Martin S. Bogetz

A multicenter comparison of maintenance and recovery with sevoflurane or isoflurane for adult ambulatory anesthesia

Sevoflurane was compared with isoflurane in 246 adult ASA class I-III patients undergoing ambulatory surgery. After administration of midazolam 1-2 mg and fentanyl 1 microgram/kg, anesthesia was induced with propofol 2 mg/kg and maintained with either sevoflurane or isoflurane in 60% nitrous oxide to maintain arterial blood pressure at +/- 20% of baseline. Fresh gas flows were 10 L/min during induction and 5 L/min during maintenance. Times to eye opening, command response, orientation, and ability to sit without nausea and/or dizziness were significantly faster after sevoflurane. Significantly more sevoflurane patients met Phase 1 of postanesthesia care unit (PACU) Aldrete recovery criteria (> or = 8) at arrival, 95% vs 81%. Also, significantly more sevoflurane patients were able to complete psychomotor recovery tests during the first 60 min postanesthesia. Discharge times were not different. Sevoflurane patients had significantly lower incidences of postoperative somnolence (15% vs 26%) and of nausea both in the PACU (36% vs 51%) and in the 24-h postdischarge period (9% vs 24%). Patient satisfaction was high overall (sevoflurane 97%, isoflurane 93%). We conclude that sevoflurane is a useful inhaled anesthetic for maintenance of ambulatory anesthesia.

Parental upset associated with participation in induction of anaesthesia in children

To evaluate the magnitude of parental upset associated with participation in induction of anaesthesia in their child, we determined: (1) the features of induction most upsetting to parents; (2) the characteristics of parents most likely to become upset; and (3) the accuracy of the anaesthetist’s perception of the magnitude of parental upset. The parents (101 mothers and 43 fathers) of 103 children scheduled for elective outpatient surgery requiring general anaesthesia with induction by mask were asked on admission to participate in this study. Parents and children were educated about anaesthesia and surgery according to unit protocols. Immediately after induction of anaesthesia, the parents were asked to complete a demographic information sheet and the Parental Reactions to Anesthesia Induction Questionnaire. Responses were analyzed using descriptive statistics and content analysis. The most upsetting factors for both mothers and fathers in order of significance were: (1) separation from the child after induction of anaesthesia; (2) watching / feeling the child go limp during induction; and (3) seeing the child upset before induction. Characteristics of parents most likely to become upset revealed positive correlations between the amount of upset between mothers and fathers, mothers of an only child, and mothers or fathers who were health care workers (P < 0.05). The anaesthetist’s perception of upset correlated with maternal (P < 0.05), but not parental, self-assessment of upset. We conclude that selected factors of parental participation are upsetting for the parents and that recognizing the factors associated with parental upset may enable operating room personnel to minimize these negative consequences.RésuméPour évaluer l’importance de l’angoisse des parents associée à leur participation à l’induction de l’anesthésie de leur enfant, nous avons déterminé: 1) les aspects de l’induction les plus angoissants pour les parents; 2) les caractéristiques des parents les plus susceptibles d’être perturbés; 3) la justesse de la perception par l’anesthésiste de l’importance de l’angoisse parentale. Au moment de l’admission, nous avons sollicité la participation des parents (101 mères et 43 pères) de 103 enfants programmés pour une chirurgie ambulatoire sous anesthésie générale avec induction au masque. Nous avons renseigné les parents et les enfants sur l’anesthésie et la chirurgie conformément aux protocoles en usage. Immédiatement après l’induction de l’anesthésie, nous avons demandé aux parents de remplir une formule de données démographiques et un questionnaire sur leurs réactions à l’induction de l’anesthésiste. Les réponses furent analysées par statistiques descriptives et analyse de contenu. Par ordre d’importance, les facteurs les plus angoissants pour les parents sont les suivants: 1) leur séparation de l’enfant après l’induction; 2) la flaccidité de l’enfant pendant l’induction; et 3) l’angoisse de l’enfant avant l’induction. Les caractéristiques des parents les plus susceptibles d’être perturbés révélent des corrélations positives entre l’importance des perturbations entre les mères et les pères, les mères d’enfants uniques, et les mères ou les pères travaillant dans le secteur de la santé (P < 0,05). La perception par l’anesthésiste de l’angoisse parentale corrélait bien avec l’auto-évaluation maternelle (P < 0,05) mais non avec l’auto-évaluation paternelle. Nous concluons que certains facteurs de la participation des parents sont angoissants et que la connaissance de ces facteurs permettra au personnel des salles d’opération d’en minimiser les conséquences négatives.

Clinical and Economic Factors Important to Anaesthetic Choice for Day-Case Surgery

AbstractClinical and economic factors that are important to consider when selecting anaesthesia for day-case surgery can differ from those for inpatient anaesthesia. Patients undergoing day-case surgery tend to be healthier and have shorter durations of surgery. They expect less anxiety before surgery, amnesia for the surgical experience, a rapid return to normal (normal mentation with minimal pain and nausea) after surgery, and lower expenses. However, the latter 2 expectations can conflict; older generic drugs have lower acquisition costs but often impose longer recovery times. Longer recovery periods can increase costs by prolonging the time to discharge from labour-intensive areas such as the operating suite or the postanaesthesia recovery unit.The challenge for today’s anaesthetist is to use newer drugs judiciously to minimise their expense without compromising the rate or quality of recovery. Several approaches can secure these aims. Most apply the least anaesthetic needed. ‘Least anaesthetic’may mean the particular form of anaesthetic (e.g. local infiltration with monitored anaesthesia care versus a general anaesthetic), or may mean the delivery of the smallest effective dose, perhaps guided by anaesthetic monitors such as end-tidal analysers or the bispectral index.For patients requiring general anaesthesia, a combination of several drugs usually secures the closest approach to the ideal. Drug combinations used usually include a short-acting preoperative anxiolytic (e.g. midazolam), intravenous propofol (a short-acting potent anxiolytic and amnestic agent) for induction of anaesthesia (and sometimes for maintenance) and primary maintenance of anaesthesia with inhaled nitrous oxide combined with a poorly soluble (low solubility produces rapid recovery; the least soluble is desflurane) potent inhaled anaesthetic delivered at a low inflow rate (to minimise cost). Although old, nitrous oxide is inexpensive and has favourable pharmacokinetic and cardiovascular advantages; however, it is limited in its anaesthetic/amnestic potency, and has the capacity to increase nausea.In children, induction of anaesthesia is often accomplished with sevoflurane rather than desflurane; although sevoflurane is modestly more soluble than desflurane, it is nonpungent whereas desflurane is pungent. Moderate- or shortacting opioids (fentanyl is popular) or nonsteroidal anti-inflammatory agents (especially ketorolac), or local anaesthetics are added to secure analgesia during and after surgery. Similarly, when needed,moderate- or short-acting muscle relaxants are selected. Before the end of anaesthesia, an intravenous antiemetic may be given. With this drug combination, patients usually awaken within minutes after anaesthesia and can often move themselves to the vehicle for transport to the recovery unit. These combinations of anaesthetics and techniques minimise use of expensive drugs while expediting recovery (again minimising cost) with minimal or no compromise in the quality of recovery.

Minimum alveolar concentrations (MAC) of halothane and nitrous oxide in swine.

To compare anesthetic effects using a swine model, we needed to know the minimum alveolar concentrations (MAC) of halothane and nitrous oxide that produce anesthesia in the pig. This information does not exist in the literature. Furthermore, MAC varies considerably among species: by more than 60% for halothane, and by more than 200% for nitrous oxide. Therefore, using eight young swine, we determined mean (± sem) MAC values for halothane (1.25 ± 0.04% of one atmosphere) and nitrous oxide (277 ± 18% of one atmosphere). These values are higher than values reported for other mammals. Factors possibly accounting for this variability include interspecies differences, age, body temperature, increased sympathetic activity, and differences in methodology.

Pre-hospital tracheal intubation versus esophageal gastric tube airway use: A prospective study

A prospective study compared the respiratory effectiveness of the endotracheal tube (ET) with that of the esophageal gastric tube airway (EGTA) for victims of nontraumatic cardiac arrest in the pre-hospital setting. Arterial blood gases were obtained within 3 minutes of hospital arrival, and survival (defined as discharge from the hospital) was determined. During EGTA ventilation, mean pH was 7.12 +/- 0.2, mean P02 was 77 +/- 92 mm Hg, and mean PC02 was 78.2 +/- 42.9 mm Hg; the survival rate was 4.5%. During ET ventilation, mean pH was 7.34 +/- 0.2, mean P02 was 265 +/- 151 mm Hg, mean PC02 was 35 +/- 20.5 mm Hg; the survival rate was 7%. The authors conclude that endotracheal intubation remains the procedure of choice for airway management in the victim of cardiopulmonary arrest.

Too much of a good thing: uvular trauma caused by overzealous suctioning.

Anesthesia-related trauma to the uvula has been reported to be caused by compression and injury of the uvula by the endotracheal tube (l), the oral airway (2), the nasal airway (3), or the laryngeal mask (4). Such injury can go unnoticed, even though the potential exists for life-threatening airway obstruction (1,5). We report four cases of uvular trauma believed to be caused by excessive suctioning of the pharynx.

Using the laryngeal mask airway to manage the difficult airway.

Before 1990, the choice of an airway device essentially was limited to the facemask or the endotracheal tube. Since then, a number of novel supraglottic airway devices have been developed. The laryngeal mask airway (LMA) was introduced to the United States in 1991 after 3 years of use in the United Kingdom and other countries. Today the LMA has a clearly established role as an airway device in the elective setting when neither the procedure nor the patient require tracheal intubation. Perhaps more importantly, the LMA also has proved extremely useful in managing the difficult airway. This article reviews the use of the various LMA devices to manage the difficult upper airway.

Cardiovascular Actions of Nitrous Oxide or Halothane in Hypovolemic Swine

: During normovolemia, nitrous oxide causes mild sympathetic stimulation and direct myocardial depression; these effects offset each other, resulting in only minimal cardiovascular changes. To test the hypothesis that during hypovolemia this balance would change and depression predominate, 10 swine were made hypovolemic (30% blood loss) and then were given 70% N2O (0.25 MAC in swine) or an equipotent concentration of halothane, an agent that does not cause sympathetic stimulation. The alternate anesthetic was given to the same hypovolemic swine on another day. Five minutes after induction of anesthesia during hypovolemia, both N2O and halothane caused significant, physiologically important deterioration of compensation for hemorrhage. Halothane decreased systemic vascular resistance (SVR); N2O was more variable in its action, and SVR did not decrease significantly. Both agents caused similar decreases in cardiac output, mean aortic blood pressure, stroke volume, oxygen consumption, and left ventricular minute work, despite increases in plasma epinephrine concentration and plasma renin activity. No differences were found between groups for any of these variables (P greater than 0.05). Plasma norepinephrine concentration increased only in the N2O group and was greater in that group than in the halothane group. The deterioration of cardiovascular compensation for hemorrhage was expressed metabolically by similar decreases in the two groups in partial pressure of oxygen of mixed venous blood and by increases in blood lactate concentration. Thirty minutes after induction of anesthesia, with stable end-tidal anesthetic concentrations, both groups had some cardiovascular, but no metabolic, recovery.(ABSTRACT TRUNCATED AT 250 WORDS)

Formal Training in Anesthesia

References 1. Hurley RJ, Lambert DH. Continuous spinal anesthesia with a microcatheter technique: preliminary experience. Anestb Analg 1990;70:97-102. 2. Blaise GA, Coumoyer S, Perrault C, et al. Spinal catheter does not reduce post-dual puncture headache after Caesarean section [letter]. Can J Anaesth 1992;39:633-4. 3. Horlocker ‘IT, McGregor DG, Matsushige DK, et al. Neurologic complications of 603 consecutive continuous spinal anesthetics using macrocatheter and microcatheter techniques. An&h Analg 1997;84:1063-70. 4. Bevacqua BK. Continuous spinal anesthesia: operative indications and clinical experience. Reg An&h 1993;18:394-401. 5. Stand1 T, Eckert S, Schulte am Esch J. Microcatheter continuous spinal anaesthesia in the post-operative period: a prospective study of its effectiveness and complications. Eur J Anaesthesiol 1995;123273-9.

Developing an ambulatory surgery programme

Since the late 1970s out-patient surgery has been the fastest growing segment of surgical and anaesthetic care. This trend is likely to continue as advances in surgical technique and technology make surgery less invasive and therefore more amenable to the out-patient setting. The arthroscope, laparoscope, thoracoscope, and laser are the tools of ‘minimally invasive surgery’. Health care policy and economic factors will also continue to force more surgical procedures, as well as more infirm patients, into the out-patient setting. Conversely, the rate of shifting procedures and patients to the outpatient setting has slowed. The economic heyday of outpatient surgery in the United States is over and with it the boom in building hospital-independent (freestanding) out-patient surgical facilities. Most new or developing programmes will therefore locate within hospital walls or on the hospital grounds. Many hospitals mix ambulatory surgery patients with in-patients having elective surgery. Surgical outpatients may also compete with patients in need of urgent or emergency surgery. While this arrangement involves a minimum investment in space, staff and equipment, it fails to address the needs of the out-patient surgical population or to define the basis for an autonomous programme in ambulatory surgery. To define the needs of an ambulatory programme requires dedicated resources and a well-defined system to safely, effectively and efficiently meet the needs of out-patient physicians (surgeon, anaesthesiologist, oncologist, gas-