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Biomedical subjects

S Ramanathan

Publications and source records attributed to S Ramanathan.

At least 91 records · Page 5Linked to original sources
PubMed1989

Plasma beta-endorphin levels in the umbilical cord blood of preterm human neonates.

Maternal venous (MV) and neonatal umbilical venous (UV) and umbilical arterial (UA) plasma beta-endorphin concentrations were measured at birth in two groups of patients undergoing cesarean section (CS). Patients in group 1 carried a term gestation (n = 12, birth weight 3,640 +/- 150 g, 1 SEM). Patients in group 2 (n = 12) carried a preterm gestation (birth weight 1,956 +/- 150 g). In the term neonate the UV and UA plasma beta-endorphin were 11.5 +/- 4 and 13.5 +/- 4 picomoles/liter, respectively. In the preterm neonate the UV and UA values were 23.6 +/- 4 and 23.5 +/- 5 picomoles/liter, respectively. Both values in the preterm neonate were significantly greater than the corresponding value in the term neonate (p less than 0.05). The MV plasma beta-endorphin did not significantly differ among the two groups. Data suggest that in preterm neonates increased plasma beta-endorphin levels occur at the time of birth.

Cesarean Section↗
PubMed1988

Skeletal contribution of cyclic adenosine monophosphate in response to parathyroid hormone and calcitonin in vivo in the rat.

Cyclic adenosine monophosphate (cAMP) is thought to be a second messenger for the actions of both parathyroid hormone (PTH) and calcitonin (CT). We examined the release of cAMP from rat bone in vivo after administration of synthetic rat PTH-(1-34) (rPTH), synthetic human PTH-(1-34) (hPTH), or synthetic human CT (hCT). Blood from the venous effluent of the femoral bone of rats (bone blood) was drawn at 5 and 10 minutes after the administration of hormones. The cAMP content of the bone blood was then compared to the cAMP content of arterial blood. In both kidney-clamped and non-kidney-clamped rats, hCT led to a significantly greater concentration of cAMP in the bone blood than in the arterial blood. We interpret this to be due to bone production and release of cAMP. Neither hPTH nor rPTH produced a significantly greater amount of cAMP in the bone blood than in arterial blood. These data do not preclude the possibility that there was a production of cAMP within the bone tissue itself after PTH but suggest that there was no release of cAMP from the bone into the bone blood.

Animals↗
PubMed1988

Vasopressor therapy for hypotension due to epidural anesthesia for cesarean section.

Maternal hemodynamic changes and neonatal acid-base status were assessed in 127 healthy patients undergoing elective cesarean section under epidural anesthesia. An impedance cardiograph was used to measure stroke volume (SV), ejection fraction (EF) and end-diastolic volume (EDV). In addition, neonatal umbilical venous and arterial PO2, PCO2, pH, base excess, lactate, pyruvate, excess lactate, and L/P ratio were measured at birth. Patients were divided into three groups. Group 1 (n = 53) required no vasopressor (normotensive controls). In Group 2 (n = 37), mean blood pressure (BP) decreased from 90 mmHg (13.3 kPa). In Group 3 (n = 37), BP decreased from 83 mmHg to 62 mmHg (11.1 to 8.2 kPa), and phenylephrine was administered in 100 micrograms increments to maintain systolic BP greater than 100 mmHg (13.3 kPa). In Groups 2 and 3 the SV and EDV decreased 43% and 33% respectively when hypotension developed. Both vasopressors restored BP, SV and EDV to near baseline values. Neonatal Apgar scores and acid-base profiles were not significantly different among the three groups of neonates, nor were they different between the two hypotensive groups. It is concluded that: 1) transient maternal hypotension does not affect neonatal acid-base status; 2) both ephedrine and phenylephrine increase cardiac preload; and 3) an alpha agent like phenylephrine does not cause fetal acidosis when used for treating maternal hypotension.

Adult↗
PubMed1986

Care of the airway.

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Anesthesia Recovery Period↗
PubMed1985

Arterial to end-tidal CO2 gradients during spontaneous breathing, intermittent positive-pressure ventilation and jet ventilation.

Arterial to end-tidal CO2 tension gradients were measured in 18 dogs during spontaneous breathing (SB), intermittent positive-pressure ventilation (IPPV), and both low-frequency and high-frequency jet ventilation (LFJV and HFJV). The dogs were anesthetized with nembutal and permitted to breathe spontaneously through an 8-mm internal diameter endotracheal tube; blood gas tensions, cardiac output, and end-tidal CO2 partial pressure (PetCO2) were measured. IPPV, LFJV, and HFJV were then instituted in a random sequence and measurements repeated. PaO2, PaCO2 and cardiac output were similar during all four ventilatory modes. The mean PaCO2 differed significantly (p less than .001) from PetCO2 during IPPV, LFJV, and HFJV but not during SB. The mean PaCO2-PetCO2 gradient was 3.7 +/- 1 (SD), 12.6 +/- 5.0, and 24.3 +/- 8 torr during IPPV, LFJV and HFJV, respectively. The large gradients during LFJV and HFJV were not produced by dilution of tracheal CO2 by entrained air or by oxygen delivered by the jet. These results suggest that both LFJV and HFJV may be associated with a large PaCO2-PetCO2 gradient.

Animals↗
PubMed1984

Humidification and airway pressures during high-frequency jet ventilation delivered through the suction-biopsy channel of a flexible bronchofiberscope.

The suction-biopsy channel (SBC) of a flexible bronchofiberscope was used to deliver gas into the trachea during high-frequency jet ventilation (HFJV) at a rate of 95 cycle/min and a tidal volume (VT) of 95 ml. A Portex epidural catheter inserted into the SBC was used to entrain water for humidification by the injector principle. Inspired humidity (IH) was regulated by adjusting the distance (D) between the injector and jet portals. Airway pressures, pulmonary gas exchange and IH levels were measured in 11 dogs. In addition, tracheal cytology scores (TCS, a sensitive index of tracheal epithelial damage caused by breathing dry gases) were assessed in 12 patients. The system maintained adequate pulmonary gas exchange in both dogs and humans. In dogs the mean tracheal pressure was 2.8 +/- 0.5 (SD) torr with a peak pressure of 3.8 +/- 0.5 torr. The upper-airway pressure was subatmospheric (-2 +/- 0.2 torr) during the first half of jet inspiration, but peaked synchronously with tracheal pressures during the second half. Both the upper airway and the trachea had a positive end-expiratory pressure (PEEP) of 1.8 +/- 0.2 torr. When D was 0.3 cm, the system delivered gas with an IH of 44 mg H2O/L (almost saturated at 37 degrees C). Human TCS did not change significantly after 2 h of humidified HFJV, suggesting efficient humidification.

Adult↗
PubMed1984

Exposure of sires to enflurane affects learning function of murine progeny.

Four 11-week-old white Swiss Webster male mice were exposed to 2% enflurane in oxygen for 4 hr/day on 5 alternate days. Eight days later each male was mated with 2 females. There was a 20% loss of offspring due to stillbirths. A total of 24 pups survived (group E). At the age of 7 weeks the learning function of group E mice was tested in a Rosensweig maze and compared to that of 24 pups born to sires similarly exposed to oxygen alone (group C). Pups from group E performed statistically significantly slower than group C pups. After animals had been tested for 10 alternate days, there was no further change in performance in either group over the next 10 weeks. Thus changes of the reproductive cells of male mice caused by exposure to enflurane adversely affect the learning function of their offspring.

Animals↗
PubMed1984

Concentrations of lactate and pyruvate in maternal and neonatal blood with different intravenous fluids used for prehydration before epidural anesthesia.

This study assesses the effects of infusion of 1200 ml of four different intravenous solutions before epidural anesthesia for cesarean section on maternal and neonatal whole blood lactate (L), pyruvate (P), excess lactate (XL), L/P ratio, and base excess (BE) in four equal groups of patients. Patients in group I (n = 15) received normal saline; those in group II, Ringer's lactate (RL); those in group III, RL with 20 g of glucose; and those in group IV, Plasma-Lyte A. Maternal venous concentrations of L increased significantly in all groups after infusion, but P increased only in group III. Both XL concentrations and L/P ratios remained unchanged after infusion in group III mothers, but increased in the other three groups. Umbilical venous (UV) and arterial (UA) blood L concentrations (1.85 +/- 0.13, 1 SEM mmol/L in both) were greater in group III than in groups I and II, and P concentrations (0.12 +/- 0.01 mmol/L in both) were significantly greater in group III than in groups I, II, and IV. Both UV XL (0.9 +/- 0.1 mmol/L) and L/P ratio (32 +/- 8) were significantly greater in group IV neonates than in the other groups. However, neither neonatal Apgar scores nor maternal and neonatal BE significantly differed among the four groups. No neonate developed hypoglycemia. It is concluded that all the four intravenous fluids, despite differences in their effects on blood L and P concentrations, produce clinically satisfactory maternal and neonatal outcome.

Adult↗
PubMed1984

Detection of anesthesia machine faults.

One hundred ninety people attending an anesthesia meeting were given ten minutes to identify five faults intentionally created in a standard anesthesia machine. 7.3% of participants found no machine faults and 3.4% found all five faults. The average number of identified faults was 2.2. Professional background did not influence the scores, but fault detection ability was increased in practitioners with ten years or more of experience. Concealed faults that did not make the machine inoperable were most frequently missed. Greater emphasis should be placed on aggressive system checking in education programs and in daily clinical practice.

Anesthesiology↗
PubMed1984

The pall ultipor breathing circuit filter--an efficient heat and moisture exchanger.

The Pall bacterial filter was tested as a potential heat and moisture exchanger on a model patient, placed on a circle absorber system, and clinically. The laboratory study was conducted during mechanical ventilation at a V of 6 L/min with fresh gas inflows of 1, 3 and 6 L/min. The model patient introduced carbon dioxide into the circuitry at a rate of 200 ml/min. The resistance of the filter was tested before and after each experiment. With all fresh gas inflows , absolute humidity increased from around 19 mg H2O/L at the start of experimentation to about 27 mg H2O/L within 30 min. Maximum humidities reached were 28 +/- 0.7 mg H2O/L, 27.6 +/- 0.5 mg H2O/L, and 27.7 +/- 0.5 mg H2O/L within 3 hr, with fresh gas inflows of 1, 3, and 6 L/min, respectively. Variations in inspired humidity were also assessed at minute volumes of 4 and 5 L/min with fresh gas inflows of 6 and 3 L/min. Increases in percent dead space were negligible when the filter was inserted between the model patients (assumed to weigh between 70-40 kg) and the circuit. There was no statistically significant increase in pressure with gas flows of 50 L/min when the instrument was dry (0.02 +/- 0.001 cm H2O/L X min-1) or when it was wet (0.02 +/- 0.002 cm H2O/L X min-1). The clinical study was conducted on ten adult anesthetized patients breathing through the bacterial filter and ten controls. The loss of body temperature was 0.2 degrees C when the filter was used and 1.5 degrees C when the filter was not used. Arterial blood gas tensions were within normal limits when the bacterial filter was used as a humidifier.

Adult↗
PubMed1983

Analgesic properties of meperidine, amitriptyline and phenelzine in mice.

Sixty-three white Swiss Webster mice were divided into seven equal groups. Their tolerance to pain (heat applied to the tail by a test tube containing hot water at a temperature measured by telethermometry) was assessed before and after intraperitoneal injection of (1) physiologic saline; (2) meperidine 14 micrograms X g-1; (3) amitriptyline 6 micrograms X g-1 (4) amitriptyline 12 micrograms X g-1; (5) phenelzine 1.5 micrograms X g-1; (6) phenelzine 3 micrograms X g-1; and (7) amitriptyline 6 micrograms X g-1 plus phenelzine 1.5 micrograms X g-1. All post-injection tests were conducted 45 and 90 minutes after administration, and repeated 24 hours later. No significant difference in pain threshold was noted in any pre-injection test or in any test conducted with physiologic saline. By 90 minutes post-injection, all groups receiving drugs developed increased tolerance to pain. Mice which had received phenelzine plus amitriptyline, or either dose of phenelzine were more tolerant to pain for up to 24 hours than mice which had received physiologic saline. The most marked increases in tolerance to pain were seen with 1.5 micrograms X g-1 and 3 micrograms X g-1 of phenelzine and phenelzine plus amitriptyline. However, phenelzine was more effective and had a longer-lasting effect than either dose of amitriptyline, or meperidine. The combination of phenelzine plus amitriptyline was no more effective than phenelzine alone.

Amitriptyline↗
PubMed1983

Murine auto- and cross-tolerance to volatile anaesthetics.

Auto-tolerance and cross-tolerance to halothane, isoflurane and enflurane were tested on 36 mice divided into three equal groups. Each group was first exposed to increasing concentrations of either of the three anesthetics on 13 occasions. The concentration at which each mouse lost its righting reflex during successive exposures in a rotating cage was noted. Cross-tolerance was assessed by comparing the number of mice which had lost their righting reflexes during their first exposure to a given anaesthetic agent to the number which lost it after having been exposed to another anaesthetic. All animals developed auto-tolerance to halothane, isoflurane and enflurane. Cross-tolerance was noted only between mice exposed to isoflurane and enflurane and between mice exposed to halothane and subsequently anaesthetized with isoflurane, but not vice versa.

Animals↗
PubMed1983

Anaesthetic uptake by the goldfish: effect of respiratory rate.

In order to assess the uptake of halothane by the goldfish, the respiratory rate of six fish was studied when water temperature was varied with and without changes in oxygen or carbon dioxide tension. The effective dose 50 of halothane (ED-50-H) and the time taken to reach it (T-ED-50-H) at an FIO2 of 0.35 in nitrogen, were studied when temperature and CO2 tension were varied. Nomograms were drawn to predict respiratory rate as a function of water CO2 tension, when CO2 was bubbled in air or in oxygen, and with changes in water temperature. At low temperatures (5 degrees C to 7.5 degrees C), respiratory rate remained below 10 per min, irrespective of CO2 partial pressure. At 28 degrees C, a CO2 partial pressure of 8 +/- 0.2 kPa produced a respiratory rate of 125 +/- 3/min in air, and in oxygen unexpectedly 140 +/- 3/min. Halothane ED-50 varied with temperature (0.8% at 10 degrees C and 1.6% at 23 degrees C). Time to reach ED-50-H decreased with increases in respiratory rate, but increased as water temperature was elevated.

Animals↗