Does intrathecal morphine alter the stress response following coronary artery bypass grafting surgery?

Analgesic efficacy and risk of low-to-medium dose intrathecal morphine in patients undergoing cardiac surgery: An updated meta-analysis

Background

To evaluate the analgesic efficacy and risk of low-to-medium dose intrathecal morphine (ITM) (i.e., ≤0.5 mg) following cardiac surgery.

Methods

Medline, Cochrane Library, Google scholar and EMBASE databases were searched from inception to February 2022. The primary outcome was pain intensity at postoperative 24 h, while the secondary outcomes included intravenous morphine consumption (IMC), extubation time, hospital/intensive care unit (ICU) length of stay (LOS), and ITM-associated side effects (e.g., respiratory depression). Subgroup analysis was performed on ITM dosage (low: <0.3 mg vs. medium: 0.3–0.5 mg).

Results

Fifteen RCTs involving 683 patients published from 1988 to 2021 were included. Pooled results showed significantly lower postoperative 24-h pain scores [mean difference (MD) = −1.61, 95% confidence interval: −1.98 to −1.24, p < 0.00001; trial sequential analysis: sufficient evidence; certainty of evidence: moderate] in the ITM group compared to the controls. Similar positive findings were noted at 12 (MD = −2.1) and 48 h (MD = −1.88). Use of ITM was also associated with lower IMC at 24 and 48 h (MD: −13.69 and −14.57 mg, respectively; all p < 0.05) and early tracheal extubation (i.e., 48.08 min). No difference was noted in hospital/ICU LOS, and nausea/vomiting in both groups, but patients receiving ITM had higher risk of pruritus (relative risk = 2.88, p = 0.008). There was no subgroup difference in IMC except a lower pain score with 0.3–0.5 mg than <0.3 mg at postoperative 24 h. Respiratory depression events were not noted in the ITM group.

Conclusion

Our results validated the analgesic efficacy of low-to-medium dose ITM for patients receiving cardiac surgery without increasing the risk of respiratory depression.

The use of pre-operative intrathecal morphine for analgesia following coronary artery bypass surgery

With the emergence of rapid extubation protocols following cardiac surgery, providing adequate analgesia in the early postoperative period is important. This prospective randomised double-blind study investigated the benefits of pre-operative intrathecal administration of low dose morphine in patients undergoing coronary artery bypass graft surgery. Postoperative analgesia, pulmonary function, stress response and postoperative recovery profile were assessed. Thirty patients were allocated into two groups, receiving either 500 mug of morphine intrathecally prior to anaesthesia and intravenous patient-controlled analgesia with morphine postoperatively following tracheal extubation, or only postoperative intravenous patient-controlled analgesia. In the intrathecal group, the total consumption of intravenous morphine following surgery was significantly reduced by 40% and patients reported lower pain scores at rest, during the first 24 h following extubation. Peak expiratory flow rate was greater and postoperative catecholamine release was significantly lower. Patients in the control group had a higher incidence of reduced respiratory rate following extubation.

Low-dose intrathecal morphine does not delay early extubation after cardiac surgery

PURPOSE

This study was designed to examine the efficacy of low-dose intrathecal morphine (ITM) on extubation times and pain control after cardiac surgery.

METHODS

43 patients undergoing elective cardiac surgery were enrolled in this prospective, randomized, double-blind placebo controlled trial. Patients were given a pre-induction dose of ITM (6 microg x kg(-1) per ideal body weight in 5 mL normal saline, group ITM) or 5 mL of intrathecal normal saline (group ITS). Anesthesia was induced with thiopental (3 mg x kg(-1)), sufentanil, midazolam and rocuronium. The total allowable doses of sufentanil and midazolam for the entire case were limited to 0.5 microg x kg(-1) and 0.045 mg x kg(-1) respectively. Anesthesia was maintained with isoflurane before and during cardiopulmonary bypass (CPB), and with propofol after CPB. In the postanesthesia care unit, patients received nurse-administered morphine followed by patient-controlled analgesia morphine. Serial visual analogue scale pain scores, morphine use, mini-mental state examinations and pulmonary function tests were measured for 48 hr. Patient satisfaction questionnaires were completed at the time of discharge.

RESULTS

Mean times to extubation from the application of dressings were short and did not differ between groups (ITM = 41.4 +/- 33.0 min, ITS = 39.2 +/- 37.1 min). During the first 24 hr postoperatively, the ITM group had improved pain control and a lower iv morphine requirement than the control group, both at rest and during deep breathing. Both forced expiratory volume in one second and forced vital capacity were improved in the ITM group. There were no differences in spinal-related side effects or in the overall complication rates. Patient satisfaction was high in both groups.

CONCLUSION

Low-dose ITM for cardiac surgery did not delay early extubation, but it improved postoperative analgesia and pulmonary function.

Intrathecal and Epidural Anesthesia and Analgesia for Cardiac Surgery

Adequate postoperative analgesia prevents unnecessary patient discomfort. It may also decrease morbidity, postoperative hospital length of stay and, thus, cost. Achieving optimal pain relief after cardiac surgery is often difficult. Many techniques are available, and all have specific advantages and disadvantages. Intrathecal and epidural techniques clearly produce reliable analgesia in patients undergoing cardiac surgery. Additional potential benefits include stress response attenuation and thoracic cardiac sympathectomy. The quality of analgesia obtained with thoracic epidural anesthetic techniques is sufficient to allow cardiac surgery to be performed in awake patients without general endotracheal anesthesia. However, applying regional anesthetic techniques to patients undergoing cardiac surgery is not without risk. Side effects of local anesthetics (hypotension) and opioids (pruritus, nausea/vomiting, urinary retention, and respiratory depression), when used in this manner, may complicate perioperative management. Increased risk of hematoma formation in this scenario has generated much of lively debate regarding the acceptable risk-benefit ratio of applying regional anesthetic techniques to patients undergoing cardiac surgery.

Regional analgesia in the critically ill

OBJECTIVE

The objective of this review is to analyze and describe the use of regional analgesia in the critically ill.

DATA SOURCE

A Medline search from 1966 to 2004 using the search terms critically ill, nerve blocks, regional analgesia, and regional anesthesia, as well as a search in the Cochrane library, was performed, and standard international textbooks related to critical care and regional anesthesia were searched for practice recommendations.

STUDY SELECTION

Studies, case reports, and review articles relevant to the topic were included.

DATA EXTRACTION AND SYNTHESIS

Data were extracted and analyzed in a descriptive fashion.

CONCLUSION

Regional analgesia using single-injection regional blocks and continuous neuraxial and peripheral catheters can play a valuable role in a multimodal approach to pain management in the critically ill patient to achieve optimum patient comfort and to reduce physiologic and psychological stress. By avoiding high systemic doses of opioids, several complications like withdrawal syndrome, delirium, mental status changes, and gastrointestinal dysfunction can be reduced or minimized. Because of limited patient cooperation during placement and monitoring of continuous regional analgesia, indications for their use must be carefully chosen based on anatomy, clinical features of pain, coagulation status, and logistic circumstances. High-quality nursing care and well-trained physicians are essential prerequisites to use these techniques safely in the critical care environment.

Intrathecal morphine for off-pump coronary artery bypass grafting

OBJECTIVE

To determine if preinduction intrathecal morphine is associated with successful intraoperative extubation in patients undergoing off-pump coronary artery bypass grafting.

DESIGN

A retrospective noncontrolled chart review of all patients undergoing off-pump coronary artery bypass grafting.

SETTING

Single university hospital.

PARTICIPANTS

One hundred twelve patients.

INTERVENTIONS

One hundred twelve of 150 patients received preinduction intrathecal morphine as part of routine anesthetic care for off-pump coronary artery bypass grafting. Patients received a mean of 1.0 mg of intrathecal morphine (range 0.3-1.6 mg); average weight-corrected dose was 13.2 microg/kg (range 5-24 microg/kg).

MEASUREMENTS AND MAIN RESULTS

This study included intraoperative extubation rate, delayed respiratory depression, and other complications potentially attributable to intrathecal morphine. An intraoperative extubation rate of 77% was found. Five patients received naloxone postoperatively, 4 of them for delayed respiratory depression.

CONCLUSIONS

It is concluded that intrathecal morphine is associated with a high intraoperative extubation rate in patients undergoing off-pump coronary artery bypass grafting. The authors' practice included 24-hour respiratory monitoring to detect delayed respiratory depression.

Intrathecal morphine provides effective and safe analgesia in children after cardiac surgery

BACKGROUND

The purpose of this prospective, randomized, blinded to observer study was to assess the analgesic effect and safety of intrathecal morphine (ITM) in post-operative pain control in children after heart surgery with a sternotomy incision.

METHODS

Eighty children, 3-55 kg in body weight, undergoing elective cardiac surgery with opioid-based anaesthesia were randomly divided into two treatment groups to receive either 20 micrograms/kg ITM at induction of anaesthesia or control. To standardize the protocol for administration of post-operative rescue intravenous morphine boluses and infusion (20-60 micrograms/kg/h), the Cardiac Analgesic Assessment Scale (CAAS) was used.

RESULTS

Nine patients were excluded from the study after randomization. Thirty-five patients were enrolled to the ITM group and 36 to the control group. The groups were similar for demographics and intra-operative clinical characteristics. The mean time for the first intravenous morphine dose from ITM administration or equivalent time zero in the control group was significantly longer (P = 0.003) in the ITM group compared with the control group (12.3 vs. 8.7 h). Time from Paediatric Intensive Care Unit (PICU) admission to the start of intravenous morphine was also significantly longer (P = 0.01) in the ITM group (6.0 vs. 3.4 h). The total intravenous morphine consumption over the mean 19 post-operative hours was significantly lower (P = 0.03) in the ITM group. However, the use of ITM did not result in earlier extubation or earlier discharge from the PICU. Of the 35 patients who received ITM at induction of anesthesia, 20% (n = 7) did not require any additional morphine in the PICU compared with three out of 36 control group patients. This did not reach statistical significance. The incidence of adverse events was low in both groups.

CONCLUSIONS

An ITM dose of 20 micrograms/kg had a significant (P = 0.03) intravenous morphine-sparing effect after cardiac surgery. Effective analgesia was observed for 12 h after administration of intrathecal morphine.

Intrathecal Morphine Reduces Infarct Size in a Rat Model of Ischemia-Reperfusion Injury

Systemically-administered morphine reduces infarct size in rat models of myocardial ischemia-reperfusion. We sought to determine whether much smaller doses of spinally-administered morphine offer a similar cardioprotective benefit. Barbiturate-anesthetized, open-chested, Wistar rats with chronic indwelling thoracic intrathecal catheters were instrumented for hemodynamic measurements and subjected to 30 min of coronary occlusion and 90 min of reperfusion. Myocardial infarct size was determined using triphenyl-tetrazolium staining. Rats were randomly assigned to receive intrathecal (IT) 0.9% saline (vehicle), IV morphine (0.3 mg/kg) plus IT saline, small-dose IT morphine (0.3 microg/kg), or large-dose IT morphine (3 microg/kg) 20 min before occlusion. IV and both doses of IT morphine reduced infarct size, defined as area of necrosis expressed as a percentage of area at risk (%AN/AAR), as compared with vehicle. The %AN/AAR group means were as follows: IV (n = 7), 30% +/- 6%; IT(small-dose) (n = 9), 30% +/- 5%; IT(large-dose) (n = 9), 18% +/- 4%; and vehicle (n = 10), 47% +/- 5%. There were no significant differences in infarct size among the morphine-pretreated rats. During ischemia-reperfusion, heart rate was unchanged from baseline in the IT(large-dose) group, whereas in the IT(small-dose), IV and vehicle groups, significant declines in heart rate occurred. Changes in arterial blood pressure were similar among groups. These results indicate that IT morphine reduces infarct size in rats, and this benefit is as great as that provided by IV morphine administration.

IMPLICATIONS

Our findings suggest that spinally-administered morphine provides a previously unrecognized cardioprotective benefit. In anesthetized rats subjected to ischemia-reperfusion injury, we show that very small doses of intrathecal morphine reduce infarct size in rats, and this benefit is as great as that provided by much larger doses of IV morphine.

The Effect of Music on the Neurohormonal Stress Response to Surgery Under General Anesthesia

Several pharmacological interventions reduce perioperative stress hormone release during surgery under general anesthesia. Listening to music and therapeutic suggestions were also studied, but mostly in awake patients, and these have a positive effect on postoperative recovery and the need for analgesia. In this study, we evaluated the effect of listening to music under general anesthesia on the neurohormonal response to surgical stress as measured by epinephrine, norepinephrine, cortisol, and adrenocorticotropic hormone (ACTH) blood levels. Thirty female patients scheduled for abdominal gynecological procedures were enrolled and randomly divided into two groups: group NM (no music) and group M (music). In group M, music was played from after the induction of anesthesia until the end of surgery. In the NM group, the patients wore the headphones but no music was played. We established three sample times for hormonal dosage during the procedure and one in the recovery room. Hemodynamic data were recorded at all times, and postoperative consumption of morphine in the first 24 h was noted. There was no group difference at any sample time or in the postoperative period in terms of mean arterial blood pressure, heart rate, isoflurane end-tidal concentration, time of the day at which the surgery was performed, bispectral index (BIS) value, doses of fentanyl, or consumption of postoperative morphine. There was no difference between the two groups with regard to plasmatic levels of norepinephrine, epinephrine, cortisol, or ACTH at any sample time, although the blood level of these hormones significantly increased in each group with surgical stimulation. In conclusion, we could not demonstrate a significant effect of intraoperative music on surgical stress when used under general anesthesia.

IMPLICATIONS

Listening to music under general anesthesia did not reduce perioperative stress hormone release or opioid consumption in patients undergoing gynecological surgery.

A comparison of intrathecal opioid and intravenous analgesia for the incidence of cardiovascular, respiratory, and renal complications after abdominal aortic surgery

Major surgery evokes a stress response that can produce deleterious consequences, especially in a population at high risk for those complications. We tested the hypothesis that decreasing or eliminating one of the sources of stress by providing intense analgesia in the immediate postoperative period via application of neuraxial opioids would decrease major nonsurgical complications. Two-hundred-seventeen patients scheduled to undergo abdominal aortic surgery were randomly allocated to receive either general anesthesia alone (control) or general anesthesia combined with intrathecal opioid (1 micro g/kg sufentanil with 8 micro g/kg preservative-free morphine injected at the L4-5 interspace). Postoperative care was identical in the two groups, including patient-controlled analgesia. Each patient provided an assessment of postoperative pain using a visual analog scale. Postopera-tive complications were recorded according to criteria established a priori. The administration of intrathecal opioid provided more intense analgesia than patient-controlled analgesia during the first 24 h postoperatively (P < 0.05). There was no difference between groups for the incidence of combined major cardiovascular, respiratory, and renal complications (P > 0.05) or mortality (P > 0.05). The incidence of myocardial damage or infarction, as defined by abnormal plasma concentration of troponin I, did not differ between the two groups (P > 0.05). In patients undergoing major abdominal vascular surgery, decrease of one contributor to postoperative stress, by provision of intense analgesia for the intraoperative and initial postoperative period, via application of neuraxial opioid, does not alter the combined major cardiovascular, respiratory, and renal complication rate.

IMPLICATIONS

Provision of intense analgesia for the initial postoperative period after major abdominal vascular surgery, via the administration of neuraxial opioid, does not alter the combined incidence of major cardiovascular, respiratory, and renal complications.