Intravenous Narcotics in the ICU

Pharmacokinetic considerations

Limited studies of the pharmacokinetics of pain medication suggest altered serum elimination when the liver is hypoperfused or affected by severe cirrhosis. Drugs that are eliminated by Phase I oxidation reactions are sensitive to changes in hepatic blood flow, while drugs eliminated by Phase II glucuronidation are more affected by diseased hepatocytes. Additionally, alterations in renal function decrease elimination of both parent drugs and metabolites, resulting in toxicity for selected opioids such as meperidine and morphine. Caution is suggested in drawing general conclusions from pharmacokinetic patterns of opioid elimination discussed in this review. Practitioners should be aware that drugs with short duration of action may have long half-lives and accumulate in end-stage liver and renal disease. While pharmacokinetic differences have been described in various populations, the clinical effects and adverse outcomes are greatly influenced by numerous independent physiologic alterations seen in critical care patients. Patients with severe alterations in liver and renal function should be administered pain medications judiciously because these patients are predisposed to metabolic disarrays. These patients should not be denied pain care, but they may benefit from smaller, less frequently administered doses, rather than continuous infusion of opioid drugs. Titration of doses to clinical effects with careful patient assessment for adverse effects is crucial for achieving desired therapeutic outcomes with analgesic agents in the ICU.

Relationship between behavioral and physiological indicators of pain, critical care patients' self-reports of pain, and opioid administration

OBJECTIVES

To examine the accuracy of inferences about critical care patients' pain based on physiological and behavioral indicators and to assess the relationship between registered nurse and patient pain scores and doses of opioids administered.

DESIGN

Descriptive, comparative analysis.

SETTING

Three intensive care units and two postanesthesia care units in two hospitals.

SUBJECTS

Fourteen critical care nurses who conducted 114 pain assessments on 31 surgical patients.

INTERVENTIONS

Nurses used a pain assessment and intervention notation algorithm that contained lists of behavioral and physiological indicators of pain to make inferences about a patient's pain intensity. Fourteen registered nurses completed up to five pain assessments on each patient over a 4-hr period. Following both the physiological and behavioral ratings, nurses rated the patients' pain intensity, using a 0 to 10 numeric rating scale, and they asked patients to provide a self-report of pain intensity, using a similar numeric rating scale. Nurses then administered an intravenous dose of an opioid from a sliding scale prescription.

MEASUREMENTS AND MAIN RESULTS

Moderate-to-strong correlations were found between the number of behavioral indicators at times 1 through 5 and between the number of physiological indicators and nurses' ratings of the patients' pain intensity at times 1 through 4 (p < .05). Although nurses' pain ratings were consistently lower than patients' pain ratings across the five time points, these differences were not significant. The amount of opioid analgesic administered by the nurse correlated more frequently with nurses' pain ratings than with patients' self-reports of pain intensity.

CONCLUSIONS

The use of a detailed, standardized pain assessment and intervention notation algorithm that incorporates behavioral and physiological indicators may assist healthcare professionals in making relatively accurate assessments of a patient's pain intensity. Further research is needed to determine the specific decision-making processes and criteria that healthcare professionals use to choose doses of analgesics to administer to critically ill patients.