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Biomedical subjects

M D Johnson

Publications and source records attributed to M D Johnson.

306 records · Page 17Linked to original sources
PubMedDate not supplied

The cardiac, obstetric, and anesthetic management of pregnancy complicated by acute myocardial infarction.

Myocardial infarction (MI) occurring during pregnancy is a rare but potentially lethal event for both mother and fetus, particularly when it occurs in the third trimester or peripartum period. The authors report two cases of MI occurring in the third trimester of pregnancy and review the literature. Management of the acute infarct and the medical, obstetric, and anesthetic considerations in such patients during labor and delivery are discussed. Successful use of percutaneous transluminal coronary angioplasty is described in a patient with evolving MI and ongoing pain. The preferred method of delivery in the pregnant MI patient is addressed, with emphasis on the need for individualization of care and coordination between the cardiac, obstetric, and anesthetic teams. Finally, the authors review the risks of subsequent pregnancy in this patient population.

Adult↗
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Anesthetic management of the pregnant patient with Marfan syndrome.

Two patients with Marfan syndrome who presented for labor and delivery are reviewed. The characteristics of Marfan syndrome and their significance in relation to the physiologic changes due to pregnancy and the implications for anesthetic management are discussed. Marfan syndrome can present with musculoskeletal, cardiovascular, ocular, and pulmonary complications believed to be secondary to an inheritable disorder of connective tissue metabolism. These patients must be carefully evaluated, monitored, and managed during the prepartum and peripartum period. The physiology of pregnancy, particularly the hemodynamic changes, can have catastrophic consequences for the parturient with Marfan syndrome. Serial echocardiographic studies evaluating aortic root size and aortic and mitral valve function are essential during pregnancy. Anesthetic management focuses on minimizing aortic root shear forces and wall stress through invasive monitoring, pharmacologic intervention, and pain treatment.

Adult↗
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General anesthesia for cesarean section in a parturient with a single ventricle and pulmonary atresia.

The successful management of a cesarean section in a parturient with a single ventricle and pulmonary atresia using general anesthesia is discussed. After cyanosis at birth, the patient underwent cardiac catheterization, which showed an apparent severe tetralogy of Fallot, atresia of the main pulmonary artery (PA), and a large patent ductus arteriosus. When she was 7 months of age, a Blalock-Taussig shunt (right subclavian artery to right PA) was done. She remained stable until age 11, when cyanosis increased and exercise tolerance decreased. Recatheterization more clearly defined the lesion: closed shunt, pulmonary valvular atresia, severe ductal stenosis, reduced pulmonary flow, double-outlet right ventricle, and severe hypoplasia of the left atrium, mitral valve, and left ventricle. A Potts shunt (left descending aorta to left PA) was done. Compliance with therapy was poor and follow-up difficult. Exercise tolerance was poor, but the patient remained otherwise stable. At 28 weeks' gestation, this 23-year-old parturient presented with severe congestive heart failure (CHF). After initial therapy with oxygen, bed rest, digoxin, and diuretics, she improved and remained stable for a month. At that time (32 weeks' gestation), CHF worsened. Because the cervix was unfavorable for a vaginal delivery, a cesarean section was planned. The patient was then taken to the operating room electively, and an opioid-based general anesthetic was administered. Both mother and infant did well. This case is presented because the physiology of the patient's lesion and her unusual social history presented challenges for her anesthetic management.

Abnormalities, Multiple↗
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Effects of a beta 1-adrenoceptor agonist, prenalterol, on renal function and renin secretion rate in anesthetized dogs.

Experiments were conducted to examine the effects of prenalterol on renal function and renin secretion in anesthetized dogs. Specifically, we tested whether prenalterol alters renal function directly, or only indirectly as a consequence of a systemic action of the drug. Accordingly, prenalterol was infused into one renal artery for five consecutive 15-min periods, at incremental rates of 0.1, 0.3, 0.9, 2.7, and 8.1 micrograms X kg-1 X min-1. Heart rate and mean arterial blood pressure were recorded, and renal functions and renin secretion rates were measured bilaterally. Direct intrarenal prenalterol infusion caused a 60 bpm increase in heart rate and resulted in marked increases in renin secretion rates from both kidneys. Intrarenal prenalterol infusion also reduced urinary sodium and potassium excretions bilaterally and equally. There were no consistent changes in mean arterial blood pressure, or in glomerular filtration rate or renal blood flow, during prenalterol infusion. We conclude that although prenalterol increases renin secretion rate markedly and may alter renal electrolyte excretion, these effects are not mediated by a direct intrarenal action of the drug.

Adrenergic beta-Agonists↗
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Effects of histamine receptor antagonism on adrenaline-induced changes in blood pressure in intact dogs.

This study was designed to test the hypothesis that histamine may contribute to the vasodepressor response which occurs in response to physiologic increments in adrenaline concentration in intact animals. Accordingly, following a control period of 30 min, adrenaline was infused intravenously for 45 min at a rate of 250 ng/kg per min in 14 anaesthetized dogs (Group I). A second group of eight dogs received an identical adrenaline infusion following complete H1- and H2-histamine receptor antagonism with tripelennamine plus cimetidine (Group II). A time control group of experiments, in which no drugs were infused, as well as groups receiving adrenaline plus either tripelennamine or cimetidine, were also performed. In Group I, adrenaline infusion increased heart rate and reduced mean arterial blood pressure by 10 mmHg (P less than 0.01). Following combined H1- and H2-histamine receptor antagonism (Group II), adrenaline infusion failed to reduce mean arterial blood pressure. However, mean arterial blood pressure was reduced significantly in the groups receiving adrenaline plus only one of the histamine receptor blocking agents. Since only the combined histamine receptor blockade completely eliminated the vasodepressor response to adrenaline, the data suggest that histamine may play a physiological role in the vasodepressor response to circulating adrenaline in the intact animal, and that both H1- and H2-histamine receptors may be involved.

Animals↗
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Modulation of aortic and cardiac G protein alpha subunits and their mRNAs during norepinephrine infusion in rats.

These studies examine the possibility that alterations in the expression of G protein alpha subunits occur during desensitization of adrenergic responses in the cardiovascular system. To desensitize adrenergic receptors, rats were infused with norepinephrine (NE) subcutaneously (0.1 mg/kg/h) for 3 or 6 days using osmotic minipumps. G protein alpha subunits and their mRNAs were then measured in the aorta and heart using selective antibodies and cDNA probes. Infusion of NE for 6 days significantly decreases the levels of Gs alpha, Gi alpha and Go alpha in the aorta. The mRNAs for the alpha subunits are not altered in the aorta after NE infusion for 3 or 6 days indicating that reduced mRNA expression does not account for the decreased proteins. In the atrium and ventricle the levels of Gs alpha decrease after NE infusion for 3 days but then return to control levels by day 6. The levels of atrial and ventricular Gi alpha are unaltered after NE infusion for 3 days but increase significantly by day 6. Go alpha levels do not change in the atrium or ventricle on either day. The level of Gi2 alpha mRNA increases after NE infusion for 6 days and may account for the increased alpha i protein. The levels of the other G alpha mRNAs do not change in the atrium or ventricle. These results demonstrate that expression of G protein alpha subunits is altered during cardiovascular desensitization, raising the possibility that modulation of the alpha subunits may contribute to reduced adrenergic responsiveness.

Animals↗
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Continuous pump pressures cannot be used to identify catheter tip migration into the subarachnoid space.

BACKGROUND AND OBJECTIVES: Migration of an epidural catheter into the subarachnoid space is a potentially lethal complication of continuous epidural anesthesia. We evaluated the use of pump pressure measurement during infusion in detecting such an occurrence. METHODS: Pump pressures at two flow rates (P1 and P10) and epidural space pressure (P0) were measured hourly in eight consecutive ASA Physical Status I parturients receiving continuous epidural anesthesia and compared to those of a patient whose catheter migrated into the subarachnoid space. In addition, total resistance to infusion (Rtot) was calculated as the slope of the least squares regression line linking pressure and flow. Epidural resistance (Repi) was computed as the difference between total resistance and catheter resistance; Repi = Rtot - Rcath. RESULTS: In epidural catheters, average P0 and P10 were 13 +/- 4 mmHg and 23 +/- 4 mm Hg, respectively, and did not change over time. Rtot and Repi averaged 960 +/- 180 RU and 980 +/- 120 RU, respectively. Pump pressures in the subarachnoid catheter were 10 mmHg for P0 and 20 mmHg for P10, while Rtot was 1000 RU. CONCLUSIONS: We conclude that epidural and subarachnoid space resistance is essentially zero and the pump pressure in the system is used to overcome the catheter resistance. Both spaces offer the same total resistance to infusion and, therefore, pump pressure will not change when a catheter migrates into the subarachnoid space.

Anesthesia, Epidural↗
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Anesthetic management of a parturient with myotonia dystrophica: a case report.

We report the case of a 22-year-old parturient with myotonia dystrophica. She underwent two separate intraabdominal surgical procedures in one day, both under lumbar epidural anaesthesia. Management was directed toward prevention of shivering, a known trigger of myotonic crises. Measures used included warm ambient atmosphere, warmed IV fluids, warming blankets and administration of epidural sufentanil, an opioid recently ascribed as an inhibitor of shivering in parturients.

Abdomen↗
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Precordial Doppler monitoring and pulse oximetry during cesarean delivery: detection of venous air embolism.

Venous air embolism (VAE) is a potential but rare complication of cesarean delivery that can be associated with morbidity and death. Uterine sinuses are susceptible to the entrance of air during cesarean delivery. To define the incidence of VAE and its relation to arterial oxygen saturation (SaO2) and consequent electrocardiographic (ECG) changes, a prospective study was undertaken in which precordial Doppler monitoring was conducted during cesarean delivery. Concomitant, SaO2 and ECG were recorded in 78 patients. Fifty-one of 78 (65%) of the subjects had Doppler changes consistent with VAE. Of these, 37 patients (72%) showed a decreased SaO2, (average decline 5.2%). The remainder of the patients with Doppler changes showed no SaO2 change. Twenty of the patients with Doppler changes and decreased SaO2 complained of chest pain and dyspnea. Three of these patients exhibited ECG changes including ST segment depression. Although all ECG changes resolved spontaneously without sequelae, the potential clearly existed for life threatening embolic events. Thus, precordial Doppler monitoring of cesarean delivery patients demonstrated a surprisingly high incidence of Doppler changes consistent with VAE. Some episodes were associated with a significant reduction in SaO2 and rarely with ECG changes.

Cesarean Section↗
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Central hypomyelination associated with congenital hypomyelinating polyneuropathy: report of an autopsied case.

The central nervous system (CNS) findings associated with congenital hypomyelinating polyneuropathy (CHN) are not established due to a paucity of reported post-mortem examinations. In this report we describe the pathologic changes found in the peripheral nervous system and CNS in a 2 1/2-week-old infant with a clinical diagnosis of CHN who died of respiratory failure clinically attributed to phrenic nerve dysfunction. Macroscopic findings included striking hypoplasia of the corpus callosum and anterior commissure, cerebellum, crus cerebri, ventral pons and pyramids. Histologic and immunohistochemical findings included complete absence of myelin staining and myelin basic protein immunoreactivity (MBP-IR) in the cerebral hemispheres, cerebellum, brainstem, cranial nerves and spinal cord despite little or no detectable reduction in numbers of oligodendrocytes. A severe fibrillary astrocytosis was seen at each of these sites. A slight reduction in neurons was identified in the cerebellum and spinal cord but nowhere else in the brain. These findings raise the possibility that deficient or markedly delayed CNS myelination accompanies peripheral hypomyelination in some cases of CHN.

Axons↗
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Production of proto-oncogene expressing control tissues for in situ hybridization and immunohistochemical studies.

There is increasing interest in cellular localization of protooncogene, growth factor, and growth factor receptor gene expression in developing or neoplastic human tissue. Establishment of nucleic acid in situ hybridization (ISH) and immunohistochemical (IH) analyses of these genes, however, is compromised by the paucity of available control tissues which have been shown to express these cancer associated genes. The present study evaluated whether proto-oncogene or growth factor gene expressing human control tissues suitable for ISH and IH studies could be produced from malignant cell lines implanted into irradiated nude mice. Tumors rapidly fixed in parafomaldehyde 2 to 4 weeks after xenograft were found optimal for in situ hybridization and immunohistochemistry. Northern blots of frozen tumors confirmed the expression of specific proto-oncogenes in the tissue and the specificity of cDNA and cRNA probes for those transcripts. Production of control tissue from xenografted cell lines should facilitate establishment and long term quality control of in situ hybridization and immunohistochemical analysis of proto-oncogene or growth factor gene expression in laboratories with limited experience in these techniques.

Animals↗
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Pineoblastoma in a cockatiel.

Pineoblastoma, a primitive neoplasm of pineal gland origin, was diagnosed in a cockatiel based on gross, histopathological, and electron-microscopic findings.

Animals↗
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Effectiveness of the California 1990-1991 tobacco education media campaign.

The California Department of Health Services conducted a $28,600,000 tobacco education media campaign in 1990 and 1991. An independent evaluation of the media campaign featured four waves of data-gathering, one prior to the campaign's beginning and three at intervals thereafter. In all, 29,264 students in grades 4-12 and 6,785 adult smokers provided data for the evaluation. Through telephone interviews for adults and written questionnaires for students, these participants supplied information so that each person could be classified as exposed or unexposed to the media campaign's advertisements. Five criterion variables were used in the evaluation: campaign awareness, tobacco use, smokers' intention to quit, nonsmokers' intention to start, and attitudes toward smoking. Based chiefly on the differences between the results of waves 1 and 4, we believe the media campaign had a number of positive effects on California students. For adult smokers, the results were mixed.

Adolescent↗
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Do anti-smoking media campaigns help smokers quit?

As part of an evaluation of the 1990-91 anti-tobacco media campaign carried out by the California Department of Health Services, a study was conducted among 417 regular smokers who had quit during the period of the media campaign. In brief telephone interviews, all respondents identified up to three events or experiences that had influenced them to quit. In response to uncued questions, 6.7 percent of those interviewed indicated that they had been influenced to quit by an advertisement they had seen or heard on radio, television, or billboards. In response to direct questions about the media campaign, 34.3 percent of the respondents indicated that the media campaign's advertisement had played a part in their decision to quit. Applying the 6.7 percentage to the number of Californians who quit smoking in 1990-91, it can be estimated that for 33,000 former smokers, the anti-tobacco media advertisements were an important stimulus in their quit decision. Multiplying the 34.3 percent by the number of former California smokers who quit in 1990-91, the estimate of former smokers for whom the media campaign's advertisements played at least some part in their decision to quit rises to 173,000 persons. While causal attributions from such investigations should be made with caution, the evidence suggests that the 1990-91 campaign did influence substantial number of smokers in California to quit.

Adult↗
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Chest discomfort associated with liposomal amphotericin B: report of three cases and review of the literature.

Liposomal formulations of amphotericin B are designed to maintain therapeutic efficacy of amphotericin B deoxycholate while reducing its associated toxicities. In three patients chest discomfort occurred during planned 1-hour infusions of liposomal amphotericin B (AmBisome) 3 mg/kg/day during an open-label trial. The first patient experienced chest tightness and difficulty breathing and the second had dyspnea and acute hypoxia, both within 10 minutes of the start of the infusion. The third patient complained of chest pain 5 minutes after the start of two infusions. All symptoms resolved on terminating therapy. Two patients were later rechallenged with slower infusions and tolerated the drug well. A review of the English-language literature revealed only two other case reports of infusion-related chest or pulmonary reactions with the drug, although similar reactions were noted in several reports of clinical trials. Further review of the literature revealed reports of chest and pulmonary adverse events with other liposomal formulations of amphotericin B, liposomal daunorubicin, liposomal doxorubicin, and liposomes. The pathophysiology of such reactions remains unclear, and premedication with diphenhydramine did not completely prevent this reaction in one of our patients. We recommend infusing liposomal amphotericin B over at least 2 hours with careful monitoring for adverse reactions.

Adolescent↗