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Biomedical subjects

G Lema

Publications and source records attributed to G Lema.

At least 19 recordsLinked to original sources
PubMed2001

[Treatment of advanced heart failure by heart transplantation].

BACKGROUND: Heart transplantation currently provides the most effective treatment for advanced heart failure. However, medical therapy for this condition has also improved, heart donors are scarce and the cost of the procedure is high. Therefore the indications and management of these patients need reevaluation. AIM: To analyze the results of 24 patients submitted to heart transplantation for end-stage heart failure needing repeated hospitalizations and i.v. inotropes for compensation. PATIENTS AND METHODS: The group was comprised by 21 men and 3 women with a mean age of 36.8 years, mean left ventricular ejection fraction 19 +/- 4.5%, mean systolic pulmonary artery pressure 48 +/- 13 mmHg (24-70) and mean pulmonary vascular resistance 2.6 Wood Units (1-5). Fourteen patients (58%) had a previous median sternotomy. Immunosuppression did not include induction therapy and steroids were discontinued early. RESULTS: Operative mortality was 4% at 30 days. Actuarial survival at one year was 90% and at 5 years 72%. Freedom from rejection at one year was 76% and at 5 years 50%. Freedom from infection was 70% at one year and 56.5% at five years. All patients with more than 3 months of follow-up were in functional class I. CONCLUSIONS: These results justify the proposed modifications for transplantation protocols.

Actuarial Analysis↗
PubMed2000

Surfactant function affected by airway inflammation and cooling: possible impact on exercise-induced asthma.

Pulmonary surfactant maintains patency of narrow conducting airways. An inflammation, with a leakage of plasma proteins into the airway lumen, causes surfactant to lose some of this ability. Will a lowering of temperature aggravate the deteriorating effect of an inflammation? Calf lung surfactant extract (CLSE) with proteins added was studied with a capillary surfactometer (CS) at temperatures of 25-42 degrees C. BALB/c mice were infected with respiratory syncytial virus (RSV). Six days later the lungs were lavaged and the surfactant in the lavage fluid was studied with the CS at temperatures of 25-42 degrees C. Lavage fluid from allergen challenged asthmatics was examined for its content of surfactant inhibitors at reduced temperatures. It was shown that CLSE with proteins gradually lost its ability to maintain patency as the temperature was lowered. Lavage fluid from the RSV infected mice showed a similar dysfunction at low temperatures. Lavage fluid from the airways of human asthmatics, when challenged with antigen but not with saline, contained agents inhibiting surface activity, particularly at reduced temperatures. Airway inflammation causes surfactant to lose its ability to maintain patency, particularly as the temperature is reduced. That might be a reason for the increased airway resistance observed in asthma patients hyperventilating in cold weather.

Albumins↗
PubMed2000

Comparison of two doses of aprotinin in patients receiving aspirin before coronary bypass surgery.

This study was designed to evaluate efficacy and tolerability of two different doses of aprotinin in patients receiving aspirin before undergoing coronary artery bypass grafting. Forty-two patients were randomized to receive either placebo (group I), or aprotinin in doses of 4,000,000 KIU (group II) or 6,000,000 KIU (group III). Drug efficacy was determined by measuring postoperative blood loss and transfusion of blood products. Both doses were effective in reducing blood loss and transfusion requirements. Blood loss through thoracotomy drainage was 450 +/- 224, 182 +/- 144, 142 +/- 98 ml, respectively, for control and treatment groups II and III (p = 0.0001). The numbers of patients with blood transfusions were seven (50%), two (17%) and two (17%) for group I and treatment groups II and III, respectively (p = 0.10). Tolerability was excellent and complications few and reversible. In conclusion, high and medium doses of aprotinin were well tolerated and reduced bleeding and transfusion requirements in patients submitted to coronary bypass surgery under the effects of aspirin.

Adult↗
PubMed2000

Pseudomonas aeruginosa from patients with cystic fibrosis affects function of pulmonary surfactant.

Patients with cystic fibrosis are severely affected by an infection with Pseudomonas aeruginosa, a microbe known to synthesize phospholipase C. This study was designed to determine whether that enzyme would affect the function of pulmonary surfactant phospholipids. Mucoid and nonmucoid strains of P. aeruginosa, freshly obtained from patients with cystic fibrosis, were cultured for 12 h on agar plates. The bacteria were suspended in saline solution and then pelleted by centrifugation. The supernatant was used to dilute the surfactant preparation, calf lung surfactant extract, from 35 to 2 mg/mL. Surfactant function, before and after incubation, was examined with a capillary surfactometer, an instrument specifically developed for an evaluation of the ability of surfactant to maintain patency of a narrow glass tube, simulating a terminal conducting airway. Phospholipid hydrolysis was also evaluated biochemically by determining the total content of phospholipids in surfactant before and after incubation. In five experiments, the lipids were separated with thin-layer chromatography, and the phosphorus content was determined in the diacylphosphatidylcholine band before and after incubation for 6, 24, and 48 h. Capillary openness and phospholipid concentration decreased as enzyme concentration and time of incubation increased (p<0.0001). Linear regression showed a significant correlation between time of capillary openness and phospholipid concentration (r = 0.957; p<0.0001). Calf lung surfactant extract hydrolysis was catalyzed by extracts of the bacteria, particularly the nonmucoid, analogous to the catalysis observed with phospholipase C. Surfactant hydrolysis catalyzed by enzymes from P. aeruginosa might severely affect surfactant function provided enzyme concentration is high and time of incubation is long.

Cystic Fibrosis↗
PubMed2000

[Carotid endarterectomy under regional anesthesia: initial experience].

BACKGROUND: Endarterectomy is the treatment of choice for internal carotid artery critical stenosis. Some authors have proposed that the use of regional anesthesia has advantages over general anesthesia. AIM: To report our initial experience with carotid endarterectomy under regional anesthesia. PATIENTS AND METHODS: Between 1998 and 1999, patients with critical carotid artery stenosis, asymptomatic or with transient and recovered symptoms, were selected. A C2, C3, C4 root deep cervical block and superficial block was performed, using a mixture of lidocaine and bupivacaine. A carotid endarterectomy with patch and without routine shunt insertion, with standard and neurological monitoring, was performed. RESULTS: During the study period, 94 carotid endarterectomies were done, 22 under regional anesthesia in 21 patients (12 male, age range 58-90 years old). Ninety five percent had hypertension, 52% smoked and 38% had renal dysfunction. One patient was converted to general anesthesia. Seventeen patients were discharged within 48 hours of the procedure and the rest, within 72 hours. There was no mortality or complications. CONCLUSIONS: Endarterectomy under regional anesthesia is less invasive, has excellent results and is well accepted by patients.

Aged↗
PubMed1999

An expert system for monitor alarm integration.

OBJECTIVE: Intensive care and operating room monitors generate data that are not fully utilized. False alarms are so frequent that attending personnel tends to disconnect them. We developed an expert system that could select and validate alarms by integration of seven vital signs monitored on-line from cardiac surgical patients. METHODS: The system uses fuzzy logic and is able to work under incomplete or noisy information conditions. Patient status is inferred every 2 seconds from the analysis and integration of the variables and a unified alarm message is displayed on the screen. The proposed structure was implemented on a personal computer for simultaneous automatic surveillance of up to 9 patients. The system was compared with standard monitors (SpaceLabs PC2), using their default alarm settings. Twenty patients undergoing cardiac surgery were studied, while we ran our system and the standard monitor simultaneously. The number of alarms triggered by each system and their accuracy and relevance were compared. Two expert observers (one physician, one engineer) ascertained each alarm reported by each system as true or false. RESULTS: Seventy-five percent of the alarms reported by the standard monitors were false, while less than 1% of those reported by the expert system were false. Sensitivity of the standard monitors was 79% and sensitivity of the expert system was 92%. Positive predictive value was 31% for the standard monitors and 97% for the expert system. CONCLUSIONS: Integration of information from several sources improved the reliability of alarms and markedly decreased the frequency of false alarms. Fuzzy logic may become a powerful tool for integration of physiological data.

Blood Gas Analysis↗
PubMed1999

Hemodilution does not alter the aortic-to-femoral arterial pressure difference in dogs.

INTRODUCTION: Distal arterial pressure normally differs from aortic pressure. This difference is modified by changes of vascular resistance. Hemodilution, due to decreased viscosity, decreases vascular resistance. Therefore, the difference between aortic and distal arterial pressures could be altered as well. We investigated whether acute hemodilution affected this difference in dogs. METHODS: Eleven mongrel dogs weighing 16.6 +/- 4.4 kg were anesthetized with pentobarbital and sufentanyl and mechanically ventilated. Arterial presssure was recorded using Millar catheter-tipped pressure transducers in the proximal aorta and in the distal femoral artery. An electromagnetic flowmeter probe was placed around the aorta. Effective downstream pressure was estimated by extrapolation of exponential arterial pressure decay during 3-second occlusion of the proximal aorta. Hemodilution was effected by removal of 30 ml/kg of blood and replacement with 60 ml/kg of warmed saline. In addition, the effects of 1 microg/kg phenylephrine and 4 microg/kg of sodium nitroprusside were measured before and after hemodilution. RESULTS: Hemodilution decreased hematocrit from 39 +/- 11.2% to 25.6 +/- 4.95%. Systolic and mean pressures were unchanged but aortic diastolic pressure decreased significantly, from 86 +/- 17 to 79 +/- 15 mmHg (p < 0.005). Peak systolic pressure was 13.5 +/- 7.2 mmHg higher in the femoral artery than in the aorta before, and 16 +/- 8.7 mmHg after, hemodilution (p > 0.05). Nitroprusside decreased the femoral to aortic peak systolic pressure difference from 14.3 +/- 6.3 to 7.7 +/- 15.3 mmHg, p = 0.05 before hemodilution and from 14.3 +/- 8.8 to 2.5 +/- 11 mmHg, p < 0.005 afterwards. Hemodilution significantly decreased the effective downstream pressure, from 44 +/- 9 to 36 +/- 6.8 mmHg in the aorta (p < 0.05), and from 51 +/- 2 to 37 +/- 3.1 mmHg in the distal femoral artery (p < 0.05). CONCLUSION: Acute hemodilution did not alter the aortic-to-distal arterial pressure difference in dogs.

Animals↗
PubMed1999

Cardiopulmonary bypass: new strategies for weaning from cardiopulmonary bypass.

This review focuses on weaning from cardiopulmonary bypass, a very critical time for patients and anaesthetists and frequently requiring major therapeutic effort. Few novel strategies for weaning have been described recently. Most drugs or approaches described during the review period are already well established. Emphasis is placed on the importance of non-cardiac factors, and on the importance of diastolic ventricular function as opposed to systolic function.

Journal Article↗
PubMed1999

[Minimally invasive coronary artery surgery].

BACKGROUND: There is a growing interest to perform a left internal mammary artery (LIMA) graft to the left anterior descending coronary artery (LAD) on a beating heart through a minimally invasive access to the chest cavity. AIM: To report the experience with minimally invasive coronary artery surgery. PATIENTS AND METHODS: Analysis of 11 patients aged 48 to 79 years old with single vessel disease that, between 1996 and 1997, had a LIMA graft to the LAD performed through a minimally invasive left anterior mediastinotomy, without cardiopulmonary bypass. A 6 to 10 cm left parasternal incision was done. The LIMA to the LAD anastomosis was done after pharmacological heart rate and blood pressure control and a period of ischemic pre conditioning. Graft patency was confirmed intraoperatively by standard Doppler techniques. Patients were followed for a mean of 11.6 months (7-15 months). RESULTS: All patients were extubated in the operating room and transferred out of the intensive care unit on the next morning. Seven patients were discharged on the third postoperative day. Duplex scanning confirmed graft patency in all patients before discharge; in two patients, it was confirmed additionally by arteriography. There was no hospital mortality, no perioperative myocardial infarction and no bleeding problems. After follow up, ten patients were free of angina, in functional class I and pleased with the surgical and cosmetic results. One patient developed atypical angina on the seventh postoperative month and a selective arteriography confirmed stenosis of the anastomosis. A successful angioplasty of the original LAD lesion was carried out. CONCLUSIONS: A minimally invasive left anterior mediastinotomy is a good surgical access to perform a successful LIMA to LAD graft without cardiopulmonary bypass, allowing a shorter hospital stay and earlier postoperative recovery. However, a larger experience and a longer follow up is required to define its role in the treatment of coronary artery disease.

Adult↗
PubMed1998

Estimation of ventricular volume and elastance from the arterial pressure waveform.

We propose that it is possible to estimate cardiovascular parameters from the arterial pressure waveform, including ventricular maximal elastance and end-diastolic volume, if cardiac output is also known. We tested this hypothesis by means of a parameter estimation algorithm applied to simulated arterial pressure signals. The program first estimated three coefficients representing products of passive parameters from the diastolic part of the simulated arterial pressure waveform. Second, it estimated three parameter products pertaining to the ventricular function from the systolic part of the waveform. Third, mean blood flow was entered, enabling the program to compute individual parameters. This program was tested on 200 computer-generated arterial pressure signals, obtained by simulating the model with random but bounded parameters. Correlation between estimated parameters with those actually used in the simulations was excellent. Even though the value of this computer simulation is limited to the simplified model used and requires experimental validation, it demonstrates that the technique is theoretically feasible.

Blood Flow Velocity↗
PubMed1998

Renal protection in patients undergoing cardiopulmonary bypass with preoperative abnormal renal function.

UNLABELLED: We prospectively studied the effects of renal protection intervention in 17 patients with preoperative abnormal renal function (plasma creatinine > 1.5 mg/dL) scheduled for elective coronary surgery. Patients were randomized to either dopamine 2.0 micrograms.kg-1.min-1 (Group 1, n = 10) or perfusion pressure > 70 mm Hg during cardiopulmonary bypass (CPB) (Group 2, n = 7). Glomerular filtration rate and effective renal plasma flow were measured with inulin and 125I-hippuran clearances before the induction of anesthesia, after sternotomy and before CPB, during hypo- and normothermic CPB, after sternal closure, and 1 h postoperatively. Plasma and urine electrolytes were measured, and free water, osmolar, and creatinine clearances, as well as fractional excretion of sodium and potassium, were calculated before and after surgery. Significant differences between groups were found before CPB for glomerular filtration rate (higher in Group 1), urine output (2.0 vs 0.29 mL/min in Group 1 versus Group 2), urinary creatinine (66 vs 175 mg/dL), urinary osmolarity (370 vs 627 mOsm/L), osmolar clearance (2.1 vs 0.7 mL/min), and urinary potassium (33 vs 71 mEq/L). There were no differences between groups during hypo- and normothermic CPB. After CPB, the only difference was a slightly higher urinary creatinine in Group 2. Renal plasma flow was lower than normal in all patients before the induction of anesthesia. A nonsignificant trend toward increased flow was seen during hypothermic CPB. Filtration fraction was high before CPB, which suggests efferent arteriolar vasoconstriction, descending toward normal during and after CPB. The same pattern of changes was present in both groups. In conclusion, there were no clinically relevant differences between the two treatment modalities during and after CPB. However, significant differences were observed before CPB, when dopamine seemed to partially revert renal vasoconstriction. IMPLICATIONS: Two protective interventions were compared in patients undergoing heart surgery to prevent deterioration of renal function; these were dopamine infusion throughout the operation and phenylephrine infusion during cardiopulmonary bypass. We found clinically relevant differences only during surgery before cardiopulmonary bypass.

Aged↗
PubMed1998

Renal preservation in cardiac surgery.

There is no conclusive evidence that any pharmacological intervention is able to offer effective protection for the kidneys during cardiac surgery. More research is needed into the underlying mechanisms of postoperative renal failure, specifically with regard to the possible role played by endothelial factors and inflammatory response.

Journal Article↗
PubMed1997

Surface properties after a simulated PLA2 hydrolysis of pulmonary surfactant's main component, DPPC.

The inflammation, so conspicuous in cases of respiratory distress, pneumonia, and asthma, is associated with an airway invasion of plasma proteins and a release into the airway lumen of phospholipase A2 (PLA2). This enzyme catalyzes hydrolysis of surfactant phospholipids, the most abundant and important of which is dipalmitoylphosphatidylcholine (DPPC). Its hydrolysis yields equimolar proportions of lysophosphatidylcholine and palmitic acid (LPC/PA). Exact quantification of DPPC hydrolysis is complicated. Consequently, it was decided to simulate hydrolysis whereby DPPC (3 mg/ml) was gradually replaced with LPC/PA (3 mg/ml), yielding seven different grades of simulated hydrolysis: 0, 17, 33, 50, 67, 83, and 100%. Surface properties of the seven mixtures were examined with various concentrations of albumin added. The Bubble Surfactometer was used to study the surfactant film that is given time to develop at a spherical air-liquid interface. A Capillary Surfactometer was used to evaluate surface properties required for airway patency. It was found, using both of these instruments that the surface activity improved as the simulated hydrolysis of DPPC to LPC/PA increased toward 100%, where the activity was maximal. With the Bubble Surfactometer, surface activity of LPC/PA, 3 mg/ml, improved as albumin concentration increased, and when it reached 15 mg/ml, surface tension became 0 mN/m after only 2 min. With the Capillary Surfactometer, requiring a much faster film adsorption, albumin had an opposite effect. LPC/PA alone maintained patency 100% of the time studied, while even a minimal addition of albumin inhibited surfactant function.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1997

Arterial pressure-flow relationship in patients undergoing cardiopulmonary bypass.

We determined the arterial pressure-flow relationship experimentally by means of step changes of blood flow in 30 adult patients undergoing cardiopulmonary bypass (CPB). Anesthesia technique was uniform. CPB was nonpulsatile; hypothermia to 25-28 degrees C, and hemodilution to 18%-25% hematocrit were used. During stable bypass, mean arterial pressure was recorded first with blood flow 2.2 L.min-1.m-2. Flow was then increased to 2.9 L.min-1.m-2 for 10 s and reverted to baseline for 1 min. Then it was decreased to 1.45 L.min-1.m-2 for 10 s, and reverted to baseline for 1 min. Subsequently, it was decreased to 0.73 L.min-1.m-2 for 10 s and then reverted to baseline. Similar sets of measurements were repeated after 0.25 mg of phenylephrine and once the patient was rewarmed. The pressure-flow function was individually determined by regression, and the critical pressure estimated by extrapolation to zero flow. All patients had zero-flow critical pressure during hypothermia, with a mean value of 21.8 +/- 6.4 mm Hg (range 8.8-38.9). It increased after 0.25 mg phenylephrine to 25.4 +/- 7.2 mm Hg (range 12.2-43.9, P < 0.001). During normothermia, critical pressure was 21.2 +/- 5 mm Hg (range 13.4-30.9), not significantly different from hypothermia. During hypothermia, the slope of the pressure-flow function (i.e., resistance) was 14.9 +/- 3.5 mm Hg.L-1.min-1.m-2 (range 7.6-22.1). It increased significantly (P < 0.001) after phenylephrine, to 19.7 +/- 6.2 mm Hg.L-1.min-1.m-2 (range 11.4-40.5), and returned to 15.4 +/- 3.4 mm Hg.L-1.min-1.m-2 (range 10.1-24.2) during normothermic bypass. Systemic vascular resistance appeared to vary reciprocally with blood flow, although this finding may represent a mathematical artifact, which can be avoided by using zero-flow critical pressure in the vascular resistance equation.

Adult↗
PubMed1997

[Myocardial revascularization with one and two mammary arteries: clinical results and long-term follow-up].

BACKGROUND: Coronary bypass grafts made with internal mammary artery have better long-term results than those made with saphenous vein. It is possible that the use of both mammary arteries would lead to even better results. AIM: To compare the long-term survival and the incidence of new coronary events of patients, in whom one or two mammary arteries were used as coronary bypass grafts. PATIENTS AND METHODS: One hundred and eight randomly selected patients who received one mammary artery for myocardial revascularization and 108 patients, matched for prognostic factors, who received two mammary arteries were studied. These patients were followed for a mean of 4 years (range 1 to 12 years). Operative complications, hospital mortality and long-term probability of being free of disease were compared in both groups. RESULTS: Operative mortality was similar in both groups (0.9%). Patients that received two mammary arteries had a higher frequency of operative wound complications. Long-term survival was 84% in patients who received one and 83% in patients who received two mammary arteries. The probabilities of being free of myocardial infarction (92 and 82% respectively) and angina (94 and 86% respectively) were lower in the later group. CONCLUSIONS: Patients who received two mammary arteries had a higher probability of a long term disease free survival than patients who received one mammary artery.

Disease-Free Survival↗
PubMed1997

[Abdominal aortic aneurysm: course of morbimortality of elective surgery in 20 years].

Abdominal aortic aneurysms (AAA) usually undergo progressive dilatation and eventually may rupture, complication that carries a high mortality rate. If certain clinical conditions, like operative risk and aortic diameter are met, all patients should be considered for surgical repair. Analysis of our results with the surgical treatment of asymptomatic AAA prompted this study. Out of 479 consecutive patients operated because of AAA between 1976 and 1995, 378 (79%) were electively treated. Two decades: 1976-85 (101 patients) and 1986-95 (277 patients) were compared as far as associated medical conditions, surgical procedures, complications and mortality rate. There was no difference in age, sex, risk factors and aortic diameter. During the second decade we favoured the use of aortic tube grafts (53% vs 25%, p < 0.01) and epidural anesthesia (94% vs 35%, p < 0.01). During the last decade only 53.3% of the patients received blood transfusion, compared to 95.3% during the first period (p < 0.001). Operative mortality decreased from 5.94% to 0.72% (p < 0.05). Postoperative hospital stay diminished from 11.2 +/- 8.2 to 9.6 +/- 6.3 days (p < 0.05). These results compare favourably with those reported from other academic centers and support our therapeutic approach. Our contemporary surgical results serve as a reference for future clinical evaluation of endovascular procedures currently under investigation.

Aged↗
PubMed1996

Comparison of isoflurane, halothane and fentanyl in patients with decreased ejection fraction undergoing coronary surgery.

The aim of the study was to compare three anaesthetic agents in patients with ejection fraction below 0.40 subjected to coronary revascularization surgery. Twenty five elective coronary surgical patients with ejection fraction below 0.40 were prospectively studied. Premedication was pethidine 1 mg/kg and induction was fentanyl 0.03 mg/kg and pancuronium 0.1 mg/kg. The patients were randomized to one of three maintenance techniques (fentanyl, isoflurane or halothane). Radial arterial pressure, heart rate, right atrial pressure, pulmonary arterial and occluded pressures, and thermodilution cardiac output were measured, and cardiac index and resistance calculated, at the following times: before induction; 5 min after intubation; 2 min after sternotomy; immediately after discontinuation of bypass; 15 min afterwards; immediately after sternal closure; during suture of the skin; 5 min after arrival in the postoperative care unit; and 60 min postoperatively. Mean arterial pressure decreased significantly in the isoflurane group and nonsignificantly in the halothane group after induction. Cardiac index decreased significantly in the isoflurane group and nonsignificantly in the halothane group after induction and after sternotomy. Neither pressure nor flow decreased in patients receiving fentanyl. Following weaning from cardiopulmonary bypass, systemic vascular resistance decreased significantly in all groups. Cardiac index, however, did not increase above control values and arterial pressure consequently decreased; there was no significant difference between groups.

Adjuvants, Anesthesia↗