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Biomedical subjects

P Breen

Publications and source records attributed to P Breen.

11 recordsLinked to original sources
PubMed2005

Haemodynamic study examining the response of venous blood flow to electrical stimulation of the gastrocnemius muscle in patients with chronic venous disease.

OBJECTIVES: The aim of this study was to explore the option of stimulating calf muscle contraction through externally applied neuromuscular electrical stimulation (NMES) and to measure venous blood flow response to this stimulation. METHODS: Ten patients with class 6 chronic venous disease (CEAP clinical classification) were recruited. Measurements of peak venous velocities in the popliteal vein were recorded by Duplex scanning in response to six test conditions; 1. Standing, 2. Voluntary calf muscle contraction, 3. Standing with NMES applied, 4. Standing with compression bandaging applied to the leg, 5. Voluntary calf muscle contraction with compression bandaging applied to the leg, 6. Stationary with compression bandaging applied to the leg and NMES applied. Comfort assessment was completed using visual analogue scales at each test stage and on study completion each patient completed a short structured interview to determine comfort and acceptability of NMES. Statistical analyses were carried out using SPSS, Version 9. Non-parametric testing was used in all analyses using the Wilcoxon Signed Ranks Test for paired samples. RESULTS: There was a significant increase in venous velocities on voluntary contraction of the calf muscle (median resting vel 7.3 cm/s; voluntary contraction median 70 cm/s) and with the introduction of NMES, both with compression (median velocity 15 cm/s, p = 0.005 Wilcoxon) and without compression (median velocity 13 cm/s, p = 0.005 Wilcoxon). The greatest increase with NMES was when combined with compression bandaging. All patients reported the stimulus as an acceptable treatment option with 90% reporting NMES as comfortable. CONCLUSIONS: Healing rates in venous ulceration with the application of compression bandaging remain between 50 and 70%. This study shows a positive haemodynamic response to NMES. Further research is needed to quantitatively measure the effect of NMES on ulcer healing.

Chronic Disease↗
PubMed2004

Locked-in syndrome: a catastrophic complication after surgery.

We describe the locked-in syndrome in a 31-yr-old patient after right upper lobectomy for suspected metastasis. After surgery, vertical eye movement was her only means of communication. She remained in a 'locked-in' state for 7 months before dying. Post-mortem examination showed extensive metastatic tumour deposition in the ventral pons. We discuss the clinical features of this syndrome and factors that may affect onset, diagnosis and management.

Adult↗
PubMed2004

Timing of high-risk vascular surgery following coronary artery bypass surgery: a 10-year experience from an academic medical centre.

Major non-cardiac surgery within 40 days of coronary angioplasty with stenting has high cardiac complication rates. We have performed a case-control study to determine whether the risk of vascular surgery might have increased in recent survivors of coronary artery bypass surgery (CABG). Using our vascular database from 1990 to 1999, we matched the cases who had vascular surgery within a month of CABG with controls by pre-operative comorbidities of diabetes mellitus, history of myocardial infarction (MI), history of congestive heart failure (CHF), and chronic renal insufficiency and compared the incidence of peri-operative MI, CHF, death, and other complications. Compared to case-matched controls, patients who underwent vascular surgery within a month of CABG suffered significantly greater mortality (20.6% vs. 3.9%, p < 0.005). The incidence of non-fatal cardiac complications was not significantly different between the groups. We conclude that the risk of mortality may be significantly greater in patients undergoing major vascular surgery within a month of CABG.

Aged↗
PubMed2002

The effects of fenoldopam on renal function in patients undergoing elective aortic surgery.

BACKGROUND AND OBJECTIVE: Postoperative renal impairment is a recognized complication of infrarenal aortic cross-clamping. Our hypothesis was that the renal vasodilating and natriuretic effects of fenoldopam mesylate, a selective dopamine (DA1) agonist, would preserve renal function in patients undergoing elective infrarenal aortic cross-clamping. METHODS: A prospective, randomized, double blind controlled clinical trial was performed. Twenty-eight ASA II-III patients undergoing elective aortic surgery requiring infrarenal aortic cross-clamping were studied. According to random allocation, patients received either fenoldopam (0.1 microg kg(-1) min(-1)) or placebo intravenously prior to surgical skin incision until release of the aortic clamp. Plasma creatinine, creatinine clearance, urinary output, fractional excretion of sodium, and free water clearance were measured: (a) prior to admission to hospital; (b) during the period from insertion of the urinary catheter until application of the aortic cross-clamp; (c) during the period of aortic cross-clamping; (d) 0-4 h, and (e) 4-8 h after release of the clamp and on days 1, 2, 3, and 5 postoperatively. RESULTS: Fenoldopam (0.1 microg kg(-1)min(-1)) administration was not associated with haemodynamic instability. On application of the aortic cross-clamp creatinine clearance decreased significantly in the placebo (83 +/- 20 to 42 +/- 29 mL min(-1) (mean +/- SD)) (P < 0.01) but not in the fenoldopam group, and this decrease persisted for at least 8 h after release of the cross-clamp (83 +/- 20 to 54 +/- 33 mL min(-1) (mean +/- SD)) (P < 0.05). Plasma creatinine concentration increased significantly from baseline on the first postoperative day in the placebo group (87 +/- 12 to 103 +/- 28 micromolL(-1) (mean +/- SD)) (P < 0.01) but not in the fenoldopam group. CONCLUSIONS: These findings are consistent with the hypothesis that fenoldopam possesses a renoprotective effect during and after infrarenal aortic cross-clamping.

Aged↗
PubMed1999

Intact proprioception and control of labour pain during epidural analgesia.

BACKGROUND: Accurate proprioception is critical while walking, yet an ambulatory epidural regimen that provides adequate analgesia for labour while simultaneously preserving proprioceptive input has not been described. METHODS: Sixty primigravidae in established labour received bupivacaine 15 mg (15 ml of 0.1% w/v) and fentanyl 100 micrograms through a lumbar epidural catheter. Clinical assessment of dorsal column sensory function included: vibration sense, distal proprioception and the Romberg test, and were all performed before catheter insertion and 30 min after the study bolus. Sensory modalities were also tested compared to an unblocked dermatome. Pain was scored on a 0-10 cm visual analogue scale (VAS) before and 30 min after induction. Intensity of the motor block was tested using a modified Bromage score (grade 1-6). RESULTS: The study bolus provided reliable analgesia with 43 parturients attaining a VAS pain score of zero. Mean duration of analgesia was 67.5 min (SD 22.85). All parturients retained the ability to perform a partial knee bend while standing (grade 6). No mothers exhibited impaired distal proprioception, altered vibration sense or a positive Romberg sign. CONCLUSION: This study confirms that the addition of lumbar epidural fentanyl 100 micrograms to 15 mg of epidural bupivacaine provides good control of labour pain with no motor block and establishes that this combination preserves dorsal column sensory function.

Adult↗
PubMed1998

Pharmacokinetics of (R,S)-Albuterol after aerosol inhalation in healthy adult volunteers.

The pharmacokinetics of inhaled (R,S)-albuterol following pulmonary absorption were studied in healthy human subjects. Ten subjects (5 females and 5 males) inhaled two puffs (180 microg) of albuterol via a metered-dose inhaler and spacer device. All subjects were nonsmoking and had normal pulmonary function. Charcoal slurries were ingested to block gastrointestinal absorption of drug. Venous samples were obtained from each subject at thirteen time points from 0 through 12 h post dose. (R,S)-Albuterol concentration in plasma was measured using a gas chromatography-mass spectrometry (GC-MS) assay. The plasma concentration-time profiles conformed to a two-compartment extravascular model with first-order absorption kinetics. The drug levels reached maximum in 12.6 +/- 2.2 (SD) minutes, which is in contrast with previous reports that maximum plasma concentrations occur within 2 to 4 h. The mean peak plasma level was 1469 +/- 410 pg/mL. The mean half-life of distribution was 17.9 +/- 8.2 min. The mean half-life of elimination was 4.4 +/- 1.5 h. Female subjects achieved peak concentration more rapidly than male subjects (10.4 vs 14.8 min, p = 0.01) and had a higher mean peak concentration (1778 vs 1159 pg/mL, p = 0.04).

Absorption↗
PubMed1998

Radiotherapy for nonfunctional pituitary adenoma: analysis of long-term tumor control.

OBJECT: The authors studied outcomes in patients who had undergone radiotherapy for nonfunctional pituitary adenoma to assess long-term tumor control and to identify factors affecting tumor control such as higher radiation doses, improved imaging, and histological characteristics of the tumor. METHODS: In this retrospective study, the authors evaluated 120 patients who received radiotherapy for nonfunctional pituitary adenomas between 1960 and 1991. The median follow-up period was 9 years (range 1 month-32 years). Radiation doses varied between 37.6 and 65.6 Gy (median 46.7 Gy). Tumors progressed in 15 of the 120 patients by 1 to 25 years after radiotherapy. Actuarial tumor control rates at 10, 20, and 30 years were 87.5+/-3.6%, 77.6+/-6.3%, and 64.7+/-12.9%, respectively. Tumor progression after radiotherapy occurred significantly more often (p=0.0397) in patients with oncocytoma than in patients with nononcocytic null cell adenoma. No other factors correlated significantly with tumor control. One case of optic and oculomotor neuropathy developed 4.5 years after a maximum dose of 50 Gy in 25 fractions. Radiation-induced neoplasms (meningioma and glioblastoma multiforme) developed at a rate of 2.7% at 10 and 30 years. CONCLUSIONS: The oncocytic variant of null cell pituitary adenoma appears less sensitive to control by radiotherapy than nononcocytic undifferentiated cell adenoma. A follow-up period extending beyond 20 years is needed adequately to assess the efficacy of radiotherapy for tumor control. Doses of 40 or 45 Gy in 20 or 25 fractions, respectively, appear optimal.

Actuarial Analysis↗
PubMed1997

Determination of albuterol in plasma after aerosol inhalation by gas chromatography-mass spectrometry with selected-ion monitoring.

Albuterol is a beta2-adrenergic agonist commonly used as a bronchodilator for the treatment of patients with asthma. We have developed an assay to determine plasma levels as low as 50 pg/ml of albuterol by gas chromatography-mass spectrometry (GC-MS). This assay utilizes isotopically labeled albuterol ([13C]albuterol) as an internal standard. In this assay albuterol and the internal standard are recovered from 1 ml of plasma using solid-phase extraction. The samples are then derivatized to trimethylsilyl ethers using N,O-bis(trimethylsilyl)trifluoro-acetamide with 1% trimethylchlorosilane. The samples are then analyzed by GC-MS with selected-ion monitoring (SIM) for the ions m/z 369.15 and 370.15. The method has been validated for a concentration range of 50-10000 pg/ml in plasma.

Administration, Inhalation↗
PubMed1988

The pulmonary vascular effects of dopamine, dobutamine, and isoproterenol in unilobar pulmonary edema in dogs.

Although catecholamine inotropic drugs are often used to support the circulation of critically ill patients with hypoxemic respiratory failure, their effect on the pulmonary circulation and on gas exchange is incompletely understood. In order to improve our understanding of the effects of these drugs on the pulmonary circulation, we made measurements of total and regional intrapulmonary shunt (Qs/Qt), distribution of pulmonary blood flow, and pulmonary hemodynamics before and after infusions of dopamine (n = 6, 5 micrograms/kg/min), dobutamine (n = 6, 10 micrograms/kg/min), isoproterenol (n = 6, 0.1 micrograms/kg/min), or saline in dogs with unilobar oleic acid-induced pulmonary edema. In addition to permitting determination of the overall hemodynamic and gas exchange effects of these drugs, this preparation allowed measurement of changes in distribution of pulmonary blood flow between normal and edematous lung. In 6 dogs given dobutamine, mean cardiac output (CO) increased by 1 liter/min, while pulmonary arterial pressure (PPA) increased by 2 mm Hg with no change in pulmonary vascular resistance (PVR) or distribution of pulmonary blood flow. There was a 5% increase in mean Qs/Qt which, because of the lack of evidence of pulmonary vasoactivity, was attributed to time or to increased CO. Isoproterenol produced a similar increase in CO, but reduced PPA and PVR indicating pulmonary vasodilator activity. Pulmonary vasodilation was most prominent in edematous lung, resulting in an increase in relative blood flow to the edema lung lobe and a substantial increase in Qs/Qt, exceeding the increase in all other groups. Dopamine, similarly increasing CO, did not change overall PVR but reduced fractional blood flow to the edema lobe by 3.4% of CO. Neither Qs/Qt nor PaO2 changed significantly in this group. The differing effects of these agents on pulmonary hemodynamics, intrapulmonary blood flow distribution, and gas exchange have potentially significant implications affecting the choice of drug used for circulatory support in hypoxemic respiratory failure.

Animals↗