Analgesic and Hemodynamic Effects of Morphine
Analgesic and Hemodynamic Effects of Morphine
Study Objectives: To evaluate the analgesic and hemodynamic effects of a single dose of intravenous morphine 7.5 mg in patients experiencing moderate-to-severe postoperative pain, and to determine any gender differences in analgesic response.
Design: Randomized, double-blind, parallel-group, multicenter study.
Setting: Postanesthesia care unit of a university teaching hospital.
Patients: Eighty-eight patients who underwent total abdominal hysterectomy or prostatectomy.
Intervention: Thirty-seven patients received a single dose of morphine sulfate 7.5 mg and 51 patients received placebo, both administered intravenously for 1 minute.
Measurements and Main Results: Overall, morphine had no significant effect on systolic or diastolic blood pressure, heart rate, oxygen saturation, or respiratory rate. Compared with baseline, morphine significantly reduced pain intensity at 2, 5, and 10 minutes after administration (p<0.05). The difference in pain intensity between patients who received morphine and those who received placebo, however, was significant only at the 5-minute time point (p<0.02). Patients receiving morphine also reported mild pain relief at 2 and 5 minutes after its administration. Peak analgesic effect was reported 2 minutes after its administration in three quarters of the patients. Significant gender differences also were observed in response to analgesic effect. In women, no significant differences in pain intensity were seen at any time between the morphine and placebo groups, whereas in men receiving morphine, pain intensity was significantly less at 2, 5, and 10 minutes compared with baseline and that seen in the placebo group. Women were generally more satisfied with their pain treatment than were men.
Conclusion: A single 7.5-mg intravenous bolus dose of morphine did not appear to provide adequate reduction in perceived pain intensity in patients with moderate-to-severe postoperative pain. In addition, in contrast to the findings of other experimental pain studies, our data suggest that women are more tolerant of postoperative pain than are men.
The degree and duration of postoperative pain are often proportionate to the extent of surgical trauma. Little has been published with respect to the time course of pain after various surgeries. Pain is usually most intense within the first 1-2 postoperative days. Factors other than surgical trauma that may contribute to the experience of postoperative pain include age and gender. Older subjects and men are believed to be more tolerant of pain.
Opioids are used widely to treat postoperative pain. The mechanisms by which these drugs relieve pain are not clearly understood. Opioids may act on injured tissues to reduce inflammation, impede the transmission of impulses in the dorsal horn, and reduce anxiety as well as the unpleasantness of pain. Although the total administered dose of an opioid analgesic is influenced by the severity of the pain, dosing guidelines for postoperative pain appear to follow fixed schedules. An initial dose of morphine for the treatment of postoperative pain is often in the range of 2-3 mg; subsequent doses may be even less. Little has been published regarding the analgesic or hemodynamic effects of larger doses of intravenous morphine in the immediate post-operative period. Most clinicians are reluctant to use higher doses due to anticipated adverse effects. Furthermore, there are scant data regarding the peak analgesic effect of single intravenous doses of morphine in postoperative patients. However, it is known that there is significant variability among patients with respect to postoperative opioid requirements and that postoperative pain continues to be undertreated.
The objectives of our study were to evaluate the analgesic and hemodynamic effects of a relatively large (7.5-mg) dose of intravenous morphine in patients with moderate-to-severe postoperative pain, and to determine any gender differences in analgesic response.
Study Objectives: To evaluate the analgesic and hemodynamic effects of a single dose of intravenous morphine 7.5 mg in patients experiencing moderate-to-severe postoperative pain, and to determine any gender differences in analgesic response.
Design: Randomized, double-blind, parallel-group, multicenter study.
Setting: Postanesthesia care unit of a university teaching hospital.
Patients: Eighty-eight patients who underwent total abdominal hysterectomy or prostatectomy.
Intervention: Thirty-seven patients received a single dose of morphine sulfate 7.5 mg and 51 patients received placebo, both administered intravenously for 1 minute.
Measurements and Main Results: Overall, morphine had no significant effect on systolic or diastolic blood pressure, heart rate, oxygen saturation, or respiratory rate. Compared with baseline, morphine significantly reduced pain intensity at 2, 5, and 10 minutes after administration (p<0.05). The difference in pain intensity between patients who received morphine and those who received placebo, however, was significant only at the 5-minute time point (p<0.02). Patients receiving morphine also reported mild pain relief at 2 and 5 minutes after its administration. Peak analgesic effect was reported 2 minutes after its administration in three quarters of the patients. Significant gender differences also were observed in response to analgesic effect. In women, no significant differences in pain intensity were seen at any time between the morphine and placebo groups, whereas in men receiving morphine, pain intensity was significantly less at 2, 5, and 10 minutes compared with baseline and that seen in the placebo group. Women were generally more satisfied with their pain treatment than were men.
Conclusion: A single 7.5-mg intravenous bolus dose of morphine did not appear to provide adequate reduction in perceived pain intensity in patients with moderate-to-severe postoperative pain. In addition, in contrast to the findings of other experimental pain studies, our data suggest that women are more tolerant of postoperative pain than are men.
The degree and duration of postoperative pain are often proportionate to the extent of surgical trauma. Little has been published with respect to the time course of pain after various surgeries. Pain is usually most intense within the first 1-2 postoperative days. Factors other than surgical trauma that may contribute to the experience of postoperative pain include age and gender. Older subjects and men are believed to be more tolerant of pain.
Opioids are used widely to treat postoperative pain. The mechanisms by which these drugs relieve pain are not clearly understood. Opioids may act on injured tissues to reduce inflammation, impede the transmission of impulses in the dorsal horn, and reduce anxiety as well as the unpleasantness of pain. Although the total administered dose of an opioid analgesic is influenced by the severity of the pain, dosing guidelines for postoperative pain appear to follow fixed schedules. An initial dose of morphine for the treatment of postoperative pain is often in the range of 2-3 mg; subsequent doses may be even less. Little has been published regarding the analgesic or hemodynamic effects of larger doses of intravenous morphine in the immediate post-operative period. Most clinicians are reluctant to use higher doses due to anticipated adverse effects. Furthermore, there are scant data regarding the peak analgesic effect of single intravenous doses of morphine in postoperative patients. However, it is known that there is significant variability among patients with respect to postoperative opioid requirements and that postoperative pain continues to be undertreated.
The objectives of our study were to evaluate the analgesic and hemodynamic effects of a relatively large (7.5-mg) dose of intravenous morphine in patients with moderate-to-severe postoperative pain, and to determine any gender differences in analgesic response.
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