Nausea and vomiting induced by opioid analgesics in the setting of patient-controlled analgesia (PCA)
PCA is a pain-control system where a patient can treat his own pain rather than wait for a nurse to give more medication. PCA uses a computerised pump connected directly to the patient's intravenous (IV) line. He receives pain medication by pressing a button - allowing him to take control of the pain. This eliminates the anxious waiting for pain relief and the peaks of pain.
This machine has several safety features and an alarm system. The machine is set up as prescribed by the doctor and will give only limited, measured amounts of analgesic. The total amount the patient can give himself each hour is carefully controlled within a safe limit.
When the pain control is administered intra-muscularly, it usually takes about half an hour to feel the pain relieving effects of the medication because it is absorbed more slowly into the bloodstream. Often the patient will become quite sleepy, but after a few hours sleep will re-awaken with pain. With PCA he usually receives a small continuous flow of medication, and alsomay give medication himself to provide a more constant level of comfort. This is the reason doctors often prescribe PCA for the first few days following surgery or injury, when patients feel the most discomfort.
When given by intravenous infusion or administered by the patient, morphine is recognised as an effective method for postoperative control of pain, without the need for intramuscular injections of analgesics. However, nausea and vomiting associated with the use of opioid analgesics is the main drawback to prescribing them and requires the administration of concomitant injectable antiemetic agents.
References
1. Macintyre PE, Runciman WB, Webb RK. An acute pain service in an Australian teaching hospital : the first year. Med J Australia 1990 ; 153(7) : 417-421.
2. Rapp SE, Ready LB, Greer BE. Postoperative pain management in gynaecology oncology patients utilizing epidural opiate analgesia and patient-controlled analgesia. Gynaecologic Oncology 1989 ; 35(3) : 341-344.
