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Biomedical subjects

T A O'Connor

Publications and source records attributed to T A O'Connor.

At least 19 recordsLinked to original sources
PubMed1999

Efficacy of repeat intravenous dosing of ondansetron in controlling postoperative nausea and vomiting: a randomized, double-blind, placebo-controlled multicenter trial.

STUDY OBJECTIVES: To compare repeat intravenous (i.v.) dosing of ondansetron 4 mg with placebo for the treatment of postoperative nausea and vomiting (PONV) in patients for whom prophylactic, preoperative ondansetron 4 mg i.v. was inadequate DESIGN: Randomized, double-blind, placebo-controlled study. SETTING: Ten outpatient surgical centers in the United States. PATIENTS: 2,199 male and female ASA physical status I, II, and III patients > or = 12 years old scheduled to undergo outpatient surgical procedures and receive nitrous oxide-based general anesthesia. INTERVENTIONS: Ondansetron 4 mg i.v. was administered to all patients before induction of general anesthesia. Patients who experienced PONV or requested antiemetic therapy within 2 hours after discontinuation of inhaled anesthesia were randomized (1:1) to either a repeat i.v. ondansetron 4 mg dose or placebo. MEASUREMENTS AND MAIN RESULTS: Of the 2,199 patients prophylactically treated with ondansetron 4 mg before anesthesia induction, 1,771 (80.5%) did not experience PONV or request antiemetic therapy during the 2 hours following discontinuation of anesthesia. Of the 428 patients who experienced PONV or requested antiemetic therapy during the same period, and were randomized to additional treatment (214 randomized to ondansetron, 214 randomized to placebo), the incidence of complete response (no emesis, no rescue medication, no study withdrawal) was similar for both ondansetron-randomized and placebo-randomized groups for the 2-hour (34% and 43%, respectively, p = 0.074) and 24-hour (28% and 32%, respectively, p = 0.342) postrandomization study periods. Repeat ondansetron dosing was not more effective than placebo in controlling either postoperative emesis or the severity/duration of postoperative nausea. The administration of an additional dose of ondansetron 4 mg postoperatively did not result in an increased incidence of adverse effects. CONCLUSIONS: In patients for whom preoperative prophylaxis with ondansetron 4 mg i.v. is not successful, a repeat dose of ondansetron 4 mg i.v. in the postanesthesia care unit does not appear to offer additional control of PONV.

Adolescent↗
PubMed1996

In vitro binding of iron with the cation-exchange resin sodium polystyrene sulfonate.

STUDY OBJECTIVE: To investigate the ability of the cation exchange resin sodium polystyrene sulfonate to bind iron from ferrous sulfate solutions, along with the effects of pH on binding. METHODS: We performed a series of in vitro experiments in which various concentrations of iron and sodium polystyrene sulfonate were combined and free ferrous iron was measured with the use of a colorimetric assay. RESULTS: Sodium polystyrene sulfonate bound iron from ferrous sulfate solutions at pH 2 and pH 7. Slightly less binding of free ferrous iron was demonstrated in experiments performed at pH 7 than in those performed at pH 2. At pH 2, 98% of iron was bound, at pH 7, 95% of iron was bound. CONCLUSION: Sodium polystyrene sulfonate may be a useful therapy in acute iron poisoning once safety and efficacy are determined with the use of in vivo models.

Cation Exchange Resins↗
PubMed1994

Mixed venous oxygenation in critically ill neonates.

OBJECTIVE: To describe the typical ranges for central venous oxygen saturation and PO2 in a group of critically ill neonates and the relationship of these measurements to measurements of arterial oxygenation and indicators of oxygen supply and demand. DESIGN: Survey. SETTING: Newborn intensive care unit (ICU) in a children's hospital. PATIENTS: Eighteen newborn infants (1 to 3 days old) who required mechanical ventilation for respiratory diseases, but who were hemodynamically stable and in acid-base balance. INTERVENTIONS: Umbilical artery and right atrial catheterization were performed, allowing simultaneous blood gas sampling. MEASUREMENTS AND MAIN RESULTS: Simultaneous umbilical arterial and right atrial blood gas measurements were analyzed (n = 100). Mean mixed venous oxygen saturation was 83.3% and mixed venous oxygen tension 37.8 torr (5.1 kPa). The mixed venous oxygen saturation correlated well with the arterial-venous oxygen content difference (C[a-v]O2) and fractional oxygen extraction, r = -.77 (r2 = .59) and -.85 (r2 = .72), respectively (p < .0005). Poor correlation was found between the mixed venous oxygen saturation and arterial oxygen saturation values. Two cases are presented in which measurements of mixed venous oxygenation led to recognition of apparent tissue hypoxia earlier than did measurements of arterial oxygenation. CONCLUSIONS: We conclude that measurement of central venous oxygenation in ill neonates may reflect more accurately the oxygen supply and demand status of the neonate than measurement of arterial oxygenation alone.

Arteries↗
PubMed1993

Penile agenesis associated with urethral and bilateral renal agenesis.

Penile agenesis is a rare anomaly, with an estimated incidence of 1 in 30 million. Most cases are compatible with life but require early surgical intervention. This case is unusual in that there was an associated agenesis of the kidneys and urethra leading to fatal oligohydramnios sequence with pulmonary hypoplasia.

Abnormalities, Multiple↗
PubMed1993

Decreased incidence of intracranial hemorrhage using cephalic jugular venous drainage during neonatal extracorporeal membrane oxygenation.

Intracranial hemorrhage (ICH) remains one of the more common serious complications of extracorporeal membrane oxygenation (ECMO) in neonates. In 1990 this center began routine use of cephalic jugular venous drainage during neonatal ECMO to augment blood return to the ECMO pump and potentially decrease the incidence of ICH by decreasing cerebral venous pressure. Thirty-four ECMO cases utilizing cephalic jugular venous drainage were compared with the previous 34 ECMO cases. The incidence of ICH decreased from 35% (12/34) to 6% (2/34) when neonates without cephalic jugular venous drainage are compared with those being subject to this technique (P < .01). No differences were found between the two groups in gestational age, birth weight, duration of ECMO, survival, platelet counts, activated clotting times, or incidence of other bleeding complications. Cephalic jugular venous drainage during neonatal ECMO appears to be safe and may decrease the incidence of ICH.

Catheterization, Central Venous↗
PubMed1993

Mean platelet volume during coagulase-negative staphylococcal sepsis in neonates.

Coagulase-negative staphylococci are the most common cause of late-onset septicemia in neonates in intensive care nurseries. Clinical and laboratory diagnosis of infection with coagulase-negative staphylococci can be difficult. The authors reviewed serial mean platelet volumes of 18 infants in whom coagulase-negative staphylococci sepsis developed and found a significant increase in the mean platelet volume at the time of diagnosis and a return to baseline after resolution of the infection. The increase in mean platelet volume occurred although thrombocytopenia developed in only two of the infants and no difference was found in the mean platelet counts before and at the time of diagnosis of the infection. This finding may be a useful adjunct to the current laboratory tests used to diagnose coagulase-negative staphylococci sepsis in neonates.

Bacteremia↗
PubMed1993

Cephalic jugular venous blood gas measurement during neonatal venoarterial extracorporeal membrane oxygenation.

Cannulation of the cephalic portion of the right internal jugular vein during extracorporeal membrane oxygenation (ECMO) allows for increased venous return flow to the circuit. This procedure also allows access to venous drainage from the brain. We reviewed data from simultaneous blood gases obtained from the cephalic jugular vein and the mixed venous return in 5 neonates during venoarterial ECMO. Cephalic venous pO 2 values were significantly lower than mixed venous pO 2 values (P less than .001). The values for pH and pCO 2 did not vary between the sites. Our experience with 34 infants using cephalic jugular drainage is reviewed. Since the institution of right jugular venous drainage, the intracranial hemorrhage rate in neonates undergoing ECMO at our center has decreased from 34% to 6% (p less than .01).

Analysis of Variance↗
PubMed1992

Trisomy 16p in a liveborn infant and review of trisomy 16p.

We report on an infant boy with duplication of part of 16p and partial deficiency of 9p: 46,XY, -9, + der(9)t(9;16)(p24;p13.1)mat. The child has the typical phenotype of dup(16p) even though the extra piece of 16p is small (16p13.1----pter). Manifestations include severe developmental delay, rounded face, sparse hair, ear anomalies, hypertelorism, cleft soft palate, a thin vermilion border of the upper lip, and left renal dysgenesis. We review 16p duplications.

Abnormalities, Multiple↗
PubMed1992

Bilirubin encephalopathy in a term infant after planned home delivery.

A term infant was delivered at home by his father after a pregnancy which involved no organized medical care. By the third day of life the infant developed fever, poor feeding and severe jaundice. The infant was found to have a serum indirect bilirubin of 49 mg/dl secondary to isoimmune hemolytic anemia due to anti-c antibody. The infant survived but suffers from clinical manifestations of kernicterus.

Adult↗
PubMed1992

Arterial red cell indices in preterm and term infants at birth.

Baseline arterial red cell indices were determined at birth in 105 infants of various gestational ages. These arterial samples were obtained through an umbilical artery catheter or radial artery puncture from a selected group of patients who were evaluated for respiratory distress or possible infection. The red cell distribution width, a quantitative measure of heterogeneity of red cells in the peripheral blood, was consistently elevated, revealing a physiologic state of anisocytosis in the newborn. This new information has provided a useful baseline reference for normal red cell indices from arterial blood in neonates in the first 24 hours of life.

Arteries↗
PubMed1989

Olfactory neuroblastoma.

Fifteen patients with olfactory neuroblastoma were treated during the 17-year period of 1969 to 1986. Data was analyzed with respect to age at presentation, sex, presenting signs and symptoms, stage, and results of treatment. Age ranged from 4 to 67 years with the median age being 27 years. Median follow-up was 8 years. Local control was achieved in nine of nine patients or 100% with successful surgical resection, i.e., minimal residual disease, followed by postoperative radiation therapy (45 to 65 Gy) was employed. There were no distant failures when the primary site was controlled. Regional lymph node metastases were infrequent: only 13% (two of 15 patients) presented with positive nodes. Three of four patients treated initially with surgery alone had a local recurrence, two of which were successfully salvaged by combined therapy. There were four patients treated with radiation therapy alone: three had persistent disease after radiation therapy, and one patient was controlled with 65 Gy. Olfactory neuroblastoma has a propensity to recur locally when treated with surgery alone. The authors' experience suggests excellent local control can be achieved with surgery immediately followed by radiation therapy. Thus the authors recommend planned combined treatment for all resectable lesions.

Adolescent↗
PubMed1986

Mesencephalic trigeminal sensory neurons of cat: axon pathways and structure of mechanoreceptive endings in periodontal ligament.

We injected 3H-proline into cat brainstem in order to label the entire mesencephalic trigeminal nucleus (Mes-V) for autoradiographic analysis of the size and pathways of Mes-V sensory axons and for microscopic study of Mes-V receptor structure in dental tissue. Labeled sensory axons were found in the trigeminal motor and sensory tracts and roots; approximately equal numbers of axons were found in both roots. The sensory root and all three divisions of the trigeminal nerve contained larger Mes-V axons than the motor root. Labeled Mes-V axons were found at the ganglion in the dorsomedial (infratrochlear) branch of the ophthalmic nerve but not in the ventrolateral branch. The mean diameter of Mes-V axons in periodontal ligament was 4.0 +/- 1.9 micron compared to 7.3 +/- 2.1 micron in maxillary and mandibular nerve, suggesting axonal arborization prior to innervation of ligament. Mes-V receptors in dental tissue were confined to ipsilateral periodontal ligament close to the root apex, with greater innervation on the posterior side. Receptor incidence was moderate for most teeth; however, maxillary first and second incisors and maxillary and mandibular canines had focal areas with remarkably dense innervation. No labeled axons were found in pulp of any ipsilateral teeth, and none was found in any contralateral dental tissue. EM-autoradiography demonstrated that Mes-V axons form unencapsulated Ruffini-like mechanoreceptors in periodontal ligament. The preterminal axons were small and myelinated. Neighboring bundles of unmyelinated axons and rare encapsulated endings were not labeled. The labeled mechanoreceptors branched to varying degrees among the ligament fibers; they contained numerous mitochondria and glycogen particles, as well as some vesicles and rare multivesicular bodies. They were surrounded by special Schwann cells that formed one or several layers around the ending. The endings were exposed to the basal lamina at numerous sites and occasionally extended fingers beyond the lamellar Schwann cells to contact ligament collagen.

Animals↗
PubMed1985

Intracranial potentials correlated with an event-related potential, P300, in the cat.

Intracranial recordings of long-latency, event-related potentials were obtained from paralyzed, artificially respirated cats. A modified oddball paradigm was employed in which cats were presented with a randomized series of two tones, a 'frequent' 4 kHz stimulus and a 'rare' 1 kHz stimulus. A tail shock was administered 700 ms after onset of the rare tone. Under these circumstances the stimulus elicited a positive component at the vertex similar to the human P300. Intracranial potentials associated with the rare tone usually manifested components of greater amplitude than did potentials associated with the frequent tone. A positive component occurring in latency between 200 and 350 ms only accompanied the presentation of the rare stimulus. The P300 component, which was positive at the dura, appeared as a negative component within a few millimeters of the surface over a wide area of the marginal and suprasylvian gyri. Changing the probability of the rare stimulus resulted in a reduction in the amplitudes of both the intracranial negative component and the P300 recorded at the skull. Components of large amplitude associated with the rare stimulus were obtained from the region of the hippocampus. These components reversed polarity, sometimes more than once, as the electrode was advanced. Substantial latency differences were often observed between the P300 recorded at the skull and P300-like intracranial components associated with the rare stimulus. These results suggest that the cortices of the marginal and suprasylvian gyri and the hippocampal region contribute to the generation of the cat P300.

Animals↗
PubMed1984

Postnatal functional development of the dorsal and posteroventral cochlear nuclei of the cat.

The postnatal development of firing patterns and response areas was determined for single neurons in the dorsal (DCN) and posteroventral ( PVCN ) cochlear nuclei of the kitten. Extracellular, single-unit responses to pure-tone stimulation were recorded in ketamine and sodium pentobarbital anesthetized kittens between the ages of 5 and 52 days. Within the first two weeks of postnatal life threshold is high, first-spike latency is long, and maximal discharge rate is low as compared to older kittens and adult cats. Prior to the end of the second postnatal week the tone-evoked temporal discharge patterns that characterize neurons of the DCN and PVCN in the adult cat are routinely recorded. These patterns, which appear within the first 50 ms of tonal stimulation, include the so-called " primarylike ," "chopper," " pauser ," "buildup," and "onset" types and their variants. In animals younger than about 10-12 days of age, the driven activity that occurs later than about 50 ms after stimulus onset often is not sustained, but breaks up during the stimulus into bursts that are separated by intervals of about 100-150 ms. Also within the first two weeks of postnatal life, many of the response-area properties of DCN and PVCN neurons are similar to those recorded in adult cats. The excitation and inhibition found within the so-called type II/III, type IV, and type V response areas of the adult occur in this early postnatal period. We conclude that many of the cellular mechanisms that underlie the temporal firing patterns and the organization of the response areas of DCN and PVCN neurons are active in the growing, differentiating cochlear nuclei and that the emergence of these mechanisms does not depend on afferent activity generated in the cochlear and auditory nerve by the animal's acoustic environment. Furthermore, if temporal firing patterns and response-area profiles remain relatively constant over the life span of the animal, then so must the spatial and temporal relationships of the inputs that produce and maintain them as these neurons, and the circuits of which they are a part, grow in size and complexity.

Action Potentials↗