Takao Yamanoue

Usefulness of transesophageal echocardiography for guiding pulmonary artery catheter placement in the operating room

SummaryThe usefulness of transesophageal echocardiography (TEE) for guiding the placement of a pulmonary artery (PA) catheter was evaluated in 31 patients (TEE group); 31 patients who were treated before TEE guidance was used (control group). In the control group, use of the PA catheter was abandoned in two patients; because of an unstable condition and marked arrhythmias, respectively. The key findings for TEE guidance were: (1) pulsatile to-and-fro movement of the balloon, i.e., “shuttle movement” and (2) loss of shuttle movement at wedging of the balloon, i.e., “anchoring sign.” When the PA catheter did not enter the right vertricle (RV), the balloon was found to be in the inferior vena cava or the right atrium (RA) without shuttle movement. Coiling of the catheter was suggested in the latter situation. Coiling also occurred in the RV, often associated with frequent arrhythmias. These findings indicate that the catheter should be withdrawn once. TEE allowed for readjustment of the catheter tip position by enabling the balloon to be wedged twice. An excessively deep placement of the catheter tip was seen in 5 of the controls, but in none of the TEE group. Biplane TEE was found to be advantageous for guiding PA catheter placement and for visualizing the RV inflow and outflow tract in a single view, with the shuttle movement of the balloon in its long axis. TEE acts as an “eye” in the operating room, as does fluoroscopy, enabling smooth placement of the PA catheter.

Pharmacokinetics and pharmacodynamics of once-daily arbekacin during continuous venovenous hemodiafiltration in critically ill patients

This study examined the pharmacokinetics of arbekacin during continuous venovenous hemodiafiltration (CVVHDF) and assessed the pharmacodynamics to consider arbekacin dosage adaptation in CVVHDF. Arbekacin was administered by 0.5-h infusion once daily, using a polymethyl methacrylate membrane hemofilter, to three critically ill patients undergoing CVVHDF; the flow rates were 0.8 l/h for the filtrate and 0.6 l/h for the dialysate. The drug concentrations in plasma and in the filtrate-dialysate were determined using a fluorescence polarization immunoassay and analyzed pharmacokinetically. The average sieving coefficient of arbekacin was 0.739 and the average drug clearance by CVVHDF was 1.03 l/h. A pharmacokinetic model with three compartments (1, central; 2, peripheral; 3, filtrate-dialysate side hemofilter) accurately reflected the concentration-time data for both plasma and filtrate-dialysate. The pharmacokinetic model assessed the pharmacodynamic profile of arbekacin once-daily regimens (0.5-h infusions) at filtrate-dialysate flow rates of 1.4 and 2.8 l/h, and demonstrated that only the 150-mg and 200-mg regimens achieved an effective target range for Cmax (9–20 µg/ml), suggesting that empirical dosages lower than the usual 150–200 mg should be avoided in patients undergoing CVVHDF. The minimum regimens needed to achieve an effective pharmacodynamic target for the free Cmax/MIC ratio (>8) were 75 mg for an MIC of 0.5 µg/ml, 200 mg for an MIC of 2 µg/ml, and 400 mg for an MIC of 4 µg/ml. These results will help us to better understand the pharmacokinetics of arbekacin during CVVHDF, while also helping in the selection of the appropriate arbekacin regimens, based on a pharmacodynamic assessment, for patients receiving this renal replacement therapy.

Cardiac arrest after mesenteric manipulation in a patient undergoing abdominal surgery

A 55-yr-old, 72-kg man with both gastric and rectosigmoidal tumors was scheduled for rectosigmoidectomy. He was not taking medication, nor did he have a history of allergic reaction. Preoperative laboratory examinations were normal. After premeditation with 3 mg of bromazepam as suppository, anesthesia was induced with thiamylal200 mg, fentanyl 200 pg, and vecuronium 8 mg intravenously (IV) and was maintained with sevoflurane and nitrous oxide in oxygen. The surgery proceeded uneventfully, and the tumor was resected. Mesenteric manipulation was performed for abdominal lavage with warm saline at the end of surgery. Just after this procedure, ventricular premature beat appeared, systolic arterial pressure decreased from 102 to 58 mm Hg, and heart rate slowed from 72 to 48 bpm with ST segment elevation by 12 mm on heart monitor (Figure 1). Immediately, 12 mg of ephedrine and 0.5 mg of atropine were given, but cardiac arrest occurred. External cardiac massage and electric countershock resuscitated the patient. When the surgical dressings were removed after surgery, large dermal flares were observed on the trunk and extremities, but there were no respiratory symptoms. Blood samplings were taken to measure serum levels of histamine and mast cell tryptase (Tryptase RIACT kit; Pharmacia, Uppsala, Sweden); their normal ranges are 1.14 -C 0.40 nmol/L and less than 2.0 U/L, respectively (Figure 2). To determine whether anaphylactic reaction or mesenteric manipulation was responsible, dermal prick test and in vitro histamine release test were performed (Hollister-Stier, West Haven, CT) using all agents given before cardiac arrest; saline, thiamylal, fentanyl, vecuronium, chlorhexidine, lactated Ringer’s solution, and hydroxyethylated starch for dermal prick test and for in vitro histamine release test

Enzyme inhibition by analgesic and hypnotic agents on anaerobic dehalogenation of halothane.

Enzyme inhibition on anaerobic dehalogenation of halothane by various analgesic or hypnotic agents was investigated in vitro using rat liver microsomal fraction. The production rate of chloro-difluoro-ethylene (CDE) and chloro-trifluoroethane (CTE), anaerobic metabolites of halothane, was measured when various concentrations of analgesic or hypnotic agents (fentanyl, morphine, pentazocine, buprenorphine, ketamine, diazepam, chlorpromazine and hydroxyzine) were supplemented. Inhibitor constant (Ki) of each agent was calculated and compared with each other. The activity of NADPH-cytochrome c reductase (fp2) and NADH-ferricyanide reductase (fp1) was measured when each agent was added. The values of inhibitor constants (Ki) for CDE and CTE formation were in the following order from large to small values; morphine (656 μM and 2570 μM), chlorpromazine (49.7 μM and 68.1 μM), ketamine (24.9 μM and 64.4 μM), fentanyl (23.9 μM and 34.6 μM), hydroxyzine (19.2 μM and 50.8 μM), diazepam (17.0 μM and 13.9 μM), buprenorphine (11.2 μM and 22.4 μM), and pentazocine (1.96 μM and 6.67 μM) respectively. Pentazocine inhibited the formation of CDE 300 fold greater than morphine. The activity of fp2 and fp1 did not change by the addition of these analgesic or hypnotic agents. These results indicate that various analgesic or hypnotic agents, which are commonly used with halothane in clinical anesthesia, suppress the anaerobic dehalogenation of halothane in vitro. They also imply that the suppression of production of halothane metabolites is the result of direct enzyme inhibition on cytochrome P-450, since these agents did not affect the activity of fpz and fPI which are flavoproteins existing in the microsomal electron transport system.

Surgical management of patients on hemodialysis undergoing emergency operations.

透析患者緊急手術に対する対策を考察するため, 最近の開腹術症例20例 (待期手術12例, 緊急手術8例) を選択してスワンガンツ・カテーテルを用いた循環動態の変化を中心に検討した. 待期手術の場合, 術前の除水によって心係数 (Cl) は正常下限まで低下したが, その後は改善, 肺動脈拡張期圧 (PADP) の変化はまったくみられず安定した心機能状態を保っていた. 一方, 緊急手術では, 術前の不十分な除水と重篤な病因のため術前PADPが上昇しており, 手術による病因の除去により術後は正常に回復したが, 術後Cl, PADPとも徐々に上昇し心負荷の増加傾向を示した。 術中の輸液バランスは待期手術では3ml/kg/hrであるのに対し, 緊急手術では4.6ml/kg/hrと多くなっていた. 術後透析は緊急手術で14.6±3.2時間と待期手術29.3±12.6時間に比して有意に早期に施行された. 以上より緊急手術の場合, 次のような点に留意すべきであると考えられた.1. 可能な限り術前緊急透析を行う, 2. 循環動態のモニターとそれに基づく輸液量の設定, 3. 手術によるできるだけ早急な病因の除去, 4. 術後早期の透析, 以上を考慮しながら, 透析患者緊急手術に対処していかなければならない.