The use of intranasal nitroglycerin to prevent pressor responses during intubation in general anesthesia--a comparison of various doses.

BACKGROUND: Intranasal nitroglycerin (NTG) was first reported to successfully prevent an increase in arterial blood pressure following laryngoscopy and tracheal intubation by Hill et al. Various different effective dosages of NTG have been reported. Grover et al. indicated 0.75 mg of intranasal NTG to be the most suitable dose. However, no definite conclusion has yet been made. This study was designed to compare the efficacy of four different dosages of intranasal NTG (0.3, 0.5, 0.75, and 1.0 mg) in preventing pressor responses to laryngoscopy and tracheal intubation during the induction of general anesthesia. METHODS: One hundred patients (ASA I or II) scheduled for elective surgery were included. These study subjects were divided into five groups and randomly assigned to four different dosages of intranasal NTG and a placebo. Each group consisted of 20 patients. The NTG solution was administered 1 min before the injection of thiopental. Systolic arterial pressure (SAP), diastolic arterial pressure (DAP), mean arterial pressure (MAP) and heart rate (HR) were recorded before the induction of anesthesia (T1), before laryngoscopy (T2), and at 0, 3, and 5 min after tracheal intubation (T3, T4, and T5 respectively). RESULTS: In patients who received a placebo (control group), there were significant increases in SAP, MAP, HR and rate-pressure-product (RPP) associated with tracheal intubation. Tachycardia was noted in all experimental groups. The increases in MAP associated with tracheal intubation were significantly less in patients who received NTG of 0.5 mg or more but not 0.3 mg. Although 0.5 mg of NTG did attenuate the increases in SAP after tracheal intubation, the increases in SAP of the other three experimental groups were no less than that of the control group. Rate-pressure-product (RPP) values of the experimental groups were noted to be equal to or higher than those of the control group during the period of study. Contrary to the results of the study conducted by Grover et al., 0.75 mg of NTG did not attenuate the pressor responses. CONCLUSIONS: Intranasal NTG does not attenuate the pressor responses to laryngoscopy and tracheal intubation.

[A proper size of endotracheal tube for infant and young child--a retrospective study in Mackay Memorial Hospital].

BACKGROUND: There are more than 2000 pediatric patients receiving surgery in Mackay Memorial Hospital each year. Most of these surgery were performed under general anesthesia with endotracheal tube; therefore choosing an appropriate size of endotracheal tube becomes an important issue in our daily practice. METHODS: Our principle is to choose an uncuffed Mallinckrodt endotracheal tube with a proper internal diameter (ID), ranging from 2.5 mm to 6.5 mm, which could be suitably and gently inserted into the trachea under full muscle relaxation. The tube would then be immediately removed and replaced with a smaller one if facing obvious resistance during intubation. After intubation, a leak test was applied to ascertain that there was no excessive gas leakage. We reviewed all anesthetic records of elective pediatric surgery in the recent 6 years, and the patients whose age above 8.5 years old and body weight (Wt) above 30 kg were excluded from this study. Using age (6476 cases) and Wt (6406 cases) as our parameters, we analyzed these data according to the distribution of each size of uncuffed endotracheal tube (UCETT) in different age and Wt intervals and compared them with the recommended Western reports. RESULTS: Our results revealed that (1) the UCETT size increases as age or Wt increases; (2) considerable spread of UCETT sizes for different age and Wt intervals and basically represent as normal distribution; (3) for the case of even age equal or above 2 years old (up to 8 years old), the ID of the most frequently used UCETT can be memorized as (18 + age in years) divided by 4 or the outer circumference (OC) of the Mallinckrodt UCETT (in French unit, Fr) = 19 + age in years; and (4) Wt as a parameter for tube size selection was as powerful as age (94.76% vs. 94.65%). CONCLUSIONS: From our results, we concluded that "whatever method of predicting tube size is used, tracheal tubes 0.5 mm larger and smaller should be available at the time of intubation so that the proper size can be chosen when the glottis is visualized."

[4P- syndrome (Wolf-Hirschhorn syndrome) complicated with delay onset of malignant hyperthermia: a case report].

One 8-month-old female patient, weighted 5 kg, with congenital abnormality (4P- syndrome) underwent elective cheiloplasty for cleft lip and palate. Two hours later, with smooth anesthesia and operation, a life-threatening anesthetic complication of malignant hyperthermia occurred at pediatric intensive care unit. The immediate treatments were initially hyperventilating the patient with 100% O2 and cooling the patient with ice bags. Subsequently, intravenous dantrolene 2.5 mg/kg and symptomatic supportive care were administered successfully to treat the event. Upon reviewing the articles, we found that a congenital chromosome 4P deletion abnormality complicated with a delay onset of malignant hyperthermia has not been described previously.