Tongue oximetry in children with extensive thermal injury: comparison with peripheral oximetry.

We undertook a prospective study of standard peripheral pulse oximetry versus a modified pulse oximeter probe applied to the tongue in order to determine the efficacy of this alternative monitoring site in children with thermal injuries. Ten patients with a mean age (+/- SD) of 7.5 +/- 4.5 yr were studied on 15 occasions. The mean weight (+/- SD) was 31.4 +/- 13.7 kg and percent surface area burn (+/- SD) was 56 +/- 21%. A total of 1,992 min of anaesthesia time was monitored. Both sites functioned simultaneously 47% of the time; the lingual but not the peripheral site functioned 28% of the time and only the peripheral site and not the lingual functioned 22% of the time. Neither site functioned 3% of the time. The tongue oximeter provided 563 min more monitoring time than the peripheral sites. The tongue oximeter also functioned in children with peripheral vasoconstriction when the peripheral sensor failed and was less susceptible to electrocautery interference. The tongue oximeter is a reasonable adjunct but not a substitute for peripheral oximetry since its application is limited to paralyzed, intubated patients.

Continuous oxygen saturation monitoring following rectal methohexitone induction in paediatric patients.

Rectal methohexitone has been used to induce anaesthesia in paediatric patients for a number of years. This study was conducted in order to confirm the safety of this method of induction for uncomplicated routine paediatric patients. Children between the ages of six months and six years were considered candidates for induction with methohexitone (10%, 25-30 mg.kg-1). Patients were monitored with a continuous oxygen saturation recording. Forty-nine patients participated in this study and anaesthesia was induced successfully in 44. The mean age of the patients was 2.7 +/- 1.6 yr. The mean weight was 13.8 +/- 4.3 kg and the mean dose of methohexitone for successful induction was 27.0 +/- 3.0 mg.kg-1. Continuous oximeter recordings were available in 31 of the 42 patients who allowed oximeter placement prior to administration of methohexitone. No major desaturation events were noted in any patient. Two brief episodes of desaturation occurred. One with a nadir of 90% which lasted for 45 sec and another with a nadir of 86% which lasted for 26 sec. Both children had their heads flexed over their parents' shoulders at the time of the event resulting in partial airway obstruction. Both of these episodes were the result of upper airway obstruction which was clinically diagnosed by the anesthetist and readily corrected by repositioning the head. This study confirms the efficacy and safety of rectal methohexitone for induction of general anaesthesia in children. Mechanical obstruction of the airway following induction seems to be the most likely cause for oxygen desaturation. Monitoring of pulse oximetry does not appear necessary provided the child is carefully observed for adequacy of air exchange.

Ionized hypocalcemia after fresh frozen plasma administration to thermally injured children: effects of infusion rate, duration, and treatment with calcium chloride.

A number of cardiac arrests and severe hypotensive episodes have been witnessed associated with the intravenous infusion of fresh frozen plasma (FFP). To clarify the possible role of hypocalcemia, 28 thermally injured anesthetized pediatric patients with massive blood loss were studied to examine the cardiovascular responses (mean arterial pressure [MAP], heart rate, ECG) to 49 infusions of FFP. Rapid, statistically significant reductions in ionized calcium ([Ca2+]) followed each of four rates (1.0, 1.5, 2.0, and 2.5 ml.kg-1.min-1 for 5 minutes) of FFP infusion (P less than 0.0001). The slowest rate resulted in significantly less reduction in [Ca2+] than did the higher infusion rates (P less than 0.002). In five children MAP decreased greater than or equal to 20% below baseline levels, but this was not correlated with rate of FFP administration or decrease in [Ca2+]. The decreases in [Ca2+] and MAP were inversely related to age and unrelated to anesthetic technique. Changes in the Q-oTc interval were not related to [Ca2+]. Adverse cardiovascular responses and reduced [Ca2+] were not significantly different between 5- and 10-minute FFP infusions. Fewer fluctuations in MAP occurred when calcium chloride (CaCl2) was administered; the least fluctuation in [Ca2+] occurred when CaCl2 was administered during the plasma infusion. It is concluded that in thermally injured children 1-17 years old: 1) Rapid infusions of FFP produce sudden but evanescent decreases in [Ca2+]; more rapid infusions result in greater reductions in [Ca2+]. 2) There is no correlation between [Ca2+] and systemic hypotension. 3) Clinically important decreases in MAP occasionally accompany the rapid infusion of FFP.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium chloride versus calcium gluconate: comparison of ionization and cardiovascular effects in children and dogs.

A randomized prospective study in both children and dogs compared ionization of calcium chloride and calcium gluconate. Five conditioned dogs under halothane anesthesia received calcium chloride (4, 8, 12 mg/kg) and calcium gluconate (14, 28, 42 mg/kg) intravenously. Ten children scheduled for burn wound excision and grafting received both calcium chloride (2.5 mg/kg) and calcium gluconate (7.5 mg/kg) injected through a central venous cannula. Ionized calcium was measured at 0, 0.5, 1, 3, 5, and 10 min in the children, and 0, 0.5, 1, 2, 3, 4, 5, 10, 20, and 45 min in the dogs. The authors conclude that equal elemental calcium doses of calcium gluconate (10%) and calcium chloride (10%) (approximately 3:1), injected over the same period of time, are equivalent in their ability to raise [Ca++] during normocalcemic states in children and dogs; the changes in [Ca++] following calcium administration are short-lived (minutes); rapidity of ionization seems to exclude hepatic metabolism as an important factor in the dissociation of calcium gluconate; and equivalent rises in [Ca++] produced by calcium gluconate or calcium chloride resulted in equivalent cardiovascular effects. The authors feel that either form of calcium salt would be satisfactory if indicated during cardiopulmonary resuscitation or for the treatment of ionized hypocalcemia due to massive blood transfusion.

Intraoperative events diagnosed by expired carbon dioxide monitoring in children.

Expired carbon dioxide measurements (PeCO2) were used (1) to assess the adequacy of initial alveolar ventilation, and (2) to document intraoperative airway events and metabolic trends. Three hundred and thirty-one children were studied. Thirty-five intraoperative events were diagnosed by continuous PeCO2 monitoring; 20 were potentially life-threatening problems (malignant hyperthermia, circuit disconnection or leak, equipment failure, accidental extubation, endobronchial intubation, or kinked tube); only two of these were also diagnosed clinically. The duration of anaesthesia may be a factor: 3.9 hours for cases with events vs. 2.5 hours for cases without events (p less than 0.002). There was a higher incidence of hypercarbia (peak expired PeCO2 greater than or equal to 50) in children who were not intubated (29 per cent) compared to those who had an endotracheal tube in place (12 per cent) (p = 0.0001). Hypocarbia (peak expired PeCO2 less than or equal to 30) was more frequent in intubated cases (11 per cent) than in unintubated cases (three per cent) (p = 0.03). There was a high incidence of hypocarbia in infants less than one year of age (p = 0.02). We conclude: (1) life-threatening airway problems are common during anaesthesia in paediatric patients; (2) quantitative measurement of PeCO2 provides an early warning of potentially catastrophic anaesthetic mishaps; (3) the incidence of events increases with duration of anaesthesia.

Comparative renal effects of midazolam and thiopental in humans.

Midazolam is a water-soluble benzodiazepine whose quick onset after intravenous injection, short duration of action, absence of venous irritation, and mild cardiovascular and respiratory effects suggest its use for induction of anesthesia. The renal effects of midazolam-N2O-O2 anesthesia, as determined by renal clearance of injected inulin and para-aminohippuric acid (PAH), in hydrated ASA Class I-II surgical patients (N = 8) were compared in a double-blind fashion with a similar group of patients (N = 9) anesthetized with thiopental-N2O-O2. Except for glomerular filtration rate, there were no significant changes in any of the measured variables (blood pressure, effective renal plasma flow, renal blood flow, and renal vascular resistance). The per cent reduction in glomerular filtration rate in patients given thiopental differed significantly from that in patients given midazolam. This study suggests that midazolam, as opposed to thiopental, offers minimal advantage in maintaining renal performance at least during the period of anesthetic administration.

Cardiovascular effects of midazolam and thiopentone for induction of anaesthesia in ill surgical patients.

The cardiovascular effects of midazolam (0.15 mg kg-1) and thiopentone (3.0 mg kg-1) were compared during induction of anaesthesia in 20 American Society of Anesthesiologists class III patients. In patients given thiopentone (N = 11), cardiac output, mean arterial pressure, heart rate, and systemic vascular resistance all decreased significantly over the course of the study period; mean right atrial pressure rose slightly, and stroke volume remained the same. Patients receiving midazolam (N = 9) experienced similar haemodynamic changes which were significant relative to baseline only for the fall in mean arterial pressure and the rise in mean right atrial pressure at ten minutes. There were no significant differences between the two groups. Midazolam thus appears to be at least as acceptable an induction agent as thiopentone in ill patients, from a haemodynamic point of view.

Comparative cardiovascular effects of midazolam and thiopental in healthy patients.

Midazolam, a water-soluble benzodiazepine that is shorter-acting, more potent, and less irritating to veins than diazepam, has been suggested for use for induction of anesthesia. The cardiovascular effects of an induction-sized dose (0.25 mg/kg) of midazolam in A.S.A. class I or II surgical patients (N = 11) sedated with morphine and N2O-O2 were compared in a double-blind fashion with a similar group of patients (N = 9) receiving thiopental (4.0 mg/kg). Consistent with earlier studies, patients given thiopental experienced downward trends from base line in mean arterial pressure, stroke volume, cardiac output, and heart rate; mean right atrial pressure increased slightly, whereas systemic vascular resistance did not change. Induction of anesthesia with midazolam was associated with more gradual and less pronounced hemodynamic alteration; the only significant changes from base line were decreases in mean arterial pressure 5 and 10 minutes after injection. When the two groups were compared, no significant differences were found. Midazolam is, then, as acceptable for induction of anesthesia as thiopental from a hemodynamic point of view in A.S.A. class I and II patients.