Propofol is a short-acting intravenous (i.v.) anaesthetic with an excellent recovery profile . The recent introduction of target-controlled infusion systems gives the further potential of improving both the rapidity and accuracy in achieving and maintaining a desired level of general anaesthesia [2,3]. Remifentanil is a new selective μ-opioid receptor agonist providing intense analgesia of rapid onset and very short duration . General anaesthesia has been reported to delay patient discharge compared with regional anaesthesia techniques [5,6]. However, the newer short-acting anaesthetic drugs such as propofol and remifentanil could improve discharge times after general anaesthesia .
Lidocaine is usually advocated as the local anaesthetic of choice for outpatient spinal anaesthesia because of its short action. However, it has been clearly demonstrated that it is the most important risk factor for transient postoperative neurological symptoms, and the incidence of its undesirable side-effects is particularly unwelcome in outpatients . Mepivacaine has been suggested as an alternative to lidocaine for outpatient spinal anaesthesia but it does not reduce the incidence of transient neurological symptoms [9,10]. For this reason, we routinely use small doses of bupivacaine instead of lidocaine, even in outpatients, to minimize the risk of transient neurological symptoms , and the recovery profile obtained is similar to that reported after lidocaine spinal block [11-13].
Nonetheless, no studies have compared total i.v. anaesthesia with propofol and remifentanil and spinal anaesthesia with low-dose bupivacaine for gynaecological outpatient procedures. We therefore conducted a prospective, randomized study to compare preparation and discharge times, as well as the incidence of side-effects and patient satisfaction after gynaecological outpatient procedures performed using either spinal anaesthesia or total i.v. anaesthesia with propofol and remifentanil.
With Ethics Committee approval and written informed consent, 40 ASA I-II outpatients, aged 18-65 yr, scheduled to undergo hysteroscopic ablation of endometrial neoplasm were studied prospectively. Patients with severe cardiac, pulmonary or renal disease were excluded. The study sample size was calculated to detect a 100 min difference in hospital discharge times between spinal and total i.v. anaesthesia, accepting a two-tailed α-error of 5% and a β-error of 20%  based on a pilot study with 10 patients per group (unpublished data; data from the pilot study were included in the final analysis). According to these calculations, the required study size was 20 patients per group.
No premedication was given. An 18-gauge i.v. cannula was inserted into a large forearm vein and NaCl 0.9% solution, 5 mL kg−1, was given over 15 min. Standard monitoring was used throughout, including non-invasive arterial pressure (Dinamap 1846SX®; Critikon, FL, USA), electrocardiography (Lead II), heart rate, pulse oximetry, as well as the balance between the inflow and outflow of the glycine solution. By use of a sealed envelope technique, patients were then randomly allocated to receive either total i.v. general anaesthesia with propofol and remifentanil (TIVA group, n = 20) or spinal anaesthesia with small doses bupivacaine (spinal group, n = 20).
Spinal anaesthesia was performed with the patient placed in the sitting position by injecting hyperbaric bupivacaine 0.5%, 10 mg (Marcaine Spinal Heavy®; AstraZeneca, Sodertalje, Sweden) through a 25-G Whitacre needle inserted at the L2-3 interspace. Patients were then placed in a supine position. The time from the end of injection to complete loss of pinprick sensation at T10 with a Bromage's score ≥ 2 was recorded as the preparation time.
In all patients receiving the general anaesthesia technique, bispectral index monitoring electrodes (BIS®; Aspect Medical Systems, Natick, MA, USA) were placed before anaesthesia was induced and calibrated on each patient according to the manufacturer's instructions. According to the time to peak effect of remifentanil, the continuous infusion of remifentanil at 0.25 μg kg−1 min−1 was started 5 min before induction of general anaesthesia. General anaesthesia was induced with a target-controlled infusion of propofol (Diprifusor®; AstraZeneca, Milano, Italy) set at 4 μg mL−1. When loss of eyelash reflexes and BIS < 60 were observed, a cuffed oropharyngeal airway was inserted (a size 10 or 11 cuffed oropharyngeal airway was generally used), and the patients' lungs were mechanically ventilated (tidal volume = 8 mL kg−1; respiratory rate = 12 breaths min−1; inspiratory to expiratory ratio 1:2) . General anaesthesia was then maintained by adjusting the target concentration of propofol and the infusion of remifentanil to maintain BIS < 60 with the systolic arterial pressure ranging ±20% from baseline values. The time from starting the remifentanil infusion to having the patient ready for antiseptic skin preparation was recorded as the preparation time. The propofol and remifentanil infusions were stopped when the surgeon removed the hysteroscope (end of the procedure).
Clinically relevant hypotension (decrease of systolic arterial pressure > 30% from baseline) or bradycardia (heart rate decrease below 45 beats min−1) were treated with i.v. boluses of etilephrine 1 mg or atropine 0.5 mg, respectively. The occurrence of haemodynamic untoward events was recorded. All patients received ketoprofen 100 mg i.v. before surgery was completed.
At the end of surgery, patients were transferred to the postanaesthesia care unit (PACU), where the modified Aldrete's score (see Appendix 1)  and the degree of pain assessed with a visual analogue scale (VAS) were recorded every 5 min by a dedicated anaesthesia nurse. If VAS > 30 mm was reported, rescue analgesia was provided with tramadol 100 mg i.v. Patients were discharged from the PACU to the day surgery unit (DSU) when vitals signs were stable for two measurements with a modified Aldrete's score ≥ 9 and VAS < 30 mm. The time of PACU discharge was recorded. Patients were evaluated every 30 min in the DSU by dedicated nurses until ready for discharge to their home. The criteria for home discharge were based on the postanaesthetic discharge scoring system (PADSS) (see Appendix 2). A PADSS ≥ 9 was considered as being ready for home discharge. Recovery of micturation and unassisted ambulation were considered mandatory criteria for home discharge.
Urinary retention was suspected if any patient with clinical evidence of bladder distension reported discomfort and abdominal pain. In these cases, the bladder was drained by temporary catheterization. Urinary retention was defined as the presence of ≥ 100 mL urine . In instances of temporary bladder catheterization, the patient was observed further until spontaneous micturation recovered. If this did not occur and a second catheterization was required, the patient was admitted to the hospital overnight.
Postoperative analgesia consisted of ketoprofen 50 mg orally every 8 h, starting 8 h after the intraoperative i.v. administration. After hospital discharge, tramadol 50 mg orally was available to patients as a rescue analgesia if required. The day after surgery, a postoperative telephone follow-up was carried out by interviewing the patient using a standard questionnaire about the degree of postoperative pain and consumption of rescue tramadol, and the occurrence of nausea, vomiting or other complications after surgery.
A cost comparison was also performed from the perspective of our anaesthesia department. This was based on the actual acquisition costs of all drugs, including waste, administered by the anaesthesia staff from the beginning of anaesthesia to discharge from the hospital; the actual acquisition costs of disposable material used throughout the study; and costs of the anaesthesia and nurse staff.
Statistical analysis was performed using the program Systat 7.0® (SPSS Inc., Chicago, IL, USA). Data distribution was tested for normality using the Kolmogorov-Smirnov test. Continuous variables were evaluated with the U-test. Analysis of variance for repeated measures was used to analyse changes over time. Ordinal data were analysed using the contingency table analysis with Fisher's exact test. P < 0.05 was considered as significant. Continuous variables are presented as median (range). Dichotomous data are presented as numbers (%).
No differences in the anthropometric parameters and duration of surgical procedure were reported between the two groups (Table 1). The median (range) preparation time was 7 (7-10) min in the TIVA group and 11 (7-21) min in the spinal group (P = 0.00005). Clinically relevant hypotension, requiring the administration of vasoconstrictors, was observed in three patients in the TIVA group (15%) and in one patient (5%) in the spinal group (P = 0.60); bradycardia was reported in three patients in the TIVA group only (15%) (P = 0.23).
The time from admission to the PACU to discharge to the DSU was 10 (10-15) min in the spinal group and 10 (10-15) min in the TIVA group (P = 0.87). Twelve patients in the TIVA group (60%) required rescue analgesia with tramadol during their stay in the PACU compared with only two patients in the spinal group (10%) (P = 0.002). Three patients in the TIVA group (15%) and one patient in the spinal group (5%) complained of nausea requiring metoclopramide 10 mg i.v. Complete resolution of symptoms was observed in all cases.
No urinary retention was observed in patients in the TIVA group, while six patients in the spinal group (30%) required temporary bladder catheterization (P = 0.02). Nonetheless, bladder function recovered in all patients and no overnight admission was required because of urinary retention in either group. The median time for home discharge was 156 min in the TIVA group (25th-75th percentiles: 117-197 min) and 296 min (25th-75th percentiles: 240-382 min) in the spinal group (P = 0.0005). Figure 1 shows the log-rank curves for the fulfilment of home discharge criteria.
Pain control, assessed at the 24 h follow-up, was similar in the two groups. Twelve patients in the spinal group (60%) and seven patients in the TIVA group (35%) needed rescue analgesia with tramadol during the first day after surgery (P = 0.20). One patient in the spinal group complained of mild postdural puncture headache at follow-up. This patient was followed on a daily basis, but she was not admitted to hospital. Complete resolution occurred within 3 days after surgery with conventional therapy. Acceptance of the anaesthesia technique was good in all TIVA patients (100%), while five patients in the spinal group (25%) would prefer a different anaesthesia technique if operated on again for the same procedure (P = 0.04). Interestingly, the five patients with poor acceptance of the anaesthesia technique also had delayed recovery of bladder function requiring bladder catheterization.
Table 2 summarizes the costs. Although minor differences were observed in the cost of drugs and disposables, or in costs related to the day stay unit, no differences were reported in the total costs.
This is the first report comparing the costs and benefits of spinal- to TIVA-related gynaecological outpatient procedures using propofol and remifentanil. Results from this prospective, randomized study demonstrated that total i.v. anaesthesia with short-acting anaesthetic drugs, e.g. propofol and remifentanil, provides a shorter preparation time and earlier discharge from the DSU compared with spinal anaesthesia with small doses of bupivacaine.
A major criticism of the study design could be the use of the long-acting local anaesthetic bupivacaine instead of shorter-acting drugs such as lidocaine or mepivacaine. The reason for the choice was based mainly on the potential for undesirable neurological complications produced by spinal lidocaine, which are even more frequent in outpatients placed in the lithotomy position . Mepivacaine, an amide local anaesthetic with an anaesthetic profile similar to lidocaine, has been recommended as a good alternative to lidocaine for subarachnoid anaesthesia in short surgical procedures . Nevertheless, transient neurological symptoms have been reported both with isobaric and hyperbaric solutions of mepivacaine [9,10]. On the other hand, it has been clearly demonstrated that the use of small doses of bupivacaine provides a recovery profile from spinal block that is suitable for outpatient purposes [11,12,19], and similar to that reported with 50-60 mg intrathecal lidocaine [13,20]. Ben-David and colleagues  reported a faster recovery profile of spinal block when the dose of bupivacaine was reduced to 5 mg; however, this was also associated with an unacceptable increase in the failure rate.
Interestingly, a larger proportion of patients required rescue analgesics after PACU admission in the TIVA group than in the spinal group. This finding points to the need for adequate planning and the implementation of pain management before the end of the procedure when remifentanil is used during surgery.
Pavlin and colleagues  reported that gynaecological procedures have a low risk of urinary retention and suggested that these patients should not benefit from being required to void before discharge. However, in the present investigation, home discharge criteria included the recovery of both bladder and neurological function because of the use of spinal anaesthesia . In fact, although urinary retention never necessitated overnight hospitalization, 30% of patients in the spinal group had urinary retention requiring temporary bladder catheterization. This undesirable side-effect not only exposed the patients to an increased risk of infection, but also was associated with a poorer acceptance of this technique of spinal anaesthesia.
When the related costs are considered, the present investigation failed to demonstrate any significant effects on the total costs, even if minor differences were observed in the costs of drugs and the duration of stay in the day surgery unit. In the present investigation, criteria for PACU discharge were mainly based on the modified Aldrete's score, while it has been demonstrated that this scoring system may be too narrow to determine adequately the eligibility for PACU discharge of outpatients. White and colleagues  developed a new scoring system specifically to evaluate patient eligibility for discharge from the PACU in order to bypass the PACU after outpatient procedures. Reducing admission to the PACU is recognized as a major factor in the reduction of costs of outpatient procedures ; further studies should be conducted to evaluate better the effects of bypassing the PACU on anaesthesia-related costs after outpatient gynaecological procedures performed with these two techniques of anaesthesia.
One case of postdural puncture headache was reported in the population studied. This complication was of mild severity and resolved uneventfully without hospital admission. However, the small sample size of the study prevents us from drawing any conclusion about this rare complication.
In conclusion, this prospective, randomized study demonstrated that accurate titration of short-acting i.v. anaesthetic drugs, such as propofol and remifentanil, results in shorter preparation time and earlier home discharge after outpatient gynaecological procedures. There is better patient acceptance and no increased costs compared with the method of spinal anaesthesia with hyperbaric bupivacaine 10 mg.
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The Modified Aldrete Scoring System for determining when patients are ready for discharge from the PACU. A score ≥ 9 was considered necessary for discharge from the postanaesthesia care unit. TABLE 1
Postanaesthetic discharge scores. TABLE 2