Magnesium therapy in acute myocardial infarction--a double-blind study.

Various methods have been proposed and tried to limit the extent of myocardial damage at the time of infarction. We chose to assess the usefulness of intravenous magnesium in this regard because of its important role in myocardial metabolism and function and the suggestion of its deficiency in ischemic hearts. A double-blind randomized trial was carried out and results analyzed in 76 patients. At the end of the infusion period the mean serum Mg++ level for the treated group was 3.6 versus 1.9 mg/dl for the control group. The estimated size of infarction (as measured by MB-CK release) was not significantly smaller overall in the treated group (37.4 +/- 4.3 vs. 45.6 +/- 4.6 MB-CK g/Eq), but was significantly smaller in the treated subgroup without heart failure (31.6 +/- 5.8 vs. 44.7 +/- 4.8 MB-CK g/Eq). A trend toward less ventricular ectopy was seen in the group treated with magnesium. There was significantly less lidocaine used for the treatment of ventricular dysrhythmias in this group. Magnesium supplementation in patients undergoing acute coronary events is promising and deserves further study.

The value of urinary chloride measurement in distinguishing surreptitious vomiting from Bartter's syndrome.

Urinary chloride measurement is a simple and common procedure but its value in clinical practice is not extensive. This case report highlights a practical and important use of this test. A patient presented with most of the clinical and metabolic derangements of Bartter's syndrome but was found to have extremely low or absent urinary chloride excretion. Her ability to excrete chloride was, however, intact during a chloride load test. The finding of low urinary chloride excretion did not support the diagnosis of Bartter's syndrome and suggested an extrarenal loss of chloride. This was confirmed when she eventually admitted to surreptitious vomiting.

Hyperparathyroidism in Paget's disease of bone.

The association between Paget's disease and hyperparathyroidism was explored in 12 patients by means of a calcium loading test. Parathyroid adenomata were discovered at surgery in 2 and parathyroid hyperfunction was found in varying degrees in 4 others. Differing responses to the calcium loading test were interpreted as reflecting different stages in the bone formation-resorption disequilibrium found in Pagetic bone. A prolonged imbalance in favour of formation is suggested as constituting a stress on the homeostasis of extracellular fluid calcium levels that leads to parathyroid hyperfunction.

Autosomal dominant hypoparathyroidism: a proband with concurrent nephrogenic diabetes insipidus.

In this paper we report an extended family with well documented autosomal dominant hypoparathyroidism which was ascertained through a proband with coincident nephrogenic diabetes insipidus. Clinical findings were limited to a slight decrease in overall stature and to clinical signs of hypocalcaemia. Intelligence was normal and two patients were asymptomatic. Published reports have established that autosomal dominant, autosomal recessive, and sex linked recessive familial isolated hypoparathyroidism exist. However, in almost half the reported families an X linked dominant aetiology cannot be excluded and, at present, clinical criteria provide only minimal aid in distinguishing between the different genetic types. There remains a need for detailed documentation of further families were the pattern of inheritance is clear.

Implementation of a pneumatic-tube system for transport of blood specimens.

Whole-blood specimens were transported through an installed 485-meter pneumatic-tube system dedicated to blood transport. The system featured constant-speed, low-carrier-velocity travel (3.6 m/sec) with controlled deceleration prior to arrival at its destination. Inserts were designed with ample use of padding to minimize agitation during transport and landing. Serum potassium, hemoglobin, and lactate dehydrogenase activity and whole-blood pH, PCO2, and PO2 were not altered in freshly drawn blood transported in this system. Partial filling or heparinization of the specimen containers did not alter the results. When specimens were allowed to clot prior to pneumatic-tube transport, significantly higher levels of serum lactate dehydrogenase were obtained. This study demonstrates that transport of whole-blood specimens by pneumatic tube without damage to blood components is feasible.

Cyanide toxicity following nitroprusside induced hypotension.

Several recently reported deaths following the use of sodium nitroprusside have been attributed to the accumulation of the nitroprusside metabolite, cyanide. In this study, brief nitroprusside infusions (mean = 36 minutes) were administered in currently recommended doses during intracranial surgery. The peak blood cyanide following the infusions was 65.2 +/- 17.5 microgram per cent (mean +/- SE) (n = 13). It occurred within 45 minutes after infusion. The highest cyanide level detected was 205 microgram per cent, which is within the range of reported lethal blood cyanide levels. Metabolic acidosis developed in the four patients with the highest blood cyanide levels (range 90-205 microgram per cent). This occurred between 45 and 180 minutes following the cyanide peak. Blood ATP levels were depressed in the same patients. These findings are indicative of disturbed aerobic metabolism. We conclude that there is evidence of cyanide toxicity when nitroprusside is infused into patients using currently recommended doses. We recommend that for short infusions the dose of sodium nitroprusside should not exceed 0.5 mg/kg.

Emergency toxicology in a general hospital.

A study of all cases of attempted suicide by drug ingestion over a 6-month period was undertaken to evaluate the use of an emergency toxicology service and to establish the role of the emergency toxicology laboratory in the diagnosis and management of cases of attempted suicide. A total of 235 requests for emergency toxicologic analysis involving 259 specimens was received. Results of toxicologic screening were positive for 58% of all cases (range, 49% for patients who were drowsy to 90% for patients who were deeply unconscious). Barbiturate blood values did not correlate well with either the level of consciousness or the clinical state of the patient. In almost all patients who were drowsy or who were unconscious but had normal reflexes and vital signs there was no deterioration in the clinical state and no active treatment was required. The study demonstrated the need to educate all personnel involved in the care of patients with attempted suicide to limit laboratory investigations to the management of patients who benefit from such analyses. Quantitative drug analyses have a limited contribution to the management of such patients and should be performed only for patients with mixed drug overdosage and when the drugs require dialysis for their elimination from the body.

Ultrastructural observations on differentiating human preadipocytes cultured in vitro.

A cell type, preadipocytes, isolated from the stroma of adult human adipose tissue appears capable of differentiating, in culture, into a cell with morphological features similar to that observed in terminally differentiated human adipocytes cultured under similar conditions. During this process of differentiation, preadipocytes develop extensive rough endoplasmic reticulum with prominent cisternae, the chromatin of most nuclei becomes decondensed and lipid bodies accumulate to levels observed in cultured adipocytes. Fibroblasts derived from non-adipose tissue do not undergo the same morphological changes when cultured under similar conditions.

Determination of phosphodiesterase I activity in human blood serum.

Phosphodiesterase I (EC 3.1.4.1) activity was detected in normal human blood serum. The enzyme is stable at laboratory temperature for three days, but is inactivated at pH less than 7. The pH for optimum activity increases with the substrate concentration (under the conditions used, from pH 9.0 to 10.2) and, conversely, the Km increases with pH and buffer concentration. The enzyme is inhibited by ethylenediaminetetraacetate but not by phosphate (0.1 mol/liter). We developed a simple quantitative method for its determination, based on hydrolysis of the p-nitrophenyl ester of thymidine 5'-monophosphate and subsequent measurement of the liberated p-nitrophenol at 400 nm in NaOH (0.1 mol/liter). Normal values (mean +/- 2 SD) were determined to be 33 +/- 6.4 U/liter. Preliminary studies indicate that phosphodiesterase I activity is greater than normal in serum of patients with necrotic changes in the liver or kidney or in cases of breast cancer, but not in that of patients with myocardial infarction, bone cancer, lung cancer, or chronic liver cirrhosis.