The Airtraq as a rescue airway device following failed direct laryngoscopy: a case series

We report the successful use of the Airtraq as a rescue device following failed direct laryngoscopy, in patients deemed at increased risk for difficult tracheal intubation. In a series of seven patients, repeated attempts at direct laryngoscopy with the Macintosh blade, and the use of manoeuvres to aid intubation, such as the gum elastic bougie placement, were unsuccessful. In contrast, with the Airtraq device, each patient's trachea was successfully intubated on the first attempt. This report underlines the utility of the Airtraq device in these patients.

Recovery of older patients undergoing ambulatory anaesthesia with isoflurane or sevoflurane

BACKGROUND

Delayed recovery of cognitive function is a well-recognized phenomenon in older patients. The potential for the volatile anaesthetic used to contribute to alterations in postoperative cognitive function in older patients following minor surgical procedures has not been determined. We compared emergence from isoflurane and sevoflurane anaesthesia in older surgical patients undergoing urological procedures of short duration.

METHODS

Seventy-one patients, 60 yr of age or older, undergoing anaesthesia expected to last less than 60 min for ambulatory surgery, were randomly assigned to receive isoflurane or sevoflurane. A standardized anaesthetic protocol was used, with intravenous fentanyl 1 microg kg(-1) and propofol 1.5-2.0 mg kg(-1) administered to induce anaesthesia. Anaesthesia was maintained with either sevoflurane or isoflurane in 65% nitrous oxide and oxygen. Early and intermediate recovery times were recorded. The Mini Mental State Examination and digit repetition forwards and backwards were administered at baseline, and at 1, 3 and 6 h postoperatively, to assess cognitive function.

RESULTS

There were no between-group differences in (sevoflurane vs. isoflurane, mean +/- standard error of the mean) times to removal of the laryngeal mask airway (7.7 +/- 0.6 vs. 7.1 +/- 0.4 min), verbal response time (10.1 +/- 0.7 vs. 9.9 +/- 0.7 min) and orientation (12.1 +/- 0.7 vs. 12.1 +/- 0.7 min). Intermediate recovery, as measured by time to readiness for discharge from the post anaesthesia care unit (44.9 +/- 1.5 vs. 44.3 +/- 1.5 min), was similar in the two groups. Postoperative indices of cognitive function and attention were comparably reduced at 1 h, but returned to baseline in both groups at 6 h.

CONCLUSIONS

Isoflurane and sevoflurane anaesthesia resulted in similar clinical and neurocognitive recovery profiles in older patients undergoing ambulatory surgical procedures of short duration.

Retention of tracheal intubation skills by novice personnel: a comparison of the Airtraq�and Macintosh laryngoscopes

Direct laryngoscopic tracheal intubation is a potentially lifesaving manoeuvre, but it is a difficult skill to acquire and to maintain. These difficulties are exacerbated if the opportunities to utilise this skill are infrequent, and by the fact that the consequences of poorly performed intubation attempts may be severe. Novice users find the Airtraq laryngoscope easier to use than the conventional Macintosh laryngoscope. We therefore wished to determine whether novice users would have greater retention of intubation skills with the Airtraq rather than the Macintosh laryngoscope. Twenty medical students who had no prior airway management experience participated in this study. Following brief didactic instruction, each took turns performing laryngoscopy and intubation using the Macintosh and Airtraq devices in easy and simulated difficult laryngoscopy scenarios. The degree of success with each device, the time taken to perform intubation and the assistance required, and the potential for complications were then assessed. Six months later, the assessment process was repeated. No didactic instruction or practice attempts were provided on this latter occasion. Tracheal intubation skills declined markedly with both devices. However, the Airtraq continued to provide better intubating conditions, resulting in greater success of intubation, with fewer optimisation manoeuvres required, and reduced potential for dental trauma, particularly in the difficult laryngoscopy scenarios. The substantial decline in direct laryngoscopy skills over time emphasise the need for continued reinforcement of this complex skill.

A comparison of tracheal intubation using the Airtraq�or the Macintosh laryngoscope in routine airway management: a randomised, controlled clinical trial

The Airtraq laryngoscope is a novel single use tracheal intubation device. We compared the Airtraq with the Macintosh laryngoscope in patients deemed at low risk for difficult intubation in a randomised, controlled clinical trial. Sixty consenting patients presenting for surgery requiring tracheal intubation were randomly allocated to undergo intubation using a Macintosh (n = 30) or Airtraq (n = 30) laryngoscope. All patients were intubated by one of four anaesthetists experienced in the use of both laryngoscopes. No significant differences in demographic or airway variables were observed between the groups. All but one patient, in the Macintosh group, was successfully intubated on the first attempt. There was no difference between groups in the duration of intubation attempts. In comparison to the Macintosh laryngoscope, the Airtraq resulted in modest improvements in the intubation difficulty score, and in ease of use. Tracheal intubation with the Airtraq resulted in less alterations in heart rate. These findings demonstrate the utility of the Airtraq laryngoscope for tracheal intubation in low risk patients.

Learning and performance of tracheal intubation by novice personnel: a comparison of the AirtraqR and Macintosh laryngoscope

Direct laryngoscopic tracheal intubation is taught to many healthcare professionals as it is a potentially lifesaving procedure. However, it is a difficult skill to acquire and maintain, and, of concern, the consequences of poorly performed intubation attempts are potentially serious. The Airtraq Laryngoscope is a novel intubation device which may possess advantages over conventional direct laryngoscopes for use by novice personnel. We conducted a prospective trial with 40 medical students who had no prior airway management experience. Following brief didactic instruction, each participant took turns in performing laryngoscopy and intubation using the Macintosh and Airtraq devices under direct supervision. Each student was allowed up to three attempts to intubate in three laryngoscopy scenarios using a Laerdal Intubation Trainer and one scenario in a Laerdal SimMan Manikin. They then performed tracheal intubation of the normal airway a second time to characterise the learning curve for each device. The Airtraq provided superior intubating conditions, resulting in greater success of intubation, particularly in the difficult laryngoscopy scenarios. In both easy and simulated difficult laryngoscopy scenarios, the Airtraq decreased the duration of intubation attempts, reduced the number of optimisation manoeuvres required, and reduced the potential for dental trauma. The Airtraq device showed a rapid learning curve and the students found it significantly easier to use. The Airtraq appears to be a superior device for novice personnel to acquire the skills of tracheal intubation.

Hypercapnia: permissive and therapeutic

Hypercapnia has traditionally been avoided in the quest to keep parameters normal. Recent understanding of the role of excessive tidal stretch has prompted clinicians to avoid high tidal volumes or plateau pressures, and the resulting permissive hypercapnia has been increasingly tolerated by clinicians. Newer data point to the potential for elevated CO2 to be protective, and in some experimental situations, to cause harm. The protective effects of so called therapeutic hypercapnia' remain experimental at present, but promising laboratory studies suggest potential roles for the eventual selective application at the bedside.

Evaluation of intubation using the Airtraq or Macintosh laryngoscope by anaesthetists in easy and simulated difficult laryngoscopy--a manikin study

The Airtraq Laryngoscope is a novel intubation device which allows visualisation of the vocal cords without alignment of the oral, pharyngeal and tracheal axes. We compared the Airtraq with the Macintosh laryngoscope in simulated easy and difficult laryngoscopy. Twenty-five anaesthetists were allowed up to three attempts to intubate the trachea in each of three laryngoscopy scenarios using a Laerdal Intubation Trainer followed by five scenarios using a Laerdal SimMan Manikin. Each anaesthetist then performed tracheal intubation of the normal airway a second time to characterise the learning curve. In the simulated easy laryngoscopy scenarios, there was no difference between the Airtraq and the Macintosh in success of tracheal intubation. The time taken to intubate at the end of the protocol was significantly lower using the Airtraq (9.5 (6.7) vs. 14.2 (7.4) s), demonstrating a rapid acquisition of skills. In the simulated difficult laryngoscopy scenarios, the Airtraq was more successful in achieving tracheal intubation, required less time to intubate successfully, caused less dental trauma, and was considered by the anaesthetists to be easier to use.

Maternal brain death--an Irish perspective

BACKGROUND

Brainstem death is a concept used in cases in which life-support equipment obscures the conventional cardiopulmonary criteria of death. Brainstem death during pregnancy is an occasional and tragic occurrence.

AIMS

To considerthe ethical, legal and medical issues raised by maternal brainstem death.

METHODS

Medline and Embase search.

RESULTS

The death of the mother mandates consideration of whether continuing maternal organ supportive measures in an attempt to attain foetal viability is appropriate, or whether it constitutes futile care. There is no theoretical limit to the duration of time for which maternal somatic function may be sustained. However, successful prolongation of maternal somatic function in pregnancies of less than 16 weeks gestation has not been reported to date. There is no legal imperative to continue maternal somatic support where there is little likelihood of a successful foetal outcome.

CONCLUSION

The difficult issues raised by maternal brainstem death mandates a consensus building approach to decision making in this context.

Anti-inflammatory effect of augmented nitric oxide production in chronic lung infection

Chronic infection of the lungs with Pseudomonas aeruginosa complicates many long-term lung diseases including cystic fibrosis, bronchiectasis, chronic obstructive lung disease, and mechanical ventilation. In acute inflammatory lung diseases, increased nitric oxide synthase (NOS-2) expression leads to excess nitric oxide (NO) production, resulting in the production of reactive nitrogen intermediates, which contribute to tissue damage. In contrast, the contribution of NO to pulmonary damage in chronic Pseudomonas infection of the lung has not been directly examined and is unclear. Although NOS-2 expression is increased in this condition, NO production is not abnormally elevated. It was hypothesized that chronic infection of the airways does not cause increased NO production but, in contrast, leads to inappropriately low NO concentrations that are pro-inflammatory. A rodent model of chronic airway infection was used to examine the effects on lung damage of augmenting or inhibiting NO production after airway infection with P. aeruginosa was well established. Three days post-infection, L-arginine, which augments NO production, or L-NAME, an inhibitor of NO production, was administered in drinking water. Lung damage was assessed 12 days later. L-arginine treatment reduced tissue damage, inhibited neutrophil recruitment, and reduced the pro-inflammatory cytokine interleukin (IL)-1beta. Treatment with L-NAME caused loss of alveolar walls, greater vascular damage, and increased levels of the pro-inflammatory cytokine IL-6. Thus, in chronic airway infection, inhibition of NO production worsened lung damage, whereas augmenting NO ameliorated this damage. This is the first demonstration that augmenting endogenous NO production in chronic infective lung disease caused by P. aeruginosa is anti-inflammatory. Given that infection with this organism complicates many chronic lung diseases, most notoriously cystic fibrosis, these findings have important clinical implications.

Preoperative intravenous fluid therapy decreases postoperative nausea and pain in high risk patients

The potential for preoperative IV rehydration to reduce postoperative nausea and vomiting (PONV) and pain in patients undergoing ambulatory surgery remains unclear, with conflicting results reported. We sought to determine whether preoperative IV rehydration with a balanced salt solution would decrease the incidence of PONV in patients at increased risk for these symptoms. Eighty ASA grade I-III patients presenting for gynecologic laparoscopy were randomized to receive large (2 mL/kg per hour fasting) or small (3 mL/kg) volume infusions of compound sodium lactate solution over 20 min preoperatively. A standardized balanced anesthetic was used. The incidence and severity of PONV and pain, and need for supplemental antiemetic and analgesic therapy, were assessed by a blinded investigator at 0.5, 1, and 4 h postoperatively, and on the first and third postoperative days. The incidence (control 87% versus large volume 59%) and severity of PONV were significantly reduced in the large volume infusion group at all time intervals. The large volume infusion group also had decreased postoperative pain scores and required less supplemental analgesia. Preoperative correction of intravascular volume deficits effectively reduces PONV and postoperative pain in high risk patients presenting for ambulatory surgery. We recommend the preoperative administration of 2 mL/kg of compound sodium lactate for every hour of fasting to patients with an increased PONV risk presenting for ambulatory surgery.

Optimizing the dose of intrathecal morphine in older patients undergoing hip arthroplasty

Intrathecal (IT) morphine provides excellent postoperative analgesia but may result in many side effects, including postoperative nausea and vomiting, pruritus, and respiratory depression, particularly at larger doses. Older patients may be at particular risk. The optimal dose of spinal morphine in older patients undergoing hip arthroplasty is not known. We designed this prospective, randomized, controlled, double-blinded study to evaluate the analgesic efficacy and side effect profile of 50-200 microg of IT morphine in older patients undergoing elective hip arthroplasty. Sixty patients older than 65 years undergoing elective hip arthroplasty were enrolled. Patients were randomized to receive spinal anesthesia with 15 mg of bupivacaine and IT morphine in four groups: 1). 0 microg, 2). 50 microg, 3). 100 microg, and 4). 200 microg. IT morphine 100 and 200 microg produced effective pain relief and decreased the postoperative requirement for morphine compared with control. IT morphine 50 microg did not provide effective pain relief. Both 100 and 200 microg of IT morphine provided comparable levels of postoperative analgesia. There were no between-group differences in postoperative nausea and vomiting, sedation, respiratory depression, or urinary retention. Pruritus was significantly more frequent with 200 microg of IT morphine. In conclusion, 100 microg of IT morphine provided the best balance between analgesic efficacy and side effect profile in older patients undergoing hip arthroplasty.

IMPLICATIONS

The dosage of intrathecal morphine that provides the best balance between analgesic efficacy and side effect profile in the older patient undergoing hip arthroplasty is not known. This prospective, randomized, controlled, double-blinded clinical trial demonstrates that a dose of 100 microg of intrathecal morphine provides the best balance between efficacy and side effects, compared with doses of 0, 50, and 200 microg of morphine, in this patient population.

Interleukin-1 beta rapidly inhibits aortic endothelium-dependent relaxation by a DNA transcription-dependent mechanism

OBJECTIVES

This study examined the effects of interleukin-1 beta on isometric tension development and relaxation in isolated rat aortic rings in response to the alpha-1 adrenergic agonist phenylephrine, the endothelium-dependent vasodilator acetylcholine, and the endothelium-independent vasodilator sodium nitroprusside.

DESIGN

Randomized, controlled, paired design.

SETTING

Animal laboratory within a university department of physiology. SUBJECTS Paired aortic thoracic aortic rings from specific pathogen-free Sprague-Dawley rats.

INTERVENTIONS

Series I examined the potential for interleukin-1 beta to cause early arterial endothelial dysfunction. Paired aortic rings were incubated for 2 hrs with interleukin-1 beta or vehicle. Series II examined the potential for inhibition of DNA transcription to attenuate interleukin-1 beta-mediated endothelial dysfunction. Paired rings received either dactinomycin or vehicle before interleukin-1 beta incubation. Series III quantified the degree to which inhibition of DNA transcription inhibited early interleukin-1 beta-mediated endothelial dysfunction. Paired rings received either dactinomycin pretreatment followed by interleukin-1 beta incubation, or pretreatment and incubation with inert vehicles. Series IV assessed the effects of interleukin-1 beta on responsiveness to an exogenous nitric oxide donor, sodium nitroprusside, in the presence of the nitric oxide synthesis inhibitor N omega-nitro-L-arginine methyl ester.

MEASUREMENTS AND MAIN RESULTS

Incubation with interleukin-1 beta for 2 hrs had no effect on contractile response but attenuated endothelium-dependent relaxation significantly relative to control. Dactinomycin pretreatment inhibited early interleukin-1 beta-mediated endothelial dysfunction. The combination of interleukin-1 beta and dactinomycin produced effects on endothelium-dependent relaxation that were not different from that seen in rings not exposed to interleukin-1 beta. Interleukin-1 beta attenuated responsiveness to sodium nitroprusside relative to control.

CONCLUSIONS

Interleukin-1 beta causes an early impairment of endothelium-dependent vasorelaxation with an onset that precedes its effects on systemic contractility. This impairment occurs via a mechanism that is wholly or predominantly dependent on DNA transcription. The altered vasorelaxation induced by interleukin-1 beta is at least partly mediated by a reduction in nitric oxide responsiveness.

Assessment of a simple artificial neural network for predicting residual neuromuscular block

BACKGROUND

Postoperative residual curarization (PORC) after surgery is common and its detection has a high error rate. Artificial neural networks are being used increasingly to examine complex data. We hypothesized that a neural network would enhance prediction of PORC.

METHODS

In 40 previously reported patients, neuromuscular function, neuromuscular block/antagonist usage and time intervals were recorded throughout anaesthesia until tracheal extubation by an observer uninvolved in patient care. PORC was defined as significant 'fade' (train of four <0.7) at extubation. Neuromuscular function was classified as PORC (value=1) or no PORC (value=0). A back-propagation neural network was trained to assign similar values (0, 1) for prediction of PORC, by examining the impact of (i) the degree of spontaneous recovery at reversal, and (ii) the time since pharmacological reversal, using the jackknife method. Successful prediction was defined as attainment of a predicted value within 0.2 of the target value.

RESULTS

Twenty-six patients (65%) had PORC at tracheal extubation. Clinical detection of PORC had a sensitivity of 0 and specificity of 1, with an indeterminate positive predictive value and a negative predictive value of 0.35. Using the artificial neural network, one patient with residual block and one with adequate neuromuscular function were incorrectly classified during the test phase, with no indeterminate predictions, giving an artificial neural network sensitivity of 0.96 (chi(2)=44, P<0.001) and specificity of 0.92 (P=1), with a positive predictive value of 0.96 and a negative predictive value of 0.93 (chi(2)=12, P<0.001).

CONCLUSIONS

Neural network-based prediction, using readily available clinical measurements, is significantly better than human judgement in predicting recovery of neuromuscular function.

Isoprostanes--markers of ischaemia reperfusion injury

Ischaemia reperfusion injury is a common and important phenomenon that occurs predictably in patients undergoing such procedures as cardiopulmonary bypass, thrombolysis, surgery under tourniquet, organ transplantation or embolectomy. Oxidative stress and the resulting lipid peroxidation play a major role in reperfusion injury. Membrane and cellular dysfunction result and, subsequently, organ injury or failure may ensue. Traditional methods of quantifying ischaemia reperfusion injury, including measurement of malondialdehyde, lack specificity and sensitivity. It was reported in 1990 that isoprostanes, a series of prostaglandin-like compounds, are produced by the free radical-catalyzed peroxidation of arachidonic acid. Measurement of the isoprostane concentration in urine or plasma provides the most reliable, non-invasive method currently available to assess oxidative stress in vivo. Serial measurement of isoprostanes in biological fluids has enhanced our understanding of the mechanisms underlying ischaemia reperfusion injury itself and its role in certain diseases. Furthermore, measurement of the isoprostane concentration provides a means to assess the effects of prophylactic and therapeutic interventions. In the future, the development of rapid, simple assays for isoprostanes offers the potential to assess prognosis during and after ischaemia reperfusion events.

Cyclizine and droperidol have comparable efficacy and side effects during patient-controlled analgesia

BACKGROUND

Post-operative nausea and vomiting (PONV) is common, especially following gynaecological surgery. Patient-controlled analgesia (PCA) is frequently complicated by nausea. We assessed PONV, pain and sedation in patients receiving cyclizine or droperidol during PCA following abdominal hysterectomy in a double-blind trial.

METHODS

Thirty women were randomised to receive either cyclizine 0.7 mg/kg or droperidol 0.04 mg/kg during surgery followed by PCA containing morphine sulphate with cyclizine 2 mg or droperidol 0.05 mg per demand. Blinded observers scored levels of nausea, sedation, anxiety and pain.

RESULTS

Pain scores, PCA usage and supplemental antiemetic requirements were comparable. Nausea and sedation scores were similar in both groups. Two patients in each group developed refractory PONV. Pre-operative anxiety scores were similar and decreased comparably over time. Patients developing refractory emetic sequelae had a higher incidence of previous PONV. Previous PONV also predicted lower PCA medication intake despite similar demand rates, suggesting increased usage during lock-out periods.

CONCLUSION

Prophylactic cyclizine and droperidol have similar efficacy during PCA. Neither is associated with perioperative anxiety. A minority of patients have refractory PONV during PCA. Previous PONV may predict less efficient PCA usage.