The present invention is directed to a method and apparatus for automatically adjusting the medication level for a patient, and more particularly to adjusting the basal rate and the bolus rate of administration in a patient control analgesia mode based on the patient's pain intensity.
Infusion pumps are used to automatically administer liquid medicants to patients. The liquid medicant is supplied from a source of medicant and delivered to the patient via a catheter or other injection device. The manner in which the liquid medicant is infused is controlled by the infusion pump, which may have various modes of infusion. An infusion pump typically can operate in five basic modes of infusion: 1) a continuous mode in which the pump delivers a single volume at a single rate; 2) an auto-ramp mode in which the pump delivers liquid medicant at a rate that gradually increases to a threshold rate, remains at the threshold rate for a period of time, and then gradually decreases; 3) an intermittent mode in which the pump delivers discrete liquid volumes spaced over relatively long periods of time, such as a liquid volume every three hours; 4) a custom mode in which the pump can be programmed to deliver a unique infusion rate during each of 25 different time periods; and 5) a pain controlled analgesic (PCA) mode during which the pump will periodically infuse boluses of an analgesic in response to requests by the patient.
In pain control analgesia, a pain relief medication or analgesic is delivered to the patient via an infusion pump into a patient's intravenous line, or to the epidural space or an interthecal space. Usually the medication is delivered at a constant rate, called the basal rate. The physician programs the basal rate into the pump. However, the patient is allowed, within bounds, to give himself additional medication, to reduce the pain level, if desired. This is done via a bolus cord. The patient presses a button on the bolus cord and the pump delivers a small bolus of medication to the patient. The maximum level of medication given in response to each press of the bolus cord button, is programmed into the pump by the physician. The maximum number of button presses which will result in a discharge of a bolus is also programmed into the pump by the physician. Once the pump is programmed by the physician, the patient can give himself a bolus whenever he needs it, regardless of time between requests. However, if the patient exceeds the maximum number of boluses programmed, any additional requested boluses will not be successful and will not result in the delivery of medication.
The physician limits the amount of medication given to the patient at any one time, and over a period of time, to reduce the level of side effects. Some pain relief medications have highly undesirable side effects, such as nausea, vomiting, itching and confusion, cardiac and respiratory depression or in sufficient quantity, may result in death. Patient functionality, e.g., mobility and awareness, is affected by pain and side effects.
Controlling of the amount of pain medication, i.e., the basal rate, the bolus dose and the maximum number of bolus doses available to the patient is a delicate balance of competing requirements. To increase pain relief, a physician will prescribe greater medication. However, large doses of some pain medication can increase the side effects and can impair patient functionalities. Using a pain medication may reduce pain sufficiently to enable the patient to move about. Using a level of pain medication which produces confusion detracts from the patient's mobility.
During acute care, when the patient is in greater need of additional pain medication, it is important to be able to adjust the PCA basal rate, the bolus rate and the bolus amount more frequently, always taking into account the effect of side effects and impairment of patient functionalities.
Infusion modes are programmed into the infusion pump by the caregiver or physician. In a hospital or other caregiver facility, a physician or caregiver can visit a patient once or twice a day to check if the programmed infusion mode, dose and frequency are providing appropriate relief to the patient. If the patient is receiving medication at home or away from a caregiver facility, such visits may be less frequent. In most of the pre-programmed modes, rechecking the mode, dose and frequency once or twice a day may be sufficient. If the patient is in the PCA mode, however, the patient's condition may vary more, requiring more frequent adjustment and more frequent visits by the physician or caregiver. If the patient is not able to receive additional adjustments or visits from the physician or caregiver, whether in the home or the hospital, the patient may be in extreme pain and may not receive appropriate pain relief for many hours.
U.S. Pat. No. 5,643,212 to Coutre et al. discloses an infusion pump management system in which the patient's physiological signs are used in a biofeedback loop. The system evaluates the patient's physiological signs and suggests alternate infusion treatment based on those signs. The proposed modifications are then sent to the operator for confirmation. Delivery rate changes are made by the operator (physician or caregiver), so the patient must wait until the operator can evaluate the proposed changes before the patient can receive any relief.
There is a need for an automatic method of adjusting the medication level in patient control analgesia taking into account the patient's pain level, side effects and any impairment of functionalities. There is a need for an apparatus for automatically adjusting the medication level in response to input from a patient regarding his pain level, side effects and impairment of functionalities, without having to contact the caregiver or physician. There is a need for a method of automatically adjusting the medication level in patient control analgesia using a predetermined set of criteria which is patient specific, yet provides the patient the ability to have his medication adjusted without having to contact a caregiver or physician.