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Biomedical subjects

G Silvay

Publications and source records attributed to G Silvay.

At least 19 recordsLinked to original sources
PubMed1995

Cardiopulmonary bypass for adult patients: a survey of equipment and techniques.

OBJECTIVES: The techniques and equipment used for cardiopulmonary bypass for adult cardiac surgery vary among institutions and may change over time. This study sought to document the changing patterns of practice. DESIGN: Voluntary survey of meeting participants. SETTING: 13th Annual San Diego Cardiothoracic Surgery Symposium (February 1993). PARTICIPANTS: There were 331 responses from perfusionists (79.5%), cardiac surgeons (11.2%), and anesthesiologists (6.3%). The majority of these participants were from institutions where more than 1,000 cardiac operations were performed annually. MEASUREMENTS AND MAIN RESULTS: It was found that 91.5% of the respondents used membrane oxygenators currently, compared with 5% in 1982 (as reported in a previous survey). Over 80% of the institutions surveyed used some type of perioperative cell-salvaging technique. Arterial line filters were used by 92% of the respondents compared with 64% in 1982. Also, 80% of the respondents were aware of the availability of leukocyte-depleting filters. CONCLUSIONS: The probable reasons for the increased utilization of membrane oxygenators and arterial line filters include less damage to the formed elements of blood, fewer gaseous microemboli, and better control of carbon dioxide elimination and oxygenation. The authors anticipate that future surveys will document increased use of leukocyte-depleting filters because of the literature implicating neutrophils as mediators of tissue destruction in various disease processes, including myocardial reperfusion injury.

Adult↗
PubMed1995

Autologous platelet-rich plasmapheresis: risk versus benefit in repeat cardiac operations.

Preoperative platelet-rich plasmapheresis has been suggested as a means of reducing homologous blood transfusions in cardiac surgical patients. The current study evaluated this technique in patients undergoing repeat cardiac operations. Fifty-two patients undergoing repeat myocardial revascularization and/or valve replacement were evaluated in a prospective randomized controlled study design. Autologous platelet-rich plasma (PRP) was harvested after the induction of anesthesia in the experimental group. After reversal of heparin, each patient received his or her autologous plasma. Patients in the control group did not have plasmapheresis and received standard transfusion therapy if coagulation variables were abnormal and a coagulopathy was clinically evident. Routine coagulation tests, thromboelastography (TEG), perioperative bleeding, and transfusion requirements were compared in the two groups. Forty-four patients completed the study. A significantly larger volume of packed red blood cells (PRBCs) was transfused in the PRP group than in the control group (P = 0.03). Platelet and fresh frozen plasma (FFP) transfusions did not differ between the two groups. Mediastinal tube drainage did not differ between the two groups. During PRP infusion, 60% of the patients required treatment for moderate hypotension (mean arterial pressure [MAP] < 60 mm Hg). Only 16% of control patients required treatment for hypotension during the comparable time period (P < 0.05). No patient who completed the study returned to the operating room for postoperative bleeding. These data suggest that PRP did not reduce postbypass bleeding or transfusion requirements in repeat cardiac surgical patients. Moreover, the incidence of hypotension during PRP reinfusion introduces a potential risk to the procedure in the absence of any obvious benefit.

Blood Coagulation Tests↗
PubMed1992

Comparison of propofol versus ketamine for anesthesia in pediatric patients undergoing cardiac catheterization.

Intravenous propofol was compared with ketamine in 20 pediatric patients undergoing cardiac catheterization. The study patients were randomly assigned to treatment groups so that 10 patients received ketamine and 10 patients received propofol. The hemodynamic responses and recovery characteristics of the two groups were compared. On induction of anesthesia, seven patients in the propofol group experienced a transient decrease in mean arterial blood pressure greater than 20% of baseline accompanied by mild arterial desaturation in four patients. Only one patient in the ketamine group experienced such a decrease in arterial blood pressure. This was the only significant difference (P less than 0.05) in hemodynamic effects between the two groups. Time to full recovery (mean +/- SD) was significantly less in the propofol group (24 +/- 19 min vs 139 +/- 87 min, P less than 0.001). In the ketamine group only, significant correlations (P less than 0.05) included time to full recovery with duration of anesthetic (r = 0.71) and time to full recovery with total drug dose per kilogram (r = 0.82). The authors conclude that propofol anesthesia is a practical alternative for pediatric patients undergoing elective cardiac catheterization and may be preferable to ketamine because of the significantly shorter recovery time.

Anesthesia↗
PubMed1991

Haemodynamic response to induction of anaesthesia with ketamine/midazolam.

The haemodynamic responses following induction of anaesthesia with ketamine and midazolam have not been determined previously. Twenty adult patients for elective myocardial revascularization were randomized to two regimens for induction of anaesthesia. Patients in Group I received ketamine, 2 mg.kg-1, and midazolam, 0.2 mg.kg-1 and those in Group II received ketamine, 2 mg.kg-1, and midazolam, 0.4 mg.kg-1. Measurements were recorded at baseline, 1 min post-induction, and at one, three, five and ten minutes after tracheal intubation. Tachycardia and hypertension (greater than 20% increases from awake baseline values) were treated with esmolol, 250 micrograms.kg-1. There were 11 patients in Group I and nine patients in Group II. There were no significant intergroup differences in demographic or haemodynamic variables. Both groups had decreases (P less than 0.05), in stroke volume, pulmonary capillary wedge pressure, and right ventricular end-diastolic volume at multiple study intervals following anaesthetic induction. None of these changes required clinical intervention. Five patients (all in Group II) had hypertensive responses to tracheal intubation. Preoperative hypertension (mean arterial pressure greater than or equal to 100 mmHg) was a predictor (P less than 0.05) of a hypertensive response to intubation, independent of the midazolam dose. Intravenous ketamine and midazolam was associated with a high incidence (25%) of haemodynamic responses to tracheal intubation. The higher dose of midazolam did not provide any haemodynamic advantage.

Aged↗
PubMed1989

Ketamine: an update on the first twenty-five years of clinical experience.

In nearly 25 years of clinical experience, the benefits and limitations of ketamine analgesia and anaesthesia have generally been well-defined. The extensive review of White et al. and the cardiovascular review of Reves et al. are broad in their scope and have advanced the understanding of dissociative anaesthesia. Nevertheless, recent research continues to illuminate different aspects of ketamine pharmacology, and suggests new clinical uses for this drug. The identification of the N-methylaspartate receptor gives further support to the concept that ketamine's analgesic and anaesthetic effects are mediated by separate mechanisms. The stereospecific binding of (+)ketamine to opiate receptors in vitro, more rapid emergence from anaesthesia, and the lower incidence of emergence sequelae, make (+)ketamine a promising drug for future research. Clinical applications of ketamine that have emerged recently, and are likely to increase in the future, are the use of oral, rectal, and intranasal preparations for the purposes of analgesia, sedation, and anaesthetic induction. Ketamine is now considered a reasonable option for anaesthetic induction in the hypotensive preterm neonate. The initial experience with epidural and intrathecal ketamine administration has not been very promising but the data are only preliminary in this area. The use of ketamine in military and catastrophic settings is likely to become more common. The clinical availability of midazolam will complement ketamine anaesthesia in several ways. This rapidly metabolized benzodiazepine reduces ketamine's cardiovascular stimulation and emergence phenomena, and does not have active metabolites. It is dispensed in an aqueous medium, which is usually non-irritating on intravenous injection, unlike diazepam. The combination of ketamine and midazolam is expected to achieve high patient acceptance, which never occurred with ketamine as a sole agent. Finally, it is necessary to point out the potential for abuse of ketamine. While ketamine is not a controlled substance (in the United States), the prudent physician should take appropriate precautions against the unauthorized use of this drug.

Administration, Rectal↗
PubMed1988

Response of lower esophageal contractility to changing concentrations of halothane or isoflurane: a multicenter study.

A multiple-center study was performed to determine the relationship between lower esophageal contractility, clinical signs, and anesthetic concentration as expressed by minimum alveolar concentration (MAC). One hundred four American Society of Anesthesiologists Class I through III patients were exposed to isoflurane (with and without nitrous oxide) or halothane in concentrations of 0.5, 1.0, and 1.5 MAC. Heart rate and systolic blood pressure were continuously monitored. Both the amplitude and frequency of spontaneous and provoked lower esophageal contractions were measured in situ by using a 24-F probe equipped with provoking and measuring balloons. Combined results demonstrated statistically significant correlations (P less than 0.001) between lower esophageal contractility and MAC. Spontaneous lower esophageal contractions decreased from 1.10 +/- 0.12 (SEM) contractions per minute (0.5 MAC) to 0.42 +/- 0.05 (1 MAC) to 0.18 +/- 0.05 (1.5 MAC). Provoked lower esophageal contractility values decreased from 45 +/- 4 mm Hg (0.5 MAC) to 29 +/- 3 (1 MAC) to 19 +/- 2 (1.5 MAC). Heart rate changes did not correlate with MAC, and systolic blood pressure correlated in only one of three centers. Intracenter and intercenter analyses failed to demonstrate a significant relationship between lower esophageal contractility and heart rate or systolic blood pressure. No intracenter differences in either amplitude or frequency of lower esophageal contractions were observed, despite differences in volatile agents, induction techniques and agents, patient populations, and durations of anesthesia.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1988

Open heart surgery in patients in the eighth and ninth decades of life.

One hundred fifty-one patients aged 70-89 years underwent a variety of open heart surgical procedures during a period of 1 year. We divided these patients into two groups: Group A was comprised of 127 patients between 70 and 79 years of age. In group B, 24 patients were between 80 and 89 years of age. These patients underwent elective open heart surgery. Information was retrieved retrospectively from the computerized data pool of the cardiothoracic registry in our institution. Statistical analysis in these two groups revealed no significant differences in any of the evaluated factors. We concluded that age should not be a contraindication for cardiac operations.

Aged↗
PubMed1986

The effect of temperature, mean arterial pressure, and cardiopulmonary bypass flows on somatosensory evoked potential latency in man.

Median nerve somatosensory evoked potentials were recorded in 21 patients undergoing cardiac surgical procedures utilizing cardiopulmonary bypass, in order to establish the effects of hypothermia, reductions in mean arterial pressure, and alterations in cardiopulmonary bypass flows on evoked potential latency. Induction and maintenance of anesthesia with fentanyl caused a significant prolongation of latency of the first cortical peak. Temperature changes were linearly correlated with changes in latency for peaks recorded from Erb's point (r = -0.843, p less than 0.01) and the contralateral cortex (r = 0.843, p less than 0.01). There was no significant effect of mean arterial pressure or cardiopulmonary bypass flow reductions on latencies under the conditions of this study. Our results emphasize the importance of monitoring peripheral and first cortical peak latencies in evaluating somatosensory evoked potentials. It is suggested that peak latency prolongations beyond those predicted by temperature alterations may be indicative of hypoperfusion.

Adult↗
PubMed1980

Continuous ketamine infusion for one-lung anaesthesia.

The mechanism which normally affects distribution of blood flow through unventilated areas of the lung is hypoxic pulmonary vasoconstriction; this acts to divert the blood to well ventilated alveoli, resulting in a better ratio of ventilation to perfusion. Several reports have focused attention on the reduction or abolition of this reflex in the unventilated lung by most of the volatile anaesthetic agents used in clinical practice. This response was not abolished by the intravenous anaesthetic agents. One hundred and ten patients undergoing elective pulmonary resection were studied to evaluate the effect of a continuous infusion of ketamine during one-lung anaesthesia, by observing the changes in PaO2 as a reflection of shunt. Ketamine was chosen as the intravenous agent for its positive inotropic and chronotropic action. Additionally, by providing both analgesia and hypnosis, we were able to administer inspired oxygen concentrations of 50-100 per cent without concern that the patient might have recall for events during operation. We have demonstrated that in all cases a PaO2 in excess of 9.31 kPa (70 torr) was achieved with ketamine and FIO2 1.0 as well as an increase in shunt fraction from 25.9 per cent (FIO2 0.5) to 36.0 per cent (FIO2 1.0). We feel that ketamine provides a satisfactory alternative to the volatile agents for one-lung anaesthesia in patients where relative hypoxaemia might be unacceptable during operation.

Adult↗