Anaesthesia for the majority of thoracic surgical procedures is associated with different methods of intraoperative lung ventilation to immobilize or substantially limit the mobility of an operating field. This can be achieved using one-lung ventilation (OLV) [1, 2, 3, 4]. There are three methods to separate ventilation of both lungs: using double-lumen endotracheal tubes, endobronchial blockers or endobronchial tubes [5, 6]. The use of double-lumen tubes allows, with the closure of one lumen, to exclude from ventilation the „upper” lung operated on, which remains immobile. The second lumen provides ventilation of the “lower” lung.  Immobilization of the dependent lung improves the conditions of the procedure thus shortening its duration [6, 7].

The Robertshow double-lumen tubes, which serve to intubate the right or left bronchus, are most commonly used. After placement they may dislocate due to changes in the patient`s position. The tube position is finally confirmed using a fiberoptic bronchoscope as in about 48% of patients its positioning is improper despite earlier confirmation by auscultation [8].

Muscle relaxation facilitates intubation. Non-depolarizing muscle relaxants are increasing common for this purpose. It is recommended to assess the extent of striated muscle relaxation by stimulation of the ulnar nerve in the wrist. The train-of-four (TOF) stimulation is widely used, i.e. a series of single stimuli used every 0.5sec [9].

TOF stimulation enables qualitative assessment of neuromuscular blockade. The TOF  response of 1-2 contractions  means that 90-95% of receptors of the neuromuscular junction is blocked. Such a blockade is sufficient for intubation. The extent of striated muscle relaxation should be objectively assessed with accelerometry during which the acceleration at muscle contraction is measured and the train-of-four ratio (TOFR) calculated   [9, 10].

The cases of iatrogenic injuries to the larynx and tears of bronchi while using the double-lumen tubes have been described. Therefore, the procedure of intubation with such tubes should be performed safely - under good muscle relaxation - and using optimal anaesthetic agents to minimize the percentage of failed or complicated intubations [11, 12, 13, 14].

An increasingly high number of non-depolarizing muscle relaxants used in clinical practice is associated with the search for an ideal agent for intubation, which could replace suxamethonium. Moreover, there are no explicit recommendations based on studies regarding the safety of double-lumen tube intubations.

The objective of the present study was to assess the duration and conditions of endobronchial intubation with double-lumen tubes using selected muscle relaxants and to define the usefulness of suxamethonium for double-lumen tube intubations.

METHODS

The prospective, randomized, double-blind study was carried out.  Randomization was performed by choosing one of three balls, each with the name of a relaxant agent inside. The physician performing the intubation and assessing intubation difficulties did not know the type of an agent until completion of anaesthesia. An agent was routinely prepared and administered intravenously by the second anaesthesiologist involved in the study. The syringe label did not suggest the name of the agent used.

The study design, approved by the Bioethical Committee of the Silesian Medical University in Katowice, was carried out in patients of both genders scheduled for thoracic surgical procedures with thoracotomy.

The exclusion criteria were : the age < 18 and > 70 years, obesity (BMI >30), airway injuries, inability to visualize the true glottis on laryngoscopy,  history of chronic obstructive pulmonary disease, fever, and kidney and/ or liver failure.

All patients were intubated using the left-sided Robertshaw double-lumen tubes.

Depending on the muscle relaxant used, patients were allocated to 3 groups:

R – rocuronium - 1mg kg-1 followed by the continuous infusion 5-10 µg kg-1 min-1,

A – cis-atracurium - 0.1 mg kg-1 followed by the continuous infusion 1-1.5 µg kg-1 min-1,

S – suxamethonium – 1.5 mg kg-1, following precurarization with pancuronium continued in the maintenance dose of  8-10 µg kg-1 min-1 in the continuous infusion.

All groups of patients underwent induction of general anaesthesia with propofol using the target controlled infusion (TCI) to obtain the plasma level of 4 µg mL-1. The chosen agent was administered once the absolute bispectral index value was 40-65. The times between the agent administration and complete muscular blockade were recorded (25% of responses to TOF stimulation). Furthermore, the duration of intubation (since insertion of the laryngoscope to the oral cavity to placement of the tube in the left bronchus) was evaluated. After intubation the position of the tube was assessed by auscultation of the chest cavity and with the fiberoptic bronchoscope.  

General anaesthesia was maintained with propofol administered using TCI with the target plasma concentration of the agent of 2.5-3 µg kg-1. Intraoperative analgesia was administered using the epidural continuous bupivacaine  infusion in the dose of 0.25% and flow of 8-10 mL h-1. 

Possible difficulties in endotracheal intubations were assessed using the 4-point scale of  Mallampati. During direct laryngoscopy, intubation conditions were evaluated according to the Cormack-Lehan and Krieg scales.

The analysis involved the baseline demographic data of patients, conditions of intubation, duration of action of muscle relaxants, duration of intubation, potential repositions of the endotracheal tube.

The results were statistically analysed. Distributions of quantitative variables were verified using the Liliefors test. The analysis of variance was applied for variables of near-normal distribution, in the remaining cases the Kruskal-Wallis analysis of variance by ranks was used.

Intergroup differences were evaluated using the suitable post-hoc tests. Qualitative variables were compared using the Pearson ?2 test.

RESULTS

Out of 75 enrolled patients, 70 (93.3%) completed the examinations whereas 5 (6.6%) were excluded during the study according to the protocol assumed. The number of patients excluded during the study was similar in all groups. Group R consisted of 24 patients, group A of 23 and group S of 23 (Table 1).

No significant differences were found as for anticipated intubation-related difficulties and assessment of intubation conditions in all three groups of patients. However, repositions of double-lumen tubes were significantly more common in group S compared with group R and A (Table 2).

The time of action of relaxant agents from the completion of their administration to muscle relaxation (T1) and the time of intubation (T2) were comparable in the individual groups of patients (Table 3).

DISCUSSION

The disputes concerning the methods of anaesthesia for thoracic procedures with thoracotomy are mainly focused on types of ventilation, methods to separate the lungs and choices of a suitable anaesthetic of general as well as local action [15]. Less attention is paid to a proper agent enabling relaxation of striated muscles.

The use of aminosteroid agents, which do not release histamine, for muscle relaxation during thoracic anaesthesia seems well-grounded. This results from the fact that patients undergoing resection of the pulmonary parenchyma suffer from hypersensitivity of the bronchial tree and syndromes of chronic bronchial obstruction.  Rocuronium provides good conditions for intubation within short time (90 sec), which is a considerable advantage at difficult intubations with double-lumen tubes and may be an alternative to suxamethonium [9].

Rocuronium and suxamethonium were demonstrated to provide comparable intubation conditions and to have similar onset of action for intubation with normal tubes yet in high-risk patients [16]. It is believed that the dose of 0.9-1.2 mg kg-1 of rocuronium provides similar or even better intubation conditions after 60 sec than suxamethonium [17, 18, 19, 20]. In our study, similar times of relaxation and intubation as well as comparable intubation conditions were obtained with both agents.

The available literature lacks reports regarding conditions of endobronchial intubation with various relaxants or various doses of one agent. Therefore, all reports aimed at any comparisons, refer to traditional endotracheal intubations.

It is known that the standard rocuronium dose of 0.6 mg kg-1 provides good intubation conditions within 60-90 sec [21]. Moreover, it was demonstrated that standard doses of rocuronium (0.6 mg kg-1) and propofol for induction might ensure similar intubation conditions as suxamethonium [22, 23].

The study assessing the intubation conditions after rocuronium in the dose of 1.2 mg kg-1  or suxamethonium in the dose of 1.5 mg kg-1 showed significantly higher percentages of excellent intubation conditions in the group receiving suxamethonium. It remains unclear why such significantly worse intubation conditions were observed with extremely high doses of rocuronium. The drawback of this report is the lack of analysis of complications following 1.5 mg kg-1 of suxamethonium [24]. Our findings are contradictory to this report and rather support the majority of authors who agree that the rocuronium dose of 1.0 mg kg-1 provides ideal conditions for intubation.

Propofol, recommended and used by us for general anaesthesia induction, is considered an agent of unique properties likely to facilitate intubation [25]. Due to its effects abolishing the pharyngeal and laryngeal reflexes, propofol may be useful for intubation facilitating its accomplishment even without muscle relaxants [26]. However, this opinion is dubious as the advantages of propofol over other hypnotics (etomidate, thiopentone) have not been demonstrated in studies comparing the conditions of intubation with small doses of suxamethonium [27].

Although higher doses of rocuronium for induction ensure better intubation conditions and shorten the time between its administration and intubation, the time of relaxation is prolonged, which should be taken into consideration once difficult intubation is anticipated [20, 28].

In the present study, the third relaxant - cis-atracurium - was used in the dose generally accepted as standard. Although the time of relaxation enabling intubation was the shortest one compared to the other two agents, the differences were not significant. According to other authors, excellent intubation conditions were achieved 60 sec after rocuronium administration in 80% of cases whereas with atracurium and vecuronium – only in 12.5% of patients. The neuromuscular blockade after this period was 55.1% for rocuronium, 9.2% for atracurium and 8.3% for vecuronium. The shortest time needed to provide maximal blockade was with rocuronium (313sec) compared to atracurium (391.9 sec) and vecuronium (331.9 sec). Such sensational results were obtained using the dose of 0.45 mg kg-1 [29].

Suxamethonium for fast and difficult intubation may soon become less useful [30]. At present, sugammadex - the agent binding with non-depolarizing aminosteroid relaxants, is being introduced on the market. The available studies demonstrate that after administration of rocuronium in the intubation dose of 1.2 mg kg-1, the suitably chosen dose of sugammadex enables reversal of deep neuromuscular blockade within 2 min [31, 32, 33]. Once this agent is widely available, the use of suxamethonium will become marginal.

CONCLUSIONS

Rocuronium, cis-atracurium and suxamethonium provide proper conditions for endobronchial intubation and comparable times of muscle relaxation as well as endobronchial intubation.

The usefulness of suxamethonium for double-lumen tube intubations is low.

..............................................................................................................................................................

REFERENCES

1.Theissen IL, Meissner A: Hypoxic pulmonary vasoconstriction. Anesthesist 1996; 45: 643-652.

2.Slinger P, McRae K, Winton T, Sander A, Zamora JE, Salpeter MJ: Arterial oxygenation during thoracic surgery: aof isoflurane and sevoflurane Anesth Analg 1998; 86: SCA40.

3.Senturk M, Layer M, Pembeci K, Toker A, Akpir K, Wiedemann K: Aof the effects of 50% oxygen combined with CPAP to the non-ventilated lung vs 100% oxygen on oxygenation during one-lung ventilation. Anasthesiol Intensivmed Notfallmed Schmerzther 2004; 39: 360-364.

4.Slinger PD, Kruger M, McRae K, Winton T: Relation of the static compliance curve and positive end-expiratory pressure to oxygenation during one-lung ventilation. Anesthesiology 2001; 95: 1096-1102.

5.Brzeziñski K, Nestorowicz A: Problemy znieczulenia do zabiegów wideotorakoskopii. Anaesthesiol Intensive Ther 1994; 26: 55-58.

6.Fujiwara M, Abe K, Mashimo T: The effect of positive end-expiratory pressure and continuous positive airway pressure on the oxygenation and shunt fraction during one-lung ventilation with propofol anesthesia. J Clin Anesth 2001; 13: 473-477.

7.Biondi JW, Schulman DS, Soufer R, Mattchay RA, Hines RL, Kay HR, Barasch PG: The effect of incremental positive end-expiratory pressure on right ventricular hemodynamics and ejection fraction. Anesth Analg 1988; 67: 144-151.

8.Benumof JL: The position of atube should be routinely determined by fiberoptic bronchoscopy. J Cardiothorac Vasc Anesth 1993; 7: 513-514.

9.Larsen R: Anestezjologia. Urban & Partner, Wroclaw, 2003: 142-150.

10.Ekman A, Flink R, Sundman E, Eriksson LI, Brudin L, Sandin R: Neuromuscular block and the electroencephalogram during sevoflurane anaesthesia. Neuroreport 2007; 18: 1817-1820.

11.Abe K, Mashimo T, Yoshiya I: Arterial oxygenation and shunt fraction during one-lung ventilation: aof isoflurane and sevoflurane. Anesth Analg 1998; 86: 1266-1270.

12.Beck DH, Doepfmer UR, Sinemus C, Bloch A, Schenk MR, Kox WJ: Effects of sevoflurane and propofol on pulmonary shunt fraction during one-lung ventilation for thoracic surgery. Br J Anaesth 2001; 86: 38-43.

13.Furugen C, Satoh K, Koh J, Sakaguchi Y, Yanagitani T, Kosaka Y: A-a2 during one lung ventilation under propofol anesthesia. Hiroshima Journal of Anesthesia 1997; 33: 21-23.

14.Kellow NH, Scott AD, White SA, Feneck RO: Comparison of the effects of propofol and isoflurane anaesthesia on right ventricular function and shunt fraction during thoracic surgery. Br J Anaesth 1995; 75: 578-582.

15.Schwarzkopf K, Schreiber T, Preussler NP, Gaser E, Huter L, Bauer R, Schubert H, Karzai: Lung perfusion, shunt fraction, and oxygenation during one-lung ventilation in pigs: the effects of desflurane, isoflurane, and propofol. J Cardiothorac Vasc Anesth 2003; 17: 73-75.

16.Ortiz-Gomez JR, Carrascosa F, Perez-Cajaraville JJ, Percaz-Bados JA, Anek C: Comparative study of intubating conditions at the first minute with suxametonium, rocuronium and different priming techniques of rocuronium. Eur J Anaesthesiol 2005; 22: 263-268.

17.Schultz P, Ibsen M, Østergaard D, Skovgaard LT: Onset and duration of action of rocuronium--from tracheal intubation, through intense block to complete recovery. Acta Anaesthesiol Scand 2001; 45: 612-617.

18.Andrews JI, Kumar N, van den Brom RH, Olkkola KT, Roest GJ, Wright PM: Alarge simple randomized trial of rocuronium versus succinylcholine in rapid-sequence induction of anaesthesia along with propofol. Acta Anaesthesiol Scand 1999; 43: 4-8

19.Li Wan Po A, Girard T: Succinylcholine: still beautiful and mysterious after all these years. J Clin Pharm Ther 2005; 30: 497-501.

20.Schmidt J, Irouschek A, Muenster T, Hemmerling T, Albrecht S: Atechnique accelerates onset of neuromuscular blockade at the laryngeal adductor muscles. Can J Anaesth 2005; 52: 50-54

21.Nigrovic V, Bhatt S, Amman A, Bengez R: Priming principle: simulation in a(PK-PD) model. Anesthesiology 2004;101: A1156.

22.Sosis M, Stiner A, Larijani G, Marr A: An evaluation of priming with vecuronium. Br J Anaesth 1987; 59: 1236-1239.

23.De Mey JC, Debrock M, Rolly G: Evaluation of the onset and intubation conditions of rocuronium bromide. Eur J Anaesthesiol 1994; 9 (Suppl.): 37-40.

24.Karcioglu O, Arnold J, Topacoglu H: Succinylcholine or rocuronium? Aof the effects on intubation conditions. Int J Clin Pract 2006; 60: 1638-1646.

25.Burburan SM, Xisto DG, Rocco PR: Anaesthetic management in asthma. Minerva Anestesiol 2007; 73: 357-365.

26.Wojcieszek E, Misio³ek H, Kucia H, Czy¿ewski D: Zarys zasad postepowania anestezjologicznego wwzeniach klatki piersiowej. a-medica press, Bielsko-Biala, 2001.

27.El-Orbany MI, Joseph N, Salem MR: Tracheal intubating conditions and apnoea time after small-dose succinylcholine are not modified by the choince of induction agent. Br J Anaesth 2005; 95: 710-714.

28.Bissinger U, Rex C, Lenz G: Intubation conditions following administration of atracurium and vecuronium. Bolus method versus priming techniqe. Anaesthesist 1996; 45: 512-517.

29.Chetty MS, Pollard BL, Wilson A, Healy TE: Rocuronium bromide in dental day case anaesthesia – awith atracurium and vecuronium. Anaesth Intensive Care 1996; 24: 37-41.

30.Rawicz M: Zmierzch suksametonium? Anaesthesiol Intensive Ther 2001; 33: 65-66.

31.Groudine S, Soto R, Lien C, Drover D, Roberts K: Adose-finding, phase II study of the selective relaxant binding drug, sugammadex, capable of safely reversing profound rocuronium-induced neuromuscular block. Anesth Analg 2007; 104: 555-556.

32.Kirkegaard-Nielsen H, Caldwell J, Berry P: Rapid tracheal intubation with rocuronium. Aaproach to determining dose. Anesthesiology 1999; 91: 131-136.

33.Sluga M, Ummenhoffer W, Studer W, Siegemund M, Marsch S: Rocuronium versus succinylcholine for rapid sequence induction of anesthesia and endotracheal intubation: aprospective, randomized trial in emergent cases. Anesth Analg 2005; 101: 1356-1361.

..............................................................................................................................................................

Address:

*Hanna Misiołek
Zakład Anestezjologii Klinicznej
Śląskiego UM w Katowicach
ul. 3 Maja13-15, 41-800 Zabrze
tel./fax: 0-32 370 16 17
e-mail: katanestz@sum.edu.pl

Received: 06.01.2009
Accepted: 10.03.2009