Thomas A. Crozier

Novices ventilate and intubate quicker and safer via intubating laryngeal mask than by conventional bag-mask ventilation and laryngoscopy

Background:Because airway management plays a key role in emergency medical care, methods other than laryngoscopic tracheal intubation (LG-TI) are being sought for inadequately experienced personnel. This study compares success rates for ventilation and intubation via the intubating laryngeal mask (ILMA-V/ILMA-TI) with those via bag–mask ventilation and laryngoscopic intubation (BM-V/LG-TI). Methods:In a prospective, randomized, crossover study, 30 final-year medical students, all with no experience in airway management, were requested to manage anesthetized patients who seemed normal on routine airway examination. Each participant was asked to intubate a total of six patients, three with each technique, in a randomly assigned order. A task not completed after two 60-s attempts was recorded as a failure, and the technique was switched. Results:The success rate with ILMA-V was significantly higher (97.8% vs. 85.6%; P < 0.05), and ventilation was established more rapidly with ILMA-V (35.6 ± 8.0 vs. 44.3 ± 10.8 s; P < 0.01). Intubation was successful more often with ILMA-TI (92.2% vs. 40.0%; P < 0.01). The time needed to achieve tracheal intubation was significantly shorter with ILMA-TI (45.7 ± 14.8 vs. 89.1 ± 23.3 s; P < 0.01). After failed LG-TI, ILMA-V was successful in all patients, and ILMA-TI was successful in 28 of 33 patients. Conversely, after failed ILMA-TI, BM-V was possible in all patients, and LG-TI was possible in 1 of 5 patients. Conclusion:Medical students were more successful with ILMA-V/ILMA-TI than with BM-V/LG-TI. ILMA-TI can be successfully used when LG-TI has failed, but not vice versa. These results suggest that training programs should extend the ILMA to conventional airway management techniques for paramedical and medical personnel with little experience in airway management.

Surgical pleth index-guided remifentanil administration reduces remifentanil and propofol consumption and shortens recovery times in outpatient anaesthesia

BACKGROUND The surgical pleth index (SPI) is an index based on changes in plethysmographic characteristics that correlate with the balance between the sympathetic and parasympathetic nervous system. It has been proposed as a measure of the balance between nociception and anti-nociception. The goal of this study was to test whether it could be used to titrate remifentanil in day-case anaesthesia. METHODS A total of 170 outpatients were given total i.v. anaesthesia with propofol and remifentanil. The patients were randomized to have the remifentanil dose either adjusted according to the SPI (SPI group) or to clinical parameters (control group). The propofol dose was adjusted according to entropy in both groups. The consumption of anaesthetic drugs, recovery times, and complications were compared. RESULTS The mean [standard deviation (SD)] remifentanil and propofol infusion rates in the SPI and control groups were 0.06 (0.04) vs 0.08 (0.05) µg kg(-1) min(-1) and 6.0 (2.1) vs 7.5 (2.2) mg kg(-1) h(-1), respectively (both P<0.05). The mean (SD) times to eye opening were -0.08 (4.4) and 3.5 (4.3) min and to extubation were 1.2 (4.4) and 4.4 (4.5) min in the SPI and control groups, respectively (both P<0.05). There was no difference between the groups with regard to satisfaction with the anaesthetic or intensity of postoperative pain. No patient reported intraoperative awareness. CONCLUSIONS Adjusting the remifentanil dosage according to the SPI in outpatient anaesthesia reduced the consumption of both remifentanil and propofol and resulted in faster recovery.

Randomized comparison of the i-gel™, the LMA Supreme™, and the Laryngeal Tube Suction-D using clinical and fibreoptic assessments in elective patients

BackgroundThe i-gel™, LMA-Supreme (LMA-S) and Laryngeal Tube Suction-D (LTS-D) are single-use supraglottic airway devices with an inbuilt drainage channel. We compared them with regard to their position in situ as well as to clinical performance data during elective surgery.MethodsProspective, randomized, comparative study of three groups of 40 elective surgical patients each. Speed of insertion and success rates, leak pressures (LP) at different cuff pressures, dynamic airway compliance, and signs of postoperative airway morbidity were recorded. Fibreoptic evaluation was used to determine the devices’ position in situ.ResultsLeak pressures were similar (i-gel™ 25.9, LMA-S 27.1, LTS-D 24.0 cmH2O; the latter two at 60 cmH2O cuff pressure) as were insertion times (i-gel™ 10, LMA-S 11, LTS-D 14 sec). LP of the LMA-S was higher than that of the LTS-D at lower cuff pressures (p <0.05). Insertion success rates differed significantly: i-gel™ 95%, LMA-S 95%, LTS-D 70% (p <0.05). The fibreoptically assessed position was more frequently suboptimal with the LTS-D but this was not associated with impaired ventilation. Dynamic airway compliance was highest with the i-gel™ and lowest with the LTS-D (p <0.05). Airway morbidity was more pronounced with the LTS-D (p <0.01).ConclusionAll devices were suitable for ventilating the patients’ lungs during elective surgery.Trial registrationGerman Clinical Trial Register DRKS00000760

Carbon dioxide absorption during extraperitoneal and transperitoneal endoscopic hernioplasty.

Transabdominal preperitoneal (TAPP) or total extraperitoneal (TEP) hernioplasty are probably associated with differing degrees of CO2 absorption which can influence anesthetic management and perioperative morbidity. We studied 20 patients with either TAPP or TEP for perioperative CO2 absorption (calculated from CO2 elimination and metabolic CO2 production) and ventilatory changes required to maintain normocapnia (blood gas analyses). CO2 absorption reached plateau values in the TAPP group, but increased over time in the TEP group. Median CO2 absorption during insufflation was 61 mL/min (range 43–78) for TAPP and 114 mL/min (range 75–178) for TEP, with a maximum of 114 mL/min (range 75–178) for TAPP and 258 mL/min (range 112–585) for TEP. Median minute ventilation (&OV0312;E) required for maintaining normocapnia was 9.5 L/min (range 7.7–11.5) for TAPP and 12.9 L/min (range 9.0–22.6) for TEP (P < 0.01). Seven patients in the TEP group required over 18 L/min &OV0312;E, although no patient in the TAPP group required more than 14 L/min &OV0312;E. All patients in the TEP group had significant subcutaneous emphysema resulting in one case of delayed tracheal extubation. We conclude that CO2 absorption is consistently less with TAPP. Implications The greater magnitude of carbon dioxide absorption during total extraperitoneal hernioplasty puts an additional load on the lungs and could pose a risk for patients with chronic lung disease who might be unable to eliminate excess carbon dixoide.

Effect of buspirone on thermal sensory and pain thresholds in human volunteers

BackgroundBuspirone is a partial 5-HT1A receptor agonist. Animal studies have shown that modulation of serotoninergic transmission at the 5-HT1A receptor can induce analgesia in acute pain models. However, no studies have been published so far on the effects of serotonin receptor agonists on pain perception in humans.MethodsThe effects of buspirone (30 mg p.o.) on thermal sensory and pain thresholds were investigated in twelve female volunteers (26 ± 2 yrs) in a prospective, randomized, double-blind, double-dummy, placebo-controlled study with morphine (10 mg i.v.) as positive control.ResultsMorphine significantly increased the heat pain detection threshold (ΔT: placebo 1.0°C and 1.3°C, p < 0.05) at 60 minutes. Buspirone caused mild sedation in six participants at 60 minutes, but was without effect on any of the measured parameters.ConclusionBuspirone in the maximal recommended dose was without significant effect on thermal pain. However, as it is only a partial agonist at the 5-HT1A receptor and also acts on other receptor types, the negative results of the present study do not rule out a possible analgesic effect of more specific 5-HT1A receptor agonists.

Accuracy of prehospital diagnoses by emergency physicians: comparison with discharge diagnosis.

Objective A correct prehospital diagnosis of emergency patients is crucial as it determines initial treatment, admitting specialty, and subsequent treatment. We evaluated the diagnostic accuracy of emergency physicians. Methods All patients seen by six emergency physicians staffing the local emergency ambulance and rescue helicopter services during an 8-month period were studied. The ambulance and helicopter physicians had 3 and 4 years, respectively, training in anesthesia and intensive care medicine. The admission diagnoses were compared with the discharge diagnoses for agreement. Time of day of the emergency call, patients’ age, and sex, living conditions, and presenting symptoms were evaluated as contributing factors. Results Three hundred and fifty-five ambulance and 241 helicopter deployment protocols were analyzed. The overall degree of agreement between initial and discharge diagnoses was 90.1% with no difference attributable to years of experience. The lowest agreement rate was seen in neurological disorders (81.5%), with a postictal state after an unobserved seizure often being diagnosed as a cerebrovascular accident. Inability to obtain a complete medical history (e.g. elderly patients, patients in nursing homes, neurological impairment) was associated with a lower agreement rate between initial and discharge diagnoses (P<0.05). Conclusion Medical history, physical examination, ECG, and blood glucose enabled a correct diagnosis in most cases, but some were impossible to resolve without further technical and laboratory investigations. Only a few were definitively incorrect. A detailed medical history is essential. Neurological disorders can present with misleading symptoms and when the diagnosis is not clear it is better to assume the worst case.

EFFECT OF THERMODE APPLICATION PRESSURE ON THERMAL THRESHOLD DETECTION

Studies using quantitative sensory testing (QST) often present incongruent results due to intra‐ and intersubject as well as interobserver variability which limit widespread use of the technique. Eliminating or reducing the factors responsible for this variability is of great interest, as it increases reliability and reproducibility of QST. Thermal sensory threshold determination is a crucial part of QST. It was previously suggested that the pressure of the thermode on the skin could influence measurements. To verify this, we developed a new thermode with a built‐in pressure sensor. Thresholds obtained with this thermode were compared to those obtained with a commercially available thermotesting device (Medoc TSA‐II). Heat detection and heat pain detection thresholds were higher, and cold detection thresholds were lower when measured with our thermode than they were with the Medoc thermode. Cold pain detection thresholds did not differ between the thermodes. Analysis of the heat transfer capacity of the thermodes indicated that the material of the skin contact surface of the thermode may play a role in these shifts in threshold values. Altering the thermode pressure on the skin did not affect the thermal thresholds. Furthermore, the intrasubject variability of the measurements (minimal‐to‐maximal range of measured threshold values in individual subjects) was also not influenced by the pressure with which the thermode was attached to the skin. Our results suggest that the pressure with which the thermode is attached to the skin does not significantly affect the intra‐ and intersubject reproducibility of the thermal sensory threshold measurements. Muscle Nerve, 2008

Effects of pulmonary acid aspiration on the lungs and extra-pulmonary organs: a randomized study in pigs

IntroductionThere is mounting evidence that injury to one organ causes indirect damage to other organ systems with increased morbidity and mortality. The aim of this study was to determine the effects of acid aspiration pneumonitis (AAP) on extrapulmonary organs and to test the hypothesis that these could be due to circulatory depression or hypoxemia.MethodsMechanically ventilated anesthetized pigs were randomized to receive intrabronchial instillation of hydrochloric acid (n = 7) or no treatment (n = 7). Hydrochloric acid (0.1 N, pH 1.1, 2.5 ml/kg BW) was instilled into the lungs during the inspiratory phase of ventilation. Hemodynamics, respiratory function and computer tomography (CT) scans of lung and brain were followed over a four-hour period. Tissue samples of lung, heart, liver, kidney and hippocampus were collected at the end of the experiment.ResultsAcid instillation caused pulmonary edema, measured as increased extravascular lung water index (ELWI), impaired gas exchange and increased mean pulmonary artery pressure. Gas exchange tended to improve during the course of the study, despite increasing ELWI. In AAP animals compared to controls we found: a) cardiac leukocyte infiltration and necrosis in the conduction system and myocardium; b) lymphocyte infiltration in the liver, spreading from the periportal zone with prominent areas of necrosis; c) renal inflammation with lymphocyte infiltration, edema and necrosis in the proximal and distal tubules; and d) a tendency towards more severe hippocampal damage (P > 0.05).ConclusionsAcid aspiration pneumonitis induces extrapulmonary organ injury. Circulatory depression and hypoxemia are unlikely causative factors. ELWI is a sensitive bedside parameter of early lung damage.

A comparison between the GlideScope® classic and GlideScope® direct video laryngoscopes and direct laryngoscopy for nasotracheal intubation.

DESIGN Prospective, randomized, clinical trial. SETTING University hospital operation room. PATIENTS 104 patients scheduled for elective dental or maxillofacial surgery were randomized to two groups: GlideScope® classic (GSc) and GlideScope® direct (GSd). INTERVENTIONS We compared the video laryngoscopes GSc and GSd with each other and with direct laryngoscopy (DL) for nasotracheal intubation with regard to visualization of the glottis, intubation success rate, and required time for and ease of intubation. The aim of the study was to determine whether the use of the video monitor alone reduced the difficulty of nasotracheal intubation, and also to investigate whether the GSc, with its blade designed for difficult airways, had an additional advantage over the video-assisted Macintosh blade (GSd). In both groups the investigators first performed laryngoscopy using the GSd blade, first with the monitor concealed and then with it visible. In the GSd group the tube was then inserted into the trachea with the video monitor screen visible. In the GSc group, the GSd blade was exchanged for the GSc blade, which was then used when inserting the tube with the screen visible. RESULTS The success rates and the times required for the video-assisted nasotracheal intubation did not differ significantly between the groups. A better view was obtained more often in the GSc group. In both groups there was a significant difference between direct laryngoscopy and the video-assisted intubation technique. Overall, using the video monitor improved the C-L scores by one grade in 52% and by two grades in 11% of the patients. CONCLUSIONS Video laryngoscopes increase the ease of nasotracheal intubation. The GSc blade might provide a better view of the laryngeal structures in case of a difficult airway than the GSd blade. Video laryngoscopy per se gives a better view of the glottis than direct laryngoscopy.

Bag-mask ventilation and direct laryngoscopy versus intubating laryngeal mask airway: a manikin study of hands-on times during cardiopulmonary resuscitation.

Objectives The percentage of hands-on time during cardiopulmonary resuscitation is a major determinant of patient outcome. We hypothesized that airway management with the intubating laryngeal mask airway (ILMA) would give greater hands-on time than with bag-mask ventilation (BMV), followed by direct laryngoscopy (DL), particularly in difficult-to-manage airways. Participants and methods Thirty paramedics and 40 medical students performed four standardized, 6-min cardiopulmonary resuscitation scenarios with the SimMan3G in a random sequence. These were normal and difficult-to-manage airways using either BMV+DL or ILMA. Results The time to the first successful ventilation was significantly longer with the ILMA (P<0.001). Hands-on time was lower for the ILMA after 2 min (67±8 vs. 81±8 s for BMV+DL, P<0.001), but was then significantly greater from the third minute onward (115±11 vs. 104±9 s for BMV+DL, P<0.001). The success rate of the first intubation attempt was higher and the time to ET placement was shorter with the ILMA, especially in the difficult-to-manage airway (P<0.001). Conclusion In this manikin-based study, hands-on time was greater with the ILMA than with BMV+DL. The ILMA was particularly useful in increasing hands-on times in the difficult-to-manage airway.