Time-varying spectral analysis revealing differential effects of sevoflurane anaesthesia: non-rhythmic-to-rhythmic ratio.

BACKGROUND: Heart rate variability (HRV) may reflect various physiological dynamics. In particular, variation of R-R peak interval (RRI) of electrocardiography appears regularly oscillatory in deeper levels of anaesthesia and less regular in lighter levels of anaesthesia. We proposed a new index, non-rhythmic-to-rhythmic ratio (NRR), to quantify this feature and investigated its potential to estimate depth of anaesthesia. METHODS: Thirty-one female patients were enrolled in this prospective study. The oscillatory pattern transition of RRI was visualised by the time-varying power spectrum and quantified by NRR. The prediction of anaesthetic events, including skin incision, first reaction of motor movement during emergence period, loss of consciousness (LOC) and return of consciousness (ROC) by NRR were evaluated by serial prediction probability (PK ) analysis; the ability to predict the decrease of effect-site sevoflurane concentration was also evaluated. The results were compared with Bispectral Index (BIS). RESULTS: NRR well-predicted first reaction (PK > 0.90) 30 s ahead, earlier than BIS and significantly better than HRV indices. NRR well-correlated with sevoflurane concentration, although its correlation was inferior to BIS, while HRV indices had no such correlation. BIS indicated LOC and ROC best. CONCLUSIONS: Our findings suggest that NRR provides complementary information to BIS regarding the differential effects of anaesthetics on the brain, especially the subcortical motor activity.

Heavily T2-weighted MR myelography vs CT myelography in spontaneous intracranial hypotension.

OBJECTIVE: To assess the diagnostic accuracy of heavily T2-weighted magnetic resonance myelography (MRM) in patients with spontaneous intracranial hypotension (SIH). METHODS: Patients with SIH were recruited prospectively, and first underwent MRM and then computed tomographic myelography (CTM). The results of MRM were validated with the gold standard, CTM, focusing on 1) CSF leaks along the nerve roots, 2) epidural CSF collections, and 3) high-cervical (C1-3) retrospinal CSF collections. Comparisons of these 3 findings between the 2 studies were made by kappa statistics and agreement rates. Targeted epidural blood patches (EBPs) were placed at the levels of CSF leaks if supportive treatment failed. RESULTS: Nineteen patients (6 men and 13 women, mean age 37.9 +/- 8.6 years) with SIH completed the study. MRM did not differ from CTM in the detection rates of CSF leaks along the nerve roots (84% vs 74%, p = 0.23), high-cervical retrospinal CSF collections (32% vs 16%, p = 0.13), and epidural CSF collections (89% vs 79%, p = 0.20). MRM demonstrated more spinal levels of CSF leaks (2.2 +/- 1.7 vs 1.5 +/- 1.5, p = 0.011) and epidural collections (12.2 +/- 5.9 vs 7.1 +/- 5.8, p < 0.001) than CTM. The overall level-by-level concordance was substantial for CSF leaks along the nerve roots (C1-L3) (kappa = 0.71, p < 0.001, agreement = 95%) and high-cervical retrospinal CSF collections (C1-3) (kappa = 0.73, p < 0.001, agreement = 92%), and moderate for epidural CSF collections (C1-L3) (kappa = 0.47, p < 0.001, agreement = 72%). Ten of the 14 patients (71%) receiving targeted EBPs experienced sustained symptomatic relief after a single attempt. CONCLUSIONS: Heavily T2-weighted magnetic resonance myelography was accurate in localizing CSF leaks for patients with spontaneous intracranial hypotension. This noninvasive technique may be an alternative to computed tomographic myelography before targeted epidural blood patches.

The effect of heart rate variability on request for labour epidural analgesia.

Maternal heart rate variability of 62 parturients were compared based on their choice of using (epidural group, 44 women) or not using (control, 18 women) epidural analgesia. Baseline heart rate variability and visual analogue scores were recorded when the cervix of the parturient dilated to 2-4 cm, and paired data were collected 1 h later. We found that parturients in the epidural group had greater heart rate variability at the beginning of labour. Multiple logistic regression analysis identified percentage of absolute difference in successive RR intervals exceeding 20 ms as the best indicator of choosing epidural analgesia. Almost all heart rate variability measures were unchanged 1 h later in both groups. We concluded that parturients who chose epidural analgesia had greater heart rate variability, and that percentage of absolute difference in successive RR intervals exceeding 20 ms could reflect their likelihood of requesting epidural analgesia at the beginning of labour.

The timing of MRI determines the presence or absence of diffuse pachymeningeal enhancement in patients with spontaneous intracranial hypotension.

The timing and clinical relevance of diffuse pachymeningeal enhancement (DPE) in the magnetic resonance imaging (MRI) examination of patients with spontaneous intracranial hypotension (SIH) remain undetermined. We reviewed 53 consecutive SIH patients (30 F/23 M, mean age of onset 41.7 +/- 11.3 years) in a tertiary hospital. Thirteen (24.5%) patients did not have DPE on their initial cranial MRIs. They had significantly shorter latency between the time of MRI examinations and the time of headache onset compared with those with DPE (6.5 +/- 4.4 vs. 20.4 +/- 16.3 days, t-test, P < 0.001). Eight of these 13 patients received a follow-up MRI (mean duration 30.3 +/- 16.6 days, range 6-59 days) and six of them revealed DPE. Among patients with DPE, the enhancement disappeared as early as 25 days after headache onset. The outcome did not differ between patients with and without DPE. The presence of DPE was associated with the timing of the MRI examination.

Oral clonidine premedication preserves heart rate variability for patients undergoing larparoscopic cholecystectomy.

BACKGROUND: Clonidine has been shown to reduce perioperative circulatory instability. This postoperative analgesic effect of clonidine was also known in previous studies. The aim of the study was to investigate the clinical efficiency of oral clonidine premedication in anesthesia and analgesia in patients undergoing laparoscopic cholecystectomy. METHODS: Thirty-two patients scheduled for elective laparoscopic cholecystectomy were recruited for a prospective, randomized, double-blinded comparative study. They were allotted randomly to two groups: placebo or clonidine. Patients in the placebo group (n = 16) were premedicated with oral antacid (alugel hydroxide 300 mg), while those in the clonidine group (n = 16) were premedicated with oral clonidine 150 micro g before anesthesia. Analysis of heart rate variability was used to quantify the control of heart rate at baseline, and during the pneumoperitoneum and recovery periods. Time of the first request for postoperative analgesic and cumulative analgesic requirements in 24 h were recorded. Data are expressed as mean +/- SD. RESULTS: Heart rate variability was reduced in the pneumoperitoneum and postoperative period in the placebo group. Clonidine resulted in a greater perioperative (pneumoperitoneum period) power at all frequency ranges compared with placebo (671.5 +/- 470.5 vs. 55.1 +/- 51.6 ms2/Hz for total power variability, 170.1 +/- 94.4 vs. 16.9 +/- 21.1 ms2/Hz for low-frequency variability and 206.1 +/- 95.7 vs. 16.4 +/- 15.1 ms2/Hz for high-frequency variability, P < 0.05). The postoperative analgesic requirement was less (2.3 +/- 0.8 vs. 3.2 +/- 1.2 dose, P < 0.05) in comparison with the placebo group. CONCLUSION: Clonidine preserves heart rate control in pneumoperitoneum and recovery periods. Oral clonidine premedication also reduces the requirement for postoperative analgesia.

Anesthetic management of parturients with Eisenmenger's syndrome--report of two cases.

Pregnancy is badly tolerated in patients with Eisenmenger's syndrome; maternal mortality with coherent fetal morbidity is high. Even with the advancement of both obstetric and anesthetic managements, the maternal mortality still exceeds 25%. Once conception occurs in patients of Eisenmenger's syndrome with severe pulmonary hypertension, interruption of pregnancy is still the best manipulation to be recommended. We report two cases of parturients with Eisenmenger's syndrome, who underwent termination of pregnancy. In this report, the obstetric and anesthetic management of this kind of parturients with Eisenmenger's syndrome has been thoroughly discussed.

Abdominal vascular injury during lumbar disc surgery.

Major vascular injury is an unusual but well-recognized complication of vertebral disc surgery. Isolated arterial laceration is the most common type of this vessel injury in lumbar spine surgery, with early manifestation due to retroperitoneal hemorrhage. Two cases are described that illustrate the full spectrum of acute manifestation of such injuries. Two cases of acute hemorrhage due to arterial trauma were seen; one mortality case was recognized during the operation and one salvaged in the recovery room. In both cases unstable perioperative hemodynamics and postoperative distended abdomen were observed. It is the purpose of this paper to report two cases and to discuss the morbid anatomy, diagnosis of such vascular injuries and anesthetic handling of retroperitoneal hemorrhage. For anesthesiologists who are also drill workers while doing lumbar spinal or epidural anesthesia, these rare catastrophes remind us to pay special attention to the vertebral vascular (not only skeletal) anatomy.

Anesthetic managements of the patients with giant mediastinal tumors--a report of two cases.

Anesthesia for patients with a huge anterior mediastinal tumor is a well-known challenge and trial to all the anesthesiologists. The tumor mass which directly compresses the trachea and bronchus induces hypoxia and asphyxia, eventuating in cardiac arrest or even fatality in the process of general anesthesia. In selection of anesthetic technique, general anesthesia is deliberately avoided if not mandatory or spontaneous respiration should be strictly preserved by all means if obligatory. Our surgical colleagues are usually not so familiar with this potentially life-threatening situation as are the anesthesiologists, and bad communications and interactions between the two may court disaster. Here we reported 2 cases: the former was an immediate mortality in a youth with a giant anterior mediastinal tumor undergoing excisional biopsy of a neck mass under general anesthesia, and the latter was a successful anesthetic management in a woman with a giant mediastinal tumor receiving abdominal total hysterectomy for cervical cancer in situ under spinal anesthesia. The hazards of general anesthesia in these patients and the importance of comprehending preanesthetic preparations were reviewed and discussed. Moreover, we address that whenever one has shot his bolt still futile to improve the respiratory crisis in a case with mediastinal tumor, try to ventilate the patient in a prone position as it has clinical importance in ventilation and oxygenation.

Heart rate variability in neonatal rats after perinatal cocaine exposure.

Pregnant rats received saline once daily (Control QD) or twice daily (Control BID), cocaine 2 mg/kg IV daily (COC QD) or twice daily (COC BID) throughout gestation beginning on gestational day 4. The treatment was continued in nursing mothers until postnatal day 7. All studies were performed in their offsprings on postnatal days 1 and 7. An age-dependent increase in heart rate was observed from D1 to D7 in all four groups of animals. Cocaine exposure significantly increased heart rate in the once daily treatment group on D1 and D7. In contrast, twice daily cocaine exposure did not alter heart rate. Maturational changes in heart rate variability (HRV) were also documented. Low-frequency (LF: 0.25-0.8 Hz) power of HRV is a marker of both sympathetic and parasympathetic influences. and high-frequency (HF: 0.8-2.4 Hz) power is a marker of efferent vagal activity. Total power (TP) is the sum of LF and HF. TP, normalized units of LF (LF as percent of TP), and normalized HF power decreased from D1 to D7 in all groups. Cocaine treatment affected both LF and HF powers and there was an interaction between cocaine treatment and age for both LF and HF. Although LF/HF ratio decreased from D1 to D7 in both groups of control animals. LF/HF did not change from D1 to D7 in either cocaine-treated group. Thus, cocaine exposure significantly attenuated the age-dependent change in LF/HF. Our results indicated that there were normal developmental changes in HRV consistent with continued postnatal development of autonomic nervous system. Perinatal cocaine exposure appeared to modify these changes. The specific autonomic mechanism for the cocaine effect may be a decline in parasympathetic activity and a concomitant change in sympathetic activity.

Diminished vasomotor component of systemic arterial pressure signals and baroreflex in brain death.

We compared the cardiovascular autonomic regulatory mechanisms between patients with brain death or under a persistent vegetative state and healthy volunteers, based on auto- and cross-spectral analysis of systolic blood pressure (SBP) and interpulse interval (PPI) signals. Brain-dead patients exhibited a significant reduction in the absolute and relative power of the low-frequency (LF; 0.04-0.15 Hz) component in both SBP and PPI spectra, along with appreciable decrease in the very low frequency (VLF; 0.004-0.04 Hz), LF, and high-frequency (HF; 0.15-0.4 Hz) power of the PPI signals. Patients in a persistent vegetative state exhibited a power of the VLF and LF component in the SBP spectrum that was comparable to that in healthy subjects, although a discernible reduction in the VLF, LF, and HF power of the PPI spectrum was manifested by the former group. Assessments with the magnitude of SBP-PPI transfer function and linear regression analysis of beat-to-beat fluctuations in SBP and PPI revealed a progressive decline in spontaneous baroreflex sensitivity from healthy subjects to patients in a persistent vegetative state or with brain death. We conclude that the vasomotor component of systemic arterial pressure signals and spontaneous baroreflex are highly correlated with the functional integrity of the brain stem.

EMLA cream and lidocaine local injection in the treatment of extravenous thiopental injection--a case report.

Thiopental extravasation which would cause tissue edema and necrosis in rapid progression by chemical reaction and vascular spasm is a potentially serious complication in anesthesia. Early diagnosis and treatment may bear a favorable outcome. A patient who sustained thiopental extravasation and received local injection of lidocaine and local application of EMLA (Eutectic Mixture of Local Anesthetics) for treatment with excellent results is presented hereunder.

Spectral analysis of systemic arterial pressure and heart rate signals as a prognostic tool for the prediction of patient outcome in the intensive care unit.

OBJECTIVES: To evaluate the applicability of changes in spectra of systemic arterial pressure and heart rate signals in the prediction of patient outcome in an adult intensive care unit (ICU). To compare the prognostic predictability of this method with the Acute Physiology and Chronic Health Evaluation II (APACHE II) scoring system. DESIGN: Prospective data collection from 52 ICU patients. SETTING: Adult ICU at a large, university-affiliated, medical center. PATIENTS: Consecutive patients who were admitted to the adult ICU due to noncardiac emergencies, and who remained for at least 2 days. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: The demographic data, diagnosis, and survival data were recorded for each patient enrolled in this study. For the period between admission and 24 hrs before discharge, the APACHE II score was tabulated daily. Likewise, continuous, on-line, and real-time spectral analysis of systemic arterial pressure and heart rate signals was carried out every day for at least 30 mins at 2200 to 2400 hrs. The averaged power density values during this 30-min recording period of the high-frequency (0.15 to 0.4 Hz), low-frequency (0.08 to 0.15 Hz), and very low-frequency (0.016 to 0.08 Hz) components of systemic arterial pressure and heart rate signals were subsequently computed. Systemic vascular resistance index and cardiac index were also determined daily. We observed a trend of changes in the spectral components of systemic arterial pressure and heart rate signals in patients who eventually survived (n = 25) or died (n = 27). Progressive increases in the power density values of both the low-frequency and very low-frequency components of systemic arterial pressure and heart rate signals appeared to be related to recovery. Conversely, progressive decreases in the power density values of these spectral components was indicative of deterioration and fatality. The predicted outcome based on the trend of changes in the low-frequency and very low-frequency components of systemic arterial pressure and heart rate signals correlated positively with daily APACHE II scores. No direct correlation, however, was indicated by mean systemic arterial pressure, heart rate, systemic vascular resistance index, and cardiac index. We also confirmed that the differential trend of spectral changes in patients who survived or died was not due to circadian rhythm, nor alterations in the responsiveness of the blood vessels to intravenous infusion of dopamine. CONCLUSION: Power spectral analysis of systemic arterial pressure and heart rate signals offers a reasonable means of monitoring acute, critically ill patients, and may be used as an alternative prognostic tool for the prediction of patient outcome in the ICU.

Exposure of anesthesiologists to nitrous oxide during pediatric anesthesia.

Nitrous oxide (N2O) is one of the most common inhalation anesthetics in current anesthesiological practice. Even though artificial ventilation and active scavenging in operating theaters are employed in most of the modern hospitals, potential N2O contamination persists in regular anesthesia, particularly pediatric operation. In order to understand personal exposure during pediatric anesthesia, ambient monitoring for N2O exposure around the breathing zone of the anesthesiologist was conducted by a portable infra-red Miran 1B2 spectrophotometer. The results demonstrated that general mask anesthesia generated greatest N2O contamination, with the mean time-weighted-average (TWA) concentrations of 85 +/- 48.4 (mean +/- S.D.) ppm in 12 cases. Initial mask induction followed by cuffed endotracheal incubation (6 cases) or intravenous induction followed by uncuffed endotracheal intubation (6 cases) also produced significant pollution to the workers, with the mean TWAs of 33.2 +/- 24.0 ppm and 31.9 +/- 18.0 ppm respectively. These procedures provided exposure levels above the 25 ppm Recommended Exposure Limit (REL) of the National Institute of Occupational Safety and Health (NIOSH), U.S.A. Modification with intravenous induction followed with cuffed endotracheal intubation or mask general anesthesia provided with a ventilation hood diminished the contamination apparently, with the resulting mean TWAs of 11.0 +/- 4.7 ppm and 17.9 +/- 9.8 ppm in 7 and 5 cases respectively. The results indicated that excessive N2O exposure to anesthesiologists was not negligible during routine pediatric anesthesia. Significant reduction could be achieved via appropriate industrial modification.

Anesthetic management in a parturient with progressive systemic sclerosis during cesarean section--a case report.

This case report concerns a successful Cesarean section (C/S) delivery in an expectant woman affected with progressive systemic sclerosis (PSS) with clinical manifestations of severe pulmonary hypertension (PH), cor pulmonale, severely restrictive ventilatory impairment, pregnancy-induced hypertension (PIH), and esophageal dysfunction under general anesthesia (GA). This is an extremely rare condition in obstetrics and the victim is usually in a great peril of conception, delivery, surgery and anesthesia because of poor pulmonary and cardiac reserves. We herewith reported our experience in two GAs given uniquely to the same patient who was affected with the disorder and discuss the problem.

Anesthetic management in parturients with uterine rupture preoperatively--report of two cases.

Uterine rupture is a rare obstetric emergency, and the diagnosis of rupture is not always obvious. High surgical delivery rate today which tends to increase the incidence of the disaster urged us to present this report. Two cases of spontaneous rupture of uterus are described. Case 1 concerns spontaneous rupture of a previously intact uterus; case 2 is a rupture due to placenta percreta. A review relevant to its incidence, risk factors, clinical characteristics, and anesthetic managements is given.

Effect of P-6 acupressure on prevention of nausea and vomiting after epidural morphine for post-cesarean section pain relief.

BACKGROUND: Nausea and vomiting are important side effects following administration of epidural morphine for post-Cesarean section pain relief. Stimulation of the P-6 (Neiguan) acupoint is a traditional Chinese acupuncture modality used for antiemetic purpose; it has been found to be effective. The aim of this study was to evaluate the antiemetic effect of P-6 acupressure in parturients given epidural morphine for post-Cesarean section pain relief. METHOD: In a randomized, double-blind and controlled trial, sixty parturients receiving epidural morphine for post-Cesarean section pain relief were investigated. Parturients were allocated to receive the acupressure bands or placebo bands on the P-6 acupoint bilaterally before the administration of spinal anesthesia and were observed over a 48-hour study period. RESULTS: The incidence of nausea and vomiting was significantly decreased from 43% and 27% in the control group, to 3% and 0% in the acupressure group, respectively (P < 0.05). CONCLUSION: The results demonstrate that prophylactic use of acupressure bands bilaterally on the P-6 acupoint can significantly reduce incidence of nausea and vomiting after epidural morphine for post-Cesarean section pain relief.

Evaluation of the hemostatic clot formation of newborns by Sonoclot coagulation analyzer.

BACKGROUND: Sonoclot Analyzer has been widely used for more than five years in The United States to evaluate the platelet function and coagulation in adult. No clinical trial with the Analyzer has been reported in the field of pediatrics. The present study was aimed to evaluate the efficacy of the Sonoclot Analyzer for urgent determination of platelet function and coagulation in newborns. METHODS: Venous blood samples were drawn from the umbilical vein in 70 healthy newborns, and from the median cubital vein in 70 healthy adult volunteers, between 24 to 40 years of age, for control. DP2951 Sonoclot II Surgical Analyzer with graphic printer was used to evaluate the hemostatic clot formation. RESULTS: Results demonstrated that Sono ACT (activated coagulation time), peak time and retraction time increased by 36%, 66% and 70% respectively in newborns, while clot rate decreased by 69% in comparison with that of these adults. CONCLUSIONS: The results of using the Sonoclot Analyzer in this study confirmed other previous investigation that platelet function and coagulation are altered in newborns when compared with that of adults. The Sonoclot Analyzer is a simple device, easy to perform; It requires only small amounts of blood sampled (0.4 ml), and provides a rapid coagulation function for newborns.

The physiological effect of CO2 pneumoperitoneum in pediatric laparoscopy.

BACKGROUND: The physiological effect of CO2 pneumoperitoneum during laparoscopy is a great concern of the anesthesiologists. Its effect in pediatric laparoscopy has not been previously reported. The purpose of this study was to examine the physiological alteration of pediatric patients during CO2 pneumoperitoneum. METHODS: One hundred and twenty six children aged from 11 mon to 13 yr undergoing laparoscopic inguinal exploration were divided into three groups based on age orientation: group I comprising 40 children with age from 11 mon to 2 yr; group II 46 children with age between 2 to 5 yr; and group III 40 children aged from 5 to 13 yr. All patients received endotracheal anesthesia with halothane-N2O in 50% O2 and atracurium for muscle relaxation. Respiration was controlled by an Ohmeda 7000 ventilator with constant minute ventilation to maintain baseline end-tidal CO2 tension (PETCO2) between 32-33 mmHg. After anesthesia, CO2 was insufflated into the peritoneal cavity via the opened hernia sac. The intraabdominal pressure exerted by CO2 was 10 mmHg and the duration of pneumoperitoneum and laparoscopy was 15 min. We recorded airway pressure, PETCO2, body temperature, blood pressure, heart rate, heart rhythm, and oxygen saturation simultaneously at 1 min interval before, during, and after laparoscopy. RESULTS: The airway pressure and PETCO2 showed significant increases during laparoscopy (15-18% and 18-20% respectively) in all cases, but the percentage of increases were not significantly different among groups. However, the PETCO2 change in terms of time lag were different between groups: (1) the time lag from CO2 insufflation to the emergence of PETCO2 change (latent period) was respectively 0.7 +/- 0.1 (mean +/- SD) min in group I, 0.9 +/- 0.2 min in group II and 1.5 +/- 0.2 min in group III (p < 0.05); (2) the PETCO2 change from baseline to a plateau (ascending period) was respectively 4.2 +/- 0.6 min in group I, 6.3 +/- 1.0 min in group II and 9.1 +/- 1.1 min in group III (p < 0.05); (3) the PETCO2 decline from plateau to baseline after CO2 deflation (descending period) was respectively 6.2 +/- 0.5 min in group I, 8.3 +/- 0.8 min in group II and 12.0 +/- 1.3 min in group III (p < 0.05). The body temperature and hemodynamics including blood pressure, heart rate, heart rhythm, oxygen saturation were not significantly changed during laparoscopy in all groups. CONCLUSIONS: The changes of PETCO2 during laparoscopy did not influence the hemodynamic stability in our study. The younger children give a faster reaction time of PETCO2 change after CO2 insufflation than do the older children which may be related to the variation of physiological exhibition at different state of development.

Seizure after reversal of benzodiazepine treatment with flumazenil: a report of two cases.

Two patients developed seizure immediately after flumazenil administration that aimed to reverse the prolonged sedative effect of diazepam. The use of benzodiazepine for sedation in ICU may mask valuable information relevant to an ongoing pathological change. The seizure in our patients seemed most likely to result from septic encephalopathy which was unmasked by flumazenil. However, flumazenil has the potential to provoke seizure and should be used with caution.