Muscle Relaxants and Laryngeal Local Anesthetics for Laryngeal Mask Airway Insertion Decreasing Propofol in Elderly (LMA)

Muscle Relaxants and Laryngeal Local Anesthetics for Laryngeal Mask Airway Insertion Decreasing Propofol in Elderly

The Impact of Using Muscle Relaxants and Laryngeal Local Anesthetics for Laryngeal Mask Airway (LMA) Insertion on Hemodynamics and Induction Anesthetics Dosage in Elderly

Laryngeal mask airway (LMA) is currently the most widely used supraglottic airway device with advantages of simple and fast placement, reduced anesthesia drug use, more stable hemodynamics, and less throat discomfort after anesthesia compared to endotracheal intubation. Some studies claimed the use of muscle relaxants or local anesthetics (sprays or lubricants containing local anesthetics) for the throat before LMA placement can reduce the dosage of induction agents and postoperative throat complications. In modern society, more and more elderly people undergo elective surgery with the need of general anesthesia. However, they are the more vulnerable population with tendency of greater hemodynamic changes with more induction agent usage. Propofol is one of the most used induction agents which may lead to a drop in blood pressure. The objective of this study is to observe whether the dose of propofol and the changes in hemodynamics can be reduced by using muscle relaxants or laryngeal local anesthetics in elderly who receiving general anesthesia with LMA insertion.

Muscle relaxants, Laryngeal local anesthetics, Laryngeal mask airway, Laryngeal Masks, LMA, Propofol, Elderly, Aged

The subjects received laryngeal local anesthetics (10% lidocaine spray), intravenous cisatracurium 0.12 mg/kg, and propofol before laryngeal mask airway placement. The predetermined dosage of propofol for the first subject is 1 mg/kg.

The subjects received laryngeal local anesthetics (10% lidocaine spray), intravenous normal saline as a substitute for cisatracurium, and propofol before laryngeal mask airway placement. The predetermined dosage of propofol for the first subject is 1.25 mg/kg.

The subjects received normal saline spray as a substitute for laryngeal local anesthetics (10% lidocaine spray), intravenous cisatracurium 0.12 mg/kg, and propofol before laryngeal mask airway placement. The predetermined dosage of propofol for the first subject is 1 mg/kg.

The subjects received normal saline spray as a substitute for laryngeal local anesthetics (10% lidocaine spray), intravenous normal saline as a substitute for cisatracurium, and propofol before laryngeal mask airway placement. The predetermined dosage of propofol for the first subject is 2 mg/kg.

The dosage of intravenous propofol for the first subjects was predetermined for each arm, and the dosage for the subsequent subjects would be determined according to the response of the previous subjects using the Dixon's up-and-down method with a step size of 0.25 mg/kg. If the subjects had no movement and stable hemodynamic status during and after the laryngeal mask airway (LMA) placement, the predetermined dosage of propofol for the subsequent subject would be decreased by 0.25 mg/kg. On the other hand, if the subjects had obvious movement, failure to LMA placement, and significant hemodynamic changes, the predetermined dosage of propofol for the subsequent subject would be increased by 0.25 mg/kg.

The minimal propofol requirement dose was defined as the median effective dose (ED50) of movement or increased mean arterial pressure (MAP) to no movement or stable MAP. The ED50 is the average of the crossover midpoints found during conducting the Dixon's up-and-down method.

Using the non-invasive blood pressure machine to collect the systolic blood pressure, diastolic blood pressure, and mean arterial pressure

Laryngospasm is defined as airway obstruction with assumption that LMA is correctly placed, which is also a factor for evaluating the condition of LMA insertion

Inclusion Criteria: American Society of Anesthesiologists (ASA) physical status I-III Age: over 65 years Elective orthopedic surgery undergo general anesthesia in supine position Exclusion Criteria: Anticipated difficult airway (Mallampati score 3-4), limited mouth opening, intra-oral and pharyngeal pathology Risk of pulmonary aspiration of gastric contents (full stomach) Obesity (Body mass index > 35) Significant lung abnormalities (low lung compliance, high airway resistance, impaired oxygenation) Loosening teeth Allergic to Cisatracurium or Lidocaine Failure in successful LMA insertion after second attempts