Obstetric Anaesthetists' Association and Difficult Airway Society guidelines for the management of difficult and failed tracheal intubation in obstetrics

The Obstetric Anaesthetists' Association and Difficult Airway Society have developed the first national obstetric guidelines for the safe management of difficult and failed tracheal intubation during general anaesthesia. They comprise four algorithms and two tables. A master algorithm provides an overview. Algorithm 1 gives a framework on how to optimise a safe general anaesthetic technique in the obstetric patient, and emphasises: planning and multidisciplinary communication; how to prevent the rapid oxygen desaturation seen in pregnant women by advocating nasal oxygenation and mask ventilation immediately after induction; limiting intubation attempts to two; and consideration of early release of cricoid pressure if difficulties are encountered. Algorithm 2 summarises the management after declaring failed tracheal intubation with clear decision points, and encourages early insertion of a (preferably second-generation) supraglottic airway device if appropriate. Algorithm 3 covers the management of the 'can't intubate, can't oxygenate' situation and emergency front-of-neck airway access, including the necessity for timely perimortem caesarean section if maternal oxygenation cannot be achieved. Table 1 gives a structure for assessing the individual factors relevant in the decision to awaken or proceed should intubation fail, which include: urgency related to maternal or fetal factors; seniority of the anaesthetist; obesity of the patient; surgical complexity; aspiration risk; potential difficulty with provision of alternative anaesthesia; and post-induction airway device and airway patency. This decision should be considered by the team in advance of performing a general anaesthetic to make a provisional plan should failed intubation occur. The table is also intended to be used as a teaching tool to facilitate discussion and learning regarding the complex nature of decision-making when faced with a failed intubation. Table 2 gives practical considerations of how to awaken or proceed with surgery. The background paper covers recommendations on drugs, new equipment, teaching and training.

A new, minimally invasive technique for measuring cardiac index: clinical comparison of continuous cardiac dynamic monitoring and pulmonary artery catheter methods

To assess the utility of a relatively simple bedside method of estimating cardiac index during major surgery or in the intensive care unit, we conducted a prospective study in patients undergoing elective cardiac bypass surgery where a pulmonary artery catheter was inserted as part of routine monitoring. The cardiac index was estimated using standard techniques and compared with estimates from continuous cardiac dynamic monitoring using HEARTSMART software. Two hundred and seventy sets of measurements were suitable for comparison. The mean bias (95% limits of agreement), for the pre-bypass cardiac index was -0.09 (-1.26 to 1.08) l x min(-1) x m(-2), and post-bypass was 0.12 l x min(-1) x m(-2) (-1.32 to 1.56). These results suggest that continuous cardiac dynamic monitoring using HEARTSMART is sufficiently accurate for assessment of haemodynamic variables in critically ill patients, facilitating goal-directed therapies.

Use of the Combitube for airway maintenance during percutaneous dilatational tracheostomy

The Combitube airway allows short-term ventilation during cardiopulmonary resuscitation and can be useful in the management of the difficult airway. In a prospective observational study we assessed its use during percutaneous dilatational tracheostomy (PDT). Twenty-one intensive care patients scheduled for elective PDT had their tracheal tube replaced by a Combitube airway retaining the same ventilator settings. Arterial blood gases, airway pressures, SpO2 and end-tidal CO2 were measured as were the transmural pressures exerted by the Combitube cuffs. Combitube placement was successful in 20 of 21 patients although adequate ventilation was possible in only 17 (85%). There was no significant change in PaO2, SpO2, end-tidal CO2, Paco2 or mean airway pressure during Combitube ventilation. A high mean (SD) transmural pressure of 14.7 (5) kPa was exerted by the distal cuff. The Combitube provided a satisfactory alternative airway to the tracheal tube during performance of PDT in 85% of our patients. Potential problems associated with its use in intensive care patients are outlined.

A comparison of cisatracurium (51W89) and atracurium by infusion in critically ill patients

OBJECTIVE

To evaluate and compare the safety and efficacy of cisatracurium (51W89) and atracurium administered by continuous infusion to critically ill patients requiring neuromuscular blocking agents to facilitate mechanical ventilation.

DESIGN

Open, randomized, multicenter study of patients receiving cisatracurium or atracurium infusion to facilitate mechanical ventilation.

SETTING

Five university teaching hospital intensive care units in the United Kingdom.

PATIENTS

Sixty-one adult patients requiring neuromuscular blocking agents to facilitate mechanical ventilation.

INTERVENTIONS

Bolus doses followed by continuous infusions of cisatracurium or atracurium were administered. Onset, maintenance, and recovery of neuromuscular blockade were measured, using transcutaneous ulnar nerve stimulation and an accelerometer.

MEASUREMENTS AND MAIN RESULTS

Forty patients received cisatracurium (mean duration 48.1 +/- 4.2 [SEM] hrs), and 21 patients received atracurium (mean duration 46.1 +/- 5.8 hrs). The infusion rate for patients receiving cisatracurium was 3.1 +/- 0.2 microg/kg/min, and for patients receiving atracurium 10.4 +/- 0.9 microg/kg/min. There were no significant differences in mean times to 70% recovery of Train-of-Four ratio (cisatracurium 60 mins, atracurium 57 mins), although there was considerable interpatient variation (20 to 175 mins with cisatracurium vs. 35 to 85 mins with atracurium). One patient who received cisatracurium exhibited intermittent bronchospasm during and after the study period.

CONCLUSIONS

Cisatracurium, an isomer of atracurium, appears to be a suitable agent for providing muscle relaxation in critically ill patients.

Thoracic epidural analgesia started after cardiopulmonary bypass. Adrenergic, cardiovascular and respiratory sequelae

The effects of thoracic epidural analgesia started after cardiopulmonary bypass were studied on the subsequent adrenergic, cardiovascular and respiratory responses. Sixteen cardiac surgical patients received either a standardised general anaesthetic (control group) or a standardised general anaesthetic and thoracic epidural analgesia (epidural group). The epidural catheter was sited before surgery and heparinisation. Following discontinuation of cardiopulmonary bypass, patients in the epidural group were given 15 ml bupivacaine 0.5% down the catheter followed by an infusion of bupivacaine 0.375% at 5-8 ml.h-1 after surgery. The control group received an intravenous morphine infusion on completion of surgery. The adrenergic response was assessed by measuring arterial catecholamine concentrations. Respiratory function was determined by spirometry, peak expiratory flow and arterial partial pressure of oxygen while breathing air. Pain scores were also obtained. After cardiopulmonary bypass the increases in catecholamine concentrations were effectively inhibited in the epidural group for the remainder of the study (p < 0.05). Postoperative respiratory function was less impaired in the epidural group, with higher forced expiratory volume in 1 s, forced vital capacity and peak expiratory flow (p < 0.05). Pain scores were also significantly lower in the epidural group (p < 0.05). There were no significant differences in cardiovascular parameters.

The reinforced laryngeal mask airway for dento-alveolar surgery

We have evaluated the reinforced laryngeal mask airway (LMA) for use during dento-alveolar surgery in 100 ASA I and II day-case patients allocated randomly to receive either a nasotracheal tube or reinforced LMA. We recorded ease of airway insertion, airway complications, quality of recovery and replies to a 24-h postoperative questionnaire. In addition, a fibreoptic assessment was made of laryngotracheal soiling, and the effect of head movement and the position of the reinforced LMA. There were no significant differences in difficulty in airway positioning or perioperative oxygen desaturation. Nineteen patients in the nasotracheal tube group had epistaxis (P = 0.001) and laryngotracheal soiling occurred in three of these patients. Two reinforced LMA were dislodged on moving into the operating theatre and in a further five patients in this group there was partial airway obstruction (compared with none in the nasotracheal tube group; P = 0.018) which was caused by downward pressure on the mandible by the surgeon. There were no differences in postoperative complications. No surgeon reported poor access to the operating field. Overall the reinforced LMA provided satisfactory conditions for this surgery but vigilance of the airway was required, especially at the time of extraction.

Circulating fluoride changes and hepatorenal function following sevoflurane anaesthesia

Sevoflurane, a new volatile inhalational agent, undergoes biotransformation to fluoride which is potentially nephrotoxic. We compared the effects of sevoflurane or isoflurane anaesthesia on hepatorenal function and serum fluoride concentrations in 50 ASA 1-3 patients undergoing major intra-abdominal surgery. No patient developed renal or hepatic dysfunction. Mean (SEM) peak fluoride concentrations were 23.1 (1.5) mumol.l-1 for sevoflurane and 5.4 (0.4) mumol.l-1 for isoflurane (p < 0.001). There was a significant correlation in the sevoflurane group between the total dose of agent (MAC h), the total fluoride production (r = 0.78, p = 0.0001) and peak fluoride concentration (r = 0.57, p = 0.003). There was no correlation between these variables in the isoflurane group.

Sevoflurane anaesthesia for major intra-abdominal surgery

The cardiovascular effects and recovery characteristics of sevoflurane and isoflurane anaesthesia were compared in 30 gynaecological and 20 general surgical patients undergoing elective intra-abdominal surgery. Patients were randomly allocated to receive either sevoflurane or isoflurane as the volatile agent, in a balanced anaesthetic technique including morphine and atropine premedication and thiopentone, fentanyl, vecuronium and nitrous oxide. The concentration of volatile agent was titrated according to clinical variables. Mean heart rate, systolic and diastolic arterial pressure and duration of surgery did not differ between the two groups. Time to emergence from anaesthesia in the gynaecological patients was significantly faster after sevoflurane compared with isoflurane (p < 0.005). Sevoflurane provided stable anaesthesia during major intra-abdominal surgery.

QT interval dispersion: a non-invasive marker of susceptibility to arrhythmia in patients with sustained ventricular arrhythmias?

OBJECTIVE

To assess QT interval dispersion on the surface electrocardiogram in patients with sustained ventricular arrhythmias.

DESIGN

A retrospective and prospective blinded controlled study of patients referred for investigation of ventricular arrhythmias at a tertiary cardiac centre.

PATIENTS AND METHODS

89 consecutive patients with sustained ventricular arrhythmias due to chronic ischaemic heart disease, cardiomyopathy, or ventricular tachycardia (VT) in a normal heart. 32 patients did not meet the inclusion criteria; therefore 57 patients were compared with a control group of 40 patients with myocardial disease but no history of arrhythmias and 12 normal controls with no myocardial disease. Standard 12 lead electrocardiograms were enlarged, the QT intervals for each lead measured, and QT dispersion calculated.

RESULTS

There was a significantly greater mean QT dispersion (77 ms) in patients with sustained ventricular arrhythmias compared with the control group (38 ms, p < 0.01). This held for all groups; after myocardial infarction VT (82 (22) ms v control 38 (10) ms; p < 0.01), dilated cardiomyopathy VT (76 (18) ms v control 40 (11) ms, p < 0.01), and normal heart VT (65 (7) ms v control 32 (8), p < 0.05). There was also a greater QT dispersion in patients with impaired left ventricular function and VT, with a correlation between left ventricular function and QT dispersion in patients with VT (r = 0.56, p < 0.01).

CONCLUSION

QT interval dispersion may be a further non-invasive marker of susceptibility to ventricular arrhythmias.

Studies in postoperative sequelae. Nausea and vomiting--still a problem

We collected data on postoperative nausea and vomiting from 3850 patients aged 11-91 years. Thirty-seven percent of the 3244 patients who received a general anaesthetic reported nausea and 23.2% vomited. Twenty percent of the 606 patients who received a local anaesthetic reported nausea and 11.4% vomited. Of the general anaesthetic patients reporting nausea, 72.2% were women, and the mean age was lower than for those who did not (p < 0.001). Similarly for vomiting, 74.0% were women and again the mean age was lower (p < 0.001). Of the local anaesthetic patients reporting nausea, 62.0% were women and the mean age was lower than for those who did not (p < 0.001). Similarly for vomiting, 68.1% were women and again the mean age was lower (p < 0.001). Anxiety before general, but not local, anaesthesia was associated with postoperative nausea (p < 0.001) but not vomiting. Patients from the gynaecological, orthopaedic, ENT and general surgical wards had higher incidences of postoperative nausea and vomiting. Linear visual analogue pain scores were higher in patients with postoperative nausea and vomiting in both general and local anaesthesia groups (p < 0.001).