Anesth Analg 2008; 106:123-126
© 2008 International Anesthesia Research Society
doi: 10.1213/01.ane.0000297292.84620.2c
AMBULATORY ANESTHESIOLOGY
Propofol Causes Less Postoperative Pharyngeal Morbidity Than Thiopental After the Use of a Laryngeal Mask Airway
Yuan-Yi Chia, MD* ,
Shih-Wei Lee, MD*, and
Kan Liu, MD*
From the *Department of Anesthesiology, Kaohsiung Veterans General Hospital, and School of Medicine, National Yang-Ming University, and Institution of Health Care Management, National Sun Yat-Sen University, Taiwan.
Address correspondence and reprint requests to Dr. Yuan-Yi Chia, MD, Department of Anesthesiology, Kaohsiung Veterans General Hospital, 386 Ta-Chung First Road, Kaohsiung (813), Taiwan. Address e-mail to yychia{at}isca.vghks.gov.tw.
Abstract
The insertion of a laryngeal mask airway (LMA) may result in postoperative sore throat. The choice of induction drug on airway morbidity after LMA insertion may be important. We performed this study to compare the incidence of postoperative pharyngeal morbidity after the insertion of a LMA in 340 patients administered either 2 mg/kg propofol (group P) or thiopental 5 mg/kg (group T) for induction of anesthesia. Patients were maintained at 1–2 minimum alveolar anesthetic concentration sevoflurane in 50% oxygen/air. Spontaneous or assisted spontaneous ventilation was maintained. An investigator blinded to group allocation visited patients at 2, 12, and 24 h postoperatively. Adverse responses were noted (yes/no) at each time point including sore throat, sore mouth, sore jaw, hoarseness, dysphonia, and dysphagia. At 2 h postoperatively, the incidence of sore throat, dysphagia, and postoperative nausea and vomiting in group T was higher than in group P (24% vs 13% for sore throat, 15% vs 3% for dysphagia, 20% vs 11% for nausea, 14% vs 6% for vomiting, P < 0.05). The number-needed-to-treat to prevent sore throat and dysphagia was 10 and 8, respectively (95% confidence intervals, 5–43). We concluded that, when propofol, rather than thiopental, is used for the induction of anesthesia, it results in a lower incidence of early pharyngeal morbidity and postoperative nausea and vomiting after the insertion of a LMA.
Some reports indicate that the use of a laryngeal mask airway (LMA) causes less postoperative pharyngeal discomfort1,2 and dysphonia than tracheal intubation.3 The overall incidence of postoperative sore throat varies widely, ranging from 0% to 43%4 and may lead to patient dissatisfaction with anesthesia care.
Several factors contribute to these postoperative complications.2 Propofol provides greater depression of laryngeal reflexes (which is associated with less laryngospasm and postoperative dysphonia) and a lower incidence of postoperative nausea and vomiting (PONV) compared with thiopental.5 This prospective, double-blind study was conducted to investigate whether propofol is associated with less postoperative pharyngeal morbidity than thiopental when a LMA is used.
METHODS
Approval by the Human Investigation Committee of our hospital was obtained for the study. Written, informed consent was obtained from each patient. Patients aged 18–71 yr, ASA physical status I–III, scheduled to receive general anesthesia for elective orthopedic, plastic, gynecologic, genitourinary, ophthalmic, or ear-nose-throat procedures were included.
Patients in whom a LMA was contraindicated were excluded. Patients were randomly divided into two groups using a computer-generated table of random digits. After administration of oxygen and 1 µg/kg IV fentanyl, general anesthesia was induced with either 2 mg/kg propofol or 5 mg/kg thiopental IV. The induction drug was prepared with the concentration of 10 mg/mL (propofol) or 25 mg/mL (thiopental) in the Department of Pharmacy. The syringe containing the induction drug was covered so that both the person administering the induction drug and the patient were blinded to assignment group. Using a syringe pump, an anesthetic nurse injected 0.2 mL/kg of the induction drug for each patient. After loss of consciousness and eyelash reflex, an anesthesiologist blinded to group allocation inserted the LMA and monitored the course of anesthesia. A deflated LMA (LMA ClassicTM Laryngeal Mask Company Limited, Seychelles) was used for all patients. The size of the LMA was based on patient's body weight as suggested by the manufacturer's instruction manual. During insertion of the LMA into the pharynx, any patient movement (including head, hand, or body) was recorded. After LMA insertion, the cuff was inflated with just enough air to obtain a seal. We recorded the air volume and pressure required for inflation; LMA intracuff pressure was measured using a Control-Inflator device (VBM; Edizintechnik Industriegebiet Wittlensweiler, Freudenstadt, Germany). If the LMA did not provide an audible seal at 100 cm H2O intracuff pressure, a second attempt to insert the LMA was performed after a supplementary bolus of 1 mg/kg propofol or 2.5 mg/kg thiopental (equal to 0.1 mL/kg of either drug). If an adequate seal was not obtained after two attempts of LMA insertion, the airway was secured with an endotracheal tube, and these cases were not included into the data analysis. After successful insertion of the LMA, sevoflurane at 1–2 minimum alveolar anesthetic concentration in a mixture of oxygen and with a fresh gas flow of 2.0 L/min was adjusted to maintain adequate anesthesia. Spontaneous or assisted spontaneous breathing was maintained without the use of a neuromuscular blocking drug. At the completion of surgery, in the operating room, the LMA was removed and a facemask was routinely applied with 100% oxygen for 10 min. If any upper airway obstruction was noted, a nasopharyngeal airway was inserted. Patients were then sent to the postanesthesia care unit.
A single investigator, who was blinded to group allocation and not involved in the course of anesthesia, visited all patients at 2, 12, and 24 h postoperatively. Adverse responses were noted (yes/no) at each time point including sore throat (continuous pain independent of swallowing), sore mouth, sore jaw, hoarseness, dysphonia, and dysphagia (difficulty or pain provoked by swallowing). The side effects, such as nausea, vomiting, and pruritus, were evaluated and recorded (yes/no) at 2 and 12 h postoperatively. Analgesics used by the patient during their time in the postanesthesia unit were recorded. Patients were asked to record satisfaction about their anesthesia experience subjectively (yes/no) at the end of hospitalization. The reason for dissatisfaction was also noted. All data are presented as mean ± standard deviation (sd) or percentage. Parametric variables were analyzed by the Student's t-test. Nonparametric data were analyzed with Mann–Whitney U-test. The incidence of side effects and patient satisfaction were analyzed by the  2 test and Fisher's exact test as deemed appropriate. A value of P < 0.05 was chosen to represent statistically significant differences between population means. The number-needed-to-treat (NNT) with 95% confidence interval (95% CI) was calculated without separating the patients into first-attempt group and second-attempt group. Based on previous reports,6a priori power analysis indicated that 160 patients from each group would be a sufficiently large sample size to detect a reduction from 40% to 25% in incidence of sore throat, featuring a Type-I error of 0.05 and a power of 82%.
RESULTS
Three-hundred-forty patients were evaluated. However, one patient in the thiopental group (group T) was excluded due to need for endotracheal intubation and four patients in the propofol group (group P) did not complete the study after surgery due to medical interventions (e.g., chemotherapy) that may have impacted their outcomes. Thus, 335 patients were available for analysis, with 166 patients in group P and 169 patients in group T. Their demographic data and duration of surgery are presented in Table 1; there was no significant difference between groups. The occurrence of postoperative side effects is presented in Figure 1. Group P experienced less sore throat than group T at 2 and 12 hours postoperatively (13% vs 24% at 2 h, P = 0.016; 6% vs 15% at 12 h, P = 0.012, respectively), and there was less dysphagia (3% vs 15%, respectively, P < 0.001) at 2 h postoperatively. For patients requiring a second attempt at LMA insertion, there was a significant difference in the incidence of dysphagia (9.5% in group P vs 17.6% in group T, P = 0.04) at 2 h, but no difference at 12 and 24 h. The NNT to prevent a sore throat was 10 (95% CI: 5–43) at 2 h and 11 (95% CI: 6–43) at 12 h. For dysphagia at 2 h, the NNT was 8 (95% CI: 5–15). There was a significantly lower incidence of PONV for group P patients (nausea/vomiting: 11%/6%) at 2 h compared with group T (nausea/vomiting: 20%/14%, P = 0.023 for nausea, P = 0.018 for vomiting). There was no difference in the use of supplementary analgesic medication and patient satisfaction (91.1% vs 93.4%, P = 0.895) between groups. Patient dissatisfaction appeared to be mostly related to PONV, accounting for 6 of 11 ratings of dissatisfaction in group P and 10 out of 15 in group T. The relationship between sore throat and vomiting was analyzed and showed that Spearman correlation coefficient at 2 and 12 h postoperatively was 0.165 and 0.078, respectively; P value was 0.002 and 0.134, respectively; and r2 was 0.02 and 0.002, respectively.
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Figure 1. Postoperative follow-up of side effects such as sore throat, sore mouth, sore jaw, hoarseness, dysphonia, and dysphagia in patients who had the laryngeal mask airway successfully inserted on the first attempt. Significant difference in the incidence of sore throat between the propofol group (group P) and the thiopental group (group T) was noted at 2 and 12 h postoperatively. The incidence of dysphagia was also significantly different at 2 h postoperatively.
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DISCUSSION
We found that patients who received propofol for induction of anesthesia to facilitate the insertion of a LMA had a lower incidence of postoperative sore throat and dysphagia compared with anesthesia induced using thiopental. In addition, the incidence of PONV was significantly less in patients receiving propofol than those receiving thiopental during the immediate postoperative recovery period.
Many confounding variables affect the incidence of LMA-induced pharyngeal morbidity. Figueredo et al. found that postoperative discomfort was related to type of ventilation (spontaneous breathing or mechanical ventilation).7 Other controversial factors include the use of neuromuscular blocking drugs, the method of insertion,8 and the number of attempts. A previous review9 suggests that postoperative pharyngeal morbidity is associated with factors that produce direct trauma to the larynx and pharynx such as larger size LMA, larger air volume, or higher intracuff pressure.10 In our study, we found that the choice of induction drug for anesthesia may also play a role in the development of postoperative complications. The other possible confounding factors, as mentioned earlier, were either controlled or comparable between groups in our study. However, the large range of 95% CI of NNT implies that there may be other factors that we did not control for which could also reduce the incidence of postoperative pharyngeal morbidity after LMA anesthesia.
Dysphagia has been thought to be a unique complication related to LMA rather than tracheal intubation.3 The mechanism and influential factors are still controversial. One study found there was no relationship between postoperative dysphagia and LMA cuff pressure.10 However, Brimacombe et al.'s showed that patients with higher LMA cuff volumes had a higher incidence of postoperative dysphagia.11
The significant relationship between postoperative sore throat and vomiting, as indicated by the Spearman correlation coefficient, explained only 2% of vomiting at 2 h postoperatively, which does not indicate a direct cause-effect relationship. One limitation of our study is that we did not record the use of a nasopharyngeal airway as it was occasionally used to maintain a patent airway and its use may be associated with variable degree of trauma and upper airway morbidity.
In conclusion, induction with 2 mg/kg propofol was associated with less postoperative pharyngeal morbidity including sore throat, dysphagia, and PONV after the insertion of a LMA than with 5 mg/kg thiopental. However, the incidence of supplementary use of analgesia and satisfaction with anesthesia care were similar.
Footnotes
Accepted for publication September 13, 2007.
Supported, in part, by VGHKS95-055 and The CY Foundation for Advancement of Education, Sciences and Medicine.
REFERENCES
- Zimmert M, Zwirner P, Kruse E, Braun U. Effects on vocal function and incidence of laryngeal disorder when using a laryngeal mask airway in comparison with an endotracheal intubation. Eur J Anaesthesiol 1999;16:511–5[Web of Science][Medline]
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- Rieger A, Brunne B, Hass I, Brummer G, Spies C, Striebel HW, Eyrich K. Laryngo-pharyngeal complaints following laryngeal mask airway and endotracheal intubation. J Clin Anesth 1997;9:42–7[Web of Science][Medline]
- Brimacombe J, Keller C. Bleeding, dysphagia, dysphonia, dysarthria, severe sore throat, and possible recurrent laryngeal, hypoglossal, and lingual nerve injury associated with routine laryngeal mask airway management: where is the vigilance? Anesthesiology 2004;101:1242–4[Web of Science]
- Barker P, Langton JA, Wilson IG, Smith G. Movements of the vocal cords on induction of anaesthesia with thiopentone or propofol. Br J Anaesth 1992;69:23–5[Abstract/Free Full Text]
- Tabo E. The LMA and sore throat. JJSCA 1991;15:1146–8
- Figueredo E, Vivar-Diago M, Munoz-Blanco F. Laryngo-pharyngeal complaints after use of the laryngeal mask airway. Can J Anaesth 1999;46:220–5[Web of Science][Medline]
- Dingley J, Whitehead MJ, Wareham K. A comparative study of the incidence of sore throat with the laryngeal mask airway. Anaesthesia 1994;49:251–4[Web of Science][Medline]
- McHardy FE, Chung F. Postoperative sore throat: cause, prevention and treatment. Anaesthesia 1999;54:444–53[Web of Science][Medline]
- Chandler M. Tracheal intubation and sore throat: a mechanical explanation. Anaesthesia 2002;57:155–61[Web of Science][Medline]
- Brimacombe J, Holyoake L, Keller C, Brimacombe N, Scully M, Barry J, Talbutt P, Sartain J, McMahon P. Pharyngolaryngeal, neck, and jaw discomfort after anesthesia with the face mask and laryngeal mask airway at high and low cuff volumes in males and females. Anesthesiology 2000;93:26–31[Web of Science][Medline]
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