Effects of halothane and isoflurane on isolated human ventricular myocardium

Segments of viable human left ventricular trabeculae were obtained at the time of endocardial resection for intractable ventricular ectopy. Muscle segments which showed suitable and reproducible contractions in 26 mM K Tyrode solution with 1 microM isoproterenol were electrically stimulated after rest, and at frequencies of 0.1, 0.25, 0.5, and 1 Hz. Effects of 0.75% halothane and 1.3% isoflurane on peak tension, maximum rate of tension development (dT/dt-max), and on slow (calcium dependent) action potential (AP) characteristics were studied. Halothane depressed peak tension, dT/dt-max, and slow AP maximum rate of depolarization (Vmax) at all frequencies, and caused a significantly greater depression of peak tension and dT/dt-max at 0.5-1 Hz than after rest and at 0.1-0.25 Hz. Isoflurane did not significantly depress slow AP Vmax, showed no frequency dependent contractile depression, and depressed dT/dt-max less than halothane at 0.5 and 1 Hz. Halothane and isoflurane caused differing depression in the pattern of developed tension. The differential depression by halothane and isoflurane of human ventricular myocardium was similar to that previously observed in isolated animal ventricular tissue.

Calcitonin determination by a fast and highly sensitive enzyme amplified immunoassay

A colorimetric enzyme amplification system was used to develop an immunoassay for human calcitonin (hCT) with a sensitivity of 6 pmol/l, and intra- and inter-assay CVs of 12% and 11.8% respectively for the low pool, and 10% and 11.2% for the high pool. The mean recovery of added synthetic hCT (58.5 pmol) from the plasma of 10 patients was 110% (64.4 pmol). The correlation coefficient between radioimmunoassay (RIA) and amplified enzymo-immunoassay was found to be 0.96 (p 0.001). The assay was successfully applied to the measurement of elevated calcitonin levels in plasma from patients with medullary carcinoma of the thyroid (MCT). AEIA offered a reliable and sensitive alternative to RIA for calcitonin determination with the added advantage of convenience as the label employed was much more stable.

Plasma immunoreactive beta-endorphin in dexamethasone suppressors and non-suppressors of cortisol

Immunoreactive plasma beta-endorphin level was assayed in 33 patients with major affective disorder and in 16 psychiatrically normal controls before and after dexamethasone (1 mg) administration at 23.00 h. There were 18 cortisol suppressors and 15 non-suppressors among the patient group. All controls suppressed cortisol. Plasma beta-endorphin before dexamethasone was significantly different between suppressors, non-suppressors and controls (P less than 0.05, ANOVA). Concentrations of beta-endorphin were 4.7 +/- 0.7, 3.1 +/- 0.3 and 2.8 +/- 0.3 pmol/l for non-suppressors, suppressors and controls respectively. Following dexamethasone, beta-endorphin concentrations were again significantly different between groups (P less than 0.005, ANOVA). Concentrations were 4.6 +/- 0.7, 2.3 +/- 0.2 and 1.6 +/- 0.2 pmol/l for non-suppressors, suppressors and controls respectively. The implications of these findings are discussed.

Depression of myocardial contractility in vitro by bupivacaine, etidocaine, and lidocaine

The effects of local anesthetics in depressing myocardial contractility were studied in isolated guinea pig right ventricular papillary muscles. Bupivacaine and etidocaine, 4 and 10 microM, showed reverse frequency-dependent depression of contractility, that is, less significant depression of contractility at higher stimulation frequencies (2-3 Hz) than at lesser frequencies (less than 1 Hz). Lidocaine, 40 microM, demonstrated a similar trend. In contrast, the normal action potential maximum rate of depolarization (Vmax), a measure of sodium channel conductance, was significantly more depressed at 2-3 Hz by bupivacaine and etidocaine than by lidocaine. Consequently, contractile depression could be overcome only at higher stimulation frequencies, at which conduction was depressed. To explore the mechanism of the contractile depression, local anesthetic effects were studied on slow (calcium channel-mediated) action potentials in partially depolarized papillary muscles. Etidocaine and bupivacaine, 4 and 10 microM, and lidocaine, 40 and 100 microM, caused a marked depression of the late-peaking contractile responses, attributed to Ca2+ release from the sarcoplasmic reticulum. In contrast, only 10 microM bupivacaine caused any significant depression of the slow action potential rate of depolarization (to 89% of control), consistent with a possible small depression of Ca2+ entry.

Differential depression of myocardial contractility by halothane and isoflurane in vitro

Depressant effects of halothane and isoflurane on isolated right ventricular guinea pig papillary muscle bathed in Tyrode's solution at 37 degrees C were examined. Contractions were elicited by stimulation through external field electrodes while tension was recorded continuously and the intracellular cardiac action potential (AP) was monitored simultaneously by microelectrodes. The time differential of tension (dT/dt) and of membrane potential (V) was determined electronically and recorded also. Contractions after rest and at stimulation rates of 0.1, 0.25, 0.5, 1, 2, and 3 Hz were studied. With normal APs, isoflurane (1.3 and 2.5%) depressed peak tension significantly less at high frequencies than did equivalent doses of halothane (0.75 or 1.5%). Isoflurane depressed dT/dt max less than halothane at all frequencies. At 0.3 Hz stimulation, isoflurane (1-4%) significantly increased the normal AP duration by 7-11%. Slow calcium-dependent APs and accompanying contractions were studied in partially depolarized muscles (-40 to -45 mV resting potential in 26 mM K+ Tyrode's solution) stimulated with 0.1 microM isoproterenol. Following rest and at 0.1, 0.25, 0.5, 1, 2, and 3 Hz, both isoflurane (1.3% or 2.5%) and enflurane (1.7% or 3.5%) markedly depressed the late-peaking slow AP contraction observed with low-frequency stimulation. Halothane (0.75% or 1.5%) caused a similar contractile depression (40-60%) at all frequencies. In contrast, isoflurane depressed early peaking tension and the dT/dt max at frequencies greater than 1 Hz significantly less than did halothane or enflurane. At 0.3 Hz, 2% and 4% isoflurane caused 9% and 17% depression of slow AP maximum rate of depolarization (Vmax), but significantly prolonged the AP duration. Isoflurane altered the pattern of tension development in a different manner than halothane, suggesting differing mechanisms of myocardial depression by these anesthetics.

Effects of dantrolene and verapamil on atrioventricular conduction and cardiovascular performance in dogs

The effects of intravenous dantrolene sodium, alone and in combination with verapamil, upon atrioventricular conduction, cardiovascular function, and neuromuscular function were studied in chloralose-urethane anesthetized dogs. Hemodynamic variables (systemic arterial, central venous, and pulmonary arterial pressures and cardiac output) and His-bundle electrograms were monitored, and measurements were made during atrial pacing at 175 beats/min, as well as at the spontaneous heart rate. In one part of the study animals received dantrolene sodium incrementally at 30-min intervals to cumulative doses of 1, 2.5, 5, and 10 mg/kg. Subsequently, verapamil was administered incrementally at 30-min intervals to cumulative doses of 0.1, 0.2, 0.4, and 0.6 mg/kg. In the second part of the study, dogs received identical dosage sequences, but verapamil preceded dantrolene administration. Dantrolene caused no significant depression of atrioventricular conduction or cardiac performance but did increase systemic vascular resistance at doses above 2.5 mg/kg. Verapamil alone (greater than or equal to 0.2 mg/kg) or with dantrolene (greater than or equal to 0.1 mg/kg) increased the atrial-His-bundle conduction interval. In the presence of verapamil, dantrolene (greater than or equal to 2.5 mg/kg) decreased cardiac index and increased pulmonary artery occlusion pressure. Although 0.6 mg/kg verapamil depressed cardiac index and increased pulmonary artery occlusion pressure, this effect was observed at 0.4 mg/kg after prior treatment with dantrolene. Verapamil did not augment the dose-dependent twitch depression observed with dantrolene. Dantrolene alone had no apparent effect on atrioventricular conduction and caused little enhancement of the effects of verapamil. However, each drug appeared to enhance the myocardial depressant effects of the other.

A mother and baby unit in a psychiatric hospital

Two rooms where women with puerperal psychiatric illness could be admitted together with their babies were provided in a general psychiatric unit. Over a 21-month-period demand for joint admission far exceeded capacity and most referrals could not be accepted. Women with various psychiatric disorders were referred to and managed in the unit. Greatest demand was for young women suffering from psychosis following childbirth.

Biochemical separation of delayed rectifier currents in frog short skeletal muscle fibres

Frog short (1-1.5 mm) skeletal muscle fibres in sucrose hypertonic Ringer at 5 degrees C were voltage clamped employing a two-electrode technique. Decreasing pH from 7.0 to 5.0 dramatically increased the rate of turn on of the slow delayed rectifier (GK,s) current, so that it became similar to the rapidly activated form. The accelerating effects of decreased pH upon slow current kinetics had a pKa of 5.8. Decreased pH also appeared to shift the voltage dependence of fast and GK,s gating to more positive potentials. In addition, a decrease in pH from 7.0 to 5.0 shifted the reversal potential of GK,s by over 11 mV in the positive direction. GK,s was selectively and irreversibly abolished by applying 1 mM-diethylpyrocarbonate (DEP), a histidine reagent. This effect occurred even after GK,s had been accelerated by low pH. DEP had no effect upon fast delayed rectifier current except for a small positive shift in voltage dependence. Application of 1 or 2 mM-N-ethylmaleimide, a sulphydryl reagent, depressed the fast delayed rectifier while sparing the GK,s currents. However, the muscle fibres also developed markedly increased leakage currents.

Ionic conductances in frog short skeletal muscle fibres with slow delayed rectifier currents

Short (0.8-1.6 mm) lumbricalis fibres of Rana pipiens were voltage clamped by a two-micro-electrode technique at 5 degrees C in sucrose hypertonic Ringer solution (SHR). Terminated linear cable analysis suggests that if the current electrode is placed near the centre of the fibre length and the voltage-sensing electrode is placed 0.19 times the fibre length from the current electrode, the fibre can be adequately voltage clamped and the conductance may be simply calculated as I/V for fibre length constants from 1.0 to 0.15 mm. In SHR solution lumbricalis fibres have action potentials with peak amplitudes of only +2 to 7 mV and a slow, gradual repolarization, distinct from the action potentials observed in sartorius muscle. In 60 mM-Na+ SHR the inward Na current could be adequately controlled over the fibre length, providing an estimated Na conductance (GNa) of 8.9 mS/cm2. The magnitude of GNa and GK (delayed rectifier) in lumbricalis fibres was approximately 20% of that reported for sartorius and semitendinosus, although the resting conductances were similar. Fibres demonstrated delayed rectifier currents with complex patterns of activation suggesting two components of conductance (fast, GK,f and slow, GK,s) which were combined together in varied amounts: (a) GK,f activated rapidly to a maximum within 80 ms at 0 mV as previously described (Adrian, Chandler & Hodgkin, 1970a); (b) GK,s activated gradually with depolarizations below -50 mV and achieving peak currents at about 400 ms at 0 mV. In about 10% of lumbricalis fibres studied, GK,s occurred in isolation with a peak magnitude of 1.4 +/- 0.4 mS/cm2 (+/- S.D.). GK,s activation kinetics and tail currents are described by a squared two-state (l2) Hodgkin-Huxley model and have a Q10 of 2.8. These currents inactivated with a time constant of 5-7 s at 0 mV. Isolated GK,s with identical kinetics was also observed in certain sartorius fibres studied with the three-electrode voltage clamp. The fractional amount of GK,s in the combined delayed rectifier (GK,s + GK,f) currents could be estimated from analysis of the late activation phase with depolarization. Combined delayed currents were described by summing GK,f currents using a n4 model with GK,s currents defined by the l2 model.

Calcitonin gene-related peptide: potent vasodilator and major product of calcitonin gene

In addition to calcitonin and katacalcin, the human calcitonin gene encodes a novel peptide--calcitonin gene-related peptide (CGRP)--a potent vasodilator. A sensitive and specific radioimmunoassay was developed to study plasma levels of CGRP in normal subjects. CGRP circulates at five times the concentration of calcitonin, suggesting that it may be an important physiological regulator of vascular tone and blood flow.

Inhibition of platelet function by cis-unsaturated fatty acids

The uptake of free fatty acids has previously been shown to affect the capping of lymphocytes, and there is evidence that different types of fatty acids may partition into separate lipid domains in cell surface membranes. In studies of gel-filtered human platelets, we found that cis-unsaturated fatty acids (1-35 microM) inhibited platelet shape change, aggregation, and secretion of 5-hydroxytryptamine induced by thrombin, adenosine diphosphate (ADP), collagen, U46619 (a thromboxane A2 analog), or plant lectins, but not that induced by A23187, a calcium ionophore. Trans-unsaturated and saturated fatty acids had little or no inhibitory effect. The inhibitory effects of cis-unsaturated fatty acids were not affected by inhibition of adenylate cyclase or cyclooxygenase. 14C-labeled fatty acids were taken up into platelet lipids. The maximum platelet-inhibitory effect of cis-unsaturated fatty acids was seen when over 90% of the platelet label was still in the form of free fatty acids. Platelet inhibition could be reversed by washing the platelets by gel filtration. Binding of platelet agonists to the platelet was not inhibited by the fatty acids. Cis-unsaturated fatty acids, but not trans-unsaturated or saturated fatty acids, decreased fluorescence polarization of platelets or isolated platelet membranes monitored with 1,6-diphenyl- 1,3,5-hexatriene. The potency of the fatty acids as inhibitors of platelet aggregation was inversely correlated with their melting points. These data suggest that inhibition of receptor-mediated platelet responses by cis-unsaturated fatty acids results from perturbation of the platelet membrane in specific lipid domains.

Adverse impact of a calcium entry-blocker (verapamil) on intracranial pressure in patients with brain tumors

In order to examine the effects of verapamil on intracranial pressure (ICP) in patients with compromised intracranial compliance, five hypertensive patients with supratentorial tumors were given verapamil, 5 mg intravenously, at the time of anesthesia induction. Within 4 minutes, ICP increased 67% from 18 +/- 4 mm Hg (standard error) to 27 +/- 5 mm Hg (p less than 0.05), whereas mean arterial pressure decreased 20% from 111 +/- 7 mm Hg to 89 +/- 4 mm Hg (p less than 0.05), and cerebral perfusion pressure (CPP) decreased 33% from 93 +/- 11 mm Hg to 62 +/- 6 mm Hg (p less than 0.05). The increases in ICP responded promptly to hyperventilation and intravenous lidocaine (1.5 mg/kg). A control group of five hypertensive patients with supratentorial tumors received the same anesthetic agents without verapamil. In this group, ICP and CPP were unchanged. The authors conclude that calcium entry-blockers, such as verapamil, should be avoided in patients with compromised intracranial compliance unless ICP is being monitored and proper therapy for intracranial hypertension can be rapidly instituted.

Intraoperative diagnosis and treatment of massive pulmonary embolism complicating surgery on the abdominal aorta

Massive pulmonary embolism associated with total cardiovascular collapse occurred during the surgical repair of a ruptured abdominal aortic aneurysm with an aortocaval fistula. Pulmonary artery pressure monitoring permitted immediate diagnosis whereas central venous pressures did not reflect the obstruction to right ventricular outflow. Pulmonary embolectomy without cardiopulmonary bypass was performed successfully.

Assay of blood and tissue aldehydes by HPLC analysis of their 2,4-dinitrophenylhydrazine adducts

A new method for the assay of blood and tissue acetaldehyde is described. Samples are reacted with a methanolic solution of 2,4-dinitrophenylhydrazine (DNP) and the DNP-aldehyde adducts extracted into CHCl3. DNP-[14C]formaldehyde is added as internal standard. The CHCl3 extracts are washed with HCl and H2O and purified by aluminium oxide chromatography. The eluate is dried down, re-dissolved in methanol and subjected to quantitative analysis by HPLC. The acetaldehyde adduct was identified by co-chromatography with the authentic derivative and by mass spectrometry. Recoveries of added acetaldehyde were 85% and addition of 20 mmol ethanol to the sample gave no apparent increment in acetaldehyde content. This technique is suitable for assessment of acetaldehyde levels in clinical and experimental studies of ethanol metabolism.

Spinal arachnoiditis ossificans: case report

A case of spinal arachnoidits ossificans is presented and discussed. This is a rare pathological finding. A review of the pertinent literature is given. Laminectomy and removal of the calcification was followed by resolution of the neurological deficit.

Paraplegia following aortic surgery

It has long been recognised that paraplegia may occur after various surgical procedures on the heart and the aorta. Paraplegia occurring following traumatic rupture of the aorta has not been commonly reported due to the dismal prognosis of such rupture. Over the past 3 years, we have encountered five patients who survived traumatic rupture of the aorta and developed paraplegia, and three patients who had chronic dissecting aneurysms of the aorta who also developed paraplegia. These patients continued to show neurological and functional improvement over the years. We are presenting these cases to illustrate their neurological improvement and to show that the prognosis for these patients may not be as dismal as previously reported once they survive the acute episode.