Transient decreases in Bispectral Index without associated changes in the level of consciousness during photic stimulation in an epileptic patient.

This case report describes a patient with a history of epileptic seizures who showed unusual decreases in the Bispectral Index (BIS) attributable to the induction of abnormal slow electroencephalographic (EEG) waves by photic stimulation, without any associated decrease in his level of consciousness. After starting anticonvulsive therapy, photic stimulation no longer induced abnormal EEG activity nor decreased BIS values. These findings suggest that BIS values may not accurately reflect a patient's actual level of consciousness in the presence of epilepsy-related abnormal EEG activity and that the BIS monitor may be able to track such EEG changes.

Cerebral ischaemia during cardiac surgery in children detected by combined monitoring of BIS and near-infrared spectroscopy.

BACKGROUND: Children frequently suffer transient cerebral ischaemia during cardiac surgery. We measured cerebral ischaemia in children during cardiac surgery by combining two methods of monitoring. METHODS: We studied 65 children aged between 5 months and 17 yr having surgery to correct non-cyanotic heart disease using hypothermic cardiopulmonary bypass (CPB). During surgery, we measured the Bispectral Index (BIS) and regional cerebral haemoglobin oxygen saturation (SrO2) with near-infrared spectroscopy (NIRS). Cerebral ischaemia was diagnosed if both SrO2 and BIS decreased abruptly when acute hypotension occurred. In each patient, the relationship between SrO2 and arterial blood pressure (AP) was indicated by a plot of mean SrO2 against simultaneous mean AP. RESULTS: We noted 72 episodes of cerebral ischaemia in 38 patients. Sixty-three ischaemic events were during CPB. Cerebral ischaemia was less frequent in older patients. Cerebral ischaemia was more common and more frequent in children under 4 yr old. Haematocrit during CPB was lower and SrO2 was more dependent on AP in children under 4 yr. CONCLUSIONS: Children less than 4 yr of age are more likely to have cerebral ischaemia caused by hypotension during cardiac surgery. Ineffective cerebral autoregulation and haemodilution during CPB may be responsible.

Detection of cerebral hypoperfusion with bispectral index during paediatric cardiac surgery.

BACKGROUND: The bispectral index (BIS) may indicate changes in cerebral activity when the cerebral circulation is affected by acute hypotension. METHODS: We measured BIS and cerebral haemoglobin saturation (Sr(O(2))) by near-infrared spectroscopy in 10 children undergoing cardiac surgery. RESULTS: We noted 14 episodes of simultaneous decreases in Sr(O(2)) and BIS during acute hypotension in five children. An acute decrease in BIS, which coincided with a decrease in Sr(O(2)) suggesting a reduction in cerebral blood flow, was associated with acute slowing of the raw EEG waveforms. CONCLUSIONS: Our findings suggest that an acute decrease in BIS during acute hypotension indicates cerebral hypoperfusion, and that cerebral hypoperfusion caused by hypotension may occur frequently during paediatric cardiac surgery.

Attenuation of haemodynamic responses to tracheal intubation by the styletscope.

Tracheal intubation often causes a haemodynamic response probably generated by direct laryngoscopy. The StyletScope is a new intubation device that does not require direct laryngoscopy. We prospectively measured haemodynamic changes after tracheal intubation using the StyletScope. The increase of heart rate was less during tracheal intubation with the StyletScope when compared with the Macintosh laryngoscope.

[Evaluation of emergence from total intravenous anesthesia with propofol for long neurosurgery].

In six neurosurgical patients we examined their emergence from more than six hours of total intravenous anesthesia with propofol and fentanyl. The anesthesia was maintained properly with total intravenous anesthesia with propofol and fentanyl without nitrous oxide. We calculated the estimated blood concentration of propofol from the anesthesia record using a three-compartment pharmacokinetic model. The patients were extubated after they had shown good awareness. The average time for extubation was 18 minutes after discontinuation of propofol infusion. The mean estimated concentration of propofol at the extubation was 1.36 micrograms.ml-1 (range: 1.1-1.5 micrograms.ml-1). The estimated emergence times in these cases, also calculated with the pharmacokinetic model, correlated significantly with the time from discontinuation of propofol infusion to the patients' awakening. It was concluded, first, that the estimated concentration of propofol at extubation after long anesthesia was similar to that measured in common cases, and second, that we could reduce the emergence time at the tail end of long-sustained neurosurgery by avoiding the delay in emergence.

[Efficiency of bispectral index in anesthetic management of a patient with hypothyroidism].

A 72-year-old, female patient with severe hypothyroidism underwent tracheostomy using deltopectral flap. During the anesthetic management, we assessed the hypnotic level using the bispectral index and regulated the dose of general anesthetics to maintain the bispectral index at about 50. The general anesthetics caused a marked cardiovascular depression, but the condition was treatable with the intravenous administration of dopamine. Using these methods, we could anesthetize this patient safely without a prolonged awakening time from general anesthesia. Although the anesthetic requirement for patients with hypothyroidism is generally thought to be decreased, there is no practical index by which we can estimate the optimal dose of anesthetic agents for these patients. This case report shows that the assessment of the hypnotic level by the bispectral index can be utilized as an efficient index to determine the optimal dose of general anesthetics for patients with hypothyroidism.

[Anesthetic management for neonates with congenital cystic adenomatoid malformation].

We experienced two cases of congenital cystic adenomatoid malformation (CCAM) diagnosed by prenatal ultrasonography. The first case with type I CCAM underwent the resection of the right upper lobe 8 days after birth. Postoperative course was uneventful. The second case with type III CCAM developed non-immune hydrops, severe mediastinal shift, and polyhydroamnios at 29 weeks' gestation. At 30 weeks' gestation, cesarean section was performed. Immediately after birth, the resection of lung tumor for the neonate was performed. However, the neonate died on the 1st postoperative day.

[Anesthetic management for MIDCAB using the target controlled infusion and the bispectral index].

We report our experience in using the target controlled infusion (TCI) of propofol combined with the bispectral index (BIS) monitoring for anesthetic management of minimally invasive direct coronary artery bypass (MIDCAB) in a 43-year-old-male patient with angina pectoris. After premedication, the patient was connected to the monitor with electrodes for BIS monitor. Then, anesthesia was induced with fentanyl and propofol using TCI technique. When blood concentration of propofol reached 4 micrograms.ml-1, the trachea was intubated. Before starting the operation, we evaluated the relationship between blood concentration of propofol and the value of BIS, and the standard maintenance concentration of propofol was set at 3 micrograms.ml-1. When the concentration of propofol was 3 micrograms.ml-1, the value of BIS was about 60. Anesthesia was maintained with nitrous oxide and oxygen and continuous infusion of propofol using TCI technique. When necessary, we gave additional injection of fentanyl and vecuronium bromide. Furthermore, diltiazem was infused continuously for cardiac rate control, as well as infusion of nicorandil, nitroglycerine for prevention of coronary artery spasms, and prostaglandin. After the operation, the patient was alert in 8 minutes and we could extubate in 12 minutes. The use of TCI combined with BIS monitoring for maintenance of anesthesia for MIDCAB is useful and safe.

[Dorsal root identification using spinal endoscopy and electro-physiology].

We aimed to develop a method of accurately identifying the dorsal root for the corresponding peripheral afferent nerve under endoscopic observation. We developed an endoscope with an external diameter of 1.8 mm. After small laminectomy on the lower thoracic vertebrae, we inserted this endoscope carefully into the epidural and then subarachnoid spaces. We observed structures in these spaces with the endoscope. We tried to determine the spatial relationship between these electrodes and dorsal root. After identifying each space, we inserted two electrodes into the visualized space to record evoked potentials; a bipolar electrode (protocol 1) and a catheter-type eight polar electrode (protocol 2). Each pole could be distinguished by marks. To stimulate peripheral nerves, we inserted needle-type electrodes into Th 10, 11 and 12 intercostal nerves. We attempted to record potentials from dorsal surface of the cord generated by intercostal nerve stimulus. Protocol 1: We moved the position of the bipolar recording electrodes between Th 9 and L 1 by 1 cm increment, and obtained evoked potentials correspondingly. Protocol 2: We chose the neighboring pairs of poles sequentially from the tip of the catheter for bipolar recording. At the end of each experiment, we dissected the animal and checked the intercostal nerve originating from the root. With the endoscope, we could clearly observe structures in the epidural and subarachnoid spaces. We could record evoked potentials from the dorsal spinal cord with the electrodes located either in epidural or in subarachnoid spaces. Shapes of evoked potentials changed characteristically according to the relative position between the root and the electrode. The largest potentials were obtained when the electrode was nearest to the dorsal root, of which the peripheral nerve was being stimulated. By combining endoscopy with the electrophysiological technique, we could accurately identify the dorsal roots for the corresponding peripheral afferent nerves. This method may be used for the selective dorsal root blockade under the visual field.

[Effects of cardiac output on PETCO2 and PaCO2 during combined inhalational-epidural anesthesia].

We investigated the effects of cardiac output on PETCO2 in anesthetized patients. We studied 8 adult patients undergoing long-lasting lower abdominal surgery. Anesthesia was maintained with epidural combined with inhalational anesthesia. The minute ventilation volume was kept constant at 10 ml.kg-1 x 10 cycles.min-1. PETCO2, PaCO2, and cardiac index, (CI) by thermodilution method were measured simultaneously. PaCO2 was corrected for body temperature for comparison with PETCO2. Approximate value of alveolar dead space to tidal volume ratio was calculated as VD/ VTalv = (PaCO2-PETCO2)/PaCO2. The measurements were repeated every 10 to 20 minutes under the steady body temperature. One hundred and six sets of data were obtained from these patients. PETCO2 as well as PaCO2 correlated positively with CI, while VD/VTalv did not correlate with CI. PETCO2 correlated positively with PaCO2, while it did not correlate with VD/VTa1v. When examined in individual patients, PETCO2 correlated positively with CI in 7 patients. PaCO2 correlated positively with CI in 6 patients, while VD/VTa1v correlated negatively with CI only in 2 patients, in whom CI showed a large fluctuation. PaCO2 correlated positively with PETCO2 in 8 patient, while VD/VTa1v correlated negatively with PETCO2 only in 1 patient. By multiple regression analysis, VD/VTa1v change accounted for only 20.0 +/- 15.3% of PETCO2 change, while PACO2 or PaCO2 change accounted for 79.3 +/- 16.7%. Decreased CI was associated with a decrease in oxygen uptake (VO2), and PaCO2 correlated positively with VO2. Decreased CI was also associated with an increase in VA/Q, and PaCO2 correlated negatively with VA/Q. Thus, PETCO2 decreased with decreasing cardiac output. A decrease in PACO2 explained the decrease in PETCO2 better than an increase in VD/VT did. Decreased cardiac output caused hypocapnia through decreased CO2 production and/or increased ventilation to perfusion ratio i.e. relative hyperventilation.

[Low preoperative PaO2 in patients with ovarian and endometrial cancer].

We investigated preoperative PaO2 and changes of PaO2/FIO2 (P/F) during the operation in 40 patients with gynecologic malignancies (ovarian cancer (O group) = 14 cases, endometrial cancer (E group) = 14 cases, cervical cancer (C group) = 12 cases). Preoperative chest X-ray and respiratory function test of our patients were within normal ranges (% VC > or = 80, % FEV 1.0 > or = 70). There were no differences among 3 groups in age, height, weight, % VC, or % FEV 1.0. Preoperative PaO2 values in the O group and E group were significantly lower than the normal value (100--age/4). Preoperative PaO2 and P/F values in the O group were significantly lower in comparison with those in the C group. We suggest, therefore, that it is necessary to measure preoperative PaO2 in patients with ovarian and endometrial cancer.

[Aspiration pneumonia during the endotracheal intubation on the occasion of bladder perforation by TUR].

We report on two cases of aspiration pneumonia which developed during the endotracheal intubation after bladder perforation during TUR. The first case was a 79 y.o. male, who underwent TUR-P and lithotripsy under spinal and epidural anesthesia. The second case was a 69 y.o. male, who had undergone TUR-Bt under nitrous oxide-oxygen-enflurane anesthesia. General anesthesia was selected to perform an laparotomy when the diagnosis was made. They vomited a considerable amount of gastric content just after giving the drugs for induction. The chest X-rays revealed signs of aspiration pneumonia. These X-ray findings improved in a week using antibiotic therapy. Although TUR is performed as scheduled, vomiting may occur in the case of unexpected bladder perforation, which can cause aspiration pneumonia. In such emergency, we should insert a nasal tube before induction, press the cricoid (crush induction), or intubate with the patient awake.

[Usefulness of NODSS (nasal/oral discriminate sampling system) in end-tidal carbon dioxide gas monitoring].

We investigated the usefulness of nasal/oral discriminate sampling system (NODSS) that had been developed recently in order to obtain the accurate end-tidal carbon dioxide (PET(CO2)) from a spontaneously breathing patient through a nomal airway. Fifty patients were monitored using a capnograph with NODSS following extubation in the postanesthesia unit. PET(CO2) data were collected by means of nasal, oral or nasal/oral sampling. The levels of arterial carbon dioxide (PaCO2) were determined simultaneously. In addition to examining the correlation between PET(CO2) and PaCO2, we investigated the influence of method of anesthesia, age and respiratory rate on the (PaCO2 - PET(CO2)) gradient. In most patients without nasal obstruction breathing through the nostril, PET(CO2) determined by selective nasal sampling was closer to PaCO2 than those by oral or nasal/oral sampling. Furthermore, the mean (PaCO2 - PET(CO2)) gradient was 4.98 mmHg in patients aged over 60, while it was 2.02 mmHg in patients aged under 60, suggesting that PET(CO2) could not be a good index in elderly people. There was no significant difference in the mean (PaCO2 - PET(CO2)) gradient among different methods of anesthesia. In conclusion, NODSS was useful in determining PET(CO2) more accurately and estimating PaCO2 precisely when used in relatively young people by selective nasal or oral sampling.

[Postoperative pain relief by patient controlled analgesia using intravenous pentazocine].

Patient controlled analgesia (PCA) by intravenous pentazocine was performed to determine its efficacy and the dose required for the pain relief after gynecological or obstetric operations. After obtaining informed consent, studies were performed on 28 female patients (ASA I, II: Mean age 38.1 years: Mean weight, 53.8 kg) who had received gynecological or obstetric operations with lower abdominal incision. Anesthesia given was nitrous oxide and isoflurane combined with epidural anesthesia with 1% mepivacaine used only during the operation. Six patients had cesarian section under spinal anesthesia. No patients received opioid during anesthesia. PCA was performed with a Graseby PCA pump. Lockout time was 8 minutes and the bolus dose was 3 mg. In all the patients, satisfactory pain relief was obtained and no other analgesic was necessary. Mean initial dose was 169.4 micrograms.kg-1 and the mean doses used for following each 6 hours until 24 hours were 409.7, 368.6, 279.3 and 211.1 micrograms.kg-1 respectively. Evaluation of PCA by the patients after the procedure showed excellent (13 patients) good (12) and passable (3) analgesia. No significant complication was observed except temporary nausea in two patients. Satisfactory postoperative pain relief could be obtained by relatively small doses of pentazocine and adverse reactions related especially to sigma receptor could be avoided.

Pulmonary capillary pressure measured with a pulmonary arterial double port catheter in surgical patients.

We developed a pulmonary artery (PA) double port catheter technique for reliable clinical measurements of pulmonary capillary pressure (Ppc). In seven elective surgical patients, the PA double port catheter with the second PA port 1 cm proximal to the balloon was inserted. The two PA ports, connected to identical pressure measuring systems, provided the pulmonary arterial pressures (Ppa) distal and proximal to the balloon. After general anesthesia was stabilized, the two Ppas were measured simultaneously during a PA occlusion maneuver during 10 s of apnea. The instant of occlusion was determined precisely as the time when the two Ppa traces sharply diverged. A single exponential equation was fitted to the segment of distal Ppa tracing starting 0.3 s after the instant of occlusion. Ppc was determined as the value of the exponential fit extrapolated to time 0. In six of seven patients, PA occlusion occurred consistently in the early systolic phase regardless of the timing of balloon inflation. Mean Ppa, Ppc, and pulmonary arterial wedge pressure were 16.6, 11.8, and 7.6 torr. The ratio of venous to total resistance ranged from 0.37 to 0.54 (mean:0.46). We conclude that this technique is clinically feasible and valuable in precise definition of the instant of PA occlusion. By defining PA occlusion consistently, this technique can provide reliable Ppc estimation in the clinical settings.

Effects of isoflurane and fentanyl on ischemic myocardium in dogs: assessment by end-systolic measurements.

The effect of anesthetics on ischemic myocardium to which blood was supplied by a stenotic coronary artery was investigated in dogs. The ischemia was assessed by regional wall motion (ultrasonic dimension technique) using fractional shortening (FS) [(EDL - ESL)/EDL x 100] and end-systolic pressure-segment length relationships (ESPLR). The latter is considered to be a more load-independent measure of regional myocardial function. Isoflurane and fentanyl were chosen as anesthetics of current interest. On reducing the left circumflex coronary artery (LCX) flow to approximately 50% of its resting value, a decrease in FS and a rightward shift in ESPLR were observed in myocardium perfused by the LCX. Simultaneously, increases in FS were observed in the nonischemic area perfused by the left anterior descending coronary artery (LAD), which was most likely due to the intraventricular unloading effect. No significant changes of ESPLR were observed in the area supplied by LAD. Isoflurane induced a dose-dependent decrease in FS and a rightward shift in ESPLR in the ischemic myocardial segment, whereas fentanyl caused an increase in FS and tended to shift ESPLR leftward in the same area. The results suggest that isoflurane may have deleterious effects on preexisting myocardial ischemia, whereas fentanyl may not when loading conditions are taken into consideration. Fractional shortening and ESPLR seem to provide similar information about regional myocardial function.

Phasic capillary pressure determined by arterial occlusion in intact dog lung lobes.

In six open-chest dogs, electrocardiogram- (ECG) controlled pulmonary arterial occlusion was performed during the control period and during the infusions of serotonin and histamine. A temporal series of instantaneous pulmonary capillary pressure and the longitudinal distributions of vascular resistance and compliance were evaluated in the intact left lower lung lobe. In the control period, we found a significant phasic variation of pulmonary capillary pressure (Pc) with the cardiac cycle. The ratio of arterial to venous resistances (Ra/Rv) was 6:4, and the ratio of arterial to capillary compliances (Ca/Cc) was 1:11. During the infusions of serotonin and histamine, Pc showed similar phasic variations, despite significant hemodynamic changes induced by these agents. Serotonin predominantly increased Ra, whereas histamine predominantly increased Rv. The ratio of Rv to the total resistance decreased significantly from 0.42 to 0.32 during the infusion of serotonin and increased significantly to 0.62 during the infusion of histamine. The data suggest that phasic Pc determined by ECG-controlled arterial occlusion reflects the pulsatility in the pulmonary microvascular bed under control conditions and after alterations of the pulmonary vascular resistance by serotonin and histamine.