Influence of motivation of care providers on the incidence of postoperative hypoxaemia in the recovery room

Incidence of Artifacts and Deviating Values in Research Data Obtained from an Anesthesia Information Management System in Children

BACKGROUND

Vital parameter data collected in anesthesia information management systems are often used for clinical research. The validity of this type of research is dependent on the number of artifacts.

METHODS

In this prospective observational cohort study, the incidence of artifacts in anesthesia information management system data was investigated in children undergoing anesthesia for noncardiac procedures. Secondary outcomes included the incidence of artifacts among deviating and nondeviating values, among the anesthesia phases, and among different anesthetic techniques.

RESULTS

We included 136 anesthetics representing 10,236 min of anesthesia time. The incidence of artifacts was 0.5% for heart rate (95% CI: 0.4 to 0.7%), 1.3% for oxygen saturation (1.1 to 1.5%), 7.5% for end-tidal carbon dioxide (6.9 to 8.0%), 5.0% for noninvasive blood pressure (4.0 to 6.0%), and 7.3% for invasive blood pressure (5.9 to 8.8%). The incidence of artifacts among deviating values was 3.1% for heart rate (2.1 to 4.4%), 10.8% for oxygen saturation (7.6 to 14.8%), 14.1% for end-tidal carbon dioxide (13.0 to 15.2%), 14.4% for noninvasive blood pressure (10.3 to 19.4%), and 38.4% for invasive blood pressure (30.3 to 47.1%).

CONCLUSIONS

Not all values in anesthesia information management systems are valid. The incidence of artifacts stored in the present pediatric anesthesia practice was low for heart rate and oxygen saturation, whereas noninvasive and invasive blood pressure and end-tidal carbon dioxide had higher artifact incidences. Deviating values are more often artifacts than values in a normal range, and artifacts are associated with the phase of anesthesia and anesthetic technique. Development of (automatic) data validation systems or solutions to deal with artifacts in data is warranted.

Pulse oximetry for perioperative monitoring

BACKGROUND

This is an update of a review last published in Issue 9, 2009, of The Cochrane Library. Pulse oximetry is used extensively in the perioperative period and might improve patient outcomes by enabling early diagnosis and, consequently, correction of perioperative events that might cause postoperative complications or even death. Only a few randomized clinical trials of pulse oximetry during anaesthesia and in the recovery room have been performed that describe perioperative hypoxaemic events, postoperative cardiopulmonary complications and cognitive dysfunction.

OBJECTIVES

To study the use of perioperative monitoring with pulse oximetry to clearly identify adverse outcomes that might be prevented or improved by its use.The following hypotheses were tested.1. Use of pulse oximetry is associated with improvement in the detection and treatment of hypoxaemia.2. Early detection and treatment of hypoxaemia reduce morbidity and mortality in the perioperative period.3. Use of pulse oximetry per se reduces morbidity and mortality in the perioperative period.4. Use of pulse oximetry reduces unplanned respiratory admissions to the intensive care unit (ICU), decreases the length of ICU readmission or both.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2013, Issue 5), MEDLINE (1966 to June 2013), EMBASE (1980 to June 2013), CINAHL (1982 to June 2013), ISI Web of Science (1956 to June 2013), LILACS (1982 to June 2013) and databases of ongoing trials; we also checked the reference lists of trials and review articles. The original search was performed in January 2005, and a previous update was performed in May 2009.

SELECTION CRITERIA

We included all controlled trials that randomly assigned participants to pulse oximetry or no pulse oximetry during the perioperative period.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed data in relation to events detectable by pulse oximetry, any serious complications that occurred during anaesthesia or in the postoperative period and intraoperative or postoperative mortality.

MAIN RESULTS

The last update of the review identified five eligible studies. The updated search found one study that is awaiting assessment but no additional eligible studies. We considered studies with data from a total of 22,992 participants that were eligible for analysis. These studies gave insufficient detail on the methods used for randomization and allocation concealment. It was impossible for study personnel to be blinded to participant allocation in the study, as they needed to be able to respond to oximetry readings. Appropriate steps were taken to minimize detection bias for hypoxaemia and complication outcomes. Results indicated that hypoxaemia was reduced in the pulse oximetry group, both in the operating theatre and in the recovery room. During observation in the recovery room, the incidence of hypoxaemia in the pulse oximetry group was 1.5 to three times less. Postoperative cognitive function was independent of perioperative monitoring with pulse oximetry. A single study in general surgery showed that postoperative complications occurred in 10% of participants in the oximetry group and in 9.4% of those in the control group. No statistically significant differences in cardiovascular, respiratory, neurological or infectious complications were detected in the two groups. The duration of hospital stay was a median of five days in both groups, and equal numbers of in-hospital deaths were reported in the two groups. Continuous pulse oximetry has the potential to increase vigilance and decrease pulmonary complications after cardiothoracic surgery; however, routine continuous monitoring did not reduce transfer to an ICU and did not decrease overall mortality.

AUTHORS' CONCLUSIONS

These studies confirmed that pulse oximetry can detect hypoxaemia and related events. However, we found no evidence that pulse oximetry affects the outcome of anaesthesia for patients. The conflicting subjective and objective study results, despite an intense methodical collection of data from a relatively large general surgery population, indicate that the value of perioperative monitoring with pulse oximetry is questionable in relation to improved reliable outcomes, effectiveness and efficiency. Routine continuous pulse oximetry monitoring did not reduce transfer to the ICU and did not decrease mortality, and it is unclear whether any real benefit was derived from the application of this technology for patients recovering from cardiothoracic surgery in a general care area.

Why we should be wary of single-center trials

OBJECTIVES

To highlight the limitations of single-center trials in critical care, using prominent examples from the recent literature; to explore possible reasons for discrepancies between these studies and subsequent multicenter effectiveness trials; and to suggest how the evidence from single-center trials might be used more appropriately in clinical practice.

STUDY SELECTION

Topical and illustrative examples of the concepts discussed including trials of patient positioning, the use of steroids for acute respiratory distress syndrome, the dose of hemofiltration, the control of glycemia, and the targets of resuscitation in sepsis. DATA SYNOPSIS: Many positive single-center trials have been contradicted when tested in other settings and, in one case, the subsequent definitive multicentered trial has found a previously recommended intervention associated with active harm. Problems inherent in the nature of single-center studies make recommendations based on their results ill advised. Single-center studies frequently either lack the scientific rigor or external validity required to support widespread changes in practice, and their premature incorporation into guidelines may make the conduct of definitive studies more difficult.

CONCLUSIONS

We recommend that practice guidelines should rarely, if ever, be based on evidence from single-center trials. Physicians should apply the findings of single-center trials only after careful evaluation of their methodology, and in particular after comparing the context of the trial with their own situation.

Pulse oximetry for perioperative monitoring

BACKGROUND

Pulse oximetry is extensively used in the perioperative period and might improve patient outcomes by enabling an early diagnosis and, consequently, correction of perioperative events that might cause postoperative complications or even death. Only a few randomized clinical trials of pulse oximetry during anaesthesia and in the recovery room have been performed that describe perioperative hypoxaemic events, postoperative cardiopulmonary complications, and cognitive dysfunction.

OBJECTIVES

The objective of this review was to assess the effects of perioperative monitoring with pulse oximetry and to clearly identify the adverse outcomes that might be prevented or improved by the use of pulse oximetry.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2009, Issue 2), MEDLINE (1966 to May 2009), EMBASE (1980 to May 2009), CINAHL (1982 to May 2009), ISI Web of Science (1956 to May 2009), LILACS (1982 to May 2009), and databases of ongoing trials; and checked the reference lists of trials and review articles.

SELECTION CRITERIA

We included all controlled trials that randomized patients to either pulse oximetry or no pulse oximetry during the perioperative period.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed data in relation to events detectable by pulse oximetry, any serious complications that occurred during anaesthesia or in the postoperative period, and intra- or postoperative mortality.

MAIN RESULTS

Searching identified five reports. We considered the studies with data from a total of 22,992 patients that were eligible for analysis. Results indicated that hypoxaemia was reduced in the pulse oximetry group, both in the operating theatre and in the recovery room. During observation in the recovery room, the incidence of hypoxaemia in the pulse oximetry group was 1.5 to three times less. Postoperative cognitive function was independent of perioperative monitoring with pulse oximetry. The one study in general surgery showed that postoperative complications occurred in 10% of the patients in the oximetry group and in 9.4% in the control group. No statistically significant differences were detected in cardiovascular, respiratory, neurologic, or infectious complications in the two groups. The duration of hospital stay was a median of five days in both groups, and an equal number of in-hospital deaths was registered in the two groups. Continuous pulse oximetry has the potential to increase vigilance and decrease pulmonary complications after cardiothoracic surgery, however routine continuous monitoring did not reduce transfer to an intensive care unit (ICU) or overall mortality.

AUTHORS' CONCLUSIONS

The studies confirmed that pulse oximetry can detect hypoxaemia and related events. However, we have found no evidence that pulse oximetry affects the outcome of anaesthesia for patients. The conflicting subjective and objective results of the studies, despite an intense methodical collection of data from a relatively large general surgery population, indicate that the value of perioperative monitoring with pulse oximetry is questionable in relation to improved reliable outcomes, effectiveness, and efficiency. Routine continuous pulse oximetry monitoring did not reduce either transfer to ICU or mortality, and it is unclear if there is any real benefit from the application of this technology in patients who are recovering from cardiothoracic surgery in a general care area.

Dependence and caring in clinical communication: the relevance of attachment and other theories

OBJECTIVE

Clinical relationships are usually asymmetric, being defined by patients' dependence and practitioners' care. Our aims are to: (i) identify literature that can contribute to theory for researching and teaching clinical communication from this perspective; (ii) highlight where theoretical development is needed; and (iii) test the utility of the emerging theory by identifying whether it leads to implications for educational practice.

METHODS

Selective and critical review of research concerned with dependence and caring in clinical and non-clinical relationships.

RESULTS

Attachment theory helps to understand patients' need to seek safety in relationships with expert and authoritative practitioners but is of limited help in understanding practitioners' caring. Different theories that formulate practitioners' care as altruistic, rewarded by personal connection or as a contract indicate the potential importance of practitioners' emotions, values and sense of role in understanding their clinical communication.

CONCLUSION

Extending the theoretical grounding of clinical communication can accommodate patients' dependence and practitioners' caring without return to medical paternalism.

PRACTICE IMPLICATIONS

A broader theoretical base will help educators to address the inherent subjectivity of clinical relationships, and researchers to distinguish scientific questions about how patients and clinicians are from normative questions about how they should be.

Pulse oximetry for perioperative monitoring: systematic review of randomized, controlled trials

Monitoring with pulse oximetry might improve patient outcome by enabling an early diagnosis and, consequently, correction of perioperative events that might otherwise cause postoperative complications or even death. The aim of the study was to clarify the effect of perioperative monitoring with pulse oximetry and to identify the adverse outcomes that might be prevented or improved by its use. Trials were identified by computerized searches of the Cochrane Library, MEDLINE, EMBASE, and by checking the reference lists of trials and review articles. All controlled trials that randomized patients to either pulse oximetry or no pulse oximetry during the perioperative period, including in the operating and recovery room, were included in the study. The search identified six reports. Of these 6 reports, 4 studies with data from 21,773 patients were considered eligible for analysis. Two studies specifically addressed the outcomes in question; both found no effect on the rate of postoperative complications using perioperative pulse oximetry. Hypoxemia was reduced in the pulse oximetry group both in the operating room and in the recovery room. During observation in the recovery room, the incidence of hypoxemia in the pulse oximetry group was 1.5-3 times less. There were postoperative complications in 10% of the patients in the oximetry group and in 9.4% in the control group. The duration of hospital stay was a median of 5 days in both groups, and an equal number of in-hospital deaths was registered in both groups. The studies confirmed that pulse oximetry could detect hypoxemia and related events. However, given the relatively small number of patients studied and the rare events being sought, the studies were not able to show an improvement in various outcomes.

Pulse oximetry for perioperative monitoring

BACKGROUND

Monitoring with pulse oximetry might improve patient outcome by enabling an early diagnosis and consequently, correction of perioperative events that might cause postoperative complications or even death. Only a few randomized clinical trials of pulse oximetry have been performed during anaesthesia, and in the recovery room which describe perioperative hypoxaemic events, postoperative cardiopulmonary complications and cognitive dysfunction.

OBJECTIVES

The objective of this review was to assess the effect of perioperative monitoring with pulse oximetry and to clearly identify the adverse outcomes that might be prevented or improved by the use of pulse oximetry.

SEARCH STRATEGY

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library 2003, issue 1) MEDLINE (1966 to January 2003), EMBASE (1980 to January 2003), and by checking the reference lists of trials and review articles.

SELECTION CRITERIA

All controlled trials that randomized patients to either pulse oximetry or no pulse oximetry during the perioperative period, including the operating and recovery room.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed data in relation to events detectable by pulse oximetry, any serious complications that occurred during anaesthesia or in the postoperative period, intra- or postoperative mortality, and duration of recovery or intensive care stay. Formal statistical synthesis of individual trials was not performed in view of the variety of outcomes studied.

MAIN RESULTS

Searching identified six reports. Four studies with data from a total of 21,773 patients were considered eligible for analysis. Only two studies specifically addressed the outcomes in question, both found no evidence of an effect on the rate of postoperative complications using perioperative pulse oximetry. Two studies used hypoxaemia detectable by pulse oximetry to assess the value of perioperative monitoring, although outcomes were not given. It was found that hypoxaemia was reduced in the pulse oximetry group both in the operating theatre and in the recovery room. During observation in the recovery room, the incidence of hypoxaemia in the pulse oximetry group was 1.5-3 times less. The postoperative cognitive function using the Wechsler memory scale and continuous reaction time was independent of perioperative monitoring with pulse oximetry. The other study showed that postoperative complications occurred in 10% of the patients in the oximetry group and in 9.4% in the control group. No statistically significant differences were detected in cardiovascular, respiratory, neurologic, or infectious complications in the two groups. The duration of hospital stay was a median of five days in both groups, and an equal number of in-hospital deaths was registered in the two groups.

REVIEWER'S CONCLUSIONS

The studies confirmed that pulse oximetry can detect hypoxaemia and related events. However, we have found no evidence that pulse oximetry affects the outcome of anaesthesia. The conflicting subjective and objective results of the studies, despite an intense, methodical collection of data from a relatively large population, indicate that the value of perioperative monitoring with pulse oximetry is questionable in relation to improved reliable outcomes, effectiveness and efficiency.

More reliable oximetry reduces the frequency of arterial blood gas analyses and hastens oxygen weaning after cardiac surgery: a prospective, randomized trial of the clinical impact of a new technology

OBJECTIVE

Evaluation of the impact on clinical care of improved, innovative oximetry technology.

DESIGN

Randomized, prospective trial.

SETTING

Postcardiac surgery intensive care unit in a major teaching hospital.

PATIENTS

A total of 86 patients after undergoing coronary artery bypass surgery.

INTERVENTIONS

All patients were monitored with two oximeters, one employing conventional oximetry (conventional pulse oximeter, CPO) and one using an improved innovative technology (innovative pulse oximeter, IPO), on different fingers of the same hand. The outputs from both devices were collected continuously by computer, but only one device was randomly selected and displayed for clinicians.

MEASUREMENTS AND MAIN RESULTS

The amount and percentage of nonfunctional monitoring time was collected and found to be much greater for the CPO than the IPO (8.7% +/- 16.4% for CPO vs. 1.2% +/- 3.3% for IPO, p =.000256). Time to extubation was not different between the two groups (634 +/- 328 mins for IPO vs. 706 +/- 459 mins for CPO). Clinicians managing patients with the more reliable IPO weaned patients faster to an FIO2 of 0.40 (176 +/- 111 mins for IPO vs. 348 +/- 425 mins for CPO, p =.0125), obtained fewer arterial blood gas measurements (2.7 +/- 1.2 for IPO vs. 4.1 +/- 1.6 for CPO, p =.000015), and made the same number of ventilator changes during this weaning process (2.9 +/- 1.2 for IPO vs. 2.9 +/- 1.7 for CPO).

CONCLUSIONS

Provision of more reliable oximetry allows caregivers to act in a more efficient and cost-effective manner in regard to oxygen weaning and use of arterial blood gas measurements. Investigating the effect of a monitor on the process of care, rather than simply its accuracy and precision, is a useful, relevant paradigm for evaluating the value and impact of a new technology.

Occlusal stabilization appliances. Evidence of their efficacy

BACKGROUND

There is substantial controversy regarding the value of occlusal appliances for managing temporomandibular joint disorders. This article specifically assesses whether the evidence is sufficient to judge occlusal appliances as being efficacious for the management of localized masticatory myalgia, arthralgia or both. A major confounder is that few studies have measured or evaluated whether subjects had strong, ongoing parafunctional activity (such as clenching or grinding) and whether appliances influenced this behavior.

LITERATURE REVIEWED

The authors evaluated four placebo-controlled studies, several randomized wait-list controlled studies and several random-assignment treatment-comparison studies. Data from the wait-list condition studies vs. those from the occlusal appliance condition studies consistently suggested that the latter treatment's effect on patient symptom level is far more than that of no treatment on a wait-list group's condition. In contrast, the studies on placebo-controlled vs. occlusal appliance studies yielded a mix of data: two showed a positive benefit of occlusal vs. nonoccluding appliances, and two showed a null effect or no difference.

CONCLUSIONS

Considering all of the available data (pro and con), the authors conclude that the use of occlusal appliances in managing localized masticatory myalgia, arthralgia or both is sufficiently supported by evidence in the literature.

CLINICAL IMPLICATIONS

The mechanism of action by which occlusal appliances affect localized myalgia and arthralgia probably is behavioral modification of jaw clenching. However, if the behavior continues unabated, even the best splint will not work.

False alarms and sensitivity of conventional pulse oximetry versus the Masimo SET technology in the pediatric postanesthesia care unit

We compared the incidence and duration of false alarms (FA)and the sensitivity of conventional pulse oximetry (CPO) with Masimo Signal Extraction Technology (Masimo SET; Masimo Corporation, Irvine, CA) in children in the postanesthesia care unit. Disposable oximeter sensors were placed on separate digits of one extremity. Computerized acquisition of synchronous data included electrocardiograph heart rate, SpO(2), and pulse rate via CPO and Masimo SET. Patient motion, respiratory, and other events were simultaneously documented. SpO(2) tracings conflicting with clinical observations and/or documented events were considered false. These were defined as 1) Data dropout, complete interruption in SpO(2) data; 2) False negative, failure to detect SpO(2) </= 90% detected by another device or based on observation/intervention; 3) FA, SpO(2) </= 90% considered artifactual; and 4) True alarm (TA), SpO(2) </= 90% considered valid. Seventy-five children were monitored for 35 +/- 22 min/patient (42 h total). There were 27 TAs, all of which were identified by Masimo SET and only 16 (59%) were identified by CPO (P < 0.05). There was twice the number of FAs with CPO (10 vs 4 Masimo SET; P < 0.05). The incidence and duration of data dropouts were similar between Masimo SET and CPO. Masimo SET reduced the incidence and duration of FAs and identified a more frequent incidence of TAs compared with CPO.

IMPLICATIONS

Pulse oximetry that incorporates Masimo Signal Extraction Technology (Masimo Corporation, Irvine, CA) may offer an advantage over conventional pulse oximetry by reducing the incidence of false alarms while identifying a higher number of true alarms in children in the postanesthesia care unit.

Advanced pulse oximeter signal processing technology compared to simple averaging. II. Effect on frequency of alarms in the postanesthesia care unit

STUDY OBJECTIVE

To determine the effect of a new pulse oximeter (Nellcor Symphony N-3000, Pleasanton, CA) with signal processing technique (Oxismart) on the incidence of false alarms in the postanesthesia care unit (PACU).

DESIGN

Prospective study.

SETTING

Nonuniversity hospital.

PATIENTS

603 consecutive ASA physical status I, II, and III patients recovering from general or regional anesthesia in the PACU.

INTERVENTIONS

We compared the number of alarms produced by a recently developed "third"-generation pulse oximeter (Nellcor Symphony N-3000) with Oxismart signal processing technique and a conventional pulse oximeter (Criticare 504, Waukesha, WI). Patients were randomly assigned to either a Nellcor pulse oximeter or a Criticare with the signal averaging time set at either 12 or 21 seconds. For each patient the number of false (artifact) alarms was counted.

MEASUREMENTS AND MAIN RESULTS

The Nellcor generated one false alarm in 199 patients and 36 (in 31 patients) "loss of pulse" alarms. The conventional pulse oximeter with the averaging time set at 12 seconds generated a total of 32 false alarms in 17 of 197 patients [compared with the Nellcor, relative risk (RR) 0.06, confidence interval (CI) 0.01 to 0.25] and a total of 172 "loss of pulse" alarms in 79 patients (RR 0.39, CI 0.28 to 0.55). The conventional pulse oximeter with the averaging time set at 21 seconds generated 12 false alarms in 11 of 207 patients (compared with the Nellcor, RR 0.09, CI 0.02 to 0.48) and a total of 204 "loss of pulse" alarms in 81 patients (RR 0.40, CI 0.28 to 0.56). The lower incidence of false alarms of the conventional pulse oximeter with the longest averaging time compared with the shorter averaging time did not reach statistical significance (false alarms RR 0.62, CI 0.3 to 1.27; "loss of pulse" alarms RR 0.98, CI 0.77 to 1.3).

CONCLUSIONS

To date, this is the first report of a pulse oximeter that produced almost no false alarms in the PACU.

Continuous pulse oximetry in the general surgical ward: Nellcor N-200 versus Nellcor N-3000

New measurement principles in pulse oximetry have been introduced to decrease the incidence of false movement alarms. Experimental studies have shown that the new Nellcor Symphony N-3000 may reduce the incidence of false alarms when monitoring during different activities. We compared the Nellcor Symphony N-3000 with the Nellcor N-200 pulse oximeter, when monitoring patients in the general surgical ward. Twenty-two patients were monitored during unrestricted ward activities for a total of 275 h with a N-3000 and a N-200 pulse oximeter simultaneously. Data were analysed for lack of concordance between the two pulse oximeters with respect to frequency of registered hypoxaemic episodes and thus the amount of time spent in the alarm state. The median number of desaturation episodes with the N-200 was 18 (range 0-511) compared with four (range 0-476) with the N-3000 (p < 0.0001). The median number of drop-outs (loss of signal) was 13 (range 1-46) with the N-200 compared with nine (2-41) with the N-3000 (p = 0.06). The N-200 registered saturation values of 85% or below for 23% of the observation time compared with 6% of the observation time with the N-3000 pulse oximeter (p < 0.0001). The different working principles of the two generations of oximeters were reflected in the present results derived from a clinical setting. The Nellcor Symphony N-3000 may offer an advantage compared with the Nellcor N-200, because of the reduced frequency of alarms and total time in alarm when monitoring patients in the general surgical ward.

Patient-controlled versus staff-controlled analgesia with pethidine after allogeneic bone marrow transplantation

Patients treated by allogeneic bone marrow transplantation (aBMT) suffer prolonged oropharyngeal mucositis pain. The aim of this study was to prospectively compare patient-controlled analgesia (PCA) with an established regimen of staff-controlled analgesia using pethidine (meperidine). Twenty patients undergoing aBMT for haematologic neoplasias or malignant lymphomas randomly received pethidine intravenously either continuously plus supplemental bolus doses on request through the transplant unit staff or by PCA. Pain intensity was assessed by patient self report using a visual analogue scale (VAS) and daily pethidine intake was documented. In addition, the pethidine consumption of 20 aBMT-patients receiving staff-controlled analgesia prior to initiation of the study, but not reporting pain, was compared retrospectively with that of patients receiving the same analgesia regimen under study conditions. PCA significantly diminished both pethidine consumption and pain intensity compared with staff-controlled analgesia. The maximum pethidine intake was 440.1 +/- 111.8 mg/24 h in the patient-controlled and 640.9 +/- 128.9 mg/24 h in the staff-controlled analgesia group (mean +/- 95% CI). Mean pain scores remained under 50% but reached 70% in the staff-controlled analgesia group. Pethidine dosage by staff-controlled analgesia increased under study conditions, suggesting that mere pain-assessment and a 'competing' analgesic method motivated the BMT-unit staff to administer higher pethidine doses. This observation is discussed as a possible Hawthorne effect. Previous studies using morphine demonstrated that PCA diminishes opioid requirement compared to continuous or staff-controlled application in bone marrow recipients. In contrast to these studies, PCA additionally improved pain relief in the present investigation.