David L. Dull

Role of monitoring devices in prevention of anesthetic mishaps: a closed claims analysis.

Anesthesiologist-reviewers examined 1,175 anesthetic-related closed malpractice claims from 17 professional liability insurance companies. The claims were filed between 1974 and 1988. The reviewers were asked to determine if the negative outcome was preventable by proper use of additional monitoring devices available at the time of the review even if not available at the time the incident occurred, and if so, which devices could have been preventative. In 1,097 cases sufficient information was available to make a judgment regarding preventability of the morbidity or mortality by application of additional monitoring devices. It was determined that 31.5% of the negative outcomes could have been prevented by application of additional monitors. Using the insurance industrys scale of 0 (no injury) to 9 (death), the median severity of injury for incidents deemed preventable was 9 compared with 5 for those deemed not preventable (P less than 0.01, scale detailed in text). The severity of injury scores were the same for preventable mishaps occurring during regional or general anesthesia, suggesting that additional monitoring devices may be equally efficacious in preventing serious negative outcomes during either regional or general anesthesia. The judgements or settlements of the incidents judged preventable by additional monitoring were 11 times more costly (P less than 0.01) than those mishaps not judged preventable. The monitors determined by the reviewers to be most useful in mishap prevention were pulse oximetry plus capnometry. Applied together, these two technologies were considered potentially preventative in 93% of the preventable mishaps.(ABSTRACT TRUNCATED AT 250 WORDS)

Additive Contribution of Nitrous Oxide to Halothane Mac in Infants and Children

Fifty-one infants and small children (14.7 ± 7.2 mo) were studied to determine the MAC of halothane in O2 (n = 11) and in the presence of three different nitrous oxide (N2O) concentrations (25% [n = 13], 50% [n = 13], and 75% [n = 14]). In the three N2O groups, after randomly assigning patients to an N2O group, anesthesia was induced with halothane and N2O using a pediatric circle system. After endotracheal intubation, halothane and N2O end-expired concentrations were adjusted to predetermined concentrations. The initial halothane concentrations in each group were based on the assumption that each percent N2O reduced halothane concentrations by 0.01 vol % (assumed halothane MAC = 1.0 vol %). Based on the response of the preceding subject in each group, halothane concentrations were increased or decreased depending on whether the response was to move or not to move, respectively, in response to the surgical incision. The mean duration of constant end-tidal concentrations before skin incision was 10 min. End-tidal gases were sampled and measured from a separate distal sampling port of an endotracheal tube during controlled ventilation (Perkin-Elmer Mass Spectrometer). The MAC value for halothane in O2 was 0.94 ± 0.08 vol % (mean ± SD). The MAC values of halothane in the presence of 25%, 50%, and 75% N2O were 0.78 ± 0.12 vol %, 0.44 ± 0.10 vol %, and 0.29 ± 0.06 vol %, respectively. All concentrations of N2O significantly reduced the MAC of halothane. A regression analysis through all four data points yielded a linear relationship (r2 = 0.87) with a predicted MAC for N2O of 105 vol %. Unlike halothane and isoflurane, the predicted MAC of N2O in infants and children is similar to that reported by others in adults. Similar to the results of clinical studies in adults, the contribution of N2O to halothane MAC in children is additive.

Haemodynamic effects of atropine during halothane or isoflurane anaesthesia in infants and small children

In this study, two-dimensional and pulsed Doppler echocardiography were used to measure cardiovascular changes before and after IV atropine in 31 infants and small children during halothane (n = 15) or isoflurane (n = 16) anaesthesia. Prior to induction of anaesthesia heart rate (HR), mean blood pressure (MBP), and two0dimensional echocardiographic dimensions of the left ventricle and pulmonary artery bloodflow velocity were measured by pulsed Doppler echocardiography. Cardiovascular measurements were repeated while anaesthesia was maintained at 1.5 MAC halothane (n = 15) or isoflurane (n = 16). Atropine 0.02 mg·kg−1 IV was then administered and two minutes later, a third set of cardiovascular data was obtained. Heart rate decreased during halothane anaesthesia but did not change significantly during isoflurane anaesthesia. Mean blood pressure, cardiac output (CO) and stroke volume (SV) decreased similarly during 1.5 MAC halothane or isoflurane anaesthesia. Ejection fraction (EF) decreased and left ventricular end-diastolic volume (LVEDV) increased significantly in bothgroups, but decreases in EF (32 ± 5 percentvs18 ± 5 per cent) and increases in LVEDV (18 ± 7 per cent vs7 ± 5 per cent) were significantly greater during halothane than during isoflurane anaesthesia. Following atropine, HR increased more in the patients maintained with halothane (31 ± 6 per cent), than during isoflurane anaesthesia (18 ± 5 per cent). Atropine increased CO in both groups of patients, but SV and EF remained unchanged. When compared with awake values, HR increased similarly and significantly (18 ± 4 per cent) following atropine in both groups, and CO returned to control levels. Halothane decreased EF and increased LVEDV more than isoflurane at 1.5 MAC end— expired anaesthetic levels. Atropine did not diminish the myocardial depression produced by halothane or isoflurane. The increase in CO following atropine during halothane and isoflurane anaesthesia in infants and small children is the result of increases in HR alone.RésuméNous avons utilisé un appareil à échocardiographie bi-dimensionnelle couplé à un Doppler pulsé chez des bébés et de jeunes enfants pour évaluer l’impact hémodynamique de l’halothane (n = 15) et de l’isoflurane (n = 16) et la modification possible de ces effets par l’atropine. Nous avons mesure la frequence cardiaque (FC), la pression artérielle moyenne (PAM), la dimension de la cavité ventriculaire gauche (par écho bi-dimensionnelle) et la vélocité du flot sanguin pulmonaire (par Doppler) et ce, en trois occasions soit avant l’induction, après l’instauration de 1.5 MAC d’halothane ou d’isoflurane et finalement, deux minutes après l’injection IV de 0.02 mg·kg−1 d’atropine. On ne nota une baisse de la frequence cardiaque qu’avec l’halothane tandis que la PAM, le débit cardiaque (DC) et le volume d’éjection (VE) diminuaient autant avec l’un ou l’autre anesthésique. La diminution de la fraction d’éjection (FE) et l’augmentation du volume télédiastolique du ventricule gauche (VTDVG) significatives pour les deux groupes, étaienl plus marqué avec l’halothane qu’avec l’isoflurane: FE 32 ± 5 pour cent vs18 ±5 pour cent; VTDVG 18 ± 7 pour cent vs 7 ± 5 pour cent. Avec l’atropine, la FC monta plus dans le groupe halothane (31 ± 6 pour cent) que dans le groupe isoflurane (18 ± 5 pour cent), le DC augmentant dans les deux groupes, alors que le VE et la FE demeuraient inchangés. Comparée aux mesures pré-induction, l’atropine amenait une hausse significative de la FC, semblable dans les deux groupes (18 ± 4 pour cent) et restaurait le DC. Donc, chez les bebes et les jeunes enfants, a 1.5 MAC, l’halothane diminue la FE et augmente le VTDVG plus que ne le fait l’isoflurane. L’atropine ne modifie pas la depression myocardique et elle ne restaure le DC que par une hausse de la FC.

Haemodynamic effects of rectal methohexitone for induction of anaesthesia in children

Pulsed Doppler and two-dimensional echocardiography were used to determine the haemodynamic effects of rectal methohexitone in 12 children32.4 ± 3.8 months old and weighing 13.3 ± 1.1 kg (mean ± SEM). Heart rate, blood pressure and echocardiographic measurements of cardiac output, stroke volume and left ventricular end-diastolic and end— systolic volumes were obtained prior to the induction of anaesthesia. Anaesthesia was induced with 25 mg · kg−1 two per cent rectal methohexitone. Immediately following the onset of sleep all cardiovascular measurements were repeated. Following the induction of anaesthesia with rectal methohexitone there was a significant increase in heart rate. Blood pressure, cardiac index, stroke volume and ejection fraction were unchanged. It is concluded that rectal administration of two per cent methohexitone for the induction of anaesthesia in healthy paediatric patients has minimal haemodynamic effect.RésuméNous avons utilisé un appareil à echographie bi-dimensionnelle couplé à un Doppler pulsé pour mesurer l’impact Mémodynamique du methohexital par voie rectale chez 12 enfants de 32.4 ± 3.8 mois pesant 13.3 ± 1.1 kg (moyenne ± erreur-type). La dose d’induction de l’anesthésie etait de 25 mg · kg−1 d’une solution a deux pour cent. Nous mesurions la fréquence cardiaque, la pression artérielle, le débit cardiaque et les volumes télésystoliques et télé-diastoliques du ventricule gauche juste avant l’ induction et dés la perte de conscience de l’enfant. Avec l’induction, le pouls s’est accéléré mais la pression artérielle, l’index cardiaque et les volume et fraction d’ éjection n’ont pas changé. Il semble donc que l’induction de l’ anesthésie avec du méthohexital deux pour cent par voie rectale air peu d’effets hémodynamiques chez les enfants en santé.

Hemodynamic responses to nitrous oxide during inhalation anesthesia in pediatric patients

STUDY OBJECTIVE To measure the hemodynamic changes produced by nitrous oxide (N2O) during halothane and isoflurane anesthesia in infants and children. DESIGN A repeated measures design in two groups of infants and small children. SETTING Operating rooms at a university hospital. PATIENTS Nineteen healthy unmedicated infants and small children (mean age 12 months) who required elective surgery. INTERVENTIONS Prior to anesthesia induction, cardiovascular measurements were recorded using pulsed Doppler and two-dimensional echocardiography. Following anesthesia induction with halothane (n = 10) or isoflurane (n = 9) in oxygen (O2) and air, anesthetic measures were stabilized at 1.0 minimum alveolar concentration (MAC) and cardiovascular measures were repeated. After 30% N2O was added to the 1.0 MAC anesthetic concentration, a third set of cardiovascular measurements was recorded. A final cardiovascular data set was measured 5 minutes following an increase in N2O concentration to 60%. MEASUREMENTS AND MAIN RESULTS Mean arterial pressure (MAP), cardiac index (CI), stroke volume (SV), and ejection fraction (EF) decreased similarly and significantly at 1.0 MAC halothane and isoflurane. Heart rate (HR) increased during isoflurane anesthesia but decreased during halothane anesthesia. The addition of N2O resulted in a decrease in HR, CI, and MAP when compared to 1.0 MAC levels of halothane or isoflurane; however, SV and EF were not significantly changed from levels measured during 1.0 MAC halothane or isoflurane. CONCLUSIONS The addition of N2O to halothane and isoflurane anesthesia in infants and children decreased HR. This decrease led to a decrease in cardiac output (CO). Unlike with adults, N2O did not produce cardiovascular signs of sympathetic stimulation in infants and children.

Pharmacokinetics of two per cent rectal methohexitone in children.

Plasma methohexitone concentrations were determined in 60 children, aged one to six years, following administration of 15mg·kg-1, 20mg·kg-1, 25 mg·kg-1 or30 mg·kg-1 two percent rectal methohexitone. Time to the onset of sleep was determined by a blinded observer and venous blood samples obtained 15, 30, 45 and 120 minutes following drug administration. Fifty of 60 children were asleep within 15 minutes. Nine of the ten children that did not fall asleep were sedate and could be separated easily from their parents to undergo inhalational induction of anaesthesia. Time to the onset of sleep was inversely related to the dose of rectal methohexitone administered. Sleep was achieved more reliably following the use of 25 to 30 mg ·kg-1 rectal methohexitone. In addition, plasma methohexitone concentrations following 30 mg ·kg-1 rectal methohexitone were significantly higher for up to 120 minutes following drug administration than the plasma concentrations achieved after 15 mg·kg-1 or 20 mg·kg-1 methohexitone. There was no difference in the incidence of complications. The authors recommend that clinical circumstances be carefully considered and the dose of rectal methohexitone administered be individualized to meet the specific anaesthetic requirements of each child.RésuméSuite à ľadministration intra-rectale de 15, 20, 25 et 30 mg · kg-1 de méthohexital à deux pour cent, nous en avons mesuré les taux sériques chez 60 enfants de un à six ans. Nous avons prélevé les échantillons veineux à 15, 30, 45 et 120 minutes post-administration et un tiers indépendant chronométrait ľintervalle ďaction jusqu’à ľapparition de somnolence, Chez cinquante des enfants, cet intervalle était inférieur à 15 minutes alors qu’au même moment, neuf des dix autres étaient assez calmes pour qu’on les sépare de leurs parents et qu’on procède à une induction par inhalation. ľintervalle ďaction s’est avéré inversement proportionnel à la dose de méthohexital utilisée et la somnolence atteinte plus efficacement à des doses de 25 et de 30 mg·kg-1. De plus, à 120 minutes, les taux sériques avec une dose de 30 mg ·kg-1 étaient supérieurs à ceux atteints avec 15 ou 20 mg ·kg-1. La dose n’a pas eu ďinfluence sur ľincidence de complication. Nous croyons que le jugement clinique doit présider à ľindividualisation des doses appropriées aux besoins anesthésiques de chaque enfant.

Efficacy of prior skin puncture in preventing iv catheter damage

The efficacy, with respect to preventing iv catheter damage, of creating a skin entry site by first piercing the skin with a large gauge needle through which an over-the-needle teflon catheter is then placed was evaluated. In 50 adult volunteers two 22-gauge iv cathéters and two 24-gauge cathéters were placed through the forearm skin into the subcutaneous tissue. One catheter of each size was placed through an entry site created by piercing the skin with an 18-gauge disposable, stainless steel needle. One catheter of each size was inserted through nearby skin without creation of an entry site. Two to three weeks after insertion all cathéters, along with 50 cathéters of each size that had not been inserted, were examined under a microscope for evidence of damage. Intravenous catheter damage was more prevalent in the 24-gauge cathéters than the 22-gauge cathéters (P < 0.05). No différences in frequency of damage were noted for either gauge catheter inserted through an entry site comparéd with those inserted without a prior skin puncture. Twenty-four-gauge cathéters, but not 22-gauge cathéters, placed into the subcutaneous tissue were damaged more frequently than were cathéters that had never been inserted (control cathéters). This study demonstrated that 24-gauge cathéters are more likely to be damaged during insertion into the subcutaneous tissue than are 22-gauge cathéters. We also demonstrated that creation of a skin entry site by piercing the epidermis with a needle of larger gauge than the catheter to be placed is not efficacious in preventing intravenous catheter damage during insertion.RésuméL’ efficacité, concernant la prévention de dommage au cathéter intraveineux, par la création d’ un site d’ entrée à travers la peau par la ponction au préalable avec une aiguille de grand calibre, à travers lequel un cathéter de teflon sur une aiguille métallique est placé ultérieurement, a été évaluée. Chez 50 volontaires adultes deux cathéters intraveineux calibre 22 et deux cathéters calibre 24 seraient placés à travers la peau de la membrane dans le tissu sous-cutané. Un cathéter de ce calibre fut placé à travers un site d’ entrée créé par la ponction de la peau avec une aiguille métallique disposable de calibre 18. Le cathéter de chaque calibre fut inséré à travers la peau avoisinante sans la création des sites d’entrée. Deux à trois semaines après l’ insertion de tous les cathéters et 50 cathéters de chaque calibre qui ne furent pas installés, furent examinés sous microscope pour mettre en évidence les dommages. Les dommages aux cathéters intraveineux étaient plus fréquents pour les cathéters de calibre 24 que ceux de calibre 22 (P < 0.05). Aucune différence ne fut notée concernant le dommage aux cathéters insérés à travers un site d’ entrée comparé à ceux insérés sans site d’ entrée. Les cathéters de calibre 24, mais non ceux de calibre 22 placés dans le tissu souscutané démontraient un dommage plus fréquémment que les cathéters qui n’ ont jamais été insérés (cathéters contrôle). L’étude démontre que les cathéters de calibre 24 étaient plus susceptibles aux dommages lors de l’ insertion dans le tissu souscutané que ceux de calibre 22. On a aussi démontré que la création d’ un site d’ entrée à travers la peau par la perforation de l’ épiderme avec une aiguille plus grosse que le cathéter n’ était pas efficace pour prévenir les dommages aux cathéters lors de l’ insertion.

EFFICACY OF PRIOR SKIN PUNCTURE IN PREVENTING IV CATHETER DAMAGE

The efficacy, with respect to preventing i.v. catheter damage, of creating a skin entry site by first piercing the skin with a large gauge needle through which an over-the-needle teflon catheter is then placed was evaluated. In 50 adult volunteers two 22-gauge i.v. catheters and two 24-gauge catheters were placed through the forearm skin into the subcutaneous tissue. One catheter of each size was placed through an entry site created by piercing the skin with an 18-gauge disposable, stainless steel needle. One catheter of each size was inserted through nearby skin without creation of an entry site. Two to three weeks after insertion all catheters, along with 50 catheters of each size that had not been inserted, were examined under a microscope for evidence of damage. Intravenous catheter damage was more prevalent in the 24-gauge catheters than the 22-gauge catheters (P less than 0.05). No differences in frequency of damage were noted for either gauge catheter inserted through an entry site compared with those inserted without a prior skin puncture. Twenty-four-gauge catheters, but not 22-gauge catheters, placed into the subcutaneous tissue were damaged more frequently than were catheters that had never been inserted (control catheters). This study demonstrated that 24-gauge catheters are more likely to be damaged during insertion into the subcutaneous tissue than are 22-gauge catheters. We also demonstrated that creation of a skin entry site by piercing the epidermis with a needle of larger gauge than the catheter to be placed is not efficacious in preventing intravenous catheter damage during insertion.