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POSTOPERATIVE PAIN The site of the surgery has a profound effect upon the degree of postoperative pain a patient may suffer. Operations on the thorax and upper abdomen are more painful than operations on the lower abdomen which, in turn, are more painful than peripheral operations on the limbs. However, any operation involving a body cavity, large joint surfaces or deep tissues should be regarded as painful. In particular, operations on the thorax or upper abdomen may produce changes in pulmonary function, an increase in abdominal muscle tone and an associated decrease in diaphragmatic function. The result will be an inability to cough and clear secretions which may lead to collapse of lung tissue and acute pneumonia. Pain causes an increase in the sympathetic response of the body with subsequent rises in heart rate, cardiac work and oxygen consumption. Prolonged pain can reduce physical activity and lead to venous stasis and an increased risk of deep vein thrombosis and consequent pulmonary embolism. These problems are unpleasant for the patient and may prolong hospital stay. For many years, the standard method of treating postoperative pain in the developed world has been intramuscular opioid (usually morphine). Many studies have shown that under-treatment of acute postoperative pain occurs because doctors and nurses overestimate the length of action and the strength of the drugs and that they have fears about respiratory depression, vomiting, sedation and dependency. Nowadays, several methods are used to manage postoperative pain. These treatments use combinations of non-narcotic drugs and/or nerve blocks to minimize the amount of narcotic medication needed to keep patients comfortable. Usually there are three levels of acute pain management:
I Level • paracetamol and FANS on fixed hours, with or without opioids; • continuous infusion of FANS and/or weak opiods; • continuous infusion and/or perineural infusion of local anesthetics.
II Level • PCA i.v. without basal infusion (bolus of morphine > 1 mg, every 5-7 minutes); • Continuous peridural analgesia (PCEA) with opioids and/or local anesthetics; • Intratecal morphine (single dose < 0.5 mg)
III Level • Intravenous continuous infusion of high dosage of opioids; • PCA with continuous basal infusion; • Continuous intrathecal infusion (peridural or spinal) of high dosage of opioids.
But by far the most common method are with Epidural Analgesia and Intravenous Analgesia, which can be controlled by the patients, it means that they can adjust the level of analgesia required, according to the severity of the pain. The use of epidural analgesia has now been extended to a wide range of surgical procedures, such as major leg, abdominal and chest surgery. An 'epidural' allows patients to remain comfortable after these types of operations. A small amount of medication is continuously infused through the epidural catheter and numbs the painful area. Only several years ago, patients undergoing these operations would have been in extreme pain for several days after surgery. They would have required large amounts of narcotic drugs, such as morphine. These drugs made the patients sleepy, disoriented, and often extremely nauseated. It is impressive to see them now - alert, orientated, comfortable, and nausea free. They are able to get up sooner and this speeds recovery and reduces complications. Epidural analgesia is a major advance of modern medicine. With epidural analgesia, a thin plastic catheter is placed between two bones of your back by an Anesthesiologist. This plastic catheter is called an "Epidural Catheter". Where the catheter is placed in your back depends upon the type of surgery you will have and the medicine you will receive. For example, the catheter may be placed in the lower back for knee surgery and higher up for gallbladder surgery.The catheter will be taped up your back to your shoulder. You may lie on your back without causing any problems. A small pump (which is about the size of a cellular phone or walkman) will be attached to your catheter after surgery. We use two types of pain medicine to block your pain after surgery: narcotics and local anesthetics. The pain medicine is absorbed through the epidural space, into the nerve roots, in your back . . . hour after hour . . .
Advantages Epidural analgesia gives very good pain relief. This method of pain control usually causes less sleepiness than medicine given through your IV or as a shot. Epidural medicine stops your pain early and blocks it along its path to your brain. Patients may have shorter hospital stays and fewer problems after surgery.
When is it used Epidural pain control may be used for almost any surgery below your upper chest. Patient having surgery on the aorta, gallbladder, prostate, knee, and hip can find this type of pain control valuable. Women who have hysterectomies could find this a good method of pain relief. Some patients may not have the option of using this type of pain control because of other health care problems, such as taking blood thinners. You may want to ask your surgeon if epidural pain control would be good for you. Epidural pain control will be used only if you, your surgeon, and the anesthesiologist all agree that this is a good plan. If you think you would like an epidural for pain control after surgery, please ask. An anesthesiologist can discuss an epidural with you in more detail and answer your questions. With the peridural analgesia:
It should be assumed that all patients are at risk of this occasional complication and a high level of care and vigilance should be maintained. Trained personnel should be present at all times to check on the rate and depth of respiration and level of consciousness of the patient at regular intervals. A global assessment is necessary particularly during the first 24 hours of treatment. Any patient receiving epidural opioids whose level of consciousness drops must be assumed to have respiratory depression until proved otherwise. Where available, the use of supplementary oxygen has been recommended. It is particularly dangerous to prescribe other opioids to patients receiving epidural opioids as this increases the likelihood of clinically significant respiratory depression. Opioid/local anaesthetic mixtures have been adopted in some centres in an attempt to reduce the frequency and severity of side effects seen with infusions of pure local anaesthetics. Dilute concentrations of these agents have been combined with opioids and delivered by infusion through an epidural catheter. These mixtures appear to produce a synergistic effect. Patient Controlled Analgesia (PCA) is a method of administering IV opioid via an infusion pump which allows the patient to titrate the dose of opioid delivered to their analgesic requirement within pre-set limits as defined by the medical staff. The patient activates delivery of an opioid bolus by pressing a hand held button. The machine is set with a "lock-out" time during which no drug will be delivered, even if the button is pressed. PCA has been shown to be a safe and effective method of analgesia when used by clinical staff who understand the technique, and who have immediate back-up advice available. PCA is generally used after major surgery and should be continued until the patient no longer requires parenteral opioids including im opioids. Most patients require PCA for 2-3 days after major surgery. They then require some other effective form of analgesic before PCA is discontinued. To achieve successful and safe analgesia with PCA requires that the patient understands what is required and this should be explained in detail before the operation. Almost every opioid drug has been used for PCA. Once a selection has been made other parameters need to be set including the size of the bolus dose, the minimum time period between doses (the lock-out period) and the maximum dose allowed. Some devices permit the use of a continuous background infusion but for the reasons stated in the section on intravenous administration it will not be considered here. Morphine is the most popular drug and will be used as an example. The ideal dose of morphine has been found to be 1 mg. However, regular review is needed in every case to ensure that pain relief is adequate. The aim of the lock-out period is to prevent overdosage occurring because of overenthusiastic demands for more analgesia. The lock-out time should be long enough for the previous dose to have an effect. In practice, lockout times of between 5 and 10 minutes are enough for most opioids. A maximum dose can be programmed into most PCA devices to prevent overdose. In practice, it is more logical to accept that the analgesic requirements of patients will vary considerably and some patients may require very large amounts to achieve adequate pain relief.
Pump for the management of acute pain. CLICK on the imagine to magnify the picture
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Peridural Analgesia
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