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Biomedical subjects

J M Badgwell

Publications and source records attributed to J M Badgwell.

17 recordsLinked to original sources
PubMed1992

Severe hypoxia enhances central nervous system and cardiovascular toxicity of bupivacaine in lightly anesthetized pigs.

Toxic systemic reactions to bupivacaine usually involve a number of factors, including hypoxia and acidosis. The objective of this study was to test the hypothesis that cardiovascular and central nervous system responses to bupivacaine overdose are proportional to the severity of hypoxia. The central nervous system and cardiovascular toxicity of bupivacaine was examined in three groups of pigs breathing 30%, 15%, or 10% O2, 70% N2O, and He (FIO2 = 0.15 and 0.1 groups). The 18 2-week-old pigs (6 animals per treatment) were paralyzed with pancuronium and their lungs ventilated mechanically. During the intravenous infusion of bupivacaine 2 mg.kg-1.min-1, four readily identified toxic endpoints (seizures, arrhythmias, isoelectric electroencephalogram, asystole) were observed in all animals, with the exception that 1 pig in the FIO2 = 0.3 group and 1 in the FIO2 = 0.15 group had no arrhythmias. Bupivacaine doses producing seizures, isoelectric EEG, and asystole were significantly less in the FIO2 = 0.1 groups as compared to the other groups. Arrhythmias occurred before seizures in all animals in the FIO2 = 0.1 group but in only 1 of 5 and 2 of 5 animals in the FIO2 = 0.15 and 0.3 groups, respectively. There was no significant difference between the arrhythmic dose of bupivacaine in the FIO2 = 0.3 versus 0.1 animals (8.4 +/- 2.4 vs. 4.0 +/- 1.4 mg.kg-1), but the dose was significantly less in the FIO2 = 0.1 animals than in the FIO2 = 0.15 animals (12.5 +/- 5.6 mg.kg-1). Arterial pH was stable in all three groups during bupivacaine infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Inhalation↗
PubMed1992

Respiratory gas monitoring in the pediatric patient.

Parents of soon-to-be-anesthetized children frequently express concern about their child's safety because they have heard that "anesthesia is the most dangerous part of the operation." Although I don't believe that statement was ever true, it is even less true today. With the development of reliable capnography and volatile agent measurement in infants and children, we have significantly reduced the risks associated with anesthesia. I think we can, and should, confidently reassure parents that the "anesthesia part of the operation" has been made much safer and that the child's breathing (as well as heart beat, temperature, oxygenation, etc.) will be vigilantly monitored by the anesthesiologist using both human senses and the latest in monitoring equipment.

Carbon Dioxide↗
PubMed1991

End-tidal carbon dioxide pressure in neonates and infants measured by aspiration and flow-through capnography.

In 25 anesthetized, intubated, artificially ventilated, and paralyzed healthy neonates and infants, end-tidal PCO2 (PETCO2) measured by remote multiplexed mass spectrometry was 1.86 +/- 1.58 mm Hg lower than arterial PCO2 (PaCO2). PETCO2 measured by a flow-through cuvette was 1.02 +/- 1.64 mm Hg lower than PaCO2. The difference between the two methods of capnography was not significant. Values for PETCO2 obtained by mass spectrometry changed -0.43 +/- 1.43 mm Hg from baseline after 15 minutes of aspiration at a sample flow rate of 240 ml/min. Values for PETCO2 obtained with flow-through capnography changed -0.17 +/- 2.17 mm Hg from baseline after 15 minutes. In both methods, the changes from baseline in PETCO2 over time were not significant. These results suggest that both methods of capnography studied are reliable and may be used safely in neonates despite high sample flow rates and added apparatus dead space (0.6 ml for tracheal tubes less than or equal to 4.0 mm OD and 4.9 ml for tracheal tubes greater than 4.0 mm OD).

Carbon Dioxide↗
PubMed1990

Accuracy of end-tidal PCO2 measurements using a sidestream capnometer in infants and children ventilated with the Sechrist infant ventilator.

To determine the accuracy of end-tidal PCO2 (PETCO2) measurements analyzed with a sidestream capnometer in infants and children whose lungs were ventilated with a Sechrist infant ventilator and an Ayre's t-piece, we compared PETCO2 measurements obtained from the proximal (PETCO2-p) and distal (PETCO2-d) ends of the tracheal tube to arterial PCO2 (PaCO2) in 37 healthy infants and children between 1.3 and 24.5 kg. Both PETCO2-p and PETCO2-d accurately approximated PaCO2, however, the mean (+/- SD) arterial to end-tidal PCO2 difference (delta(a-ET)PCO2) was significantly greater with proximal (1.27 +/- 1.54 mmHg) than with distal sampling (0.64 +/- 1.64 mmHg) (P less than 0.01). In the subgroup of patients who weighted less than 12 kg, the delta(a-ET)PCO2 using proximal gas sampling (1.94 +/- 1.29 mmHg) was also significantly greater than it was using distal sampling (0.74 +/- 1.31 mmHg) (P less than 0.001). We conclude that although statistically different, both proximal and distal estimates of PETCO2 provide acceptable estimates of PaCO2 in healthy infants and children who are ventilated with a Sechrist infant ventilator and an Ayre's t-piece system.

Carbon Dioxide↗
PubMed1990

Bupivacaine toxicity in young pigs is age-dependent and is affected by volatile anesthetics.

The influence of age and volatile anesthetic agents on plasma concentrations and toxic effects of bupivacaine were studied in 2-day-old, 2-week-old, and 2-month-old pigs. Bupivacaine was infused at a constant rate while the pigs' ECGs and EEGs were recorded. Six pigs in each age group were lightly anesthetized with 70% N2O/30% O2 during the bupivacaine infusion, and twelve 2-day-old pigs were anesthetized with 70% N2O/30% O2 plus either 0.5 X MAC halothane or isoflurane. Two-day-old pigs were more resistant than older pigs to the toxic effects of bupivacaine despite higher plasma concentrations at all sample times. All pigs given N2O alone or N2O plus halothane had ventricular dysrhythmias, but only one pig in the N2O plus isoflurane group had a ventricular dysrhythmia. Threshold doses of bupivacaine for dysrhythmias in the N2O alone and N2O plus halothane groups did not differ. Seizures occurred in all pigs in the N2O alone group, in none of the N2O plus halothane group, and in two of the N2O plus isoflurane group. The doses required to depress cardiac index and cause asystole were less in the groups receiving halothane and isoflurane. It was concluded that N2O plus halothane and N2O plus isoflurane increase the lethality of bupivacaine while preventing early warning signs of toxicity.

Aging↗
PubMed1990

Alveolar dead space does not affect indirect Fick cardiac output determinations.

We examined the influence of three variables (different breathing circuits, breath selected for analysis, and alveolar dead space ventilation) on the accuracy of noninvasive cardiac output determinations with the Fick CO2 (indirect) equation. We compared noninvasive determinations with invasive thermodilution measurements over a wide range of cardiac outputs in 17 2-mo-old pigs anesthetized with halothane and nitrous oxide and paralyzed with either pancuronium or d-tubocurare. We found that rebreathing and nonrebreathing circuits provide accurate cardiac output determinations and that the optimal breath for analysis with either the rebreathing or nonrebreathing technique appears to depend on the cardiac output. When alveolar dead space was increased by using positional changes and the intracardiac administration of glass beads, there was still a good correlation between noninvasive and invasive cardiac output determinations. We conclude that both rebreathing and nonrebreathing techniques of indirect Fick cardiac output determinations correlate well with thermodilution measures over a wide range of cardiac outputs and alveolar dead space/tidal volume fractions.

Animals↗
PubMed1990

Thiopental attenuates dysrhythmias in children: comparison of induction regimens.

Anesthesia was induced in 91 children using one of three induction regimens: (a) thiopental, atropine, and succinylcholine (T group); (b) halothane, atropine, and succinylcholine (H group); and (c) halothane, thiopental, atropine, and succinylcholine (H/T group). The incidence of dysrhythmias was significantly greater in the H group (85%) than in the T group (6%) and H/T group (20%). Fewer dysrhythmias occurred in the H/T group compared to the H group despite similarly prolonged QTc intervals in both groups. We conclude that induction of anesthesia with thiopental is appropriate and reduces the incidence of cardiac rhythm disturbances in children and that administration of thiopental to children during induction of anesthesia with halothane, atropine, and succinylcholine may reduce the incidence of cardiac dysrhythmias.

Anesthesia, General↗
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↗
PubMed1988

The cardiovascular effects of anticholinergic agents administered during halothane anaesthesia in children.

The cardiovascular effects of anticholinergic agents administered during halothane anaesthesia were studied in 31 children aged 1-12 years undergoing peripheral orthopaedic surgery. Either normal saline, glycopyrrolate (10 micrograms.kg-1) or atropine (20 micrograms.kg-1) was administered in randomized double-blind fashion during the induction of anaesthesia with halothane while the electrocardiogram was continuously recorded. After induction, the children were paralyzed with atracurium, intubated, and ventilated. Anaesthesia was maintained with N2O/O2 and halothane (up to 2.5% inspired). The concentrations of expired CO2 and halothane were measured continuously using mass spectrometry. Sixty-one percent (19/31) of the children developed one or more dysrhythmias. Junctional rhythm occurred in 74% (14/19) of the children with dysrhythmias, developed early during induction (mean +/- s.d. time = 2.29 +/- 2.0 min after commencement of induction), and usually resolved before the administration of the study drug (8/14). All dysrhythmias initially occurred before or during induction and none developed during intubation, during incision, during the maintenance of anaesthesia, or after the administration of anticholinergic agents. The data suggest that: 1) a combination of factors present during halothane induction is highly dysrhythmogenic especially for junctional rhythm; 2) junctional rhythm will resolve spontaneously; 3) the administration of an anticholinergic agent during halothane induction is safe but may be unnecessary in children greater than 1 year of age; and 4) the dysrhythmogenic factors present during induction are attenuated during the maintenance of halothane anaesthesia.

Anesthesia, Inhalation↗
PubMed1987

End-tidal PCO2 measurements sampled at the distal and proximal ends of the endotracheal tube in infants and children.

To determine whether the site of gas sampling affects end-tidal gas measurements in pediatric patients, end-tidal PCO2 was measured continuously from the distal and proximal ends of the endotracheal tube in 60 infants and children ventilated with an Air-Shields Ventimeter and a partial rebreathing circuit. These data were compared with simultaneous arterial PCO2 measurements. In infants and children weighing greater than or equal to 12 kg, both distal and proximal end-tidal PCO2 values approximated arterial PCO2 measurements. In infants and children weighing less than 12 kg, however, only distal end-tidal PCO2 measurements approximated arterial PCO2 measurements. It is concluded that in infants and children weighing less than 12 kg, accurate end-tidal measurements can be obtained only from the distal end of the endotracheal tube.

Body Weight↗
PubMedDate not supplied

A rodent model for studying four well defined toxic endpoints during bupivacaine infusion.

An animal model with four well defined endpoints for studying the cardiotoxicity and neurotoxicity of bupivacaine is described. Five male Wistar rats (264-324 g) were anesthetized, tracheostomized and ventilated, and ECG and EEG leads were placed. Femoral arteries and veins were then cannulated. Twenty minutes before bupivacaine infusion, 0.1 mg/kg pancuronium was given intravenously, and anesthesia was adjusted to halothane 0.5%, 30% O2 and 70% N2O. Bupivacaine infusion was then begun at 2 mg/kg/minute. Bupivacaine doses producing the following endpoints were then determined: (1) first ventricular arrhythmia (ARR), (2) seizures (SZ), (3) isoelectric EEG (ISO EEG), and (4) asystole (ASYS). The doses of bupivacaine (in mg/kg +/- SD) precipitating AAR, SZ, ISO EEG and ASYS were 4.22 +/- 1.87, 7.08 +/- 1.55, 11.05 +/- 5.15 and 20.4 +/- 6.49 mg/kg, respectively. These endpoints were present and readily determined in all animals. The doses of bupivacaine producing ARR and SZ were not significantly different (p greater than 0.05). The doses producing SZ, ISO EEG and ASYS were significantly different from each other (p greater than 0.05, ANOVA and the Duncan test). These results indicate that it is possible to study, in the anesthetized and paralyzed rat that is intensely monitored, many of the variables associated with local anesthetic toxicity currently of clinical interest. The use of a constant local anesthetic infusion allows ready observation of the progression of toxic signs.

Animals↗
PubMedDate not supplied

Cardiovascular and central nervous system effects of co-administered lidocaine and bupivacaine in piglets.

The toxic profile of bupivacaine (1 mg/kg/minute) when administered intravenously alone or with lidocaine (1 mg/kg loading dose, then 1 mg/kg/minute) was examined in 12 2-day-old pigs anesthetized with 70% N2O/30% O2 and paralyzed with 0.15 mg/kg pancuronium. Bupivacaine doses producing arrhythmias, seizures, isoelectric EEG and asystole were about 24% lower in the lidocaine plus bupivacaine group (n = 6) than in the bupivacaine group (n = 6). However, the incidence of cardiac arrhythmias in the combination local anesthetic group (3/6) was half that in the bupivacaine group (6/6). Administration of lidocaine with bupivacaine under conditions of this study apparently reduces the risk of cardiac arrhythmias and acts along with bupivacaine to produce seizures, cerebral depression (isoelectric EEG) and asystole.

Animals↗