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Biomedical subjects

P Mills

Publications and source records attributed to P Mills.

At least 55 records · Page 3Linked to original sources
PubMed1997

Sleep apnea, norepinephrine-release rate, and daytime hypertension.

Patients with obstructive sleep apnea (OSA) are often hypertensive, and both apneics and hypertensives are reported to have increased sympathetic nerve activity. We measured plasma norepinephrine (NE) levels, clearance, and release rate among 65 subjects who breathed room air, a hypoxic gas mixture, and the hypoxic mixture combined with intermittent breath holding. Apneics' plasma NE across all three breathing conditions was 307 pg/ml compared with the non-apneics' level of 248 pg/ml (p = 0.017). NE clearance increased from 3.2 l/minute to 3.9 l/minute when subjects breathed a hypoxic gas mixture (p < 0.001). NE clearance was similar among normal controls, apneics, and hypertensives. The rate at which NE was released from sympathetic nerves into the bloodstream was higher among hypertensives but not among apneics while subjects breathed room air. Hypoxia increased the NE-release rate from 892 ng/minute to 1,042 ng/minute (p < 0.001) and increased the NE-release rate more among apneics than non-apneics (p < 0.001). The NE-release rate response to hypoxia and breath holding differed between hypertensives and normotensives (p < 0.001) and between apneics and non-apneics (p < 0.001). Normotensive apneics had the largest increase in NE release during hypoxia. Like other investigators, we found that plasma NE levels were increased among apneics. Calculation of NE-release rate and correction for blood pressure status revealed a more complex situation. Apneics breathing room air had a normal NE-release rate; any increase in sympathetic neuronal NE release could be attributed to apneics who were also hypertensive. However, apneics had a greater NE response to hypoxia. These results suggest that apneics are susceptible to transient increases in sympathetic nervous activity and that hypertensive apneics maintain increased sympathetic nervous release of NE in the daytime.

Adult↗
PubMed1997

Co-induction and laryngeal mask insertion. A comparison of thiopentone versus propofol.

Conditions for insertion of the laryngeal mask airway were assessed in 70 unpremedicated patients comparing the co-induction with midazolam-alfentanil-thiopentone and midazolam-alfentanil-propofol. Following pre-induction doses of midazolam 0.04 mg.kg-1 and alfentanil 10 micrograms.kg-1, patients received equipotent doses of either thiopentone or propofol. Whilst jaw relaxation and ease of laryngeal mask insertion were similar between the two groups, patients receiving propofol were less likely to have undesired responses requiring additional boluses of induction agent (p < 0.05). We conclude that, using these doses, propofol is superior to thiopentone for laryngeal mask airway insertion when using a co-induction technique.

Adolescent↗
PubMed1997

Initial experience with a co-radial bipolar pacing lead.

A new type of endocardial bipolar pacing lead has been designed to overcome the potential drawbacks of the conventional coaxial bipolar pacing lead. We prospectively evaluated the new co-radial bipolar pacing leads (Intermedics Thin-Line), which are thinner (5 Fr vs 6-8 Fr) than standard coaxial bipolar leads. X-ray visibility and lead handling were subjectively assessed (excellent, good, adequate, or poor) at implant; lead impedance, sensitivity threshold, and pacing threshold were measured at implant, then at 1, 3, 6, 12, and 18 months. The results were as follows: 103 patients (51 M; age 63.8 +/- 17.4 years) received 71 atrial (A) and 89 ventricular (V) leads. X-ray visibility was excellent in 59/103; good in 23/103; adequate in 11/103; and poor in 10/103. Overall handling was excellent in 56/71 A and 69/89 V; good in 11/71 A and 18/89 V; adequate in 3/71 A and 1/89 V; poor in 1/71 A and 1/89 V. There were two perioperative complications. At implant: impedance in A and V were 370.1 +/- 74.7 and 501.5 +/- 124.4 omega, sensing thresholds in A and V were 3.0 +/- 1.5 and 9.9 +/- 5.0 mV, pacing thresholds at 0.45 ms in A and V were 0.59 +/- 0.21 and 0.41 +/- 0.15 volt, respectively. At 1, 3, 6, 12, and 18 months of follow-up: no pacing lead related complications were reported; pacing lead characteristics remained outstanding and stable. This new lead appears to have significant clinical advantages over the conventional coaxial bipolar pacing lead. Long-term follow-up is required to confirm its reliability and chronic performance characteristics.

Adolescent↗
PubMed1997

Sympathetic nervous system alterations in sleep apnea. The relative importance of respiratory disturbance, hypoxia, and sleep quality.

Numerous alterations in the sympathetic nervous system have been reported in patients with obstructive sleep apnea. It is unclear whether such alterations can be attributed to the respiratory disturbance itself, the resulting hypoxia, or disruption of sleep. We examined urinary norepinephrine levels in 45 individuals with varying amounts of respiratory disturbance and sleep disruption. All were of similar age (40 to 60 years) and body weight (100 to 160% ideal body weight), and all were free from antihypertensive medications that could influence norepinephrine levels. Twenty-four-hour urinary norepinephrine levels were correlated with respiratory disturbance index (r = 0.39, p < 0.01) and mean oxygen saturation (r = -0.36, p < 0.05). These variables, together with the time in slow-wave sleep, accounted for a statistically significant but modest percentage of the variance in urinary norepinephrine (R2 = 0.19, p < 0.05). However, the variables were so tightly intercorrelated that no single variable independently predicted norepinephrine levels in multiple regression analysis.

Adult↗
PubMed1996

Children's use of counterfactual thinking in causal reasoning.

Research on children's causal thinking has emphasized the perception of temporal and spatial contiguity between cause and effect. However, our causal judgements often involve a contrast between a perceived sequence (A, then B) and a counterfactual case (in the absence of A, then not B). In three experiments, children's capacity for such counterfactual thinking was assessed. In Experiment I, children aged 3-5 years observed a sequence such as A causing B. Subsequently, they replied quite accurately to a question about a counterfactual sequence, for example: "What if A had not occurred, then B or not B?". In Experiment 2, children were asked about two counterfactual antecedents, one that would not have caused B, and one that (like the actual antecedent) would also have caused B. Children differentiated between the two types of antecedent. Finally, in Experiment 3, children heard stories in which the protagonist chose a course of action that led to a minor mishap (e.g., drawing with a black pen and getting inky fingers), having rejected an option that would have prevented it in experimental stories (e.g., using a pencil) or an option that would have led to an equivalent outcome in control stories (e.g., using a blue pen). Children aged 3 and 4 years often cited the failure to adopt another course of action as the cause of the mishap and, particularly in experimental stories, they focused on the rejection of the alternative option. Children's use of counterfactual thinking is discussed in relation to contemporary accounts of causal reasoning.

Child Development↗
PubMed1996

Midazolam co-induction and laryngeal mask insertion.

We have studied the effect of alfentanil and midazolam+alfentanil on the conditions for laryngeal mask airway insertion in patients receiving propofol for induction of anaesthesia. Ninety unpremedicated. ASA 1 or 2 adult patients were randomly allocated to one of three groups: group P received propofol only (2.5 mg.kg-1); group PA received alfentanil (10 micrograms.kg-1) followed by propofol (1.25 mg.kg-1); group PMA received midazolam (0.04 mg.kg-1) and alfentanil (10 micrograms.kg-1) followed by propofol (1.25 mg.kg-1). Further boluses of propofol (0.25 mg.kg-1 every 15 s) were given if the initial dose was inadequate for induction of anaesthesia. Patients in the midazolam+alfentanil group required less propofol (p < 0.001), had better mouth opening (p < 0.001) and fewer undesired responses to laryngeal mask airway insertion (p < 0.001) than the other two groups.

Adult↗
PubMed1996

Phase I study of weekly outpatient paclitaxel and concurrent cranial irradiation in adults with astrocytomas.

PURPOSE: Astrocytomas are extremely resistant to currently available treatments. Cranial irradiation is a mainstay of frontline therapy, but tumor recurrence is nearly universal. Paclitaxel has shown antitumor efficacy against astrocytoma cell lines, and is a potent radiosensitizer. For these reasons, we conducted a phase I study of weekly paclitaxel and concurrent cranial irradiation in patients with newly diagnosed astrocytomas. PATIENTS AND METHODS: Patients with astrocytomas were eligible for this study following initial surgery if they had a Karnofsky performance score (KPS) > or = 60%; normal hematologic, liver, and renal function; and could give informed consent. Beginning on day 1 of treatment, patients received paclitaxel by 3-hour infusion once weekly for 6 weeks, concurrent with standard cranial irradiation. Pharmacokinetic studies were performed on 10 patients. RESULTS: Sixty patients were enrolled; 56 were fully assessable. Forty-eight had glioblastomas (GBMs), 10 anaplastic astrocytomas (AAs), and two astrocytomas. Age ranged from 21 to 81 years (median, 55); KPS ranged from 60 to 100 (median, 70). The paclitaxel dose was escalated from 20 mg/m2 to 275 mg/m2. No clinically significant anemia or thrombocytopenia occurred. Only one patient (175 mg/m2) became neutropenic. Sensory neuropathy was dose-limiting. The maximum tolerated dose (MTD) was 250 mg/m2. Paclitaxel pharmacokinetic profiles in study patients were identical to those of previously reported patients with other solid tumors. CONCLUSION: The MTD of paclitaxel administered weekly for 6 weeks by 3-hour infusion is 250 mg/m2. Since patients with brain tumors often have preexisting neurologic deficits, we suggest 225 mg/m2 as the optimum dose for phase II trials in this group of patients.

Adult↗
PubMed1996

Short communication: Prospective assessment of a new graduated hookwire for the localization of impalpable breast lesions.

The benefits of the addition of site specific variable graduations to a conventional mammographic localizing wire were assessed in a prospective multidistrict study. Six surgeons and five radiologists localized lesions in 31 patients in three District General Hospitals. The advantages of the graduated wire were shown to be greater ease and accuracy of radiological localization with easier surgical excision and a smaller resected breast specimen.

Biopsy↗
PubMed1995

Renal ultrasonography as a tool for detecting dynamic changes in blood pressure.

Renal ultrasonography has been used to assess renal blood flow under pathological conditions. We attempted to determine if sonographically derived renal resistive index measurements would be affected by subtle changes in flow as a consequence of transiently induced mild increases in blood pressure in persons with normal renal functioning. Nine subjects free of structural renal disease were studied with duplex Doppler ultrasonography. Main renal artery resistive indices were determined under resting baseline conditions and in response to graded infusions of phenylephrine sufficient to increase blood pressure by approximately 13/5 mm Hg. Change in blood pressure correlated with the change in main renal artery resistive index (r = 0.254, P < 0.05). Thus, the resistive index varies in association with transient increases in blood pressure and may reflect concurrent alterations in distal resistance under physiologic conditions.

Blood Pressure↗