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Biomedical subjects

J Lerman

Publications and source records attributed to J Lerman.

At least 109 records · Page 6Linked to original sources
PubMed1989

Expiratory muscle activity in anesthetized children: effect on the single breath technique.

Phasic expiratory activity of the abdominal muscles occurs in adults during halothane anesthesia, but has not been demonstrated in children. If present, abdominal muscle activity would preclude the use of recently developed tests of respiratory mechanics in children during anesthesia. We therefore measured abdominal muscle activity throughout induction of anesthesia with halothane in 10 patients between 1.5 and 9.5 years of age, seven with normal respiratory function and three with chronic airway obstruction. During induction of anesthesia with halothane in N2O and oxygen, the abdominal wall electromyograph (a-EMG) was continuously recorded from surface electrodes. At the same time, the expiratory time constant (tau a) was measured using the single breath test (SBT). The patients were then paralyzed with succinyl choline, and the a-EMG signal and expiratory time constant during paralysis (tau p) were recorded. The raw a-EMG signal and its moving time average were compared with the phase of respiration and with the end-tidal fraction of halothane (Fehalo), and the effect of abdominal muscle activity on tau a was noted. Of the 10 patients, 2 had no abdominal muscle activity at any time during induction. Of the remaining 8 patients, 3 had continuous abdominal muscle activity throughout induction, including one patient with asthma. In the remaining five patients, abdominal muscle activity was present during light halothane anesthesia and disappeared at increased Fehalo. When abdominal muscle activity was present, tau a was significantly less than tau p. It is concluded that abdominal muscle activity in expiration is undetectable during deep halothane anesthesia in most children.(ABSTRACT TRUNCATED AT 250 WORDS)

Abdominal Muscles↗
PubMed1989

Cardiopulmonary effects of the volume recruitment manoeuvre in infant swine.

The volume recruitment manoeuvre is a non-invasive technique used to measure respiratory mechanics in infants. Because airway pressure increases during this manoeuvre, lung volume, compliance and cardiac output may change. In order to assess possible changes in cardiopulmonary function caused by the volume recruitment manoeuvre, we applied this technique to seven intubated infant swine breathing spontaneously during anaesthesia with halothane and N2O. Tidal volume (VT), respiratory frequency, arterial blood gases, cardiac output (CO) and total respiratory compliance were measured before and after the manoeuvre. In three swine functional residual capacity (FRC) was measured by helium dilution before the manoeuvre, and in four swine diaphragmatic EMG was recorded continuously. Finally, all swine were paralysed during volume recruitment to assess the contribution of the respiratory muscles to post-manoeuvre respiratory mechanics. VT and f increased immediately after the manoeuvre but there were no significant changes in PaCO2, or alveolar to arterial oxygen gradient. There was a small but statistically significant decrease in CO. Compliance increased by 17.8 +/- 3.6 per cent and FRC increased by a mean of 41.1 ml (or 51.9 per cent increase above the baseline FRC). The increase in FRC could not be explained by active mechanisms since the diaphragmatic EMG showed no post-inspiratory activity and neuromuscular paralysis did not decrease FRC. We conclude that the volume recruitment manoeuvre increases FRC and compliance by recruiting collapsed alveoli, and this effect must be taken into consideration when applying this test to infants.

Anesthesia, Inhalation↗
PubMed1989

Factors influencing the R-R interval during central venous injection in newborn swine.

Seven Yorkshire swine, ages 7-11 days and weighing 1.4-2.8 kg were studied to determine the effects of temperature and volume of injectate, depth of anaesthesia, position of the central venous catheter tip and vagotomy on the R-R interval after central venous injection of saline. The swine were anaesthetized with halothane in 100 per cent oxygen and their lungs ventilated to normocapnia. The length of the R-R varied inversely with the temperature of the injectate between 0 and 20 degrees C reaching a maximum prolongation of 152 per cent above control values with 0 degrees C saline. Injecting saline at 37 degrees C did not affect the R-R interval. The length of the R-R interval varied directly with the volume of injectate between 1.5 and 4.5 ml.kg-1 (P less than 0.05). The R-R interval response also varied directly with the depth of anaesthesia: the post-injection R-R interval increased from 185 per cent to 341 per cent as the end-tidal halothane concentration increased from 0.45 to 1.20 per cent. The position of the tip of the central venous catheter that produced the maximum increase in the R-R interval, as determined radiographically, was at the junction of the superior vena cava and the right atrium. Neither bilateral vagotomy nor atropine (50 micrograms.kg-1) affected the R-R interval after injecting 3 ml.kg-1 saline 0 degrees C. We conclude that the increases in R-R interval after injection of fluid into the right atrium are due to direct effects on the nerve conduction system of the heart, possibly on the sino-atrial node.

Anesthesia, Inhalation↗
PubMed1989

Single breath end-tidal CO2 estimates of arterial PCO2 in infants and children.

To determine whether single breath end-tidal carbon dioxide (PE'CO2) measurements accurately estimate arterial PCO2 (PaCO2) in infants and children, 68 healthy infants and children, ASA physical status I or II scheduled for peripheral and lower abdominal surgery requiring endotracheal intubation were studied. A 3 ml single breath sample was obtained with a 23-gauge needle which was inserted through the wall of the endotracheal tube below the connector. The mean +/- SD PE'CO2 33.6 +/- 6.9 mmHg did not differ significantly from the corresponding mean +/- SD PaCO2 33.6 +/- 5.6 mmHg. The coefficient of determination, r2, was 0.97. The authors conclude that single breath PE'CO2 measurements from the proximal end of the endotracheal tube accurately estimate the PaCO2 in infants and children.

Adolescent↗
PubMed1989

Effects of age on the serum concentration of alpha 1-acid glycoprotein and the binding of lidocaine in pediatric patients.

We determined the effect of age on the serum concentration of alpha 1-acid glycoprotein (alpha 1-AGP) in venous blood from 134 subjects who ranged in age from preterm neonates to 18-year-old adolescents. The mean (+/- SD) serum concentration of alpha 1-AGP, determined by radial immunodiffusion, increased significantly with age: the concentration found in neonates was less than that found in infants which, in turn, was less than that found in older children (p less than 0.001). In addition, we determined the effect of alpha 1-AGP on the free fraction of lidocaine in four groups of infants and children who received intravenous lidocaine (1.5 mg/kg). The percentage of free lidocaine correlated inversely and linearly with the serum alpha 1-AGP concentration (r2 = 0.617; p less than 0.001). The percentage of free lidocaine in the five neonates exceeded that in the older age groups. We conclude that the serum concentration of alpha 1-AGP increases while the free fraction of lidocaine decreases from early infancy to adolescence.

Adolescent↗
PubMed1989

Incidence of emesis and postanesthetic recovery after strabismus surgery in children: a comparison of droperidol and lidocaine.

The authors sought to compare the antiemetic and sedative postanesthetic effects of droperidol versus lidocaine given intravenously. One hundred and fifty children, ASA physical status I or II, ages 2-15 yr, were studied. Each child was randomly assigned to receive either droperidol, 0.075 mg/kg; lidocaine, 1.5 mg/kg; or a combination of lidocaine, 1.5 mg/kg, and a reduced dose of droperidol, 0.025 mg/kg, immediately after induction of anesthesia, which was with thiopental, atropine, and succinylcholine. Anesthesia was maintained with halothane and nitrous oxide. The incidence of postanesthetic vomiting was 22% in the droperidol-alone group, which was significantly less than the lidocaine-alone group (50%). The incidence of vomiting in the combination group (30%) was not significantly different from either the droperidol- or lidocaine-alone groups. The time in the recovery room was significantly shorter for patients given lidocaine alone than those given droperidol alone or the combination. However, the mean time intervals from completion of surgery to recovery of full alertness and to discharge from the hospital did not differ significantly among the three groups. In summary, the authors found that intravenous droperidol is significantly more effective than lidocaine in reducing the incidence of vomiting in unpremedicated children after strabismus surgery. Furthermore, droperidol did not delay either the time to recovery of full alertness or the time to discharge from hospital compared to lidocaine.

Adolescent↗
PubMed1989

Pharmacokinetics of intravenous dantrolene in children.

To determine the pharmacokinetics of iv dantrolene and its metabolites in children, ten children 2-7 yr of age scheduled for minor elective surgery, were studied. After induction of anesthesia and tracheal intubation, dantrolene (2.4 mg/kg) was administered iv over 10.2 +/- 0.83 min. Venous blood samples (3 ml) were obtained 1, 5, 10, 20, and 30 min and 1, 2, 4, 8, 12, and 20 h after the dantrolene infusion. Whole blood concentrations of dantrolene, 5-hydroxydantrolene, and nitroreduced acetylated dantrolene were measured by high-performance liquid chromatography. The whole blood concentration of dantrolene decreased rapidly from a mean (+/- SD) of 6.03 +/- 0.93 microgram/ml 1 min after the end of the dantrolene infusion to 3.56 +/- 0.49 microgram/ml at 1 h. Between 1 and 4 h, the concentration of dantrolene either remained constant or increased slightly. Thereafter, the concentration of dantrolene decreased slowly with an elimination half-life (mean +/- SD) of 10.0 +/- 2.6 h. The mean (+/- SD) time for the concentration of dantrolene to decrease to 3.0 micrograms/ml was 6.55 +/- 2.88 h. The whole blood concentration of 5-hydroxydantrolene reached a maximum of 0.60 +/- 0.18 microgram/ml approximately 7 h after the dantrolene and decreased thereafter with an elimination half-life of 9.0 +/- 2.5 h. The concentration of nitroreduced acetylated dantrolene was below the limit for detection at all times. All children recovered without complications. Intravenous dantrolene, 2.4 mg/kg, produces safe and predictable blood concentrations in children similar to those reported in adults.

Child↗
PubMed1988

Arterial oxygen saturation following premedication in children with cyanotic congenital heart disease.

To determine the effects of premedication on arterial oxygen saturation (SaO2) and heart rate (HR), 11 children (ages three to seven years) scheduled for elective repair of cyanotic congenital heart defects were studied. Patients were premedicated with oral or rectal pentobarbitone 2 mg.kg-1 90 minutes prior to induction of anaesthesia followed by intramuscular morphine 0.2 mg.kg-1 and atropine 0.02 mg.kg-1 60 minutes prior to induction. The SaO2 and HR of each child were monitored continuously using a Nellcor pulse oximeter during two 90 minute periods: a control period commencing 25.5 hours preoperatively (day 1) and a post premedication period commencing 1.5 hours preoperatively (day 2). Data were compared at time 0 (corresponding to the time of administration of pentobarbitone on day 2), 30 (corresponding to the administration of intramuscular morphine and atropine on day 2), 60 and 90 minutes (the latter corresponding to the time of induction on day 2) after the administration of pentobarbitone. There were no significant differences in SaO2 or HR between day 1 and day 2 at time 0, 60, and 90 minutes. The SaO2 (mean +/- SD) decreased significantly immediately following intramuscular premedication at time 30 minutes on day 2 (72.7 +/- 5.9 per cent) compared to the corresponding time on day 1 (83.9 +/- 2.9 per cent) (p less than 0.05). The duration of this desaturation was 2.5 +/- 1.9 minutes. Heart rate (mean +/- SD) increased from 109.2 +/- 21.3 beats.min-1 at time 30 minutes on day 1 to 142 +/- 20.4 beats.min-1 on day 2 (p less than 0.05). We conclude that administration of intramuscular premedication preceded by oral or rectal pentobarbitone causes transient arterial desaturation and tachycardia in children with cyanotic congenital heart disease.

Child↗
PubMed1988

Fresh gas formulae do not accurately predict end-tidal PCO2 in paediatric patients.

To determine the fresh gas flow (FGF) requirements in paediatric patients, we measured the FGFs needed to maintain distal end-tidal PCO2 (PETCO2) values at 30 and 38 mmHg in patients weighing between 3.8 and 20 kg ventilated with either a Sechrist Infant Ventilator IV-100B or an Air-Shields Ventimeter and a Mapleson D circuit. The FGF requirement was 500 ml.kg-1.min-1 to maintain a PETCO2 of 30 mmHg and 250 ml.kg-1.min-1 to maintain a PETCO2 of 38 mmHg when minute ventilation greater than or equal to FGF. When these formulae were used in a subsequent group of similar patients, a wide variation in PETCO2 measurements were obtained. We conclude that the safest and most accurate approach to determine the FGF requirement of paediatric patients is to continuously monitor the PETCO2 in each patient and to adjust the FGF accordingly.

Anesthesia, General↗
PubMed1987

Effects of anaesthesia and surgery on the solubility of volatile anaesthetics in blood.

To determine the effects of anaesthesia and surgery on the solubility of volatile anaesthetics in blood, we measured the blood/gas partition coefficients of enflurane, halothane, isoflurane, and methoxyflurane in vitro in blood obtained from six healthy unpremedicated adults at three different times during isoflurane anaesthesia: awake; 20 minutes after induction of anaesthesia, but before surgical incision; and, 90 minutes after surgical incision. The blood/gas partition coefficients of the four volatile anaesthetics decreased significantly after induction of anaesthesia and after surgical incision (p less than 0.05). Values for haematocrit and the serum concentrations of albumin, globulin, and cholesterol decreased parallel to the decrease in blood/gas partition coefficients.

Adult↗
PubMed1987

The effect of pancuronium on the solubility of aqueous thiopentone.

In this study we identified the precipitate formed when pancuronium bromide (pH 3.9) and sodium thiopentone (pH 10.6) are combined in vitro. A precipitate formed when sufficient pancuronium was added to thiopentone to decrease the pH below 9.25. The precipitate was isolated, redissolved in alkaline solution and identified as thiopentone using ultraviolet spectrophotometry. Pancuronium was soluble in water in the pH range of 2.0 to 12.0, whereas thiopentone was soluble in water only at a pH greater than 9.90. We conclude that thiopentone precipitates when combined with pancuronium because of a pH-dependent decrease in the solubility of thiopentone, rather than a chemical interaction.

Anesthesia↗