Validation of Noninvasive Methemoglobin and Carboxyhemoglobin Measurements Using Pulse Co-Oximeter in Healthy Dogs.

Purpose: To assess the agreement between pulse co-oximeter and blood co-oximeter in measuring methemoglobin (MetHb) and carboxyhemoglobin (COHb) in healthy, awake dogs. Patients and Methods: Forty-five healthy dogs were enrolled in the study. Pulse co-oximetry was performed using the Masimo Radical 7 Pulse Co-Oximeter with a Rainbow® adhesive sensor. Simultaneously, venous blood samples were collected, and MetHb and COHb were immediately measured using a Stat Profile Prime Plus VET Critical Care Analyzer. Paired measurements of MetHb and COHb were evaluated via Spearman correlation, intra-class correlation (ICC), and Bland-Altman plots to evaluate the degree of agreement between the pulse co-oximeter and the blood co-oximeter. Results: A total of 45 paired MetHb and COHb measurements were collected. There was a weak correlation between the pulse co-oximeter and the blood co-oximeter readings. The correlation coefficients for MetHb and COHb were 0.0 (95% CI, -0.3 to 0.3) and 0.03 (95% CI, -0.27 to 0.32), respectively. The ICC indicated poor agreement between the pulse and blood co-oximeter for MetHb (ICC = 0.00, 95% CI: -0.12 to 0.15) and COHb (ICC = 0.03, 95% CI: -0.27 to 0.33). Bland-Altman plots revealed low mean bias but wide limits of agreement, indicating that the pulse co-oximeter overestimated MetHb by on average of 0.7% (P < 0.0001) (95% LoA: -0.5 to 2.0) and COHb by on average 0.2% (P = 0.59) (95% LoA: -4.6 to 5.0). Conclusion: Obtaining MetHb and COHb measurements with the Masimo Radical 7 Pulse Co-Oximeter is straightforward in healthy, awake dogs. However, the device does not provide accurate measurements compared to the blood co-oximeter, specifically in the range of MetHb and COHb in healthy dogs, based on the wide LoA.

Comparative Effectiveness of Targeted Intrathecal Drug Delivery Using a Combination of Bupivacaine with Either Low-Dose Fentanyl or Hydromorphone in Chronic Back Pain Patients with Lumbar Postlaminectomy Syndrome.

OBJECTIVE: Targeted intrathecal drug delivery (TIDD) is an effective interventional pain management modality often used in postlaminectomy patients with refractory chronic low back pain. A combination of intrathecal bupivacaine with an opioid is often used. However, intrathecal catheter tip granulomas have occurred with use of morphine or hydromorphone but generally not with fentanyl. The objective of this study was to compare the efficacy of TIDD using bupivacaine/fentanyl vs bupivacaine/hydromorphone in patients with chronic intractable low back pain postlaminectomy. MATERIALS AND METHODS: A retrospective comparative analysis of consecutive patients with lumbar postlaminectomy syndrome who were trialed and later received TIDD with a combination of bupivacaine/hydromorphone or bupivacaine/fentanyl between June 2009 and May 2016 at a single tertiary medical center. RESULTS: We identified a cohort of 58 lumbar postlaminectomy patients receiving a TIDD admixture of either hydromorphone/bupivacaine (30 patients) or low-dose fentanyl/bupivacaine (28 patients) with at least two years of follow-up. The fentanyl group had significantly lower baseline opioid consumption and a lower rate of intrathecal opioid dose escalation. Both groups had similar and significant reductions in pain scores over the two-year follow-up period. No granulomas were observed. CONCLUSION: TIDD using a low-dose fentanyl admixture with bupivacaine in patients with postlaminectomy syndrome and refractory chronic low back pain results in similar pain relief to TIDD with hydromorphone and bupivacaine. Low-dose intrathecal fentanyl leads to a lower rate of opioid escalation and may be safer than hydromorphone.

Effect of Long-Term Intrathecal Bupivacaine Infusion on Blood Pressure.

OBJECTIVES: The local anesthetic bupivacaine is a common analgesic adjuvant medication used in combination with opioids in intrathecal drug delivery systems (IDDSs). While the acute effects of spinal bupivacaine injection on blood pressure (BP) have been studied, there is a dearth of data regarding long-term effects of continuous intrathecal bupivacaine infusion. MATERIALS AND METHODS: A retrospective review of all noncancer pain patients receiving bupivacaine through IDDSs from January 2013 to November 2017 was performed. Blood pressure values before implantation, and after implant at the 1-week, 3-month, 6-month and 1-year time points are recorded as well as corresponding bupivacaine and opioid doses in the IDDS. RESULTS: Eighty-two patients were included in the study; median patient age was 64 years and intrathecal catheter tips were located predominantly in the lower thoracic spine. Significant decreases in systolic blood pressure (SBP) and mean arterial pressure (MAP) relative to baseline occurred in patients receiving chronic lower thoracic intrathecal bupivacaine delivery at 3, 6, and 12 months post-implant (-12.96 ± 18.21; p < 0.001 and - 6.38 ± 12.04; p < 0.001, respectively). The only significant decrease in DBP was observed at 1 year post-implant (-3.09 ± 11.76; p < 0.05). Similar decreases in BP values occurred in patients with or without hypertension. CONCLUSIONS: Long-term thoracic intrathecal infusion of bupivacaine likely exerts a lowering effect on BP, primarily because of a significant decrease in SBP. This effect is likely due to efferent sympathetic blockade by bupivacaine.