Definitions of "respiratory depression" with intrathecal morphine postoperative analgesia: a review of the literature

Transcutaneous carbon dioxide levels and oxygen saturation following caesarean section performed under spinal anaesthesia with intrathecal opioids

BACKGROUND

Intrathecal opioids can be associated with respiratory depression which may have serious consequences. We describe the use of a non-invasive monitor (TOSCA) to measure transcutaneous carbon dioxide levels and percentage of haemoglobin oxygen saturation in post-caesarean section patients in two hospitals which used different intrathecal opioids.

METHODS

Eighty-nine women undergoing caesarean section were monitored postoperatively until 08.00h on the first postoperative day. In addition to hyperbaric bupivacaine, patients from Hospital 1 received intrathecal diamorphine 300μg: those from Hospital 2 received intrathecal fentanyl 15μg and postoperative intramuscular morphine 10mg and were given morphine patient-controlled analgesia. Data from TOSCA were analysed the following day. Respiratory depression was defined as oxygen saturations <90% or transcutaneous carbon dioxide levels >7kPa for >2min or the need for medical intervention for clinical respiratory depression.

RESULTS

Sustained hypercapnia was recorded in 8/45 (17.8%) patients from Hospital 1 and 3/44 (6.8%) from Hospital 2. Sustained oxygen saturations <90% were recorded in one patient from Hospital 2 and none from Hospital 1. The overall incidence of respiratory depression was 17.8% in Hospital 1 and 9.1% in Hospital 2. The median duration of hypercapnia was 9min [IQR 5.8-12.4] in Hospital 1 and 11.5min [IQR 7-32.8] in Hospital 2. No patient required medical intervention.

CONCLUSIONS

The incidence of opioid-induced respiratory depression detected by TOSCA is higher than previously reported by other monitoring methods. TOSCA may have a role in detecting subclinical respiratory depression in the obstetric population. Further studies with a control population are needed.

A clinical approach to neuraxial morphine for the treatment of postoperative pain

Opioids are considered a “gold standard” in clinical practice for the treatment of postoperative pain. The spinal administration of an opioid drug does not guarantee selective action and segmental analgesia in the spine. Evidence from experimental studies in animals indicates that bioavailability in the spinal cord biophase is negatively correlated with liposolubility, and is higher for hydrophilic opioids, such as morphine, than lipophilic opioids, such as fentanyl, sufentanil and alfentanil. Epidural morphine sulphate has proven analgesic efficacy and superiority over systemically administered morphine for improving postoperative pain. However, pain relief after a single epidural injection of morphine could last less than 24 hours. Techniques used to administered and prolong opioid epidural analgesia, can be costly and inconvenient. Moreover, complications can arise from indwelling epidural catheterization, particularly in patients receiving anticoagulants. Clinical trials have shown that epidural morphine in the form of extended-release liposome injections (EREM) gives good analgesia for a period of 48 hours, with no need for epidural catheterisation. Intrathecal morphine produces intense analgesia for up to 24 hours with a single shot, and clinical recommendation is to choose the minimum effective dose and do not exceed 300 μg to prevent the delay respiratory depression.

Anaesthetic management of a super morbidly obese patient for total abdominal hysterectomy: a few more lessons to learn

BACKGROUND

The prevalence of obesity is on the upward trend world-wide. This epidemic has challenging implications for anaesthetists, following the anthropometric changes associated with the disease.

OBJECTIVE

To highlight some of the challenges, the management and the lessons learnt during the management of this patient.

METHODS

This is a case report of a 52-year old super morbidly obese, diabetic, and hypertensive patient that presented for total abdominal hysterectomy. Surgery was carried out under a single-shot spinal anaesthesia with bupivacaine/fentanyl.

RESULTS

Under bupivacaine/fentanyl anaesthesia, she became very drowsy and had moderate to severe respiratory depression. She was arousable but had an obstructive sleep apnoea. Surgery was carried out successfully

CONCLUSION

A better understanding of the pathophysiology and complications that accompany obesity is needed to manage an obese patient under anaesthesia.

Effects of concurrent intravenous morphine sulfate and naltrexone hydrochloride on end-tidal carbon dioxide

Background

Respiratory depression, a potentially fatal side-effect of opioid-overdose, may be reversed by timely administration of an opioid antagonist, such as naloxone or naltrexone. Tampering with a formulation of morphine sulfate and sequestered naltrexone hydrochloride extended release capsules (MS-sNT) releases both the opioid morphine and the antagonist naltrexone. A study in recreational opioid-users indicated that morphine and naltrexone injected in the 25:1 ratio (duplicating the ratio of the formulation) found MS-sNT reduced morphine-induced euphoric effects vs intravenous (IV) morphine alone. In the same study, the effects of morphine + naltrexone on end-tidal carbon dioxide (EtCO₂), a measure of respiratory-depression, were evaluated and these data are reported here.

Methods

Single-center, placebo-controlled, double-blind crossover study. Non-dependent male opioid users were randomized to receive single IV doses of placebo, 30 mg morphine alone, and 30 mg morphine + 1.2 mg naltrexone. EtCO₂ was measured by noninvasive capnography.

Results

Significant differences in EtCO₂ least-squares means across all treatments for maximal effect (E_max) and area under the effect curve (AUE_0-2, AUE_0-8, AUE_0-24) were detected (all p ≤ 0.0011). EtCO₂ E_max values for morphine + naltrexone were significantly reduced vs morphine alone (42.9 mm Hg vs 47.1 mm Hg, p < 0.0001) and were not significantly different vs placebo (41.9 mm Hg). Median time to reach maximal effect (TE_max) was delayed for morphine + naltrexone vs morphine alone (5.0 h vs 1.0 h).

Conclusions

Results provide preliminary evidence that the naltrexone:morphine ratio within MS-sNT is sufficient to significantly reduce EtCO₂ when administered intravenously to non-dependent male recreational opioid-users. Further studies with multiple measures of respiratory-function are warranted to determine if risk of respiratory depression is also reduced by naltrexone in the tampered formulation.

Ventilatory responses after major surgery and high dependency care

BACKGROUND

Disturbed breathing during sleep, with episodic upper airway obstruction, is frequent after major surgery. Ventilatory responses to hypercapnia and hypoxia during episodes of airway obstruction are difficult to investigate because the usual measure, that of ventilation, has been attenuated by the obstruction. We simulated the blood gas stimulus associated with obstruction to allow investigation of the responses.

METHODS

To assess ventilatory responses, we studied 19 patients, mean age 59 (19-79), first at discharge from high dependency care after major abdominal surgery and then at surgical review, ~6 weeks later. Exhaled gas was analysed and inspired gas adjusted to simulate changes that would occur during airway obstruction. Changes in ventilation were measured over the following 45-70 s. Studies were done from air breathing if possible, and also from an increased inspired oxygen concentration.

RESULTS

During simulated obstruction, hypercapnia developed similarly in all the test conditions. Arterial oxygen saturation decreased significantly more rapidly when the test was started from air breathing. The mean ventilatory response was 5.8 litre min(-2) starting from air breathing and 4.5 litre min(-2) with oxygen breathing. The values 6 weeks later were 5.9 and 4.3 litre min(-2), respectively (P=0.05, analysis of variance). There was no statistical difference between the responses starting from air and those on oxygen.

CONCLUSIONS

After major surgery, ventilatory responses to hypercapnia and hypoxaemia associated with airway obstruction are small and do not improve after 6 weeks. With air breathing, arterial oxygen desaturation during simulated rebreathing is substantial.

The use of opioids at the end of life: the knowledge level of Dutch physicians as a potential barrier to effective pain management

BACKGROUND

Pain is still one of the most frequently occurring symptoms at the end of life, although it can be treated satisfactorily in most cases if the physician has adequate knowledge. In the Netherlands, almost 60% of the patients with non-acute illnesses die at home where end of life care is coordinated by the general practitioner (GP); about 30% die in hospitals (cared for by clinical specialists), and about 10% in nursing homes (cared for by elderly care physicians).The research question of this study is: what is the level of knowledge of Dutch physicians concerning pain management and the use of opioids at the end of life?

METHODS

A written questionnaire was sent to a random sample of physicians of specialties most often involved in end of life care in the Netherlands. The questionnaire was completed by 406 physicians, response rate 41%.

RESULTS

Almost all physicians were aware of the most basal knowledge about opioids, e.g. that it is important for treatment purposes to distinguish nociceptive from neuropathic pain (97%). Approximately half of the physicians (46%) did not know that decreased renal function raises plasma concentration of morphine(-metabolites) and 34% of the clinical specialists erroneously thought opioids are the favoured drug for palliative sedation.Although 91% knew that opioids titrated against pain do not shorten life, 10% sometimes or often gave higher dosages than needed with the explicit aim to hasten death. About half felt sometimes or often pressured by relatives to hasten death by increasing opioiddosage.The large majority (83%) of physicians was interested in additional education about subjects related to the end of life, the most popular subject was opioid rotation (46%).

CONCLUSIONS

Although the basic knowledge of physicians was adequate, there seemed to be a lack of knowledge in several areas, which can be a barrier for good pain management at the end of life. From this study four areas emerge, in which it seems likely that an improvement can improve the quality of pain management at the end of life for many patients in the Netherlands: 1)palliative sedation; 2)expected effect of opioids on survival; and 3) opioid rotation.

Trends in the use of opioids at the end of life and the expected effects on hastening death

The aim of our study was to describe trends in opioid use and perceptions of having hastened the end of life of a patient. In 2005, a questionnaire was sent to 6860 physicians in The Netherlands who had attended a death. The response rate was 78%. In 1995 and 2001 similar studies were done. Physicians less often administered opioids with the intention to hasten death in 2005 (3.1% of the non-sudden deaths) than in 2001 and in 1995 (7% and 10%, respectively). Physicians gave similar dosages of opioids in 2005, 2001, and 1995, but physicians in 2005 less often thought that life was actually shortened than in 2001 and 1995 (37% in 2005, 50% in 2001, and 53% in 1995). Of the physicians in 2005 who did think that the life of the patient was shortened by opioids, 94% did not give higher dosages than were, in their own opinion, required for pain and symptom management. Physicians in 2005 more often took hastening death into account when they gave higher dosages of opioids when the patient experienced more severe symptoms and with female patients. In older patients (>or=80 years), physicians took the hastening of death into account more often, but the actual dosages of opioids were lower. These data indicate that physicians in The Netherlands less often thought that death was hastened by opioids and less often gave opioids, with the intention to hasten death in 2005 than in 2001 and 1995.

Respiratory depression after neuraxial opioids in the obstetric setting

Neuraxial opioids have contributed significantly to improved labor and postcesarean delivery analgesia. In the obstetric population, epidural and intrathecal opioids are associated with a very low risk of clinically significant respiratory depression. Although rare, respiratory depression is a serious risk; patients may die or suffer permanent brain damage as a consequence. This review discusses the mechanism and incidence, as well as the prevention, detection, and management of respiratory depression with morphine, extended-release epidural morphine, and lipophilic opioids in the labor and cesarean delivery setting.

Anticipation of distress after discontinuation of mechanical ventilation in the ICU at the end of life

BACKGROUND

A considerable number of patients admitted to the intensive care unit (ICU) die following withdrawal of mechanical ventilation. After discontinuation of ventilation without proper preparation, excessive respiratory secretion is common, resulting in a 'death rattle'. Post-extubation stridor can give rise to the relatives' perception that the patient is choking and suffering. Existing protocols lack adequate anticipatory preparation to respond to all distressing symptoms.

METHODS

We analyzed existing treatment strategies in distressing symptoms after discontinuation of mechanical ventilation.

CONCLUSION

The actual period of discontinuation of mechanical ventilation can be very short, but thoughtful anticipation of distressing symptoms takes time. There is an ethical responsibility to anticipate and treat (iatrogenic) symptoms such as pain, dyspnea-associated respiratory distress, anxiety, delirium, post-extubation stridor, and excessive broncho-pulmonary secretions. This makes withdrawal of mechanical ventilation in ICU patients a thoughtful process, taking palliative actions instead of fast terminal actions. We developed a flowchart covering all possible distressing symptoms that can occur after withdrawal of mechanical ventilation and extubation. We recommend a two-phase process. Six hours before extubation, enteral feeding should be stopped and parenteral fluids reduced, overhydrated patients should be dehydrated with furosemide, administration of sedatives (for distress) and opioids (for pain and/or dyspnea) should be continued or started and methylprednisolone should be given in anticipation of stridor after extubation. Thirty minutes before extubation, Butylscopolamine should be given and methylprednisolone repeated. After this the patient should be extubated to secure a dying process as natural as possible with the lowest burden due to distress.

Pharmacokinetic-pharmacodynamic modeling of the effectiveness and safety of buprenorphine and fentanyl in rats

Objective

Respiratory depression is a serious and potentially life-threatening side-effect of opioid therapy. The objective of this investigation was to characterize the relationship between buprenorphine or fentanyl exposure and the effectiveness and safety outcome in rats.

Methods

Data on the time course of the antinociceptive and respiratory depressant effect were analyzed on the basis of population logistic regression PK–PD models using non-linear mixed effects modeling software (NONMEM). The pharmacokinetics of buprenorphine and fentanyl were described by a three- and two-compartment model, respectively. A logistic regression model (linear logit model) was used to characterize the relationship between drug exposure and the binary effectiveness and safety outcome.

Results

For buprenorphine, the odds ratios (OR) were 28.5 (95% CI, 6.9–50.1) and 2.10 (95% CI, 0.71–3.49) for the antinociceptive and respiratory depressant effect, respectively. For fentanyl these odds ratios were 3.03 (95% CI, 1.87–4.21) and 2.54 (95% CI, 1.26–3.82), respectively.

Conclusion

The calculated safety index (OR_{antinociception}/OR_{respiratory depression}) for fentanyl of 1.20 suggests that fentanyl has a low safety margin, implicating that fentanyl needs to be titrated with caution. For buprenorphine the safety index is 13.54 suggesting that buprenorphine is a relatively safe opioid.

Observational study of perioperative P tc co2 and S p o2 in non-ventilated patients receiving epidural infusion or patient-controlled analgesia using a single earlobe monitor (TOSCA) †

BACKGROUND

TOSCA, a non-invasive monitor with a single earlobe probe incorporating a Stow-Severinghaus electrode and optical sensor (Linde Medical Sensors AG, Basel, Switzerland), has previously been used with ventilated patients and in sleep laboratories. We recorded transcutaneous carbon dioxide pressures (Ptc(co(2)) and oxygen saturations (Sp(o(2)) in non-ventilated patients to investigate opioid-induced respiratory depression.

METHODS

This observational cohort study included 28 ASA I and II patients, monitored between 10 p.m. and 6 a.m., before and after elective major laparotomy. After operation, patients were kept on oxygen, 4 litre min(-1), and received either bupivacaine (0.1%) containing fentanyl (2 microg ml(-1) via epidural catheter (epidural analgesia group, EPI; n = 14) or morphine via patient-controlled analgesia infusion pump (PCA-morphine group, PCA; n = 14).

RESULTS

The preoperative median (lower/upper quartile) Ptc(co(2)) was similar in both groups at around 5.5 kPa, but significantly higher after operation in PCA with 6.9 kPa (5.6/7.3) (P = 0.02), accompanied by a longer hypercarbia time >6 kPa of 6.6 h (0.1/8.0) (P = 0.04), and lower respiratory rates of 13.9 breaths min(-1) (13.3/15.4) (P = 0.04). In EPI, the corresponding results were 5.8 kPa (5.5/6.0), 1.2 h (0.1/4.3), and 16.2 breaths min(-1) (14.8/16.7). The perioperative median Sp(o(2)) in both groups was comparable within the normal range, although generally higher when on supplemental oxygen (P = 0.26). The Sp(o(2)) time <94% was similar in both groups (P = 0.33) as were pain scores (P = 0.25).

CONCLUSIONS

Ptc(co(2)) recording in patients on PCA-morphine and supplemental oxygen revealed hypercapnia in the presence of normal respiratory rates and Sp(o(2)) values. This is recommended as an easy and sensitive monitor of respiratory depression and may have a role in the safe administration of opioid-analgesia.

Survey of intrathecal opioid usage in the UK

BACKGROUND AND OBJECTIVE

Intrathecal opioids are now used routinely in the UK for intra- and postoperative analgesia. The opioids of choice have altered over recent years and the dosage regimens used can vary between institutions. Concerns over safety have been reduced probably because much lower doses of opioids are now being used. This survey explored the practice of intrathecal opioid usage in the UK.

METHODS

We sent a questionnaire survey to 270 anaesthetic departments and received 199 replies, a response rate of 73.7%.

RESULTS

Intrathecal opioids were used in 175 (88.4%) departments. Of these departments, 107 (61.1%) had local guidelines or protocols in place. Opioids such as diamorphine (used in 136 (78.2%) of departments) and fentanyl (129 (74.1%)) with a shorter duration of action are now more commonly used than morphine (37 (21.3%)) for intrathecal analgesia. In 96 (54.5%) departments, patients were nursed on regular surgical wards following administration of spinal opioids.

CONCLUSIONS

The use of low-dose lipophilic intrathecal opioids for postoperative analgesia is widespread in the UK. Patients are commonly nursed in low-dependency post-anaesthetic care areas. The low incidence of adverse events reported by the respondents along with the popularity of the technique suggests that low-dose spinal opioid administration is safe.

Continuous Oximetry/Capnometry Monitoring Reveals Frequent Desaturation and Bradypnea During Patient-Controlled Analgesia

BACKGROUND

The most serious complication of patient-controlled analgesia (PCA) is respiratory depression (RD). The incidence of RD in the literature is derived from intermittent sampling of pulse oximetry (Spo(2)) and respiratory rate and defined as a deviation below an arbitrary threshold.

METHODS

We monitored postsurgical patients in a hospital ward receiving morphine or meperidine PCA with continuous oximetry and capnography. Nurses responding to audible monitor bedside alarms documented respiratory status and interventions.

RESULTS

A total of 178 patients were included in the analysis, 12% and 41% of whom had episodes of desaturation (Spo(2) <90%) and bradypnea (respiratory rate <10) lasting 3 min or more. One patient required "rescue" with positive pressure ventilation, and none required naloxone. Patients over 65 years of age and the morbidly obese were at greater risk for desaturation. Patients over 65 years of age were also more likely to have bradypnea, whereas the morbidly obese and patients receiving continuous infusions were less likely to have bradypnea.

CONCLUSIONS

Our incidence of RD by bradypnea is significantly higher than the 1%-2% incidence in the literature, using the same threshold criteria but more stringent duration criteria, while our incidence of RD based on desaturation is consistent with previous estimates. We conclude that continuous respiratory monitoring is optimal for the safe administration of PCA, because any RD event can progress to respiratory arrest if undetected. Better alarm algorithms must be implemented to reduce the frequent alarms triggered by threshold criteria for RD.

Respiratory function during parenteral opioid titration for cancer pain

BACKGROUND

Respiratory depression is the most feared opioid-related side-effect yet research on the topic is sparse. We evaluated changes in respiratory parameters during parenteral opioid titration for cancer pain to determine if opioid titration was associated with evidence of hypoventilation. The primary outcome measure was to measure changes in end-tidal CO(2) (ET-CO(2)) during opioid titration to pain control.

METHODS

Subjects with severe cancer pain admitted for parenteral opioid titration for poorly controlled pain were eligible. Those who were oxygen dependent were excluded. ET-CO(2), O(2) saturation, respiratory rate (RR), and vital signs were monitored daily until pain control was achieved.

RESULTS

30 patients completed the study of which 29 are reported. The mean ET-CO(2) at initial evaluation was 33.39 -/+ 5.0 and 34.79 -/+ 5.7 mmHg at pain control (P =0.14, 95% CI -0.5 to 3.3). None had an ET-CO(2) > or =50 mmHg. All maintained O(2) saturation > or = 92%. RR dropped transiently below 10/minute in two subjects.

CONCLUSIONS

Parenteral opioid titration for relief of cancer pain was not associated with respiratory depression as demonstrated by significant changes in ET-CO(2) or oxygen saturation in non-oxygen dependent cancer patients.

Low-Dose Intrathecal Morphine for Postoperative Analgesia in Children

BACKGROUND

We evaluated the efficacy and safety profile of low-dose (4-5 mcg/kg) intrathecal morphine for postoperative pain management after various surgical procedures in children.

METHODS

We reviewed the pain management service database and the medical records of patients who received low-dose intrathecal morphine for postoperative analgesia at The Children's Hospital of Philadelphia between October 2003 and March 2006. Patients had been prospectively followed for 24-48 h after the intrathecal morphine administration.

RESULTS

The medical records of 187 patients were examined. The mean age was 5.6 +/- 5.1 yr (median 4.0, interquartile range [IQR] 1.0-10.0). The median maximum pain score during the first 24 h in patients evaluated by the FLACC score and in those evaluated by the numeric verbal rating scale, was 0 (IQR 0-3) and 0 (IQR 0-4), respectively. The mean time to first rescue opioid was 22.4 +/- 16.9 h (range: 0-48 h, 95% CI: 19.9-24.8 h). During the first 24 h after surgery, 70 patients (37%) did not receive any opioids (oral or IV). Of the 117 patients who received opioids, 59 (50%) were managed with oxycodone only. Pain was managed with ketorolac in 33% of patients, either alone (11%) or in combination with IV or oral opioids (22%). The incidence of nausea or vomiting, pruritus, and urinary retention was 32%, 37%, and 6% respectively. One patient had transient postdural puncture headache, while two patients received supplemental oxygen beyond the first 60 postoperative minutes to manage occasional episodes of hypoxemia. No severe respiratory depression requiring assisted ventilation or naloxone administration was observed.

CONCLUSION

We conclude that low-dose intrathecal morphine in the pediatric population can be a useful and safe adjunct for postoperative analgesia.

The frequency and timing of respiratory depression in 1524 postoperative patients treated with systemic or neuraxial morphine

STUDY OBJECTIVE

To describe the frequency and timing of intravenous patient-controlled analgesia (IV-PCA) or neuraxial morphine-induced postoperative respiratory depression.

DESIGN

Audit of data captured by routine quality assurance of the acute pain protocols that were implemented by nurses performing routine postoperative care.

SETTING

The surgical wards of a university-affiliated, 700-bed, tertiary hospital.

PATIENTS AND INTERVENTIONS

In real time, the data of all patients enrolled into our Acute Pain Service (APS) were entered and stored in the APS database. Thereafter, patients who had received IV morphine via a PCA device or neuraxial morphine between January 1999 and December 2002 were isolated. From this subset, all patients in whom a respiratory rate (RR) less than 10 breaths per minute was recorded were retrieved.

MEASUREMENTS AND MAIN RESULTS

From a total of 4500 patients, IV or neuraxial morphine was administered to 1524 patients. Eighteen (1.2%) cases of an RR less than 10 breaths per minute were recorded (13 patients, 4 patients, and 1 patient in the IV-PCA, daily epidural morphine, and single-dose intrathecal morphine groups, respectively). A direct correlation between intraoperative fentanyl administration and postoperative respiratory depression was demonstrated between the IV-PCA (P = 0.03) and epidural groups (P = 0.05). The time from IV-PCA initiation or last neuraxial morphine administration until the diagnosis of respiratory depression ranged between 2 hours and 31.26 hours and 2 hours and 12.15 hours, respectively. Ten (55.6%) patients received naloxone.

CONCLUSION

Morphine-induced respiratory depression may occur at any time during the APS admission. However, the optimal frequency of intermittent RR monitoring is unknown. Furthermore, because multiple variables (age, sex, prior opioid administration, site of operation) may affect morphine-induced respiratory depression, further investigation must be performed to determine the ideal monitoring protocol.

The role of intrathecal drugs in the treatment of acute pain

Intrathecal opioids are widely used as useful adjuncts in the treatment of acute and chronic pain, and a number of non-opioid drugs show promise as analgesic drugs with spinal selectivity. In this review we examine the historical development and current use of intrathecal opioids and other drugs that show promise for treating pain in the perioperative period. The pharmacology and clinical use of intrathecal morphine and other opioids is reviewed in detail, including dosing guidelines for specific surgical procedures and the incidence and treatment of side effects associated with these drugs. Available data on the use of non-opioid drugs that have been tested intrathecally for use as analgesics are also reviewed. Evidence-based guidelines for dosing of intrathecal drugs for specific surgical procedures and for the treatment of the most common side effects associated with these drugs are presented.

Endogenous opiates and behavior: 2003

This paper is the 26th consecutive installment of the annual review of research concerning the endogenous opioid system, now spanning over a quarter-century of research. It summarizes papers published during 2003 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior (Section 2), and the roles of these opioid peptides and receptors in pain and analgesia (Section 3); stress and social status (Section 4); tolerance and dependence (Section 5); learning and memory (Section 6); eating and drinking (Section 7); alcohol and drugs of abuse (Section 8); sexual activity and hormones, pregnancy, development and endocrinology (Section 9); mental illness and mood (Section 10); seizures and neurologic disorders (Section 11); electrical-related activity and neurophysiology (Section 12); general activity and locomotion (Section 13); gastrointestinal, renal and hepatic functions (Section 14); cardiovascular responses (Section 15); respiration and thermoregulation (Section 16); and immunological responses (Section 17).

Spinal anesthesia for arthroscopic knee surgery

BACKGROUND AND OBJECTIVE

The purpose of the study was to compare the effects of adding 50 microg of morphine, 25 microg of fentanyl or saline to 6 mg of hyperbaric bupivacaine on postoperative analgesia and time to urination in patients undergoing arthroscopic knee surgery under spinal anesthesia.

METHODS

The study was designed in a prospective, randomized, double-blinded and placebo-controlled manner. Sixty ASA I-II patients were randomized into the following three groups: Group BM: 6 mg of bupivacaine and 50 microg of morphine, Group BF: 6 mg of bupivacaine and 25 microg of fentanyl, and Group BS: 6 mg of bupivacaine and saline. Selective spinal anesthesia was performed in a lateral decubitus position, with the operative knee dependent for 10 min.

RESULTS

In all groups satisfactory anesthesia was provided during the operation. There was a statistically significant difference between all the groups in times to voiding [Group BM 422 +/- 161 min; Group BF 244 +/- 163 min; Group BS 183 +/- 54 min (mean +/- SD)]. The incidence of pruritus was significantly greater in Group BM (80%) and BF (65%) in comparison with Group BS (no pruritus) (P < 0.05). The incidence of nausea was significantly increased in Group BM (35%) in comparison with Group BF (10%) and Group BS (P < 0.05). Analgesic consumption was significantly greater in Group BS in comparison with Groups BM and BF (P < 0.01).

CONCLUSIONS

We conclude that during spinal anesthesia even mini-dose intrathecal morphine is not acceptable for outpatient surgery due to side-effects, especially severely prolonged time to urination.