Choice of electrocardiography lead does not affect the usefulness of the T-wave criterion for detecting intravascular injection of an epinephrine test dose in anesthetized children

Cardiovascular and Vector-Cardiographic Effects of Articaine Anesthesia with Epinephrine

The aim was to investigate the vector-cardiographic effects in patients submitted to dental extraction under local anesthesia. Twenty-one patients aged 36.6 ± 12.4 years with a clinical and radiographic indication of mandibular or maxillary tooth extraction were enrolled. The intervention was a local or mandibular nerve block anesthesia with 4% articaine hydrochloride containing epinephrine (1 : 100,000; 40 mg/ml + 10 μg/ml). Blood pressure (BP), heart rate (HR), pulse wave transit time, and vector-cardiography data were recorded throughout 3 min before and 5 min after injection. QRS- and T-wave area under the curve (QRS AUC/T AUC) were calculated from the X/Y/Z QRS-vector or T-vector. T-wave amplitude (T AM), T AUC values, and diastolic BP decreased, and HR significantly increased 4 min after injection. A transient moderate HR drop and a corresponding small increase in T AM and T AUC immediately after the injection procedure may be explained by a decreased sympathetic tone due to psychological relief. In dental anesthesia, the systemic epinephrine effects are represented by a decrease in T AUC. These effects are most pronounced in the X- and Y-leads. The 3D determination of vector planes or amplitudes is a simple method to register the sympathetic tone in local anesthesia independently of possible effects on T-wave characteristics in single leads. In conclusion, T-wave determination may help to detect even small increases in systemic adrenaline concentration in case of accidental intravascular injection. At the same time, full rhythm and spatial ischemia control is provided.

Phenylephrine as a simulated intravascular epidural test dose in pediatrics: a pilot study

BACKGROUND

A test dose is used to detect intravascular injection during neuraxial block in pediatrics. Accidental intravascular epidural local anesthetic injection might be unrecognized in anesthetized children leading to potential life-threatening complications. In children, sevoflurane anesthesia blunts the hemodynamic response when intravascular cathecolamines are administered. No studies have explored the hemodynamics and the criteria for a positive test dose result following phenylephrine in sevoflurane anesthetized children.

METHODS

Healthy children undergoing minor procedures were randomly assigned to receive intravenous placebo, or 5 μg∙kg(-1) phenylephrine (n = 11/group) during sevoflurane anesthesia. Hemodynamic response was assessed using electrocardiography, pulse oxymetry and non-invasive blood pressure monitoring for 5 min following drug administration in anesthetized patients.

RESULTS

All patients receiving phenylephrine showed a decreased heart rate (HR) but not all of them met the positive criterion for test dose response. Overall, at 1 min, patients receiving phenylephrine showed a 25% decrease in HR from the baseline while an increase in blood pressure was noticed in 54% of patients receiving phenylephrine.

DISCUSSION

Phenylephrine might be a future indicator of positive intravascular test dose. Further investigation is needed to find out the phenylephrine dose that elicits a reliable hemodynamic response and whether phenylephrine needs to be dose age-adjusted in order to appreciate relevant hemodynamic changes in children receiving neuraxial blocks undergoing general anesthesia.

Electrocardiographic and blood pressure alterations caused by intravenous injection of ropivacaine - a study in piglets

OBJECTIVES

Objective signs to detect inadvertent intravascular injection of local anesthetics are essential in the anesthetized pediatric patient. For early detection of intravenous bupivacaine administration, it was shown that an epinephrine containing test dose reliably provoked T-wave alterations, changes in heart rate (HR) and blood pressure, whereas intravenous injection of plain bupivacaine could not be detected until high doses were applied. This study investigates electrocardiographic and hemodynamic alterations caused by intravenous ropivacaine.

METHODS

Twenty-four piglets, anesthetized with sevoflurane, were randomized into two groups: Group R received as test dose plain ropivacaine 0.2% and group RE, ropivacaine 0.2% + epinephrine 5 μg·ml(-1) . Under stable conditions, 0.2 ml kg(-1) of the test solution was intravenously injected. Twenty minutes later, 0.4 ml kg(-1) was applied. A positive effect was defined as HR increase ≥ 10 bpm, increase in mean arterial pressure (MAP) ≥ 15 mmHg, T-wave increase ≥ 25% baseline. In another setting ropivacaine was intravenously infused until cardiac arrest.

RESULTS

After injection of 0.2 or 0.4 ml kg(-1) test solution, a positive increase in HR and MAP was found in 0% of group R and in 100% of group RE. An increase in T-wave ≥ 25% was found in 42% of group R and in 100% of group RE. During intoxication, T-elevation was seen in 83%.

CONCLUSIONS

An epinephrine containing test dose ropivacaine reliably provoked T-wave elevations and increases in HR and MAP. A small dose plain ropivacaine caused T-elevations in a remarkable percentage, whereas higher, quite toxic doses provoked T-elevations in most of the pigs.

Absorption characteristics of epidural levobupivacaine with adrenaline and clonidine in children

AIM

To determine if the addition of adrenaline, clonidine, or their combination altered the pharmacokinetic profile of levobupivacaine administered via the caudal epidural route in children.

METHODS

Children aged <18 years old scheduled to undergo sub-umbilical surgery were administered caudal levobupivacaine plain 2.5 mg · ml(-1) or with adjuvants adrenaline 5 mcg · ml(-1) or clonidine 2 mcg · ml(-1) or their combination. Covariate analysis included weight and postnatal age (PNA). Time-concentration profile analysis was undertaken using nonlinear mixed effects models. A one-compartment linear disposition model with first-order input and first-order elimination was used to describe the data. The effect of either clonidine or adrenaline on absorption was investigated using a scaling parameter (Fabs(CLON), Fabs(ADR)) applied to the absorption half-life (Tabs).

RESULTS

There were 240 children (median weight 11.0, range 1.9-56.1 kg; median postnatal age 16.7, range 0.6-167.6 months). Absorption of levobupivacaine was faster when mixed with clonidine (Fabs(CLON) 0.60; 95%CI 0.44, 0.83) but slower when mixed with adrenaline (Fabs(ADR) 2.12; 95%CI 1.45, 3.08). The addition of adrenaline to levobupivacaine resulted in a bifid absorption pattern. While initial absorption was unchanged (Tabs 0.15 h 95%CI 0.12, 0.18 h), there was a late absorption peak characterized by a Tabs(LATE) 2.34 h (95%CI 1.44, 4.97 h). The additional use of clonidine with adrenaline had minimal effect on the bifid absorption profile observed with adrenaline alone. Neither clonidine nor adrenaline had any effect on clearance. The population parameter estimate for volume of distribution was 157 l 70 kg(-1). Clearance was 6.5 l · h(-1) 70 kg(-1) at 1-month PNA and increased with a maturation half-time of 1.6 months to reach 90% of the mature value (18.5 l · h(-1) 70 kg(-1)) by 5 months PNA.

CONCLUSIONS

The addition of adrenaline decreases the rate of levobupivacaine systemic absorption, reducing peak concentration by half. Levobupivacaine concentrations with adrenaline adjuvant were reduced compared to plain levobupivacaine for up to 3.5 hours. Clonidine as an adjuvant results in faster systemic absorption of levobupivacaine and similar concentration time profile to levobupivacaine alone. Adding adrenaline with clonidine does not alter the concentration profile observed with adrenaline alone.

Pharmacology in the very young: anaesthetic implications

Anaesthesia dosing in infants (0-2 years) should be based on pharmacokinetic-pharmacodynamic considerations and adverse effects profiles. Disease processes and treatments in this group are distinct from those in adults. Absorption, distribution and clearance change dramatically during this period because of maturation of anatomical and physiological processes as well as behavioural changes. Pharmacogenomic expression also matures in this period. Population-based and physiological-based pharmacokinetic modelling has improved the understanding of maturation and subsequent dose approximation. Postmenstrual, rather than postnatal, age is a reasonable measure for maturation. There remains a need for clinically applicable tools to assess pharmacodynamics which can provide response feedback; this has been achieved for neuromuscular monitoring, but not yet fully for depth of anaesthesia, sedation or pain. Morbidity and mortality associated with paediatric anaesthesia have historically been highest in this age group and continue to be so. Some of this morbidity was attributable to a poor understanding of developmental pharmacology; this facet continues to plague the specialty.

Impact of propofol on electrocardiographic alterations during intravascular application of bupivacaine--a study in piglets

BACKGROUND

Intravascular application of a small dose of local anesthetics (LA) with epinephrine as well as larger doses of LA under sevoflurane anesthesia results in increase in T-wave amplitude in the electrocardiogram (ECG). The aim of this study was to elucidate whether propofol anesthesia affects these ECG alterations or not.

METHODS

Thirty neonatal pigs were randomized into two groups. Group 1 was anesthetized with sevoflurane, group 2 with sevoflurane plus continuous propofol infusion (10 mg·kg(-1)·h(-1)). A test dose of 0.2 ml·kg(-1) bupivacaine 0.125% + epinephrine 1 : 200,000 was injected intravenously. Arterial pressure was monitored. ECG was analyzed for changes in T-wave amplitude (positive if ≥25% baseline) and heart rate. In another setting, bupivacaine 0.125% was intravenous infused at a rate of 4 mg·kg(-1)·min(-1). ECG was analyzed for alteration in T-wave amplitude and heart rate at 1.25, 2.5, and 5 mg·kg(-1) bupivacaine infused.

RESULTS

T-wave elevation after the administration of an epinephrine containing LA test dose was similar between the two groups. Increase in heart rate caused by the test dose were significantly higher in group 2 (P = 0.008). During continuous bupivacaine administration, T-wave elevation occurred in 40% and 71% (group 1 and 2) at 1.25 mg·kg(-1), in 80% and 100% at 2.5 mg·kg(-1), and in 93% and 86% at 5 mg·kg(-1) bupivacaine infused.

CONCLUSION

Continuous propofol infusion does not suppress the ECG signs of a systemically administered epinephrine containing LA test dose nor does it suppress the ECG signs caused by high doses of intravenous applied bupivacaine.

Clinically unrecognized intravascular placement of epidural catheter in a child--an argument for the use of radio-opaque contrast?

An epidural catheter was inserted after induction of anesthesia in a 28.2 kg 9-year-old boy scheduled to undergo bilateral femoral varus derotational osteotomies. There was no gravity free flow of blood down the catheter and there was no blood aspirated with a 2 ml syringe. After a negative test dose of a 4 ml solution of 0.25% levobupivacaine with epinephrine 1 : 200 000, a further 8 ml was administered via the epidural catheter. No significant increase in heart rate was noted. On surgical skin incision the heart rate increased from 94 to 116 b.min(-1) and blood pressure increased from 104/44 to 116/46 mmHg. A further 3 ml 0.25% levobupivacaine with epinephrine and clonidine 2 mug.kg(-1) were administered via the epidural catheter. The operation continued uneventfully although it was noted that the heart rate increased intermittently during the procedure. In view of the unexplained tachycardia and a history of cerebral palsy with the potential for postoperative muscle spasms, it was felt important to have a reliable epidural. To confirm placement, 2 ml of Isovue 300 (Iopamidol) was administered via the epidural catheter. X-ray screening demonstrated intravascular placement and the rapid disappearance of contrast. The catheter was removed and reinserted. Contrast demonstrated good spread in the epidural space. The merits of screening with contrast for epidural catheter placement in children are discussed.

The Epidural Test Dose: A Review

This review systematically examines the literature on the ability of the classical epidural test dose and other strategies to detect intravascular, intrathecal, or subdural epidural needle/catheter misplacement. For detection of simulated intravascular misplacements, a sensitivity (S) and a positive predictive value (PPV) > or =80 demonstrated by at least two randomized controlled trials coming from two different centers were determined for the following tests and patient populations: Nonpregnant adult patients = increase in systolic blood pressure (SBP) > or =15 mm Hg (S = 80-100 and 93-100; PPV = 80-100 and 83-100) or either an increase in SBP > or =15 mm Hg or an increase in heart rate > or =10 bpm after the injection of 10 (S = 100; PPV = 83-100) or 15 microg of epinephrine (S = 100; PPV = 83-100); pregnant patients = sedation, drowsiness, or dizziness within 5 min after the injection of 100 microg of fentanyl (S = 92-100; PPV = 91-95); and children = increase in SBP > or =15 mm Hg after the injection of 0.5 microg/kg of epinephrine (S = 81-100; PPV = 100). Conversely, more studies are required to determine the best strategies to detect intrathecal and subdural epidural needle/catheter misplacements in these three patient populations.

Pharmacokinetics and efficacy of ropivacaine for continuous epidural infusion in neonates and infants

INTRODUCTION

The primary objective of this noncomparative study was to evaluate the pharmacokinetics of ropivacaine during a 48-72-h continuous epidural infusion of ropivacaine in children under 1 year. The secondary objectives were to assess efficacy and safety.

METHODS

Neonates and infants (ASA I-III, gestational age > or =37 weeks, > or =2.5 kg, scheduled for major abdominal or thoracic surgery) were included and separated into age groups: 0-30 (neonate), 31-90, 91-180, and 181-365 days. Ethics committee approval and informed parental consent were obtained before inclusion. An epidural catheter was introduced under general anesthesia at the appropriate dermatomal level. An initial bolus dose (0.9-2.0 mg.kg(-1) of ropivacaine 0.2%) was followed by an epidural infusion (0.2 mg.kg(-1).h(-1) for infants <180 days or 0.4 mg.kg(-1).h(-1) for infants >180 days). Plasma samples were collected every 12 h from 24 h, and on termination of the epidural infusion. Postoperative pain was evaluated using both the Objective Pain Scale and a four-graded descriptive scale.

RESULTS

Forty-five infants, median age 116 (0-362) days, were included. Forty-three and 19 patients received an infusion for at least 48 and 72 h, respectively. Satisfactory analgesia was provided in the majority, only 20 patients were given supplementary medication during the infusion. In all age groups, plasma concentrations of unbound ropivacaine leveled at 24 h, without any further increase at 48 and 72 h. Because of lower clearance of unbound ropivacaine in neonates (mean 33 ml.min(-1).kg(-1)) than in infants above the age of 30 days (80, 124, and 163 ml.min(-1).kg(-1), respectively, in the age groups 31-90, 91-180, and 180-365 days), unbound ropivacaine concentrations at the end of infusion were higher in neonates [median 0.10 mg.l(-1) (0.04-0.21 mg.l(-1))] than in infants >30 days [median 0.03 mg.l(-1) (0.003-0.10 mg.l(-1))].

CONCLUSION

Epidural infusions (0.2-0.4 mg.kg(-1).h(-1) ropivacaine) provided satisfactory pain relief in neonates and infants under 1 year. As plasma concentrations of unbound ropivacaine were not influenced by the duration of the infusion, ropivacaine can be safely used for postoperative epidural infusion for 48-72 h. Levels of unbound ropivacaine were higher in the neonates than in the infants, but were below threshold concentrations for CNS toxicity in adults (> or =0.35 mg.l(-1)). This should not preclude the use of ropivacaine infusions in neonates but suggests a need for caution during the first weeks of life.

Cardiovascular responses in patients with acute allergic reactions treated with parenteral epinephrine

The present study describes the cardiovascular responses to epinephrine (Epi) given into the arm, in adult patients with acute allergic reactions, and the differential responses to subcutaneous (SC) and intramuscular (IM) administration. Sixty-three adult patients were treated with Epi administered SC or IM after H1 and H2 receptor blockade. Heart rate and blood pressure (BP) were then measured for 20 minutes. Changes in heart rate and BP variables were analyzed. Pulse pressure and systolic BP showed increases with time. Diastolic BP also showed a modestly decreasing values over time. Heart rates did not change. Time-related changes between IM and SC Epi treatment were not observed. Sex influenced timed BP values and a significant sex by time effect was observed. In subset analysis, only male patients showed an overall time effect for BP variables, especially pulse pressure. In conclusion, adults with acute allergic syndromes treated with arm-injected Epi show a modest but definite increase in pulse pressure and systolic BP. This pattern is observed more in males. Heart rate and blood pressure differences between IM and SC arm-injected Epi treatments do not appear to be significant.