Endotracheal drug therapy

Cardiopulmonary resuscitation and pediatric advanced life support update for the emergency physician

Although pediatric cardiopulmonary arrest is uncommon, out-of-hospital survival is dismal. Through international consensus conferences, the American Heart Association develops new treatment recommendations for cardiopulmonary resuscitation every few years. The recent changes in cardiopulmonary resuscitation and pediatric advanced life support, with some background information about these changes, will be reviewed.

Reanimación cardiopulmonar avanzada en pediatría

Advanced life support (ALS) includes all the procedures and maneuvers used to restore spontaneous circulation and breathing, thus minimizing brain injury. The fundamental steps of ALS are airway control with adjuncts, ventilation with 100% oxygen, vascular access and fluid and drug administration, and monitoring to diagnose and treat arrhythmias. Airway control can be achieved by means of oropharyngeal airway, endotracheal intubation, and alternative methods (laryngeal mask and cricothyroidotomy). Vascular access can be achieved by the peripheral venous, intraosseous, central venous, and tracheal routes. The most frequent rhythms found in children with cardiorespiratory arrest are nonshockable (asystole, severe bradycardia, pulseless electrical activity, and complete atrioventricular block). In these cases, adrenaline continues to be the essential drug. Currently, low adrenaline doses (0.01 mg/kg IV and 0.1 mg/kg intratracheal administration) are recommended throughout the resuscitation period. Amiodarone (5 mg/kg) is the drug of choice in cases of ventricular fibrillation refractory to electric shock. The treatment sequence for shockable rhythms (ventricular fibrillation and pulseless ventricular tachycardia) is one 4 J/kg electric shock, followed by cardiopulmonary resuscitation (chest compressions and ventilation) for 2 minutes with subsequent reassessment of the electrocardiographic rhythm. Adrenaline must be administered immediately before the third electric shock and subsequently every 3-5 minutes. Amiodarone must be administered immediately before the fourth shock.

Plasma epinephrine levels after epinephrine administration using different tracheal administration techniques in an adult CPR porcine model

The aim of the study was to compare arterial plasma epinephrine levels after tracheal epinephrine application using three different tracheal instillation techniques at different tracheal levels in a porcine adult cardiopulmonary resuscitation model. In the prospective, randomized study, electrically-induced cardiopulmonary arrest was applied to 32 anaesthetized and paralyzed domestic pigs. After 3 min of cardiopulmonary arrest and 2 min of external chest compressions using a pneumatic compression device and mechanical ventilation, epinephrine was administered intravenously (20 microg/kg) or tracheally (50 microg/kg): using either direct injection into the upper end of the tracheal tube, via a catheter placed into the bronchial system and using a special tracheal application tube. In each group, there were eight pigs. Arterial blood samples were taken before and up to 10 min after epinephrine administration. Regression analysis was performed of the correlated data. The values of mean arterial blood pressure and end-tidal CO(2) during the time of observation did not differ between groups. Total plasma epinephrine concentrations showed a significant increase in all groups, but with no difference between the tracheal groups. However, peak epinephrine levels in the intravenous group were significantly higher than in tracheal groups. We conclude that administration using three different tracheal instillation levels result in similar onset and peak plasma epinephrine levels in this setting and therefore the preferred method of tracheal epinephrine application for cardiopulmonary resuscitation may be selected by other criteria.

Epinephrine pharmacokinetics and pharmacodynamics following endotracheal administration in dogs: the role of volume of diluent

OBJECTIVE

to define the optimal volume of dilution for endotracheal(ET) administration of epinephrine (EPI).

DESIGN

prospective, randomized, laboratory comparison of four different volumes of dilution of endotracheal epinephrine (1, 2, 5, and 10 ml of normal saline).

SETTING

large animal research facility of a university medical center.

SUBJECTS AND INTERVENTIONS

epinephrine (0.02 mg/kg) diluted with four different volumes (1, 2, 5, and 10 ml) of normal saline was injected into the ET tube of five anesthetized dogs. Each dog served as its own control and received all four volumes in different sequences at least 1 week apart. Arterial blood samples for plasma epinephrine concentration and blood gases were collected before and 0.25, 0.5, 0.75, 1, 2, 3, 4, 5, 10, 15, 20, 25, 30 and 60 min after drug administration. Heart rate and arterial blood pressure were continuously monitored with a polygraph recorder.

MEASUREMENTS AND MAIN RESULTS

higher volumes of diluent (5 and 10 ml) caused a significant decrease of PaO2, from 147 +/- 8 to 106 +/- 10 torr, compared with the lower volumes of diluent (1 and 2 ml), from 136 +/- 10 to 135 +/- 7 torr (P < 0.05). These effects persisted for over 30 min. Mean plasma epinephrine concentrations significantly increased within 15 s following administration for all the volumes of diluent. Mean plasma epinephrine concentrations, maximal epinephrine concentration (Cmax) and the coefficient of absorption (Ka) were higher in the 5 and 10 ml groups. The time interval to reach maximal concentration (Tmax) was shorter in the 5 and 10 ml groups. Yet these results were not significantly different. Heart rate, systolic and diastolic blood pressures did not differ significantly between the groups throughout the study.

CONCLUSIONS

Dilution of endotracheal epinephrine into a 5 ml volume with saline optimizes drug uptake and delivery without adversely affecting oxygenation and ventilation.

Mastering pediatric cardiopulmonary resuscitation

Premature and unexpected death, especially in children, is tragic and very unacceptable. Effective treatments for sudden death of pediatric patients continue to emerge. Modern cardiopulmonary resuscitation function began with the widespread introduction of closed-chest cardiac massage in 1960; however, despite 35 years of research and refinement, more than 90% of children who receive cardiopulmonary resuscitation do not survive. This article summarizes and expands on current treatment concepts for pediatric sudden death. Emphasis is placed on procedures and techniques that likely are accessible in most medical centers caring for critically ill and injured children.

Comparison of intravenous and endotracheal administration of midazolam and the effect on pulmonary function and histology in the lamb model

OBJECTIVES

To determine the effect of endotracheal administration of midazolam on pulmonary function and histology in lambs.

DESIGN

Prospective, randomized, controlled study.

SETTING

Laboratory of the UpJohn Pharmaceutical Company.

TYPES OF PARTICIPANTS

Twenty male and female lambs weighing 10 to 20 kg.

INTERVENTIONS

The animals were anesthetized and placed on controlled ventilation. The animals were divided into four groups. The first two groups received endotracheal midazolam 0.1 and 0.2 mg/kg. The other two groups received IV midazolam 0.1 and 0.2 mg/kg. The endotracheal group had a catheter placed through the endotracheal tube, and midazolam was rapidly injected through the catheter followed by a 2-mL normal saline flush. Two rapid insufflations were administered, and the animals were then returned to the ventilator. Serum midazolam levels were drawn at one, two, five, ten, 15, and 20 minutes after both IV and endotracheal administration. Heart rate, respirations, SaO2 by oximetry, peak and mean airway pressure, compliance, airway resistance, and end-tidal CO2 were measured throughout the experiment. Lung sections were taken from control and treated animals receiving 0.1 and 0.2 mg/kg endotracheal midazolam, respectively. Sample lung sections were taken at 24, 48, and 120 hours after endotracheal midazolam administration.

MEASUREMENTS AND MAIN RESULTS

There were no statistical or clinically significant differences for pulmonary function between endotracheally and IV-administered midazolam. Histologic examination of the lungs at 24, 48, and 120 hours after endotracheal midazolam showed no pathologic changes in the control and study animals. Acceptable serum midazolam levels were achieved endotracheally with no clinically deleterious effects.

CONCLUSION

Endotracheal midazolam showed no significant deleterious effect on pulmonary function or histology in the lamb model.

Controversies in cardiopulmonary resuscitation: pediatric considerations

This article addresses some therapeutic controversies concerning medications that may be needed during advanced pediatric life support (APLS) and the routes of administration that may be selected. The controversies that are discussed include the appropriateness and selection of various routes for drug administration during APLS; the determination of whether epinephrine hydrochloride is the adrenergic agent of choice for APLS and its appropriate dose; treatment of acidosis associated with a cardiopulmonary arrest; recommendations for atropine sulfate doses; and the role, if any, of calcium in APLS. Background information differentiating pediatric from adult cardiopulmonary arrest is presented to enable the reader to have a better understanding of the specific needs of children during this life-threatening emergency. The article also presents an overview of various drugs used for APLS and a table of their typically recommended doses and routes of administration.

Differences in plasma lidocaine levels with endotracheal drug therapy secondary to total volume of diluent administered

Endotracheal drug therapy provides an effective alternative method for the administration of drugs in the numerous clinical settings in which intravenous access is difficult or impossible to obtain. However, the specific factors affecting endotracheal drug absorption and thus, the drug's plasma levels and effectiveness, has not yet been fully determined. Lidocaine alone or lidocaine mixed with normal saline was given endotracheally in four volumes (Volume I = undiluted with less than or equal to 5.5 cc total volume; Volume II = diluted to 6 cc total volume; Volume III = diluted to 12 cc total volume; Volume IV = diluted to 25 cc total volume) by the same technique of administration and in the same dosage of 4 mg/kg. Each dog served as its own control and received all four volumes of endotracheal lidocaine on different occasions. Plasma lidocaine levels at all four volumes and at all four time periods (5, 15, 30 and 60 min after giving endotracheal lidocaine) were obtained in each of the six dogs for a total of 96 plasma lidocaine levels measured in the study. Mean plasma lidocaine levels (micrograms/ml) at 5 min were: Volume I = 1.9, Volume II = 10.0, Volume III = 3.2 and Volume IV, = 4.3. These results were highly significant (P less than 0.001). The highest plasma lidocaine levels were obtained in the diluted volume, Volume II and the lowest plasma lidocaine levels in the undiluted volume, Volume I, with Volumes III and IV being intermediate.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of hypoxemia on pharmacokinetics of endotracheal lidocaine in dogs

Endotracheal administration is an effective alternative method for giving drugs in the many clinical situations in which it is difficult or impossible to quickly obtain an intravenous line. Yet whether various clinical conditions such as hypoxemia have any effect on endotracheal drug therapy is not known. Sixteen sets of plasma lidocaine levels were measured at 5, 15, 30, and 60 min after endotracheal lidocaine administration in eight dogs. Each dog was given the same dose of endotracheal lidocaine by the same technique of administration while in both a normal control state (Group I = 'Non-hypoxemia', mean Po2 = 98) and during hypoxemia (Group II = "Hypoxemia", mean Po2 = 36). Significantly higher plasma lidocaine levels occurred in the hypoxemic state (Group II) at time = 5 min while there was no significant difference in plasma lidocaine levels at time = 15, 30, and 60 min. Mean plasma lidocaine levels (micrograms/ml) at 5 min were: Group I = 1.38, Group II = 2.36 (significant at P less than 0.05). Plasma lidocaine levels were: Group I = 1.61 vs. Group II = 1.63 at time = 15 min, Group I = 1.11 vs. Group II = 1.10 at time = 30 min, and Group I = 0.54 vs. Group II = 0.51 at time = 60 min. Thus, there was a higher peak plasma lidocaine level and a shorter time to peak plasma lidocaine levels in the hypoxemic dogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Plasma lidocaine levels occurring with endotracheal administration during hemorrhagic shock

During the many emergency situations in which venous access is difficult or impossible, endotracheal drug administration is an effective alternative means of delivering life-saving medications. Shock is a commonly encountered emergency situation in which endotracheal drug therapy can and is often used. Yet whether a drug given endotracheally during shock can be absorbed from the lungs and pass into the bloodstream is not known. Forty-five sets of plasma lidocaine levels drawn at 5, 15, 30 and 60 min after the administration of endotracheal lidocaine at a dose of 2 or 4 mg/kg were obtained in dogs either in shock or in a normal control group: Group I = "Non-shock" or normal control, N = 27; Group II = "Shock", N = 18. Significantly higher plasma lidocaine levels occurred in the shock group in all time periods and with either dose of lidocaine (P less than 0.001). Mean plasma lidocaine levels (micrograms/ml) at 5 min were: (at 2 mg/kg dose) Group I = 1.1, Group II = 2.0; and (at 4 mg/kg dose) Group I = 2.3, and Group II = 5.1. The dose of lidocaine, the technique of administration, and the time at which the plasma lidocaine level was drawn as well as whether shock vs. non-shock was present were all highly significant factors (P less than 0.001) in determining plasma lidocaine levels. In summary: (1) endotracheal lidocaine is absorbed during shock and (2) higher plasma lidocaine levels occur during shock than during the non-shock control state. This suggests that the dosage of endotracheal medication may need to be adjusted for various clinical conditions such as shock.

The effect of dilution on plasma lidocaine levels with endotracheal administration

In the many emergency situations in which it is difficult or impossible to obtain venous access rapidly endotracheal drug therapy can be effective and life saving. Yet relatively little is known about endotracheal drug therapy. Plasma lidocaine levels were measured in 23 dogs after the administration of endotracheal lidocaine at a dose of 2 or 4 mg/kg. Endotracheal lidocaine was given either as a dilution with normal saline (1:1 dilution) or undiluted (Group 1, no dilution; Group 2, dilution). Significantly higher plasma lidocaine levels occurred with the dilution group in all the time periods and with either dose of lidocaine (2 or 4 mg/kg) (P less than .001). Mean plasma lidocaine levels (microgram/mL) at five minutes were: (at 2 mg/kg dose) Group 1, 0.64; Group 2, 3.4; and (at 4 mg/kg dose) Group 1, 1.9, Group 2, 4.7 (P less than .001). Arterial blood gases were not significantly different before or after endotracheal drug administration. This study suggests that higher plasma lidocaine levels are achieved and maintained longer when diluted with normal saline than when given undiluted; and higher plasma lidocaine levels can be obtained by dilution without any detrimental effect on respiratory function as measured by arterial blood gases.

Endotracheal diazepam: absorption and pulmonary pathologic effects

We conducted a study to evaluate the absorption of endotracheally administered diazepam and the pulmonary pathologic changes induced by its administration. Six cats received diazepam and five cats received saline endotracheally. Serial blood gases and serum diazepam levels were drawn at intervals for 90 minutes after the administration of diazepam. The cats were sacrificed after two days and their lungs were examined by a pathologist. Mean diazepam levels reached a peak two minutes after the administration of diazepam and remained elevated above therapeutic levels for 90 minutes. There was no significant change in pH, PO2, or PCO2 for either group. Histologic examination of the lungs showed a significantly increased incidence of pneumonitis in the diazepam group as compared to the saline group. This study demonstrates that although diazepam is well absorbed when administered endotracheally, it has adverse effects on the lungs that may preclude endotracheal use in the currently available commercial form.

Effect of technique of administration on plasma lidocaine levels

There are many clinical situations in which IV access is unavailable, and the endotracheal route is a valuable alternative route for drug therapy. The optimal technique of endotracheal drug administration, however, has not been determined. Twenty-nine dogs were divided into five groups and given endotracheal lidocaine at two doses, 2 mg/kg and 4 mg/kg, by differing techniques: control, undiluted lidocaine in a syringe was given as a bolus; needle, the drug was given through a needle attached to the syringe; dilution, lidocaine was diluted approximately 1:1 with normal saline and the entire dilution was given as a bolus; normal saline (NS) followup, lidocaine in a syringe was given as a bolus, followed immediately by an equal bolus of normal saline; and catheter, the drug was given through a catheter that was placed inside and extended just beyond the endotracheal tube. Mean plasma lidocaine levels (microgram/mL) at five minutes were as follows (at a 2-mg/kg endotracheal lidocaine dose): control, 0.64; needle, 0.0; dilution, 3.1; and (at a 4-mg/kg endotracheal lidocaine dose) control, 1.0; needle, 0.6; dilution, 6.2; NS followup, 1.9; and catheter, 1.9. At all time periods with either dose of lidocaine (2 or 4 mg/kg), the highest plasma lidocaine levels occurred with dilution and the lowest with the needle method. These results were highly significant (P less than .001). The highest plasma lidocaine levels may be attained by diluting the drug with normal saline. Higher levels were achieved when the drug was given through a catheter or when the drug was followed with a bolus of normal saline.(ABSTRACT TRUNCATED AT 250 WORDS)

Peripheral versus central venous delivery of medications during CPR

Traditionally drug delivery during cardiopulmonary resuscitation (CPR) has been considered to be equally effective when given through the peripheral venous and central venous routes. Recently, however, these routes of drug administration have undergone reevaluation. During normal flow drug delivery appears to be equally efficient by the peripheral venous and central venous routes. During CPR, however, drug administration by way of the supradiaphragmatic central circulation appears to result in significantly more rapid drug delivery to the central arterial circulation. Data regarding the effect of route of administration on quantitative peak levels are mixed. Changes in cardiac output and the mechanics of blood flow during CPR are thought to be responsible for these route-dependent rates of drug delivery.

Endotracheal bretylium tosylate in a canine model

This study was conducted to determine whether bretylium tosylate (BT) is effectively and safely absorbed through the endotracheal route in the canine model. Eleven adult mongrel dogs were anesthetized with pentobarbital, were orally intubated, and had continuous blood pressure and electrocardiographic monitoring. Four dogs received 5 mg/kg BT, three dogs received 10 mg/kg BT, two dogs received 20 mg/kg BT, and two control dogs were given volumes of normal saline equal to those given the 5- and 10-mg/kg groups. Each dog received the same dose of BT both endotracheally and intravenously, but in a random order and on different dates. Following each drug administration arterial blood was drawn at various intervals over two hours and sent for immediate gas analysis; serum samples were frozen for future determination of BT levels. Regardless of the amounts delivered, the peak levels of BT in the arterial blood following administration by the endotracheal route were consistently low (4.13 micrograms/mL to 14.00 micrograms/mL) when compared to those levels following intravenously administered BT (120 micrograms/mL to 268 micrograms/mL) (all P less than .002 for the 5- and 10-mg/kg groups). No depot effect was observed during a two-hour period. The arterial blood gases did not change significantly following the administration of BT by the endotracheal route in the 5- and 10-mg/kg groups, and sections of these autopsied dog lungs showed no apparent pathologic changes.