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PubMed1992

A neuromuscular monitoring system based on a personal computer.

We have developed a computerized neuromuscular monitoring system (NMMS) using commercially available subsystems, i.e., computer equipment, clinical nerve stimulator, force transducer, and strip-chart recorder. This NMMS was developed for acquisition and analysis of data for research and teaching purposes. Computer analysis of the muscle response to stimulation allows graphic and numeric presentation of the twitch response and calculated ratios. Since the system can store and recall data, research data can be accessed for analysis and graphic presentation. An IBM PC/AT computer is used as the central controller and data processor. The computer controls timing of the nerve stimulator output, initiates data acquisition, and adjusts the paper speed of the strip chart recorder. The data processing functions include establishing control response values (when no neuromuscular blockade is present), displaying force versus time and calculated data graphically and numerically, and storing these data for further analysis. The general purpose nature of the computer and strip chart recording equipment allow modification of the system primarily by changes in software. For example, new patterns of nerve stimulation, such as the posttetanic count, can be programmed into the computer system along with appropriate data display and analysis routines. The NMMS has functioned well in the operating room environment. We have had no episodes of electrocautery interference with the computer functions. The automated features have enhanced the utility of the NMMS.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer Systems↗

PubMed1993

Artifact detection and removal during auditory evoked potential monitoring.

Various artifacts can distort or obscure evoked potential waveforms. The algorithms presented in this paper scan the output electroencephalographic signal for artifacts during evoked potential recordings. If possible, the artifact is removed; if not possible, that sweep is excluded from the averaging process required to raise the evoked response above the background electroencephalographic activity. An artifact is detected if 1 or more amplitude or frequency parameters exceed a threshold. These thresholds have been determined after constructing histograms of the parameters concerned using a number of control evoked potential recordings containing no visually recognizable artifacts. The distributions of the parameters shown by these histograms give information about their normal range. The method improves the quality of the waveform in many cases, but its effectiveness strongly depends on the characteristics of the artifacts concerned.

Algorithms↗

PubMed1995

LabVIEW: a software system for data acquisition, data analysis, and instrument control.

Computer-based data acquisition systems play an important role in clinical monitoring and in the development of new monitoring tools. LabVIEW (National Instruments, Austin, TX) is a data acquisition and programming environment that allows flexible acquisition and processing of analog and digital data. The main feature that distinguishes LabVIEW from other data acquisition programs is its highly modular graphical programming language, "G," and a large library of mathematical and statistical functions. The advantage of graphical programming is that the code is flexible, reusable, and self-documenting. Subroutines can be saved in a library and reused without modification in other programs. This dramatically reduces development time and enables researchers to develop or modify their own programs. LabVIEW uses a large amount of processing power and computer memory, thus requiring a powerful computer. A large-screen monitor is desirable when developing larger applications. LabVIEW is excellently suited for testing new monitoring paradigms, analysis algorithms, or user interfaces. The typical LabVIEW user is the researcher who wants to develop a new monitoring technique, a set of new (derived) variables by integrating signals from several existing patient monitors, closed-loop control of a physiological variable, or a physiological simulator.

Analog-Digital Conversion↗

PubMed1994

Nondepolarizing neuromuscular blockade does not alter sensory evoked potentials.

OBJECTIVE: The objective of this study was to determine whether changes in nondepolarizing neuromuscular blockade (NMB) alter the latency or amplitude of visual, brain stem auditory, or median nerve somatosensory evoked potentials. METHODS: Ten adult cynomologous Macaca fascicularis monkeys were studied during continuous ketamine anesthesia infusion. The NMB was incrementally adjusted between no block and complete block using infusions of vecuronium or atracurium. The NMB was measured by observing the mechanical response of the hand muscles to train-of-four stimulation of the median nerve and by quantification of the peak-to-peak electromyographic activity of the thenar muscles to supramaximal median nerve stimulation. The following variables were measured: the latencies of the three major peaks of the brain stem auditory evoked potential, the latency and amplitude of the cortical visual evoked potential, the latency of the spinal cord response, and the latency and amplitude of the cortical median nerve somatosensory evoked response. RESULTS: No statistically significant changes were observed for any evoked response variable measured at any degree of NMB when compared with values obtained in the unblocked control state. CONCLUSIONS: The results suggest that fluctuating degrees of NMB may contribute little to changes in these evoked potentials during intraoperative monitoring, given the testing parameters used.

Animals↗

PubMed1996

Kaleidoscopes.

Explore the source record for details and available documents.

Humans↗

PubMed1996

The peripheral pulse wave: information overlooked.

although the waveform derived from a peripheral pulse monitor or pulse oximeter may resemble an arterial pressure waveform, it is in fact a visualization of blood volume change in transilluminated tissue caused by passage of blood: an indication of perfusion or blood flow. Most currently available pulse oximeters indicate this flow, but few display it in usable form. Since adequate tissue blood flow is a prerequisite for normal metabolic activity, it is a parameter that should merit a place in standard anesthesia or intensive care monitors. That the peripheral tissue blood flow is not routinely displayed may be in part due to the difficulty in quantifying data obtained: flow is not accurately measured as simply as pressure, even by invasive means. It is in the pattern of the waveform that beat-to-beat changes in stroke volume can be better seen than measured, or in the interaction of ventilation and circulation that tests general circulatory performance. The origin and interpretation of these changes are discussed and illustrated with examples. We indicate how new physiological tests of autonomic function and cardiac preload can be developed using pulse plethysmography. The importance and application of the Valsalva effect on the waveform is emphasized. This effect is particularly applicable for monitoring adequate fluid loading and the action of vasodilator drugs, which are both important in anesthesia. Differences between the arterial pulse pressure wave and tissue flow wave are discussed, as well as the cause of certain artifacts, including the wandering dicrotic notch.

Anesthesia↗

PubMed1996

Intra-arterial blood gas monitoring system: more accurate values can be obtained.

OBJECTIVE: To compare values measured by a continuous intra-arterial blood gas monitoring system with those measured by conventional blood gas analyzer for the assessment of the clinical performance of a new device for measurement of PaO2, PaCO2, and arterial pH. METHODS: Forty-six patients undergoing cardiopulmonary bypass were enrolled in this study. All patients had a continuous intra-arterial sensor (PB 3300) placed into the radial artery through a 20-gauge catheter. A total of 319 arterial blood gas and pH values were obtained for comparison with a conventional blood gas analyzer. The measurements were performed every 12 hrs after the initial in vitro calibration of the sensor for each patient. RESULTS: Measurements were made over a range of 12 to 192 hrs. The overall bias and precision determined by the two methods were 4.5 and 17.1 mmHg for PaO2; 4.5 and 6.2 mmHg for PaCO2; and 0.009 and 0.035 for pH, respectively. For the range of PO2 less than 150 mmHg, the bias and precision improved to 4.2 and 9.5 mmHg. The sensor-derived PCO2 value, PCO2 (IABG), increased significantly more than the conventional blood gas analysis value, PCO2(ABG), even within 72 hrs (2.8 and 4.1 mmHg). The relationship between the two measurements can be described as: PCO2(IABG)/PCO2(ABG) = 1 + 0.0026.t where t is the time period of use (in hours). By correcting the PCO2(IABG) value using this formula, the overall bias and precision of the values measured by two methods decreases to -0.4 and 3.6 mmHg. CONCLUSIONS: The PO2 and pH values derived from an intra-arterial blood gas monitoring system agreed well with the values measured by a conventional blood gas analyzer. However, the PCO2 value must be corrected due to an increase of drift, especially with extended use for more than 72 hours.

Blood Gas Analysis↗

PubMed1996

Superior mesenteric and portal vein thrombosis following laparoscopic-assisted right hemicolectomy. Report of a case.

PURPOSE: This article describes a case of superior mesenteric and portal vein thrombosis following laparoscopic-assisted right hemicolectomy. METHODS: A retrospective case review was performed. RESULTS: Data continue to grow regarding safety and technical feasibility of laparoscopic-assisted colectomy. As this minimally invasive alternative to open colonic resection becomes more popular, it is inevitable that information on benefits and complications associated with it will continue to expand. We report a case of superior mesenteric and portal vein thrombosis following laparoscopic-assisted colon resection. To our knowledge, this represents a complication of laparoscopic colon resection not previously reported in literature. CONCLUSION: Careful patient selection for this procedure is important. Additionally, the incision for extracorporeal resection and anastomosis in laparoscopic-assisted colectomy must be planned appropriately and carefully monitored intraoperatively to avoid potential complication of vascular trauma leading to mesenteric vein thrombosis.

Colectomy↗

PubMed1996

Comparison of four methods of automated recording of physiologic data at one minute intervals.

INTRODUCTION: This study aims to evaluate possible differences between the maximum, minimum, and mean value over each epoch, or the instantaneous value at the end of the interval, when recording physiological data at 1-minute intervals. METHODS: The mean arterial pressure (MAP), heart rate derived from the radial pulse (PULSE), end-tidal CO2 (etCO2), and the arterial O2 saturation by pulse oximeter (SpO2) were measured continuously in 10 patients during general anesthesia. Anesthesia was induced and maintained using the same technique for the first 10 minutes. At 1-minute intervals for each parameter, the maximum, minimum, and mean value (over the preceding minute), as well as the instantaneous value at the end of the recording epoch, were automatically downloaded to an electronic spreadsheet. The differences between the maximum and minimum, the maximum and mean, the mean and minimum, and the instantaneous and mean values were calculated for each patient. RESULTS: We found differences between the maximum and minimum values recorded over each interval, between the maximum and mean values, between the mean and minimum values, and between the mean and instantaneous values recorded at the end of each minute interval for all physiological parameters examined. CONCLUSIONS: From the data presented, we conclude that during the first 10 minutes of a general anesthetic, including anesthesia induction and endotracheal intubation, the values of physiologic parameters derived from different summary indices, namely the maximum, minimum, and mean values over the 1-minute interval or instantaneous at the end of the interval differ from each other. This source of error must be considered when designing systems for computerized recordkeeping of anesthesia charts and when interpreting the data stored in electronic databases.

Blood Gas Analysis↗

PubMed1996

Motor evoked potentials during brain surgery.

In order to obtain a robust method for intraoperative monitoring of motor pathways, different stimulation patterns to elicit muscle motor evoked potentials (MEPs) were studied during neurosurgical procedures in 3 patients. MEPs were recorded by a catheter electrode in the subdural space and/or by needle electrodes in limb muscles. For stimulation single pulses and trains consisting of two to five pulses were used. Muscle MEPs were only obtained after trains of at least 3 stimuli while single/double stimuli were inefficient. Simultaneous subdural recordings showed that single and double stimuli only elicited D-waves, whereas trains of 3 or more stimuli generated I-waves, as well. We propose that train stimulation can overcome the depressive effects of anesthesia on cortical motoneurons.

Brain↗

PubMed1994

Absence of right superior vena cava that was not detected by insertion of a pulmonary arterial catheter via the right internal jugular vein.

Pulmonary arterial catheter (PAC) placement under fluoroscopy is a useful and safe method to diagnose certain congenital cardiac anomalies [1]. However, when a PAC for intraoperative monitoring is placed without the aid of fluoroscopy, it may be inadvertently placed into anomalous veins. The following report presents a case of persistent left superior vena cava (PLSVC) with absence of right superior vena cava, which was not detected by a PAC inserted via the right internal jugular vein.

Aged↗

PubMed1984

The value of nuclear angiography in the preoperative assessment of patients undergoing elective aortic surgery.

Eighteen patients undergoing elective aortic surgery, either for peripheral vascular insufficiency or abdominal aneurysm, were studied preoperatively by nuclear angiography. By this technique the resting ventricular function of each patient was measured. Nuclear angiography is a safe non-invasive technique which has been shown to have excellent correlation with conventional contrast angiography in the assessment of ejection fraction. Throughout the intraoperative period, measurements of the central venous pressure and pulmonary capillary wedge pressure were taken simultaneously at approximately five-minute intervals. An average of 18 data points was established in each case. The correlation between central venous pressure (CVP) and pulmonary capillary wedge pressure (PCWP) was examined. Ten of our patients had preoperative resting ejection fractions less than 55 per cent. In only four of these patients (40 per cent) was correlation between CVP and PCWP judged to be good intraoperatively. Eight of our patients had preoperative ejection fractions greater than 55 per cent. Six of these (75 per cent) showed good correlation between CVP and PCWP intraoperatively. We also assessed our ability to predict by purely clinical means which patients would show poor correlation between CVP and PCWP. Evaluation on purely clinical grounds was as good as the scans at predicting in which patients CVP would not correlate with PCWP and we feel that the routine use of this test would not modify our use of Swan Ganz catheters for intraoperative monitoring in patients undergoing aortic surgery, in the future.

Aorta, Abdominal↗

PubMed2005

Prolonged (more than ten hours) neuromuscular blockade after cardiac surgery: report of two cases.

PURPOSE: We examine two cases of prolonged neuromuscular blockade (NMB) after cardiac surgery. To the best of our knowledge, these are the first reported cases of complete paralysis lasting more than ten hours after surgery. CLINICAL FEATURES: We attribute the extended durations of NMB (more than ten hours) to high doses of NMB drugs in combination with magnesium sulphate and moderate renal failure. Advanced age, hepatic disease, aminoglycoside exposure, hypocalcemia, and possible interaction between rocuronium and pancuronium may have played minor roles. CONCLUSION: We should avoid administering large doses of NMB agents, even in the context of planned postoperative ventilation. If NMB is not monitored intraoperatively in patients who are at risk of prolonged NMB, then train-of-four response should be measured in the intensive care unit. Adequate sedation should be provided until proper recovery of neuromuscular function is documented.

Acute Kidney Injury↗

PubMed2000

Differential lung ventilation and emergency hyperbaric oxygenation for repair of a tracheal tear.

PURPOSE: To report the anaesthetic management of a case of tracheal rupture, using different types of ventilation and additional hyperbaric oxygenation (HBO). CLINICAL FEATURES: An 8 cm postintubation tracheal tear was repaired in a 66-yr-old woman with acute myocardial reinfarction, mediastinal and subcutaneous emphysema, cardiac failure and unrecognized lymphoma. Intraoperative monitoring included dual oximetry: arterial (SaO2) and mixed venous saturations (SvO2). Maintenance of free surgical access and a series of life-threatening events like dislocation of the jet catheter required many ventilation modes. An episode of supraventricular tachycardia was interrupted by cardioversion. Differential lung ventilation with a combination of conventional and high-frequency jet ventilation (HFJV) modes preserved oxygenation (PO2 139.2 mm Hg, PCO2 42.4 mm Hg, FiO2 1.0) until acute tube obstruction and decrease of saturation values (SaO2 58%, SvO2 45%) required emergency HBO: immediate cardiac and respiratory stabilization was provided by double-lung HFJV and apneic oxygenation under hyperbaric conditions at 2.5 atmospheres absolute for 35 min (SaO2 100%). The patient recovered from surgery but died of non-Hodgkin lymphoma. CONCLUSION: The combination of different ventilation modes including HFJV and the additional use of HBO resulted in sufficient oxygenation during tracheal repair.

Aged↗

PubMed1996

[Perioperative physiological and cognitive functions following oral premedication with 3.75 mg midazolam in operations with retrobulbar anesthesia].

UNLABELLED: The number of surgical procedures performed as day surgery has significantly increased in recent years. Therefore, a safe and short postoperative recovery period has become increasingly important. The aim of the present study was to investigate perioperative cognitive and physiological function after oral premedication with low-dose midazolam (3.75 mg), especially during the postoperative period. METHODS: Forty-seven men (age > 69 years, weight 50-90 kg) scheduled for elective cataract surgery under retrobulbar anaesthesia (RBA) were included in the study. The patients were randomly assigned to either group 1 (n = 28), receiving 3.75 mg midazolam p.o. (Dormicum), or group 2 (n = 19), receiving a placebo orally 30 min before RBA. We measured the following parameters: sedation (modified Glasgow coma scale); anxiety (visual analogue scale); numerical and verbal memory (digit span and reproduction of previously presented words); concentration (Revisions test of Stender/Marschner). To identify depression of ventilation, pulse oximetry and nasal end-tidal PCO2 were monitored intraoperatively. RESULTS: After premedication with 3.75 mg midazolam, patients were significantly more sedated (P < 0.01) and systolic blood pressures were significantly reduced (P < 0.05); 30 min after midazolam premedication only concentration was significantly (P < 0.05) decreased. The results of the other cognitive functions did not differ. No differences in cognitive and physiological functions between and groups could be found 2 h after the operation (293 +/- min after premedication). Intraoperatively, there were no significant differences in end-tidal PCO2 and oxygenation between the groups. In both groups anxiety and blood pressure were significantly higher pre- than postoperatively. CONCLUSION: Oral administration of low-dose midazolam (0.049 +/- mg/kg) seems to be appropriate for premedication before ambulatory surgical procedures in elderly patients. In the interest of patient safety, standardised oral premedication with 3.75 mg midazolam may not be sufficient for some of the patients.

Aged↗

PubMed1997

[The effects of aprotinin. Blood loss and coagulation parameters in orthotopic liver transplantation: A clinical-experimental, prospective and randomized double-blind study].

The effect of aprotinin (2,000,000 IU as a bolus +500,000 JU/h until the end of the operation) on transfusion requirements and coagulation parameters in orthotopic liver transplantation (study group: n = 9; placebo group: n = 9) was investigated in a randomised, double-blind study. Coagulation parameters were monitored intraoperatively using a mobile laboratory. In contrast to the published results, no effect on transfusion requirements could be demonstrated. However, aprotinin showed a positive effect on some coagulation parameters in the reperfusion phase. The mechanism appeared to be inhibition of the contact activation of the intrinsic system with less thrombin generation in the study group.

Aprotinin↗

PubMed2005

[Cavernous hemangioma of the parotid gland in adults].

Parotid hemangiomas are rare in adults. Whereas both capillary and cavernous hemangiomas are seen in children, only cavernous hemangiomas have thus far been reported in adults. Clinically, cavernous hemangiomas usually present as slowly growing, soft or firm, movable, painless parotid masses. Severe pain and swelling can occur, however, depending on the size of the hemangioma or in particular in the presence of acute hemorrhage or thrombosis. CT and MRI are the diagnostic tools of choice. Prior to surgery, magnetic resonance angiography or intra-arterial digital subtraction angiography should be performed to investigate the vascular supply of the tumor. Surgical excision is the treatment of choice for small lesions. Large cavernous hemangiomas usually require superficial or total parotidectomy. Especially in the case of extended lesions, the facial nerve may be difficult to identify and should be monitored intraoperatively.

Adult↗

PubMed2002

[Computer-assisted screw osteosynthesis of the posterior pelvic ring. Initial experiences with an image reconstruction based optoelectronic navigation system].

Injuries of the posterior pelvic with combined anterior and posterior instability require the stabilisation of both the anterior and posterior pelvic ring. If the injury only involves the ligamental connections, then a transileosacral osteosynthesis with screws is the minimal invasive and biomechanically suitable method of choice. The difficulty with this approach is the correct placement of the screws. Their position must be monitored intraoperatively in 3 planes (inlet, outlet and lateral viewing). This denotes that conventional methods involve high radiation dosages for the patient and the surgical staff. Having the system readily available and being able to perform updates during the operation, fluoroscopically supported navigation for the treatment of fresh injuries becomes possible. Between October 1999 and December 2000 7 patients with traumatic instability of the posterior pelvic ring were treated by computer assisted percutaneous transileosacral screw osteosynthesis. In each case the osteosynthesis of the ileosacral joint was performed with two cannulated AO 7.3 mm titanium screws. After the operation the screw position was controlled by CT scanning and compared to the data acquired intraoperatively. No patients had infection, and there were no postoperative neurological defects. The postoperative CT scans showed no intraspinal or intraforminal malplacement of the screws. In two cases a slight tangential screwthread penetration through the ventral sacrum was found. Our first experiences with this novel technology are encouraging and clearly demonstrate the advantages of fluoroscopic supported passive navigation systems for the optimal placement of ileosacral screws.

Adolescent↗