Single-patient randomized clinical trial. Opiates for intractable dyspnea

Respiratory adverse effects of opioids for breathlessness: a systematic review and meta-analysis

Previous studies have shown that opioids can reduce chronic breathlessness in advanced disease. However, physicians remain reluctant to prescribe opioids for these patients, commonly due to fear of respiratory adverse effects. The aim of this study was to systematically review reported respiratory adverse effects of opioids in patients with advanced disease and chronic breathlessness.PubMed, Embase, the Cochrane Central Register of Controlled Trials, CINAHL, ClinicalTrials.gov and the reference lists of relevant systematic reviews were searched. Two independent researchers screened against predefined inclusion criteria and extracted data. Meta-analysis was conducted where possible.We included 63 out of 1990 articles, describing 67 studies. Meta-analysis showed an increase in carbon dioxide tension (0.27 kPa, 95% CI 0.08-0.45 kPa,) and no significant change in oxygen tension and oxygen saturation (both p>0.05). Nonserious respiratory depression (definition variable/not stated) was described in four out of 1064 patients. One cancer patient pretreated with morphine for pain needed temporary respiratory support following nebulised morphine for breathlessness (single case study).We found no evidence of significant or clinically relevant respiratory adverse effects of opioids for chronic breathlessness. Heterogeneity of design and study population, and low study quality are limitations. Larger studies designed to detect respiratory adverse effects are needed.

A comparison of four methods for the analysis of N-of-1 trials

OBJECTIVE

To provide a practical guidance for the analysis of N-of-1 trials by comparing four commonly used models.

METHODS

The four models, paired t-test, mixed effects model of difference, mixed effects model and meta-analysis of summary data were compared using a simulation study. The assumed 3-cycles and 4-cycles N-of-1 trials were set with sample sizes of 1, 3, 5, 10, 20 and 30 respectively under normally distributed assumption. The data were generated based on variance-covariance matrix under the assumption of (i) compound symmetry structure or first-order autoregressive structure, and (ii) no carryover effect or 20% carryover effect. Type I error, power, bias (mean error), and mean square error (MSE) of effect differences between two groups were used to evaluate the performance of the four models.

RESULTS

The results from the 3-cycles and 4-cycles N-of-1 trials were comparable with respect to type I error, power, bias and MSE. Paired t-test yielded type I error near to the nominal level, higher power, comparable bias and small MSE, whether there was carryover effect or not. Compared with paired t-test, mixed effects model produced similar size of type I error, smaller bias, but lower power and bigger MSE. Mixed effects model of difference and meta-analysis of summary data yielded type I error far from the nominal level, low power, and large bias and MSE irrespective of the presence or absence of carryover effect.

CONCLUSION

We recommended paired t-test to be used for normally distributed data of N-of-1 trials because of its optimal statistical performance. In the presence of carryover effects, mixed effects model could be used as an alternative.

WITHDRAWN: Opioids for the palliation of breathlessness in advanced disease and terminal illness

BACKGROUND

Breathlessness is a common symptom in people with advanced disease. The most effective treatments are aimed at treating the underlying cause of the breathlessness but this may not be possible and symptomatic treatment is often necessary. Strategies for the symptomatic treatment of breathlessness have never been systematically evaluated. Opioids are commonly used to treat breathlessness: the mechanisms underlying their effectiveness are not completely clear and there have been few good-sized trials in this area.

OBJECTIVES

To determine the effectiveness of opioid drugs given by any route in relieving the symptom of breathlessness in patients who are being treated palliatively.

SEARCH METHODS

An electronic search was carried out of Medline, Embase, CINAHL, T he Cochrane L ibrary, Dissertation Abstracts, Cancercd and SIGLE. Review articles and reference lists of retrieved articles were hand searched. Date of most recent search: May 1999.

SELECTION CRITERIA

Randomised double-blind, controlled trials comparing the use of any opioid drug against placebo for the relief of breathlessness were included. Patients with any illness suffering from breathlessness were included and the intervention was any opioid, given by any route, in any dose.

DATA COLLECTION AND ANALYSIS

Studies identified by the search were imported into a reference manager database. The full texts of the relevant studies were retrieved and data were independently extracted by two review authors. Studies were quality scored according to the Oxford Quality scale. The primary outcome measure used was breathlessness and the secondary outcome measure was exercise tolerance. Studies were divided into non-nebulised and nebulised and were analysed both separately and together. A qualitative analysis was carried out of adverse effects of opioids. Where appropriate, meta-analysis was carried out.

MAIN RESULTS

Eighteen studies were identified of which nine involved the non-nebulised route of administration and nine the nebulised route. A small but statistically significant positive effect of opioids was seen on breathlessness in the analysis of studies using non-nebulised opioids. There was no statistically significant positive effect seen for exercise tolerance in either group of studies or for breathlessness in the studies using nebulised opioids.

AUTHORS' CONCLUSIONS

There is evidence to support the use of oral or parenteral opioids to palliate breathlessness although numbers of patients involved in the studies were small. No evidence was found to support the use of nebulised opioids. Further research with larger numbers of patients, using standardised protocols and with quality of life measures is needed.

Use of the single subject design for practice based primary care research

The use of a single subject research design is proposed for practice based primary care research. An overview of the rationale of the design, an introduction to the methodology, strengths, limitations, a sample of recent literature citations, a working example, and possible clinical applications are presented.

Randomised, double blind, placebo controlled crossover trial of sustained release morphine for the management of refractory dyspnoea

OBJECTIVE

To determine the efficacy of oral morphine in relieving the sensation of breathlessness in patients in whom the underlying aetiology is maximally treated.

DESIGN

Randomised, double blind, placebo controlled crossover study.

SETTING

Four outpatient clinics at a hospital in South Australia.

PARTICIPANTS

48 participants who had not previously been treated with opioids (mean age 76, SD 5) with predominantly chronic obstructive pulmonary disease (42, 88%) were randomised to four days of 20 mg oral morphine with sustained release followed by four days of identically formulated placebo, or vice versa. Laxatives were provided as needed.

MAIN OUTCOME MEASURES

Dyspnoea in the morning and evening as shown on a 100 mm visual analogue scale, quality of sleep, wellbeing, performance on physical exertion, and side effects as measured at the end of the four day treatment period.

RESULTS

38 participants completed the study; three withdrew because of definite and two because of possible side effects of morphine (nausea, vomiting, and sedation). Participants reported significantly different dyspnoea scores when treated with morphine: an improvement of 6.6 mm (95% confidence interval 1.6 mm to 11.6 mm) in the morning and of 9.5 mm (3.0 mm to 16.1 mm) in the evening (P = 0.011 and P = 0.006, respectively). During the period in which they were taking morphine participants also reported better sleep (P = 0.039). More participants reported distressing constipation while taking morphine (9 v 1, P = 0.021) in spite of using laxatives. All other side effects were not significantly worse with morphine, although the study was not powered to address side effects.

CONCLUSIONS

Sustained release, oral morphine at low dosage provides significant symptomatic improvement in refractory dyspnoea in the community setting.

Opioids for the palliation of breathlessness in terminal illness

BACKGROUND

Breathlessness is a common symptom in people with advanced disease. The most effective treatments are aimed at treating the underlying cause of the breathlessness but this may not be possible and symptomatic treatment is often necessary. Strategies for the symptomatic treatment of breathlessness have never been systematically evaluated. Opioids are commonly used to treat breathlessness: the mechanisms underlying their effectiveness are not completely clear and there have been few good-sized trials in this area.

OBJECTIVES

To determine the effectiveness of opioid drugs given by any route in relieving the symptom of breathlessness in patients who are being treated palliatively.

SEARCH STRATEGY

An electronic search was carried out of Medline, Embase, Cinahl, the Cochrane library, Dissertation Abstracts, Cancercd and SIGLE. Review articles and reference lists of retrieved articles were hand searched. Date of most recent search: May 1999

SELECTION CRITERIA

Randomised double-blind, controlled trials comparing the use of any opioid drug against placebo for the relief of breathlessness were included. Patients with any illness suffering from breathlessness were included and the intervention was any opioid, given by any route, in any dose.

DATA COLLECTION AND ANALYSIS

Studies identified by the search were imported into a reference manager database. The full texts of the relevant studies were retrieved and data were independently extracted by two reviewers. Studies were quality scored according to the Jadad scale. The primary outcome measure used was breathlessness and the secondary outcome measure was exercise tolerance. Studies were divided into non-nebulised and nebulised and were analysed both separately and together. A qualitative analysis was carried out of adverse effects of opioids. Where appropriate, meta-analysis was carried out.

MAIN RESULTS

Eighteen studies were identified of which nine involved the non-nebulised route of administration and nine the nebulised route. A small but statistically significant positive effect of opioids was seen on breathlessness in the analysis of studies using non-nebulised opioids. There was no statistically significant positive effect seen for exercise tolerance in either group of studies or for breathlessness in the studies using nebulised opioids.

REVIEWER'S CONCLUSIONS

There is evidence to support the use of oral or parenteral opioids to palliate breathlessness although numbers of patients involved in the studies were small. No evidence was found to support the use of nebulised opioids. Further research with larger numbers of patients, using standardised protocols and with quality of life measures is needed.

The palliation of dyspnea in terminal disease

Dyspnea is a complex subjective experience that is common in terminal illness. Patients may present at any time during the course of their illness, although prevalence increases with disease progression. Dyspnea has physical, psychological, social and spiritual components; without recognizing how each of these contributes to the total suffering of dyspnea, management is unlikely to be successful. The management of dyspnea involves both pharmacological and non-pharmacological treatment. The main pharmacological palliative treatments are oxygen, opioids, and benzodiazepines, but the evidence to support these treatments is limited. More research is urgently needed to establish the efficacy of current treatments and to identify new ones.

The effect of sustained-release morphine on breathlessness and quality of life in severe chronic obstructive pulmonary disease

Morphine has been proposed as a treatment for breathlessness in patients with severe chronic obstructive pulmonary disease (COPD), but there is uncertainty as to whether or not it is effective. Orally administered sustained-release morphine was compared with placebo in a randomized, double-blind, crossover trial with two 6-wk treatment periods separated by a 2-wk washout period. The primary end point was quality of life measured using the Chronic Respiratory Disease Questionnaire (CRQ). Secondary end points included 6-min walk (6MW), distance, and breathlessness scores. Sixteen subjects with a mean age 70.7 yr, FEV1 of 0.6 L, and VC of 1.90 L were studied. There was no change in the total CRQ score with either treatment, but the score on the Mastery subscale was significantly worse with morphine (p = 0.02). The 6MW distance increased by 21 m from the beginning to the end of the placebo treatment period, but it decreased by 35 m with morphine (p = 0.04). There were no differences between treatments in breathlessness scored on daily diary cards or on the Dyspnea subscale of the CRQ. Almost all the subjects experienced adverse effects related to morphine. Sustained-release morphine was not a useful treatment for breathlessness in these patients with severe COPD.

Randomised study of n of 1 trials versus standard practice

OBJECTIVE

To compare outcomes between groups of patients with irreversible chronic airflow limitation given theophylline by n of 1 trials or standard practice.

DESIGN

Randomised controlled study of n of 1 trials versus standard practice.

SETTING

Tertiary care center outpatient department.

SUBJECTS

31 patients with irreversible chronic airflow limitation who were unsure that theophylline was helpful after an open trial.

INTERVENTIONS

n Of 1 trials (single patient randomised multiple crossover comparisons of theophylline against placebo) followed published guidelines. For standard practice patients theophylline was stopped and resumed if their dyspnoea worsened; if their dyspnoea then improved theophylline was continued. For both groups a decision to continue or stop the drug was made within three months of randomisation.

MAIN OUTCOME MEASURES

Exercise capacity as measured by six minute walking distance, quality of life as measured by the chronic respiratory disease questionnaire at baseline and six months after randomisation, and proportions of patients taking theophylline at six months.

RESULTS

26 patients completed follow up. 47% fewer n of 1 trial patients than standard practice patients were taking theophylline at six months (5/14 versus 10/12; 95% confidence interval of difference 14% to 80%) without differences in exercise capacity or quality of life.

CONCLUSIONS

n Of 1 trials led to less theophylline use without adverse effects on exercise capacity or quality of life in patients with irreversible chronic airflow limitation. These data directly support the presence of a clinically important bias towards unnecessary treatment during open prescription of theophylline for irreversible chronic airflow limitation. Confirmation in a larger study and similar studies for other problems appropriate for n of 1 trials are needed before widespread use of n of 1 trials can be advocated in routine clinical practice.

The single-subject randomized trial. A useful clinical tool for assessing therapeutic efficacy in pediatric practice

The purpose of a single-subject randomized trial is to assess objectively the efficacy of a specific therapeutic intervention in an individual patient. Treatment is randomly alternated with placebo over a number of study periods. Specific outcome measures are recorded blindly and later compared via paired statistical analysis. Single-subject trials have long been successfully performed in adults, but rarely in children. We present single-subject trials of two pediatric patients done to assess the effect of cisapride on symptoms arising from gastroesophageal reflux. In the first patient, the drug affected neither vomiting nor gagging, although stool frequency increased. Since the symptoms of concern were unaffected, cisapride was discontinued. In the second patient, use of cisapride led to a significant decrease in vomiting and wheezing; the drug was therefore incorporated into the therapeutic regimen. Single-subject randomized trials are inexpensive and simple and can be used by the family physician, pediatrician, or pediatric surgeon in daily practice. They permit the rational use of effective therapy and the abandonment of ineffective measures.

A statistical model for the "N-of-1" study

The controlled clinical trial has largely replaced case-reports as the authoritative source of information concerning the efficacy of treatment. However, many situations arise in clinical practice where treatment decisions cannot be made on the basis of such studies. The definitive clinical trial may not have been performed, or the results from a particular study may not be applicable to a particular patient. Recently, "N-of-1" studies have been proposed for the experimental evaluation of therapy in a single patient. Multiple courses of active and placebo treatments are administered, and efficacy is determined by following the response measure over a period of time. The purpose of this paper is to present a statistical model appropriate for data arising from this design. The model provides for serial correlation among the response measures captured from the subject, and for heteroskedasticity across the treatment periods. ML estimation procedures are considered, and their properties are investigated. A scoring algorithm is described to iterate to the solution of the ML equations, and considerations for hypothesis testing are presented. The techniques are illustrated through an example.

Effects of oral morphine on breathlessness and exercise tolerance in patients with chronic obstructive pulmonary disease

Previous studies have shown that opiates increase the maximal external work performed at exhaustion in patients with chronic obstructive pulmonary disease (COPD). The mechanism responsible for this improvement in exercise tolerance is unknown. The purpose of this study was to determine the effects of an oral morphine solution (0.8 mg/kg) on the exercise tolerance, perception of dyspnea, and arterial blood gases of patients with COPD. Thirteen eucapnic patients with stable COPD (FEV1 = 0.99 +/- 0.48) underwent duplicate incremental cycle ergometer tests to exhaustion (Emax) after the ingestion of placebo and after the ingestion of morphine. After the ingestion of morphine, the maximal workload increased by 18% (p less than 0.001) and the VO2 increased by 19.3% (p less than 0.001). Ten of the 13 patients had a higher ventilation at Emax after morphine ingestion. Despite the higher ventilation at Emax after morphine, the mean Borg score was not significantly higher. At Emax after morphine ingestion, the PaO2 (65.8 +/- 11.6 mm Hg) was significantly lower and the PaCO2 (43.5 +/- 8.3 mm Hg) was significantly higher than at Emax after placebo (71.9 +/- 15.5 and 38.3 +/- 8.5, respectively). When data at the highest equivalent workload were analyzed, the ventilation and the Borg scores were significantly lower, whereas the VO2 and VCO2 were comparable. From this study, we conclude that the administration of opiates can substantially increase the exercise capacity of patients with COPD. The improved exercise tolerance appears to be related to both a higher PaCO2 resulting in lowered ventilation requirements for a given workload and also to a reduced perception of breathlessness for a given level of ventilation.

Death from bronchial asthma

There is now incontrovertible evidence that there is a progressive and strikingly increased mortality from bronchial asthma in the US. The increase is more dramatic in the older age groups, but younger age groups are not spared. The exact cause or causes of this increased mortality are not known, and it is even possible (although not likely) that the increase is artifactual. This increased death rate is in sharp contrast to the general medical perception that major advances in the management of bronchial asthma have occurred. Perhaps they have, but if so, more patients are dying during this period of advances than were dying before. The most prudent course would be to assume that the excess deaths are iatrogenic in origin and to act accordingly. Even if this assumption is flawed, acting on it would improve the management of patients with bronchial asthma. If it is true that the major purpose of risk-benefit analysis is to improve patient outcome rather than merely analyze risk-benefit balance, then a series of proposals can be generated to grapple with this problem in bronchial asthma.