Preventable medical injuries in older patients.

Injuries associated with hospitalization are more common in older (>/=65 years) than in younger patients (<65 years), and they may be more severe and more often preventable. The increasing age of the population magnifies the importance of this problem. In this review, we first consider medical injuries in general and then review the literature for 6 categories: adverse drug events, falls, nosocomial infections, pressure sores, delirium, and surgical and perioperative complications. For each of these categories, older patients appear to be at higher risk, ranging from a 2.2-fold increase for perioperative complications to a 10-fold increase for falling, based on Harvard Medical Practice Study rates. The main cause of these increased risks appears to be the diminished physiological reserve of elderly patients; however, age alone is a less important predictor of adverse events than comorbidities and functional status. Furthermore, many of these complications appear to be preventable, although the proportion preventable varies by type of complication. While some prevention strategies are specifically beneficial in older patients, many apply to all age groups. Geriatric care units and consultation systems have improved outcomes in some instances, although the data are mixed. The success of intervention varies by type of complications. For medications, various interventions have been successful, and fall prevention programs have been demonstrated to be effective in the nursing home and home.

Abdominal cross-sectional imaging for inpatients with abnormal liver function test results: yield and usefulness.

BACKGROUND: Abdominal cross-sectional imaging is often performed to evaluate abnormal liver function test (LFT) results in hospitalized patients. However, few data are available regarding the yield and usefulness of imaging inpatients for the indication of abnormal LFT results, the process of requesting abdominal imaging studies, or the response to their findings. METHODS: We retrospectively reviewed abdominal imaging scans that were obtained during a 27-month period. We matched the imaging studies done with the indication of abnormal LFT results; all scans were requested using computerized physician order entry. Reports were coded for interpretation and associated process step results. To determine the usefulness of the imaging studies, a random sample of patient charts with positively coded imaging studies were reviewed. Imaging examinations were considered useful if they provided new diagnostic information and/or changed subsequent patient care. RESULTS: Of 6494 abdominal imaging studies, 856 were performed for the indication of abnormal LFT results and matched to both image reports and laboratory results. Report coding judged 37% of interpretations as clinically significant, including 27% with "positive" (abnormal results and explain the abnormal LFT results) examinations. Among the positive examinations, the most common diagnoses were biliary obstruction (25%), cholecystitis (21%), malignancy (20%), and cirrhosis (14%). Positively coded reports provided new clinical information in 63% of these studies and changed patient care in 42% of cases. Process measures assessed provision of additional information to and from radiologists (69% and 8%, respectively) and the frequency with which the findings of current abdominal imaging studies were compared with those of prior studies (59%). CONCLUSION: Abdominal cross-sectional imaging studies performed on inpatients with abnormal LFT results had a high diagnostic yield and frequently changed patient care.

Changes in pacing lead impedance over time predict lead failure.

It has been suggested that a decrease in lead impedance may predict pacing lead failure, but there is limited prospective data about the relation of changes in lead impedance over time to lead performance. We monitored changes in lead impedance through implantable pulse generators with real-time telemetry data capability in 105 patients with Medtronic 4012 leads (n = 38) and Medtronic 4004 leads (n = 67). Pacing lead failure was documented by serial ambulatory electrocardiographic monitoring or intensified pacemaker clinic surveillance. A significant decrease in lead impedance was observed in patients with Medtronic 4012 and Medtronic 4004 leads with documented lead failure, whereas lead impedance remained stable over time in patients without documented lead failure. The sensitivity and specificity of a lead impedance decrease of > or =15% to predict lead failure were 69% and 70%, respectively. The sensitivity and specificity of a lead impedance decrease of > or =30% to predict lead failure were 36% and 90%, respectively. The positive and negative predictive values for a lead impedance decrease of > or =15% were 54% and 81%, respectively, and for a lead impedance decrease of > or = 30% were 65% and 73%, respectively. Thus, small decreases in lead impedance may identify failing leads. Serial measurement of pacing lead impedance over time is a useful tool to monitor pacing lead performance.

Bafilolides, potent inhibitors of the motility and development of the free-living stages of parasitic nematodes.

Three Streptomyces isolates were identified as producing macrolide antibiotics of the bafilomycin or leucanicidin types during an evaluation of Australian actinomyces for the production of inhibitors of larval development in the parasitic nematode, Haemonchus contortus. Bafilomycins A1, B1, C1, and D were obtained from culture A239 and the 2-O-methyl-L-rhamnosyl derivative of bafilomycin A1, leucanicidin, from cultures A223 and A240. All these 'bafilolides' gave similar patterns of inhibition typified by an initial paralysis of newly hatched L1 larvae and a lethal toxicity within 24 h. LD50 values for inhibition of larval development of McMaster H. contortus ranged from 0.23 micrograms ml-1 for leucanicidin to 2.5 micrograms ml-1 for bafilomycin D. The bafilolides had broad spectrum nematocidal activity, being equi-potent as inhibitors of H. contortus, Trichostrongylus colubriformis and Ostertagia circumcincta larval development. Further, all bafilolides caused some inhibition of H. contortus L3 motility, with the semi-synthetic analogue, bafilomycin B2, the most potent inhibitor (LP50 against McMaster H. contortus 1.9 microgram ml-1). Nematode strains resistant to the known benzimidazole, levamisole and avermectin anthelmintics showed no cross resistance to the bafilolides, supporting the hypothesis that the bafilolides act by an independent mechanism.

Unipolar sensing in contemporary pacemakers: using myopotential testing to define optimal sensitivity settings.

Bipolar lead use has increased due to oversensing concerns with older unipolar systems. Data on contemporary unipolar devices with improved hardware design and greater programming flexibility is lacking. Using a randomized crossover design, unipolar and bipolar sensing characteristics of 22 atrial and 16 ventricular leads were compared in 34 patients who had pulse generators of programmable polarity. Unipolar and bipolar intracardiac electrogram amplitudes, pacing and sensing thresholds at rest were similar. Provocative maneuvers were used to assess for myopotential inhibition. At atrial sensitivities of 0.625-1.50 mV, myopotential inhibition occurred in 11 (50%) atrial leads in the unipolar mode compared to 1 (5%) in the bipolar mode (p < 0.001). At sensitivities of > 1.50 mV myopotential inhibition occurred in only 1 ventricular (unipolar) lead. An optimal sensitivity setting for each polarity was derived using clinic test results and assessed by ambulatory ECG (AECG). At these optimal settings, oversensing occurred in 1 (6%) atrial and 1 (8%) ventricular unipolar lead during AECG monitoring, whereas oversensing was not seen in any leads programmed to the bipolar mode. Undersensing occurred in 5 (29%) atrial unipolar versus 1 (6%) bipolar lead (p = 0.08). Undersensing was not observed in any of the ventricular leads. Myopotential inhibition may be frequently provoked by provocative maneuvers at higher sensitivity settings in atrial unipolar leads. The frequency of oversensing can be significantly reduced by defining an optimal sensitivity setting using simple isometric maneuvers. Given present day concerns over bipolar lead longevity, increased utilization of unipolar ventricular leads should be considered.

Structure of actinotetraose hexatiglate, a unique glucotetraose from an actinomycete bacterium.

An Actinomycete strain A499 belonging to the genera Amycolatopsis or Amycolata isolated from a Western Australian soil sample produced the cyclic decapeptide antibiotic quinaldopeptin (1), together with the actinotetraose hexatiglate (2), the hexa-ester of a novel non-reducing glucotetraose.

Limitations to activation of the antitachycardia burst pacing function of the Symbios 7008 pacemaker in the universal (DDD) mode.

The Symbios 7008 antitachycardia pacemaker was implanted in five patients for control of supraventricular tachycardia. Shortly after implantation in the first two patients, it was noted that the burst pacing sequence was not automatically activated by tachycardia when the pacemaker was in the DDD mode. Data from these two and the subsequent three patients were evaluated to explain this observation. The problem was primarily related to the operation of the device during the postventricular atrial refractory period. In all patients, the atrial electrogram encroached upon the programmed postventricular atrial refractory period because VA conduction during SVT was less than the lowest programmable interval (155 ms). Atrial events occurring during this interval will not trigger the tachycardia termination sequence. In all five patients, the size of the atrial electrogram decreased substantially (48 +/- 10%; mean +/- SD) during supraventricular tachycardia compared to sinus rhythm. In at least two of the five patients, decreased atrial size during supraventricular tachycardia may also have resulted in intermittent failure of atrial sensing during tachycardia, even at the most sensitive setting (0.6 mV). The latter may remain a problem even if the technical fault in SVT detection in the DDD mode were corrected. Two related problems were noted in the DDD mode: ventricular events during rapid SVT do not reset the low rate interval, resulting in random low rate pacing; and, automatic prolongation of atrial refractory period by two successive ventricular events without an intervening atrial sensed event compounds problems of atrial sensing. All of these problems were easily circumvented in all patients by noninvasive reprogramming to the DVI mode in which supraventricular tachycardia detection is based on ventricular sensing. These findings have implications for the future design of such devices.

Ambulatory electrocardiography for the detection of pacemaker lead failure.

The suboptimal performance of some polyurethane bipolar pacing leads has highlighted concern about the optimal method of monitoring pacemaker lead performance. Since the manifestations of premature lead failure may be initially intermittent, we hypothesized that ambulatory electrocardiography (AECG) would be a more sensitive tool for the detection of pacing lead failure compared to increased pacemaker clinic surveillance. Since the Medtronic safety alerts on the 4012, 4082, and 4004 leads, we have followed 261 patients by serial AECG and 165 patients by increased pacemaker clinic surveillance. Lead failures were identified in 75 patients: 68 in the AECG group (31%) and 7 in the clinic group (4%, P < 0.001). Repeat AECG confirmed the lead failure in 38 (97%) of 39 patients in which it could be done. Pacing lead failure documented by AECG could be confirmed by a subsequent clinic assessment in only 15 (25%) of 60 patients evaluated (P < 0.001). The actuarial survival of the 4012 lead was significantly lower in the AECG group compared to the clinic group (56% vs 87% survival at 8 years, P < 0.002). Similar trends were observed for the 4082 and 4004 leads. AECG is a more sensitive method of surveillance for pacemaker lead function compared to pacemaker clinic assessment. AECG should be incorporated into the routine follow-up of pacemaker patients.

A randomized comparison of a bipolar steroid-eluting electrode and a bipolar microporous platinum electrode: implications for long-term programming.

Differences in acute and chronic pacing thresholds were compared in patients receiving either the Medtronic Model 4004 steroid-eluting lead or the Medtronic Model 4012 microporous platinum lead. Patients (n = 35) were randomized at the time of implant to receive either a steroid-eluting (n = 17) or a microporous (n = 18) lead. Pacing thresholds were determined within 24 hours and at 2, 4, 6, 12, 24, and 52 weeks postimplant. By 2 weeks postimplant, pacing thresholds measured at 0.8, 1.6, 2.5, 3.3, and 4.2 V were significantly lower in the steroid lead group compared to the microporous lead group (P < 0.05). At 24 weeks, the voltage threshold at 0.3 msec was 0.8 V in 88% of patients with a steroid lead whereas this threshold was only observed in 33% of patients with the microporous lead (P < 0.01). At 52 weeks the pacing energy measured at 1.6 V, twice pulse duration threshold, was significantly lower in the steroid lead group (0.81 +/- 0.59 microJ) compared to the microporous lead group (1.25 +/- 0.60 microJ, P < 0.05). Thirteen patients in the steroid lead group and 9 patients in the microporous lead group have been programmed at a pulse amplitude of 1.6 V since the 24-week follow-up visit. These patients have been followed for a minimum of 6 months without documented failure to capture. This study shows that pacemaker/lead systems with stable chronic low thresholds can be safely programmed to low pulse amplitude settings. This practice will prolong the longevity of pulse generators.