Care of the airway.
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Anesthesia Recovery Period↗
Biomedical subjects
J Chalon
Publications and source records attributed to J Chalon.
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↗
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↗
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↗
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↗
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↗
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↗
Intrauterine exposure to halothane increases murine postnatal autotolerance to halothane and reduces brain weight.
The effect of halothane on prenatal development was assessed using the appearance of postnatal tolerance to the anesthetic and its effect on brain weight. Eighteen 3-month-old mice were repeatedly tested in a rotating cage for loss of righting reflex during exposure to increasing concentrations of halothane on 15 occasions to determine whether or not tolerance to halothane developed. Of these, nine mice were born to dams exposed for 30 min to 2% halothane on days 14 and 17 of gestation. The other nine mice (controls) were born to dams exposed to 100% oxygen for 30 min at the same stage of pregnancy. There was no significant difference in tolerance to halothane between the groups during the first nine days of repeated exposure to halothane. By the 13th and 15th days, however, mice exposed to halothane in utero became more tolerant to 1% halothane than did controls (P less than 0.025). In addition, the mean total brain weight of six 7-week-old mice exposed to 2% halothane in utero for 30 min on days 14 and 17 of gestation was found to be significantly less than the mean total brain weight of six control mice not exposed to halothane in utero (20.83 +/- 0.27 g and 23.07 +/- 0.51 g, respectively, P less than 0.0025). This difference occurred mainly in the brain stem rather than in the forebrain and cerebellum.
Animals↗
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↗
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↗
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↗
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↗
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↗
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↗
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↗
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↗
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↗
Growth and development of mice breathing 42% oxygen.
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Animals↗