Wei-Te Hung

Monitoring of Heparin-induced Anticoagulation with Kaolinactivated Clotting Time in Cardiac Surgical Patients Treated with Aprotinin

High-dose aprotinin appears to enhance the anticoagulant effects of heparin, as documented by increases in the activated clotting times (ACTs) during cardiopulmonary bypass; hence, some authorities have advocated reducing the dose of heparin in patients treated with aprotinin. An in vitro study by our group suggested that the increase of the ACT in the presence of aprotinin and heparin may be due to the use of celite as surface activator. We compared celite and kaolin as surface activators for the measurement of the ACT in cardiac surgical patients treated with aprotinin and in patients given no aprotinin. This double-blind, randomized, placebo-controlled study included 30 patients, of whom 14 received aprotinin and 16 received a placebo. Before, during, and after cardiopulmonary bypass, the ACT was measured with two Hemochron 400 systems with 12 mg of either celite (C-ACT) or kaolin (K-ACT) used as surface activator and with one Hepcon HMS system (HR-ACT), which uses kaolin as activator. The latter also was used for measurement of the blood heparin concentration. The ACTs of blood without heparin did not differ between aprotinin and control patients. During anticoagulation with heparin and cardiopulmonary bypass, the average C-ACTs were 784 +/- 301 s (aprotinin) and 496 +/- 120 s (control) (P < .001); the K-ACTs were 502 +/- 131 s (aprotinin) and 458 +/- 101 s (control) (P > .05); the HR-ACTs were 406 +/- 87 s (aprotinin) and 423 +/- 82 s (control) (P > .05), which was consistently less than C-ACT and K-ACT.(ABSTRACT TRUNCATED AT 250 WORDS)

Thromboelastogram fails to predict postoperative hemorrhage in cardiac patients

To determine the clinical usefulness of the thromboelastogram in the prediction of postoperative hemorrhage in cardiac patients, we related the results of routine coagulation tests (RCTs) and thromboelastography with the amount of chest tube drainage postoperatively in 101 patients requiring cardiopulmonary bypass. Our data indicated that there was no correlation between RCT results and thromboelastographic variables. No single variable of RCTs and thromboelastography correlated well with the amount of chest tube drainage postoperatively. Before the onset of cardiopulmonary bypass, the most frequent abnormalities detected by thromboelastograms were fibrinolysis and hypocoagulability resulting from factor deficiency. Hypercoagulability detected by thromboelastograms occurred in 13% of patients after cardiopulmonary bypass and usually was not detected by RCTs. The incidence of false-negative thromboelastograms and RCT results in patients who had excessive hemorrhage of unknown cause was 46% and 52%, respectively. The incidence of fibrinolysis as detected by thromboelastograms was similar before and after bypass, but only 2 of the 18 patients with fibrinolysis had excessive hemorrhage postoperatively. Our results indicate that neither RCTs nor thromboelastography predicts the likelihood of excessive hemorrhage in patients after cardiopulmonary bypass. The thromboelastographic results should be interpreted cautiously because of the high rate of unreliable results.

Retrospective analysis of surgery postponed or cancelled in the operating room

STUDY OBJECTIVE To analyze the reasons for postponement or cancellation of surgery in the operating room (OR), and to determine the effect on patient outcomes. DESIGN Retrospective analysis. SETTING University-affiliated hospital. MEASUREMENTS Over a 5-year period, 45,663 surgeries requiring anesthesia occurred. Surgery was postponed or cancelled in the OR for 67 patients (0.15%). Airway problems, change in medical condition, and change in surgical condition were the reasons recorded. Each patients surgical result was audited using medical charts and telephone calls for at least 6 months. MAIN RESULTS 33 cases (49.3%) were postponed from one day to 6 months (range, one to 165 days; median, 8 days). The scheduled surgeries for 21 (31.3%) patients were never performed; and 9 patients (13.4%) died during their hospitalization (range, one to 20 days; mean, 12.7 days). CONCLUSIONS Surgery was postponed or cancelled in the OR mainly for changes in medical condition (70.2%); either medical risk outweighed the benefits of surgery, or alternative treatments were used.

Leakage of disposable breathing circuits

STUDY OBJECTIVE To determine the sites and rates of the leakage of disposable breathing circuits. DESIGN Nonclinical, experimental study. SETTING Experimental laboratory. INTERVENTIONS To identify in vitro the leakage sites by bubble test and to measure the leakage rate by the increased oxygen (O2) flow needed to maintain the circuit pressure provided by an anesthesia machine previously verified to have no leaks. Breathing circuit pressures measured with a sphygmomanometer of 30, 50, 70, and 100 mmHg were studied. MEASUREMENTS AND MAIN RESULTS Ninety-seven disposable and three reusable breathing circuits from seven manufacturers were investigated for leakage. There was a linear relationship between the circuit pressure and O2 flow at which leaks occurred. No leakage was detected in reusable circuits at 30 mmHg of circuit pressure. Leakage was found in two of the six junctions between the patient adapter and the corrugated tubing in the reusable breathing circuits at a circuit pressure of 100 mmHg. In 90% of the disposable circuits tested, the leakage rate was less than 75 ml/min at 30 mmHg of circuit pressure, but there was a wide variation in the amount of leakage among the circuits of different companies. Almost all the leakage sites were located at connections in the circuit and not in the corrugated tubing. The most common site of leakage in the disposable circuits was the junction between the patient adapter end and the corrugated tubing (57%) rather than the swivel piece (40%). CONCLUSIONS Most disposable breathing circuits can be used safely for closed-circuit anesthesia, as the leakage volume is too small to be of clinical importance. The variation in the leakage rates stresses the importance of quality control of the connector seals.

Anesthetic management of dental procedures in mentally handicapped patients.

BACKGROUND Providing dental care to a mentally handicapped patient is a challenge to both dentist and anesthesiologist. This study was aimed to describe the anesthetic methods which were used to facilitate dental treatments in mentally handicapped patients at a medical university hospital in Taiwan during a three-year period. METHODS The data referring to anesthetic techniques to facilitate dental treatments during the period from Dec. 1, 1997 to Nov. 30, 2000 were retrospectively collected. In the period, there were four different anesthetic techniques in application: nasal mask technique combined with intravenous sedation, total intravenous anesthesia, laryngeal mask intubating general anesthesia and endotracheal intubating general anesthesia. Basic characteristics of patients were compared with student t-test between groups according to anesthetic technique used. Intraoperative and postoperative complications and complaints collected were analyzed by chi-square test between anesthetic techniques. P value less than 0.05 was considered statistically significant. RESULTS The anesthetic records of 1201 mentally handicapped patients who underwent dental procedures over the three-year period were reviewed. Anesthesia was accomplished with nasal mask technique combined with intravenous sedation in 10 patients, with intravenous anesthesia in 112 patients, with endotracheal intubation anesthesia in 249 patients and with reinforced laryngeal mask anesthesia in 826 patients. Four patients were excluded from study because of changing of anesthetic method during the dental procedure. The use of nasal mask combined with intravenous sedation and intravenous anesthesia caused a higher incidence of intraoperative hypoxemia (P < 0.05) in comparison with the groups of endotracheal intubation anesthesia and reinforced laryngeal mask anesthesia. Although patients anesthetized by intravenous anesthetics had less postoperative complaints or complications but the difference was not statistically significant (P > 0.05) when group comparison was made. Patients who were anesthetized by volatile agents through endotracheal tube had the highest rate of postoperative complication although the difference was of no significance (P > 0.05) when comparison between groups was made. CONCLUSIONS We provided four different anesthetic methods for 1197 mentally handicapped patients who underwent dental procedures in three years. All anesthetic methods had their advantages and disadvantages. Using reinforced laryngeal mask or endotracheal intubation for general anesthesia to facilitate dental procedures for such patients had greater intraoperative safety than other two methods. However, less postoperative complaints or complications were revealed with the methods of nasal mask combined with intravenous sedation and intravenous anesthesia.

Improving Laryngeal Mask Airway Insertion Success by Using Fentanyl or Succinylcholine as Adjunct in Propofol Induction

Purpose: The successful insertion of a laryngeal mask airway (LMA) during propofol induction requires a proper mouth opening and minimal obstructive airway reflexes. We hypothesized that the concurrent use of fentanyl or succinylcholine in a propofol induction could reduce the occurrence of airway reflex and increase the success rate of laryngeal mask airway insertion. Methods: We randomly allocated 60 enrolled patients (scheduled to undergo surgery under general anesthesia) into three treatment groups: (1) propofol 2 mg/kg only; (2) propofol 2 mg/kg with fentanyl 2 μg/kg; (3) propofol 2 mg/kg with succinylcholine 0.5 mg/kg. After premedication with atropine (0.01 mg/kg, intravenous), we recorded the interval between the introduction of the treatment and the time of jaw relaxation, any excitatory movements after administering the induction agents and, after inserting the laryngeal mask, checked their airway reflex. Students t test and Chi-square test were used to analyze the data. Results: Demographic data for all three groups were statistically identical. The concurrent use of fentanyl or succinylcholine during propofol induction significantly shortened LMA insertion time, decreased airway reflex, and increased the success rate of LMA insertion when compared to use of propofol alone. No process difference was found between the two adjuncts, fentanyl and succinylcholine. Conclusions: As an induction agent for the insertion of LMA, propofol alone (2 mg/kg ) is not recommended. Adding either fentanyl (2 μg/kg) or succinylcholine (0.5 mg/kg) significantly, and equally, improves the success rate. A further evaluation should be made to consider adverse postoperative effects.

Evaluation of airway leakage using reinforced laryngeal mask during dental anesthesia with spontaneous breathing.

BACKGROUND The purpose of this study was to evaluate whether manipulation or position change of the head during dental procedures for handicapped patients (mentally retarded) using a reinforced laryngeal mask airway for ventilation would lead to air leak. METHODS All patients had a reinforced laryngeal mask airway inserted after induction of anesthesia; anesthesia was maintained with sevoflurane. Normal saline stained with methylene blue was instilled into the oral cavity of the patient. Then, the patients laryngeal region was checked for blue staining with a fiberoptic bronchoscope. After dental treatment, the laryngeal region was checked again under fiberoptic bronchoscopy. The staining results were recorded and analyzed. RESULTS In one of 51 patients (1.96%), the laryngeal region was stained blue after the flexible laryngeal mask airway was inserted. In ten of 51 (19.6%) patients, the laryngeal area was stained blue after the dental procedure. One of the ten patients who had a leak because the laryngeal mask was pulled out during the dental procedure. And in another one patient endotracheal tube was placed in lieu of laryngeal mask due to severe leakage. No oxygen desaturation below 90% occurred in all patients. No major complications such as fever or aspiration pneumonia were reported. CONCLUSIONS The use of a reinforced laryngeal mask airway eliminates the complications due to endotracheal intubation and enhances the progress of the dental procedure. Although leakage may happen during dental manipulation, it usually does not raise serious problem. No serious complications such as aspiration were found in our cases. So a reinforced laryngeal mask airway may be considered to be another safe choice for maintenance of a patent airway in handicapped patients during dental procedures.

Evaluation of learning effectiveness in endotracheal intubation by the use of a laryngoscope in combination with a flexible fiberoptic bronchoscope.

BACKGROUND Accidental esophageal intubation may cause lethal complications when undetected. We developed a laryngoscope, which utilizes a laryngoscope blade incorporating with a flexible fiberoptic bronchoscope for teaching new learners. We compared two teaching methods, i.e. the traditional method and the new method we contemplated, for teaching new interns. METHODS We selected new interns as our study group. Everyone had six turns, four of which for the traditional method (T) and two of which for the new method (N), to perform the procedure under the guidance of a teaching supervisor. The interns were assigned randomly to one of three groups. Group 1 used the series of TTTTNN; group 2, TTNNTT; and group 3, NNTTTT. We used success or failure of intubation as the result of our evaluation. Statistical analyses were performed by chi-square test. RESULTS 84 interns performed 504 endotracheal intubation trials during a period of 4 years. There was a 91.7% success rate with the new method and a 78.9% success rate with the traditional technique (P < 0.05). The group to which the new method was initially taught achieved the highest success rate of intubation and the greatest feeling of satisfaction according to a self-evaluation record. Of the failed intubations, 82.4% were due to performing the procedure in more than one minute, 15.3% due to esophageal intubation and the remaining 2.3% due to contact bleeding of teeth or oral trauma. CONCLUSIONS By using the new teaching method, the supervisor could easily teach and assess the success of the new learners. Besides, esophageal intubation could be reduced to a minimum with subsequent increase of success rate.

Simultaneous Transtracheal Ventilation and Retrograde Tracheal Intubation in a Cannot Intubate-Cannot Ventilate Situation

A case of recurrent laryngeal cancer where the patient was in a cannot-intubate, cannot-ventilate (CICV) situation, and refused to have a tracheotomy despite a doctors recommendation. No family members were available at that moment to give consent for a tracheostomy. We performed a temporizing measure to achieve emergency ventilation and a second cricothyroidotomy for retrograde intubation. Retrograde intubation is not one of standard method for securing an airway. However, when the airway could not be secured and emergent tracheostomy was not available, this method was considered as a ”last resort” option.

The Timing of Fentanyl Administration as an Adjunct for Etomidate Induction in the Insertion of Laryngeal Mask Airway

Purpose: Without the use of a muscle relaxant, smooth insertion of a laryngeal mask airway (LMA) requires attenuation of airway reflexes to prevent gagging, coughing, or laryngospasm. Since fentanyl is a potent depressant of the upper airway reflex, the timing of fentanyl administration during etomidate induction may be an important factor in the successful insertion of a laryngeal mask airway. We compared the success rates of LMA insertion with various injection times of fentanyl given during etomidate induction. Methods: Ninety adult patients who were scheduled for general anesthesia were placed into one of the following groups: Group 1 (n=30), etomidate 0.3 mg/kg; Group 2 (n=30), fentanyl 2 pg/kg with immediate etomidate 0.3 mg/kg administration (n=30); or Group 3 (n=30), fentanyl 2 p/kg two minutes prior to etomidate 0.3 mg/kg administration during induction. After premedication with atropine 0.01 mg/kg, the time needed for jaw relaxation from the beginning of etomidate administration was calculated and recorded. The first check began 60 sec after etomidate administration, Subsequent checks were performed at 30 sec intervals up to 240 sec. Laryngeal mask airway was inserted when jaw relaxation was sufficient. After LMA insertion, any sign of airway irritation (e.g., coughing, swallowing, gagging, biting, hiccupping, and tongue movement) were noted. Results: There was no significant difference among the three groups with regard to demographic data, Inadequate jaw relaxation occurred in each group. Fentanyl given 2 mm before etomidate injection significantly reduced airway reflex better than etomidate alone or fentanyl administration immediately before etomidate injection. Among the three groups, fentanyl 2 pg/kg given 2 mm before etomidate injection had a significant greater success rate of LMA insertion than the other two groups. Conclusions: Without a muscle relaxant, etomidate is not a good induction agent for the insertion of LMA. The addition of fentanyl can decrease the time to LMA insertion as well as produce better jaw relaxation. Administration of fentanyl 2 pg/kg given 2 mm before etomidate injection could decrease airway reflex and increase the success rate of LMA insertion.