Biomedical subjects
Publications and source records attributed to M A Marcus.
A case report is presented of ventricular fibrillation after intramyometrial injection of 1 mg dinoprostone (PGE(2)) during cesarean section performed under general anesthesia. Anesthesiologists should be aware of the potential cardiovascular side-effects of prostaglandins used by the obstetrician.
The use of epinephrine as a test dose for epidural analgesia in obstetrics remains controversial. Isoproterenol as a test dose may be efficacious in the parturient. However, the effects of isoproterenol on the uterine blood flow (UBF) and umbilical blood flow (UMB) in the parturient are unknown. In a randomized, double-blind study, the hemodynamic variables in 60 nonlaboring women at term were studied 5 min before and for 10 min after an intravenous injection of either 5 micrograms isoproterenol or 5 micrograms saline. The UBF was assessed in 35 women and the UMB in 25 women using a color Doppler technique. The results of 50 women were used for further analysis. Maternal heart rate (MHR) was measured continuously, and maternal mean arterial pressure was measured every minute. MHR did not change after saline but increased significantly after injection of isoproterenol. UBF also increased significantly after isoproterenol during the same time interval. UMB did not change. Other hemodynamic variables did not change. We conclude that isoproterenol, 5 micrograms, may be a suitable test dose for epidural analgesia in obstetrics.
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Isoproterenol 5 micrograms may be an effective marker of accidental intravascular injection in women in labor; however, before isoproterenol can be incorporated in routinely used epidural test doses, the safety and usefulness should be determined in an animal model. This study was designed to examine the hemodynamic effects of isoproterenol in comparison with epinephrine in the pregnant ewe. Five doses of isoproterenol were tested and compared with two doses of epinephrine in a randomized cross-over fashion. After administration of isoproterenol there was a small decrease of uterine blood flow (UBF) and maternal mean artery pressure (MMAP), which both almost immediately returned to baseline. When epinephrine was used a more pronounced and more prolonged decrease of UBF occurred. Increasing doses of isoproterenol resulted in dose-dependent increases in maternal heart rate (MHR), while with epinephrine this was not the case. A significant increase in the cardiac output was seen after isoproterenol. Neither isoproterenol nor epinephrine affected fetal heart rate (FHR), fetal mean arterial pressure (FMAP), amniotic fluid pressure (Amn-pr), blood gases, or acid base status in the mother and the fetus. Provided that neurotoxic effects are absent, isoproterenol might be a better alternative than epinephrine as a test dose for possible intravenous placement of an epidural catheter in pregnant women.
This study examines the placental transfer and hemodynamic and acid-base changes after intravenous (i.v.) and epidural administration of sufentanil in the chronically instrumented maternal-fetal sheep preparation. A dose of 50 micrograms sufentanil was injected either i.v. or epidurally into seven ewes. Neither i.v. nor epidural injection of sufentanil affected maternal mean arterial pressure (MMAP), uterine blood flow (UBF), maternal heart rate (MHR), fetal mean arterial pressure (FMAP), fetal heart rate (FHR), or blood gases and acid-base status in mother and fetus, After i.v. administration, a peak sufentanil level of 1.28 ng/mL +/- 0.285 (SD) was detected in maternal plasma. A peak plasma level of 0.037 ng/mL +/- 0.041 (SD) was attained in the fetus. A constant maternal-fetal concentration ratio of 5.5 from 15-60 min after the i.v. injection was found. After epidural injection a mean peak plasma level of 0.059 ng/mL +/- 0.042 (SD) was reached in the mother 25 min after injection. Sufentanil levels were undetectable in fetal plasma after epidural injection into the mother. Because placental transfer of sufentanil is small, the maternal and fetal cardiovascular and acid-base effects are minimal in the pregnant ewe.
Administration of fluids intravenously prior to spinal and epidural analgesia in obstetrics is required to prevent maternal hypotension and fetal hypoxia. A colloid solution, such as hydroxyethyl starch (HES), might be preferable considering the capacity to stay intravascularly for a longer period. In this study the placental transfer of HES and the hemodynamic effects after infusion were investigated using a chronic maternal-fetal sheep preparation. Either 500 mL HES 10% or 750 mL lactated Ringer's solution (RL) was infused intravenously into the ewe over 30 min. Fetal and maternal blood were assayed for HES, blood gases, and acid-base status before and at regular intervals after infusion. Maternal and fetal cardiovascular variables were recorded continuously for 90 min. After HES infusion, maternal HES levels peaked at 30 min ranging from 6.9 mg/mL to 12.1 mg/mL and declined at 24 h to levels between 0.3 mg/mL and 2.8 mg/mL. Mean fetal HES concentrations remained below 0.3 mg/mL. Infusion of HES decreased hemoglobin (Hb) and plasma viscosity (PV) in the mother. Infusion of RL decreased Hb, but did not change PV. Infusion of HES significantly increased uterine blood flow (UBF), cardiac output (CO), total oxygen-delivery capacity, and uterine artery oxygen delivery. In contrast, infusion of RL did not significantly change these variables. Infusion of HES increases UBF, CO, and uterine and total oxygen-carrying capacity in the pregnant ewe. No significant transplacental transfer of HES was shown.
The purpose of this study was to examine global and regional hemodynamic changes during induction of anesthesia with eltanolone, a new short-acting steroid hypnotic, as compared to propofol, in chronically instrumented dogs. The effects on cardiac performance were assessed in six animals. Renal and hepatic blood flows were examined in a separate study including five animals. Two doses of each drug were investigated: eltanolone 2.5 and 5 mg/kg and propofol 7.5 and 15 mg/kg. Left atrial filling pressures and cardiac output were not affected by either drug. Maximum rate of increase of left ventricular pressures decreased both with eltanolone (-28% and -40% from awake control for the 2.5 and 5 mg/kg doses, respectively) and with propofol (-19% and -30% from awake controls with 7.5 and 15 mg/kg respectively). In contrast to propofol, eltanolone preserved arterial blood pressure. Propofol lowered systemic vascular resistance (-21% and -39% with the low and high dose, respectively), and only slightly decreased left ventricular wall thickening fraction (-16% and -21%). Eltanolone did not affect systemic vascular resistance but reduced the wall-thickening fraction dose-dependently (-28% and -61%). Propofol, but not eltanolone, induced moderate coronary vasodilation. Hepatic arterial blood flow velocity decreased dose-dependently (-21% and -64%) during eltanolone anesthesia whereas, in contrast, it increased after propofol (+59% and +64%). Renal and portal venous blood flows remained essentially unaltered from awake conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
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The haemodynamic effects of urapidil, an alpha 1-antagonist with central serotoninergic properties, were studied in an experimental canine model of chronic ischaemic heart disease. Global and regional haemodynamic recordings were made in conscious dogs with ameroid-induced single vessel coronary artery occlusion. Three intravenous bolus-infusion doses of urapidil (0.1 mg kg-1 + 0.3 mg min-1; 0.5 mg kg-1 + 1.5 mg min-1; 2.5 mg kg-1 + 7.5 mg min-1) were given on separate occasions in 12 animals. Regional blood flows were measured with radioactively labelled tracer microspheres. The effects of urapidil and dipyridamole, a powerful arteriolar vasodilator, on regional myocardial blood flow distribution to normal and collateral-dependent myocardium were compared. Urapidil caused a dose-dependent reduction of arterial blood pressure. There was moderate tachycardia and decreased left atrial filling pressures at the higher doses. Urapidil was a much weaker coronary vasodilator than dipyridamole. Dipyridamole caused maldistribution of intercoronary and transmural flows (endo-to-epicardial flow ratio in collateral-dependent regions from 1.35 +/- 0.07 to 0.7 +/- 0.13 and flow ratio between collateral-dependent and normal regions from 1.09 +/- 0.03 to 0.57 +/- 0.14). Urapidil preserved blood flow to both regions. Urapidil did not affect systolic wall thickening fraction in normal or ischaemic regions of the heart. Renal (+16%) and splanchnic perfusion (+45%) increased during urapidil infusion. Urapidil preserves myocardial function and perfusion and increases renal and intestinal blood flow in dogs with chronically ischaemic hearts.
A case of a person struck by lightning is presented in which treatment consisted of 60 min of resuscitation, followed by a 3 day period of artificial ventilation. Persons who are struck by lightning might benefit from prolonged resuscitation efforts, since patients such as this one, as well as similar cases described in the literature, have survived without major sequelae. In our opinion, on-the-spot advanced life support, hypothermia and a moderate rehydration policy contributed to this patient's successful resuscitation.
The effects of moderate systemic hypotension with halothane (HALO) and isoflurane (ISO) on regional myocardial function and perfusion were studied in dogs with chronic coronary artery occlusion. Vasodilator reserve in collateral-dependent (CD) myocardium was quantified in conscious animals by using a dipyridamole challenge test. Blood flow was distributed homogeneously to the normal (Nl) and CD myocardium at rest, but subendocardial perfusion increased only in the Nl area after dipyridamole. HALO and ISO were administered at doses that reduced diastolic arterial pressure to 50 mm Hg. End-tidal concentrations were 1.3 +/- 0.2 vol% for HALO (1.5 minimum alveolar anesthetic concentration) and 1.8 +/- 0.2 vol% for ISO (1.4 minimum alveolar anesthetic concentration), respectively. Global and regional hemodynamic depression were more pronounced with HALO. Systolic wall-thickening fraction decreased both in the Nl (-37%) and CD area (-27%). Myocardial blood flow to Nl and CD myocardium decreased to a comparable extent. ISO predominantly decreased systemic vascular resistance and, when compared to HALO, decreased systolic wall-thickening fraction less in both the Nl (-19%) and CD area (-18%). In addition, regional myocardial perfusion to both Nl and CD myocardium remained virtually unaltered from conscious control conditions. Despite reductions of diastolic blood pressure to 50 mm Hg, neither HALO nor ISO induced ischemic dysfunction in myocardium with diminished vasodilator reserve. Both anesthetics preserved intercoronary as well as transmural blood flow distribution. During HALO, myocardial perfusion was less both in Nl and CD myocardium due to a more pronounced metabolic depression. We conclude that moderate hypotensive doses of ISO and HALO preserve regional myocardial function of collateral-dependent myocardium in dogs with single vessel occlusion and enhanced collateral circulation.
STUDY OBJECTIVE: To evaluate the safety and efficacy of oral transmucosal fentanyl citrate (OTFC) as a noninvasive method of providing analgesia and sedation for patients in the emergency department. DESIGN: Prospective, nonblinded. SETTING: ED of a tertiary care university hospital. TYPE OF PARTICIPANTS: Ten patients, 6 to 34 years old, with acute painful conditions requiring treatment in the ED. INTERVENTIONS: Premedication with OTFC and local anesthetic prior to incision or wound closure. MEASUREMENTS AND MAIN RESULTS: Pain and activity (sedation) scores, vital signs (including systolic and diastolic arterial blood pressures, heart and respiratory rates, and pulse oximetry-determined oxygen saturation) were measured before and at two- to ten-minute intervals during and after OTFC consumption. All patients accepted OTFC. Patients received an average of 13.7 +/- 2.5 micrograms/kg of fentanyl citrate in 11.8 +/- 6.8 minutes. Decreases in pain were reported in two patients in two minutes and by all patients 14 minutes after beginning OTFC consumption. Sixty percent of patients became drowsy or sedated 12 to 30 minutes after beginning OTFC. Vital signs and oxygen saturation changes were small and not clinically significant. The most important side effects were pruritus (30%), nausea (20%), and dizziness and dry mouth (40%). All were considered mild and not disturbing, although one patient required post-procedure antiemetic therapy for recurrent vomiting. The mean time to discharge from the ED was 139 +/- 54 minutes after receiving OTFC. CONCLUSION: OTFC may be useful in providing rapid, noninvasive analgesia and sedation in the ED and deserves further evaluation.
The authors evaluated the sigmoidal administration of methohexital, the effect of methohexital concentration (1% versus 2%), the effect of dosage (25 mg/kg versus 15 mg/kg) on sleep-success rate, administration - sleep time, recovery time and the effect of aspirating the residual methohexital on recovery time. The study demonstrated that both 1% solution and 25 mg/kg of sigmoidal methohexital were independently associated with significantly higher sleep success rate and faster onset of sleep compared with 2% and 15 mg/kg of sigmoidal methohexital solution respectively. The recovery time was significantly affected by the dose of methohexital and was not significantly affected by the concentration of methohexital solution. Aspiration of the residual methohexital did not significantly affect the recovery time.
The authors compared the safety, efficacy, and effects on gastric volume and pH of oral transmucosal fentanyl citrate (OTFC) premedication and of placebo lollipop and no premedication in 55 children undergoing elective operations. The patients were randomly assigned to receive no premedication (group A, N = 18); OTFC containing 15-20 micrograms/kg of fentanyl citrate (group B, N = 18); or a placebo lollipop (group C, N = 19). Activity (sedation) and anxiety scores, vital signs (including systolic and diastolic arterial blood pressures, heart and respiratory rates), and pulse oximetry determined oxygen saturation were measured before and at 10-min intervals after premedication until the patients were taken to the operating room. Gastric contents were aspirated via an orogastric tube and analyzed for volume and pH after induction of anesthesia. Quality of induction and recovery were evaluated using scoring schedules; recovery times were measured and side effects recorded. OTFC was readily accepted and provided levels of sedation and anxiolysis significantly greater after 10 min than after no premedication or the placebo lollipop. Arterial blood pressures, heart rate, and oxygen saturations were not different among the three groups. In patients given OTFC, respiratory rates were significantly lower after 10 min than they were in patients having no premedication.(ABSTRACT TRUNCATED AT 250 WORDS)
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Resonance Raman spectra of squid rhodopsin have been obtained under a variety of temperature and illumination conditions. The data have been characterized in terms of spectral contributions from squid rhodopsin, isorhodopsin, bathorhodopsin, lumirhodopsin, mesorhodopsin, P-465, and acid metarhodopsin. The results are compared with the spectral features obtained from bovine rhodopsin, isorhodopsin, and bathorhodopsin. The data support a proposed structure for the chromophore in bathorhodopsin which is not all trans, 11-cis, or 9-cis. This structure can be generated from either rhodopsin or isorhodopsin by a similar motion (simultaneously rotating chromophore carbon atoms 10 and 11 out-of-plane). Furthermore, we detect the same distinct bathorhodopsin vibrational modes when rhodopsin is illuminated between 4 and 100 K. This demonstrates that under steady-state illumination the light-induced chromophore structural alterations occurring at 4 K are very similar to those occurring at higher temperatures. Finally, our data indicate that bathorhodopsin is generated not only by structural transitions in the chromophore but also alterations in the opsin conformation as has recently been proposed[Lewis, A. (1978) Proc. Natl. Acad. Sci. U.S.A. 75, 549].
Resonance Raman spectra of various intermediates in the bacteriorhodopsin proton pumping cycle have been obtained at physiological and low temperatures. To interpret these data, spectra of modél compounds, bacteriorhodopsin analogues, and isotopically labeled membranes have been measured. These results demonstrate that a protein group interacts with the Schiff base proton and, thus, the chromophore in protonated bacteriorhodopsin species is not a simple protonated Schiff base. This accounts for the abnormally low frequency of the C=N+H vibrational mode in bacteriorhodopsin and other failures to model the chromophore in bR570 with a simple butylamine protonated Schiff base of all-trans-retinal. To obtain the resonance Raman spectrum of M412 at physiological pH and temperatures, a dual beam kinetic technique was developed. We demonstrate that in the fingerprint region of the resonance Raman spectrum M412 is modeled accurately by a simple unprotonated butylamine Schiff base of all-trans-retinal. Spectral resolution and the solution environment of the membrane suspensions play important roles in this conclusion. Kinetic resonance Raman techniques are also used to monitor the time evolution of the M412 species and the intermediates which precede it. We find spectral features in our kinetic data which can be assigned to L550, and we present evidence for a new unprotonated species (X) which occurs before M412. Single pass flow resonance Raman spectra of bR560 also have been obtained, and, although bR570 and M412 appear to have all-trans chromophores, there are 13-cis-like features in the spectra of bR560, L550, and X.
Subpicosecond pulses have been used to study the ultrafast dynamics of the photochemistry of bacteriorhodopsin. An optically induced absorption that appears in about 1.0 picosecond at physiological temperatures has been resolved in time. The data can be interpreted in terms of the photochemical formation of bathobacteriorhodopsin and provide support for an excitation mechanisms involving molecular rearrangement in the protein induced by electron redistribution in the chromophore.