Effects of halothane and sodium nitroprusside on renal function and autoregulation

The effects of sodium nitroprusside and halothane on renal autoregulation and kidney function were studied in 14 mongrel dogs at mean arterial pressures of 120, 100, 80, 60 and 40 mm Hg. In group 1, stepwise decreases in mean arterial pressure were achieved by increasing the halothane concentration. In group II, mean arterial pressure was decreased by infusing sodium nitroprusside during halothane anaesthesia. In group I, renal blood flow decreased significantly at mean arterial pressures of 100, 80, 60 and 40 mm Hg. In group II, renal blood flow was well maintained at mean arterial pressures of 100 and 80 mm Hg, but decreased significantly at 60 and 40 mm Hg; at these low pressures flow was greater in group II than in group I. There were no significant differences between two groups in inulin clearance, inulin clearance/renal plasma flow, urine output, urine osmolarity and sodium excretion rate. Significantly larger fractions of cardiac output were distributed to the kidneys in group I.

Failure of bacterial filters to reduce the incidence of pneumonia after inhalation anesthesia

The authors prospectively studied 520 patients undergoing inhalation anesthesia to evaluate the efficacy of low resistance 0.22-micron bacterial filters in preventing postoperative pneumonias. Patients undergoing elective thoracic, upper abdominal and lower abdominal surgeries were randomly assigned preoperatively to filtered and nonfiltered anesthesia circuits by a study nurse. A second study nurse, who was unaware of patient assignments, followed each patient for five postoperative days to identify possible pulmonary complications. Both groups of patients were similar in age, sex distribution, smoking history, prior pulmonary disease, types and duration of surgery, ASA physical status classification, and receipt of intraoperative antibiotics. No differences in rates of postoperative pneumonia were observed between patients assigned to filtered and nonfiltered circuits (16.7 per cent vs. 18.3 per cent, respectively, P = 0.73). Also no differences were observed when the incidences of other outcome criteria such as postoperative fever, abnormal chest x-ray, sputum production, or abnormal pulmonary physical exam findings were evaluated. The results suggest that bacterial gas filters do not influence the incidence of postoperative pneumonias and that routine use of these devices for this purpose is not cost-effective.

Electro-acupuncture modification of halothane anaesthesia in the dog

The effects of electro-acupuncture on minimum alveolar anaesthetic concentration (MAC) was studied during halothane anaesthesia in the dog. Following induction of anaesthesia, MAC was determined in duplicate. Ten dogs then received electro-acupuncture bilaterally at San Yin Chiao for 30 minutes. MAC was determined in duplicate while electro-acupuncture was continued. Electro-acupuncture significantly lowered MAC from 1.2 per cent to 1.0 per cent (p less than 0.01). A crossover experimental design was used in an additional eleven dogs. Here MAC was lowered from 1.17 per cent to 1.04 per cent (p less than 0.05). Electro-acupuncture produces a small but statistically significant reduction in halothane MAC.

Risk factors for postoperative pneumonia

Prospectively studied were 520 patients undergoing elective thoracic, upper abdominal and lower abdominal surgeries to analyze risk factors for postoperative pneumonias. Over-all, pneumonias developed in 91 of the 520 patients studied (17.5 percent). The acquisition of pneumonia was highly associated with preoperative markers of the severity of underlying diseases such as low serum albumin concentrations on admission (P less than 0.005) and high American Society of Anesthesiologists pre-anesthesia physical status classification (P less than 0.0001). History of smoking (P less than 0.001), longer preoperative stays (P less than 0.0001), longer operative procedures (P less than 0.0001) and thoracic or upper abdominal sites of surgery (P less than 0.0001) were also significant risk factors for postoperative pneumonias. Although massive obesity, old age and male sex were also associated with increased incidences of pneumonia, statistical significance was lost when these variables were controlled for site or duration of surgery. We were able to identify risk factors for pneumonia and to define a subpopulation of patients in which the risk of pneumonia was negligible. The acquisition of pneumonia by a low-risk patient should alert the physician to the possibility of a potentially preventable nosocomial infection.

Failure of indomethacin to prevent or ameliorate oleic acid pulmonary edema in the dog

The possibility that prostaglandin synthesis inhibition might favorably inhibit the development of animal adult respiratory distress syndrome models was investigated in two groups of dogs; one group was pretreated with indomethacin 3 mg/kg. Both groups received oleic acid 0.15 mg/kg. Measurements of gas exchange and hemodynamics were performed every hour for 5 hours following embolization. Severe pulmonary edema developed in both groups. The indomethacin pretreated group responded similarly to the control group; there was no difference in the 5 hour course of Pa02 (p = .34), P(A-a)02 (p = .21) or QS/QT (p = .99). Prostaglandin synthesis inhibition did not favorably influence the immediate development of acute respiratory failure following oleic acid.

Epinephrine-induced arrhythmias: effect of exogenous prostaglandins and prostaglandin synthesis inhibition during halothane-O2 anesthesia in the dog

Prostaglandins (PG) modify sympathetic and parasympathetic neurotransmission and have antiarrhythmic properties. Inhibitors of PG synthesis sensitize the heart to certain experimentally induced arrhythmias. This study examined the arrhythmogenic dose (AD) of epinephrine in dogs during halothane-O2 anesthesia as modified by the infusion of PG and by treatment with an inhibitor of PG synthesis. Dogs were anesthetized with 1.25 MAC halothane. The AD of epinephrine was established by a series of 3-minute epinephrine infusions at 10-minute intervals. The AD of epinephrine was then redetermined during infusions of PG(PGE1--1 microgram/kg/min and PGF2 alpha--1 microgram/kg/min), after indomethacin, 3 mg/kg, and after aminophylline, 10 mg/kg. The AD remained unchanged from control during both of the PG infusions and following indomethacin. Only following aminophylline did the AD decrease significantly. Our study suggests that pretreatment of surgical patients with nonsteroidal antiinflammatory drugs which inhibit PG synthesis does not increase the likelihood of ventricular arrhythmias during halothane-O2 anesthesia.

Pharmacokinetics of naloxone and naltrexone in the dog

The serum kinetics of 5 mg/kg of i. v. naloxone or naltrexone were studied in each of two groups of five dogs; serum samples were obtained from 2 min to 2 hr after injection. Serum concentrations were determined by radioimmunoassay. Serum levels of both naloxone and naltrexone fell rapidly; serum half-life during the elimination phase was 71.2 +/- 8.9 min (mean +/- S.E.) for naloxone and 85.1 +/- 9.0 min (mean +/- S.E.) for naltrexone. Although human and dog kinetics are similar for naloxone, naltrexone is long-acting in man, but is quickly dissipated in the dog.

Failure of naloxone and naltrexone to antagonize halothane anesthesia in the dog

The effects of two narcotic antagonists, naloxone and naltrexone, on minimum alveolar anesthetic concentration (MAC) were studied during halothane anesthesia in the dog. Following induction of anesthesia, MAC was determined in duplicate. Each dog was then given one of the two narcotic antagonists and MAC was redetermined in duplicate: five dogs were given naloxone, 3 mg/kg IV, followed by an intravenous infusion of naloxone, 0.025 mg/kg/min; five dogs received naltrexone, 5 mg/kg IV. MAC was unaffected by the narcotic antagonists. Failure of narcotic antagonists to reverse halothane anesthesia suggests that the endogenous opioid peptides are not involved in the anesthetic state produced by halothane.

Management of the mechanically ventilated patient receiving pancuronium bromide

The use of the drug pancuronium bromide occasionally is necessary as a part of the treatment of mechanically ventilated patients. This article reviews the mechanism of drug action, the use of the drug, and the nursing care of the patient receiving pancuronium bromide.

Indwelling pulmonary artery catheters. Their relationship to aspetic thrombotic endocardial vegetations

To assess the incidence of aseptic thrombotic endocardial vegetations (TEV) after pulmonary artery catheterization with Swan-Ganz catheters we reviewed all autopsy reports for a two-year period in our hospital. In 413 autopsies there were five instances of aseptic TEV: 3 in 88 patients with Swan-Ganz catheters, 1 in 120 patients with central venous catheters, and 1 in the 205 patients without central vascular catheters. The incidence of TEV is significantly greater in patients with Swan-Ganz catheters than in other patients.