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Biomedical subjects

M N Gomez

Publications and source records attributed to M N Gomez.

9 recordsLinked to original sources
PubMed2000

Release of angiotensin-(1-7) from the rat hindlimb: influence of angiotensin-converting enzyme inhibition.

The results of recent studies have demonstrated that angiotensin (Ang)-(1-7) contributes to the antihypertensive actions of either combined ACE/Ang II type 1 receptor blockade or ACE inhibition alone. The vasculature is a key site of action for either drug regimen, and evidence favors a local Ang system within these tissues. Because ACE may degrade Ang-(1-7), we determined whether ACE inhibition alters Ang-(1-7) release from the rat hindlimb perfused with Krebs-Ringer buffer containing Ficoll. Ang-(1-7) release averaged 36+/-13 fmol (period 1, 15-minute collection) and 44+/-11 fmol (period 2) in the control buffer. The addition of the ACE inhibitor lisinopril to the perfusion buffer augmented levels of Ang-(1-7) in periods 3 (144+/-39 fmol) and 4 (163+/-35 fmol; P<0.05 versus 1 or 2, n=8). HPLC and radioimmunoassay of effluent from control or lisinopril treatment demonstrated a single immunoreactive peak with a retention time identical to that of Ang-(1-7). The addition of the neprilysin inhibitor SCH 39370 reduced Ang-(1-7) release in the lisinopril buffer from 177+/-32 (period 1) and 173+/-39 (period 2) fmol to 112+/-24 (period 3) and 87+/-23 fmol (period 4; P<0.05 versus 1 or 2, n=6). Ang I metabolism in the collected perfusate revealed the formation of Ang-(1-7) that was sensitive only to thimet oligopeptidase inhibition; Ang II generation was not detected. The present study demonstrates the recovery of endogenous Ang-(1-7) from the perfused hindlimb. The release of Ang-(1-7) is significantly influenced by inhibition of ACE, which may reflect both increased substrate (Ang I) levels and reduced metabolism of the peptide. Neprilysin inhibition reduced but did not abolish Ang-(1-7) release, which suggests that other endopeptidases may contribute to the release of the peptide.

Angiotensin I↗
PubMed1992

Dose-response relationship of isoflurane and halothane versus coronary perfusion pressures. Effects on flow redistribution in a collateralized chronic swine model.

The authors studied the redistribution of myocardial blood flow in a collateral-dependent (CD) zone as a function of coronary perfusion pressure (CPP) during isoflurane and halothane anesthesia. A swine model with CD myocardium distal to a chronically occluded left anterior descending coronary artery was developed and studied. Sixteen piglets were allowed to grow for 8-10 weeks after banding of the left anterior descending coronary artery. They were randomly anesthetized with either isoflurane (n = 8) or halothane (n = 8) as the sole anesthetic, which was used to regulate specific CPP. The resultant regional myocardial blood flows were measured using radiolabeled microspheres. Four randomly allocated CPPs, of 30, 40, 45, and 55 mmHg, were studied in each animal. Four additional collateralized animals were anesthetized with alpha-chloralose, and the same CPPs were obtained using an intravenous adenosine infusion (1-5 microM kg-1) to validate this model. There was a proportional decrease in heart rate and blood pressure in both the isoflurane and and the halothane group with CPP. Cardiac output was significantly decreased in the halothane group at 30 mmHg when compared to 55-mmHg CPP, but it was maintained in the isoflurane group. Systemic vascular resistance was significantly lower in the isoflurane group at 30 and 40 mmHg when compared to 55-mmHg CPP. Both the isoflurane and the halothane group showed a proportional and significant decrease in endo-, mid-, and epicardial blood flows at 30-mmHg CPP when compared to baseline. In both CD and normal perfusion zones, isoflurane consistently sustained a higher endocardial blood flow than halothane (5.7-41.1%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Limited lateral thoracotomy. Improved postoperative pulmonary function.

A prospective randomized controlled study was designed to determine differences in early postoperative pulmonary function, pain, and complications between patients undergoing limited lateral muscle-sparing thoracotomy. Fifteen patients underwent standard thoracotomy and 13 underwent limited incision with the same anesthetic technique. During the first 24 hours after operation, there were large decreases in the results of spirometric tests of pulmonary reserve (forced expiratory volume in 1 second and forced vital capacity), but these decrements were consistently significantly smaller in the limited-incision group. Other tests of pulmonary function (mid-expiratory phase forced expiratory flow, alveolar-arterial oxygen gradient, and PaCO2), however, demonstrated similar postoperative changes in both groups. Similarly, there were no differences in pain scores, postoperative morphine requirements, complications, or length of hospital stay. Use of the limited muscle-sparing incision resulted in improved postoperative pulmonary reserve, but this did not translate into differences in other measures of postoperative convalescence.

Female↗
PubMed1989

Intrapleural bupivacaine--technical considerations and intraoperative use.

The authors evaluated the incidence and type of technical problems associated with blind insertion of intrapleural catheters placed in 21 anesthetized patients and then injected in a double-blind fashion with 0.5% bupivacaine (1.5 mg/kg) or isotonic saline. The patients' chests were then opened, catheter positions located, and the lungs inspected. Eleven of the catheters were located with the tips intrapleurally, three extrapleurally, and seven actually in lung tissue. Eight patients had holes in the lung surface. Three patients had a pneumothorax, two of which were under tension. Plasma bupivacaine levels reached maximal concentrations at about 20 minutes in those with intrapleurally placed catheters, but not until 60 minutes when the catheter had actually penetrated the lung. Significant variations in plasma bupivacaine levels were achieved when the catheter entered lung tissue, with potentially toxic levels in one patient. To evaluate intraoperative analgesic effects, all patients were given a standard anesthetic with isoflurane, oxygen, and a muscle relaxant. There was no significant difference in isoflurane requirement between the groups who had bupivacaine v saline injected into their intrapleural catheters before surgery. It is concluded that blind insertion of intrapleural catheters can be hazardous, especially if followed by positive-pressure ventilation. In addition, catheter placement in lung tissue, which was not uncommon, delays the time for peak plasma concentrations and may increase risk of toxicity. Intrapleural bupivacaine was not found to be a useful adjunct to general anesthesia during thoracotomies.

Adult↗
PubMed1989

Intrapleural bupivacaine v saline after thoracotomy--effects on pain and lung function--a double-blind study.

The effects of intrapleural (IP) bupivacaine on pain, morphine requirement, and pulmonary function were evaluated in 15 patients for 24 hours after thoracotomy. An IP catheter was placed during surgery. Patients were randomized in a double-blind fashion to receive 1.5 mg/kg of 0.5% bupivacaine IP or saline on two occasions, eight hours apart. A standard anesthetic with thiopental, oxygen, isoflurane, and nondepolarizing muscle relaxant was given. Pain was evaluated with a visual analog pain score every hour, and forced vital capacity (FVC), forced expiratory volume one second (FEV1), peak expiratory flow (PF), and forced expiratory flow 25% to 75% (FEF) were measured 1, 2, 4, 8, and 24 hours postoperatively as well as before and 30 minutes after each IP injection. Arterial blood gases were sampled 1, 2, 8, and 24 hours postoperatively. Plasma bupivacaine concentrations were measured in 10 patients 5, 10, 20, 30, 60, 120, and 180 minutes after IP injection. With each IP bupivacaine injection, the pain score and morphine requirement decreased. There was a significant improvement in all pulmonary function tests in the patients receiving bupivacaine, but no change in the saline controls. The analgesic effect was shortlived (two to five hours), possibly because of loss of bupivacaine in the chest drains. No differences were seen between the two groups after the effect of IP bupivacaine had worn off. Plasma bupivacaine levels had a Cmax of 0.44 to 1.50 micrograms/mL, with a Tmax at 5 to 30 minutes with levels well below 2 to 4 micrograms/mL where increasing toxicity is seen.

Aged↗
PubMed1989

A cost/benefit analysis of randomized invasive monitoring for patients undergoing cardiac surgery.

The aim of this study was to determine the effect of choice of invasive monitoring on cost, morbidity, and mortality in cardiac surgery. Two hundred and twenty-six adults undergoing elective cardiac surgery were initially assigned at random to receive either a central venous pressure monitoring catheter (group I), a conventional pulmonary artery (PA) catheter (group II), or a mixed venous oxygen saturation (SvO2) measuring PA catheter (group III). If the attending anesthesiologist believed that the patient initially randomized to group I should have a PA catheter, that patient was then reassigned to receive either a conventional PA catheter (group IV) or SvO2 measuring PA catheter (group V). The total costs were defined as the total amount billed to the patient for the catheter used; the professional cost of its insertion; and the determinations of cardiac output, arterial blood gas tensions, hemoglobin level, and hematocrit. Mean total monitoring and laboratory costs in Group I ($591 +/- 67) were statistically significantly (P less than 0.05) less than costs in Group II ($856 +/- 231). Further, mean monitoring and laboratory costs in Group II were statistically significantly (P less than 0.05) less than those in Group III ($1128 +/- 759). Patients in group IV incurred mean total costs of $986 +/- 578, while those in group V had mean total costs of $1126 +/- 382 (NS). There were no significant differences between any of the groups with respect to length of stay in the intensive care unit, morbidity, or mortality.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Gas Analysis↗