Application of an artificial neural network to predict postinduction hypotension during general anesthesia.

BACKGROUND: Perioperative hypotension is associated with adverse outcomes in patients undergoing surgery. A computer-based model that integrates related factors and predicts the risk of hypotension would be helpful in clinical anesthesia. The purpose of this study was to develop artificial neural network (ANN) models to identify patients at high risk for postinduction hypotension during general anesthesia. METHODS: Anesthesia records for March through November 2007 were reviewed, and 1017 records were analyzed. Eleven patient-related, 2 surgical, and 5 anesthetic variables were used to develop the ANN and logistic regression (LR) models. The quality of the models was evaluated by an external validation data set. Three clinicians were asked to make predictions of the same validation data set on a case-by-case basis. RESULTS: The ANN model had an accuracy of 82.3%, sensitivity of 76.4%, and specificity of 85.6%. The accuracy of the LR model was 76.5%, the sensitivity was 74.5%, and specificity was 77.7%. The area under the receiver operating characteristic curve for the ANN and LR models was 0.893 and 0.840. The clinicians had the lowest predictive accuracy and sensitivity compared with the ANN and LR models. CONCLUSIONS: The ANN model developed in this study had good discrimination and calibration and would provide decision support to clinicians and increase vigilance for patients at high risk of postinduction hypotension during general anesthesia.

Predicting hypotensive episodes during spinal anesthesia with the application of artificial neural networks.

Hypotension is one of the most frequent adverse effects of spinal anesthesia. Several factors might be related to the occurrence of hypotension. Predictions of the hypotensive event, however, had been addressed by only a few authors using logistic regression (LR) models. Artificial neural networks (ANN) are pattern-recognition tools that can be used to detect complex patterns within data sets. The purpose of this study was to develop the ANN-based predictive model to identify patients with high risk of hypotension during spinal anesthesia. From September 2004 to December 2006, the anesthesia records of 1501 patients receiving surgery under spinal anesthesia were used to develop the ANN and LR models. By random selection 75% of data were used for training and the remaining 25% of data were used as test set for validating the predictive performance. Five senior anesthesiologists were asked to review the data of test set and to make predictions of hypotensive event during spinal anesthesia by clinical experience. The ANN model had a sensitivity of 75.9% and specificity of 76.0%. The LR model had a sensitivity of 68.1% and specificity of 73.5%. The area under receiver operating characteristic curves were 0.796 and 0.748. The ANN model performed significantly better than the LR model. The prediction of clinicians had the lowest sensitivity of 28.7%, 22.2%, 21.3%, 16.1%, and 36.1%, and specificity of 76.8%, 84.3%, 83.1%, 87.0%, and 64.0%. The computer-based predictive model should be useful in increasing vigilance in those patients most at risk for hypotension during spinal anesthesia, in allowing for patient-specific therapeutic intervention, or even in suggesting the use of alternative methods of anesthesia.

Doxapram shortens recovery following sevoflurane anesthesia.

PURPOSE: A randomized, double blind controlled trial was undertaken to investigate the effect of doxapram on recovery times and bispectral index following sevoflurane anesthesia. METHODS: Upon completion of surgery under sevoflurane anesthesia, 60 adult patients were randomly allocated to receive either doxapram hydrochloride 1 mg.kg(-1) iv or saline placebo. Clinical recovery from anesthesia was assessed by time to eye opening on verbal command, hand squeezing on command, time to extubation, and the Aldrete recovery score. Bispectral index values, systolic blood pressure, and heart rate were recorded at baseline (before anesthesia), during surgery, and every minute for 15 min after administration of the study drug. RESULTS: Time to eye opening was shorter in the doxapram group compared with the control group (6.9 +/- 2.2 min vs 9.9 +/- 3.1 min, P < 0.05). Mean bispectral index scores were also higher in the doxapram group compared with the saline placebo seven to eight minutes following administration of the study medication (P < 0.05). More rapid emergence was associated with a greater increase in heart rate with doxapram (P < 0.05 compared with placebo), but no differences in systolic blood pressure responses were observed in comparison with placebo. CONCLUSION: We conclude that doxapram 1 mg.kg(-1) hastens early recovery from sevoflurane anesthesia, and this arousal effect correlates with higher bispectral index values.

Starting dose of gabapentin for patients with post-herpetic neuralgia--a dose-response study.

BACKGROUND: Gabapentin has been shown to provide pain relief for post-herpetic neuralgia at dosage of 1200 to 2400 mg/day. However, the initial dosing strategy has not been thoroughly investigated. The purpose of this study was to establish the initial dosing strategy in the treatment of the gabapentin-naive patients with post-herpetic neuralgia. METHODS: This clinical study was an open-label, randomized, time-sequence and controlled trial. Each gabapentin-naive subject was allocated to receive either 200 mg (100 mg, twice daily), 400 mg (100 mg, four times daily), or 600 mg (200 mg, three times daily) of gabapentin for three days. The analgesic effect and occurrence of dizziness, drowsiness, and fatigue were assessed at day 0 and day 3. RESULTS: A total of 61 subjects (32 male/29 female) were enrolled in this study. The intensity of pain was greatly improved in all three groups after three days of treatment (visual analog scale decreased from 6.5 +/- 1.6 to 4.5 +/- 2.1, P < 0.05). There was no statistically significant difference among subjects taking 200 mg, 400 mg, or 600 mg with respect to dizziness, drowsiness or fatigue. CONCLUSIONS: This study shows that elderly gabapentin-naive subjects no matter whether receiving 200, 400 or 600 mg/day of gabapentin benefited a moderate pain relief with minimal side effects at the first three days of treatment. Since starting with a minimal dose of 200 mg/day did not offer a better reduction of side effects, we suggest that 600 mg/day gabapentin could be a safe and effective starting dose for patients with post-herpetic neuralgia.

Intravenous lidocaine and ephedrine, but not propofol, suppress fentanyl-induced cough.

PURPOSE: The aim of this study was to evaluate the effectiveness of lidocaine, propofol and ephedrine in suppressing fentanyl-induced cough. METHODS: One hundred and eighteen patients were randomly assigned into four groups and the following medications were given intravenously: patients in Group I (n = 31) received normal saline 2 mL, Group II (n = 29) received lidocaine 2 mg.kg(-1), Group III (n = 30) received propofol 0.6 mg.kg(-1) and Group IV (n = 28) received ephedrine 5 mg. At one minute after the study medication, fentanyl 2.5 microg.kg(-1) was given intravenously within two seconds. The occurrence of cough and vital sign profiles were recorded within two minutes after fentanyl bolus by an anesthesiologist blinded to study design. RESULTS: Sixty-five percent of patients in the placebo group had cough, whereas the frequency was significantly decreased in Groups II (14%) and IV (21%). Although a numerically lower frequency of cough was noted in Group III (37%), it was not statistically different from that of the placebo group. SpO(2) decreased significantly in patients of Group III compared to placebo; one patient experienced hypoxemia necessitating mask ventilation. Patients in Group III showed a decrease in heart rate and systolic blood pressure (2 beats.min(-1) and 8 mmHg vs baseline). Patients in Group IV showed an increase in both measurements (5 beats.min(-1) and 8 mmHg vs baseline). No truncal rigidity was observed throughout the study. CONCLUSIONS: Intravenous lidocaine 2 mg.kg(-1) or ephedrine 5 mg, but not propofol 0.6 mg.kg(-1), was effective in preventing fentanyl-induced cough. The results provide a convenient method to decrease fentanyl-induced cough.

Outpatient penile implantation with the patient under a novel method of crural block.

Although local anaesthesia for penile implants has been substantially reported, its methodology, simplicity and reliability left room for improvement. We would like to report on an innovative penile crural block using local anaesthesia in patients who underwent penile implantation as outpatient surgery. From March 1987 to March 1991, a total of 21 organically impotent men, aged from 27 to 77 years, received penile prosthesis implantation. All these were performed under pudendal nerve block as an outpatient procedure. From August 1992 to January 2003 a proximal dorsal nerve block with peripenile infiltration and penile crural block was developed to replace the anaesthesia method of pudendal nerve blocks in 137 consecutive patients (aged from 35 to 83 years) undergoing penile implants. The anaesthetic effects and postoperative results with the crural block were very satisfactory. Common immediate side-effects included puncture of the vessels, subcutaneous ecchymosis, transient palpitations and dilation pain, but there were no significant late complications. In the group of pudendal nerve blockage, 42.9% patients (nine of 21) experienced severe aching pain over the perineum for 1-2 weeks postoperatively, whereas the newly developed method of crural block markedly reduced these adverse effects. This new anaesthetic method proved to be reliable, simple, and safe with fewer complications. It offers the advantages of less morbidity, preservation of patient's privacy, reduced adverse effects of anaesthesia, and a more-rapid return to activity with minimal complications.

The effect of desflurane on ameliorating cerebral infarction in rats subjected to focal cerebral ischemia-reperfusion injury.

To obtain more information on the cerebral ischemia and reperfusion injury under desflurane anesthesia, we compared the infarct volume and lactate dehydrogenase (LDH) activity in rats subjected to focal cerebral ischemia during different concentration of desflurane anesthesia. Male Long-Evans rats weighing 270-350 g were anesthetized with desflurane in air at 1.0, 1.25 or 1.5 MAC whereas rats in the control group received intraperitoneal chloral hydrate (400 mg/kg) anesthesia. Cerebral infarction was induced by microsurgical procedures with ligation of the right middle cerebral artery (MCA) and clipping of the bilateral common carotid arteries (CCA) for 60 minutes. The rats were sacrificed 24 hours later, serial brain slices of 2mm thickness were taken and stained for the measurement of the infarct area. Cellular damage was evaluated by measuring the LDH level in the plasma. Desflurane (1.0, 1.25 or 1.5 MAC by inhalation) and chloral hydrate (400 mg/kg; ip.) did not produce any changes in pH, blood gases, heart rate or mean arterial blood pressure. In the rats subjected to focal cerebral ischemia, the volume of infarction was significantly less in the desflurane groups in all three different concentrations than in the chloral hydrate group. The changes of LDH activity in plasma also correlated with the result of the infarct volume. Our study suggests that desflurane may offer a neuroprotective effect such as decreased infarct volume after focal cerebral ischemia.

General anesthetic management for diagnostic splenectomy in a patient with paraneoplastic pemphigus.

Paraneoplastic pemphigus (PNP) is an autoantibody-mediated mucocutaneous blistering disease that often occurs with confirmed or occult malignancy. It is often accompanied by extensive eruption of respiratory mucosa and can lead to respiratory failure. The indications for anesthetic management in patients with PNP are rare due to the high risk of generating further eruption of respiratory mucosa during intubation, with potentially disastrous consequences. We report the anesthetic management in a 43-year-old woman with PNP scheduled for diagnostic splenectomy. The surgery was postponed due to persistent hoarseness, diffuse oral-pharyngeal mucositis, and laryngeal erosion. Methylprednisolone 40 mg 3 times daily was prescribed for controlling the mucosa lesions. Two weeks later, after the improvement of mucosal lesions, direct laryngoscopic intubation and the scheduled splenectomy were performed under general anesthesia. Pathology of the spleen showed low-grade B-cell lymphoma had induced PNP. Flexible fiberoptic bronchoscopic examination revealed neither bleeding nor bullae formation in the trachea either immediately after intubation or before extubation. The tracheal mucosa is highly susceptible to mechanical stimulation with direct laryngoscopic intubation. Cuff inflation and positive pressure ventilation, awareness of the disease characteristics of PNP, a sufficient course of steroid therapy beforehand, and adequate mucosal protection are essential to the uneventful anesthetic management of the patient with PNP involving the respiratory tract mucosa.

Penile venous anatomy: an additional description and its clinical implication.

The human penile venous system has been well studied and described but the demonstration of extra venous channels in imaging films prompted us to seek refinement of our anatomical knowledge of this venous system. Cavernosography in 37 patients who had venous stripping surgery and now suffered recurrent erectile dysfunction consistently showed an independent vein, smaller than the deep dorsal vein, running almost in the same position of the deep dorsal vein even though the latter had been removed unequivocally in previous surgery. Cavernosography in 9 patients who underwent intraoperative films also demonstrated the presence of this cavernosal vein in addition to the deep dorsal vein. Meticulous dissection of the penis under the microscope was then performed in 21 male cadavers and we found a cavernosal vein coursing along each corpus cavernosum all the way distally to the glans and draining directly into the Santorini's plexus in 19 subjects. This is in contrast to the previous description that this cavernosal vein was a short vein in the penile hilum. Two sets of para-arterial veins, which have not been reported in the literature, were found to accompany each dorsal artery in all 21 subjects. This more extensive and extra venous drainage might have important implication for venous stripping surgery in the treatment of erectile dysfunction.

Neural network modeling to predict the hypnotic effect of propofol bolus induction.

Dose requirements of propofol to achieve loss of consciousness depend on the interindividual variability. Until now when propofol was administered by a single bolus, how to define the optimal individual dose and to assess its hypnotic effect have not been clearly studied. The goal of this study is to develop an artificial neural network model to predict the hypnotic effect of propofol on the basis of common clinical parameters. Ten parameters were chosen as the input factors based on the related literatures and clinical experiences. The bispectral index of EEG was used to record the consciousness level of patients and served as the output factor. The predictive results of neural net models were superior to that of clinician. This model could potentially help determine the optimal dose of propofol and thus reduce the anesthetic cost.

Myoclonic seizure in the postanesthesia care unit after thoracic laminectomy.

IMPLICATIONS: We report a patient who developed myoclonic seizure in the postanesthesia care unit after thoracic laminectomy. Expeditious diagnostic evaluation of unrecognized dura tear during surgery must be instituted immediately to avoid untoward sequelae. Specific treatment in addition to supportive care is required if the diagnosis is to be clearly identified.

Influence of testosterone on autotomy in castrated male rats.

Sex-related differences exist in nociception and gonadal steroids influence the analgesic response in animals and humans. As we have shown previously, estrogen could modify autotomy in female rats using the sciatic nerve transection model. To further characterize the relationship between gonadal steroid and nociception, the role of testosterone on autotomy in sciatic nerve sectioned rats was investigated. Twenty male rats were subjected to orchiectomy (ORX). Then ten rats received subcutaneous sesame oil and the other ten were treated with testosterone propionate in sesame oil (TP; 500 microg/day/rat). All the rats underwent sciatic nerve resection in left hind limb. Degree of self-mutilation was measured daily for 8 weeks. TP reinstatement resulted in significantly lower autotomy scores in orchiectomized rats. The results demonstrated that testosterone could modify the autotomy behavior, an indicator of neuropathic pain, in rats after nerve injury.

Can neostigmine reduce propofol injection pain?

BACKGROUND: Neostigmine has been found to cause peripheral analgesia. We used venous retention technique to evaluate whether neostigmine displayed peripheral analgesic effect in reducing propofol injection pain. METHODS: In a double blind fashion, 105 patients were randomly allocated to receive either 1 ml 0.5 mg neostigmine (Group N, n = 35), 1 ml 2% lidocaine (Group L, n = 35), or 1 ml normal saline (Group C, n = 35) as pretreatment to reduce pain on propofol injection. A pediatric T-connector linking with the i.v. catheter port was used for injection. Venous occlusion was made possible with a tourniquet before the intravenous administration of one of the three drugs. The tested drug was allowed to retain for one minute and then the tourniquet was released for propofol injection. Pain and side effect assessments were made after propofol injection. RESULTS: The incidence of propofol injection pain was 85% in normal saline group, 46% in neostigmine group and 6% in lidocaine group (P < 0.05 among groups). The tested drugs arrayed in order of increasing magnitude of intensity of pain upon propofol injection were lidocaine (mean rank 34.20), neostigmine (mean rank 50.42) and normal saline (mean rank 76.81) in sequence (P < 0.05 among groups). CONCLUSIONS: With one-minute venous retention, 0.5 mg neostigmine (1 ml) could produce peripheral analgesia to some degree in reducing propofol injection pain. However, its analgesic effect was inferior to 1 ml of 2% lidocaine.

Bispectral index monitoring during hypoglycemic coma.

Bispectral index (BIS) monitoring is gaining wide acceptance as a gauge of the hypnotic effect of anesthetics. However, change in BIS in relation to the mental status of diabetic patients due to hypoglycemia has not been reported to date. We describe a case in which BIS was found to correlate with a patient's level of consciousness and changes in blood glucose levels.

Anesthetic considerations in intracranial aneurysm surgery.

Rupture of an intracranial aneurysm generally has a poor outcome, though perioperative treatments have improved. At the present time, the important factors in the management of intracranial aneurysm surgery appear to be the maintenance of adequate cerebral perfusion pressure and the avoidance of hyperglycemia. Relevant features of the anesthetic management of this surgery are discussed.