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M Echevarría

Publications and source records attributed to M Echevarría.

34 records · Page 2Linked to original sources
PubMed1996

[Effect of the local anesthetic on visceral pain in cesarean sections done under intradural anesthesia].

OBJECTIVES: To evaluate the influence of local anesthetic on the incidence and severity of visceral pain during cesarean section performed under subarachnoid anesthesia. PATIENTS AND METHOD: This was a randomized double blind study of 90 parturients undergoing scheduled or emergency cesareans. The women were distributed among three groups according to local anesthetic used: 2% isobaric mepivacaine in group 1, 0.5% hyperbaric bupivacaine in group 2, and 0.5% isobaric bupivacaine with adrenalin in group 3. The total anesthetic dose was selected based on height, and pain was defined as silent and dull, or a sensation of pressure that was poorly defined, diffuse or referred to another area and accompanied or not by nausea and/or vomiting. Pain was assessed on a visual analog scale at various moments during surgery. Other variables recorded were metameric level of blockade, hemodynamic function and presence of nausea and/or vomiting. RESULTS: One patient in each group was excluded. The incidences of visceral pain and 95% confidence intervals were as follows: 38% (23-56%) in group 1 and 10% (3.5-25%) in groups 2 and 3 (p = 0.002). The metameric level of blockade differed significantly among the groups. The highest level (T1-5) was reached in group 1 but level was the most consistent (T3-5) in group 2. Systolic arterial pressures in all groups were significantly lower than baseline levels 5 min after puncture and the decrease was greatest in group 3. The highest incidence (p = 0.01) of nausea and/or vomiting occurred in the isobaric bupivacaine group. CONCLUSION: Use of hyperbaric bupivacaine offers advantages over the other techniques, as it assures more consistent attainment of metameric level, an incidence of visceral pain that is lower than that of isobaric mepivacaine, and fewer hemodynamic repercussions than isobaric bupivacaine with vasoconstrictor.

Adult↗
PubMed1995

The proximal straight tubule (PST) basolateral cell membrane water channel: selectivity characteristics.

Proximal straight tubules (PST) were dissected from rabbit kidneys, held by crimping pipettes in a chamber and bathed in a buffered isosmotic (295 mOsm/kg) solution containing 200 mM mannitol (MBS). Changes in tubule diameter were monitored on line with an inverted microscope, TV camera and image processor. The PST were then challenged for 20 sec with MBS made 35 mOsm/kg hyperosmotic by addition of either NaCl, KCl, mannitol (M), glycerol (G), ethylene glycol (E), glycine (g), urea (U), acetamide (A) or formamide (F). With NaCl, KCl, M, G, E, g, U, and A, tubules shrunk osmometrically within 0.5 sec and remained shrunk for as long as 20 sec without recovering their original volume (sometimes A showed some recovery). PST barely shrunk with F and quickly recovered their original volume. The permeability coefficients were 0 microns/sec (NaCl, M, g, E and U), 1 micron/sec (A), 84 microns/sec (F) and 0.02 micron/sec (G). The reflection coefficients sigma = 1.0 (NaCl, KCl, M, G, E, g and U), 0.95 (A) and 0.62 (F). Similar sigma values were obtained by substituting 200 mOsm/kg M in MBS by either NaCl, KCl, G, E, g, U, a or F. The olive oil/water partition coefficients are 5 (M), 15 (U), 85 (A) and 75 (F) (all x 10(-5)). Thus, part of F permeates the cell membrane through the lipid bilayer. The probing molecules van der Waals diameters are 7.4 x 8.2 x 12.0 (M), 3.6 x 5.2 x 5.4 (U), 3.8 x 5.2 x 5.4 (A) and (3.4 x 4.5 x 5.4 (F) A.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1995

[Comparative study of single-dose intradural anesthesia and continuous intradural anesthesia with or without fentanyl].

OBJECTIVE: To compare the hemodynamic effects, level of anesthetic blockade and advantages of single-dose versus continuous intrathecal anesthesia with hyperbaric bupivacaine with and without fentanyl. PATIENTS AND METHOD: Prospective study in 45 patients under 65 who were scheduled for elective surgery of the lower abdomen, randomly divided into 3 groups. Group 1 and 2 received continuous intrathecal anesthesia with 10 mg hyperbaric bupivacaine; group 2 also received 25 mcg fentanyl. Patients in group 3 were given a single intrathecal dose of 15 mg hyperbaric bupivacaine. Mean arterial pressure and heart rate were recorded at baseline and 10, 20 and 30 minutes after the start of anesthesia. The level of block achieved was recorded after 10, 30 and 60 minutes. Hemodynamic changes, differences in blockade and side effects were analyzed. RESULTS: Hemodynamic changes were greater in group 2 (fentanyl) than in groups 1 and 3 (p < 0.05), with group 3 showing the greatest degree of hemodynamic stability. Level of blockade was always higher in group 2, with significant differences at 30 min (p < 0.05). Seven and 5 reinjections by catheter were necessary in groups 1 and 2, respectively. Two patients in group 3 required general anesthesia when blockade was inadequate. Apart from pruritus in group 2 (40%), no side effects due to anesthesia were observed. CONCLUSIONS: A single dose intrathecal anesthesia, produces less hemodynamic changes than a continuous intrathecal block. Nevertheless, continuous intrathecal block, allows the maintenance of the block as long as required. The association of fentanyl enhances the hemodynamic changes with no other beneficial effects.

Adult↗
PubMed1995

[Comparison of changes in plasma concentrations of ACTH and beta-endorphin in cholecystectomy under general anesthesia and general plus epidural anesthesia].

OBJECTIVE: To study neuroendocrine response during cholecystectomy under general anesthesia with fentanyl and under general anesthesia with nitrous oxide plus thoracic epidural block, by determining plasma levels of ACTH and beta-endorphin. PATIENTS AND METHODS: This was a prospective study of 2 randomly chosen groups of 7 patients each who were undergoing cholecystectomy. One group received general anesthesia with fentanyl at initial doses of 10 micrograms/kg-1 followed by perfusion of 5 micrograms.kg-1.h-1. The other group received general anesthesia with 60% nitrous oxide in oxygen combined with bupivacaine 0.5% for thoracic epidural blockade. Plasma levels of ACTH and beta-endorphin were determined at the following moments: A, upon arrival in the operating theater; B, after anesthetic induction and intubation; C, after incision; D, 30 minutes after start of surgery; E, after surgery but before extubation, and F, after arrival in the recovery room. Also recorded were mean arterial pressure and heart rate. RESULTS: In both groups we found significantly higher levels of beta-endorphin throughout surgery. The increase was greater, however, in the group receiving combined anesthesia at moments D (p = 0.008) and E (p = 0.008). ACTH levels rose significantly during surgery (p = 0.004) in the combined anesthesia group, whereas there was only a slight increase in the group receiving only general anesthesia (p = NS). beta-endorphin levels increased proportionally more than ACTH levels during combined anesthesia. Hemodynamic stability was acceptable in both groups. CONCLUSION: General anesthesia with fentanyl at the dose used in this study was more effective that combined anesthesia in mitigating the release of ACTH and beta-endorphin during cholecystectomy.

Adrenocorticotropic Hormone↗
PubMed1993

Cultured bovine corneal endothelial cells express CHIP28 water channels.

Cultured bovine corneal endothelial cells (CBCEC) transport fluid from the basal to the apical surface. In this study, we examined whether the plasma membranes of these cells have water channels. We cultured BCEC on glass plates and monitored the intensity of the light scattered (IS) by the cells. We determined the kinetic constant (k) of the change in IS on exposure to a 10% hypoosmotic challenge to calculate the osmotic permeability (Pf) of the plasma membrane. At 37 degrees C, we found values of k = 0.68 +/- 0.07 s-1 and Pf = 93.3 +/- 33 microns/S (n = 13). The sulfhydryl reagent p-chloromercuribenzenesulfonate (pCMBS; 1 mM) reduced Pf by 75%; 5 mM dithiothreitol reversed such inhibition. The activation energy (Ea) of Pf in the range 10-37 degrees C was 4.7 +/- 0.7 kcal/mol (n = 5). The high Pf, values, the inhibition by pCMBS, and the low Ea strongly suggest the presence of water channels. Therefore, we tested whether the injection of poly(A)+ RNA prepared from CBCEC into Xenopus laevis oocytes results in the expression of water channels. Four days after injection, we measured oocyte Pf values from the rate of volume increase on exposure to hypoosmotic medium. In control oocytes injected with 50 nl of water, Pf was 13.4 +/- 0.3 microns/S (n = 63). In oocytes injected with poly(A)+ RNA (50 ng/oocyte in 50 nl water), Pf was 40.9 +/- 1.6 microns/S (n = 72).(ABSTRACT TRUNCATED AT 250 WORDS)

4-Chloromercuribenzenesulfonate↗
PubMed1993

Determination of volume and water permeability of plated cells from measurements of light scattering.

Measurements of cell membrane water osmotic permeabilities can be inaccurate because of the technical difficulties inherent to cell volume measurements and because of the presence of an unstirred water layer in contact with the cells. We detail here a method we have developed to quantify transient changes in cell volumes from the intensity of light scattered by cells. For this, we theorize how an unstirred layer originates in a perfusing chamber, and we calculate values for both cell membrane water osmotic permeability and unstirred layer thickness from time transient changes in scattered light. We apply a computer algorithm that finds the best correspondence between experimental data and estimated values. This is done by solving a differential equation governing cell volume changes by numerical integration (Runge-Kutta) and iterating the procedure varying the test values of osmotic permeability and unstirred layer thickness until the best fit is achieved. We exemplify this procedure with experimental results obtained in adherent cultured cells.

Animals↗
PubMed1988

Histological and immunocytochemical study of the endocrine pancreas of the lizard Podarcis hispanica Steindachner, 1870 (Lacertidae).

The endocrine pancreas of the lizard Podarcis hispanica is described using light and electron microscopy. The endocrine pancreas of this reptile is located throughout the spleen side of the organ and consists of islet-like structures, small groups of two to five cells, and single scattered endocrine cells. The endocrine cells, including the islet-like structures, are not discrete units; on the contrary, they are intermingled with the endocrine component, both forming the glandular units. The endocrine islet-like structure shows a peculiar pseudoacinar pattern. The tridimensional reconstruction allows us to recognize the true structure of the glandular units. They are made up of two or three tubules closely arranged around a blood vessel, the endocrine component being disposed in the facing aspects of the tubules, around the vessel. Silver methods, Giemsa, and peroxidase-antiperoxidase techniques for light microscopy, immunogold, and routine methods for electron microscopy were used to demonstrate the regulatory peptide-producing cells present in the endocrine pancreas. Four major pancreatic endocrine cells, immunolocalized with the light and electron microscope, have been described: glucagon-containing cells (granules of 440 nm in diameter), insulin cells (400 nm), somatostatin cells (610 nm), and pancreatic polypeptide-containing cells (460 nm).

Animals↗
PubMedDate not supplied

[Headache following dural puncture in pregnant patients at term. Comparative study with non-obstetric patients].

OBJECTIVES: To compare the incidence of postdural puncture headache after subarachnoid anesthesia with a 24G Sprotte needle among full-term obstetric patients as compared to non-obstetric patients. PATIENTS AND METHODS: A total of 200 patients were studied prospectively, divided into 2 groups. Group 1 (n = 100) patients were delivered by cesarean section and group 2 (n = 100) patients underwent infraumbilical or traumatological surgery. All were ASA I-II and under 40 years of age. Hydration was accomplished with lactated Ringer's solution 400-1,000 ml before mid-line puncture. The anesthetic used in both groups was isobaric bupivacaine 0.5% with a vasoconstrictor. The incidence of arterial hypotension and accompanying symptoms was recorded; perioperative administration of vasoactive amines and anticholinergics and liquids administered was measured. Twenty-four to 48 hours later the patients were asked when they started walking and if postdural puncture headache was experienced. RESULTS: Group 1 received smaller doses of bupivacaine (p < 0.05) and the incidence of arterial hypotension was greater (p < 0.01) and required increased administration of amines (p < 0.01) and perioperative fluid therapy (p < 0.001). No difference was found between the two groups either for time of start of ambulation or for incidence of headache, which was 1% in both groups. CONCLUSIONS: The incidence of postdural puncture headache in obstetric patients is low and similar to that of non-obstetric patients when the 24G Sprotte needle is used.

Adolescent↗
PubMedDate not supplied

[Postoperative mental confusion in the elderly with hip fracture. Perioperative risk factors].

OBJECTIVE: To determine the incidence of postoperative mental confusion and perioperative risk factors in elderly patients with femoral neck fractures. PATIENTS AND METHODS: A prospective study of patients 65 years of age or older undergoing surgery for hip fracture with intradural anesthesia between March 1992 and August 1993. Although the total number of cases came to 162, only 50 patients were enrolled in the study: the rest were excluded mainly because of mental deficits presenting before surgery. Folstein's Mini-Mental State test was used to assess mental function. Risk factors analyzed were classified as preoperative, intraoperative (in the operating room and the recovery room) or postoperative (hospital ward). RESULTS: Eleven (22%) patients showed signs of postoperative mental confusion. Simple analysis revealed a correlation between mental confusion and ASA (p = 0.01), neuropsychiatric history (p = 0.03) and preoperative hemoglobulin, red blood cell and urea nitrogen levels (p = 0.02). Multifactorial discriminant analysis indicated that patients with low red cell counts before surgery, high urea nitrogen and neuropsychiatric histories were more predisposed (p = 0.004) to mental confusion. CONCLUSIONS: A high incidence of postoperative mental confusion is associated to pre-surgical factors. We therefore suggest that greater preventive and therapeutic efforts be directed preferably to preparation before surgery, especially in patients at high risk.

Aged↗
PubMedDate not supplied

[Synergism of midazolam and propofol in the induction of anesthesia].

INTRODUCTION: The purpose of this study was to determine the possible interaction of midazolam and propofol in the induction of anesthesia. METHODS: A double-blind study of 90 ASA I-II women undergoing elective general surgery and gynecology was performed. The patients were divided into three groups of 30 patients receiving midazolam, propofol and a combination of both as the anesthesia induction agent. As a test of anesthetic induction the response to the verbal order of opening their eyes was evaluated. The dose-response curves for each group were determined by a logistic regression procedure while isobolographic analysis compared the actions of both agents separately and together. RESULTS: The ED50 in the propofol group was 1.56 mg.kg-1 and that of the midazolam group was 0.24 mg.kg-1. In the midazolam-propofol group the ED50 of midazolam was reduced approximately a quarter (0.068 mg.kg-1) when associated to the half of the ED50 of propofol anteriorly obtained. Isobolographic analysis revealed that the conjunctive action of both drugs was synergic (p = 0.04). CONCLUSIONS: Propofol potentiates the action of midazolam in anesthetic induction. Although this synergism also reduces with the association of thiopental-midazolam, the mechanism of action is not demonstrated as the same. Thiopental increases the affinity of the benzodiazepines for the GABA complex receptors which has not been described for propofol.

Adult↗
PubMedDate not supplied

[Prophylaxis of intraoperative nausea and vomiting with sub-hypnotic dose of propofol during intradural anesthesia in cesarean section].

OBJECTIVES: To determine the preventive and therapeutic effect of 10 mg of propofol administered after delivery on the incidence of intraoperative nausea and vomiting (IONV) during intradural anesthesia for cesarean delivery. PATIENTS AND METHOD: Controlled, randomized double blind study of 60 women (ASA I-II) receiving intradural anesthesia for elective or deferred emergency cesarean delivery. The propofol group received 10 mg i.v. immediately after fetal extraction. The control group received an equal volume of Intralipid. The presence of IONV after administration of the prophylactic bolus was treated with a second bolus, and if nausea had not subsided completely after two minutes, treatment was topped up with dehydro-benzoperidol. RESULTS: The control group included 31 women and the propofol group 29, of whom 3 were excluded. Control variables were similar in the two groups. There were no significant differences in the incidence and severity of IONV between the two groups (22.5 versus 23%). The top-up antiemetic drug was used in the same number of patients in each group. CONCLUSIONS: Although 10 mg propofol has been described as an effective direct antiemetic, episodes of IONV were neither prevented nor reversed by its use during intradural anesthesia for cesarean delivery.

Adult↗
PubMedDate not supplied

[Explicit and implicit memory during inhalation and intravenous anesthesia].

OBJECTIVE: Patients rarely report memory or knowledge of surgery after general anesthesia. During apparently adequate surgical anesthesia, however, information processing of high level functions, such as language comprehension and learning, can continue unconsciously. Our objective is to assess whether different anesthetic techniques (two inhalational and two intravenous) guarantee the absence of both types of memory. PATIENTS AND METHOD: One hundred patients were randomly assigned to receive the following anesthetic procedures: desflurane/N2O (group 1), isoflurane/N2O (group 2), fentanyl/N2O (group 3) and total intravenous anesthesia (group 4). A cassette with the same music was played in all cases, and an order requiring a nonverbal response was given to 15 randomly chosen patients in each group. Response was evaluated at a visit 24 to 48 hours after surgery. Fifteen patients, therefore, constituted the study group for each anesthetic procedure, and 10 patients formed the control group. We assessed the presence of explicit memory in a structured interview, and implicit memory by way of the relation between the number of times the nonverbal order was obeyed and the time of the interview. RESULTS: Explicit memory was absent in all patients. The presence of implicit memory was confirmed, however, in the isoflurane (p = 0.02) group. Significant differences between the isoflurane group and both the desflurane and total intravenous anesthesia groups (p = 0.03) were found. CONCLUSION: Explicit memory was absent with all four anesthetic techniques used in our study. Implicit memory was more difficult to inhibit, however, with isoflurane/N2O.

Adolescent↗