Free colorectal cancer cells on the peritoneal surface: correlation with pathologic variables and survival

BACKGROUND

Clinicopathologic staging of colorectal cancer remains the best predictor of survival. Prognostication for an individual with colorectal cancer remains elusive. This study was designed to investigate the incidence of free surface colorectal cancer cells detected by cytology during elective open curative resection, to correlate their presence with particular clinicopathologic variables and determine whether their presence was predictive of cancer-specific survival.

METHODS

Over a six-year period in one institution, all elective colon and intraperitoneal rectal cancer specimens were assessed during primary resection for the presence of free colorectal cancer cells by means of a simple and tested specimen imprint cytology methodology. Clinicopathologic variables were assessed prospectively and blinded to cytology results. All patients were followed up routinely until death and if the patient was not seen within the last six months, information was obtained from the New South Wales Registry of Births, Deaths and Marriages in Australia.

RESULTS

Overall, 26 of 281 (9.25 percent) colorectal cancers had positive cytology for cancer cells on the peritoneal surface of the bowel. Poorly differentiated tumors were significantly associated with positive cytology. Tumor penetration, presence of vascular or neural invasion, mucinous characteristics, lymph node status, and operative procedure performed were not statistically significant predictors of positive cytology. Overall, 43 of the 281 patients (15.3 percent) died during the mean follow-up period of 49.2 months from cancer-related deaths. Of these patients, 8 had positive cytology and 35 had negative cytology results. Cancer-specific survival assessed with the log-rank test was significantly associated with positive cytology in univariate (P = 0.008) and multivariate analysis (P < 0.001).

CONCLUSION

In this study, the presence of free surface colorectal cancer cells has been shown to be predictive of survival and is independent of direct peritoneal invasion and lymph node status. Thus, further assessment of this simple prognostic variable is warranted and selection of patients with positive cytology for possible adjuvant therapies may be beneficial.

Validation of an Adaptive Signal Enhancer in Intraoperative Somatosensory Evoked Potentials Monitoring

The conventional approach of ensemble averaging in intraoperative somatosensory evoked potentials (SEP) monitoring requires more than 500 trials to extract a reliable waveform for neurologic diagnosis. Previous studies showed that an adaptive signal enhancer (ASE) could increase the signal-to-noise ratio of input signals. This study assessed the accuracy and efficiency of the ASE in the extraction of neurologic normal human and abnormal rat SEP. Cortical and subcortical SEP were taken from 16 subjects undergoing scoliosis surgery. SEP extracted by ASE were compared with those obtained with 500-trial averaging in terms of peak latency, amplitude, and waveforms using correlation coefficients. An animal study composed of 18 rats was used to test the ASE in detecting abnormal SEP changes due to spinal cord compression. The results demonstrate the accuracy of ASE by showing very high correlations between ASE-processed SEP and ensemble averaging-processed SEP in waveforms, peak latencies, and amplitudes. The results also show the efficiency of the ASE in extracting SEP waveforms from 50 input trials, which provided waveforms of sufficiently high quality and latency/amplitude measurements equivalent to those obtained in 500 trials of conventional ensemble averaging. Because of its fast extraction ability, adaptive signal enhancement could be an appropriate alternative to conventional ensemble averaging in intraoperative spinal cord monitoring.

Comparison of monitoring techniques for intraoperative cerebral ischemia

OBJECTIVE

To prospectively compare somatosensory evoked potentials, electroencephalography (EEG) and transcranial Doppler ultrasound (TCD) for detection of cerebral ischemia during carotid endarterectomy (CEA).

METHODS

Somatosensory evoked potentials and EEG recordings were attempted in 156 consecutive CEAs and TCD was also attempted in 91 of them. Recordings from all three modalities were obtained for at least 10 minutes before CEA, during CEA and for at least 15 minutes after CEA. Somatosensory evoked potentials peak-to-peak amplitude decrease of >50%, EEG amplitude decrease of >75%, and ipsilateral middle cerebral artery mean blood flow velocity (mean VMCAi) decrease >75% persisting for the entire period of internal carotid artery occlusion were individually considered to be diagnostic of cerebral ischemia. Clinical neurological examination was performed immediately prior to surgery and following recovery from general anaesthesia.

RESULTS

Somatosensory evoked potentials, EEG, and TCD were successfully obtained throughout the entire period of internal carotid artery occlusion in 99%, 95%, and 63% of patients respectively. Two patients (1.3%) suffered intraoperative cerebral infarction detected by clinical neurological examination and subsequent magnetic resonance imaging. Somatosensory evoked potentials accurately predicted intraoperative cerebral infarction in both instances without false negatives or false positives, EEG yielded one false negative result and no false positive results and VMCAi one true positive, four false positive and no false negative results. Transcranial Doppler ultrasound detection of emboli did not correlate with postoperative neurological deficits. Nevertheless the sensitivity and specificity of each test was not significantly different than the others because of the small number of disagreements between tests.

CONCLUSION

A >50% decrease in the cortically generated P25 amplitude of the median somatosensory evoked potentials, which persisted during the entire period of internal carotid artery occlusion, appears to be the most reliable method of monitoring for intraoperative ischemia in our hands because it accurately detected both intraoperative strokes with no false positive or false negative results.

Prophylaxis to avert exacerbation/relapse of multiple sclerosis in affected patients undergoing surgery. Surgical observations and recommendations

To provide the neurological and neurosurgical communities with case evidence of postoperative multiple sclerosis (MS) relapse, literature review to support operative stress-induced relapse and recommendations for perioperative prophylaxis to prevent relapse in patients undergoing surgery. Two case studies are presented with recommendations based on an extensive review of the medical literature and personal experience to support perioperative prophylactic suggestions. Both patients fully recovered to preoperative functional status after treatment. We now routinely implement perioperative prophylaxis to MS patients undergoing surgery at our institution with no complications to date. Perioperative prophylaxis in patients with MS undergoing surgery can prevent relapse. It is of utmost importance that the surgical community realizes that prophylactic treatment is available and should be utilized during elective and emergent surgical situations.

Quality of perioperative AEP—variability of expert ratings

BACKGROUND

Previous studies suggest that auditory evoked potentials (AEP) may be used to monitor anaesthetic depth. However, during surgery and anaesthesia, the quality of AEP recordings may be reduced by artefacts. This can affect the interpretation of the data and complicate the use of the method. We assessed differences in expert ratings of the signal quality of perioperatively recorded AEPs.

METHODS

Signal quality of 180 randomly selected AEP, recorded perioperatively during a European multicentre study, was rated independently by five experts as 'invalid' (0), 'poor' (1), or 'good' (2). Average (n=5) quality rating was calculated for each signal. Differences between quality ratings of the five experts were calculated for each AEP: inter-rater variability (IRV) was calculated as the difference between the worst and best classification of a signal.

RESULTS

Average signal quality of 57% of the AEPs was rated as 'invalid', 39% as 'poor', and only 4% as 'good'. IRV was 0 in only 6%, 1 in 62%, and 2 in 32% of the AEP, that is in 32% one expert said signal quality was good, whereas a different expert thought the identical signal was invalid.

CONCLUSIONS

There is poor agreement between experts regarding the signal quality of perioperatively recorded AEPs and, as a consequence, results obtained by one expert may not easily be reproduced by a different expert. This limits the use of visual AEP analysis to indicate anaesthetic depth and may affect the comparability of AEP studies, where waveforms were analysed by different experts. An objective automated method for AEP analysis could solve this problem.

A marked decrease in bispectral index with elevation of suppression ratio by cervical haematoma reducing cerebral perfusion pressure

A 77-year-old man with a ruptured abdominal aortic aneurysm undergoing aneurysmectomy were anaesthetised with ketamine under bispectral index (BIS) monitoring, which is a clinical EEG monitor for measurement of depth of anaesthesia/sedation. First marked BIS reduction with elevation of suppression ratio (SR) was observed following severe hypotension by deflation of the aortic occlusion balloon. The re-inflation and rapid blood transfusion improved haemodyanamics and BIS and SR. At second marked BIS reduction with SR elevation, a heavy cervical swelling due to a massive subcutaneous haematoma around the previously mis-punctured right carotid artery extending throughout the whole neck was observed without hypotension. Cervical relief incision improved the BIS and SR. The present case suggests that BIS monitor may be a simple and convenient monitor for cerebral ischaemia detection.

Methods for assessing adequacy of anesthesia

Assessing adequacy of anesthesia requires evaluation of its components: hypnosis, analgesia, and neuromuscular transmission. In order to do this, many methods have been developed that process signals representing different modalities. Assessment of hypnosis requires cortical measures of the central nervous system (CNS); methods that assess analgesia concentrate on subcortical and spinal levels of the CNS; and neuromuscular transmission is a peripheral phenomenon. This article presents an overview of the current state of methods available for measuring each of these components. We conclude that, whereas important gains have been made in the area of assessment of hypnosis, mainly owing to the advancement of methods using EEG and auditory evoked potentials, and whereas neuromuscular transmission can be objectively monitored using motor nerve stimulation, assessment of analgesia still contains many challenges.

[Assessment of anesthesia adequacy with spectral analysis of the heart sinus rhythm]

The information density of spectral analysis of the variability of sinus rhythm to be used in diagnosing the neurovegetative activity in operation trauma was studied in 32 patients in the course of anesthesia and operation. It is suggested on the basis of the found the method can in monitoring the anesthesia adequacy.

Guidelines for inspiratory flow setting when measuring the pressure-volume relationship

Acquisition of pressure-volume (PV) curves to improve ventilation strategy is time consuming when using static methods. Low-flow techniques use less time, but compliance values can be decreased by the resistance to flow in airways and tracheal tube (P-t). In this study, we determined the impact of three flows on the resistive component of airway pressure during anesthesia. We studied 10 ASA status P1/P2 patients with normal respiratory function. Airway and esophageal pressures were measured while volume-control ventilated with 6, 12, and 30 L/min continuous flows. PV curves, lower inflection point, respiratory system, and chest wall compliances at 250, 500, 750, and 1000 mL tidal volume were established before and after removing P-t. Data were submitted to analysis of variance. The inflection point was lower for the lower flow when comparing 6 and 12 with 30 L/min (P < 0.001). No difference was found between 6 and 12 L/min. Removal of P-t showed a difference only for 30 L/min (P = 0.004). Higher flows generated lower compliances. P-t subtraction reduced compliances only for 30 L/min. Chest wall compliances showed no difference between flows. We concluded that flows < or =12 L/min minimize P-t during intraoperative PV curves acquisition. Compliances suggest 6 L/min as the most adequate flow.

IMPLICATIONS

We suggest guidelines for inspiratory flow setting when measuring the pressure-volume relationship during anesthesia based on the comparison among three different continuous flow values, aiming at better intraoperative respiratory settings in patients with normal respiratory function.

Pressure-flow loops and instantaneous input impedance in the thoracic aorta: another way to assess the effect of aortic bypass graft implantation on myocardial, brain, and subdiaphragmatic perfusion

BACKGROUND

The serious disturbances in ventriculoarterial coupling after thoracic aorta bypass grafting are addressed through aortic entry impedance in the frequency domain from flow-pressure waves. We designed a method for synthesizing pressure and flow waves to evaluate opposal to aortic flow along the cardiac cycle, addressing myocardial, brain, and visceral tissue perfusions from pressure-flow hysteresis loops and forward-backward aortic entry impedance in the ascending aorta, transverse aortic arch, and distal descending aorta, respectively, before and after extra-anatomic grafting of the descending aorta in the swine.

METHODS

Twelve pigs underwent extra-anatomic grafting (woven double-velour prosthesis, 18-mm diameter), bypassing the descending aorta. Periarterial flow and endovascular pressure signals were mathematically synthesized (error minimization) to yield continuous functions of flow, pressure along the cardiac cycle before treatment for mean hemodynamics, pressure-flow hysteresis loops, and aortic entry impedance.

RESULTS

Grafting of the descending aorta overshadowed pressure-flow hysteresis loops in the ascending aorta by shortening maximum pressure delay on maximum flow and diastolic flow reversal. Clamping of the descending aorta substantially restored hemodynamics in the ascending aorta, although the diastolic flow decrease was accelerated. Identical processes developed in the transverse aorta. Subdiaphragmatic descending aortic flow was flattened after grafting and restored, although thickened, after clamping of the descending aorta. Flow wave peak was framed by a diastolic aortic entry impedance peak, which was damped along the transverse aortic arch (aortic entry impedance peak in the ascending aorta, 1700 +/- 102 kN x s x m(-5); aortic entry impedance peak in the descending aorta, 292 +/- 45 kN x s x m(-5); P <.05). After grafting, the aortic entry impedance peak was transferred to early systole (aortic entry impedance peak in the transverse aortic arch, 2104 +/- 94 kN x s x m(-5); aortic entry impedance peak in the descending aorta, 450 +/- 75 kN x s x m(-5); P <.05). Clamping of the descending aorta attenuated the early systolic aortic entry impedance peak (aortic entry impedance peak in the transverse aortic arch, 1269 +/- 104 kN x s x m(-5); aortic entry impedance peak in the descending aorta, 491 +/- 75 kN x s x m(-5); P <.05), although aortic entry impedance in the descending aorta remained higher than before grafting (P <.05). Specifically, the backward flow ascending aorta to coronary trunks generated a backward aortic entry impedance peak (2234 +/- 350 kN x s x m(-5)) superimposed onto the forward aortic entry impedance peak with asymptotic boundaries that diminished after grafting and further enlarged after clamping of the descending aorta.

CONCLUSIONS

Hemodynamic opposition of grafting of the descending aorta are specific to the aortic site and cardiac cycle and are dependent on clamping of the descending aorta. Our approach to thoracic aorta hemodynamics could enable optimization of bypass grafting.

Evaluating intraoperative therapeutic and diagnostic interventions

A cost-conscious health care system requires detailed measures of its activities, including measurements of care provided to perioperative patients. Because there are no scoring systems that quantify the extent of intraoperative care interventions, we developed an intraoperative therapeutic intensity score (I-TIS). Physiological/biochemical monitoring and therapeutic interventions were assigned one to four points on the basis of the resource utilization and/or intensity of care they each reflect. Scoring was performed on actual patients, and the results were compared with ASA classification and surgical complexity. A 78-item scoring system was developed and assessed by using two patient groups. Group 1 (n = 307) entered the postanesthesia care unit (PACU) for short postoperative stays and had an I-TIS of 7.3 +/- 5.0; Group 2 patients (n = 443) were either admitted to the surgical, cardiothoracic, or neurosurgical intensive care units or had extended PACU stays, and they had an I-TIS of 25.2 +/- 12.4 (P < 0.001 versus Group 1). The correlation of I-TIS with the surgical complexity classification was r = 0.77, with ASA base relative value units was r(s) = 0.75, and with the ASA physical status classification was r(s) = 0.49. The score correlated well with surgical complexity and was able to differentiate between the intensity of care during various surgical procedures.

IMPLICATIONS

A scoring system to quantify the extent of nonsurgical intraoperative care was developed. The scoring system was validated and correlated well with surgical complexity; it was able to differentiate between the intensity of care provided during various surgical procedures.

Regulatory and medical-legal aspects of intraoperative monitoring

Public policies are in place for health care to insure high quality, organized delivery of care to patients. Public policy issues for intraoperative monitoring include billing, coding, reimbursement, staffing, device approval, and liability. Staffing issues include privileging, credentialing, certifying, training, and professionalism. Those staffing processes provide ways that the profession passes judgment on individual's skills, knowledge, abilities, and training relevant to monitoring. These issues are reviewed here, along with a discussion of the respective roles of physicians and non-physicians in monitoring. Various billing codes for intraoperative monitoring are reviewed along with the circumstances in which they are to be used. Policy on the use of non-approved devices is also presented.

Tourniquet safety in lower leg applications

PURPOSE

To reduce the chance of injury due to pneumatic tourniquet use, the minimum cuff pressure required to maintain a bloodless field should be used. The purpose of this study was to find out if Limb Occlusion Pressure (LOP--the cuff pressure required to occlude arterial flow) is lower with a wide contoured cuff than with a standard width cylindrical cuff at the calf, if cuff pressures based on measured LOP will be lower than the typical 250 mmHg used in lower leg cuffs, and if a new automatic LOP measurement method gives the same results as the standard Doppler stethoscope method.

SAMPLE

16 adult volunteers were tested in a controlled laboratory setting, and 53 clinical cases were reviewed at two centers.

DESIGN

Repeated measures comparison of LOP on volunteers with the two different cuffs and measurement methods, and review of clinical cases.

RESULTS

LOP was lower with the wide cuff on all volunteers (mean reduction 20 mmHg, SD 8.6, range 5-35, p < 0.001). The average difference of 1.2 mmHg between Doppler and automatic LOP readings was not significant (p = 0.43). Based on the volunteer results, using LOP plus a safety margin of 40, 60, or 80 mmHg (for LOP < 130, 131-190, or 190+ respectively) with a standard width cylindrical cuff will lead to an average cuff pressure of 223 mmHg (range 170-299, SD 36), 11% lower than typical practice and up to 80 mmHg (32%) lower on some patients. Using a wide, contoured cuff should further reduce cuff pressures to an average of 195 mmHg (range 160-280, SD 33), 22% lower than typical practice and a reduction of up to 90 mmHg (36%). At two clinics, the wide cuff maintained a bloodless field in 48 out of 53 cases (91%) when used at 200 mmHg.

CONCLUSIONS

Using a wide, contoured cuff at the calf should reduce required cuff pressures compared to a standard cuff. Setting cuff pressure based on LOP should further reduce cuff pressures for most patients compared to typically used pressures. With continued development, the new automatic method may become a viable alternative to the Doppler method and may make LOP measurement more practical in the clinical setting.

Monitoring bladder temperatures in the OR

Temperature monitoring via the urinary bladder has become common in the OR, often replacing monitoring at the rectal site. A systematic, integrated review and synthesis of the literature was undertaken to assess the validity of using the urinary bladder as a site for temperature measurement in the OR. During steady thermal states, bladder temperature performed well, providing temperatures similar to those of core sites. In contrast, poor performance was demonstrated during rapid thermal changes, such as during the rapid cooling and rewarming phases of cardiopulmonary bypass. At such times, a significant lag in response rate at the bladder site was noted by multiple investigators. This delayed responsiveness during thermally dynamic states, however, may provide information regarding the adequacy of rewarming during bypass at sites intermediate between the core and periphery. Limited research indicates that urinary bladder temperature may be influenced by urine flow rate, and additional research is required in this area. The cost effectiveness of this method of temperature measurement requires investigation as well.

Intraoperative neurophysiological monitoring in pediatric neurosurgery: why, when, how?

INTRODUCTION

This review is primarily based on peer-reviewed scientific publications and on the authors' experience in the field of intraoperative neurophysiology. The purpose is a critical analysis of the role of intraoperative neurophysiological monitoring (INM) during various neurosurgical procedures, emphasizing the aspects that mainly concern the pediatric population. Original papers related to the field of intraoperative neurophysiology were collected using medline. INM consists in monitoring (continuous "on-line" assessment of the functional integrity of neural pathways) and mapping (functional identification and preservation of anatomically ambiguous nervous tissue) techniques. We attempted to delineate indications for intraoperative neurophysiological techniques according to their feasibility and reliability (specificity and sensitivity).

DISCUSSION AND CONCLUSIONS

In compiling this review, controversies about indications, methodologies and the usefulness of some INM techniques have surfaced. These discrepancies are often due to lack of familiarity with new techniques in groups from around the globe. Accordingly, internationally accepted guidelines for INM are still far from being established. Nevertheless, the studies reviewed provide sufficient evidence to enable us to make the following recommendations. (1) INM is mandatory whenever neurological complications are expected on the basis of a known pathophysiological mechanism. INM becomes optional when its role is limited to predicting postoperative outcome or it is used for purely research purposes. (2) INM should always be performed when any of the following are involved: supratentorial lesions in the central region and language-related cortex; brain stem tumors; intramedullary spinal cord tumors; conus-cauda equina tumors; rhizotomy for relief of spasticity; spina bifida with tethered cord. (3) Monitoring of motor evoked potentials (MEPs) is now a feasible and reliable technique that can be used under general anesthesia. MEP monitoring is the most appropriate technique to assess the functional integrity of descending motor pathways in the brain, the brain stem and, especially, the spinal cord. (4) Somatosensory evoked potential (SEP) monitoring is of value in assessment of the functional integrity of sensory pathways leading from the peripheral nerve, through the dorsal column and to the sensory cortex. SEPs cannot provide reliable information on the functional integrity of the motor system (for which MEPs should be used). (5) Monitoring of brain stem auditory evoked potentials remains a standard technique during surgery in the brain stem, the cerebellopontine angle, and the posterior fossa. (6) Mapping techniques (such as the phase reversal and the direct cortical/subcortical stimulation techniques) are invaluable and strongly recommended for brain surgery in eloquent cortex or along subcortical motor pathways. (7) Mapping of the motor nuclei of the VIIth, IXth-Xth and XIIth cranial nerves on the floor of the fourth ventricle is of great value in identification of "safe entry zones" into the brain stem. Techniques for mapping cranial nerves in the cerebellopontine angle and cauda equina have also been standardized. Other techniques, although safe and feasible, still lack a strong validation in terms of prognostic value and correlation with the postoperative neurological outcome. These techniques include monitoring of the bulbocavernosus reflex, monitoring of the corticobulbar tracts, and mapping of the dorsal columns. These techniques, however, are expected to open up new perspectives in the near future.

[Analysis of the anesthesiologist's vigilance with an eye-tracking device. A pilot study for evaluation of the method under the conditions of a modern operating theatre]

INTRODUCTION

With the inclusion of new monitoring devices over the last two decades, the distribution of the anesthesiologists vigilance has changed which might influence the ergonomic profile of an optimal anesthesia workstation. The aim of this pilot study was the evaluation of an eyetracking device to analyze the vigilance distribution of an anesthesiologist during routine cases in an operating theatre of the 21st century.

MATERIAL AND METHODS

Five anesthesiologist with different levels of training were followed during different types of surgery using a video camera-based eye-tracking system. The films were analyzed by an independent observer and rated according to defined regions of interest (ROI). Then typical scan-paths were identified and quantitatively analyzed.

RESULTS

The eye-tracking studies proved to be technically of high quality but were time-consuming. Only few disturbances to the operating room (OR) personnel were recorded according to their subjective impressions but bias of behaviour due to the measurement procedure itself cannot be completely excluded. The vigilance of the anesthesiologist towards different factors was dependent on the level of professional training, the type of anesthesia and the type of surgery. Certain factors such as documentation (10-15%) or external disturbances (approximately 20%) proved to be relatively constant. Typical scan-paths could also be identified.

CONCLUSION

Eye-tracking studies proved to be a suitable way to analyze the distribution of vigilance of anesthesiologists in a modern operating theatre. For further studies examining the influence of detailed modifications of the OR environment, a standardized study design with the same level of education, the same anesthesia technique and the same surgical procedure needs to be chosen.

Profound hypotension: ethical considerations

The use of profound induced hypotension to provide better operating conditions for surgery is long established. However, it is a controversial technique and it may be argued that it is inappropriate in modern anaesthetic practice. A currently used technique is reviewed against the benchmark of a lawsuit concerning profound hypotension.

Local anaesthetic techniques in ophthalmic surgery

This article, which won third place in the Alison Bell Writer's Award this year, reports the findings of a literature review that explored the use of local anaesthetic techniques used in ophthalmic surgery. The author describes the various ophthalmic procedures that can take place under local anaesthetic and asks whether there is a need for an anaesthetist to be present for such lists. Issues such as patient monitoring requirements and intravenous access are also discussed, emphasising the importance of the nurse's role in informing, supporting and comforting the patient through what can be a stressful experience.

Prevention of spinal cord injury with time-frequency analysis of evoked potentials: an experimental study

OBJECTIVES

To verify the applicability and validity of time-frequency analysis (TFA) of evoked potential (EP) signals in detecting the integrity of spinal cord function and preventing spinal cord injury.

METHODS

The spinal cord was simulated during surgery in 20 mature rats by mechanically damaging the spinal cord. Cortical somatosensory evoked potential (CSEP), spinal somatosensory evoked potential (SSEP), cortical motor evoked potential (CMEP), and spinal cord evoked potential (SCEP) were used to monitor spinal cord function. Short time Fourier transform (STFT) was applied to the CSEP signal, and cone shaped distribution (CSD) was used as the TFA algorithm for SSEP, CMEP, and SCEP signals. The changes in the latency and amplitude of EP signals were measured in the time domain, and peak time, peak frequency, and peak power were measured in the time-frequency distribution (TFD).

RESULTS

The TFDs of EPs were found to concentrate in a certain location under normal conditions. When injury occurred, the energy decreased in peak power, and there was a greater dispersion of energy across the time-frequency range. Strong relations were found between latency and peak time, and amplitude and peak power. However, the change in peak power after injury was significantly larger than the corresponding change in amplitude (p<0.001 by ANOVA).

CONCLUSIONS

It was found that TFA of EPs provided an earlier and more sensitive indication of injury than time domain monitoring alone. It is suggested that TFA of EP signals should therefore be useful in preventing spinal cord injury during surgery.

Thoracic and thoracoabdominal aortic aneurysm repair: use of evoked potential monitoring in 118 patients

PURPOSE

Paraplegia is the most dreaded and severe complication of surgery on the descending thoracic aorta (TAA) and thoracoabdominal aorta (TAAA). The functional integrity of the spinal cord can be monitored by means of intraoperative recording of myogenic-evoked responses after transcranial electrical stimulation (tcMEP) and somatosensory-evoked potential (SEP) monitoring. In this study, we evaluated the results of evoked potential monitoring and the adequacy of the strategy followed.

METHOD

The spinal cord of 118 patients (78 men; age, 65 +/- 12 years; 79 TAAAs, 39 TAAs) undergoing surgery on the TAA or TAAA was monitored with tcMEP and SEP. Spinal cord protection was achieved by means of a multimodality approach: moderate hypothermia (32 degrees C rectal temperature), continuous cerebrospinal fluid drainage to keep the pressure less than 10 mm Hg, reimplantation of intercostal arteries, left ventricular bypass grafting, and staged clamping. In the case of evoked potential changes more than 50% of baseline, the strategy was adjusted: reattachment of more segmental arteries when technically feasible, higher distal and proximal perfusion pressures, and enhanced cerebrospinal fluid drainage.

RESULTS

Forty-two of 118 patients (35.6%) had a more than 50% of baseline tcMEP reduction during cross-clamping. At this point, only 5 of those 42 cases were also associated with SEP reduction of more than 50% of baseline. On the basis of the tcMEP findings, the strategy was adjusted. Five patients had postoperative paraplegia (4.2%).

CONCLUSION

tcMEP monitoring seems to be a useful adjunct of the protective techniques and may cause substantial adjustments in strategy, reducing the incidence of postoperative paraplegia.

A closer look at bispectral index monitoring

The most common fear expressed by preanesthesia patients is experiencing awareness while under general anesthesia. Although extremely rare, awareness during anesthesia does occur and patients have recalled explicit details and conversations that occurred while they were under general anesthesia, including described recall of the intubation process. The Bispectral Index Monitor (BIS) was developed by Aspect Medical System of Newton, MA, to measure patient response to the administration of potent sedative, hypnotic agents. The BIS monitor is intended to decrease the risk of intraoperative awareness by providing the anesthetist with a quantitative assessment regarding the hypnotic state of the patient.

The Cytoscan model E-II in intraoperative parathyroid gland identification in a rabbit model

BACKGROUND

Intraoperative parathyroid gland identification and preservation is often a challenge even in the hands of experienced surgeons as they could be indistinguishable from fat or thyroid tissue.

OBJECTIVE

The goal of this study was to demonstrate the use of the Cytoscan Model E-II, which uses orthogonal polarization spectral (OPS) imaging technology, as an intravital microscope in identifying parathyroid glands intraoperatively and differentiating the parathyroid glands from fat and thyroid tissue in a rabbit model.

METHODS

The necks of 4 New England white rabbits were explored with the animals under a general anesthesia. The Cytoscan was used to obtain images of the vasculature of tissue suspected to be parathyroid, fat, and thyroid tissue. These were confirmed by histologic evaluation.

RESULTS

All tissues were correctly identified by the Cytoscan and confirmed by histologic analysis. There was an obvious difference in the images obtained of fatty tissue as compared with parathyroid tissues. There was also an appreciable difference between parathyroid and thyroid tissue based on the difference in vascularity.

CONCLUSIONS

OPS imaging technology can be used in identifying parathyroid glands based on the difference in vascularity from fat and the pattern and density of vessels when compared with thyroid tissue in a rabbit model.

SIGNIFICANCE

The Cytoscan may play a future role in real time intraoperative identification of human parathyroid glands. Future investigation is warranted.

Flow measurement in coronary surgery

BACKGROUND

Many of the modern less invasive approaches to coronary artery bypass grafting (CABG) are performed without the use of the heart lung machine and cardiac asystole. Even after the introduction of mechanical stabilizers, the ability to achieve a technically perfect anastomosis is less certain in beating heart bypass surgery. Our group has begun to assess the surgical results of beating heart CABG using Transit Time Flow Measurement (TTFM). Our experience indicates that a meticulous and controlled method of assessing the results of intraoperative flow measurements can improve the quality of information and increases the accuracy of diagnosing technical problems with newly constructed bypass grafts. For this reason, we developed a standard algorithm for using and interpreting intraoperative TTFM.

METHODS

From January to August of 1998, 161 patients underwent off-pump CABG with a total of 323 distal anastomoses (2.0 grafts per patient). All completed grafts were tested intraoperatively with TTFM and the decision to accept or revise any individual graft was based on a decision nomogram using key values readily available from the TTFM output.

RESULTS

Thirty-two grafts (9.9%) were surgically revised based on unsatisfactory flow curves, the Pulsatile Index, or both. All revised grafts were found to have a significant technical error, such as an intimal flap, thrombus, conduit kinking, or dissection. There were no major complications, myocardial infarctions, or deaths in the entire series of patients.

CONCLUSIONS

Based on our favorable use of TTFM, we strongly recommend that patency of every graft be assessed whether the operation is performed off pump or on cardiopulmonary bypass. Guidelines for performing and interpreting TTFM ensure a high degree of confidence in the completed graft. The decision to revise a graft can be made based on simple parameters easily acquired from the TTFM device. Any concern about quality or quantity of flow should prompt immediate revision.

Routine intra-operative assessment of pain and/or depth of anaesthesia by nurse anaesthetists in clinical practice

Patient safety and comfort during general anaesthesia and surgery are to a considerable extent dependent on the capability of anaesthesia personnel to interpret directly monitored as well as indirect clinical signs of pain and/or depth of anaesthesia. The aim of the present study was to evaluate how nurse anaesthetists in their clinical routine work assess and interpret intra-operative responses evoked by pain stimuli and/or insufficient depth of anaesthesia. A questionnaire was designed to assess the perceived relevance and validity of cardiovascular, respiratory, mucocutaneous, eye-associated, and muscular responses for routine assessment of intra-operative pain and/or insufficient depth of anaesthesia in patients undergoing surgery under general anaesthesia. Data were obtained from 223 nurse anaesthetists working at nine different university anaesthesia departments in Sweden. A number of significant indicators for pain and depth of anaesthesia could be identified for spontaneously breathing as well as for mechanically ventilated patients. No variable was considered entirely specific for either intra-operative pain or depth of anaesthesia. Changes in breathing rate/volume, central haemodynamics (BP, HR), lacrimation, and presence of moist and sticky skin were given higher score values as indicators of pain than as indicators of depth of anaesthesia. Occurrence of grimaces, attempted movements, and presence of non-centred pupils were variables considered more indicative of insufficient depth of anaesthesia than intra-operative pain. In conclusion, it is obvious from the present data that indirect physiological signs of intra-operative pain and depth of anaesthesia are still considered of importance by Swedish anaesthesia nurses in the anaesthetic management of surgical patients.

Cerebral microembolization during pediatric scoliosis surgery: a transcranial doppler study

SUMMARY

The goal of this study was to identify cerebral microemboli during scoliosis surgery and their potential relationship with visual alterations. Transcranial Doppler identified high-intensity transient signals (HITS) during surgery in both middle cerebral arteries, and ophthalmologic examination assessed their potential effects on the visual system. Thirteen children (age 13-17 years) undergoing surgery for scoliosis or kyphosis with spine curvature >45 degrees were studied. HITS were identified in 92%. Eleven patients had a total count of <15 HITS, but in the remaining two the count was unexpectedly high (63 and 265 HITS). Echocardiography in these two patients indicated the presence of an atrial right-to-left shunt. Uneventful preoperative and postoperative visual function was found in 11 patients. One patient had preoperative blindness and in another ophthalmologic complications developed not related to microembolization. Scoliosis surgery is frequently associated with low counts of cerebral microemboli. It appears that such low embolic counts have no effects on postoperative visual function as determined clinically. Some patients may show high rates of microemboli, which may be related to the presence of right-to-left cardiac shunts. The impact of these signals on brain function remains to be investigated.

A cardiopulmonary bypass score system to assess quality of perfusion performance

During cardiopulmonary bypass, the perfusionist maintains physiological parameters laid down in protocols; this is his or her performance capability. In order to assess his or her performance we need to be able to analyse these physiological parameters objectively. We defined six parameters, pH, BE, PaCO2, PaO2, ACT and oesophageal temperature and gave them ideal values of 7.40+/-0.05, 0.0+/-2.5 mmol/l, 39.0+/-3.0 mmHg, 150+/-50 mmHg, 540+/-60 s and 37.2+/-0.2 degrees C, respectively. We established ranges and a score system: +/- one standard deviation of the mean for a score of zero; between +/- one and two standard deviations for a score of one; and greater than +/- two standard deviations for a score of two. We captured and analysed the most outlying value, with respect to known normal values, for each parameter recorded on the pump sheet. This was performed for 100 consecutive patients. Mean +/- standard deviation (medians) values for pH, BE, PaCO2, PaO2, ACT and oesophageal temperature were 7.41+/-0.07 (7.41), -1.85+/-2.37 mmol/l (-1.85 mmol/l), 34.6+/-5.42 mmHg (34.0 mmHg), 320+/-96.2 mmHg (317 mmHg), 558+/-164 s (503 s) and 37.3+/-0.5 degrees C (37.4 degrees C), respectively. We then analysed what percentage of our 100 patients fell within each score range for each of the six parameters. This is an efficient means in analysing whether the perfusionist abides by the protocols, what quality is supplied to the patient, does he or she react when he or she is faced with parameters that are out of range and finally advocating in-line blood gas monitoring. This is another step towards our goal of total quality management.

What is the yield of intraoperative ultrasonography during partial hepatectomy for malignant disease?

BACKGROUND

Previous studies have shown that intraoperative ultrasonography (IOUS) during hepatic resection for malignancy changes the operative plan or identifies occult unresectable disease in a large proportion of patients. This study was undertaken to reassess the yield of IOUS in light of recent improvements in preoperative staging.

STUDY DESIGN

Patients with potentially resectable primary or metastatic hepatic malignancies subjected to exploration, bimanual palpation of the liver, and IOUS were evaluated prospectively. Intraoperative findings were recorded, and preoperative imaging studies were reanalyzed by radiologists blinded to the intraoperative findings. The extent of disease based on preoperative imaging was compared with the intraoperative findings.

RESULTS

From October 1997 until November 1998, 111 patients were evaluated. At exploration, a total of 77 new findings or findings different than suggested on the imaging studies were identified in 61 patients (55%), the most common of which was additional hepatic tumors (n = 37). Thirty-five of 77 (45%) new findings were identified by IOUS alone and 10 (13%) by palpation alone; the remainder were identified by both palpation and IOUS. Forty-seven of 61 patients (77%) underwent a complete resection despite new intraoperative findings, with a modification (n = 28) or no change (n = 19) in the planned operation. Twenty-one patients (19%) had new findings identified only on IOUS. Thirteen of these patients underwent resection with no change in the operative plan, six underwent a modified resection and two were considered to have unresectable disease based solely on the findings of IOUS.

CONCLUSIONS

In patients with hepatic malignancies submitted to a potentially curative resection, new intraoperative findings or findings different than suggested on preoperative imaging studies are common. But resection with no change in the operative plan or a modified resection is still possible in the majority of patients despite such findings. The findings on IOUS alone rarely lead to a change in the operative plan.

Shape and movement of the interatrial septum predicts change in pulmonary capillary wedge pressure

We aimed to assess whether movement of the interatrial septum predicts change in pulmonary capillary wedge pressure (PCWP). In 71 patients undergoing cardiac surgery, the interatrial septum was categorised by its shape and movement using transesophageal echocardiography. Fixed curvature (FC) was identified by bowing of the interatrial septum from left to right throughout the cardiac cycle, mid-systolic reversal (MSR) by minimal septal movement and transient reversal (right to left) during mid-systole, and mid-systolic buckling (MSB) by marked movement and buckling of the septum during mid-systole. These were compared with PCWP. Sensitivity and interobserver reliability was studied with continuous PCWP and TEE measurement during a period of acute volume alteration in 10 additional patients. Interatrial septal movement predicted PCWP, with mean PCWP (95% confidence intervals) for FC, 18.1 mmHg (16.7 to 19.6), MSR 13.2 mmHg (12.5 to 13.8) and MSB, 9.9 mmHg (9.0 to 10.7) mmHg. The mean PCWP at which a change in pattern occurred was 8.9 mmHg (8.3 to 9.6) for MSR to MSB, and 10.9 mmHg (10.1 to 11.8) for MSR to FC (p<0.001). There was no significant difference in mean values for all three observers. Movement of the interatrial septum predicts change in PCWP.

Intraoperative and early postoperative gastric intramucosal pH predicts morbidity and mortality after major abdominal surgery

The present study was undertaken to investigate the correlation between the intraoperative and postoperative gastric intramucosal pH (pHi) with important perioperative variables and to explore any potential relationship of the measured pHi with the patients' postoperative course. A prospective study was carried out in a group of 48 patients who underwent major abdominal operations over an 8-month period at St. John Hospital and Medical Center. An automated air tonometer was used for gastric pHi monitoring. Twenty-eight elective and 20 emergency abdominal operations were performed in 23 men and 25 women. Twenty-six patients (54%) required postoperative hospitalization in the Intensive Care Unit (ICU). Seventeen patients (35%) developed early postoperative complications. The non-ICU and ICU mortality rates were 4.5 and 19.2 per cent respectively. The mean intraoperative pHi (pHiOR) and postoperative pHi (pHiPO) ranged between 7.03 and 7.58 (7.38+/-0.12) and 6.89 and 7.56 (7.35+/-0.12) respectively (mean +/- standard deviation). There was a significant decrease of the gastric pHi at the first hour intraoperatively compared with the pHi after induction to anesthesia (7.44 vs 7.38+/-0.14, P < 0.001). Patients who underwent emergent abdominal procedures were characterized by lower pHiOR and pHiPO values (7.43+/-0.08 vs 7.30+/-0.13 and 7.39+/-0.84 vs 7.30+/-0.15, P < 0.001 and P < 0.05). Similarly patients who required surgical ICU admission had significantly lower pHiOR and pHiPO measurements (7.3+/-0.12 and 7.28+/-0.12) compared with the rest (7.46+/-0.06 and 7.43+/-0.06; P < 0.001). Overall, lower pHiOR and pHiPO values were associated with the occurrence of postoperative complications (P < 0.001), the postoperative mortality (P < 0.001), the requirement for postoperative mechanical ventilator (P < 0.001) and its duration (P < 0.001), longer ICU stay (P < 0.001), and prolonged hospitalization (P < 0.05). Evidence of intraoperative and early postoperative gastric mucosal ischemia (pHiOR and pHiPO < or = 7.32) was observed in 12 (25%) and 15 (31%) patients respectively. The incidence of postoperative complications and the mortality rate were higher in this group of patients (P < 0.001). At a cutoff point of 7.32 gastric pHiOR gave a sensitivity of 69 per cent and specificity of 97 per cent for predicting postoperative complications as well as a sensitivity and specificity of 67 per cent and 81 per cent for predicting death. Intraoperative and early postoperative gastric pHi is a reliable predictor of patient outcome after major abdominal operations. Splanchnic ischemia may play an important role in determining early complications and survival; therapy guided by the gastric pHi might improve outcome.

Respiratory physiopathology in surgical repair for large incisional hernias of the abdominal wall

BACKGROUND

The computerized noninvasive measurement of respiratory mechanics enables new prospects in the study of respiratory physiopathology in surgical repair of large incisional hernias.

STUDY DESIGN

We studied 10 patients with COPD ventilated with a Servo Ventilator 900C. We measured inspiratory flow by means ofa pneumotacograph, the volume by integrating the flow signal, and esophageal and airway opening pressure by means of two differential pressure transducers (an esophageal balloon measures, separately, chest wall and lung mechanical properties). The signals were sent by an analogic-digital converter to a personal portable computer to be analyzed. We calculated compliance of total respiratory system (Crs), chest wall (Ccw), and lung (CI); maximum resistance of the total respiratory system (Rmax, Rs), chest wall (Rmax, w), and lung (Rmax, L); and work of breathing (Wob). Statistics were performed using one-way analysis of variance and p = 0.05 was considered significant.

RESULTS

At the closure of the peritoneum a reduction of Crs and Wob was recorded in seven patients in whom a PTFE prosthesis widening the abdominal cavity was used to restore the baseline value. Variations in respiratory compliance are from variations in Ccw with unaffected CI (Ccw varied from 0.180 to 0.130 L/cmH2O at peritoneal closure and from 0.130 to 0.170 L/cmH2O by prosthetic peritoneal widening). Respiratory resistances remained unchanged (11.3 cmH2O/ L/s) at any time of measurement.

CONCLUSIONS

The intraoperative assessment of respiratory mechanics is useful to evaluate and eventually to decrease the mechanical workload (prosthesis widening peritoneum or fascia incisions). The passive mechanical work performed by the ventilator needs to be kept constant or no higher than 10% basic data: if these conditions are maintained, mostly in patients with COPD, there is no risk of respiratory muscular fatigue during the postoperative period.