Intravenous opioids reduce airway irritation during induction of anaesthesia with desflurane in adults{dagger}

C. F. Kong, S. T. H. Chew and P. C. Ip-Yam

Department of Anaesthesia and Surgical Intensive Care, Singapore General Hospital, Outram Road, Singapore 169608*Corresponding author

Accepted for publication: April 10, 2000


    Abstract
 Top
 Abstract
 Introduction
 Patients
 Methods
 Results
 Discussion
 Conclusion
 References
 
Desflurane is not used for the induction of anaesthesia despite its favourable pharmacokinetic characteristics because it causes airway irritation. We investigated whether pretreatment with i.v. narcotics reduced unwanted effects. One hundred and eighty adults were randomized to three groups (60 per group) to receive i.v. saline, fentanyl 1 µg kg–1 and morphine 0.1 mg kg–1, respectively, before inhalational induction with desflurane in nitrous oxide and oxygen. Mean time to loss of response to commands was 4.0 min, without significant differences between groups. The incidence of coughing was greater (25%) in the control group than in the fentanyl (5.0%) and morphine groups (8.3%). The incidence of apnoea was 20.0% in the control group versus 13.3 and 5.0% in the fentanyl and morphine groups, respectively. Laryngospasm developed in 11.7% of controls compared with 3.3 and 1.7% in the fentanyl and morphine groups, respectively. More patients in the control group had excitatory movements (46.7%) than in the fentanyl (16.7%) and morphine (8.3%) groups. These results demonstrate that i.v. opioids reduce airway irritability significantly during inhalational induction with desflurane in adults.

Br J Anaesth 2000: 84; 364–7

Keywords: anaesthetics, volatile, desflurane; anaesthetics i.v., opioid, morphine; anaesthetic techniques, induction; airway


    Introduction
 Top
 Abstract
 Introduction
 Patients
 Methods
 Results
 Discussion
 Conclusion
 References
 
Desflurane is a halogenated ether with low solubility (partition coefficients: blood:gas, 0.42; oil:gas, 18.71), giving rapid induction and emergence from anaesthesia.23 It has other valuable features, such as stability in soda lime45 and negligible biotransformation to toxic metabolites,67 and hence a low potential for hepatic and renal toxicity. However, it can cause airway irritation when used for the induction of anaesthesia in adults812 and children, leading to coughing, apnoea, laryngospasm, copious secretions and excitatory movements.13 14 We studied the ability of intravenous opioids to reduce the airway irritation caused by desflurane.


    Patients
 Top
 Abstract
 Introduction
 Patients
 Methods
 Results
 Discussion
 Conclusion
 References
 
With hospital ethics committee approval and patient consent, 180 adult ASA I and II patients aged between 18 and 65 yr who were scheduled for elective surgery entered the study. The exclusion criteria were anaemia, a history suggestive of malignant hyperthermia, a family history of anaesthetic mishaps, severe lung disease, chronic cough (cough occurring for at least 3 months of the year for 2 successive years), obesity (body mass index >30 kg m–2), previous exposure to desflurane, smoking, and medication that could interfere with the study (e.g. anxiolytics). Patients with a history of upper respiratory tract infection within 1 month of surgery were also excluded. Patients were randomized to three groups (60 patients per group) to receive morphine, fentanyl or saline before induction with desflurane. Randomization was by means of sealed envelope.


    Methods
 Top
 Abstract
 Introduction
 Patients
 Methods
 Results
 Discussion
 Conclusion
 References
 
Monitoring included continuous ECG, pulse oximetry, non-invasive blood pressure, end-tidal CO2 and expired desflurane concentration (Hewlett-Packard Anaesthetic Gas Module M1026A).

The opioids were given from a syringe containing either fentanyl, morphine or saline made up to 10 ml (in saline if necessary), prepared by an assistant who was not involved in the study. The anaesthetist administered the drugs over 1 min and was not aware of the contents of the syringe.

Saline (group C), morphine 0.1 mg kg–1 (group M) or fentanyl 1 µg kg–1 (group F) was given 2 min before preoxygenation with 100% oxygen at 6 litre min–1 for 3 min using a circle system with soda lime absorber. The oxygen flow was then reduced to 3 litre min–1 and nitrous oxide (50%) was started at 3 litre min–1. Desflurane 1% was started and increased by 1% after every six breaths. Every 10 s during this period, each patient was asked to open his or her eyes. The time when the patient failed to respond to this command was taken as the time of completion of inhalational induction.

We recorded the age, sex, weight, ASA status, diagnosis and the type of surgical procedure for each patient. The reading of the pulse oximeter before induction and the lowest reading obtained during induction were noted. The time between starting desflurane and loss of consciousness was calculated and the expired desflurane concentration at loss of consciousness was noted. Any coughing, apnoea, laryngospasm or excitatory movements were noted. Coughing was considered mild if there were 1–3 coughs, moderate if there were 4–7 coughs and severe if there were 8 coughs or more. Apnoea was noted as no breathing movements for more than 30 s.

If patients developed laryngospasm, i.v. propofol 2 mg  kg–1 was given with the addition of i.v. suxamethonium 1 mg kg–1 if necessary. The patients were then ventilated using the mask with 100% O2 until saturation improved.

If apnoea and oxygen desaturation were present (SpO2 <90%, or a decrease of more than 5% from initial value), the lungs were ventilated via a mask until spontaneous respiration returned.

Statistics
Analysis of variance (ANOVA) was used to analyse parametric data and all non-parametric data were analysed using the Kruskal–Wallis and Mann–Whitney tests. A P value of <0.05 was considered significant.


    Results
 Top
 Abstract
 Introduction
 Patients
 Methods
 Results
 Discussion
 Conclusion
 References
 
The three groups were comparable in age, sex, weight and ASA status (Table 1).


View this table:
[in this window]
[in a new window]
 
Table 1 Characteristics of the three groups
 
The induction times for the three study groups are given in Table 2, and were not significantly different (P=0.26).


View this table:
[in this window]
[in a new window]
 
Table 2 Time required for induction and the expired desflurane concentration at induction. Values with the same superscript are significantly different (P<0.05)
 
The expired desflurane concentrations at loss of response to command are given in Table 2. The concentration was greater in the morphine group than in the control group (P=0.02).

The incidence of complications is shown in Table 3. Significant differences in coughing were found between the control and fentanyl groups (P=0.002) and between the control and morphine groups (P=0.013). No differences were found between the morphine and fentanyl groups.


View this table:
[in this window]
[in a new window]
 
Table 3 Incidence of cough, apnoea, laryngospasm and excitatory movements during desflurane induction. Values with the same superscript are significantly different (P<0.05)
 
The difference in apnoea between the control and morphine groups was statistically significant (P=0.012). No significant differences were found between the control and fentanyl groups or the morphine and fentanyl groups.

Seven patients in the control group had laryngospasm. In one of these, oxygen saturation decreased to 70%. Two patients in the fentanyl group and one patient in the morphine group had laryngospasm without oxygen desaturation. There was a significant difference between the control and morphine groups (P=0.025). No differences were found between the control and fentanyl groups or the morphine and fentanyl groups.

There were more excitatory movements in the control group than in the morphine group (P=0.025), but the control and fentanyl groups and the morphine and fentanyl groups did not differ.

The blood pressure and heart rate changes in the three groups are given in Table 4. Overall there were no group differences and the magnitudes of the changes were not of clinical significance.


View this table:
[in this window]
[in a new window]
 
Table 4 Arterial pressure (mm Hg, mean (SD)) and heart rate (beats min–1) before and after induction
 

    Discussion
 Top
 Abstract
 Introduction
 Patients
 Methods
 Results
 Discussion
 Conclusion
 References
 
Expired desflurane concentration at the end of induction
The mean (SD) expired desflurane concentration at completion of induction in the control, fentanyl and morphine groups was 3.8 (1.1), 3.9 (1.2) and 4.4 (1.5)%, respectively. During the study, 50% N2O was introduced together with desflurane. This could explain the lower expired desflurane concentration at the completion of induction, as the use of N2O reduces the minimal alveolar concentration (MAC) of volatile anaesthetic.

This study showed a significant difference in the expired desflurane concentration at the end of induction between the control and morphine groups. This difference may have been the result of sedation cause by morphine.

No differences were found between the fentanyl and control groups. Fentanyl had a peak effect at 4–5 min. It may be that the effect of fentanyl was beginning to wear off (even though its duration of action is 20–30 min).

Time to loss of response to command
No differences were found between the three groups in the time taken to induction, which was approximately 5 min. This could be due to the slow, small increments in inhaled concentration in the study design because of the risk of laryngospasm.

Coughing occurs in 26–59% of patients during desflurane inhalation.812 This is supported by our results. The control group had an incidence of coughing of 25.0%. Among the 14 patients who coughed, cough was mild in two, moderate in seven and severe in five. Morphine or fentanyl reduced the incidence of coughing. In the fentanyl group, all three patients had mild cough, whereas of the five patients who received morphine two had mild cough, two had moderate cough and one had severe cough.

Sevoflurane is often used for inhalational induction in both adults and children, with coughing in 16%.1719 The tidal volume induction technique may be associated with a greater incidence of airway complications compared with vital capacity induction.1719 Pretreatment with morphine or fentanyl reduces the incidence of airway complications below 10% during tidal volume induction using desflurane.

This study also supports the incidence of apnoea reported in the literature (13–35%),812 with 20% in the control group. Pretreatment with morphine or fentanyl reduced the incidence of this adverse effect to 5 and 13.3%, respectively. These incidences are comparable with those reported for sevoflurane (16%).1719

The incidence of excitation is reported to be 24–43%,812 and was 47% in this study. Pretreatment with morphine or fentanyl reduces the incidence to 8.3% and 16.7%, respectively. When sevoflurane is used for induction 12% of patients exhibit excitatory movements.1719 Morphine pretreatment reduces the incidence of excitatory movements to a comparable figure during desflurane inhalational induction.

Seven patients (11.7%) in the control group had laryngospasm during induction, similar to the reported incidence of up to 17%.812 Three of these seven patients also had cough of moderate severity, two had apnoea and five had excitatory movements. One patient, a 31-yr-old ASA I man, had significant desaturation during induction. He also had excitatory movement but he did not cough or become apnoeic during induction. His blood pressure remained stable.

One patient in the morphine group had laryngospasm. He did not cough or have apnoea or excitatory movements during induction, or show arterial desaturation during the episode. Two patients in the fentanyl group had laryngospasm with mild cough and excitatory movement. They did not have apnoea or arterial oxygen desaturation during this episode. Laryngospasm is reported in 3–8% of patients induced with sevoflurane and a tidal volume induction technique.18 19 Pretreatment with morphine or fentanyl reduces the incidence of laryngospasm during desflurane induction to a figure comparable with sevoflurane induction.


    Conclusion
 Top
 Abstract
 Introduction
 Patients
 Methods
 Results
 Discussion
 Conclusion
 References
 
Pretreatment with morphine or fentanyl reduces the incidence of airway irritation to a value similar to that value reported with sevoflurane during inhalational induction of anaesthesia. However, for direct comparison a randomized study should be performed. With opioid pretreatment, desflurane can be considered for inhalational induction of anaesthesia in adults.


    References
 Top
 Abstract
 Introduction
 Patients
 Methods
 Results
 Discussion
 Conclusion
 References
 
1 Eger EI. Partition coefficient of I-653 in human blood, saline and olive oil. Anesth Analg 1987; 6: 971–3

2 Kennedy SK, Longnecker DE. History and principles of anaesthesiology. Goodman and Gilman’s The Pharmacological Basis of Therapeutics. 8th edn. New York: Pergamon Press, 1990: 273

3 Yasuda N, Lockhart SH, Eger EI, Weiskopf RB, Johnson BH, Freire BA, et al. Kinetics of desflurane, isoflurane and halothane in humans. Anesthesiology 1991; 74: 489–98[ISI][Medline]

4 Eger EI. Stability if I-653 in soda lime. Anesth Analg 1987; 66: 983–5[Abstract]

5 Fang ZX, Eger EI, Laster MJ, Chortkoff, Kandel L, Ionescu P. Carbon monoxide production from degradation of desflurane, enflurane, isoflurane, halothane and sevoflurane by soda lime and baralyme. Anesth Analg 1995; 80: 1187–93[Abstract]

6 Koblin DD, Weiskopf RB, Holmes MA, Konopka K, Rampil IJ, Eger EI, et al. Metabolism of I-653 and isoflurane in swine. Anesth Analg 1989; 68: 147–9[Abstract]

7 Koblin DD, Eger EI, Johnson BH, Konopka K, Waskell L. I-653 resists degradation in rats. Anesth Analg 1988; 67: 534–8[Abstract]

8 Rampil IJ, Lockhart SH, Zwass MS, Peterson N, Yasuda N, Eger EI, et al. Clinical characteristics of desflurane in surgical patients: minimal alveolar concentration. Anesthesiology 1991; 74: 429–33[ISI][Medline]

9 Lebenbom-Mansour MH, Pandit SK, Kothary SP, Randel GI, Levy L. Desflurane versus propofol anesthesia: a comparative analysis in outpatients. Anesth Analg 1993; 76: 936–41[Abstract]

10 Rapp SE, Conathan TJ, Pavlin DJ, Levy WJ, Hautman B, Lecky J, et al. Comparison of desflurane with propofol in outpatients undergoing peripheral orthopedic surgery. Anesth Analg 1992; 75: 572–9[Abstract]

11 Wrigley SR, Fairfield JE, Jones RM, Black AE. Induction and recovery characteristics of desflurane in day case patients: a comparison with propofol. Anaesthesia 1991; 46: 615–22[ISI][Medline]

12 Van-Hemelrijck J, Smith I, White PF. Use of desflurane for outpatient anesthesia. A comparison with propofol and nitrous oxide. Anesthesiology 1991; 75: 197–203[ISI][Medline]

13 Zwass MS, Fisher DM, Welborn LG, Cote CJ, Davis PJ, Dinner M, et al. Induction and maintenance characteristics of anesthesia with desflurane and nitrous oxide in infants and children. Anesthesiology 1992; 76: 373–8[ISI][Medline]

14 Taylor RHI, Lerman J. Induction, maintenance and recovery characteristics of desflurane in infants and children. Can J Anaesth 1992; 39: 6–13[Abstract]

15 Cahalan MK, Weiskopf RB, Eger EI, Yasuda N, Ionescu P, Rampil IJ, et al. Hemodynamic effects of desflurane/nitrous oxide anesthesia in volunteers. Anesth Analg 1991; 73: 157–64[Abstract]

16 Weiskopf RB, Cahalan MK, Eger EI, Yasuda N, Rampil IJ, Ionescu P, et al. Cardiovascular actions of desflurane in normocarbic volunteers. Anesth Analg 1991; 73: 143–56[Abstract]

17 Epstein RH, Mendel HG, Guarnieri KM, Staudt SR, Lessin JB, Marr AT. Sevoflurane versus halothane for general anaesthesia in pediatric patients: a comparative study of vital signs, induction, and emergence. J Clin Anesth 1995 7: 237–44

18 Johannesson GP, Floren M, Lindahl SGE. Sevoflurane for ENT-surgery in children: a comparision with halothane. Acta Anaesthesiol Scand 1995; 39: 546–50[ISI][Medline]

19 Saito S, Goto F, Kadoi Y, Takahashi T, Fujita T, Mogi K. Comparative clinical study of induction and emergence time in sevoflurane and enflurane anaesthesia. Acta Anaesthesiol Scand 1989; 33: 389–90[ISI][Medline]