Sources of interindividual variations in acetaminophen and antipyrine metabolism

Our goal was to compare and contrast in the same normal twins the relative contribution of genetic and environmental factors to large interindividual variations in the metabolism of acetaminophen (APAP) and antipyrine. These drugs were selected because they are biotransformed by different mechanisms. A single oral dose of APAP (10 mg/kg) was given to six sets of monozygotic (MZ) and six sets of dizygotic (DZ) twins. All were normal, nonsmoking, nonmedicated, and male. Among these 24 subjects, there were 300% interindividual variations in rate constants for formation of the sulfate and glucuronide conjugates, as well as in the overall rate constant for APAP elimination. Intratwin variations for each measurement were as large within MZ as within DZ twinships, suggesting that predominantly environmental rather than genetic factors maintained interindividual variations. Two other observations support this conclusion: Intraindividual variations were frequently as large as interindividual variations, and regardless of zygosity for twins living together, intratwin correlation coefficients were almost twice those of twins living apart. Quite different results were obtained when these twins received antipyrine. After a single oral dose of antipyrine (18 mg/kg), 500% interindividual variations in rate constants for formation of the three main oxidative metabolites of antipyrine appeared to be mainly under genetic control. Also for antipyrine and its principal metabolites, intraindividual variations were much smaller than interindividual variations. In contrast to the results with APAP, regardless of zygosity, intratwin correlation coefficients for antipyrine were similar for twins living apart and twins living together. This comparison between APAP and antipyrine metabolism in the same carefully selected normal twins under apparently uniform environmental conditions reveals that interindividual variations in APAP metabolism arise from certain unidentified environmental factors, whereas genetic factors cause the large interindividual variations that occur in antipyrine disposition.

Does naloxone suppress self-stimulation by decreasing reward or by increasing aversion?

Fifty-eight rats were implanted with electrodes in the ventrolateral midbrain central gray from which both self-stimulation reward and/or stimulation-produced analgesia can be obtained. Thirty-nine cases were positive for self-stimulation; of these, 24 also displayed significant stimulation-produced analgesia and 15 did not. Injections of the opiate receptor blocker, naloxone, suppressed self-stimulation by approximately 40% at both analgesic and non-analgesic reward sites. Since naloxone failed to act preferentially at analgesic reward sites, the hypothesis that naloxone suppresses self-stimulation primarily by antagonizing endorphin-mediated analgesia, and thereby increasing the aversive properties of the brain stimulation, was not supported. Rather, the data are consistent with the hypothesis that naloxone suppresses self-stimulation by antagonizing endorphin-mediated reward.

Value of high-resolution computerized tomography in localizing diseased parathyroid glands

Eighteen patients with hyperparathyroidism underwent high-resolution computerized tomography of the neck and superior mediastinum to assess the accuracy of the method in localizing diseased parathyroid glands preoperatively. The tomograms were correlated with surgical and pathological findings. Four scans were technically unsatisfactory. Of the remaining 14 scans, 8 showed an enlarged parathyroid gland; in 7 cases, the scan correctly identified the location of the diseased gland while in 1 case, the side of the lesion was incorrect. The other six scans did not show an abnormal parathyroid. These glands varied in size from 0.05 to 5.0 cm3 at the time of pathological examination. Three patients were undergoing re-exploration for persistent disease; technically acceptable scans were obtained in two and, in both, the location of the adenoma was correctly identified. Excluding patients with technically unsatisfactory scans, this technique has a sensitivity of 50% (7/14) and a false-negative rate of 43% (6/14) independent of gland size. However, in the eight scans interpreted as positive, the correct side of the lesion was localized in 7 (88%). This technique is not recommended for routine preoperative localization but may be of value in re-exploration for persistent disease.

Auditory brain-stem responses in hydrocephalic patients

Auditory brain-stem response (ABR) was measured in 40 patients (80 ears) with confirmed hydrocephalus. Eighty-eight percent of these patients showed some form of ABR abnormality. Responses indicative of brain-stem dysfunction consisted of prolonged I-V interwave latency (38%), reduced V/I amplitude ratio (33%), and abnormalities in wave-shape of components III (27%) and V (53%). In addition, 70% of the patients had elevated ABR thresholds; 45% had responses in excess of 20 dB HL and the remaining 25% had no ABR activity. The etiology of the hydrocephalus, head circumference and brain-stem symptoms were not associated with particular ABR abnormalities. Communicating hydrocephalus correlated significantly with both prolonged I-V conduction time and absence of ABR activity, compared with non-communicating hydrocephalus. Four of the 9 patients retested showed ABR improvement on follow-up; one patient showed deterioration. The results were compared to our prior studies of ABR in 60 post-meningitic patients and in 100 severely neurologically impaired institutionalized children in whom the incidence of intrinsic brainstem abnormalities was one-third and two-thirds that of the hydrocephalic group, respectively. The results of this study suggest that ABR can be used to document clinically unsuspected brain-stem pathology that may accompany hydrocephalus. Auditory brain-stem dysfunction is likely to complicate the assessment of hearing sensitivity in hydrocephalic patients.

Salvage of a severely ischemic limb by arteriovenous revascularization: a case report

Severe ischemia in a limb that cannot be revascularized almost inevitably leads to gangrene and eventual amputation. For decades, surgeons have considered utilizing the venous system to revascularize ischemic tissue in numerous areas, including the lower limb, but with very limited success. This report documents the successful revascularization of a severely ischemic pregangrenous limb with a bypass graft from the femoral artery to a tibial vein. The authors believe this is the first clinical report of salvage of an ischemic limb by this approach.

Absent auditory brain stem response: peripheral hearing loss or brain stem dysfunction?

Interpretation of auditory brain stem response (ABR) findings can be problematic in cases where waves III and V are absent. Such findings can be attributed to profound hearing loss, brain stem neuropathology, or both. Over a 3-year period, 48 patients with no known brain stem damage and on whom audiologic data were available were found to have no response by ABR or absent waves III and V. Severe to profound hearing loss was documented in 38 cases, audiometric data were equivocal in 3 cases, and 7 patients showed pure tone sensitivity ranging from normal hearing to moderate impairment. Thus 15% had better hearing sensitivity than might have been expected from their ABR findings. Each of these patients also exhibited abnormal acoustic reflex findings. We report the electrophysiological (ABR, MLR, acoustic reflex), medical (history, neurological, EEG, CT scan) and behavioral (audiometric, speech and language, learning disabilities, psychological) data which characterize this group of patients.

Psychosocial adaptation of children and their parents to hospital and home hemodialysis

Psychosocial adaptation of 20 children and adolescents treated by regular hemodialysis and their parents was analyzed by detailed semistructured interviews and questionnaires. The results in 10 patients treated in the centre and 10 followed at home were compared. The burdens of patients and parents induced by therapy as well as compliance, educational aspects and school activity in the treated children are described. Home dialysis usually provoked more fears of complications and aggressive feelings in patients and stress in parents but was superior to centre treated patients regarding social contacts and school activity of patients. From the data obtained, a comprehensive programme of psychosocial care for children with end-stage kidney disease was derived, including detailed instruction for parents and teachers of children on regular dialysis treatment.

Spontaneous rupture of the bladder. A case report

A case of spontaneous rupture of the bladder is described. The patient was a 35-year-old woman presenting with an unusual clinical pattern of peritonitis. She underwent surgery 7 days after the onset of symptoms, and recovered after repair of the rupture. A review of the literature is given.

The hearing-impaired infant: patterns of identification and habilitation

The 1982 Position Statement by the Joint Committee on Infant Hearing recommends that infants at risk for hearing impairment be screened by 3 mos of age and that the diagnostic process be completed an habilitation begun by 6 mos of age. How close to this ideal actual practice comes in an urban setting is the subject of this study, Data on 88 infants referred to a hospital-based parent-infant program were retrospectively examined to determine the occurrence of risk factors and at what ages: (1) hearing loss was first suspected, (2) hearing loss was diagnosed, and (3) habilitation was initiated. Results indicate that over one-quarter of all hearing-impaired infants will not manifest any of the risk factors proposed in the 1982 Position Statement and that regardless of whether the infant graduates from a neonatal intensive care unit or well-baby nursery, the median age for enrollment in a parent-infant program is a year or more later than the 1982 recommendation.

Follow-up of infants screened by auditory brainstem response in the neonatal intensive care unit

Auditory brainstem response screening at 40 and 60 dB was conducted in 100 infants in the neonatal intensive care unit to determine initial failure rate and prevalence of abnormality on follow-up. Of our NICU population, 20% failed one or both of the screening levels: 9% failed at 60 dB in both ears, and 11% failed at 40 dB in one or both ears. On follow-up, half of the 60 dB failure group were found to have sensorineural or conductive impairment and represent the 2% to 4% prevalence of serious otologic-audiologic problems generally found in an NICU population. Subsequent improvement (reversal) of the retest ABR records of the remaining infants in the 60 dB failure group was thought to be related to neural changes in the brainstem associated with recovery from hypoxic episodes. A transient or reversible conductive deficit appeared to account for the majority of failures at 40 dB. We recommend the screening protocol be expanded to include threshold and latency measures in infants who fail the initial screening. The transient nature of many ABR abnormalities makes postdischarge ABR, otologic, audiologic, and neurologic examinations mandatory before any inferences are made about hearing loss or neurodevelopmental disorders.

Pericarditis as a manifestation of histoplasmosis during two large urban outbreaks

During two histoplasmosis outbreaks in Indianapolis 45 patients presented with pericarditis. The pericarditis occurred as a late complication in individual patients and during the outbreak. Risk factors for this complication included young age, immunocompetence, and male sex in persons between 20 and 39 years old. Intrathoracic adenopathy was present in 66% of cases. Since cultures were uniformly negative, including pericardial fluid or tissue from nine patients, serologic studies provided the basis for diagnosis. Although the course was usually benign, nine patients presented with tamponade and another with constrictive pericarditis. Prompt response to antiinflammatory medications and failure to identify H. capsulatum in the pericardial fluid or tissue support a noninfectious, inflammatory mechanism for this complication. Of 20 patients reexamined 1 year later, none had evidence of constriction but three had pericardial thickening by echocardiography. Histoplasmosis should be considered in patients with pericarditis from endemic areas, particularly when associated with intrathoracic adenopathy.

Auditory brainstem responses in infants recovering from bacterial meningitis. Audiologic evaluation

Auditory brainstem response (ABR) was used to assess possible hearing loss in 60 patients recovering from bacterial meningitis. The ABR results were consistent with either unilateral or bilateral hearing loss in 35% of the cases tested. Of these, 15% were conductive-type hearing loss. Twelve percent had sensorineural hearing losses and normal brainstem function. The remaining 8% had elevated ABR thresholds coincident with findings suggestive of neuropathology of the auditory brainstem pathways. A case of reversible sensorineural hearing loss was documented. Various clinical and demographic factors were examined to determine their predictive value with regard to hearing loss. As expected, otitis media occurred significantly with conductive hearing loss. Type of pathogen (Streptococcus pneumoniae) and hospitalization greater than two weeks were significantly correlated with sensorineural hearing loss. As meningitis typically affects young children who are difficult to test with conventional audiometry, ABR provides an effective means of testing hearing in this population.

Persistent skin and nail infection by an exotic fungus, Hendersonula toruloidea

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Auditory middle latency responses (MLRs) in patients with cortical lesions

Auditory middle latency response (MLRs) and auditory brain stem responses (ABRs) were simultaneously recorded in 24 patients with cortical lesions primarily affecting the temporal lobes. Site of lesion was documented by computerized tomography (CT) scan and behavioral profiles assessing language and other higher cortical functions were obtained. In patients with normal ABRs and either left or right hemisphere lesions, MLR components Na and Pa obtained at the vertex were of normal shape and latency. Exceptions to this occurred in 2 patients: one with bilateral temporal lobe lesions, the second with an infraventricular left temporal lobe lesion extending into the thalamic radiations. Although Na and Pa shape and latency were for the most part unaltered, Pa amplitude tended to cluster at the low end and below normal values. MLR recorded in the coronal plate showed Pa amplitude to be attenuated or absent over the damaged temporal lobe relative to the vertex or the intact hemisphere. This finding contrasts with data from normal subjects where Pa amplitude is largest at the vertex and essentially symmetrical about the temporal lobes. Patients showing an atypical amplitude distribution tended to have lesions involving auditory cortex and adjacent white matter projections. No obvious correlations between MLR abnormalities and behavioral findings regarding receptive and expressive language processes were found. Pa appears to be affected by temporal lobe lesions involving auditory cortex and thalamic projections. Our findings support the hypothesis that Pa is bilaterally generated by two symmetrical, vertically oriented dipole sources located about the temporal lobes.

Auditory brain stem response (ABR) in unilateral hearing loss

Auditory brain stem responses (ABRs) wee reported with two groups of patients with confirmed and suspected unilateral hearing loss. Evidence of acoustic crossover in click stimuli when the difference in click thresholds for the two ears exceeds approximately 60 db is presented. In such a circumstance, the ABR presumably elicited from the test ear can, in fact, be a reflection of a crossover response from the non-test ear. In clinical practice, appropriate contralateral ear masking should be employed when ABR audiometry is carried out with infants and adults with suspected unilateral hearing loss.

Increase in plasma norepinephrine during prazosin therapy for chronic congestive heart failure

To investigate the mechanism of pharmacodynamic tolerance reported to occur during prazosin therapy of chronic congestive heart failure, we measured plasma norepinephrine, plasma epinephrine, plasma renin activity (PRA) and plasma aldosterone, as well as hemodynamics in eight patients with chronic congestive heart failure, functional class III and IV (NYHA), before and during 10 weeks of prazosin therapy. Initially, prazosin therapy produced significant hemodynamic improvement, but no significant changes were noted in norepinephrine, epinephrine, plasma renin activity or aldosterone. During ambulatory therapy, fluid retention developed in four patients, and three of them had symptoms or clinical evidence of congestive heart failure for which they required an increase in diuretic or prazosin therapy. Plasma norepinephrine levels for the whole group were significantly higher after four weeks of therapy (p less than 0.01). Repeat inpatient studies after 10 weeks showed a persistent hemodynamic response to prazosin in seven patients. One patient demonstrated complete hemodynamic tolerance whereas three others showed partial tolerance. In these four patients the cardiac output increased only to 3.78 +/ 1.17 liters/min compared to 5.04 +/- 2.11 liters/min during initial prazosin therapy. Plasma norepinephrine increased further and levels were significantly higher for the whole group than before prazosin therapy (p less than 0.05). No significant changes in epinephrine, plasma renin activity or aldosterone were demonstrated. This increase in plasma norepinephrine suggests that the sympathetic nervous system could be involved in the pharmacodynamic tolerance to prazosin therapy in congestive heart failure. Further studies are necessary to extend these results.

Acute and chronic haemodynamic effects of prazosin in left ventricular failure

We evaluated the acute and chronic effects of prazosin treatment in 11 patients with chronic congestive heart failure, NYHA functional class III and IV. Before treatment mean arterial pressure averaged 100 +/- 15 mmHg, left ventricular filling pressure 29 +/- 11 mmHg, and systemic vascular resistance 2372 +/- 1121 dynes s cm-5. Prazosin administration resulted in haemodynamic improvement in all but one patient with significant lowering of the mean arterial pressure, left ventricular filling pressure, and systemic vascular resistance. Nine patients completed a 10-week course of ambulatory treatment. Five patients remained improved while four developed significant fluid retention; two of these had transient exacerbation of congestive heart failure. This was controlled by increasing diuretic and/or prazosin treatment. After 10 weeks all nine patients had advanced to NYHA functional class II. Repeat haemodynamic measurements disclosed complete haemodynamic tolerance in one patient while three other patients showed partial tolerance with a lower cardiac output (CO) response to prazosin. The nine patients, however, still showed significant lowering of the mean arterial pressure, left ventricular filling pressure, as well as the systemic vascular resistance. Though pharmacodynamic tolerance was noted in four out of nine patients, beneficial clinical and haemodynamic effects could be demonstrated after 10 weeks of prazosin treatment in most patients. Further evaluation of the long-term effects of prazosin in chronic congestive heart failure is warranted.

Pitfalls in bedside diagnosis of severe acute mitral regurgitation. Clinical and hemodynamic features

We describe five patients with severe acute mitral regurgitation in whom delay in diagnosis contributed to their fatal outcome. Either a soft systolic murmur was not heard or was misinterpreted, or hemodynamic confirmation by bedside right heart catheterization was unduly delayed. Pitfalls in recognition of hemodynamic patterns further postponed diagnosis and therapy. The diagnosis should be suspected when, in the proper setting, significant hemodynamic deterioration occurs, and is confirmed by bedside balloon flotation catheterization. Large V waves, characteristic of acute mitral regurgitation, may be overlooked unless one pays attention to the pulmonary artery systolic pressure tracing, which often has a triangular shape and may be double peaked; the V wave occurs later causing the second peak. Careful balloon inflation will demonstrate the large V waves. Timing with simultaneous ECG recordings allow this differentiation. Pulmonary hypertension with normal pulmonary vascular resistance is typical.