Novel delivery systems for postoperative analgesia.

Moderate-to-severe postoperative pain is usually controlled using a multimodal approach, including opioids. Intravenously administered patient-controlled analgesia (IV PCA) with opioids, popular for over 40 years, enables patients to control their level of analgesia and has advantages over a nurse-administered approach, including more satisfied patients and improved pain relief. Unfortunately, IV PCA has drawbacks such as device programming errors, medication prescribing errors, pump malfunction, limitations on patient mobility, IV patency issues, and transmission of infection. Furthermore, the setup of an infusion pump is often complex, time-consuming, and requires witnessed confirmation. Complicating IV PCA is the problem of commonly used compounds, morphine and hydromorphone, having significantly reduced brain/effector-site permeability and active metabolites, both of which create the risk of delayed adverse events. Novel patient-controlled modalities that incorporate rapid effector site-permeating opioids and non-invasive routes of administration offer great promise to enhance both patient and caregiver experiences with postoperative analgesia systems.

A comparison of lidocaine and bupivacaine digital nerve blocks on noninvasive continuous hemoglobin monitoring in a randomized trial in volunteers.

BACKGROUND: Blood hemoglobin can be monitored continuously and noninvasively with a noninvasive spectrophotometric sensor (Masimo SpHb). The perfusion index (PI) of the finger is directly related to the clinical accuracy of SpHb. We evaluated those variables that influence PI without the influences of surgery and anesthesia. METHODS: Based on our past studies, 12 awake adult volunteers were studied. A SpHb sensor was attached to the same finger of each hand. The temperature of each finger was measured via a skin surface probe. A digital nerve block (DNB) was performed with 1% lidocaine on one finger and 0.25% bupivacaine on the other finger of the opposite hand. SpHb, PI, and finger temperature were monitored continuously 30 minutes before and 3 to 4 hours after placement of the DNB. A random effects spline regression was used to flexibly model the outcomes before and after the DNB and to compare the effects of lidocaine and bupivacaine. RESULTS: The DNBs increased the PI for both lidocaine and bupivacaine (P < 0.0001) and finger temperature from both lidocaine (P < 0.0001) and bupivacaine (P = 0.02). The duration of action of bupivacaine was markedly longer than that of lidocaine (P < 0.0001). Between 45 and 75 minutes after insertion of the DNB, the PI with bupivacaine was substantially higher than that of lidocaine. The PI was directly related to changes in finger temperature and SpHb. During this time interval, 11 of the 12 volunteers receiving bupivacaine descriptively had increases in finger temperature ranging from no change to 6.1°C. In contrast, only 6 of the 12 lidocaine volunteers had increases in finger temperature ranging from no change to 4°C. Changes in PI were directly correlated with SpHb values (correlation coefficient = 0.7). CONCLUSIONS: A DNB increases PI and finger temperature. These increases lasted 2 to 3 hours longer with bupivacaine than lidocaine. The increases in PI were associated with slightly higher SpHb values. We conclude that the DNB induces increases in PI and temperature of the finger. Because of the close relationship between finger temperature, PI, and SpHb, consistently increasing finger temperature and PI could increase the accuracy of SpHb.

Does a digital regional nerve block improve the accuracy of noninvasive hemoglobin monitoring?

BACKGROUND: Blood hemoglobin (Hb) can be continuously monitored utilizing noninvasive spectrophotometric finger sensors (Masimo SpHb). SpHb is not a consistently accurate guide to transfusion decisions when compared with laboratory Co-Oximetry (tHb). We evaluated whether a finger digital nerve block (DNB) would increase perfusion and, thereby, improve the accuracy of SpHb. METHODS: Twenty adult patients undergoing spinal surgery received a DNB with lidocaine to the finger used for the monitoring of SpHb. SpHb-tHb differences were determined immediately following the DNB and approximately every hour thereafter. These differences were compared with those in our previously reported patients (N = 20) with no DNB. The SpHb-tHb difference was defined as "very accurate" if <0.5 g/dL and "inaccurate" if >2.0 g/dL. Perfusion index (PI) values at the time of each SpHb-tHb measurement were compared. RESULTS: There were 57 and 78 data points in this and our previous study, respectively. The presence of a DNB resulted in 37 % of measurements having SpHb values in the "very accurate group" versus 12 % in patients without a DNB. When the PI value was >2.0, only 1 of 57 DNB values was in the "inaccurate" group. The PI values were both higher and less variable in the patients who received a DNB. CONCLUSIONS: A DNB significantly increased the number of "very accurate" SpHb values and decreased the number of "inaccurate" values. We conclude that a DNB may facilitate the use of SpHb as a guide to transfusion decisions, particularly when the PI is >2.0.

Possible augmentation of neuromuscular blockade by propofol during recovery from rocuronium.

Propofol is a widely used drug in anesthesia practice, and its pharmacological characteristics are well known. However, propofol is not known for neuromuscular effects. As part of clinical neuromuscular monitoring, the neuromuscular responses to train-of-four (TOF) stimulation were monitored and recorded. We observed, in two cases of balanced anesthesia maintained by desflurane and fentanyl, that administration of a small dose of propofol during almost complete recovery from rocuronium in two patients resulted in marked decreases of both T1 (first twitch response of the TOF) and the TOF ratio. This neuromuscular block dissipated in both patients without any subsequent neuromuscular effects. These two observations provide visual confirmation of the possible impact of propofol on recovery from a rocuronium neuromuscular blockade.

A comparison of three methods of hemoglobin monitoring in patients undergoing spine surgery.

BACKGROUND: Hemoglobin values (Hb) can facilitate decisions regarding perioperative transfusion management. Currently, Hb can be determined invasively by analyzing blood via laboratory Co-Oximetry (tHb) or by point-of-care HemoCue (HCue). Recently, a new noninvasive, continuous spectrophotometric sensor (Masimo SpHb) was introduced into clinical practice. We compared the accuracy of the SpHb and HCue with tHb. METHODS: Twenty patients, ages 40 to 80 years, were studied. They received general anesthesia and underwent spine surgery in the prone position. All blood samples were obtained from a radial artery catheter. SpHb, tHb, and HCue were determined immediately after induction of anesthesia, but before the start of surgery and approximately every hour thereafter. Primary outcomes were defined on the basis of the following differences between measures: SpHb - tHb or HCue - tHb. All patients had 3 to 5 observations taken on each measure. Differences and absolute differences were analyzed by several techniques to assess accuracy. We also investigated the relationship between observed differences and the following variables: tHb level, duration of surgery, age, weight, and perfusion index. RESULTS: Data consisted of 78 measurements of SpHb, tHb, and HCue made on the 20 patients. Absolute differences between SpHb and tHb were <1.5 g/dL for 61% of observations, between 1.6 to 2.0 g/dL for 16% and >2.0 g/dL for 22% of the observations. Observed differences displayed significant decreases with time and higher perfusion index values. No systematic relationships were observed with age or weight. Except for 1 value, all of the HCue values were <1.0 g/dL of tHb. CONCLUSIONS: Although HCue was consistently accurate, our data confirm that SpHb often correlated well with tHb values. Yet our study indicates that SpHb may not be as accurate as clinically necessary in some patients. Improved refinement of continuous, noninvasive technology, such as SpHb, could address important clinical requirements.

Current and developing methods of patient-controlled analgesia.

Moderate-to-severe acute postoperative pain is commonly controlled with opioids administered via programmable intravenous (IV) patient-controlled analgesia (PCA) infusion pumps. Intravenously administered opioids provide effective relief of postoperative pain, and IV PCA enables patients to control their level of analgesia, which has advantages over nurse-administered approaches, including more satisfied patients and improved pain relief. Unfortunately, commonly used opioid analgesics can cause significant adverse effects. Furthermore, IV PCA has drawbacks, such as device programming errors, system errors, medication errors, limitations in patient mobility, and potential for IV tubing kinks, clogging, and transmission of infection. The IV route of administration is also characterized by a rapid, high peak in analgesic drug concentration followed by rapidly decreasing concentrations. Consequently, respiratory depression, excessive sedation, and inadequate pain control can occur. Furthermore, the technical assembly of an infusion pump is often complex and time-consuming. PCA modalities that incorporate superior opioid analgesics, such as sufentanil, and novel noninvasive routes of administration offer great promise for enhancing the patient and caregiver experience with the use of postoperative PCA.

Massive blood transfusions: the impact of Vietnam military data on modern civilian transfusion medicine.

To determine the coagulation defects associated with massive blood transfusions, coagulation studies were performed on 21 battle casualties admitted to the US Naval Support Activity Hospital, Da Nang, Vietnam. All but one patient who received less than 20 units of Acid-Citrate-Dextrose blood (7 patients) did not develop a coagulopathy. All patients who received more than 20 units (14 patients) developed a clinically significant coagulation defect. Although the partial thromboplastin and prothrombin times were markedly prolonged (i.e., low Factor V and XIII levels), restoring these times to normal levels by fresh frozen plasma administration did not terminate the clinical coagulopathy.In all 12 patients who had platelet counts less than 60,000/mm(3), a clinical bleeding problem (coagulopathy) developed. The coagulopathy eventually spontaneously resolved (n = 4), was successfully treated with fresh blood (n = 4), or the patients died (n = 4). A mathematical analysis confirmed that the thrombocytopenia is dilutional in origin and is the primary cause of a coagulopathy from massive blood transfusions. The authors conclude that clinically important coagulopathies predictably occur after administration of 20-25 units of stored Acid-Citrate-Dextrose blood in acutely wounded, previously healthy soldiers. Fresh frozen plasma should not be a major therapeutic choice for coagulopathies in massive blood transfusions. Treatment of dilutional thrombocytopenia (50,000/mm(3)) is a primary component of treating coagulopathies associated with massive blood transfusions.

The impact of productivity-based incentives on faculty salary-based compensation.

In industry and academic anesthesia departments, incentives and bonus payments based on productivity are accounting for an increasing proportion of a total compensation. When incentives are primarily based on clinical productivity, the impact on the distribution of total compensation to the faculty is not known. We compared a pure salary-based compensation methodology based entirely on academic rank to salary plus incentives and/or clinical productivity compensation (i.e., billable hours). The change in compensation methodology resulted in two major findings. First, the productivity-based compensation resulted in a large increase in the variability of total compensation among faculty, especially at the Assistant Professor rank. Second, the mean difference in total compensation between Assistant and Full Professors decreased. The authors conclude that this particular incentive plan, primarily directed toward clinical productivity, dramatically changed the distribution of total compensation in favor of junior faculty. Although not analytically investigated, the potential impact of these changes on faculty morale and distribution of faculty activities is discussed.