Fentanyl treatment reduces GABAergic inhibition in the CA1 area of the hippocampus 24 h after acute exposure to the drug.

The effect of in vivo fentanyl treatment on synaptic transmission was studied in the CA1 area of the rat hippocampus. Animals were treated either with saline or fentanyl (4 x 80 microg/kg, s.c./15 min). Intracellular in vitro recordings were obtained, 24 h after treatment, from CA1 pyramidal neurons. No difference in pyramidal neuron basic membrane properties or postsynaptic membrane excitability was observed between neurons from saline- and fentanyl-treated animals. The peak amplitude of fast (f-) and slow (s-) components of IPSPs elicited in standard ACSF and the peak amplitude and rate of rise of isolated f- and s-IPSPs elicited in the presence of antagonists (CNQX, 10 microM; AP-5, 10 microM; CGP 55845, 1 microM; and bicuculline methochloride, 10 microM), in response to various stimulus intensities, was smaller in fentanyl-treated animals. Conversely, the rising slope of excitatory responses was similar in neurons from saline- and fentanyl-treated animals. Furthermore, in fentanyl-treated animals, lower stimulus strengths were required to elicit subthreshold excitatory responses of the same amplitude suggesting that acute exposure to fentanyl increases susceptibility of pyramidal neurons to presynaptic stimulation. GABA immunohistochemistry revealed lower GABA content in processes and neuronal somata suggesting diminished GABA release onto pyramidal neurons. We conclude that acute in vivo exposure to fentanyl is sufficient to induce long-lasting reduction in GABA-mediated transmission, rather, than enhanced excitatory transmission or modulation of the intrinsic excitability of pyramidal neurons. These findings provide evidence regarding the mechanisms involved in the early stages of tolerance development towards the analgesic effects of opioids.

The impact of the type of anaesthesia on cognitive status and delirium during the first postoperative days in elderly patients.

BACKGROUND AND OBJECTIVES: Postoperative confusion and delirium is a common complication in the elderly with a poorly understood pathophysiology. The aim of this study was to examine whether the type of anaesthesia (general or regional) plays a role in the development of cognitive impairment in elderly patients during the immediate postoperative period. METHODS: Forty-seven patients > 60 yr of age and undergoing major surgery were randomly allocated to receive either regional or general anaesthesia. The mental status of the patients was assessed preoperatively and during the first three postoperative days with the Mini Mental State Examination. The incidence of delirium was also examined during the same period with the use of DSM III criteria. RESULTS: Overall, during the first three postoperative days, the mean Mini Mental State Examination score decreased significantly (P < 0.001). However, this decline was very significant only in patients assigned to receive general anaesthesia (P < 0.001) compared to regional anaesthesia. Nine patients developed delirium but the type of anaesthesia did not affect its incidence. The only important factor for the development of delirium was preexisting cardiovascular disease irrespective of anaesthesia type (P < 0.025). CONCLUSIONS: Elderly patients subjected to general anaesthesia displayed more frequent cognitive impairment during the immediate postoperative period in comparison to those who received a regional technique.

Left ventricular function and cardiopulmonary performance following surgical treatment of morbid obesity.

BACKGROUND: It is well established that morbid obesity affects the respiratory system and the diastolic function of the heart. During exercise, cardiopulmonary reserve is exhausted because of augmented requirements, leading to a significant intolerance. A study was undertaken to investigate the influence of body weight loss on the characteristics of the left ventricle (LV) and on exercise capacity in obese patients before and 6 months, following vertical banded gastroplasty (VBG). METHODS: 16 morbidly obese individuals (BMI > 40 kg/m2) scheduled for VBG were studied. A symptom-limited cardiopulmonary exercise test and a complete transthoracic echocardiogram were performed 1 day before operation and 6 months postoperatively (after the patients achieved a body weight loss of > 20% of their pre-operative values). RESULTS: Exercise duration increased significantly 6 months following surgery. The mean O2 consumption at peak exercise (peak VO2) and at the anaerobic threshold (VO2AT) was significantly higher after weight loss. 6 months after VBG the LV thickness decreased significantly. Regarding the diastolic indices, isovolumic relaxation time (IVRT) and early/late (E/A) velocity ratio, there was a significant improvement after weight loss. Simple linear regression analysis revealed that peak VO2 and VO2AT were significantly correlated with IVRT and E/A velocity ratio. CONCLUSIONS: Weight loss after VBG improves the cardiac diastolic function and this is associated with an improvement in cardiopulmonary exercise performance. Left ventricular filling variables could be considered among the most important determinants of exercise intolerance in obese individuals.

Obesity-associated disorders before and after weight reduction by vertical banded gastroplasty in morbidly vs super obese individuals.

BACKGROUND: The amount of excess weight which must be lost in order to cure or to improve disorders associated with obesity remains unknown. This study was designed to compare super obese and morbidly obese patients in terms of weight reduction following VBG and to investigate the effects of postoperative weight changes to preexisting co-morbidities. METHODS: 125 patients underwent VBG. Group A consisted of 80 morbidly obese patients (64%) and group B consisted of 45 super obese patients (36%). Preoperative examination was planned to identify and determine the severity of any disorders associated with obesity, that the patients may have had. Following VBG, all patients were followed-up at regular time periods, for at least 2 and up to 4 years. The progress of preexisting co-morbidities was evaluated and carefully recorded. RESULTS: Among the 80 patients of Group A, there were 240 total co-morbidities (3 per patient), and in group B there were 196 co-morbidities (4.35 per patient) preoperatively. Dyspnea during fatigue and arthritis were found at statistically higher incidence in the super obese category. At the end of the second postoperative year, greater weight loss in terms of number kilograms was seen in patients in group B, but these patients did not reach a BMI lower than 35, while patients in group A had mean BMI below 30. In group A, 66% of the co-morbidities completely resolved, 19% significantly diminished and 15% remain unchanged. In group B, the respective percentages were 53%, 27.5% and 19.5%. However, after weight reduction by VBG a significant number of co-morbidities remain in the super obese patients (92 or 2.044 per/patient), and this is believed to be due to the greater remaining excess weight. CONCLUSION: Reduction of body weight by VBG is associated with resolution or improvement of a significant number of the obesity-associated disorders. However, super obese patients remain obese after surgery, and this results in two-fold higher remaining morbidity.

Continuous spinal anesthesia/analgesia for perioperative management of morbidly obese patients undergoing laparotomy for gastroplastic surgery.

BACKGROUND: The authors determined prospectively the safety of continuous spinal anesthesia combined with general anesthesia and the efficacy of postoperative pain relief with continuous spinal analgesia for morbidly obese patients undergoing vertical banded gastroplasty. METHODS: 27 patients (13 men, 14 women) with a mean body mass index (BMI) of 50.4 +/- 7.8 and several co-morbidities were studied. All patients were anesthetized with the same anesthetic regimen, which included midazolam, fentanyl, propofol, muscle relaxants, nitrous oxide, isoflurane and intrathecal bupivacaine. Postoperative pain relief was provided for 5 days and all patients received the same regimen, which included intrathecal bupivacaine, fentanyl and intravenous tenoxicam. The intrathecal analgesic regimen was administered continuously through a pump which had the facility of providing bolus doses when requested in predetermined lockout intervals. Intra-operative monitoring included hemodynamic and respiratory parameters. Additional postoperative monitoring included respiratory rate, degree of sedation, sensory level of anesthesia, motor response and intensity of pain. RESULTS: Intraoperative anesthetic technique was safe and provided satisfactory results in the immediate postoperative period. Furthermore, the postoperative analgesia regimen provided effective analgesia in all patients. The mean doses of fentanyl and bupivacaine infused intrathecally for the first 24 postoperative hours were 14.1 +/- 2.0 microg.h(1) and 0.7 +/- 0.1 mg.h(1) respectively, while the requirements of analgesia decreased progressively with time. The technique provided effective analgesia with low pain scores, which was reflected by ease in mobilizing and performing physical exercises with the physiotherapist. Only minor complications related to anesthesia and analgesia were encountered. CONCLUSION: To our knowledge, this technique of anesthesia and postoperative analgesia has not been described before in morbidly obese patients. This regimen merits further controlled trials to establish its place in the perioperative management of morbidly obese patients.

Continuous spinal anaesthesia/analgesia for the perioperative management of high-risk patients.

The intraoperative effects of continuous spinal anaesthesia, and the efficacy of postoperative continuous spinal analgesia in 48 elderly high risk patients undergoing major abdominal, vascular or orthopaedic surgery is reported. Intraoperative anaesthetic technique proved to be safe and provided satisfactory results in the immediate postoperative period. Furthermore, the postoperative analgesic regimen which involved intrathecal fentanyl and bupivacaine, and intravenous tenoxicam, provided effective analgesia for all patients. The intrathecal analgesic regimen was administered continuously through a PCA pump which had the facility to provide bolus doses when requested in predetermined lockout intervals. The mean doses of fentanyl and bupivacaine infused intrathecally for the first 24 h postoperatively were 14.5 +/- 1.5 microg h(-1) (mean +/- SD) and 0.72 +/- 0.08 mg h(-1) (mean +/- SD), respectively, while the requirements for analgesia decreased progressively overtime but lasted for 118 h. The technique provided effective analgesia with low pain scores that was reflected by the ease in performing physical exercises and the pleasant co-operation with the physiotherapist. Only minor complications related to anaesthesia/analgesia were encountered.

Monitoring the successful embolization of an arterio-venous fistula by a fibreoptic jugular vein catheter.

The management of surgical embolization of a post-traumatic carotid-cavernous fistula is reported in this study. The procedure was successfully performed with the aid of a fibreoptic intravascular catheter, which was monitoring continuously the changes of the jugular venous oxygen saturation. Jugular venous oxygen saturation monitoring effectively confirmed the success of embolization without the need for intraoperative angiography, by manifesting an abrupt return of oxygen saturation from arterial to normal venous values immediately after embolization.

Peritoneal expansion by artificially produced ascites during perfusion chemotherapy.

HYPOTHESIS: In cases of peritoneal carcinomatosis, continuous hyperthermic peritoneal perfusion chemotherapy (CHPPC) accomplishes homogeneous distribution of the drug and heat to the entire peritoneal cavity and exposure of the visceral and parietal surfaces to the perfusate. A new closed technique for expansion that produces artificial ascites is safer for medical personnel because of less heat and drug loss and more efficacious in its hemodynamic effect on the patient. DESIGN: Prospective study. SETTING: University hospital. PATIENTS: Twenty-one patients with peritoneal carcinomatosis. INTERVENTIONS: We performed 23 continuous hyperthermic peritoneal perfusion chemotherapy (CHPPC) procedures with peritoneal cavity expansion to an intra-abdominal pressure up to 26 mm Hg, using artificially produced ascites with 4 to 9 L normal saline solution. MAIN OUTCOME MEASURES: Intraoperative and postoperative complications and hemodynamic changes during CHPPC. RESULTS: No intraoperative complications were recorded. The artificially produced ascites did not cause significant hemodynamic changes. During the immediate postoperative period, 1 patient died of intra-abdominal hemorrhage and leakage of a colorectal anastomosis, resulting in a mortality rate of 4% in our series. Minor complications were seen in 14 patients. The complications were not attributable to the expansion technique. CONCLUSIONS: Our proposed modification of closed-circuit CHPPC appears to be well tolerated and safe in patients with a high tumor load, as well as for the theater personnel. It remains to be investigated whether the theoretical advantages of the proposed technique will also lead to better long-term results.

Idiopathic prolonged QT interval and QT dispersion: the effects of propofol during implantation of cardioverter-defibrillator.

Local anaesthesia combined with conscious sedation is becoming a popular technique for implantation of cardioverter-defibrillator devices. Propofol was given to provide loss of consciousness during defibrillation shock administration, for induced ventricular fibrillation testing. Propofol was found to decrease QT interval and QT dispersion in two patients with idiopathic prolonged QT interval and QT dispersion. The findings of the procedure are reported.

Undiagnosed central anticholinergic syndrome may lead to dangerous complications.

This report describes two cases of central anticholinergic syndrome, the first after general anaesthesia and the other during a prolonged stay in the intensive care unit. The symptoms in both patients resolved soon after physostigmine administration. There was a delay in the diagnosis of central anticholinergic syndrome, which resulted in acute lung injury and unanticipated intensive care unit admission. It is suggested that in cases of abnormal mental recovery after anaesthesia or sedation, the diagnosis of central anticholinergic syndrome should be considered.

Continuous spinal anaesthesia/analgesia for abdominal aortic aneurysm repair and post-operative pain management.

The intra-operative management of two patients with chronic obstructive pulmonary disease and cardiovascular pathology, who underwent peripheral reconstructive vascular surgery under continuous spinal anaesthesia, is described. Furthermore, continuous intrathecal analgesia was also continued in the post-operative period and provided effective pain relief that was reflected by the favourable surgical outcome.

Disorders associated with clinically severe obesity: significant improvement after surgical weight reduction.

BACKGROUND: Surgical treatment for patients with clinically severe obesity mainly aims to reduce morbidity. METHODS: Sixty-two patients were examined for disorders associated with morbid obesity before and after surgical weight reduction by vertical banded gastroplasty. All patients were followed-up for 12 to 48 months. RESULTS: At the end of the first postoperative year, 84% of the patients had lost at least 50% of their excess weight. Of the 218 weight-related pathologic conditions existing before the operation, 131 (60%) were completely cured, 50 (23%) showed significant improvement, and only 37 (17%) remained unchanged. The same percentages were obtained for patients followed tip for 24, 36, and 48 postoperative months. CONCLUSIONS: Surgical treatment of clinically severe obesity has a significant effect on the health of the patients by eliminating the associated disorders.

Anaesthesia and the QT interval. Effects of isoflurane and halothane in unpremedicated children.

The effects of isoflurane and halothane on the QT interval were investigated during induction of anaesthesia. Fifty-one unpremedicated, ASA grade 1 children were studied. Anaesthesia was induced with either isoflurane (n = 25) or halothane (n = 26) and was maintained to the end of the study with end-tidal concentrations of between 2.5% and 3%. Recording of the electrocardiograph, heart rate and systolic arterial pressure were obtained at the following times: before induction of anaesthesia; 1 min and 3 min after stable end-tidal concentrations of anaesthetic agent had been reached; 1 min and 3 min following vecuronium administration; at the time of tracheal intubation and 1 min and 3 min later. Isoflurane significantly prolonged the QT interval (p < 0.001), in contrast to halothane which shortened it (p < 0.01). Heart rate remained largely unchanged during isoflurane anaesthesia but it decreased in the presence of halothane (p < 0.001). In both groups, systolic arterial pressure decreased significantly after induction of anaesthesia (p < 0.001) and remained so to the end of the study. In the isoflurane group, 12 children developed ECG repolarisation abnormalities and in one child an arrhythmia was noticed. In the halothane group, one child developed repolarisation changes while arrhythmias were observed in 10 children. There were no adverse sequelae. It is concluded that halothane may be a better anaesthetic agent than isoflurane for use in children with a prolonged QT interval.

The influence of premedication on heart rate variability.

Analysis of heart rate variability has been used to study the effects of midazolam, morphine and clonidine on the autonomic nervous system, when administered to patients for premedication. Ninety-five patients were studied 60 min before and 60 min after premedication. Normal saline (n = 25), midazolam 0.08 mg.kg-1 (n = 24), morphine 0.15 mg.kg-1 (n = 23), or clonidine 2 micrograms.kg-1 (n = 23) were administered intramuscularly by random allocation. A Holter device was connected to the patient during the study period. Using power spectral analysis the low-frequency and high-frequency components were calculated from the Holter recordings. These are markers for sympathetic and parasympathetic activity respectively; the low- to high-frequency ratio was also calculated, a ratio of > 1 signifying sympathetic dominance. A significant reduction was noticed in both low-frequency and high-frequency power in the three premedicated groups, whereas no changes were observed in the normal saline group. In the case of midazolam, both the low and high frequencies were decreased but the low- to high-frequency ratio did not change significantly. Morphine and clonidine depressed the low-frequency component more than the high-frequency component and the low- to high-frequency ratio was decreased, suggesting parasympathetic dominance. We conclude that heart rate variability may be a useful tool for investigating the effect of drugs on the autonomic nervous system.

Anaesthesia and the QT interval in humans: effects of halothane and isoflurane in premedicated children.

The effects of halothane and isoflurane followed by subsequent administration of vecuronium on the QT interval have been investigated during the induction of anaesthesia. Fifty-eight children, ASA I, without cardiovascular and electrolyte abnormalities and not receiving any medication were studied. Anaesthesia was induced with either halothane (n = 28) or isoflurane (n = 30), and was maintained until the end of the study with end-tidal concentrations of 2.5-3%. Recordings of ECG, heart rate and systolic arterial pressure were obtained at the following times: prior to induction of anaesthesia; 1 and 3 min after stable end-tidal concentrations of the induction agent had been reached; 1 and 3 min following vecuronium administration; at the time of tracheal intubation; 1 and 3 min later. Halothane significantly shortened the QTc interval (P < 0.05); isoflurane prolonged it (P < 0.001). Heart rate decreased significantly after halothane administration (P < 0.01); in contrast, heart rate increased after induction of anaesthesia with isoflurane (P < 0.05), increasing further after laryngoscopy and tracheal intubation (P < 0.001). Systolic arterial pressure decreased significantly (P < 0.001) in both groups after induction of anaesthesia and remained decreased until the end of the study. It is concluded that halothane may be a better choice than isoflurane for children with a long QT interval.

Hemodynamic effects of intravenous somatostatin administered in the postoperative period.

OBJECTIVE: To evaluate the hemodynamic effects of intravenous somatostatin administration in patients during the early postoperative period. DESIGN: Prospective, case-controlled trial. SETTING: Postanesthesia care unit. PATIENTS: Ten postoperative, noncirrhotic, American Society of Anesthesiologists physical status II patients, after resection of nonsecretory (i.e., non-neuroendocrine) tumors. No patient received any vasoactive medication perioperatively. INTERVENTIONS: Three hours after the end of surgery, normal saline or somatostatin was intravenously administered in two phases: a) in phase 1, patients received a 20-mL bolus of normal saline within 1 min, followed by a continuous infusion of 20 mL of normal saline for the next 30 mins. Patients were left undisturbed for the subsequent 30 mins. b) in phase 2, patients received somatostatin (3.5 micrograms/kg, 20-mL bolus) over 1 min, followed by a continuous infusion of somatostatin (3.5 micrograms/kg/hr) for 72 hrs. MEASUREMENTS AND MAIN RESULTS: Anesthesia was managed according to a prospectively designed protocol. Patients' hemodynamic profiles and pressure waveforms were recorded immediately before the bolus injections of normal saline and somatostatin, and at every minute thereafter for 30 mins. Bolus doses of somatostatin produced a transient, nonsignificant decrease in heart rate, along with short-lived increases in systolic arterial pressure, diastolic arterial pressure, systolic pulmonary arterial pressure, diastolic pulmonary arterial pressure, and central venous pressure. CONCLUSION: Bolus intravenous somatostatin administered postoperatively after tumor resection in patients produced transient cardiovascular changes that were not sustained during a subsequent continuous infusion.

Long QT interval syndrome with increased QT dispersion.

This case report describes the anaesthetic management of a patient with sporadic-type long QT interval syndrome (LQTS), and increased QT dispersion, who presented for removal of an ovarian cyst. Beta adrenergic blockade and adequate depth of anaesthesia for successful management is emphasized. The successful use of epidural administration of lignocaine and opioids in addition to general anaesthesia is described.