Video recording of cardiac surgical procedures: what the surgeon needs to know.

In the past, rudimentary devices were used to record surgical operations. Currently, the introduction of technologic advances such as high-definition television and the miniaturization of high-resolution digital video cameras provides an opportunity for making significantly enhanced surgical records. These enhancements, coupled with the recent advances in telemedicine and surgical simulation, will improve cardiac surgery training and skill acquisition, decrease operative times and costs, minimize morbidity, and improve overall patient care. The present paper provides a discussion of the media technology offered to surgeons for recording a surgical procedure on video. Hardware technology, including different types of cameras and analogical or digital post processing methods, are reviewed with a surgical ''eye''. This ''how to'' paper provides practical suggestions to surgeons in order to enhance surgical video recording.

Serotonin facilitates AMPA-type responses in isolated siphon motor neurons of Aplysia in culture.

1. Serotonin (5-HT) facilitates the connections between sensory and motor neurons in Aplysia during behavioural sensitization. The effect of 5-HT on sensorimotor synapses is believed to be primarily presynaptic. Here we tested whether 5-HT can have an exclusively postsynaptic facilitatory effect. 2. Siphon motor neurons were individually dissociated from the abdominal ganglion of Aplysia and placed into cell culture. Brief pulses of glutamate, the putative sensory neuron transmitter, were focally applied (0.1 Hz) to solitary motor neurons in culture, and the glutamate-evoked postsynaptic potentials (Glu-PSPs) were recorded. 3. When 5-HT was perfused over the motor neuron for 10 min, the amplitude of the Glu-PSPs was significantly increased. The 5-HT-induced enhancement of the Glu-PSPs persisted for at least 40 min after washout. 4. Prior injection into the motor neuron of the calcium chelator BAPTA, GDP-beta-S or GTP-gamma-S blocked the 5-HT-induced facilitation of the Glu-PSPs. However, the facilitation was not blocked when APV, an NMDA receptor antagonist, was applied together with the 5-HT. 5. The enhancement of the Glu-PSPs by 5-HT was reversed by the AMPA receptor antagonist DNQX, indicating that 5-HT increased the functional expression of AMPA-type receptors in the motor neuron. 6. The presence of botulinum toxin in the motor neuron blocked the 5-HT-induced enhancement of the Glu-PSPs. As botulinum toxin prevents exocytosis we hypothesize that during sensitization 5-HT causes the insertion of additional AMPA-type receptors into the postsynaptic membrane of sensorimotor synapses via exocytosis. This postsynaptic mechanism may contribute to facilitation of the synapses.

Estrogen therapy in women undergoing coronary artery bypass grafting: effect on surgical complications.

OBJECTIVE: To determine whether estrogen therapy at the time of coronary artery bypass grafting affects postoperative complications. METHODS: Consecutive postmenopausal women who had coronary artery bypass grafting between 1992 and 1997 were identified and their medical records were reviewed. Outcome measures included mortality, perioperative cardiac morbidity, and early and late postoperative complications. RESULTS: Estrogen therapy was noted in 13.9% of 734 women. Those using estrogen replacement were younger (63.9 +/- 0.27 versus 68.8 +/- 0.64 years) and had higher ejection fractions (2.8 +/- 0.11 versus 3.1 +/- 0.04) and fewer vessels bypassed. Mortality rates were 2.9% for estrogen users and 7.4% for nonusers (odds ratio [OR] 0.38; confidence interval [CI] 0.07, 1.21). Perioperative cardiac morbidity rates were 5.8% for estrogen users and 11% for nonusers (OR 0.52; CI 0.23, 1.7). Early complication rates were 0. 98% for estrogen users and 1.11% for nonusers. Late inpatient complications were noted in 6.8% of treated women and 14.8% of those untreated (OR 0.42; CI 0.16, 0.96). Stepwise logistic regression confirmed age, New York Heart Association angina classification, and ejection fraction as significant variables for mortality, perioperative cardiac morbidity, and late complications. Estrogen therapy did not influence mortality, perioperative cardiac morbidity, or early or late complications. CONCLUSION: Age, ejection fraction, and New York Heart Association angina classification predicted mortality, perioperative cardiac morbidity, and late complications. Estrogen therapy at the time of admission for coronary artery bypass grafting did not influence surgical mortality, perioperative cardiac morbidity, or early or late complications.

Passive electrotonic properties of rat hippocampal CA3 interneurones.

1. The linear membrane responses of CA3 interneurones were determined with the use of whole-cell patch recording methods. The mean input resistance (RN) for all cells in this study was 526 +/- 16 MOmega and the slowest membrane time constant (tau0) was 73 +/- 3 ms. 2. The three-dimensional morphology of 63 biocytin-labelled neurones was used to construct compartmental models. Specific membrane resistivity (Rm) and specific membrane capacitance (Cm) were estimated by fitting the linear membrane response. Acceptable fits were obtained for 24 CA3 interneurones. The mean Rm was 61.9 +/- 34.2 Omega cm2 and the mean Cm was 0.9 +/- 0.3 microF cm-2. Intracellular resistance (Ri) could not be resolved in this study. 3. Examination of voltage attenuation revealed a significantly low synaptic efficiency from most dendritic synaptic input locations to the soma. 4. Simulations of excitatory postsynaptic potentials (EPSPs) were analysed at both the site of synaptic input and at the soma. There was little variability in the depolarization at the soma from synaptic inputs placed at different locations along the dendritic tree. The EPSP amplitude at the site of synaptic input was progressively larger with distance from the soma, consistent with a progressive increase in input impedance. 5. The 'iso-efficiency' of spatially different synaptic inputs arose from two opposing factors: an increase in EPSP amplitude at the synapse with distance from the soma was opposed by a nearly equivalent increase in voltage attenuation. These simulations suggest that, in these particular neurones, the amplitude of EPSPs measured at the soma will not be significantly affected by the location of synaptic inputs.

Calcium-dependent spike-frequency accommodation in hippocampal CA3 nonpyramidal neurons.

Interneurons of the hippocampal formation are traditionally identified electrophysiologically as those cells that fire trains of weakly accommodating action potentials in response to depolarizing current injection. We studied the firing properties of nonpyramidal neurons in the five substrata of the CA3b region of hippocampus. With the use of whole cell recording methods we found that nonpyramidal neurons fired in a range from weak to strong spike-frequency accommodation (SFA) that was calcium dependent. Slow afterhyperpolarizations were not associated with strong SFA. In addition a subset of interneurons ( approximately 20%) fired with an irregular firing pattern that was generally calcium independent. These results suggest a calcium-dependent mechanism for SFA in nonpyramidal neurons that is distinct from pyramidal cells and further demonstrates the heterogeneity of hippocampal interneurons.

Ethanol affects hypothalamic neurons projecting to the hippocampus and inhibits dentate granule cell LTP.

In previous studies we demonstrated that ethanol inhibition of hippocampal granule cell long-term potentiation (LTP) is mediated by angiotensin II (AII), and the inhibition can be blocked by losartan, a specific AII receptor antagonist. The purpose of the present study was to demonstrate that this low-dose ethanol inhibition of dentate granule cell LTP induction is mediated by lateral hypothalamic (LH) afferents that project to the granule cells. In urethane anesthetized rats, we compared the effects of ethanol infusion, 6.0 microliter/30 min, by means of an open-ended push-pull type cannula, in both the LH and the dentate gyrus, on dentate granule cell LTP. Results demonstrate a dose-dependent inhibition of LTP induction when the LH is perfused that can be blocked by losartan, 10 mg/kg i.p.. Four doses of ethanol were used: 5, 10, 20, and 30 mM. There was no effect when the dentate gyrus was infused with 30 mM ethanol and normal granule cell LTP was observed. Also, these results demonstrate for the first time a low-dose ethanol effect on a physiological function, LTP in a specific neural pathway, directly related to the anterograde amnesia produced by ethanol on short-term memory. Therefore, these data support our hypothesis that ethanol inhibition of LTP induction at the medial perforant path-granule cell synapse can be attributed to a presynaptic release of AII and cannot be explained in terms of a direct postsynaptic effect on the granule cells.

Surgical complications of transaxillary arteriography: a case-control study.

PURPOSE: The purpose of this study was to review the complications of transaxillary arteriography (TRAX), determine clinical factors associated with their occurrence, and define optimal treatment methods. METHODS: A retrospective review of 842 consecutive TRAX studies performed in a large, urban, tertiary care, academic medical center was undertaken. Patients with complications were compared with a concurrent randomized control group without complications with the use of a multivariate analysis model. Results of operative therapy for nerve injury were compared with those of nonoperative therapy. RESULTS: Nineteen (2.3%) complications were identified including 14 nerve injuries, four expanding hematomas/pseudoaneurysms without neurologic deficit, and one puncture site thrombosis. Several statistically significant or suggestive findings associated with the occurrence of complications were identified: female sex (odds ratio [OR] = 4.7), systolic blood pressure > or = 150 mm Hg at the conclusion of TRAX (OR = 9.5), periprocedural systemic heparin anticoagulation (OR = 7.9), concomitant use of intraarterial thrombolysis or percutaneous angioplasty (OR = 12.0), and duration of procedure > or = 90 minutes (OR = 4.0). Patients who underwent prompt exploration (< or = 4 hours from symptom onset) for nerve injuries were more likely to have complete resolution of their neurologic deficits (five of six patients) than those who were observed or underwent delayed operation (three of eight patients) (OR = 8.3). CONCLUSIONS: Aggressive treatment of post-TRAX hypertension, limitation of TRAX duration, delay of postprocedure anticoagulation, and use of alternative sites for arterial puncture in female patients or patients undergoing catheter-based intervention may reduce the incidence of TRAX-related complications. In patients who have neurologic deficits prompt surgical exploration of the puncture site with decompression of the involved nerve(s) may reduce the incidence of prolonged deficits.

Antiphospholipid antibodies in vascular surgery patients. A cross-sectional study.

BACKGROUND: Autoantibodies to phospholipid (aPL) have been associated with vascular thromboses in cerebral, coronary, and peripheral venous and arterial sites. To date, no large cross-sectional study has examined the incidence of occurrence of aPL in patients with peripheral arterial disease. METHODS: A cross-sectional study was performed with patients admitted for vascular surgery procedures to treat peripheral arterial disease for 23 months between January 1, 1990 and November 1, 1991. Consecutive patients were evaluated for the presence of aPL. Medical records for each patient were reviewed in detail, and historic, operative, and postoperative parameters were tabulated for relationship to the presence of aPL. RESULTS: Two hundred thirty-four patients underwent complete testing for aPL. All patients were receiving chronic aspirin therapy. This represented 86% of admissions. Antiphospholipid antibodies were detected in 60 patients (26%). No differences in age, sex, operation performed, or postoperative outcome were found between patients with and without aPL. However, patients with aPL were 1.8 times more likely to have undergone previous lower extremity (LE) vascular surgery than patients without aPL (95% confidence interval = 1.0 - 3.6, p = 0.047). Patients with aPL and previous LE vascular surgery were 5.6 times more likely to have had occlusion of that procedure than patients without aPL (95% confidence interval = 1.9 - 16.8, p = 0.03). The occluded previous LE procedures had a shorter duration of patency before occlusion in patients with aPL than in those without (mean duration of patency 17 months vs. 50 months, p < 0.003). Patients with occluded previous LE procedures and aPL were 4 times more likely to be female (95% C.I. = 1.4 - 11.3, p = 0.018). CONCLUSIONS: The incidence of aPL in vascular surgery patients is substantial. Vascular surgery patients with aPL are more likely to have failure of previous LE bypass procedures and to be female and the bypass failure occurs significantly more rapidly than in patients without aPL. Based on these data, testing of vascular surgery patients for aPL and investigation of alternative antithrombotic treatment regimens in patients with aPL appears warranted.

Bilateral vs single internal thoracic artery grafting for left main coronary artery occlusion.

This study was conducted to compare the coronary flow distributed by single and bilateral internal thoracic artery (ITA) grafts in the setting of the left main coronary occlusion. Ten dogs underwent coronary artery bypass grafting through a left thoracotomy, off pump, using a brief local occlusion to perform the anastomosis. Dogs were randomly assigned to receive either a single left ITA (LITA) graft to the circumflex coronary artery (CFX), or bilateral ITA grafts, with additional placement of the right ITA (RITA) to the left anterior descending artery (LAD). After the grafts were placed, the left main coronary artery was ligated. Electromagnetic flows were obtained in the LAD and the CFX proximally and distally to ITA grafts in both groups before grafting and after grafting. ITA flow in situ was also measured before rotation from the chest wall. Total left ventricular flow requirements were satisfied equally well by either a single LITA graft (116.7 +/- 11.6 mL/min) or bilateral ITA grafts (total, 116.8 +/- 9.6 mL/min divided as LITA, 55.9 +/- 7.4 mL/min; RITA, 60.9 +/- 12.0 mL/min). When two grafts were replaced, competitive flow in the proximal regions of both native vessels was noted, although basal flow requirements were maintained. When an individual graft was occluded in the bilaterally grafted system, the remaining graft immediately recruited the additional flow, demonstrating that either right or left ITA can support flow demands five to six times higher than in situ chest wall flow (RITA, 21.9 +/- 3.1 mL/min; LITA, 22.3 +/- 4.9 mL/min). These data suggest that in this canine model, a single ITA graft can support the entire flow requirements of the left ventricle. Assuming no intervening stenosis is present in native coronary systems, bilateral ITA grafting may provide a margin of safety, but under resting conditions, provides no perfusion advantages over a single ITA graft.

Correlation of North American Symptomatic Carotid Endarterectomy Trial (NASCET) angiographic definition of 70% to 99% internal carotid artery stenosis with duplex scanning.

PURPOSE: The North American Symptomatic Carotid Endarterectomy Trial (NASCET) has thus far demonstrated conclusive benefit for carotid endarterectomy for patients with symptomatic 70% to 99% internal carotid artery (ICA) stenosis. In the NASCET, ICA stenosis was classified angiographically: % ICA stenosis = (1 - [narrowest ICA diameter/diameter normal distal cervical ICA]) x 100%. However, widely used duplex scan criteria for ICA stenosis correlate with different angiographic categories of high-grade stenosis (50% to 79%, > 80%) and were developed on the basis of estimated bulb diameter. We therefore blindly evaluated with separate observers carotid angiograms from 100 patients who also underwent carotid duplex scanning in our vascular laboratory. METHODS: "Angiographic stenosis" was calculated as in NASCET. Duplex scan measurements of ICA peak systolic velocity (PSV), ICA end-diastolic velocity, and the ratio of ICA PSV to common carotid artery (CCA) PSV were analyzed for sensitivity, specificity, positive predictive value, negative predictive value, and overall accuracy to identify a 70% to 99% ICA stenosis. RESULTS: Analysis of the data revealed that an ICA PSV/CCA PSV ratio of 4.0 provided the best combination of sensitivity (91%), specificity (87%), positive predictive value (76%), negative predictive value (96%), and overall accuracy (88%) for detection of a 70% to 99% stenosis. CONCLUSION: We conclude duplex scan determination of 70% to 99% stenosis as defined in the NASCET requires the adoption of duplex criteria modified from those in current use in most vascular laboratories.

Evidence for an A2 adenosine receptor in human coronary arteries.

The present study was an attempt to characterize the type of adenosine receptor in human coronary arteries obtained from organ donors with the use of adenosine analogs. Prostaglandin F2 alpha (10(-6) M) produced tonic contractions followed by phasic contractions and diltiazem (10(-6) M) pretreatment changed the phasic contractions to tonic contractions. Adenosine and its analogs (5'-N-ethyl-carboxamide adenosine, NECA and N6-L-phenyl-isopropyl adenosine, L-PIA), produced concentration-dependent relaxations of the tonic contractions and the order of potency was found to be: NECA greater than L-PIA greater than adenosine. 8-Phenyltheophylline (5 X 10(-6) M) antagonized the relaxations produced by adenosine and its analogs. The data suggest the existence of A2 adenosine receptor in human coronary arteries.