemia was confirmed. CONCLUSION: TA with prilocaine 0.1% in combination with FNB is sufficient to provide high patient satisfaction during varicosis surgery.

Prospective randomized controlled multi-centre trial of cuffed or uncuffed endotracheal tubes in small children.

BACKGROUND: The use of cuffed tracheal tubes (TTs) in small children is still controversial. The aim of this study was to compare post-extubation morbidity and TT exchange rates when using cuffed vs uncuffed tubes in small children. METHODS: Patients aged from birth to 5 yr requiring general anaesthesia with TT intubation were included in 24 European paediatric anaesthesia centres. Patients were prospectively randomized into a cuffed TT group (Microcuff PET) and an uncuffed TT group (Mallinckrodt, Portex, Rüsch, Sheridan). Endpoints were incidence of post-extubation stridor and the number of TT exchanges to find an appropriate-sized tube. For cuffed TTs, minimal cuff pressure required to seal the airway was noted; maximal cuff pressure was limited at 20 cm H(2)O with a pressure release valve. Data are mean (SD). RESULTS: A total of 2246 children were studied (1119/1127 cuffed/uncuffed). The age was 1.93 (1.48) yr in the cuffed and 1.87 (1.45) yr in the uncuffed groups. Post-extubation stridor was noted in 4.4% of patients with cuffed and in 4.7% with uncuffed TTs (P=0.543). TT exchange rate was 2.1% in the cuffed and 30.8% in the uncuffed groups (P<0.0001). Minimal cuff pressure required to seal the trachea was 10.6 (4.3) cm H(2)O. CONCLUSIONS: The use of cuffed TTs in small children provides a reliably sealed airway at cuff pressures of

An intraoperative pre-incision single dose of intravenous ketamine does not have an effect on postoperative analgesic requirements under clinical conditions.

Evidence about the effectiveness of the N-methyl-D-aspartate antagonist ketamine to reduce postoperative acute and long-lasting pain is inconclusive. The aim of this study was to investigate effects of adding an intraoperative, pre-incision single intravenous dose of ketamine to a routine anaesthesia regimen on postoperative analgesic requirements, side-effects and persisting pain up to three months. After obtaining Ethical Committee approval and written informed patient consent, 120 patients were included in this prospective, randomised, double-blinded, placebo-controlled study. Patients were randomised into three groups, receiving 0.15 mg/kg ketamine intravenously, 0.5 mg/kg ketamine intravenously or normal saline in groups low-dose ketamine, moderate-dose ketamine and placebo, respectively. Anaesthesia maintenance, intraoperative pain management and postoperative pain therapy were standardised. The primary study endpoint was consumption of morphine during the first 24 hours after surgery. Three months after surgery, pain scores were assessed. Data were compared by t-test and Kruskall-Wallis test with alpha = 0.05. There was no difference between the groups in the assessed variables. These findings indicate that with the anaesthesia regimen described, and in the doses used, a single intravenous dose of ketamine does not reduce postoperative analgesic requirement or postoperative pain at three months.

In vitro evaluation of the CeVOX continuous central venous oxygenation monitoring system.

We investigated the in vitro performance of the CeVOX system for continuous monitoring of central venous oxygen saturation by spectrophotometry (Pulsion Medical Systems, Munich, Germany). Oxygen inflow into the system was varied, and oxygen saturation values measured by CeVOX were documented. Blood samples were simultaneously taken to assess oxygen saturation by co-oximetry, and values were compared by Bland-Altman analysis. Sixty-six data pairs were obtained at CeVOX and co-oximetry values of 16-99% and 5.5-100%, respectively. Overall, CeVOX values only slightly overestimated co-oximetry values (mean bias +2.4%), but limits of agreement (2 SD of bias) were wide (-11.8 to +16.6%). Saturation measured by CeVOX underestimated that measured by co-oximetry at higher oxygen concentrations and overestimated it at lower oxygen concentrations. There was a nearly linear correlation of the mean bias, suggesting a systematic error. We conclude that the current version of the CeVOX system does not reliably reflect oxygen saturation.

Tracheal tube tip displacement during laparoscopy in children*.

The risk of endobronchial intubation during laparoscopy because of displacement of the tip of the tracheal tube is a well known problem in adults. Laparoscopy in children is increasingly performed, but there are no data available regarding the above problem. We prospectively studied 46 children aged 2 months to 15.7 years (median 4.2 years) undergoing laparoscopy. After tracheal intubation with the Microcuff Pediatric Endotracheal Tube, with the 'intubation depth marking' of the tube at the vocal cords, the distance from the tracheal tube tip to the carina was endoscopically measured with the patient in the neutral position and with 20 degrees head-down tilt, both with and without capnoperitoneum. Maximal displacement of the tip of the tracheal tube tip in cm was 0.5+(0.05xage (years)) for 20 degrees head-down tilt, 0.6+(0.09xage (years)) for capnoperitoneum alone, and 1.2+(0.11xage (years)) for 20 degrees head-down tilt with capnoperitoneum. In no patients did endobronchial intubation occur with the tracheal tube placed according to the intubation depth marking.

An in vitro study of the compliance of paediatric tracheal tube cuffs and tracheal wall pressure.

Cuff volume-pressure curves and cuff pressure-tracheal wall pressure relationships were investigated in eight brands of currently available cuffed, paediatric tracheal tubes with internal diameters of 5.0 mm. Cuff volume-pressure curves were measured with the cuff unrestricted and with the cuff placed within a tracheal model with wall pressure measurements. With the tracheal tube cuffs, unrestricted cuff compliance at 20 cmH(2)O cuff pressure varied between 0.06 and 0.3 ml x cmH(2)O(-1). With the cuff restricted within the model trachea, all tracheal tube cuffs became considerably less compliant (0.01-0.09 ml x cmH(2)O(-1)). We found tracheal wall pressure was similar to the cuff pressure as long as the resulting cuff diameter was sufficiently large freely to drape the inner tracheal wall. We found that, regardless of whether a higher or lower compliant tube cuff was used, cuff hyperinflation uniformly resulted in potentially compromised tracheal mucosal blood flow; cuff pressure monitoring using cuff pressure limitation is therefore strongly recommended.

Clinical evaluation of cuff and tube tip position in a newly designed paediatric preformed oral cuffed tracheal tube.

BACKGROUND: To assess the adequacy of the position of the tracheal tube cuff and tracheal tube tip in the recently introduced preformed oral Microcuff paediatric endotracheal tube (PET) using the manufacturers recommendations for Microcuff tracheal tube size selection. METHODS: With Hospital Ethics Committee approval and informed parental consent, the tracheas of children from birth to adolescence were orally intubated with the preformed oral Microcuff PET. First, the position of the tracheal tube's intubation depth mark in relation to the vocal cords was assessed. Second, the distance 'tracheal tube tip-to-carina' was endoscopically measured with the patient supine and the head in a neutral position and the tube placed with the centre mark at the lower incisors or alveolar ridge. RESULTS: A total of 166 children aged from 0.1 to 16.4 yr (median 5.9 yr) were studied. In five patients the intubation depth mark was above (5 mm each), in 22 patients at the level of and in the remaining 139 patients below the vocal cords. No endobronchial intubation occurred. In four patients the distance 'tracheal tube tip-to-carina' was smaller than the safety margin to prevent endobronchial intubation during head-neck flexion. CONCLUSION: The new oral preformed cuffed tracheal tubes allow safe placement in almost all patients when inserted according to the tube bend. The critically low tube tip and the high cuff positions in a few tubes when placed according to the tube bend requires clinical alertness.

Evaluation of a new recommendation for improved cuffed tracheal tube size selection in infants and small children.

BACKGROUND: The purpose of this study was to evaluate a new recommendation for tracheal tube size selection using second-generation Microcuff paediatric endotracheal tubes (PETs) with optimized outer diameter (OD) of the distal tube. METHODS: With Ethics Committee approval, patients aged from birth to 5 years, requiring general anaesthesia with orotracheal intubation, were included. Tracheal tube sizes were selected as follows: internal diameter (ID) 3.0 mm, birth (if > or =3 kg) to <6 months; ID 3.5 mm, 6 to <18 months; ID 4.0 mm, 18 months to <3 years; ID 4.5 mm, 3 to <5 years. Tracheal tubes with the cuff not inflated were classified as too large if no air leak was obtained at an airway pressure of < or =20 cmH2O. Post-intubation stridor requiring therapy was noted. RESULTS: Three hundred and fifty children were studied. Nine tracheal tubes (2.6%) were too large and had to be exchanged: in patients requiring tracheal tubes of ID 3.0 mm and 3.5 mm, three and four tracheal tubes, respectively, and, in patients requiring tracheal tubes of ID 4.0 mm and 4.5 mm, one tracheal tube in each group. In three patients (0.9%), post-intubation stridor occurred which required therapy. CONCLUSION: The new recommendation presented for the use of second-generation Microcuff PETs with improved OD to ID ratio allows the selection of cuffed tracheal tubes with larger IDs than previously recommended for small children without increased need for tracheal tube exchange or increased incidence of post-intubation stridor in these age groups.

Tracheal tube-tip displacement in children during head-neck movement--a radiological assessment.

BACKGROUND: Aims of this study were to assess the maximum displacement of tracheal tube tip during head-neck movement in children, and to evaluate the appropriateness of the intubation depth marks on the Microcuff Paediatric Endotracheal Tube regarding the risk of inadvertent extubation and endobronchial intubation. METHODS: We studied children, aged from birth to adolescence, undergoing cardiac catheterization. The patients' tracheas were orally intubated and the tracheal tubes positioned with the intubation depth mark at the level of the vocal cords. The tracheal tube tip-to-carina distances were fluoroscopically assessed with the patient supine and the head-neck in 30 degrees flexion, 0 degrees neutral position and 30 degrees extension. RESULTS: One hundred children aged between 0.02 and 16.4 yr (median 5.1 yr) were studied. Maximum tracheal tube-tip displacement after head-neck 30 degrees extension and 30 degrees flexion demonstrated a linear relationship to age [maximal upward tube movement (mm)=0 0.71 x age (yr)+9.9 (R(2)=0.893); maximal downward tube movement (mm)=0.83 x age (yr)+9.3 (R(2)=0.949)]. Maximal tracheal tube-tip downward displacement because of head-neck flexion was more pronounced than upward displacement because of head-neck extension. CONCLUSIONS: The intubation depth marks were appropriate to avoid inadvertent tracheal extubation and endobronchial intubation during head-neck movement in all patients. However, during head-neck extension the tracheal tube cuff may become positioned in the subglottic region and should be re-adjusted when the patient remains in this position for a longer time.

Comparison of tracheal tube cuff diameters with internal transverse diameters of the trachea in children.

BACKGROUND: In this study, we evaluated the ratio of the cuff diameters of the Microcuff paediatric tracheal tube (Microcuff PET, Weinheim, Germany) to fluoroscopically measured internal transverse tracheal diameters in children from birth to adolescence. METHODS: With Institutional Ethics Committee approval and parental consent, we measured the internal transverse tracheal diameters from fluoroscopy images in children undergoing cardiac catheterization requiring general anaesthesia with oro-tracheal intubation. Minimal tracheal sealing pressures were assessed at standardized respirator settings. Internal transverse tracheal diameters were compared with cuff diameters at 20 cmH2O cuff pressure. Linear regression analysis was employed to assess the correlation of tracheal diameters with age, height and weight, and to assess the correlation of the cuff/tracheal diameter ratio with sealing pressures. For all tests, P < 0.05 was considered to be statistically significant. RESULTS: One hundred and forty-five patients were studied (62 girls; 83 boys). Transverse tracheal diameters correlated well with age (r = 0.890; P < 0.0001), height (r = 0.900; P < 0.0001) and weight (r = 0.882; P < 0.0001). Tracheal sealing pressures ranged from 4 to 18 cmH2O. The ratio of the tracheal tube cuff diameter to the internal transverse tracheal diameter ranged from 1.06 in tubes with internal diameters of 6.0 and 4.5 mm to 2.01 in a tube with an internal diameter of 3.5 mm (median, 1.43), and did not correlate with tracheal sealing pressures (r = 0.021, P = 0.7999). CONCLUSIONS: The residual diameters of the Microcuff paediatric tracheal tube cuffs were sufficient to cover the measured internal transverse tracheal diameters of children from birth to adolescence. This allowed the internal tracheal mucosal surface to be draped and the trachea to be sealed at very low cuff pressures.

Outer diameter and shape of paediatric tracheal tube cuffs at higher inflation pressures.

Cuffed tracheal tubes are becoming increasingly popular in paediatric anaesthesia and intensive care medicine. To avoid cuff related complications and airway morbidity, a thorough understanding of cuff volume/pressure behaviour and management is required. In this study, the outer cuff diameter and form stability of the cuff at high cuff pressure were assessed in a series of different paediatric cuffed tracheal tubes with internal diameter of between 3.0 and 5.0 mm. The main findings were that small amounts of inflated air led to a rapid increase in cuff pressure and volume and that the outer cuff diameters increased to 2-2.5 times the age-corresponding internal tracheal diameter following inadvertent syringe inflation. Careful cuff inflation under cuff pressure monitoring and/or automatic cuff pressure release is recommended in paediatric tracheal tube cuffs to prevent airway damage caused by manual inflation, pilot balloon compression and nitrous oxide diffusion.

Nitrous oxide diffusion into tracheal tube cuffs--efficacy of a new prototype cuff pressure release valve.

BACKGROUND: The aim of this study was to evaluate the performance of a new cuff pressure release valve (CPRV), in which the release pressure can be adjusted from 10 to 25 cmH2O, particularly intended to control pressure in paediatric cuffed tracheal tubes and to avoid cuff hyperinflation caused by N2O diffusion. METHODS: In vitro: the PRV was set to 10, 15, 20 or 25 cmH2O release pressure and connected to a cuffed tube placed into a box flushed with 66% N2O in O2. The cuff pressure was monitored with and without CPRV for 60 min. Experiments were performed four times using two different CPRVs. In vivo: with Institutional Review Board approval, CPRV was studied in 50 children undergoing general anaesthesia with tracheal intubation and standardized anaesthesia technique (including 66% N2O in O2) and ventilator settings. Patients were randomized into two groups (with and without CPRV). The cuff pressure baseline was 20 cmH2O and CPRV was set to 25 cmH2O. If the cuff pressure exceeded 25 cmH2O, it was manually released to 20 cmH2O. The numbers of deflations in both groups were noted and compared by Mann-Whitney U-test (P<0.05). RESULTS: In vitro: the cuff pressure exceeded 50 cmH2O after 60 min without CPRV, but did not exceed the settings with CPRV. In vivo: there was no need to manually deflate the cuff in the CPRV group but, in every patient in the control group, three (two to seven) deflating manoeuvres were required within the first hour of anaesthesia (P<0.0001). CONCLUSION: The CPRV allows reliable cuff pressure release at various pressure levels and reliably prevents cuff pressure increases caused by N2O.

Performance of automated air tonometry under hypothermia.

Intestinal tonometry is used during hypothermic cardio-pulmonary bypass surgery to assess splanchnic perfusion. In an in vitro set-up the performance of automated air tonometry (TONOCAP) was tested for normo- and hypothermia. A 14-FG tonometry catheter was built into a testing chamber (100 cm(3)) perfused with blood from a cardio-pulmonary bypass circuit with P(a)co(2) held at 5.6-5.8 kPa (alpha-stat). P(r)co(2) from the balloon of the tonometry catheter was measured at intervals of 10 min at 37 degrees C and at 25 degrees C by the TONOCAP. Bias (precision) of P(r)co(2) - P(a)co(2 alpha-stat) and P(r)co(2) -P(a)co(2 pH-stat) at 37 degrees C blood temperature were low at 0.23 kPa (0.21) each. Tonometrically measured P(r)co(2) at 25 degrees C significantly differed from P(a)co(2 alpha-stat) bias (precision) of 2.00 kPa (0.11) but was similar to P(a)co(2 pH-stat) (0.30 kPa (0.11)). P(r)co(2) values as measured by the TONOCAP represent pH-stat approach. Identical blood gas management (pH- or alpha-stat) should be used for calculation of mucosal-arterial CO(2) difference (P(r-a)co(2) gap) or calculation of intramucosal pH.

Nitrous oxide diffusion into the cuffs of disposable laryngeal mask airways.

The aim of this study was to investigate cuff pressure changes found in disposable size 3 laryngeal mask airways (LMAs) from different manufacturers during nitrous oxide exposure and to compare the results with the re-usable Classic LMA. In an in vitro experiment, laryngeal mask airway cuff pressures starting from a baseline pressure of 40 cm H(2)O were recorded using a pressure transducer for 60 min with the laryngeal mask airway cuff exposed to 66% N(2)O in oxygen. Cuff pressure increases within 5 min of nitrous oxide exposure were > 250% in the Classic LMA and were not significantly different from those found in the Marshall laryngeal mask airway. However, they were significantly greater than those in the Soft Seal, the Unique, the AMBU, and Intersurgical laryngeal mask airways, all of which demonstrated stable cuff pressure levels within the first 5 min. The cuff pressure increase following 60 min of nitrous oxide exposure was 13.0 +/- 1.1 and 14.6 +/- 0.7 cm H(2)O in the Intersurgical and Unique laryngeal mask airways, respectively, which was significantly lower than the cuff pressure increase in the Soft Seal and in the Ambu laryngeal mask airways (28.3 +/- 2.9 and 30.9 +/- 1.2 cm H(2)O, respectively). Unlike the re-usable Classic LMA and the disposable Marshall laryngeal mask airway, which have silicone cuffs, the disposable Ambu, Intersurgical, Portex Soft Seal and Unique laryngeal mask airways have cuffs constructed from PVC, which seems to be less susceptible to hyperinflation caused by nitrous oxide diffusion.

Fit and seal characteristics of a new paediatric tracheal tube with high volume-low pressure polyurethane cuff.

BACKGROUND: To evaluate a new paediatric tracheal tube (Microcuff, Weinheim, Germany) with an ultrathin high volume-low pressure polyurethane cuff. METHODS: With approval of the Hospital Ethics Committee tracheas of children undergoing general anaesthesia were intubated using a Microcuff tube. Tube sizes were selected according to: internal diameter (mm) = age/4 + 3.5 in children aged > or = 2 years. In newborns (> or = 3 kg) < or = 1 year, ID 3.0-mm tubes, and in children from 1 to 2 years, internal diameter 3.5-mm tubes were used. Tubes were classified too large if no air leakage was obtained at an airway pressure of 20 cm H2O with the cuff not inflated. Sealing pressure was assessed by auscultation. Post-extubation croup requiring therapy was noted. RESULTS: Five-hundred children were studied. In eight children the tubes were too large. Sealing pressure was 9.7 +/- 2.5 cm H2O (4-20). In two patients postextubation croup required singular short-term therapy. CONCLUSIONS: Microcuff paediatric tracheal tubes provided tracheal sealing with cuff pressures considerably lower than usually accepted. The rate of tube exchange was very low (1.6%), as was the rate of airway morbidity (croup requiring therapy; 0.4%).