Monoamine oxidase A inhibitor-near-infrared dye conjugate reduces prostate tumor growth

Development of anti-cancer agents with high tumor-targeting specificity and efficacy is critical for modern multidisciplinary cancer research. Monoamine oxidase A (MAOA), a mitochondria-bound enzyme, degrades monoamine neurotransmitters and dietary monoamines. Recent evidence suggests a correlation between increased MAOA expression and prostate cancer (PCa) progression with poor outcomes for patients. MAOA induces epithelial-mesenchymal transition (EMT) and augments hypoxic effects by producing excess reactive oxygen species. Thus, development of MAOA inhibitors which selectively target tumors becomes an important goal in cancer pharmacology. Here we describe the design, synthesis, and in vitro and in vivo evaluation of NMI, a conjugate that combines a near-infrared dye for tumor targeting with the moiety derived from the MAOA inhibitor clorgyline. NMI inhibits MAOA with low micromolar IC50, suppresses PCa cell proliferation and colony formation, and reduces migration and invasion. In mouse PCa xenografts, NMI targets tumors with no detectable accumulation in normal tissues, providing effective reduction of the tumor burden. Analysis of tumor specimens shows reduction in Ki-67(+) and CD31(+) cells, suggesting a decrease of cell proliferation and angiogenesis and an increase in M30(+) cells, indicating increased apoptosis. Gene expression profiles of tumors treated with NMI demonstrate reduced expression of oncogenes FOS, JUN, NFKB, and MYC and cell cycle regulators CCND1, CCNE1, and CDK4/6, along with increases in the levels of tumor suppressor gene TP53, cell cycle inhibitors CDKN1A and CDKN2A, and MAOA-downstream genes that promote EMT, tumor hypoxia, cancer cell migration, and invasion. These data suggest that NMI exerts its effect through tumor-targeted delivery of a MAOA-inactivating group, making NMI a valuable anti-tumor agent.

A selective mitochondrial-targeted chlorambucil with remarkable cytotoxicity in breast and pancreatic cancers

Nitrogen mustards, widely used as chemotherapeutics, have limited safety and efficacy. Mitochondria lack a functional nucleotide excision repair mechanism to repair DNA adducts and are sensitive to alkylating agents. Importantly, cancer cells have higher intrinsic mitochondrial membrane potential (Δψmt) than normal cells. Therefore, selectively targeting nitrogen mustards to cancer cell mitochondria based on Δψmt could overcome those limitations. Herein, we describe the design, synthesis, and evaluation of Mito-Chlor, a triphenylphosphonium derivative of the nitrogen mustard chlorambucil. We show that Mito-Chlor localizes to cancer cell mitochondria where it acts on mtDNA to arrest cell cycle and induce cell death, resulting in a 80-fold enhancement of cell kill in a panel of breast and pancreatic cancer cell lines that are insensitive to the parent drug. Significantly, Mito-Chlor delayed tumor progression in a mouse xenograft model of human pancreatic cancer. This is a first example of repurposing chlorambucil, a drug not used in breast and pancreatic cancer treatment, as a novel drug candidate for these diseases.

Reduction in intraoperative bacterial contamination of peripheral intravenous tubing through the use of a passive catheter care system

BACKGROUND

Bacterial contamination of intravascular devices has been associated with increased morbidity and mortality in various hospital settings, including the perioperative environment. Catheter hub disinfection has been shown in an ex vivo model to attenuate intraoperative injection of bacterial organisms originating from the anesthesia provider's hands, providing the impetus for improvement in intraoperative disinfection techniques and compliance. In the current study, we investigated the clinical effectiveness of a new, passive catheter care station in reducing the incidence of bacterial contamination of open lumen patient IV stopcock sets. The secondary aim was to evaluate the impact of this novel intervention on the combined incidence of 30-day postoperative infections and IV catheter-associated phlebitis.

METHODS

Five hundred ninety-four operating room environments were randomized by a computer-generated list to receive either a novel catheter care bundle (HubScrub and DOCit) or standard caps in conjunction with a sterile, conventional open lumen 3-way stopcock set (24 inch with 3-gang 4-way and T-Connector). Patients underwent general anesthesia according to usual practice and were followed prospectively for 30 postoperative days to identify the development of health care-associated infections (HCAIs) and/or phlebitis. The primary outcome was intraoperative bacterial contamination of the primary stopcock set used by the anesthesia provider(s). The secondary outcome was the combined incidence of 30-day postoperative infections and phlebitis.

RESULTS

Five hundred seventy-two operating rooms were included in the final analysis. Study groups were comparable with no significant differences in patient, provider, anesthetic, or procedural characteristics. The catheter care station reduced the incidence of primary stopcock lumen contamination compared with standard caps (odds ratio [OR] 0.79, 95% confidence interval [CI] 0.63-0.98, P = 0.034) and was associated with a reduction in the combined incidence of HCAIs and IV catheter-associated phlebitis with and without adjustment for patient and procedural covariates (OR(adjusted) 0.589, 95% CI 0.353-0.984, P = 0.040). The risk-adjusted number needed to treat to eliminate 1 case of lumen contamination was 9 (95% CI 3.4-13.5) patients, whereas the risk-adjusted number needed to treat to eliminate 1 case of HCAI/catheter-associated phlebitis was 17 (95% CI 11.8-17.9) patients.

CONCLUSION

Intraoperative use of a passive catheter care station significantly reduced open lumen bacterial contamination and the combined incidence of 30-day postoperative infections and phlebitis.

Prevention of intravenous bacterial injection from health care provider hands: the importance of catheter design and handling

BACKGROUND

Device-related bloodstream infections are associated with a significant increase in patient morbidity and mortality in multiple health care settings. Recently, intraoperative bacterial contamination of conventional open-lumen 3-way stopcock sets has been shown to be associated with increased patient mortality. Intraoperative use of disinfectable, needleless closed catheter devices (DNCCs) may reduce the risk of bacterial injection as compared to conventional open-lumen devices due to an intrinsic barrier to bacterial entry associated with valve design and/or the capacity for surface disinfection. However, the relative benefit of DNCC valve design (intrinsic barrier capacity) as compared to surface disinfection in attenuation of bacterial injection in the clinical environment is untested and entirely unknown. The primary aim of the current study was to investigate the relative efficacy of a novel disinfectable stopcock, the Ultraport zero, with and without disinfection in attenuating intraoperative injection of potential bacterial pathogens as compared to a conventional open-lumen stopcock intravascular device. The secondary aims were to identify risk factors for bacterial injection and to estimate the quantity of bacterial organisms injected during catheter handling.

METHODS

Four hundred sixty-eight operating room environments were randomized by a computer generated list to 1 of 3 device-injection schemes: (1) injection of the Ultraport zero stopcock with hub disinfection before injection, (2) injection of the Ultraport zero stopcock without prior hub disinfection, and (3) injection of the conventional open-lumen stopcock closed with sterile caps according to usual practice. After induction of general anesthesia, the primary anesthesia provider caring for patients in each operating room environment was asked to perform a series of 5 injections of sterile saline through the assigned device into an ex vivo catheter system. The primary outcome was the incidence of bacterial contamination of the injected fluid column (effluent). Risk factors for effluent contamination were identified in univariate analysis, and a controlled laboratory experiment was used to generate an estimate of the bacterial load injected for contaminated effluent samples.

RESULTS

The incidence of effluent bacterial contamination was 0% (0/152) for the Ultraport zero stopcock with hub disinfection before injection, 4% (7/162) for the Ultraport zero stopcock without hub disinfection before injection, and 3.2% (5/154) for the conventional open-lumen stopcock. The Ultraport zero stopcock with hub disinfection before injection was associated with a significant reduction in the risk of bacterial injection as compared to the conventional open-lumen stopcock (RR = 8.15 × 10(-8), 95% CI, 3.39 × 10(-8) to 1.96 × 10(-7), P = <0.001), with an absolute risk reduction of 3.2% (95% CI, 0.5% to 7.4%). Provider glove use was a risk factor for effluent contamination (RR = 10.48, 95% CI, 3.16 to 34.80, P < 0.001). The estimated quantity of bacteria injected reached a clinically significant threshold of 50,000 colony-forming units per each injection series.

CONCLUSIONS

The Ultraport zero stopcock with hub disinfection before injection was associated with a significant reduction in the risk of inadvertent bacterial injection as compared to the conventional open-lumen stopcock. Future studies should examine strategies designed to facilitate health care provider DNCC hub disinfection and proper device handling.

Use of a nerve stimulator does not improve the efficacy of ultrasound-guided supraclavicular nerve blocks

OBJECTIVE

To evaluate the efficacy of nerve stimulation as an adjunct to ultrasound-guided supraclavicular nerve blocks.

DESIGN

Prospective database review.

SETTING

Tertiary-care medical center.

MEASUREMENTS

The records of 94 consecutive adult patients requiring surgery below the elbow and consenting to receive regional anesthesia were studied. The focus of this study was on supraclavicular nerve block using ultrasound guidance for nerve identification and needle localization. A nerve stimulator with a motor response lower than 0.5 mA was used for confirmation of findings. An ultrasound image was considered adequate if two trunks of the brachial plexus were visualized and if the needle was completely seen on the long axis. A successful block was defined as one that sufficed as the sole anesthetic without conversion to general anesthesia. Motor and sensory examination findings on the upper extremity were also evaluated.

RESULTS

74 patients had an adequate ultrasound image. Of the 64 patients with a positive motor response, 88% had a successful block, as compared with 90% of the 10 patients without a motor response (relative risk, 1.09; 95% confidence interval, 0.79-1.51; P = 0.52). Neither multivariate correction for baseline characteristics nor inclusion of the 20 patients with inadequate ultrasound images changed the results.

CONCLUSION

For adequately imaged ultrasound-guided supraclavicular nerve blocks, a positive motor response to nerve stimulation does not increase the success rate of the block. In addition, the high false-negative rate suggests that these blocks are usually effective, even in the absence of a motor response. Nerve stimulation as an adjunct to ultrasound guidance may have a limited role.

Characterizing Novice Behavior Associated With Learning Ultrasound-Guided Peripheral Regional Anesthesia

BACKGROUND AND OBJECTIVES

Ultrasound-guided regional anesthesia is a rapidly growing field. There exists little information regarding the competencies involved with such a practice. The objective of this exploratory study was to characterize the behavior of novices as they undertook the challenges of learning a new technique. In addition to assessing for both committed errors and accuracy, we aimed to identify previously unrecognized quality-compromising behaviors that could help structure effective training interventions.

METHODS

By using detailed video analyses, the performances of 6 anesthesia residents were evaluated while on a dedicated 1-month rotation in ultrasound-guided regional anesthesia. From these video reviews, we assessed accuracy, errors committed, performance times, and searched for previously unrecognized quality-compromising behaviors.

RESULTS

A total of 520 nerve blocks were videotaped and reviewed. All residents performed at least 66 nerve blocks, with an overall success rate of 93.6% and 4 complications. Both speed and accuracy improved throughout the rotation. There were a total of 398 errors committed, with the 2 most common errors consisting of the failure to visualize the needle before advancement and unintentional probe movement. Five quality-compromising patterns of behavior were identified: (1) failure to recognize the maldistribution of local anesthesia, (2) failure to recognize an intramuscular location of the needle tip before injection, (3) fatigue, (4) failure to correctly correlate the sidedness of the patient with the sidedness of the ultrasound image, and (5) poor choice of needle-insertion site and angle with respect to the probe preventing accurate needle visualization.

CONCLUSIONS

Based on the analysis of the committed errors and the identification of quality-compromising behaviors, we are able to recommend important targets for learning in future training and simulation programs.

An abnormal clinical course of an ultrasound-guided supraclavicular brachial plexus block using 0.375% bupivacaine

We report on the case of a reappearance of a supraclavicular nerve block after the apparent initiation of its resolution in a 21-year-old athlete undergoing repair of a valgus impaction syndrome of his right elbow. The patient's anesthetic management consisted of a supraclavicular nerve block and general anesthesia. The patient was discharged home with an apparent resolving nerve block. He returned to the hospital urgently when, at 7 hours after blockade, he lost all motor-sensory function in his arm. His workup ultimately yielded negative results, and the block resolved at 23 hours. In addition to documenting an abnormal course of a supraclavicular block, this case report questions the appropriateness of placing long-acting nerve blocks in outpatients.

Ultrasound guidance improves the success rate of a perivascular axillary plexus block

BACKGROUND

Traditional approaches to performing brachial plexus blocks via the axillary approach have varying success rates. The main objective of this study was to evaluate if a specific technique of ultrasound guidance could improve the success of axillary blocks in comparison to a two injection transarterial technique.

METHODS

Fifty-six ASA physical status I-III patients presenting for elective hand surgery were prospectively randomized to receive an axillary block performed by either a transarterial technique (Group TA) or an ultrasound-guided perivascular approach (Group US). Both groups received a total of 30 ml of 1.5% lidocaine (225 mg) with 5 microg/ml epinephrine. Patients were then evaluated for block onset in specific nerve distributions and whether or not the block acted as a surgical anesthetic.

RESULTS

Group TA sustained more failures defined as conversion to general anesthesia or the inability to localize the artery [Group TA eight patients (29%) vs. Group US in which 0 patients required conversion to general anesthesia (0%) P < 0.01]. Group US demonstrated a reduction in performance times vs. Group TA (7.9 +/- 3.9 min vs. 11.1 +/- 5.7 min, P < 0.05). By 30 min post-injection, there were no significant differences between groups TA and US in terms of the proportion of patients demonstrating a complete motor or sensory loss.

CONCLUSION

Ultrasonographic guidance improves the overall success rate of axillary blocks in comparison to a transarterial technique.

Enantioselective Total Synthesis of Avrainvillamide and the Stephacidins

In this article, full details regarding our total synthesis of avrainvillamide and the stephacidins are presented. After an introduction and summary of prior synthetic studies in this family of structurally complex anticancer natural products, the evolution of a final synthetic approach is described. Thus, a thorough description of three separate model studies is provided for construction of the characteristic bicyclo[2.2.2]diazaoctane ring system common to these alkaloids. The first and second approaches sought to build the core using formal Diels-Alder and vinyl radical pathways, respectively. Although these strategies failed in their primary objective, they fostered the development of a new and mechanistically intriguing method for the synthesis of indolic enamides such as those found in numerous bioactive natural products. The scope and generality of this simple method for the direct dehydrogenation of tryptophan derivatives is described. Finally, details of a third and successful route to the core of these alkaloids are described which features oxidative C-C bond formation. Specifically, the first heterocoupling of two different types of carbonyl species (ester and amide) is accomplished in good yield, on a preparative scale, and with complete stereocontrol. The information gained in these model studies enabled an enantioselective total synthesis of stephacidin A. The absolute configuration of these alkaloids was firmly established in collaboration with Professor William Fenical. A full account of our successful efforts to convert stephacidin A into stephacidin B via avrainvillamide is presented. Finally, the first analogues of these natural products have been prepared and evaluated for anticancer activity.

The learning curve associated with a simulated ultrasound-guided interventional task by inexperienced anesthesia residents

BACKGROUND AND OBJECTIVE

Ultrasound has become an increasingly popular modality in facilitating the performance of peripheral nerve blocks. There exists no literature that examines the learning curve of the ultrasound novice. In this prospective series, we evaluated the learning curve of inexperienced anesthesia residents in performing a simulated ultrasound-guided interventional procedure. In doing so, we hoped to identify reproducible patterns of human errors, which could potentially aid in the prevention of real-life iatrogenic injuries.

METHODS

Ten subjects were prospectively enrolled. After a brief introduction to the ultrasound system, the subjects were asked to perform 6 sequential trials of a simulated breast cyst aspiration. For the first 3 trials, each subject attempted to place a 22-gauge b-bevel needle into any aspect of an olive buried inside the turkey breast. After completion of these 3 trials, the subjects were asked to place the needle into the exact midpoint of the olive wall closest to the transducer. Trials were videotaped and analyzed for task performance in terms of speed and accuracy.

RESULTS

All subjects successfully completed the 6 interventional trials. The mean time to perform the task was reduced by 38% and 48%, respectively, for the second and third trials. A composite score of accuracy showed an improvement of 36% and 59%, respectively, for the second and third trials. The most common committed error, which occurred in 7 of 10 subjects, was the failure to accurately image the needle while advancing. This resulted in excessive depth of penetration and inadvertent transfixation of the olive in 5 of these subjects.

CONCLUSIONS

Anesthesiology residents, with little or no ultrasound experience, can rapidly learn and improve their speed and accuracy in performing a simulated interventional ultrasound procedure. A concerning novice pattern was identified where the subjects advanced the needle even though it was not appropriately visualized in the ultrasound beam. This resulted in needle placement error, which could cause iatrogenic injury in the clinical setting.

A single injection ultrasound-assisted femoral nerve block provides side effect-sparing analgesia when compared with intrathecal morphine in patients undergoing total knee arthroplasty

Postoperative pain after total knee arthroplasty (TKA) is severe, and achieving adequate analgesia remains a clinical challenge. We tested the hypothesis that, in patients having unilateral TKA under intrathecal (IT) anesthesia, the addition of a femoral nerve block would provide superior analgesia when compared with IT morphine and demonstrate fewer adverse side effects. In a single-blinded and controlled trial, 41 ASA I-III patients undergoing unilateral TKA were randomized into 2 groups. Both groups received 15 mg of IT hyperbaric bupivacaine for the surgical anesthetic. Group ITM received 250 microg of IT morphine and group FNB received an ultrasound-assisted femoral nerve block with 40 mL of 0.5% ropivacaine, 5 microg/mL of epinephrine, and 75 microg of clonidine. At 1, 2, 4, 6, 12, and 24 h postoperatively, we measured visual analog scales for pain, cumulative IV morphine consumption, hemodynamics, and side effects. There were no statistically significant differences in morphine consumption, pain at rest, or pain with movement. However, group FNB had fewer perioperative side effects including nausea, vomiting, and pruritus (P < 0.05 for each event). This corresponded to a decrease in patient satisfaction in group ITM, in which 20% of the patients rated their experience as "unsatisfactory" (P < 0.05). We conclude that, in comparison with IT morphine, a single injection femoral nerve block provides equivalent analgesia but with a significant reduction in side effects for patients having TKA under bupivacaine intrathecal anesthesia.

The use of magnetic resonance imaging to evaluate the accuracy of a handheld ultrasound machine in localizing the sciatic nerve in the popliteal fossa

BACKGROUND AND OBJECTIVE

Ultrasound has become an increasingly popular modality in facilitating the performance of peripheral nerve blocks. There is a paucity of data describing techniques of ultrasound-guided sciatic nerve blocks. By using magnetic resonance imaging (MRI) as a gold standard, the objective of this study was to describe the ability of a handheld ultrasound machine to accurately locate the sciatic nerve.

METHODS

Ten patients were prospectively enrolled and placed in the prone position. By using a 4- to 7-MHz ultrasound transducer, the sciatic nerve was visualized in short axis between 5 to 10 cm above the popliteal crease. The distance from the skin to the nerve was measured by ultrasound, and a MRI lucent marker was placed at this site. This process was repeated in one additional location. The patient was then placed supine in the MRI scanner and short-axis T1-weighted images were obtained. On the MRI image, we recreated the 2 lines extending down from the markers using the distances previously measured by ultrasound. The point of intersection of these 2 lines represents the ultrasound-determined location of the sciatic nerve, which was then compared with the midpoint of the nerve complex on MRI.

RESULTS

The sciatic nerve was easily visualized by ultrasound in all 10 patients. MRI showed the division of the sciatic nerve in 9 out of 10 patients. Ultrasound was able to confirm this division in 7 patients. The mean distance between the MRI and ultrasound midpoint location of the sciatic nerve was 2.9 +/- 1.3 mm.

CONCLUSIONS

The data presented here suggest that the specific ultrasound machine evaluated in this study can accurately localize the sciatic nerve in the popliteal fossa.

OMNI scale perceived exertion at ventilatory breakpoint in children: response normalized

PURPOSE

The Children's OMNI Scale of Perceived Exertion was used to identify a response normalized rating of perceived exertion (RPE)-Overall, RPE-Legs, and RPE-Chest that corresponds to the ventilatory breakpoint (Vpt) in 8- to 12-yr-old female and male children.

METHODS

Subjects were a priori stratified into two fitness groups on the basis of peak oxygen uptake (VO2 peak): average (A) (41.0-49.0 mL x kg(-1) x min(-1); N = 24) and above average (AA) (50.0-58.0 mL x kg(-1) x min(-1); N = 24). Vpt was determined by a progressive cycle ergometer protocol to VO2 peak.

RESULTS

A gender effect was not observed for any descriptive or dependent variable. Mean VO2peak for the A group was 1.72 L x min(-1) and for the AA group 2.04 L x min(-1). Vpt corresponded to 64.0% VO2 peak for A and 74.0% VO2peak for AA. RPE-Overall (mean A and AA, 6.1), RPE-Legs (mean A and AA, 7.2), and RPE-Chest (mean A and AA, 4.5) did not differ between the fitness groups.

CONCLUSION

Findings indicated that undifferentiated and differentiated RPE-Vpt were similar between female and male children who varied in VO2peak and Vpt. A comparatively stable RPE-Vpt for 8- to 12-yr-old children that vary in VO2peak and Vpt indicates a group normalized perceptual response.

Children's OMNI scale of perceived exertion: mixed gender and race validation

PURPOSE

The newly developed Children's OMNI Scale of Perceived Exertion (category range: 0 to 10) was validated using separate cohorts of female and male, African American and white subjects. Each of the four cohorts contained 20 clinically normal, nonobese children, 8-12 yr of age.

METHODS

A cross-sectional, perceptual estimation paradigm using a single multi-stage cycle ergometer test protocol was used. Oxygen uptake (VO2; mL x min(-1)), heart rate (HR; beats x min(-1)) and ratings of perceived exertion for the overall body (RPE-Overall), legs (RPE-Legs), and chest (RPE-Chest) were determined at the end of each continuously administered 3-min power output (PO) (i.e., 25, 50, 75, and 100 W) test stage.

RESULTS

The range of responses over the four POs for all cohorts was VO2: 290.8 to 1204.0 mL x min(-1); HR: 89.2 to 164.4 beats x min(-1); and RPE-Overall, RPE-Legs, and RPE-Chest: 0.85 to 9.1. First-order correlation and linear regression analyses were performed for each cohort separately and the total sample using a repeated measures paradigm over the four POs. For all correlation/regression paradigms RPE-Overall, RPE-Legs, and RPE-Chest distributed as a positive linear function of both VO2 and HR; r = 0.85 to 0.94; P < 0.01. Differences between RPE-Overall, RPE-Legs, and RPE-Chest were examined with ANOVA for the repeated measures paradigm. RPE-Legs was higher (P < 0.01) than RPE-Chest and RPE-Overall at 25, 50, 75, and 100 W. RPE-Chest did not differ from RPE-Overall at 25 and 50 W but was lower (P < 0.01) than RPE-Overall at 75 and 100 W.

CONCLUSION

The psycho-physiological responses provide validity evidence for use of the Children's OMNI Scale over a wide range of dynamic exercise intensities.

Voluntary movement strategies of individuals with unilateral peripheral vestibular hypofunction

This study compared voluntary movement strategies of patients with unilateral peripheral vestibular hypofunction with those of age-matched healthy control subjects. All subjects performed three voluntary movement tasks with their dominant upper extremity: a forward flexion arm movement through 90 degrees, a reach to an overhead target, and a reach to a side target. Subjects performed the movement tasks sitting and standing (Body Position), and under precued and choice reaction time (RT) conditions (Task Certainty). Measures of motor planning and movement execution included RT and movement time (MT), respectively. Statistical analysis included separate Group x Task Certainty x Body Position ANOVA calculations for each task. Across tasks, results suggested no between group differences for RT. A Task Certainty main effect for the side and overhead tasks indicated that the choice RT situation resulted in longer RTs as compared to the precued RT condition. Movement time differed between the two groups. Across all three voluntary movement tasks, vestibular impaired subjects moved more slowly than control subjects. Providing vestibular subjects with a precue did not bring MT performance to the level of controls. Body position influenced MT for the side task only. Across both groups of subjects, MT for the side task was longer when performed in the standing position. The results of this study suggest that individuals with unilateral peripheral vestibular hypofunction initiate voluntary movement responses with similar timing as control subjects, but require more time to complete the movement. Vestibular rehabilitation should include goal-directed movement and should address issues of movement speed.

The effects of halothane on abnormal automaticity in canine cardiac Purkinje fibers

Abnormal automaticity is the spontaneous beating of cardiac cells with abnormally depolarized resting membrane potentials. The effects of halothane on cardiac arrhythmias caused by abnormal automaticity are controversial, with either antiarrhythmic effects or enhancement of abnormal automaticity reported by different authors. The goal of the present investigation was to clarify the effects of halothane on abnormal automaticity induced by superfusing excised canine Purkinje fibers (PF) with barium chloride. Intracellular microelectrodes recorded action potentials from fibers superfused with buffer solution in a tissue bath. Barium chloride 0.25 mM reduced maximal diastolic potential from -82.1 +/- 5.6 mV to -67.4 +/- 9.4 mV (mean +/- SD, P < 0.05). Fibers developed abnormal automatic rhythms at a rate of 47.1 +/- 5.9 bpm. Halothane, 0.5%-4%, was added to the superfusate. Halothane reduced the rate of firing in a dose-dependent manner, so that abnormal automaticity was abolished by 4% halothane and reduced by lesser concentrations. Serendipitously, during barium superfusion, two additional fibers developed early afterdepolarizations, a cause of triggered arrhythmias in patients with long Q-T syndrome. Halothane abolished early afterdepolarizations in each. In this model of barium toxicity in excised canine PF, halothane antagonized both abnormal automaticity and early afterdepolarizations.

IMPLICATIONS

Life-threatening cardiac arrhythmias may occur during anesthesia. An arrhythmia called abnormal automaticity occurs after heart attacks and can be mimicked by adding barium to small segments of heart tissue. Halothane abolished abnormal automaticity in these tissues, which suggests that it or similar agents may benefit patients prone to developing such abnormal rhythms during surgery.

Electrophysiological mechanisms for ventricular arrhythmias in patients with myocardial ischemia: anesthesiologic considerations, Pt II

This is the second half of a two-part review article that discusses ventricular tachyarrhythmias, either induced by acute ischemia or consequent to chronic myocardial ischemia, and their anesthestic implications. The first half of the article was published in the June 1997 Issue of The Journal.

MRI of pituitary abscess: two cases and review of the literature

Pituitary abscesses, rare lesions, may be divided into primary and secondary types. Primary pituitary abscesses occur within a previously healthy gland, while secondary abscesses arise within an existing lesion, such as an adenoma, craniopharyngioma, or Rathke's cleft cyst. Secondary abscesses share radiologic characteristics with the lesions from which they arise. There has been no review of the MRI characteristics of primary pituitary abscesses. We report two cases and review the literature. The typical primary pituitary abscess gives the same or slightly lower signal than brain on T1-weighted images, and could be mistaken for a solid mass or presumed to represent a pituitary adenoma. Contrast-enhanced images are useful, demonstrating absence of central enhancement, suggesting a fluid or necrotic center. In one of our cases, meningeal enhancement was obvious; this has not been reported previously and may be diagnostic, when associated with a rim-enhancing pituitary mass.

Presence of functional NMDA receptors in a human neuroblastoma cell line

Data are presented that provide convincing evidence for the expression of structurally normal and functional NMDA receptors by acetylcholine-producing human LA-N-2 neuroblastoma cells in culture. Reverse transcription and polymerase chain reaction (RT-PCR), followed by cloning and DNA sequencing, revealed the presence in these cells of mRNA representing the key subunit, NMDAR1, of the receptor. This mRNA was further demonstrated by Northern analysis to be the same size as that described for human neurons. The neutral red cytotoxicity assay was utilized to examine the influence on these neuroblastoma cells of a 48-h incubation with either L-glutamic acid or the specific NMDA agonist N-phthalamoyl-L-glutamic acid (NPG). Cell cytotoxicity was shown by this assay to be increased through incubation with glutamate at 1 and 10 mM by 27 and 37%, and through incubation with NPG at 0.1 and 1 mM by 28 and 46%. A possible mechanism of these toxic effects was further evaluated using the whole-cell configuration of the patch-clamp technique and the specific NMDA agonists (+/-)1-aminocyclobutane-cis-1,3-dicarboxylic acid (ACDA) and NPG. Using this procedure, a voltage-dependent tetrodotoxin-sensitive inward sodium current was found to be increased (x 1.5) by L-glutamic acid and by both NMDA agonists in the presence of glycine. Another voltage-gated inward current, probably carried by calcium ions, was increased three- to fourfold. Hence, these glutamate activities observed in human LA-N-2 neuroblastoma cells appear to occur through the activation of functional NMDA receptors in much the same way as reported for neurons, and both glutamate and NMDA agonists can be toxic to these neuroblastoma cells. Our findings, therefore, suggest this cell line will provide a model suitable for investigating the mechanisms of NMDA-related long-term potentiation (LTP) in neurons and of the NMDA-related neurotoxic effects of glutamate in disease states that involve a reduction in cholinergic function.

Ionic signals in T47D human breast cancer cells

Increasing evidence that ion channels play a key role in the modulation of cellular mitogenesis led us to investigate the membranes of T47D human breast cancer cells to identify the ion currents present. We report here the results of voltage-clamp studies in the whole-cell configuration on isolated, non-synchronized single cells obtained from a ductal breast carcinoma. In these studies we identified an outward rectifying potassium current and a chloride current. The potassium current activated at potentials more positive than -40 mV, reached an average value of 1.4 nA, and did not inactivate with time. This current was sensitive to block by extracellular tetraethylammonium chloride (TEA, IC50 = 1 micro M), was insensitive to charybdotoxin (CTX, IC50 = 7.8 micro M), and was not diminished by repetitive pulses separated by 1 s. Rapid voltage-dependent inactivation of the current was demonstrated by tail current analysis. The current appeared calcium-insensitive. Application of hyperpolarizing pulses did not elicit an inward potassium rectifier current. Treatment with tetrodotoxin did not reveal the presence of an inward sodium current. The potassium current was increased by the presence of aspartate in place of chloride and in the presence of the chloride channel blocker 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS). We conclude that currents present in T47D breast cancer cells include a chloride current and a voltage-gated potassium outward rectifier. We suggest that the potassium current, either alone or in conjunction with potassium currents reported in different human breast cancer cell lines by others, may play a role in the modulation of the cell cycle.

Prenatal exposure to alcohol and marijuana: effects on motor development of preschool children

Gross motor development of preschool children prenatally exposed to alcohol and marijuana was assessed as part of a longitudinal study. Most mothers in the study were light to moderate users and discontinued or decreased use of alcohol and marijuana after the first trimester of pregnancy. The women were of lower socioeconomic status, half of the sample was African-American, and most were single. Gross motor development was evaluated with balance and ball-handling items at 3 years. Balance items included walking on a line, walking on a balance beam, standing on one foot, standing on tiptoes, and stair climbing and descent. Ball-handling items included catching, throwing, and kicking a ball. Refusal to perform items was also recorded. Prenatal alcohol and marijuana exposure did not negatively affect gross motor development. The composite score on the Stanford-Binet Intelligence Scale, age at assessment, gender, and examiner were significant predictors of gross motor performance and of refusal to participate in the balance items. The ponderal index, number of siblings, current income, examiner, current maternal use of tranquilizers, and first trimester exposure to amphetamines were also significant predictors of balance skills. Gender and number of hospitalizations predicted refusal to participate in balance items, whereas hearing and vision problems predicted refusal on ball-handling items. The components of timing, speed, and fine motor control have not been addressed in this study, and therefore it is premature to conclude that there is no impact of prenatal substance use on motor development.

Mercury suppression of a potassium current in human B lymphocytes

Mercury is a recognized environmental toxin. Several organ systems are targeted by this substance and impairment of immune function is known to result from exposure to mercury. Using the patch clamp technique in the whole cell configuration on resting human B lymphocytes we have identified an outward potassium current and studied the effects of mercury on this current. We present data that demonstrate: (i) the absence of inward currents; (ii) a time and voltage dependent outward current with a threshold of -40 mV and reversal potential near EK+; (iii) blocking of this current by TEA (tetraethylammonium chloride) in a dose dependent manner; (iv) a slow time course for recovery from inactivation of this outwardly rectifying K+ current and, (v) the diminution and final block of this potassium current by mercury. These data supplement the findings from our laboratories that demonstrate inhibitory effects on B cell activation by mercury. We propose that the movement of potassium ions across the B cell membrane, an event presumed to be one of the first signals in the mitogenic process, is a target of mercury toxicity.

Effects of isoflurane on ouabain toxicity in canine Purkinje fibers. Comparison with halothane

BACKGROUND

Although halothane reduces digitalis toxicity, other anesthetics, notably cyclopropane, increase toxicity. This study determined the effects of isoflurane on digitalis toxicity in isolated cardiac tissue and compared these effects with those of halothane.

METHODS

Standard microelectrode techniques were used to record action potentials from excised canine Purkinje fibers. Fibers were paced at cycle lengths between 1,000 and 250 ms for 20 beats to induce delayed afterdepolarizations, which are membrane potential oscillations indicative of intracellular Na+ and Ca2+ overload, produced in these experiments by digitalis toxicity. The digitalis glycoside ouabain, 2 x 10(-7) M, was added to the Tyrode's solution superfusate to induce delayed after-depolarizations. Action potential variables and the coupling interval and amplitude of afterdepolarizations were then measured. Isoflurane (0.5%, 1%, or 2%) was added with a calibrated vaporizer (n = 8). In a second set of experiments (n = 10), isoflurane 1.25% or halothane 0.75% was added to the superfusate. After measurements had been made, the other agent was substituted.

RESULTS

Ouabain produced primary and secondary delayed afterdepolarizations, which were reduced in amplitude by isoflurane in a dose-related manner (P = 0.0002). Action potential duration to 90% repolarization was shortened by ouabain (P = 0.009) and remained shortened during isoflurane administration. Action potential duration to 50% repolarization was shortened by isoflurane 2%. Halothane and isoflurane were equally effective in reducing the amplitude of delayed afterdepolarizations (both P = 0.0002). In three fibers, triggered extrasystoles appeared. Halothane and isoflurane each abolished extrasystoles. In two fibers, sustained triggered activity appeared. Isoflurane abolished the arrhythmia in each fiber.

CONCLUSIONS

Isoflurane and halothane are equally effective in reducing delayed afterdepolarizations induced by ouabain toxicity.

Effect of halothane on in vivo and in vitro cardiotoxicity of an aminocardenolide

Halothane opposes cardiotoxicity of neutral-sugar digitalis compounds in intact animals, presumably by depressing a sympathetic component of arrhythmogenesis. However, halothane also produces a dose-related reduction in arrhythmogenicity of ouabain in isolated canine Purkinje fibers, suggesting that the anesthetic may oppose direct mechanisms of cardiotoxicity as well. The present study examined in vivo and in vitro the effect of halothane on the arrhythmogenicity of ASI-222 (3-beta-O[4-amino-4-6-dideoxy-beta-D-galactopyranosyl] digitoxigen in HCl), a highly polar aminocardenolide with no sympathetic component to cardiotoxicity. For in vivo studies, ASI-222 was infused at a rate of 1 microgram/kg/min until appearance of third-degree atrioventricular (AV) block or sustained ventricular arrhythmias in 5 conscious (control) and 6 halothane-anesthetized (1.4% end-tidal) dogs. For in vitro studies, standard microelectrode techniques were used to measure action potentials (AP) in seven excised canine Purkinje fibers superfused with oxygenated Krebs-Henseleit buffer. AP were recorded during control superfusion, after induction of toxicity with 10(-7) M ASI-222, and during exposure to 0.5, 1.0, and 2.0% halothane. Purkinje fibers were paced at 500-ms cycle lengths (CL) for 20 beats, and the amplitude of delayed afterdepolarizations (DAD) were recorded. Pacing at 250 ms CL was used to trigger ectopy. In vivo studies showed no difference in the cardiotoxic dose of ASI-222 between control dogs and those anesthetized with 1.4% halothane. However, in 4 of 6 anesthetized dogs, acutely increasing the inspired halothane concentration suppressed arrhythmias once end-tidal concentration were >2.2%.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of cadmium on potassium currents in activated B lymphocytes

We have applied the patch clamp technique in the whole-cell configuration to study whole-cell currents in B lymphocytes under three conditions: (i) resting; (ii) interleukin-4 (IL-4)-treated; and (iii) IL-4 plus cadmium-treated murine B lymphocytes. Through these experiments we have: (i) confirmed our earlier findings and the observation of others that resting B cells express only outward currents; (ii) confirmed the presence of an inwardly rectifying K+ current elicited by treatment with the lymphokine IL-4 that was revealed in our previous study on single channel currents; (iii) demonstrated that both inward and outward rectifying K+ currents in IL-4-treated B cells are dramatically reduced by exposure to 20 microM cadmium; and (iv) determined that the activation curve of the IL-4-induced inward rectifier is shifted to more negative voltages by cadmium. We propose that one of the mechanisms by which cadmium can mediate toxicity in activated B lymphocytes is through the suppression and modulation of potassium currents, effects that may alter the timing of entry into the cell cycle.

Effects of halothane and quinidine on intracardiac conduction and QTc interval in pentobarbital-anesthetized dogs

To confirm in vitro data that halothane and quinidine depressed cardiac conduction and prolonged action potential (AP) duration, the electrocardiogram and His bundle electrogram were recorded in dogs during basal pentobarbital anesthesia, after 1% halothane or quinidine (2.38 +/- 0.22 micrograms/mL serum concentration [mean +/- SEM]), or both. Purkinje fibers from a second dog were superfused with blood from the intact (support) dog, and APs were recorded. In the intact dogs, 1% halothane caused no changes in the electrocardiogram or His bundle electrogram. Quinidine prolonged QRS duration, QT interval, and rate-corrected QT (P < 0.05). Ventricular conduction (HS interval) slowed, and atrial effective refractory period increased (P < 0.05). Quinidine combined with halothane widened QRS, QT, and rate-corrected QT, prolonged the HS interval, and increased the vulnerability of the atrioventricular node to conduction block. Three of 20 dogs developed torsades de pointes-type ventricular tachycardia during simultaneous quinidine and halothane administration. In cross-superfused Purkinje fibers, the AP duration to 50% repolarization was shortened, and conduction time was prolonged by 1% halothane (both P < 0.05). Quinidine decreased AP amplitude, prolonged AP duration to 90% repolarization, and slowed conduction (P < 0.05). Quinidine combined with halothane decreased AP amplitude, and prolonged both AP duration to 90% repolarization and conduction (P < 0.05). When 1% halothane and therapeutic concentrations of quinidine are administered in dogs, depressed conduction and an acquired long QT syndrome with malignant ventricular arrhythmias may develop.

The effects of halothane on ventricular tachycardia in intact dogs

Halothane has either proarrhythmic or antiarrhythmic effects in a variety of clinical circumstances. This investigation tested the hypothesis that halothane would display different effects on ventricular tachycardia (VT) produced by different electrophysiologic mechanisms in intact dogs. Four models of VT produced by abnormal automaticity, reentry, delayed-afterdepolarization-induced triggered activity, and early-afterdepolarization-induced triggered automaticity (groups 1-4, respectively) were studied. In groups 1 and 2, the left anterior descending coronary artery (LAD) was ligated. In group 1 (n = 5), 24 h after LAD ligation and infarction, all dogs demonstrated incessant VT with 94.7 +/- 2.3% of beats of ventricular origin. This ectopy presumably was due to abnormal automaticity. Halothane reduced the frequency of ventricular ectopy until at 2% halothane only 34.8 +/- 15% of beats were of ventricular origin. One week after LAD ligation, programmed stimulation produced nonstimulated extrasystoles of presumably reentrant origin in six dogs. In three, halothane 1% abolished extrasystoles while increasing the ventricular refractory period by 23 +/- 3.8% (P less than 0.05). In the three other dogs, halothane had no effect (two dogs) or worsened the severity of VT (one dog), while the refractory period increased by 7.7% (P greater than 0.05). In group 3 dogs, ouabain was infused until VT secondary to triggered activity occurred. Halothane restored sinus rhythm in 4 of 5 dogs. Overall the percentage of sinus beats increased from 11.1 +/- 2.8 to 97.4 +/- 2.6% when halothane 2% was added during ouabain toxicity. Cesium chloride infusion increased the QT interval and produced complex VT in 5 dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

The electrophysiologic effects of amiodarone and halothane on canine Purkinje fibers

Amiodarone may cause serious complications in patients receiving general anesthetics. Potentially adverse electrophysiologic interactions between amiodarone and halothane were studied with the use of standard microelectrode techniques to record intracellular action potentials (APs) from excised canine Purkinje fibers. A second dog (support dog) was anesthetized and a femoral arteriovenous bypass circuit created in which arterial blood from the support dog superfused the Purkinje fiber in a tissue bath. The applicability of this model was established by first comparing the AP effects of halothane during blood perfusion with those in Tyrode's solution. Halothane reduced AP duration (APD; P less than 0.05) during Tyrode's solution superfusion and blood cross-perfusion. After the blood perfusion-Purkinje fiber model was validated, the interaction between halothane and amiodarone was studied using Purkinje fibers from dogs chronically treated with oral amiodarone, superfused with blood from chronically amiodarone-treated support dogs. Amiodarone reduced resting membrane potential and prolonged APD. Depression of AP amplitude and reduction of the maximum rate of increase of phase 0 of the AP (Vmax) by halothane (both P less than 0.05) suggested risk of conduction defects if halothane is administered to patients receiving chronic amiodarone therapy.

Halothane antagonizes ouabain toxicity in isolated canine Purkinje fibers

Standard intracellular microelectrode techniques were used to study the effects of halothane on ouabain-induced delayed after depolarizations (DAD) in canine Purkinje fibers. Free running Purkinje fibers were superfused with 2 X 10(-7)M ouabain in Krebs-Henseleit buffer for 30-50 min until DAD appeared. Purkinje fibers were then paced for 20 beats at cycle lengths between 1,000 ms and 200 ms, and the amplitude of the DAD and coupling interval between the DAD and last paced beat were determined. Halothane (0.5, 1, and 2%) was then administered and measurements repeated. Halothane produced dose-related decreases in DAD amplitude without changing DAD coupling interval. The ability of calcium to antagonize the effects of halothane was evaluated by doubling buffer calcium concentration to 5 mM in the presence of halothane 2%. Doubling buffer calcium concentration to 5 mM antagonized the reduction of DAD amplitude caused by halothane. In several preparations, dysrhythmias occurred during ouabain superfusion. Halothane reversibly terminated these arrhythmias. Halothane antagonizes DAD and dysrhythmias induced in vitro by ouabain toxicity. This effect, in part, may account for the apparent effectiveness of halothane against ouabain-induced dysrhythmias in vivo.

A comparison of the electrophysiologic effects of acute and chronic amiodarone administration on canine Purkinje fibers

The electrophysiologic effects of acutely and chronically administered amiodarone on canine Purkinje fibers were assessed using microelectrode techniques to record intracellular action potentials. Chronically treated dogs received amiodarone for 3 weeks (serum levels, 0.91 +/- 0.09 microgram/ml or 1.42 X 10(-6) M). Acute studies were performed using fibers from untreated dogs superfused for 1 h with 5 X 10(-5) M amiodarone (32 micrograms/ml) in Tyrode's solution (KCl = 4 mM). Acute superfusion shortened the action potential duration to 50 and 90% repolarization by 41 and 8%, respectively (p less than 0.01), and decreased Vmax of phase 0 from 418 +/- 20 to 309 +/- 23 V/s (p less than 0.01) (paced cycle length of 500 ms). Prominent use-dependent depression of Vmax was noted. Acute exposure of fibers from untreated dogs to blood from dogs chronically treated with amiodarone using the blood cross-perfusion technique decreased the action potential duration to 50% repolarization and Vmax, similar to acute exposure in Tyrode's solution. Blood cross-perfusion was used to study fibers from treated dogs superfused with blood from another amiodarone-treated dog. Chronic amiodarone prolonged the action potential duration to 90% repolarization by 13% (p less than 0.02) and did not change Vmax when compared to control studies using fibers obtained from untreated dogs superfused with blood from untreated dogs. Thus, the effects of acutely superfused amiodarone on action potentials of canine Purkinje fibers differ from the effects of chronically administered amiodarone.

Determination of the pulmonary capillary wedge position in patients with giant left atrial V waves

Thirteen patients with giant left atrial V waves during preoperative cardiac catheterization were admitted into the study group. While awake and breathing spontaneously, simultaneous recordings of electrocardiographic leads II and V5, radial arterial traces, and pulmonary arterial or pulmonary capillary wedge traces were obtained. Measurements were made on four consecutive cardiac cycles in the unwedged and wedged positions for the following intervals: Q wave to the radial arterial upstroke (220 +/- 20 milliseconds) and peak (360 +/- 10 milliseconds), Q wave to the pulmonary arterial upstroke (170 +/- 20 milliseconds) and peak (350 +/- 20 milliseconds), Q wave to the V wave upstroke (280 +/- 20 milliseconds) and peak (570 +/- 20 milliseconds), and QT interval (420 +/- 20 milliseconds). These findings indicate that the radial arterial and pulmonary arterial upstrokes and peaks occur nearly simultaneously. Upon wedging, the V wave upstroke occurs significantly later in the cardiac cycle (P less than .05) compared with the pulmonary arterial upstroke, and the V wave peak occurs significantly later compared with both the pulmonary arterial and the radial arterial peak (P less than .05). A rapid, simple beat-to-beat method for differentiating pulmonary arterial from pulmonary capillary wedge positions in the presence of giant left atrial V waves is the superimposition of the pulmonary arterial trace on the radial arterial trace. When a wedge position is attained, there is an immediate rightward shift in the upstroke and peak of the pulmonary arterial pressure trace, which can be easily identified by observing the relationship between the pulmonary arterial and systemic arterial traces.

Chronotropic response of an activity detecting pacemaker compared with the normal sinus node

We compared the rate responsiveness of an activity-detecting multiprogrammable, single chamber pacemaker (Medtronic Activitrax) to rate responsiveness of the normal sinus node. This pacemaker changes its basic pacing rate in response to physical activity. The rate responsiveness is programmable by selecting one of three activity thresholds, and one of 10 rate response settings. The study included a group of six normal volunteers and 12 patients implanted with Activitrax to examine the similarity of the pacemaker rate to normal sinus rhythm during acceleration and deceleration. The pacemaker was set to Activity mode, at a basic rate of 60 bpm. In volunteers, the device was externally secured on the chest wall and tested at two programmed settings. When programmed at a high threshold of activity and high rate response in volunteers, there was no significant difference in maximum normal sinus rates and pacemaker rates during arm waving, jumping in place, and walking during stress testing. At a medium activity threshold, the only significant difference occurred during submaximal stress testing, when the maximum sinus rate achieved was 141 +/- 19 bpm and the maximum pacing rate was 105 +/- 8 bpm (p less than .02). The pacemaker behaved in a similar manner in patients, successfully simulating the typical fast acceleration and slow deceleration of a normal sinus node in exercise testing. There was no difference in pacer response when implanted in abdominal or infraclavicular locations. The implanted units have functioned normally over a follow-up period of nine to 22 months. Activitrax can be programmed to achieve physiologic pacing rates in response to normal daily activities with appropriate programming.

Halothane metabolism in acyanotic and cyanotic patients undergoing open heart surgery

The metabolism of halothane was examined in patients with acyanotic and cyanotic congenital heart disease undergoing open heart surgery. Statistically significant (P less than 0.05) pre-surgical differences between acyanotic and cyanotic groups included pH (7.46 +/- 0.02 vs 7.36 +/- 0.02), PaO2 (277 +/- 58 vs 51 +/- 3 torr), O2 saturation (97 +/- 1 vs 74 +/- 4%), and hematocrit (45 +/- 3 vs 58 +/- 2%). Serum fluoride levels were significantly greater in cyanotic than in acyanotic groups 2-4 hours after initial exposure to halothane. Both groups had significant intragroup increases in serum levels of fluoride, bromide, and trifluoroacetic acid. Significant increases in serum levels of lactate dehydrogenase, creatinine phosphokinase, and glutamic oxaloacetate transaminase were observed in both groups, whereas, the cyanotic patients had additional significant increases in blood urea nitrogen and direct bilirubin. The cyanotic group also had higher total and direct serum bilirubin levels than the acyanotic group. Therefore, patients with cyanotic congenital heart disease had greater reductive metabolism of halothane than acyanotics. However, cyanotic and acyanotic patients had essentially similar postoperative derangements in hepatic and renal function.

Electrophysiologic effects of halothane and quinidine on canine Purkinje fibers: evidence for a synergistic interaction

The authors studied possible interactions between halothane and quinidine on the action potentials of canine Purkinje fibers superfused with Tyrode's solution. Using standard microelectrode techniques and a physiologic pacing rate (2 Hz), halothane in concentrations from 0.5% to 2% decreased the action potential duration to 50% repolarization (ADP50). Total ADP (APD100), in contrast, increased after 1% and 2% halothane. Resting membrane potential (RMP) and action potential amplitude (APamp) increased after 0.5% halothane, but returned to control with higher halothane levels. Conduction time (CT) increased at each halothane level. Pacing at faster (3 Hz) or slower (1 Hz) rates did not markedly alter the effects of halothane. Quinidine 1 X 10(-5)M decreased the phase O upstroke (Vmax) and prolonged APD100 and CT. When halothane was added, RMP and APamp decreased, Vmax decreased further, and APD100 and CT were markedly prolonged. This resulted in conduction block or inexcitability, especially at faster pacing rates (3 Hz). Synergistic interactions between halothane and quinidine were found on RMP, APamp, APD100, and CT. Effects on Vmax, APD50, and action potential duration to 90% repolarization (APD90) were additive. It is concluded that quinidine and halothane act synergistically to decrease action potential amplitude, lower RMP, and prolong conduction. Severe depression of conduction often progressed to conduction block or inexcitability when halothane, 2%, was administered during superfusion with therapeutic concentrations of quinidine.

Prophylactic nitroglycerin infusions during coronary artery bypass surgery

The effects of prophylactic infusion of 1 microgram X kg-1 X min-1 nitroglycerin (NTG) on the incidence of ischemia, hypertension, hypotension and perioperative myocardial infarction were studied in 81 patients during coronary artery bypass grafting (CABG). Forty-one patients (Group 1) received NTG and 40 patients (Group 2) received placebo. All patients received fentanyl for anesthesia and pancuronium. Mean arterial pressure (MAP), pulmonary capillary wedge pressure (PCWP), heart rate (HR), and cardiac output (CO) were measured before and after induction of anesthesia, after intubation, before and after chest incision, after sternotomy, after the pericardium was opened, and during normothermic cardiopulmonary bypass. Myocardial ischemia and infarction were diagnosed from the ECG, hypertension was defined as a 20% increase in MAP, and hypotension was defined as a 20% decrease in MAP compared with preinduction values. No significant differences between Groups 1 and 2 in HR, PCWP, or CO were seen. MAP was significantly lower in Group 1 than Group 2 (P less than 0.05) before chest incision, but increased to levels equal to Group 2 after sternotomy. Hypertension occurred in 32 Group 2 patients and 25 Group 1 patients (0.05 less than P less than 0.1). Group 1 patients had 0.95 +/- 0.14 episodes per patient of hypertension, while Group 2 patients had 2.10 +/- 0.31 episodes (P less than 0.05). Hypotension occurred in 20 Group 1 patients but only six Group 2 patients (P less than 0.05). There was no difference in the incidence of ischemia. In Group 1, nine patients (22%) had ECG changes of ischemia, while 12 patients in Group 2 (30%) had ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)

Simultaneous appearance of endocardial late potentials and ability to induce sustained ventricular tachycardia after procainamide administration

We describe a patient in whom procainamide induced the appearance of late potentials during intraoperative sinus rhythm electrogram mapping. Only nonsustained ventricular tachycardia (VT) could be induced while off all antiarrhythmic drugs. After administration of the procainamide, programmed stimulation induced sustained VT coincident with the appearance of late potentials during sinus rhythm. The late potential was recorded from the same site, during normal sinus rhythm, where mid to late diastolic activation during VT was recorded, and where cryotermination occurred during cryomapping. We hypothesize that procainamide slowed conduction, manifested as prolongation or appearance of late potentials in sinus rhythm, and facilitated induction of sustained reentrant ventricular tachycardia.