Thermophysical Properties of Thermosoftening Nasotracheal Tubes.

Thermosoftening treatment of polyvinyl chloride (PVC) nasotracheal tubes (NTTs) can reduce the incidence and amount of epistaxis during nasotracheal intubation. The optimal thermal setting for thermosoftening treatment of NTTs without burn injury was investigated. Two composite types of PVC NTTs were used. Following withdrawal of the PVC NTTs from a bottle of water at 45 or 60°C, the changes in the surface temperature of the NTTs were measured by infrared thermography. Hardness of the NTTs at 25, 30, 35, and 40°C was measured. The incidence of epistaxis during nasotracheal intubation using thermosoftened NTTs was evaluated retrospectively. The surface temperature of both PVC NTTs dipped in 45 and 60°C water decreased to below body temperature 30 seconds after withdrawing them from the bottles. Although thermosoftening treatment proportionally decreased the hardness of both types of NTTs, the degrees differed according to their composition. When avoiding impingement of the NTT on the posterior wall of the nasopharynx, the incidence of mild and moderate epistaxis was 2.3%. Flexibility of PVC NTTs could be obtained by thermosoftening treatment at 60°C without burn injury. Thermosoftening treatment of PVC NTTs may be useful to avoid epistaxis during nasotracheal intubation.

Role of tube size and intranasal compression of the nasotracheal tube in respiratory pressure loss during nasotracheal intubation: a laboratory study.

BACKGROUND: Small nasotracheal tubes (NTTs) and intranasal compression of the NTT in the nasal cavity may contribute to increasing airway resistance. Since the effects of size, shape, and partial compression of the NTT on airway resistance have not been investigated, values of airway resistance with partial compression of preformed NTTs of various sizes were determined. METHODS: To determine the factors affecting the respiratory pressure loss during the nasotracheal intubation, physical and fluid dynamics simulations were used. The internal minor axes of NTTs in the nasal cavity of intubated patients were measured using dial calipers. In physical and fluid dynamics simulations, pressure losses through the tubular parts, compressed parts, and slip joints of NTTs with internal diameters (IDs) of 6.0, 6.5, 7.0, 7.5, and 8.0 mm were estimated under partial compression. RESULTS: The median internal minor axes of the 7.0- and 7.5-mm ID NTTs in the nasal cavity were 5.2 (4.3-5.6) mm and 6.0 (4.2-7.0) mm, respectively. With a volumetric air flow rate of 30 L/min, pressure losses through uncompressed NTTs with IDs of 6.0-, 6.5-, 7.0-, 7.5- and 8.0-mm were 651.6 ± 5.7 (6.64 ± 0.06), 453.4 ± 3.9 (4.62 ± 0.04), 336.5 ± 2.2 (3.43 ± 0.02), 225.2 ± 0.2 (2.30 ± 0.00), and 179.0 ± 1.1 Pa (1.82 ± 0.01 cmH2O), respectively; the pressure losses through the slip joints were 220.3 (2.25), 131.1 (1.33), 86.8 (0.88), 57.1 (0.58), and 36.1 Pa (0.37 cmH2O), respectively; and the pressure losses through the curvature of the NTT were 71.6 (0.73), 69.0 (0.70), 64.8 (0.66), 32.5 (0.33), and 41.6 Pa (0.42 cmH2O), respectively. A maximum compression force of 34.1 N increased the pressure losses by 82.0 (0.84), 38.0 (0.39), 23.5 (0.24), 16.6 (0.17), and 9.3 Pa (0.09 cmH2O), respectively. CONCLUSION: Pressure losses through NTTs are in inverse proportion to the tubes' IDs; greater pressure losses due to slip joints, acute bending, and partial compression of the NTT were obvious in small NTTs. Pressure losses through NTTs, especially in small NTTs, could increase the work of breathing to a greater extent than that through standard tubes; intranasal compression further increases the pressure loss.

Possible association between successful intubation via the right nostril and anatomical variations of the nasopharynx during nasotracheal intubation: a multiplanar imaging study.

PURPOSE: Most reported cases of nasopharyngeal laceration following impingement during nasotracheal intubation involved tube insertion via the right nostril. We postulated that recesses on the posterior wall of the nasopharynx might be associated with tube impingement. Using multiplanar imaging and clinical statistics, we evaluated whether anatomical variations in the recesses are related to successful intubation via the right nostril. METHODS: Using multiplanar computed tomography (CT) images of 97 patients, we investigated the locations of recesses relative to the mid-sagittal plane, nasal floor plane and posterior end of the nasal septum, and their shapes. Incidents of impingement of the tube during nasotracheal intubation and the shapes of the fossa of Rosenmüller on CT images were retrospectively evaluated in 170 patients. RESULTS: Eustachian tube orifices were located approximately 10 mm laterally from the sagittal plane, and approximately 10 mm above the nasal floor plane. The fossa of Rosenmüller was vertically elongated and located 7 mm laterally from the mid-sagittal plane. Pharyngeal bursae were found in 15 % of the subjects. Patients with failed insertion via the right nostril due to impingement frequently had a wide opening of the fossa of Rosenmüller. CONCLUSIONS: Successful intubation via the right nostril is related to the anatomy of structures on the posterior nasopharyngeal wall, particularly recesses located close to the path of nasotracheal tube insertion. Nasopharyngeal anatomical variations should be considered when one notices any resistance to advancement of the tube into the nasopharynx during nasotracheal intubation.

Roles of endotracheal tubes and slip joints in respiratory pressure loss: a laboratory study.

PURPOSE: The endotracheal tube (ETT) constitutes a significant component of total airway resistance. However, a discrepancy between measured and theoretical values has been reported in airway resistance through ETTs. The causes of the discrepancy were estimated by physical and rheological simulations. METHODS: The pressure losses through total lengths of ETTs and slip joints under a volumetric flow rate of 30 L/min were measured, and the pressure losses through the tubular parts of ETTs with internal diameters (IDs) of 6.0-, 6.5-, 7.0-, 7.5-, and 8.0 mm were measured. The Reynolds number of each setting was calculated, and the pressure losses through the total length of the ETT, the tubular part, and the slip joint of each size of tube were estimated. RESULTS: The Reynolds numbers were >5000 in all sizes of ETTs. Measured pressure losses were larger in small sized ETTs than in large sized ETTs-520.9 Pascals (Pa) in 6.0-mm ID and 136.4 Pa in 8.0-mm ID tubes. The measured pressure losses through the tubular part were comparable to the predicted values. The measured pressure losses through the slip joints were larger than the predicted values, and they accounted for approximately 25-40% of total pressure losses of the ETTs. CONCLUSION: Especially in small sized tubes, the pressure loss through the slip joint accounts for a large percentage of the total pressure loss through the ETT. The pressure loss through the slip joint may play a role in the discrepancy between measured and theoretical pressure losses through ETTs.

[Allergic reaction during anesthesia: two case reports].

We experienced two cases of serious and potentially life-threatening allergic reactions. The first patient was a 28-year-old male patient scheduled for surgery for cerebral arteriovenous malformations and another patient was a 66-year-old male patient scheduled for hepatic resection. After uneventful anesthetic induction, anesthesia was maintained with sevoflurane, air and oxygen. Both patients developed allergic reactions characterized by cardiovascular failure during anesthesia. Resuscitative treatment included rapid fluid infusion, administration of adrenaline and steroid. Both patients were successfully resuscitated without any lasting sequelae. The causative agent in one of these cases was probably a prophylactically used antibiotic, while that of the other case was a reaction to latex. Both patients showed elevated histamine and tryptase concentrations in blood samples. Recently, the incidence of allergic reactions to antibiotics and latex during anesthesia is increasing. Anesthesiologists should, therefore, be aware of the possibility of allergic reactions to all drugs and substances, especially to latex, during the perioperative period.

[Case of myocardial infarction during emergency clipping surgery of a cerebral aneurysm].

An 80-year-old woman with subarachnoid hemorrhage underwent emergency neck clipping of a cerebral aneurysm. She had previously undergone surgery for an abdominal aortic aneurysm 10 years before. Anesthesia was induced with propofol and maintained with a combination of fentanyl and sevoflurane (0.5-1.5%) in air and oxygen. Ventricular fibrillation occurred immediately before clipping of the aneurysm, in the absence of preexisting myocardial ischemia, and recurred 4 times thereafter during the surgery. The ventricular fibrillation was successfully treated with cardioversion. We administered catecholamines, nitrates, calcium antagonists, nicorandil and heparin, following which the patient's hemodynamics gradually improved. After the operation, the patient was transferred to the cardiovascular center of a neighboring university where she successfully underwent emergency percutaneous transluminal coronary angioplasty. The patient was discharged from hospital 10 days later without any complications. Patients undergoing vascular surgical procedures or having a preoperative history of prior vascular surgery are at high risk for perioperative myocardial infarction. It is necessary to perform cardiac examination, including coronary angiography, preoperatively in such patients, even in those who are otherwise asymptomatic.

Anesthetic management for the minimally invasive Nuss procedure in 21 patients with pectus excavatum.

The aim of this study was to assess the anesthetic management and postoperative analgesic effect of continuous epidural infusion for the minimally invasive Nuss procedure. A total of 21 operated cases were analyzed retrospectively. Thoracoscopy was used in all cases. General anesthesia with endotracheal intubation was induced and maintained with oxygen, air, sevoflurane, and fentanyl in all cases. Thoracic epidural anesthesia was performed after induction at the level between Th4 and 12. When the bar was placed via insertion under the sternum, six patients exhibited sinus tachycardia and one showed premature atrial contraction for 2-4 beats before recovering spontaneously within 1 min. Operations were uneventful. The mean operating time was 115 min and anesthetic time was 193 min. In X-ray findings, residual pneumothorax and pleural effusion were found in seven (33.3%) and eight (38.0%) patients, respectively. In all cases, these symptoms were resolved spontaneously within 5 days. Epidural fentanyl (0.3 microg.kg(-1).h(-1)) in 0.125% bupivacaine (0.15 ml.kg(-1).h(-1)) or 0.2% ropivacaine (0.15 ml.kg(-1).h(-1)) were used for 3 days to relieve postoperative pain. Postoperatively, 12 (57.1%) patients required no additional analgesics, and 4 (19.0%) patients required a single dose of dicrofenac sodium or pentazocine. Although the Nuss procedure is minimally invasive, we should pay attention to the possibility of many intra- and postoperative complications. Continuous epidural infusion of fentanyl with local anesthetics provides effective postoperative pain relief and prevents complications such as bar displacement after the Nuss procedure.

Volatile anesthetics constrict pulmonary artery in rabbit lung perfusion model.

Volatile anesthetics are generally considered to possess a vasodilator action. Some of their actions on pulmonary vessels, however, are not clearly understood. We examined the effects of various volatile anesthetics on pulmonary vessels using an in situ rabbit isolated-lung perfusion model. We prepared a rabbit constant-flow lung-perfusion model by sending blood to the pulmonary artery and removing blood from the left atrium, and observed the changes in pulmonary arterial perfusion pressure caused by inhalation of 0.5, 1, 2, and 3 minimum alveolar concentration (MAC) volatile anesthetics: halothane, enflurane, isoflurane, and sevoflurane, in random order. These volatile anesthetics increased pulmonary arterial perfusion pressure in a dose-dependent manner and caused the pulmonary arteries to constrict. In particular, halothane at all concentrations induced significantly greater pulmonary vasoconstriction than the other volatile anesthetics. Therefore, it is suggested that volatile inhalation anesthetics induce the pulmonary arteries to constrict, and halothane exhibits the most potent pulmonary vasoconstrictor effect among the volatile anesthetics tested.

Transcutaneous cisternal puncture for sampling of cerebrospinal fluid in awake rat.

Reported cisternal puncture methods require the anesthetization and fixation of an animal within a stereotaxic frame. To determine the effect of anesthesia and animal fixation on the central nervous system (CNS), amino acid concentrations of cerebrospinal fluid (CSF) sampled by transcutaneous cisternal puncture were compared among awake rats, pentobarbital-anesthetized rats and pentobarbital-anesthetized rats fixed in a stereotaxic frame. Although the concentrations of many amino acids in the CSF of pentobarbital-anesthetized rats were lower than in awake rats, use of the stereotaxic frame resulted in significantly increased amino acid concentrations in the CSF. These data indicate that CSF sampling by transcutaneous cisternal puncture from awake rats is a suitable method for serial measurement of drug effects on the CNS.