A Quantile Regression Approach to Estimating the Distribution of Anesthetic Procedure Time during Induction.

Although procedure time analyses are important for operating room management, it is not easy to extract useful information from clinical procedure time data. A novel approach was proposed to analyze procedure time during anesthetic induction. A two-step regression analysis was performed to explore influential factors of anesthetic induction time (AIT). Linear regression with stepwise model selection was used to select significant correlates of AIT and then quantile regression was employed to illustrate the dynamic relationships between AIT and selected variables at distinct quantiles. A total of 1,060 patients were analyzed. The first and second-year residents (R1-R2) required longer AIT than the third and fourth-year residents and attending anesthesiologists (p = 0.006). Factors prolonging AIT included American Society of Anesthesiologist physical status ≧ III, arterial, central venous and epidural catheterization, and use of bronchoscopy. Presence of surgeon before induction would decrease AIT (p < 0.001). Types of surgery also had significant influence on AIT. Quantile regression satisfactorily estimated extra time needed to complete induction for each influential factor at distinct quantiles. Our analysis on AIT demonstrated the benefit of quantile regression analysis to provide more comprehensive view of the relationships between procedure time and related factors. This novel two-step regression approach has potential applications to procedure time analysis in operating room management.

No enlargement of the right internal jugular vein of the dialysis patients in the Trendelenburg position.

BACKGROUND: The Trendelenburg position has been suggested for right internal jugular vein (RIJV) catheterization. However, this position can sometimes be functionally intolerable for chronic kidney disease patients. We conducted an ultrasound study to further investigate the efficacy of the use of the Trendelenburg position during tunneled dialysis catheter insertion via the RIJV in chronic kidney disease patients. METHODS: We recruited into our study patients without a history of prior tunneled dialysis catheter insertion or neck surgery. Those patients with stenosis or thrombus in the RIJV were excluded. Serial ultrasound images were acquired with patients in the supine position, with the head rotated 30° to the left: Stage 0, table flat; Stage T, Trendelenburg tilt. Then, measurements of patient RIJV transverse diameter, anteroposterior (AP) diameter, and cross-sectional area (CSA) were obtained. RESULTS: Fifty dialysis patients and 40 healthy volunteers completed the study. There were no significant differences in the lateral diameter, AP diameter, or AP/lateral diameter ratio between the dialysis patients and healthy volunteers, whether in the supine or the Trendelenburg position. However, the CSA of the RIJV of the healthy volunteers in the Trendelenburg position was significantly larger than that in dialysis patients. The change in CSA from the supine to the Trendelenburg position was also significantly different between the two groups. CONCLUSION: In contrast to healthy volunteers, there was no enlargement of the RIJV when dialysis patients were in the Trendelenburg position. The reason for this phenomenon may be multifactorial, with diastolic dysfunction being the most likely cause, and further investigation is required to clarify the cause. Our investigation suggests that the supine position for central venous catheterization in dialysis patients is superior to the Trendelenburg position.

Effect on pain relief and inflammatory response following addition of tenoxicam to intravenous patient-controlled morphine analgesia: a double-blind, randomized, controlled study in patients undergoing spine fusion surgery.

OBJECTIVE: This study tested the hypothesis that adding tenoxicam (T) to intravenous patient-controlled analgesia (IV-PCA) with morphine (M) would improve postoperative pain relief and wound inflammatory responses compared with M alone after spine surgery. DESIGN: Randomized, prospective, double-blind, controlled study. SUBJECTS: Ninety-four patients eligible for elective spine surgery. SETTING: Teaching hospital. METHODS: Patients were randomized to one of three groups: the M group (PCA regimen with M), the TM group (PCA regimen with T and M), or the T+TM group (20 mg T administered 30 minutes before wound closure in addition to the TM regimen). The primary end point was the numeric rating scale score for pain intensity, and secondary end points pertaining to postoperative pain management included M consumption, PCA demand/delivery, use of rescue analgesics, adverse events, and levels of inflammatory mediators in wound drainages. RESULTS: PCA demand was reduced in both the TM and T+TM groups compared with the M group (both P ≤ 0.001). The incidence of skin itching was significantly reduced in the T+TM group compared with the other groups (both P ≤ 0.05). PGE2 and interleukin-6 levels in wound drainages were reduced in the TM and T+TM groups compared with the M group (both P ≤ 0.001). CONCLUSIONS: The combination of T and M for IV-PCA was not more efficacious than IV-PCA with M alone in reducing postoperative pain after spine surgery but reduced PCA demand and suppressed local inflammation at the surgical site. Administration of T before wound closure may ameliorate IV-PCA M-induced skin itching.

Dexamethasone prevents postoperative nausea and vomiting: benefit versus risk.

Postoperative nausea and vomiting (PONV) is a common annoying experience after surgery. The overall incidence of PONV in adults is 20-30%; the incidence rate in patients of high-risk groups can be as high as 70-80%. Children are not exempted from attacking either; the incidence rate in children above the age of 3 is more than 40%. The incidence slowly drops after puberty, sharing the same rate with adults. Dexamethasone can be effective in preventing PONV in adults and children. Compared with other preventive medications, dexamethasone has equal or even better efficacy in reducing the incidence of PONV and has the advantages of low cost and longer effectiveness as well. Although the action mechanism of dexamethasone is hitherto not fully understood, animal studies have confirmed that the vomiting center in the brain stem plays a central role. A combination of dexamethasone with other antiemetics is more effective than any single drug alone. Additionally, the use of dexamethasone to prevent nausea and vomiting triggered by intravenous or epidural morphine for pain control can also offer a good therapeutic effect. To date, clinically, dexamethasone as a preventative drug against PONV has not caused fatal outcome; therefore, it is generally considered to be an effective and safe antiemetic. Nevertheless, its use in this regard may lead to adverse effects, principally postoperative hyperglycemia and infection.

Evaluation of the relationships between intravenous patient-controlled analgesia settings and morphine requirements among patients after lumbar spine surgery.

BACKGROUND: To evaluate the association between daily morphine requirement and the intravenous patient-controlled analgesia (IVPCA) setting in patients undergoing spinal surgery. METHODS: We conducted a retrospective analysis of 179 patients of American Society of Anesthesiologists physical status class I-III who underwent elective posterior lumbar spinal surgery and consented to IVPCA for postoperative pain control. The regi-mental solution contained morphine 1 mg/mL. The IVPCA program was set to deliver a priming dose of 1.5-4 mL, a basal infusion rate of 0-1.2 mL/hr, and a 0.5-1.5 mL bolus on demand with a 5-minute lockout interval. Demographic data, surgical procedures, analgesia program setting variables, 4-hour cumulative morphine dose and 11-point numeric rating scale for pain on postoperative days 1 and 2 were collected for comparison. RESULTS: The IVPCA requirement decreased gradually over time (p < 0.001). The number of vertebrae involved significantly influenced the daily morphine requirements (p = 0.01). None of the IVPCA settings, including continuous infusion, affected daily morphine requirements. On average, the analgesic requirement on postoperative day 2 was 18% less than that on postoperative day 1. CONCLUSION: The number of vertebrae involved was significantly associated with the daily IVPCA requirement. The IVPCA settings, including priming dose, basal infusion rate and bolus dose, did not affect the daily morphine requirements.

Severe carbon dioxide retention during second laparoscopic surgery for urgent repair of an operative defect from the preceding laparoscopic surgery.

A 61-year-old male patient underwent laparoscopic cholecystectomy on diagnosis of acute cholecystitis. Thirteen hours later, bile leakage was noted and a second laparoscopic surgery was performed to rectify this. Severe hypercapnia and acute respiratory acidosis occurred during the act of CO2 pneumoperitoneum. The accumulated CO2 could not be eliminated effectively in spite of deliberate adjustment of the respiratory parameters. We suspected that abnormally high CO2 absorption, which outweighed the capability of physiologic elimination in the presence of acute peritonitis, was the cause of the severe CO2 retention in the second laparoscopic surgery. The patient remained intubated with mechanical ventilatory support after surgery. Excessive internal CO2 was washed out gradually and the patient was extubated successfully the next morning. Profound inflammatory responses in peritonitis may increase permeability and absorption of CO2. Hypercapnia can occur as the store of CO2 in the tissues is saturated and there is continuous inflow of external CO2. It usually takes several hours to achieve a steady state of CO2 elimination after desufflation of CO2 pneumoperitoneum and mechanical ventilatory support may sometimes be needed. In conclusion, caution should be taken against hypercapnia and respiratory acidosis in patients with peritonitis undergoing laparoscopic surgery because of the likelihood of these events occurring during the procedure.

Paradoxical carbon dioxide embolism during pneumoperitoneum in laparoscopic surgery for a huge renal angiomyolipoma.

We present a case of paradoxical gas embolism during CO2 insufflation in laparoscopic nephrectomy for a huge renal angiomyolipoma. Paradoxical CO2 embolism in the left heart chambers without demonstrable intracardiac right-to-left shunt was detected by transesophageal echocardiography (TEE). The surgical procedure was stopped immediately, but the patient recovered with mild neurologic deficit. We speculate that rapid pneumoperitoneum introduction pushed CO2 into the abnormal vasculature of the angiomyolipoma, which communicates with the systemic vascular system, causing pseudoaneurysm formation. Follow-up abdominal computed tomography showed a new pseudoaneurysm inside the tumor. If intracardiac right-to-left shunt is excluded for the reason of paradoxical gas existence, there remains extracardiac right-to-left shunt, with transpulmonary passage of the venous emboli being the most likely mechanism. In fact, the cause of paradoxical gas embolism in this case remains unknown. Therefore, laparoscopic surgery for huge angiomyolipoma should be performed with extreme caution; an open procedure may be considered as an alternative.