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Intravenous or Inhaled Induction of Anesthesia in Adults? An Audit of Preoperative Patient Preferences

van den Berg, Anton A. FRCA; Chitty, Dudley A. MD; Jones, Ramoun D. MD; Sohel, Mir S. MD; Shahen, Ali MD

doi: 10.1213/01.ANE.0000150609.82532.C5
Economics, Education, and Health Systems Research: Research Report

If given a choice, would patients prefer an inhaled or IV method of inducing anesthesia? We investigated the choice between inhaled and IV induction of anesthesia of adult patients presenting to an academic institution for ambulatory surgery. Of 240 patients audited at the preoperative visit, 212 (88%) reported anesthetic histories in which anesthesia had been induced IV and by inhalation in 203 (96%) and 5 (2%) patients, respectively, with the remaining 4 (2%) having no recall of route of the induction of anesthesia. Seventy-eight (33%) patients selected IV induction, 120 (50%) chose inhaled induction, and 42 (17%) patients were undecided. Sevoflurane was used successfully for induction in 154 patients to whom it was offered. These findings seem to contradict the concept that most adult patients have an aversion to anesthesia masks and suggest that a fear of needle stick may be more prevalent among some populations of American adults. Where manpower and facilities permit and in the absence of risk of regurgitation or airway difficulty, it is suggested that enquiry be made of healthy adults presenting for elective ambulatory surgery as to their preferred route for the induction of anesthesia.

IMPLICATIONS: The majority of adult American patients presenting for ambulatory surgery to a university teaching hospital in Texas choose an inhaled rather than IV induction of anesthesia.

Department of Anesthesiology MSB 5.020, Medical School, University of Texas, Houston

Accepted for publication October 29, 2004.

Address correspondence and reprint requests to A.A. van den Berg, FRCA, Department of Anesthesiology, Mayo General Hospital, Castlebar, County Mayo, Ireland. Address e-mail to antonvdb2000@yahoo.com.

There is increasing interest in exploring patients' perceptions, views, and preferences regarding everyday practices in anesthesia because it is acknowledged that guidelines based on patient preference are more likely to meet criteria for high quality care (1). Recently, recommendations regarding aspects of routine anesthesia practice have been based on audits of patient attitude to premedication and postoperative morbidity (2,3). The introduction of sevoflurane during the last decade has been accompanied by renewed interest in inhaled inductions of anesthesia in adults (4–6), and an audit of adult Australian women presenting for gynecological surgery revealed that the majority selected an inhaled rather than IV induction of anesthesia (7). However, no audit has been performed and published that canvasses the preoperative preferences of adult American patients regarding their choice of route of induction of anesthesia. Accordingly, we audited the choice between inhaled and IV induction of anesthesia of healthy adult patients presenting to our large general university teaching hospital for elective, ambulatory surgery.

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Method

With the approval of the institutional committee for the Protection of Human Subjects and patient consent, the preferences of 240 ASA grade I–II patients presenting for ambulatory surgery under general anesthesia administrated by the authors were audited. Each patient was visited by one of the authors in the Day Surgery Unit (DSU) before surgery and given a standard questionnaire. Patients in whom an IV cannula had already been inserted by nursing or surgical staff before the arrival of the anesthesiologist were excluded from the audit. After routine preoperative consultation, examination, discussion, and explanation of their anesthesia care, the response of each patient to the standard questionnaire was recorded. During the discussion, it was explained that an IV cannula would be inserted after loss of consciousness in those selecting the inhaled induction.

The questionnaire stated: “We want to give you the choice between two ways you can go to sleep in the operating room, both of which work just fine.

  1. The first choice is to use local anesthetic to put a small IV cannula on your hand or arm, either here or in the operating room, and through it to give you an injection of propofol or pentothal, which will send you off to sleep.
  2. The second choice is to gently hold a mask over your nose and mouth, when you are on the operating table in the operating room, and allow you to breathe an anesthetic gas called sevoflurane, which is essentially odorless and takes five to eight breaths to send you off to sleep. This is popular with children because it avoids using needles.”

Patients selecting the IV induction had an IV cannula inserted, after subcutaneous injection of lidocaine, by one of the investigators either immediately in the DSU or later in the operating room after application of electrocardiographic, oximetric, and noninvasive arterial blood pressure monitoring devices. Thereafter, after 1 min of preoxygenation with 100% oxygen administered by face mask and simultaneous performance of a mini-Bier's IV regional block using 2 to 3 mL of 2% lidocaine injected IV, anesthesia was induced by IV injection of propofol. Patients selecting the inhaled induction were transported on a trolley by one of the investigators to the operating room immediately before the induction. While the patient was being transferred from the trolley to the operating table, and standard monitoring devices were being applied, the circle absorber anesthesia circuit was primed with 8% sevoflurane in equal parts of oxygen and nitrous oxide by obstructing the patient outlet of the circuit, fully opening the expiratory valve of the circuit and commencing an 8-L/min fresh gas flow of equal parts of oxygen and nitrous oxide. After reminding the patient to take five to eight deep breaths through their mouth (to minimize olfactory sensation) and unobstructing the patient outlet, the anesthetic mask was gently applied, an airtight seal achieved, and the patients respirations audibly counted (6). After loss of response by the patient to a verbal command (“open your eyes, please”) and onset of regular respiration, an IV cannula was inserted by either of the two attendant anesthesiologists. Thereafter, anesthetic drugs were injected to deepen anesthesia, facilitate control of the airway, and maintain anesthesia as appropriate.

Patient demographic data (age, sex, weight, height, ethnicity, and ASA status), history of surgery, route of induction of previous anesthesia, and answers to the questionnaire were recorded, as were the replies of patients who requested that the anesthesiologist do “whatever is considered best.” Analysis of variance, Student's t-test, and χ2 tests, with Bonferroni correction for repeated comparisons, were used to compare demographic data and to test for differences within and between ethnic groups. The χ2 test was used to compare differences of choice overall. Statistical significance was assumed at P < 0.05.

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Results

Sixty-three (12 men and 51 women) African American, 53 (19 men and 34 women) Hispanic, 119 (59 men and 60 women) white, and 5 (2 men and 3 women) Asian adults, aged between 16 and 89 yr old, were audited, yielding a study population of 240 (92 men and 148 women) patients. Within and between ethnic group and gender comparisons revealed no differences with respect to numbers of patients with previous surgical experience or choice of route of induction of anesthesia were revealed. Overall, 212 (88%) patients had undergone surgery previously, which had been induced by a needle in 203 (96%), by mask in 5 (2%), and via an unrecalled route in 4 (2%) patients. IV induction was chosen by 78 (33%) and inhaled induction by 120 (50%) patients, respectively (P < 0.0005). The remaining 42 (17%) patients were undecided (P < 0.0005; IV versus inhaled) and requested that the anesthesiologist do whatever was considered best. Sevoflurane 8% in equal parts of nitrous oxide and oxygen, administered from a primed circle absorber circuit (6), was used successfully in 154 patients. Of these, 120 patients had chosen mask induction, 32 had been undecided and were offered mask induction, and 2 patients had selected IV induction but in whom IV cannulation had proven difficult.

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Discussion

This investigation revealed that the majority of adult Americans presenting to a university teaching hospital for ambulatory surgery chose an inhaled, rather than an IV, induction of anesthesia. These findings are similar to those of an audit of adult Australian women presenting to an Australian university teaching hospital (7).

The reasons for the preferences reported here were not explored and are open to conjecture. It is probable that, during the last millennium, the pungency of ether, chloroform, and other inhaled anesthetics resulted in an unpopularity of inhaled inductions of anesthesia and contributed to the concept popular among anesthesiologists that most adult patients have a dislike of anesthetic masks. In conjunction with the introduction of safe IV anesthetic induction drugs, this aversion may, in turn, have resulted in the preference with both patients and anesthesiologists for the IV induction of anesthesia. The selection of mask induction by 50% of our patients, most of whom were unlikely to have had exposure to pungent inhaled anesthetics, seems to contradict the concept that an aversion to anesthetic masks is prevalent among contemporary adults. Rather, these data seem to suggest that a fear of needle stick is more prevalent in some adult populations, most of whom are likely to have previous experience with injections.

The concept of patient preference and patient-centered medical practice has long been advocated (8) but has only recently impacted anesthetic practice (9–11). However, although the satisfaction of patients with their anesthetic care may be enhanced by seeking their opinion on aspects of their anesthesia care (such as need for night sedation or premedication, choice of local versus general anesthesia, and methods of postoperative pain control), the preferences of patients regarding route of the induction of anesthesia has various safety, manpower, and economic implications. Of these, patient safety is preeminent. An inhaled induction is contraindicated where regurgitation is possible. Accordingly, irrespective of their choice, patients with a history of reflux, achalasia of the esophagus, hiatus hernia, gastroparesis, or diabetic neuropathy are best induced by IV injection with concomitant cricoid pressure. Similarly, in those suspected of having a difficult airway, the necessity to insert an IV cannula before the induction of anesthesia by either route or any attempt to secure the airway supersedes patient aversion to needle stick. More contentious, however, is offering obese patients the option of an inhaled induction. It is regarded as best practice to insert an IV cannula before the induction in these patients, irrespective of their choice. However, venous cannulation is often difficult in obese patients, many of whom also give a history of difficult venepuncture and express an aversion to needle stick. Accordingly, some anesthesiologists may agree to an expressed preference for inhaled induction because the venodilatation produced by inhaled anesthetics usually facilitates IV cannulation after loss of consciousness and avoids the discomfort of multiple attempts at securing IV access while the patient is awake.

It is also desirable for the anesthesiologist conducting inhaled inductions of anesthesia to have an assistant trained in venepuncture and airway management skills. This enables continued maintenance of the airway after the patient has lost consciousness and simultaneous insertion of an IV cannula. Our study was performed in an academic institution where two anesthesiologists (attending and resident) were present during all of the inductions of anesthesia. Where anesthesiologists practice alone, because of manpower or economic restraints, it may be prudent to avoid offering patients the choice of an inhaled induction.

Pertinent, too, to the concept of offering patients this choice are the relative costs of inhaled versus IV induction. Propofol is probably now the most popular IV induction drug for ambulatory surgery in western anesthetic practice (12), and sevoflurane has become increasingly advocated for inhaled induction in adults (4–7). Although comparisons of cost effectiveness are difficult, data do suggest that the costs to loss of consciousness (5) or to insertion of the laryngeal mask (13) are less with sevoflurane than with propofol.

It has long been our belief that minimizing needle stick discomfort is a modality of good patient care (14). It is also our growing belief that heeding the preference of healthy patients regarding their preferred route of induction of anesthesia, aforesaid factors notwithstanding, may enhance the satisfaction of patients with their anesthetic care. Although the induction of anesthesia by inhalation of a volatile anesthetic in the absence of an IV cannula may be contrary to the views of anesthesiologists familiar with the dysrhythmogenic and vagotonic effects of halothane, the remarkably rapid action and stable cardiorespiratory profile of sevoflurane has persuaded the authors that its use for the induction of anesthesia and before venous cannulation in healthy patients is an acceptable technique. Whereas these data derive from a select population presenting to a university teaching hospital, the principle they espouse may be applicable to adult populations at large. It is suggested that, where appropriate, inquiry regarding the preferences of healthy adults regarding their route of induction of anesthesia may be considered at the preoperative visit.

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