Search PubMed⌕ Search

Biomedical subjects

S Ramanathan

Publications and source records attributed to S Ramanathan.

At least 109 records · Page 6Linked to original sources
PubMed1983

Maternal and fetal effects of prophylactic hydration with crystalloids or colloids before epidural anesthesia.

Prophylactic intravenous hydration decreases the incidence and severity of hypotension due to obstetric epidural anesthesia. This study assesses whether infusion of normal serum albumin (NSA) offers any advantages over Ringer's lactate (RL) solution. Sixty patients scheduled for elective cesarean sections were divided into three equal groups. Group 1 received 1200 ml of RL; group 2, 700 ml of RL plus 500 ml of 5% NSA; and group 3, 1000 ml of RL plus 200 ml of 25% NSA. In group 1, the concentrations of serum albumin (SA) decreased from 3.5 +/- 0.3 (mean +/- SD) to 3 +/- 0.2 g/dL (P less than 0.01) and plasma oncotic pressure (POP) from 20 +/- 3 to 17 +/- 3 torr (P less than 0.005) immediately after hydration. In group 2, SA remained unchanged, but POP decreased from 21 +/- 2 to 19 +/- 2 torr (P less than 0.005). In group 3, SA increased from 3.6 +/- 0.5 to 3.9 +/- 0.3 g/dL (P less than 0.01) and POP from 19 +/- 2 to 21 +/- 2 torr (P less than 0.0025). Neither SA nor POP levels differed among the groups 24 h later; however, both SA and POP were significantly lower than preinfusion values in all groups at 24 h. The incidence of maternal hypotension, neonatal Apgar scores, and acid-base status also were comparable among the groups (X2 analysis). Because low POP may predispose to postoperative pulmonary morbidity, the incidence of this complication was studied in the mothers by using a point scoring system (based on the presence of symptoms and physical signs) and also by measuring AaDO2 gradients. Neither pulmonary morbidity scores nor AaDO2 gradients differed significantly in the three groups. It is concluded that both crystalloid and colloid prehydration produce equally satisfactory maternal and fetal outcomes.

Adult↗
PubMed1982

Meperidine-promethazine combination and learning function of mice and of their progeny.

Twenty mice aged three to four months and trained to find food in a six compartment maze after a 24 hour fast, were divided into two equal groups. For just over one month the group which had received intraperitoneal meperidine 3 microgram.g-1 and promethazine 1.66 microgram.g-1 performed significantly slower than the group which had received intraperitoneal physiological saline. Because of this marked effect, it was decided to investigate the action of the drug combination on brain development and to assess whether it produced permanent retardation in learning function. The dams of a second group of 12 mice were, therefore, given either the same dose of drug combination or saline. At the age of seven weeks, the six pups born to dams which had received intramuscular saline and the six born to dams which were given intramuscular promethazine with meperidine performed equally well in a series of tests conducted in a T maze and in the six compartment maze after a 24 hour fast. In the T maze they had to distinguish between the presence of food provided in diminishing amounts or no food. In the six compartment maze they were tested with multiple maze pattern sequences. Meperidine and promethazine given during early labor does not permanently affect the learning function of the progeny of mice.

Aging↗
PubMed1982

Continuous and simultaneous on-line measurements of VO2 and VCO2 during endotracheal anesthesia.

A single method was developed for the continuous measurement of oxygen consumption (VO2) and carbon dioxide production (VCO2) during endotracheal anesthesia. The total vented flow from a Bain circuit was measured during anesthesia in 28 adult patients and was found to attain at least 97% of a 6-L/min fresh gas inflow (FGI). Therefore, the circuit overflow was assumed to approximate the FGI. Total volume of vented oxygen was calculated by multiplying FGI by oxygen concentration in the vented (mixed expired) gas. VO2 was assessed as the difference between the oxygen volumes entering and leaving the circuit. VCO2 was derived from the product of FGI and mixed expired CO2 concentration. VO2 measured on the Bain circuit correlated with measurements made on a non-breathing circuit (n = 60 pairs, r = 0.99). A good correlation was also found between VCO2 obtained on both circuits (n = 60 pairs, r = 0.99).

Adolescent↗
PubMed1982

Uterine contractions and the spread of local anesthetics in the epidural space.

Local anesthetics injected into the epidural space during a uterine contraction are commonly believed to produce a higher than usual level of anesthesia. This was evaluated in 34 parturients undergoing continuous lumbar epidural labor analgesia. The patients were divided into two equal groups. In group A, the inducing dose (2% chloroprocaine, 8 ml) was injected during an active uterine contraction and the top-up dose was injected between contractions. In group B, the injection sequence was reversed. Irrespective of the time of injection, in relation to uterine contractions, approximately 16 dermatomal segments were blocked in both groups. It is concluded that uterine contractions do not affect spread of local anesthetic solution in the epidural space.

Adult↗
PubMed1982

Oxygen transfer from mother to fetus during cesarean section under epidural anesthesia.

The correlation between maternal PaO2 levels and umbilical vein (UV) and umbilical artery (UA)PO2 levels was studied in 40 healthy patients undergoing elective cesarean sections under lumbar epidural anesthesia. Patients were divided into four equal groups. Each group inhaled oxygen at a FIO2 of 0.21, 0.47, 0.74 (in nitrogen), or 1.0. Maternal arterial samples and fetal UV and UA samples were collected at the time of delivery. Maternal PaO2 levels increased from 96 +/- 4 (1 SE) torr during exposure to to a FIO2 of 0.21 to 232 +/- 6, 312 +/- 16, and 423 +/- 6 torr while breathing FIO2 of 0.47, 0.74 and 1.0, respectively. UV PO2 levels increased from 28 +/- 1 to 36 +/- 1.5, 41 +/- 1.3 and 47 +/- 1.2 torr in the hyperoxic groups. UA PO2 levels increased from 15 +/- 0.7 to 19 +/- 0.8, 21 +/- 0.3, and 25 +/- 1.8 torr, respectively. Oxygen saturation and blood O2 contents increased in maternal and fetal blood. Maternal arterial, UV, and UA base excess values in the hyperoxic groups were significantly higher than in the normoxic groups. There was no difference in 1- or 5-minute Apgar scores between the normoxic and hyperoxic groups. It is concluded that maternal hyperoxia improves fetal oxygen stores and acid-base status during cesarean section under epidural anesthesia.

Adult↗
PubMed1982

Coaxial catheter for humidification during jet ventilation.

A coaxial jet ventilation catheter capable of entraining liquid water by Venturi effect was assembled by inserting an epidural catheter (water injector tube) into a 69-cm-long, 3-mm-i.d., outer jet delivery tube. Gas jet flow in the outer tube produced a negative pressure in the inner injector tube. The entrainment pressure could be varied by increasing or decreasing the distance between the injector and jet portals. The quantity of entrained water could thus be regulated between 8 +/- 1 to 44 +/- 2 mg/L of gas by decreasing this distance from 3.5 to 0.5 cm. The catheter was used to deliver low- or high-frequency jet ventilation for 4 hours in dogs (five dogs per mode of ventilation) and for 2 hours in patients (12 patients per mode). Patients receiving either mode of ventilation were divided into two equal groups. One group was ventilated with dry gases and the other with humidified gases containing 44 mg H2O/L. Ciliated epithelial cells were obtained by bronchial lavage at the onset and termination of each study. Damage to ciliated cells was assessed numerically by a point scoring system. The coaxial catheter produced adequate pulmonary ventilation both in dogs and humans during both modes of ventilation. The human tracheobronchial cellular score decreased approximately 21% after unhumidified low- and high-frequency ventilation. However, the score did not change significantly in patients who received humidified gases, indicating efficient humidification by the coaxial catheter.

Adult↗
PubMed1981

A circle system with a rotating wick vaporizer.

The humidity output of a circle system was raised to 28 mg H2O/l by the use of a modified rotating wick vaporizer placed in the center of the soda lime canister and coaxial inspiratory and expiratory limbs. Both the fresh gas inflow and the expired gases passed through the lime and reached a compartment below it. The bag/ventilator connector, bearing a pressure relief valve, opened on the lateral wall of that compartment. Gases returning to the inspiratory valve passed: (1) through a tube in the canister connecting the inferior compartment to the vaporizer above water level, (2) through the upper portion of the vaporizer and around the rotating wick, and (3) through a tube emerging from the top of the vaporizer to reach the inspiratory valve. Thus inspired gases were humidified by the rotating wick constantly replenishing its water content warmed by the reaction of neutralization. The use of coaxial inspiratory and expiratory limbs reduced water condensation outside the canister.

Anesthesiology↗
PubMed1981

Decreases in electric thoracic impedance during transurethral resection of the prostate: an index of early water intoxication.

Thoracic impedance of 18 patients undergoing transurethral resection of the prostate was measured 15 minutes preoperatively, and 30 and 60 minutes after the start of the operation. Impedance variations were compared to variation in 1) cardiac output, 2) serum sodium osmolality and 3) alveolar-arterial oxygen tension difference. Thoracic impedance, initially 24.6 plus or minus 0.3, decreased to 23.8 plus or minus 0.5, 30 minutes after the onset of the operation (p less than 0.0005) and 22.9 plus or minus 0.5, 30 minutes later (p less than 0.01 from previous reading and 0.0005 from control). Patients in whom impedance had decreased 10 per cent or more from control values received 10 mg. furosemide intravenously 60 minutes after the onset of the operation. This therapy permitted the restoration of impedance values, cardiac output, alveolar-arterial oxygen tension difference and serum sodium osmolality to values statistically similar to those found in the 10 patients who had not sustained such precipitous decreases in impedance within 60 minutes. We believe that the measurement of thoracic impedance during transurethral prostatic surgery offers the most sensitive index of early water intoxication. Measurements can be obtained without delay in the operating room and, thus, permit immediate correction of the condition.

Aged↗
PubMed1981

Urinary excretion of cyclic nucleotides and phosphate in response to parathyroid hormone and calcitonin in man.

The response to parathyroid hormone (PTH) and calcitonin (CT) was studied in eight children with various bone diseases by determining the serum calcium (Ca) and phosphate (P) concentration, urinary phosphate excretion rate, renal phosphate clearance, the percentage of filtered phosphate reabsorbed by the renal tubule (%TRP), creatinine clearance (Ccr), urinary cyclic adenosine 3',5' monophosphate excretion rate (UcGMPV). Administration of PTH caused no significant change in serum Ca and P values, whereas CT produced a decrease in Ca (delta Ca, -1.4 +/- 0.1 mg/100 ml) and P (delta P; -1.1 +/- 0.1 mg/100 ml). There was an increase in UcAMP V (delta UcAMP; 437 +/- 74 nmoles/min/100 ml Ccr) without any significant change in UcGMPV after administration of PTH. Phosphaturia was produced by both PTH (delta TRP, -18 +/- 3%) and CT (delta TRP, -13 +/- 2%). However, CT did not elicit any increase in either UcAMPV or UcGMPV.

Adolescent↗
PubMed1981

A percolator vaporizer heated by reaction of neutralization of lime by carbon dioxide.

To improve the humidification of anesthetic gases without use of electricity and its associated dangers the principle of the coffee percolator has been applied to a new vaporizer. Coffee percolators work by introducing steam-driven spurts of boiling water into a perforated coffee container. A water vaporizer, which functions on this principle, was used substituting the fresh gas inflow of an anesthesia machine as the driving gas. The vaporizer was placed in the center of the lime canister of a circle system with coaxial-valved respiratory limbs. The gas-water mixture percolated through a multiple wire mesh gauze filter that prevented the introduction of water droplets into respiratory channels. All gases emerging from the bottom of the canister and reaching the inspiratory valve passed through the vaporizer above water level. The circuit delivered gases containing 4 to 9 mg of H2O/L above saturated values at ambient temperature (20.5 mg of H2O/L) within 15 minutes, if the fresh gas inflow was set at 2.5 L/min.

Anesthesiology↗
PubMed1981

Routine cytodiagnosis of pulmonary malignancies.

Anesthesiologists normally discard the material routinely suctioned from the tracheal tube of patients under general endotracheal anesthesia. We preserved, and later examined microscopically, specimens from 10,621 patients. We found 11 cytologically abnormal smears from subjects with unsuspected pulmonary involvement, an incidence slightly more than 1:1,000. The accuracy of our method was assessed by calculation of the percent of abnormal smears obtained from patients with prediagnosed bronchogenic carcinomas: 40% when suctioned material was immediately spread on slides, and 67% when cellular concentration was achieved by mucolysis followed by filtration or centrifugation. Secretions normally discarded can reveal much information that would otherwise be missed. Our method may be useful if applied to patients at risk (heavy smokers, workers with asbestos, nitrosamine, or benzopyrine, miners of radioactive material, etc) who undergo general anesthesia for incidental surgery.

Adolescent↗
PubMed1981

Exposure to halothane and enflurane affects learning function of murine progeny.

This study was conducted to assess the learning function of murine progeny born of mothers that had received either 1% or 2% halothane or 2% or 4% enflurane, on days 6 and 10 or days 14 and 17 or gestation. Their timed performance at the age of 6 to 7 weeks was compared in a maze with that of control mice of similar ages that had not been exposed to anesthetics prenatally. All mice exposed to halothane in utero performed poorly at first, especially the group with mothers exposed to 2% halothane on days 14 and 17 of pregnancy. By the 10th training period, the performance of all mice improved but remained significantly slower than control mice. The offsprings of mice exposed to enflurane also performed poorly on the first training period, but between the fifth and seventh training periods, made statistically significant progress. However, they too remained slower in maze performance than control mice. Although blood pressure and arterial blood gas studies were only performed on two pregnant mice, data obtained suggest that the anesthetics did not have sufficient effect on respiration to affect our results. Second generation offspring, born to dams exposed to 2% halothane in utero late in pregnancy and sired by normal unexposed males, were also consistently slower than control mice, indicating a possible genetic effect induced by the anesthetic.

Animals↗
PubMed1980

Ontogenetic development of isoproterenol subsensitivity of myocardial adenylate cyclase and beta-adrenergic receptors in spontaneously hypertensive rats.

[3H]Dihydroalprenolol binding and adenylate cyclase activity in the myocardial membranes of Kyoto Wistar normotensive rats and spontaneously hypertensive rats were compared at various stages of postnatal development ranging from 2 to 36 weeks. Basal as well as agonist-stimulated myocardial adenylate cyclase activity was consistently decreased in spontaneously hypertensive rats as compared to normotensive rats as early as 2 weeks of age with significant differences (P < 0.05) observed after 6 weeks of age. When results were expressed as percent stimulation over the basal activity, only isoproterenol plus GTP-stimulated enzyme activity was reduced by 25--30% in spontaneously hypertensive rats, suggesting a specific loss of stimulation by isoproterenol in hypertensive animals. The number of [3H]dihydroalprenolol binding sites of KD for dihydroalprenolol binding were comparable between spontaneously hypertensive and normotensive rats at 3, 6 and 12 weeks of age. The competition of isoproterenol with [3H]dihydroalprenolol for the specific binding sites showed that the affinity of isoproterenol binding was decreased 3--4-fold in spontaneously hypertensive compared with normotensive rats. With postnatal development in age, basal as well as agonist-stimulated activities decreased progressively in both spontaneously hypertensive and normotensive rats. Similarly, the number of [3H]dihydroalprenolol binding sites decreased with the development in age, whereas affinity of dihydroalprenolol binding increased up to 12 weeks of age. These results therefore suggest that adenylate cyclase activity and the number of beta-adrenergic receptors in rat heart, decrease with age and that in hypertension, specific decrease in isoproterenol stimulation of cyclase appears at all stages of development.

Adenylyl Cyclases↗
PubMed1980

A microprocessor computer program. An aid to the International System of Units.

The transition from the scientific system of measurements used in the United States to the Système International creates difficulties for Americans who consult European or Canadian journals. Similar difficulties occur when they want to publish abroad. We have developed a program for the portable microcalculator, which may be coupled selectively to a recorder. Two types of programs are used on 7.5 X 1.5-cm electromagnetic cards. Program P1 is used with the recorder and program P2 with the calculator only.

Abbreviations as Topic↗
PubMed1980

Considerations on impedance cardiography.

Impedance cardiography is an electronic plethysmographic technique which provides information on cardiac stroke index, myocardial performance, thoracic fluid content and peripheral circulation. The method has gained popularity in recent years because it is not invasive. While less precise in absolute terms than invasive methods the results are reproducible, and the technique accurately assesses variations in measurements. It may be used in most anaesthetized patients without the possibility of any of the complications which sometime accompany the use of more precise invasive methods. This paper describes impedance cardiography and methods for its use.

Cardiography, Impedance↗
PubMed1980

Effects of minute volume increases on the rebreathing characteristics of the Bain anaesthesia circuit during controlled ventilation.

In the course of a study on the carbon dioxide rebreathing characteristics of the Bain anaesthesia circuit, it was noted that raising the minute volume without changing the fresh gas inflow invariably led to increased rebreathing of expired gases. Altering tidal volume and rate in order to reproduce a given minute volume had the same effect on rebreathing. A nomogram constructed to quantitate increases in rebreathing in function of carbon dioxide production per minute, fresh gas flow from the anaesthesia machine, and minute volume is produced. It can be used to assess the amount of fresh gas flow necessary to mantain a steady and inspired gas composition.

Anesthesiology↗
PubMed1980

Bronchofiberscopic jet ventilation.

The suction-biopsy channel of a flexible bronchofiberscope was used to provide subglottic jet ventilation in six dogs and eight adult human subjects. In dogs, after 75 minutes of ventilation at a driving pressure of 2580 torr/cm2 (50 lb/in2) the PaO2 was 412 +/- 18 torr and the PaCO2 32 +/- 3 torr with a peak airway pressure of 6 torr. In patients, after 30 minutes of jet ventilation, the PaO2 varied from 347 to 480 torr, the PaCO2 from 17 to 36 torr, and peak tracheal pressure from 6 to 8 torr. The method is convenient, simple and applicable in a variety of clinical situations.

Adult↗