J. E. Smith

Learning curves for fibreoptic nasotracheal intubation when using the endoscopic video camera

We have followed the progress of 12 anaesthetic trainees as they learnt how to perform fibreoptic nasotracheal intubation with the aid of an endoscopic video camera system. Each trainee had a structured teaching session on a bronchial tree model, viewed an instructional videotape and then performed 20 nasotracheal intubations on anaesthetised oral surgery patients. Trainees were required to perform the endoscopies under full visual control and to demonstrate airway anatomy as they advanced the fibrescope. They were allowed up to two 2½ min periods to complete nasotracheal endoscopy. All 240 endoscopies were completed within the time limit: 228 were completed within 2½ min and 12 (5%) were completed during the second 2½ min period. We constructed a group learning curve from the pooled data. The half‐life of the curve was nine endoscopies. The best fit value for the first endoscopy time was 132 s, and after the 18th (two half‐lives) it was 49 s. We analysed the theoretical basis for deriving a learning curve from raw data. This information could form a rational basis for the design of fibreoptic training programmes using video imaging systems.

Intravenous regional analgesia. The danger of the congested arm and the value of occlusion pressure.

Two cases are described in which congestion of the arm occurred during intravenous regional analgesia. One case exhibited signs of serious local anaesthetic toxicity, while a significant plasma bupivacaine level was demonstrated in the other. In a study in a volunteer, leakage of contrast medium past the cuff was demonstrated radiologically only when congestion of the arm was produced. The Hoyle double cuff apparatus has narrow runs producing less tissue compression than a standard blood pressure cuff inflated to the same pressure. It may sometimes not occlude the brachial artery when inflated to a pressure based on the systolic arterial pressure measured with a standard cuff and congestion of the arm may then result. Increases in arterial blood pressure occurring during the procedure can also lead to congestion of the arm. Congestion may increase the risk of local anaesthetic agent leaking past the tourniquet into the systemic circulation. Recommendations are made about the choice of cuff gauge pressure and the prevention of arm congestion occurring during intravenous regional analgesia.

Heart rate and arterial pressure changes during fibreoptic tracheal intubation under general anaesthesia

The cardiovascular responses to fibreoptic orotracheal intubation under general anaesthesia were compared with those in a control group in whom tracheal intubation was effected with a Macintosh laryngoscope. The patients received a standard anaesthetic and were allocated randomly to either group immediately before intubation. Fibreoptic intubation took significantly longer to perform. There were significant increases in heart rate and arterial pressure in both groups compared with pre‐induction values. The tachycardia in the fibreoptic group was significantly greater than that in the control group during the second minute after intubation, and the increase in systolic pressure was sustained for a longer period in the fibreoptic group. The maximum increases in systolic and diastolic pressures above pre‐intubation values were significantly greater in the fibreoptic group. The cardiovascular responses associated with fibreoptic intubation under general anaesthesia appear to be more severe than those which follow intubation effected with a Macintosh laryngoscope.

Cardiovascular effects of fibrescope-guided nasotracheal intubation

The cardiovascular effects of fibrescope‐guided nasotracheal intubation were compared to those of a control group of patients who were intubated using the Macintosh laryngoscope. The 60 patients studied received a standard anaesthetic technique which included a muscle relaxant and were allocated randomly to one of two groups immediately before tracheal intubation. Systolic and diastolic arterial pressures in the fibreoptic group were significantly lower than in the control group during the first minute after intubation. The maximum increase in diastolic pressure was significantly lower in the fibreoptic group. The heart rate in the fibreoptic group was significantly higher than in the control group during all five minutes after intubation. The maximum increase in hearl rate was significantly higher in the fibreoptic group. The cardiovascular responses to fibreoptic nasotracheal intubation under general anaesthesia should not cause undue concern in fit patients, but appropriate measures should be taken to prevent excessive tachycardia in compromised patients.

Nasotracheal tube placement over the fibreoptic laryngoscope

We have assessed the effectiveness of three tracheal tube rotational movements in assisting nasotracheal tube placement over the fibreoptic laryngoscope. Ninety ASA grade 1 or 2 oral surgery patients undergoing fibreoptic nasotracheal intubation under general anaesthesia were studied. After the fibrescope had been positioned in the trachea, patients were randomly allocated to one of three groups. In group 1, no rotation was used and the tube was advanced towards the trachea in the neutral position. In group 2, the tube was rotated by 90° anticlockwise. In group 3, the tube was rotated by 180° anticlockwise, then rotated back to 90° anticlockwise (overcorrected rotation). If resistance to the advance was encountered, up to two more attempts were allowed, after further rotational manoeuvres had been made, in accordance with a standard, graduated sequence. There were significantly more successful tube placements at the first attempt in groups 2 and 3 (93% and 100% respectively) than in group I (63%). It is therefore recommended that 90° anticlockwise or overcorrected 90° anticlockwise tube rotation is used to facilitate nasotracheal tube placement during fibreoptic intubation.

Cardiovascular effects of nasotracheal intubation

Intubation time, arterial pressure, heart rate and arterial oxygen saturation during nasotracheal intubation effected with the Macintosh laryngoscope blade were compared with those during orotracheal intubation. The 60 patients studied received a standardised general anaesthetic and were randomly allocated to one of two groups immediately before tracheal intubation. The mean nasal intubation time (33.2 seconds) was significantly greater than mean oral intubation time (14.8 seconds). The mean arterial pressure changes in the nasal group were significantly greater and more prolonged than in the oral group. The mean heart rate in the nasal group was significantly lower than in the oral group during the first minute after intubation, after which heart rates were similar. There were no significant differences between the two groups with regard to arterial oxygen saturation levels at any stage.

Effect of fentanyl on the circulatory responses to orotracheal fibreoptic intubation

The effectiveness of fentanyl in attenuating the pressor and heart rate response to orotracheal fibreoptic intubation under general anaesthesia was assessed in 60 healthy patients undergoing elective surgery. Patients were randomly assigned to receive either fibreoptic intubation with or without fentanyl 6μg.kg−1 or traditional Macintosh intubation with fentanyl 6μg.kg−1. A standardised general anaesthetic was administered which included temazepam premedication, thiopentone, atracurium, oxygen, nitrous oxide and isoflurane. The pressor response to fibreoptic intubation was suppressed in those patients who received fentanyl and was similar to that seen in the Macintosh‐fentanyl group of patients. The heart rate response to fibreoptic intubation was also significantly reduced in the patients who received fentanyl, but, in contrast, was still significantly greater than that in the Macintosh‐fentanyi group. Fentanyl 6μg.kg−1 appears to have a useful place in attenuating the cardiovascular effects of fibreoptic intubation under general anaesthesia.

Conversion of orotracheal to nasotracheal intubation with the aid of the fibreoptic laryngoscope

increased to 1.4 cmH,O under similar conditions after 5 h use. It is probable that the discrepancy in monitored tidal volume was due to a change in the expiratory flow waveform resulting from an increase in breathing system resistance Royaf Liverpool University S.N. COSTIGAN Thus the effect on the accuracy and performance of S.L. SNOWDON anaesthetic monitoring apparatus needs to be considered when selecting a bacteriological filter for use in breathing systems.

Cardiovascular responses following laryngoscope assisted, fibreoptic orotracheal intubation.

The Macintosh laryngoscope has recently been used successfully as an airway clearance device during fibreoptic intubation in patients who presented difficult intubation, but it is not known whether this approach will increase the pressor response to intubation. The aim of this investigation was to compare the cardiovascular responses of this method of facilitating airway clearance with the lingual traction plus jaw thrust method. 40 ASA I or II adult patients were given a standardised general anaesthetic and were randomly allocated to receive either lingual traction with jaw thrust (lingual traction group) or direct laryngoscopy with a Macintosh laryngoscope (laryngoscopy group) as the airway clearance manoeuvre prior to fibreoptic orotracheal intubation. Following intubation there was a significant rise in arterial pressure above pre‐induction levels in both groups (p < 0.05); however, the arterial pressure in the laryngoscopy group was significantly greater than that in the lingual traction group (systolic: p = 0.031, diastolic: p = 0.002). It appears therefore that the mechanical stimulus of the Macintosh laryngoscopy evokes a greater pressor response than that of lingual traction plus jaw thrust when these interventions are followed by fibreoptic intubation.

Learning fibreoptic endoscopy. Nasotracheal or orotracheal intubations first

We have studied the extent to which learning fibreoptic nasotracheal endoscopy first helped anaesthetists to learn fibreoptic orotracheal endoscopy later, and vice versa. After preliminary training on a bronchial tree model, 30 anaesthetic trainees were randomly allocated to the nasal first/oral second group, who performed 10 nasal intubations followed by 10 oral intubations, or the oral first/nasal second group, who performed 10 oral intubations followed by 10 nasal intubations, in anaesthetised, ASA group I or II patients undergoing elective oral or general surgery. Each type of endoscopy was taught in a standard manner, with the aid of an endoscopic video‐camera system, under the supervision of experienced instructors. Performing nasal endoscopy second (average 70.8 s) took significantly less time than performing it first (average 84.4 s) and performing oral endoscopy second (average 35.2 s) took significantly less time than performing it first (average 48.5 s). The mean (SD) total endoscopy time for all the endoscopies (both nasal and oral) in the nasal first/oral second group [1196 (162) s] was not significantly different from that for all the endoscopies in the oral first/nasal second group [1193 (188) s]. Because there is no advantage or disadvantage to be gained in starting to learn either type of endoscopy first, graduated training programmes can be planned according to the availability of suitable patients for fibreoptic intubation, without instructors needing to consider whether trainees make better progress if they learn one technique before the other.