Alfred L. Daniels

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-O2were 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 a trial 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.

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, 18 thermally injured anesthetized pediatric patients with massive blood loss were studiedto 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 < 0.0001). The slowest rate resulted in significantly less reduction in [Ca2+] than did the higher infusion rates (P < 0.002). In five children MAP decreased ⩾20% below baseline levels, but this was not correlated with rate of FFP administration or decrease in [Ca2+]. The decreases in [Ca2+1 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 leastfluctuation in [Ca−2] occurred when CaCl2 was administered during the plasma infusion. It is concluded that in thermally injuredchildren 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 decreasesin MAP occasionally accompany the rapid infusion of FFP. 4) The duration of FFP infusion does not seem to be a significant factor in causing decreases in [Ca2+] or in MAP. 5) Pretreatment with exogenous calciummay reduce the incidence of cardiovascular instability; smaller fluctuations in [Ca2 +] occur if exogenous calcium is administered duringthe FFP infusion. 6) Changes in Q-oTc are not predictive of acute changes in [Ca2+].

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 shortlived (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 < 0.002). There was a higher incidence of hypercarbia (peak expired PeCO2≥ 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≤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) lifethreatening 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.RésuméL’6tude du CO2 en fin dexpiration (PeCO2) a été utilisée afin d’évaluer (1) la fonction respiratoire initiate et (2) pour documenter les événemenls per-opératoires touchant les voies aériennes ainsi que les changements métaboliques. 331 enfants ont été étudiés. 35 événements per-opératoires ont été diagnostiqués par une surveillance constante de la PeCO2; 20 représentaient des problèmes mettant en danger la vie (hyperthermie maligne, disconnection de circuit, fuite, bris d’équipement, extubation accidentelle, intubation endobronchique, ou tube endotrachéal coudd); seulement deux de ces événements ont été aussi diagnostiqués cliniquement. La durée de l’anesthésie pouvait aussi être un facteur: les présentants les accidents ont duré en moyenne 3.9 heurs contre 2.5 heures pour les cas n’ayant pas présenté de problèmes (p < 0.002). Il y avait un incidence plus élevée d’hypercarbie (PECO2 ≥ 50,) chez les enfants qui n’étaient pas intubés (29 pour cent) a comparé à ceux dont le tube endotrachéal élail en place (12 pour cent) (p = 0.0001). L’hypocarbie (PeCO2 ≤ 30) était plus fréquente chez les patients intubés (11 pour cent) que chez ceux qui n’étaient pas intubés (trois pour cent) (p = 0.03). It y avait une incidence plus grande d’hypocarbie chez les enfants âgés de moins qu’un an (p = 0.02). On colclut: 1) les problemes de voies aeriennes pouvant mettre en danger la vie sont fréquents lors de I’anesthésie pédiatrique; 2) la mesure quantitative de la PeCO2 fournie un signal d’alarme précoce pour les accidents anesthésiques potentiellement catastrophiques; 3) l’incidence des accidents augmente avec le temps.

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.RésuméAfin d’évaluer la langue comme site de monitorage de la saturation artérielle en oxygène chez des enfants brûlés, un capteur standard d’oxymètre de pouls périphérique est comparé de façon prospective à un capteur adapté à la langue. Dix enfants âgés de 7,5 ± 4,5 ans participent à l’étude au cours de 15 interventions. Les enfants ont un poids moyen de 31,4 ± 13,7 kg et présentent des brûlures couvrant en moyenne 56 ± 26% de la surface corporelle. La durée totale de la période anesthésique étudiée est de 1992 minutes. Les deux sites de monitorage sont simultanément fonctionnels durant 47% du temps. Pendant une période couvrant 28% du temps étudié, le capteur au niveau de la langue permet une mesure de saturation artérielle alors que le capteur périphérique ne donne pas de signal. À l’inverse, durant 22% du temps, le capteur périphérique est fonctionnel alors que celui de la langue ne l’est pas. La période pendant laquelle les deux capteurs sont simultanément inefficaces représente 3% du temps total. Le capteur au niveau de la langue permet 563 minutes de monitorage de plus que le capteur périphérique. La mesure de la saturation artérielle au niveau de la langue est possible chez des enfants avec vasoconstriction périphérique alors qu ’elle ne l’est pas avec le monitorage périphérique. De plus, le monitorage au niveau de la langue est moins sensible aux interférences électriques. En conclusion, la langue représente une alternative raisonnable comme site de monitorage de l’oxymètre de pouls. Cependant, son utilisation se limite aux patients myorelaxés et ventilés mécaniquement.

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

The cardiovascular effects of midazolam (0.15 mg kg-) and thiopentone (3.0 mg kg1) were compared during induction of anaesthesia in 20 American Society of Anesthesiologists class HI 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 haemoaynamic point of view.RésuméOn a comparé les effets cardiovasculaires obtenus pendant I’administration de I’anesthésie avec le midazolam (0.15 mg kg-1) et le thiopentone (30 mg kg1) chez 20patients appartenant ä la Classe III (American Society of Anesthesiologists). Chez les patients recevant le thiopentone (N = 11), on a observé que le débit cardiaque, la fréquence cardiaque, la résistance vasculaire générale et la tension artérielle ont baissé sensiblement durant le cours de notre recherche. La pression moyenne de I’auriculaire cardiaque droite haussa faiblement tandis que le débit systolique resta le même. Les patients auxquels on administra le midazolam (N = 9) ont éprouvé des changements hémodynamiques significatifs par rapport à la valeur de base oi l’on observa settlement une baisse de la pression artérielle moyenne et une hausse à dix minutes de la pression moyenne de l’ auriculaire cardiaque droite. Il n’y a done pas áe différences significatives entre les deux groupes. Le midazolam apparaît être un agent d’induction aussi acceptable que le thiopentone chez les malades, au point de vue hémodynamique.

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.RésuméLe méthohexitone par voie rectale a été utilisé pour un grand nombre d’années afin d’induire l’anesthésie chez les patients pédiatriques. Cette étude fut entreprise afin de confirmer la sécurité de cette méthode d’induction pour des patients pédiatriques n’ayant aucune complication. Les enfants entre l’âge de six mois et six ans furent considérés comme candidats à l’induction avec le méthohexitone (10%, 25–30 mg · kg−1). Les patients furent surveillés avec un enregistrement continu de la saturation en oxygène. Quarante-neuf patients ont participé à cette étude et l’anesthésie fut induite avec succès chez 44. L’âge moyen des patients était de 2,7 ±1,6 ans. Le poids moyen était de 13,8 ±4,3 kg et la dose moyenne de méthohexitone pour l’induction était de 27,0 ±3,0 mg · kg−1. Les enregistrements continus de l’oxymètre furent disponibles chez 31 des 42 patients chez qui on pouvait installer l’oxymètre avant l’administration de méthohexitone. Aucune saturation majeure ne fut notée chez aucun des patients. Deux épisodes brèves de désaturation sont survenues. Un avec un nadir de 90% qui a duré 45 secondes et un autre avec un nadir de 86% qui a duré 26 sec. Les deux enfants avaient leur tête fléchie sur l’épaule des parents au moment où l’évènement est survenu à cause d’obstruction partielle des voies aériennes. Ces deux épisodes furent cliniquement diagnostiqués par l’anesthésiologiste et corrigés par le repositionnement de la tête. Cette étude confirme l’efficacité et la sécurité de l’administration rectale de methohexitone pour l’induction de l’anesthésie générale chez les enfants. L’obstruction mécanique des voies aériennes après l’induction apparaît comme la cause la plus probable de la désaturation en oxygène. La surveillance de la saturométrie de pouls n’apparaît pas nécessaire si l’enfant est surveillé attentivement concernant l’échange gazeux adéquat.

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-N20–02 anesthesia, as determined by renal clearance of injected inulin and para-aminohippuric acid (PAH), in hydrated ASA Class III surgical patients (N = 8) were compared in a double-blind fashion with a similar group of patients (N = 9) anesthetized with thiopental-N20–02. 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