Advanced Age and Sex Influence Baseline Regional Cerebral Oxygen Saturation as Measured by Near-Infrared Spectroscopy: Subanalysis of a Prospective Study.

OBJECTIVES: The aging brain shows decreased venous oxygenation predominantly in the frontal cortex, which seems sex- dependent. The authors hypothesized that age and sex would influence baseline regional cerebral oxygen saturation (rScO2) measured by the INVOS 5100. DESIGN: Subanalysis of published data. SETTING: Tertiary hospital. PARTICIPANTS: A total of 1,616 adults undergoing cardiac interventions. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Baseline rScO2 was recorded at room air and calculated as mean of the left and right rScO2. Patients were divided into 3 groups: 18- to- 49 years: young; 50- to- 74 years: middle-aged; and ≥75 years: elderly. The rScO2 was significantly different in the middle-aged (63 [56-69]) compared with the young participants (67 [59-74]; p < 0.001) and elderly participants (60 [55-66]; p < 0.001]. Women were significantly older compared with men (72 [62-79] v 66 [56-74]; p < 0.001]) and showed lower hemoglobin values (p < 0.001) and lower rScO2 (58 [52-63] v 65 [58-70]; p < 0.001]). Multiple regression analysis revealed age, sex, and hemoglobin as significant determinants of rScO2: 26.665 - (0.030 × age) + (2.581 × hemoglobin) + (2.799 × 0 for female sex). CONCLUSIONS: Baseline rScO2, as measured by the INVOS 5100, decreases with advanced age and is lower in women. New definitions of cerebral oxygen desaturation need to be analyzed in future trials that will evaluate neurologic outcome in the aging population or in women.

The use of patient-specific instruments does not reduce blood loss during minimally invasive total knee arthroplasty?

PURPOSE: Blood loss can be substantial and will influence morbidity and mortality after total knee arthroplasty. This study evaluated whether patient-specific instruments (PSI) can reduce blood loss because the intramedullary canal is not opened during the procedure and whether hidden blood loss can be reduced by its use. METHODS: Seventy-five patients operated with the Signature PSI technique were compared with a matched group operated with conventional instruments. Maximal drop in haemoglobin (Hb) and hematocrit (HTC) level were compared at day 2 and day 4. Transfusions were noted. Clinical outcomes like range of motion and knee society scores were studied as secondary outcomes. RESULTS: No statistically significant difference for calculated blood loss, maximal drop in Hb or HTC and transfusions were found. No clinical differences in range of motion or knee society scores were observed. CONCLUSIONS: The use of PSI-assisted total knee arthroplasty (TKA) did not result in less blood loss compared with conventional minimally invasive TKA with tourniquet. No reduction in hidden blood loss was observed either. According to this study, the argument of reduced transfusion cost should not be used in cost-effectiveness calculations of PSI-assisted TKA. LEVEL OF EVIDENCE: III.

Pain trajectories identify patients at risk of persistent pain after knee arthroplasty: an observational study.

BACKGROUND: Persistent postsurgical pain is a major source of dissatisfaction after knee arthroplasty. Postoperative pain trajectories allow a dynamic view of pain resolution after surgery and might help to identify patients at risk for persistent pain. QUESTIONS/PURPOSES: In this prospective observational study, we examined the relationship between postoperative pain trajectories and persistent pain, specifically neuropathic pain, at 3 months after knee arthroplasty. METHODS: Over a 1-year period, all patients undergoing elective unilateral knee arthroplasty for osteoarthritis by one surgeon were invited to participate in the study, provided they had not had prior knee surgery and their American Society of Anesthesiologists grade was 3 or lower; 128 patients fulfilled these criteria. Patients filled in a diary questioning postoperative pain at rest and during mobilization and maximal pain from Day 1 until Day 8 after surgery. At 3 months, the patients were questioned concerning the presence of persistent pain and its nature and intensity using the Douleur Neuropathique 4 [Neuropathic Pain 4] and Brief Pain Inventory questionnaires. At 3 months, 112 of the 128 patients (87%) were successfully contacted. RESULTS: At 3 months, 47 of the 112 (42%) patients were totally pain free and 65 (58%) reported persistent pain at the surgical site. Among the latter, 12 patients (11%) presented with a neuropathic component and more severe persistent pain. Pain trajectories highlighted higher acute pain scores for maximal pain (from Day 1 until Day 8) and for pain at mobilization (from Day 3 until Day 8) in patients with neuropathic persistent pain (p < 0.05 at all time points compared with the no persistent pain group). CONCLUSIONS: Postoperative pain trajectories constructed from patient's pain diary suggest that a subgroup of patients who will present with higher pain at 3 months after knee arthroplasty might be identified early in the postoperative period and might benefit from preventative treatment. LEVEL OF EVIDENCE: Level III, diagnostic study. See Instructions for Authors for a complete description of levels of evidence.

Pain after knee arthroplasty: an unresolved issue.

PURPOSE: Despite the recent advances in the understanding of pain mechanisms and the introduction of new drugs and new techniques in the postoperative management, pain after total knee arthroplasty (TKA) is still an unresolved issue. It affects the quality of life and rehabilitation of an important percentage of patients undergoing TKA. The aim of this narrative review was to give an overview on pain mechanisms and multimodal pain management. METHODS: A review of all peer-reviewed articles on pain after knee arthroplasty was performed by two reviewers. Recent articles on incisional pain mechanisms were included because of their importance in the understanding of postsurgical pain. Search was performed in Pubmed, Cochrane and Google Scholar data bases. RESULTS: Postsurgical pain mechanisms are based on both local and systemic inflammatory reactions. Peri-operative pain management starts with the anaesthetic technique and resides on a multimodal analgesia regimen. New concepts, drugs and techniques have shown their efficacy in reducing the severity of acute postoperative pain and the risk of developing chronic pain after TKA. CONCLUSION: This narrative review offers a clear overview of pain mechanism after knee arthroplasty and an understanding on how multimodal pain management can reduce the intensity and duration of pain after knee arthroplasty.

C-reactive protein (CRP) in different types of minimally invasive knee arthroplasty.

PURPOSE: C-reactive protein (CRP) is an acute-phase biomarker responding to surgical trauma. Typically, a first peak is observed at day 2 with a reduction at day 4 and normalization 3-6 weeks after surgery. CRP is often linked to prosthetic joint infection when elevated values are present longer time after surgery. The aim of this study was to analyse the kinetics of CRP in different types of minimally invasive (MI) arthroplasty and to observe if there were significant differences in between MI total knee arthroplasty (TKA), patient-specific instruments (PSI) TKA and unicompartmental arthroplasty (UKA). MATERIALS AND METHODS: Three hundred and seventy-two patients were prospectively studied with a blood test measuring CRP at day 2, 4, 21 and 42 in 3 different groups of patients: 257 MI TKA, 55 PSI TKA and 60 UKA. Mean peak values and kinetics were compared in between different groups of MI arthroplasty. RESULTS: There was a significant age difference in the three MI arthroplasty groups. The difference in mean age for the conventional MI TKA group of 68.8 ± 9.8 years, 58.5 ± 11.7 years for the unicompartmental group (P < 0.05) and 63.3 ± 9.6 years for the PSI group (P < 0.05) was significant. Mean CRP level, for the entire study group, on day 2 was 16.7 ± 8.8 mg/dl that gradually decreased to 13.6 ± 7.8 mg/dl on day 4. On day 21 and 42, median CRP level was 0.6 (0-20) and 0.4 (0-7) mg/dl, respectively. Peak CRP values were lower for UKA compared to TKA at day 2 (11.6 vs. 17.5 mg/dl) and day 4 (8.0 vs. 15 mg/dl), but this was not observed for PSI-assisted arthroplasty (18.9 vs. 17.5 mg/dl). There was a trend for faster CRP normalization in UKA compared to the two other groups at day 21 and at day 42 and for PSI TKA to have a lower mean level at 4 days (12.9 vs. 15 mg/dl). There was no statistical difference in the normalization rate of PSI-assisted versus MI TKA. CONCLUSION: Kinetics of CRP in MI arthroplasty are identical to the published kinetics of conventional TKA. Most patients normalize CRP at 3 weeks; however, 18 % does not by 6 weeks. This is not a sign of early prosthetic joint infection. Peak values are significantly lower for UKA but not for PSI TKA.

Dynamic view of postoperative pain evolution after total knee arthroplasty: a prospective observational study.

BACKGROUND: Having a dynamic view of postoperative pain resolution allows a better understanding of the transition towards chronic pain. Sleep and quality of life are important determinants of satisfaction after total knee arthroplasty (TKA), besides functional recovery and pain. METHODS: For 114 patients undergoing TKA we recorded the presence of pain at rest, pain evoked at movement and pain located at the incision site in the acute (postoperative day 1, 2, 3, 8), subacute (30 days, 3 months) and chronic (6 months and 1 year) period. Analgesics consumption and need of medical assistance for pain were questioned. Quality of life measured by the impact on enjoyment of life, sleep and mood were monitored. RESULTS: Average incidence for subacute pain was 54% at rest, 66% at mobilization. For chronic pain, the incidence was 14% at rest, 22% during mobilization. Pain at rest peaked at day 30 while pain during mobilization displayed a plateau between day 8 and 3 months. Three per cent of the patients complained at 1 year of pain at the incision site. 11% of patients still took analgesics one year after the surgery. More than 40% of patients reported moderate to severe alterations of sleep and quality of life in the acute period, decreasing to less than a half at one year. CONCLUSIONS: The trajectories of the different types of pain after TKA show their non-linear evolution, highlighting the need of a better pain control at precise moments. Sleep disturbances and alterations of quality of life are still present one year after the surgery.

New concepts in acute pain management: strategies to prevent chronic postsurgical pain, opioid-induced hyperalgesia, and outcome measures.

Chronic postsurgical pain (CPSP) is a pain syndrome that has attracted attention for more than 10 years. CPSP is a pain syndrome that develops postoperatively and lasts for at least 2 months in the absence of other causes for pain (eg, recurrence of malignancy, chronic infection, and so forth). Pain continuing from a preexisting disease is not considered as CPSP. In this article, the authors discuss the etiopathogenesis of CPSP and interventions that can help prevent and treat this condition.

Use of dexmedetomidine for pain control.

For many years, clonidine, an α2-adrenergic receptor (α2-AR) agonist, has been widely used as an analgesic adjuvant in perioperative conditions and pain therapy. Dexmedetomidine (DMET) is currently the most potent α2-AR agonist available and was first approved as a sedative agent for use in the intensive care unit. However, DMET has recently been investigated for its analgesic effects and has the potential to become an alternative to clonidine.