Another route of CO2 gas excretion independent of red blood cells in human lungs.

We demonstrated pulmonary arteriolar blood flow-mediated CO2 gas excretion in rabbit lungs. The shear stress stimulation produced CO2 gas in cultured human endothelial cells of pulmonary arterioles via the activation of F1/Fo ATP synthase. To confirm the findings in human subjects undergoing the operation with heart-lung machines, we aimed to evaluate the effects of a stepwise switch, from a partial to a complete cardiopulmonary bypass, of the circulatory blood volume (BV, 100% = 2.4 × cardiac index), on the end-expiratory CO2 pressure (PetCO2), maximal flow velocity in the pulmonary artery (Max Vp), the inner diameter (ID) of pulmonary artery, pulmonary arterial CO2 pressure (P mix v CO2), pulmonary arterial O2 pressure (P mix v O2), hematocrit (Hct), pH, the concentration of HCO3-, and base excess (BE) in mixed venous blood in 9 patients with a mean age of 72.3 ± 3.4 years. In addition, the effects of the decrease in Hct infused with physiological saline solution (PSS) on PetCO2 were investigated in the human subjects. An approximately linear relationship between the PetCO2 and Max Vp was observed. The pumping out of 100% BV produced little or no change in the Hct, pH, P mix v CO2, and P mix v O2, respectively. The hemodilution produced by intravenous infusion of PSS caused a significant decrease in the Hct, but not in the PetCO2. In conclusion, another route of CO2 gas excretion, independent of red blood cells, may be involved in human lungs.

Phrenic Nerve Block at the Azygos Vein Level Versus Sham Block for Ipsilateral Shoulder Pain After Video-Assisted Thoracoscopic Surgery: A Randomized Controlled Trial.

BACKGROUND: Ipsilateral shoulder pain (ISP) is a common problem after pulmonary surgery. We hypothesized that phrenic nerve block (PNB) at the azygos vein level, near the location of the surgical operation, would be effective for reducing ISP. Our primary aim was to assess the effect of PNB on postoperative ISP, following video-assisted thoracic surgery (VATS). METHODS: This prospective, randomized, patient-blinded, single-institution trial was registered at the University Hospital Medical Information Network (UMIN000030464). Enrolled patients had been scheduled for VATS under general anesthesia with epidural analgesia. Patients were randomly allocated to receive infiltration of the ipsilateral phrenic nerve at the azygos vein level with either 10 mL of 0.375% ropivacaine (PNB group) or 0.9% saline (control group) before chest closure. Postoperative ISP was assessed using a numerical rating scale (NRS, 0-10) at rest at 2, 4, 8, 16, and 24 hours. The incidence of ISP was defined as the proportion of patients who reported an NRS score of ≥1 at least once within 24 hours after surgery. In the primary analysis, the proportion of patients with ISP was compared between PNB and control groups using the χ2 test. NRS values of ISP and postoperative incision pain within 24 hours were investigated, as was the frequency of postoperative analgesic use. Incision pain was assessed using an NRS at the time of ISP assessment. Finally, the incidence of postoperative nausea and vomiting and shoulder movement disorders were also evaluated. RESULTS: Eighty-five patients were included, and their data were analyzed. These patients were randomly assigned to either PNB group (n = 42) or control group (n = 43). There were no clinically relevant differences in demographic and surgical profiles between the groups. There was no significant difference in the incidence of ISP (the control group 20/43 [46.5%] versus the PNB group 14/42 [33.3%]; P = .215). The severity of ISP was lower in the PNB group than in the control group (linear mixed-effects model, the main effect of treatment [groups]: P < .001). There were no significant differences between groups in terms of postoperative incision pain. The frequency of postoperative analgesic use was significantly higher in the control group (Wilcoxon rank sum test, P < .001). Postoperative nausea and vomiting did not significantly differ between the 2 groups. There were no changes in the range of shoulder joint movement. CONCLUSIONS: Azygos vein level PNB did not significantly affect the incidence of ISP after VATS.

Phospholipase Cß3 Expressed in Mouse DRGs is Involved in Inflammatory and Postoperative Pain.

BACKGROUND: Previous studies suggested that phospholipase Cß3 (PLCß3), which is a common downstream component in the signaling cascade, plays an important role in peripheral mechanisms of perception including nociception. However, detailed profiles of PLCß3-expressing dorsal root ganglion (DRG) neurons and involvement of PLCß3 in inflammatory and postoperative pain have not been fully investigated. PURPOSE: We evaluated neurochemical char0acteristics of PLCß3-expressing DRG neurons in mice and then we examined the effects of selective knockdown of PLCß3 expression in DRGs on inflammatory and postoperative pain. METHODS: Male C57BL/6-strain mice were used. For the inflammatory model, each mouse received subcutaneous injection of complete Freund's adjuvant (CFA) in the left hindpaw. For the postoperative pain model, a plantar incision was made in the left hindpaw. PLCß3 antisense oligodeoxynucleotide or PLCß3 mismatch oligodeoxynucleotide was intrathecally administered once a day for three consecutive days in each model. The time courses of thermal hyperalgesia and mechanical hyperalgesia were investigated. Changes in PLCß3 protein levels in DRGs were evaluated by Western blotting. RESULTS: Immunohistochemical analysis showed that high proportion of the PLCß3-positive profiles were biotinylated isolectin B4-positive or transient receptor potential vanilloid subfamily 1-positive. PLCß3 protein level in DRGs during CFA-induced inflammation was comparable to that at baseline. Intrathecal administration of PLCß3 antisense oligodeoxynucleotide, which significantly suppressed PLCß3 expression in DRGs, did not affect pain thresholds in normal conditions but inhibited CFA-induced thermal and mechanical hyperalgesia both at the early and late phases compared to that in mismatch oligodeoxynucleotide-treated mice. Intrathecal administration of PLCß3 antisense oligodeoxynucleotide also inhibited surgical incision-induced thermal and mechanical hyperalgesia. CONCLUSION: Our results uncover a unique role of PLCß3 in the development and maintenance of inflammatory pain induced by CFA application and in those of surgical incision-induced pain, although PLCß3 does not play a major role in thermal nociception or mechanical nociception in normal conditions.

Severe mitral regurgitation due to geometric changes in the mitral valve after surgical aortic valve replacement.

BACKGROUND: Severe mitral regurgitation (MR) after aortic valve replacement (AVR) is a serious complication. Although several causes of MR after AVR have been reported, severe MR due to geometric changes in the mitral valve imposed by an aortic valve prosthesis has not been reported. We here report a case of severe MR after AVR that was improved after re-AVR. CASE PRESENTATION: A 77-year-old male underwent elective total aortic arch replacement and AVR. Mild MR was preoperatively identified. After surgery and separation from cardiopulmonary bypass, transesophageal echocardiography (TEE) demonstrated restriction and distortion of the anterior mitral leaflet and severe MR. Displacement of the anterior mitral annulus by the prosthetic aortic valve was strongly suspected to be the cause of MR, which should be surgically restored. Re-AVR using a small-sized valve was then performed. Consequently, the structural changes in the mitral valve were reverted and the MR was reduced. CONCLUSIONS: Geometric changes in the mitral valve induced by an aortic valve prosthesis can cause massive increment of MR. Intraoperative TEE examination of the mitral apparatus is important when severe MR occurs after AVR.

Transversus abdominis plane block with 0.25 % levobupivacaine: a prospective, randomized, double-blinded clinical study.

PURPOSE: Because blood concentrations of local anesthetics sometimes reach toxic levels after transversus abdominis plane (TAP) block, reduction of the dose has been necessary to reduce the risk of systemic toxicity. We therefore investigated the effects of TAP block with 0.25 % levobupivacaine (100 mg) on postoperative pain and measured its plasma concentration after gynecological surgery. METHODS: Forty women undergoing elective open gynecological surgery were randomized to receive bilateral TAP block with 20 ml 0.25 % levobupivacaine on each side (TAP group) or not (non-TAP group) before surgery. Postoperative pain was treated with intravenous patient-controlled analgesia by use of morphine. Patients were evaluated 3 and 24 h after the end of surgery. Visual analog scale (VAS) for pain at rest and with movement, and morphine consumption were recorded. Plasma concentrations of levobupivacaine after TAP block were measured. RESULTS: Three hours after surgery, total morphine consumption was significantly lower in the TAP group (2.8 ± 1.6 mg) than in the non-TAP group (6.4 ± 4.8 mg, P = 0.03). There were no significant differences between VAS in the two groups. Mean plasma concentration of levobupivacaine peaked 10 min after TAP block (0.99 ± 0.43 µg/ml), and the highest concentration was 1.99 µg/ml. CONCLUSION: TAP block with 100 mg levobupivacaine is a safe and efficacious multimodal analgesic regimen for postoperative pain after open gynecological surgery.

[Usefulness of Epidrum for teaching identification of the epidural space].

BACKGROUND: Epidrum (ED) is a device to facilitate the epidural anesthesia procedure. Using ED, we can visually confirm the needle's penetration into the epidural space by collapse of the diaphragm. We investigated the usefulness of ED for teaching identification of the epidural space. METHODS: Forty parturients scheduled for cesarean section were randomly allocated to an ED group or loss of resistance (LOR) group. Epidural anesthesia was performed by residents (operators) under the instruction of advising doctors (observers). In the LOR group, the epidural space was identified by the conventional LOR technique using a glass syringe filled with normal saline. In the ED group, ED was attached to a Tuohy needle and was charged with 1.5 ml of air to expand its diaphragm. Ease of identification of the epidural space was scored by the operator and the observer. The time to identify the epidural space (TI) was recorded. RESULTS: TI in the ED group was significantly shorter than that in the LOR group. ED was superior to LOR for identification of the epidural space not only by operators but also by observers. CONCLUSIONS: The results suggest that ED is a useful device for teaching identification of the epidural space.