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Biomedical subjects

P Kerr

Publications and source records attributed to P Kerr.

At least 37 records · Page 2Linked to original sources
PubMed1995

Risk factors for recurrent emergency department visits for asthma.

BACKGROUND: Patients presenting with asthma to emergency departments have lost control of their disease, have significant airways obstruction, and frequently require admission to hospital. Although even one visit is not desirable, there is a more disturbing subgroup who repeatedly visit the emergency department. METHODS: To investigate the reasons for multiple emergency visits, a questionnaire was given to 448 consecutive patients presenting to the two largest adult emergency departments in Ottawa, Canada between November 1989 and April 1991. Within this cohort, those who had made at least three visits in the past year were compared with controls (only one visit in the past year). RESULTS: Although inhaled corticosteroid use increased with multiple visits (indicating increased asthma severity), only 60% of those visiting at least three times in the past year were taking inhaled corticosteroids. Chronic undermedication relative to disease severity was apparent among the cases. The number of visits was associated with nocturnal asthma on a regular basis, work and school absenteeism, frequent visits to their regular physician, and frequent admissions to hospital. Visits were not related to psychological health, environmental allergens/irritants, or lack of perceived asthma severity. CONCLUSIONS: The recommendations of current asthma guidelines are not reaching these patients. The issue of translating guidelines from paper to practice must be addressed before highly effective medications can have an important impact on the frequency of emergency department visits.

Adrenal Cortex Hormones↗
PubMed1994

The effect of nasal CPAP on nocturnal reflux in patients with aperistaltic esophagus.

It has been shown that nasal continuous positive airway pressure (nasal CPAP) significantly reduces nocturnal reflux both in patients with sleep apnea and in patients without sleep apnea but consistent abnormal nocturnal reflux. The mechanism by which CPAP is thought to reduce reflux includes the elevation of the resting lower esophageal sphincter (LES) pressure. In this study, we tested the effect of nasal CPAP in two groups of patients with aperistaltic esophagus but with different resting LES pressure. Seven patients with scleroderma esophagus and six patients treated for achalasia were tested over a 48-h period. On the first night, the patients were untreated; on the second night, both groups received applied nasal CPAP at 8 cm H2O pressure. The percentage of time the pH < 4.0, the number of reflux events > 5 min, and the length of the longest reflux event were all significantly reduced in the patients with achalasia (p < 0.03), but not in the scleroderma group (p > 0.20). These results suggest that a residual resting LES pressure greater than that demonstrated by patients with scleroderma (> 10 mm Hg) may be necessary for nasal CPAP to affect nocturnal reflux.

Adult↗
PubMed1993

Nocturnal cluster headache associated with sleep apnea. A case report.

We describe a 49-year-old man with chronic cluster headache unresponsive to all medications. Following investigation in the sleep lab he was found to have obstructive sleep apnea (OSA) with associated oxygen desaturations during rapid eye movement (REM) sleep. He awakened during one of these episodes with a typical headache. Treatment with nasal CPAP abolished his OSA and desaturations, and largely abolished his headaches. He then developed central apneas during REM sleep. Further treatment with BiPAP, with a set backup rate, abolished both the apneas and the headaches. We conclude that there may be a link between nocturnal cluster headaches and sleep apnea.

Annexin A2↗
PubMed1993

Nasal continuous positive airway pressure. A new treatment for nocturnal gastroesophageal reflux?

Nasal continuous positive airway pressure (CPAP) reduces nocturnal gastroesophageal reflux (GER) in obstructive sleep apnea syndrome (OSAS) patients. The primary objectives of our investigation were to determine if CPAP could reduce reflux in non-OSAS patients and, if so, by what mechanism. Esophageal pH was monitored for 48 h in six nocturnal reflux patients. During the first 24 h, basal reflux data were collected; the second night, nasal CPAP was administered (pressure = 8 cm H2O). Esophageal manometry was obtained in six healthy adult volunteers both on and off nasal CPAP (pressure = 8 cm H2O) to ascertain CPAP's effects on esophageal pressure and peristalsis. The six reflux patients experienced less nocturnal GER while on CPAP. The mean percent time esophageal pH < 4 was reduced from 27.7 +/- 10.0 to 5.8 +/- 2.6 (p < 0.004); the mean reflux duration dropped from 2.1 +/- 0.6 to 0.9 +/- 0.5 min (p < 0.03); and the mean duration of longest reflux improved from 84.3 +/- 32.6 to 13.8 +/- 6.9 min (p < 0.01). The CPAP raised the mean resting midesophageal pressure by 4.4 cm H2O (p < 0.01) and the mean resting lower esophageal pressure (LES) by 13.2 cm H2O (p < 0.02) in the healthy volunteers. Nasal CPAP effectively reduced nocturnal GER in six patients with nocturnal reflux. The antireflux activity of CPAP is likely due to passive elevation of intraesophageal pressure and possibly to reflex LES constriction.

Administration, Intranasal↗
PubMed1992

Failure of a daily haemofiltration programme using a highly permeable membrane to return beta 2-microglobulin concentrations to normal in haemodialysis patients.

In an attempt to return to normal serum beta 2-microglobulin levels in a group of seven ESRD patients, a programme of daily HF with highly permeable AN69 membranes was undertaken. Pre-HF beta 2-M serum levels stabilized after 4 days at 20 mg/l, only 40% lower than the initial concentration. A total of 985 +/- 20 mg beta 2-M was removed over the week. The beta 2-M release rate averaged 97 micrograms/min with a broad range of values (63-128 micrograms/min). beta 2-M release peaked at 602 micrograms/min 1 h after the end of the HF session before returning to baseline by 12 h post-HF. We conclude that a return to normal blood beta 2-M concentrations in ESRD patients seems quite unrealistic despite a highly intensive extracorporeal therapy. Therefore other therapeutic alternatives have to be designed to prevent or cure beta 2-M amyloidosis.

Adsorption↗
PubMed1992

Oxidative modification of low-density lipoproteins and the inhibition of relaxations mediated by endothelium-derived nitric oxide in rabbit aorta.

1. The mechanism by which Cu(2+)-oxidized low-density lipoproteins (oxLDL) inhibit acetylcholine (ACh)-evoked relaxations mediated by endothelium-derived nitric oxide (EDRF) in rabbit aortic rings was investigated. The proposed role of lysophosphatidylcholine (LPC) in the inhibition was also studied. 2. The kinetics of lipid peroxidation of native low-density lipoproteins (LDL) from individual donors, as measured by changes in conjugated diene concentration, were related to the inhibitory effects of the resultant oxLDL. It was found that the more susceptible LDL was to oxidation, the greater the inhibition. 3. No correlation was found between the inhibitory effects of oxLDL and LPC content. 4. Synthetic 1-palmitoyl LPC produced an inhibition of ACh-induced relaxations and when added to precontracted rings evoked nitric oxide-mediated endothelium-dependent relaxation. This latter effect was not elicited by oxLDL. 5. Synthetic 1-palmitoyl (10 microM) had no effect on relaxations evoked by glyceryl trinitrate in endothelium-denuded aortic rings in contrast to the inhibition found previously for oxLDL. 6. Concentrations of oxLDL and phospholipase A2-treated LDL which inhibited relaxation contained very different LPC concentrations. Unlike oxLDL, the inhibitory effects of phospholipase A2-treated LDL preparations were independent of the donors and showed no lag period. 7. We suggest that there are differences in the mechanisms by which oxLDL and 1-palmitoyl LPC exert their inhibitory effects on relaxation. 8. The inhibition of relaxation by oxLDL (1-2 mg protein ml-1) was prevented by the presence of high-density lipoproteins (HDL; 1-2 mg protein ml-1).9. It is proposed that prevention of the inhibition of relaxation by HDL is consistent with the inhibitory factor(s) being lipophilic constituents of oxLDL. However, variations in the inhibitory effects of oxLDL preparations are not due to differences in their LPC content and factors other than LPC must contribute to the inhibition.

Animals↗
PubMed1992

Nasal CPAP reduces gastroesophageal reflux in obstructive sleep apnea syndrome.

Anecdotal reports suggest that obstructive sleep apnea syndrome (OSAS) patients may suffer from frequent nocturnal gastroesophageal reflux (GER) and that nasal continuous positive airway pressure may be an effective form of antireflux therapy in this population. To confirm these clinical impressions, we performed two consecutive days of 24-h esophageal pH monitoring, nocturnal esophageal pressure recording, and polysomnography on six OSAS patients complaining of regular nocturnal GER. On night one, the patients were untreated. Five of six subjects had abnormal amounts of nocturnal GER. Arousal, movement and swallowing were more frequent (p less than 0.043) and nadir intrathoracic pressure lower (p less than 0.005) in the 30 s prior to precipitous drops in esophageal pH (greater than or equal to 2 pH units) than during random control periods. A direct association between obstructive apneas and GER was not identified. On night two, nasal CPAP was administered and successfully treated apnea in five of six subjects. In these patients, there was also dramatic reduction in GER frequency and duration on CPAP. The mean percentage of time pH less than 4 dropped from 6.3 +/- 2.1 to 0.1 +/- 0.1 percent (p less than 0.025). We believe that OSAS may predispose to nocturnal GER by lowering intrathoracic pressure and increasing arousal and movement frequency. Nasal CPAP can correct these predisposing factors and reduce GER.

Adult↗
PubMed1992

The importance of nasal resistance in obstructive sleep apnea syndrome.

The importance of nasal airflow resistance in the pathogenesis of obstructive sleep apnea syndrome (OSAS) remains contentious. We performed formal nocturnal polysomnography (PSG) on OSAS patients under conditions of baseline and reduced nasal resistance to answer two main questions. First, to what degree does baseline nasal airflow resistance influence upper airway collapse in OSAS patients? Second, in what proportion of the OSAS population is baseline nasal resistance contributing to the pathogenesis of upper airway collapse? Our study group consisted of 10 patients with a wide range of OSAS severity. Six of these patients had symptoms and clinical evidence of chronic nasal obstruction which, in some, was associated with markedly elevated nasal resistance. A placebo (normal saline) was instilled in the nose of each patient on the night of baseline data collection. On the treatment night of the study, nasal resistance was reduced by application of topical vasoconstrictor and insertion of vestibular stents designed to dilate the area of the nasal valve. Posterior rhinomanometry was used to measure resistance to nasal airflow immediately before and after each PSG study. Although treatment was associated with a subjective improvement in sleep quality and mean drop in nasal resistance of 73% (P less than 0.001), there was no significant improvement in sleep architecture, nocturnal oxygenation, or the amount of apnea experienced by patients. The most significant improvement was a reduced number of arousals/hour from 52.4 +/- 12.4 on placebo to 43.7 +/- 10.2 on treatment (P less than 0.04).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Intraperitoneal (IP) vancomycin therapy for CAPD peritonitis--a prospective, randomized comparison of intermittent v continuous therapy.

The use of intraperitoneal (IP) vancomycin as initial, single agent therapy for gram positive and "no organism" continuous ambulatory peritoneal dialysis (CAPD) peritonitis is described, comparing continuous and intermittent administration schedules. "Continuous" therapy consisted of an IP 1-g loading dose of vancomycin followed by 30 mg/L dialysate effluent. "Intermittent" therapy consisted of 2 IP doses of 30 mg vancomycin/kg body weight--the initial dose delivered at diagnosis and the second dose 1 week later. All patients presenting with peritonitis (n = 90) were randomized to receive either continuous or intermittent vancomycin therapy. Patients in whom gram negative organisms and fungi were identified by microscopy and culture were transferred to therapy with a more appropriate antibiotic (n = 39). In the remainder (n = 51), CAPD peritonitis was treated solely with vancomycin (continuous, n = 21; intermittent, n = 30). Clinical resolution was seen in all patients, requiring a mean of 3.2 days for macroscopic clearing of dialysate effluent. Recurrence of peritonitis within 1 month of cessation of therapy was unusual and did not vary between treatment protocols (4/21 v 3/30; P = NS). There were no differences in observed side effects. Thus, IP vancomycin proved to be a useful single agent therapy for gram positive and no organism CAPD peritonitis. Therapy with two IP doses was effective and as safe as continuous IP vancomycin therapy, and therefore should replace other vancomycin administration schedules in the treatment of CAPD peritonitis.

Drug Administration Schedule↗