Comparative Effects of Laryngeal Mask Airway and Endotracheal Tube Insertion on Intraocular Pressure in Children Mehernoor F. Watcha, Julia L. Stevens, MD
MD,
Paul F. White, PhD,
MD, FFARACS, Lawrence
Tychsen,
MD,
and
Departments of Anesthesiology and Ophthalmology, Washington University School of Medicine, St. Louis, Missouri
Intraocular pressure (IOP) measurements in children are frequently performed under halothane-nitrous oxide anesthesia; however, anesthesia face masks may limit access to the eyes, and tracheal intubation is associated with transient increases in IOP. Use of the laryngeal mask airway (LMA) permits the maintenance of a patent airway without the need for laryngoscopy and tracheal intubation. In a randomized study of 41 children, we compared the IOP, hemoglobin oxygen saturation, and hemodynamic responses to the insertion of an LMA or tracheal tube during a standardized steady-state anesthetic technique consisting of 1 MAC halothane and 66% nitrous oxide. Baseline measurements of IOP, hemoglobin oxygen saturation, heart rate, and arterial
A
ccurate, reliable intraocular pressure (IOP) measurements in children are difficult to perform without profound sedation or general anesthesia (13). A widely used technique involves the administration of halothane and nitrous oxide (N,O) through a face mask; however, the anesthesiologist's attempts to maintain an adequate airway by manipulation of the jaw and face mask can occasionally interfere with the surgeon's ability to measure IOP. In addition, unrecognized pressure on the globe of the eye by the face mask may be a potential source of error. Although tracheal intubation will secure the airway and provide better conditions for the measurement, it is associated with a n increase in IOP (3,4). The laryngeal mask airway (LMA) is a new device consisting of a cuff that forms a seal around the inlet of the larynx and a tube to direct gases to the larynx (Figure 1) (5-10). This method of maintaining airway control without tracheal intubation leaves the Accepted for publication May 15, 1992. Address correspondence to Dr. Watcha, Department of Anesthesiology, Children's Hospital of St. Louis, 400 South Kingshighway, P.O. Box 14871, St. Louis, MO 63110. 01992 by the International Anesthesia Research Society 0003-2999/92/$5.00
blood pressure were recorded and repeated within 15-30 s after insertion of the airway device and at 1-min intervals for 5 min. Insertion of the LMA required significantly less time (26 2 16 vs 39 I 17 s [mean * SD]) and was associated with higher hemoglobin oxygen saturation values compared with the tracheal intubation. The LMA did not increase IOP, heart rate, or arterial blood pressure above baseline values. In contrast, tracheal intubation was associated with significantincreases of IOP, heart rate, and arterial blood pressure. We concluded that the laryngeal mask offers advantages over tracheal intubation and the face mask for airway management in patients undergoing IOP measurements. (Anesth Analg 1992;75:355-60)
surgical field largely unobstructed and the anesthesiologist's hands free to perform other duties (5-9). However, data are not available on IOP changes when the LMA is used in children. This prospective, randomized study was designed to compare the IOP and hemodynamic responses associated with the insertion of an LMA and an endotracheal tube in children during halothane-N,O anesthesia.
Methods After obtaining approval from the Washington University Human Studies Committee and written informed consent from the parents (or legal guardian) of the child, we studied 41 healthy ASA physical status I or I1 children scheduled for elective strabismus surgery. We excluded children 5 kg (11). After loss of consciousness, the end-tidal N,O concentration was kept constant at 66% in oxygen. In addition, all patients received halothane to maintain a constant end-tidal concentration that by itself was equivalent to 1 MAC for the patient’s age (i.e., halothane end-tidal concentrations of 0.97% for 0.5-2.5 yr, 0.91% for 2 . 5 6 yr, and 0.87% for 7-11 yr). After vascular access was obtained, all patients received atropine (10 &kg) and atracurium (0.5mg/kg) intravenously a minimum of 10 min before baseline measurements were made. The end-tidal CO, tension was maintained between 32 and 45 mm Hg with gentle positive pressure ventilation (peak inspiratory
ANESTH ANALG 1992;75:355-60
pressure
MD,
Paul F. White, PhD,
MD, FFARACS, Lawrence
Tychsen,
MD,
and
Departments of Anesthesiology and Ophthalmology, Washington University School of Medicine, St. Louis, Missouri
Intraocular pressure (IOP) measurements in children are frequently performed under halothane-nitrous oxide anesthesia; however, anesthesia face masks may limit access to the eyes, and tracheal intubation is associated with transient increases in IOP. Use of the laryngeal mask airway (LMA) permits the maintenance of a patent airway without the need for laryngoscopy and tracheal intubation. In a randomized study of 41 children, we compared the IOP, hemoglobin oxygen saturation, and hemodynamic responses to the insertion of an LMA or tracheal tube during a standardized steady-state anesthetic technique consisting of 1 MAC halothane and 66% nitrous oxide. Baseline measurements of IOP, hemoglobin oxygen saturation, heart rate, and arterial
A
ccurate, reliable intraocular pressure (IOP) measurements in children are difficult to perform without profound sedation or general anesthesia (13). A widely used technique involves the administration of halothane and nitrous oxide (N,O) through a face mask; however, the anesthesiologist's attempts to maintain an adequate airway by manipulation of the jaw and face mask can occasionally interfere with the surgeon's ability to measure IOP. In addition, unrecognized pressure on the globe of the eye by the face mask may be a potential source of error. Although tracheal intubation will secure the airway and provide better conditions for the measurement, it is associated with a n increase in IOP (3,4). The laryngeal mask airway (LMA) is a new device consisting of a cuff that forms a seal around the inlet of the larynx and a tube to direct gases to the larynx (Figure 1) (5-10). This method of maintaining airway control without tracheal intubation leaves the Accepted for publication May 15, 1992. Address correspondence to Dr. Watcha, Department of Anesthesiology, Children's Hospital of St. Louis, 400 South Kingshighway, P.O. Box 14871, St. Louis, MO 63110. 01992 by the International Anesthesia Research Society 0003-2999/92/$5.00
blood pressure were recorded and repeated within 15-30 s after insertion of the airway device and at 1-min intervals for 5 min. Insertion of the LMA required significantly less time (26 2 16 vs 39 I 17 s [mean * SD]) and was associated with higher hemoglobin oxygen saturation values compared with the tracheal intubation. The LMA did not increase IOP, heart rate, or arterial blood pressure above baseline values. In contrast, tracheal intubation was associated with significantincreases of IOP, heart rate, and arterial blood pressure. We concluded that the laryngeal mask offers advantages over tracheal intubation and the face mask for airway management in patients undergoing IOP measurements. (Anesth Analg 1992;75:355-60)
surgical field largely unobstructed and the anesthesiologist's hands free to perform other duties (5-9). However, data are not available on IOP changes when the LMA is used in children. This prospective, randomized study was designed to compare the IOP and hemodynamic responses associated with the insertion of an LMA and an endotracheal tube in children during halothane-N,O anesthesia.
Methods After obtaining approval from the Washington University Human Studies Committee and written informed consent from the parents (or legal guardian) of the child, we studied 41 healthy ASA physical status I or I1 children scheduled for elective strabismus surgery. We excluded children 5 kg (11). After loss of consciousness, the end-tidal N,O concentration was kept constant at 66% in oxygen. In addition, all patients received halothane to maintain a constant end-tidal concentration that by itself was equivalent to 1 MAC for the patient’s age (i.e., halothane end-tidal concentrations of 0.97% for 0.5-2.5 yr, 0.91% for 2 . 5 6 yr, and 0.87% for 7-11 yr). After vascular access was obtained, all patients received atropine (10 &kg) and atracurium (0.5mg/kg) intravenously a minimum of 10 min before baseline measurements were made. The end-tidal CO, tension was maintained between 32 and 45 mm Hg with gentle positive pressure ventilation (peak inspiratory
ANESTH ANALG 1992;75:355-60
pressure
