Factors that might impact intrathecal drug delivery (IDD) dose escalation: a longitudinal study.

BACKGROUND: Intrathecal drug delivery (IDD) system with implantable pumps has been used to treat cancer-related pain as well as noncancer-related chronic pain. Opioids, including morphine and hydromorphone, are the most commonly used intrathecal (IT) agents. Although technology, techniques, and knowledge of IDD have improved, dose escalation occurs relatively rapidly in noncancer pain. METHODS: Retrospective chart review of IDD pump patients, implanted for a minimum of 2 years, was designed to investigate possible existing predictors that might impact IDD dose escalation, such as patient's demographic risk factors, duration of the treatment, and diagnosis of the patient's pain correlates with increase in medication requirement. Primary outcome was defined as the annual percent escalation in daily opioid dosage, and secondary outcome was the average annual percent reduction in VRS pain scores. RESULTS: Median dosage escalation was 17% per year for patients with neuropathic pain compared with 12% per year for patients with other pain modalities. Mean opioid dosage increased 30.4% more rapidly for patients with neuropathic pain than for other pain modalities. The adjusted difference in means was 28.8% (P = 0.001). None of the secondary exposures were statistically significant after the Bonferroni adjustment. No association was found between pain modality and annual percent change in VRS pain score. CONCLUSION: Annual increases in daily opioid dosage were higher among patients with neuropathic pain than among patients with other modalities; we also found no evidence of difference in annual pain reduction.

Differential epidural block predicts the success of visceral block in patients with chronic visceral abdominal pain.

BACKGROUND AND AIMS: Differential thoracic epidural regional block, also known as a differential neural block (DNB), involves the placement of an epidural catheter placed in the thoracic epidural space to achieve appropriate anesthesia in a dermatomal distribution. This is a retrospective case series evaluating how well a DNB may predict success of subsequent visceral blockade in patients with chronic abdominal pain of visceral origin. METHODS: Of 402 patients who had a DNB performed for unexplained abdominal pain from January 2000 to January 2009, 81 patients were found to have results consistent with visceral pain and thus underwent subsequent visceral blockade. Basic demographic data, years of chronic pain, history of psychosocial issues, initial visual analog scale (VAS) pain score, pain location, and medication usage were documented in our electronic medical record database. Parameters regarding DNB and visceral blocks also were documented. Descriptive statistics were computed for all variables. The positive predictive value (PPV) for DNB for whom visceral block was successful (at least a 50% reduction in VAS) was calculated. Additionally, subjects with successful visceral blocks were compared to those with unsuccessful visceral blocks. PARTICIPANTS: All patients with chronic abdominal pain with normal gastrointestinal studies who underwent DNB. SETTING: Tertiary Outpatient Pain Management Clinic. DESIGN: Retrospective Cohort Study. RESULTS: Mean age of patients was 46 (± 15) years, 73% were female, and median duration of pain was 5 years. 67% of subjects were taking opioid analgesics. PPV of DNB was 70.4%. Only factor found to be statistically significant with visceral block success was baseline VAS with higher scores associated with DNB predictive success (6.8 ± 1.7 vs. 5.5, 1.8; P = 0.004). Use of membrane stabilizing medications was significantly more common in subjects for whom visceral block was not successful (46% vs. 25%; P = 0.058). Area underneath curve (AUC) for VAS was found to be 0.70 (95% CI: 0.57, 0.82), which signifies fair discrimination. CONCLUSION: Differential neural block is fairly predictive of subsequent visceral block success in patients with chronic abdominal pain of visceral origin. An initial VAS ≥ 5 provides a sensitivity of 93%, which implies that VAS < 5 may predict unsuccessful visceral block. Contrarily, a value of ≥ 8 would provide a specificity of 92% and may be used to predict success of subsequent visceral block.

Early postoperative subcutaneous tissue oxygen predicts surgical site infection.

BACKGROUND: Subcutaneous oxygen partial pressure is one of several determinants of surgical site infections (SSIs). However, tissue partial pressure is difficult to measure and requires invasive techniques. We tested the hypothesis that early postoperative tissue oxygen saturation (Sto(2)) measured with near-infrared spectroscopy predicts SSI. METHODS: We evaluated Sto(2) in 116 patients undergoing elective colon resection. Saturation was measured near the surgical incision, at the upper arm, and at the thenar muscle with an InSpectra™ tissue spectrometer model 650 (Hutchinson Technology Inc., Hutchinson, MN) 75 minutes after the end of surgery and on the first postoperative day. An investigator blinded to Sto(2) assessed patients daily for wound infection. Receiver operating characteristic curves were used to analyze the performance of Sto(2) measurements as a predictor of SSI. RESULTS: In 23 patients (≈ 20%), SSI was diagnosed 9 ± 5 days (mean ± SD) after surgery. Patients who did and did not develop an SSI had similar age (48 ± 14 vs 48 ± 15 years, respectively; P = 0.97) and gender (female:male, 15:8 vs 46:47, respectively), but patients who developed SSI weighed more (body mass index 32 ± 7 vs 27 ± 6 kg/m(2); P < 0.01). Sto(2) at the upper arm was lower in patients who developed SSI than in those who did not develop SSI (52 ± 22 vs 66 ± 21; P = 0.033), and these measurements had a sensitivity of 71% and specificity of 60% for predicting SSI, using Sto(2) of 66% as the cutoff point. CONCLUSION: Sto(2) measured at the upper arm only 75 minutes after colorectal surgery predicted development of postoperative SSI, although the infections were typically diagnosed more than a week later. Although further testing is required, Sto(2) measurements may be able to predict SSI and thus allow earlier preventive measures to be implemented.

Transdermal oxygen does not improve sternal wound oxygenation in patients recovering from cardiac surgery.

BACKGROUND: Sternal wound dehiscence and infection complicate 1% of cardiac surgeries. Tissue oxygen tension (PsqO(2)) is the primary determinant of surgical wound infection risk and is often critically low in surgical incisions. We tested the hypothesis that local transdermal delivery of oxygen improves oxygenation in sternotomy wounds after cardiac surgery. Our secondary hypothesis was that supplemental inspired oxygen improves sternal wound PsqO(2). METHODS: After undergoing cardiopulmonary bypass, 30 patients randomly received (1) 2 EpiFlo oxygen generators (Ogenix, Inc., Beachwood, OH) that provided oxygen at 6 mL/h into an occlusive wound dressing or (2) identical-appearing inactive generators. PsqO(2) and temperature were measured in the wound approximately 5 mm below the skin surface. PsqO(2) and arterial oxygen (Pao(2)) were measured 1 h after intensive care unit admission (Fio(2) = 60%) and on the first and second postoperative mornings at Fio(2) of both 30% and 50% in random order. RESULTS: Data from four patients were excluded for technical reasons. Patient characteristics were similar in each group, as were type of surgery and perioperative management. Increasing Fio(2) from 30% to 50% improved Pao(2) from 99 [84-116] to 149 [128-174] mm Hg (P < 0.001, mean [95% CI]) and sternal wound PsqO(2) from 23 [16-33] to 27 [19-38] mm Hg (P < 0.001). In contrast, local oxygen delivery did not improve tissue oxygenation: 24 [14-41] vs 25 [16-41] mm Hg (P = 0.88). CONCLUSIONS: Additional inspired oxygen improved Pao(2) and sternal wound PsqO(2) after bypass and may, consequently, reduce infection risk. However, oxygen insufflated locally into an occlusive dressing did not improve wound PsqO(2) and, therefore, does not appear to be useful clinically in cardiac surgery patients to reduce sternal wound infections.

Fenoldopam and renal function after partial nephrectomy in a solitary kidney: a randomized, blinded trial.

OBJECTIVE: To test the hypothesis that fenoldopam administration ameliorates ischemic injury, preserving the glomerular filtration rate and serum creatinine postoperatively after partial nephrectomy in patients with a solitary kidney. MATERIALS AND METHODS: Fenoldopam is a short-acting dopamine-1 receptor agonist that might provide renal protection during ischemic stress. A total of 90 patients with a solitary functioning kidney who were undergoing partial nephrectomy were randomized to fenoldopam or placebo in a double-blind protocol. The patients assigned to fenoldopam received an infusion rate of 0.1 µg/kg/min for 24 hours. The effect of fenoldopam on renal function was assessed by comparing the groups on the change in glomerular filtration rate from baseline to the third postoperative day (primary outcome) and on the change in serum creatinine over time (secondary outcome). RESULTS: Of the 90 enrolled patients, 77 provided analyzable data (43 in fenoldopam and 44 in placebo group). Fenoldopam (vs placebo) did not reduce the mean percentage of change in the glomerular filtration rate from baseline to the third postoperative day (P = .15), with an estimated ratio of means of 0.89 (95% confidence interval 0.69-1.09) for fenoldopam vs placebo. The postoperative serum creatinine in the 2 groups changed at comparable rates from postoperative day 1 to 4 (group-by-time interaction, P = .72) after adjusting for baseline creatinine, with no difference in the mean serum creatinine over time (P = .78). CONCLUSION: Fenoldopam administration did not preserve renal function in the clinical setting of renal ischemia during solitary partial nephrectomy, as evidenced by changes in the glomerular filtration rate or serum creatinine.