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Biomedical subjects

N L Pace

Publications and source records attributed to N L Pace.

At least 91 records · Page 5Linked to original sources
PubMed1983

Differential lung ventilation after unilateral hydrochloric acid aspiration in the dog.

Differential lung ventilation (DLV) may be necessary in the supportive care of patients with severe unilateral or asymmetrical lung disease. The best method for allocating tidal volume between the 2 lungs is unknown. Eighteen mongrel dogs were given a unilateral hydrochloric acid (HCI) aspiration injury. A computer-controlled differential lung ventilation system was used to ventilate 6 dogs with equal volumes in each lung, 6 dogs with equal end-inspiratory pressure in each lung, and 6 dogs with equal end-tidal CO2 fraction in each lung. The computer allocated volume between the 2 lungs by these 3 schemes on a breath-by-breath basis and maintained PaCO2 at 35 torr and total tidal volume at 15 ml/kg. Oxygen tension fell and pulmonary venous admixture increased after aspiration. There were no differences in gas exchange among the groups. Without PEEP, differential partitioning of tidal volume is of little consequence in differential lung ventilation of asymmetrical injuries.

Animals↗
PubMed1983

Synchronous versus asynchronous differential lung ventilation with PEEP after unilateral acid aspiration in the dog.

Differential lung ventilation (DLV) with PEEP has been used to oxygenate patients with severe unilateral or asymmetrical lung disease. Many different ventilator systems have been used to deliver DLV, but the question of whether or not to synchronize the ventilation of the 2 lungs has not been answered. Twelve mongrel dogs were given a unilateral hydrochloric acid (HCl) injury and divided into 2 groups, one receiving synchronous and the other receiving asynchronous DLV. The assignment of synchronization and side of injury was allocated randomly. A computer-controlled DLV system was used to ventilate the dogs with equal tidal volumes to each lung. The respiratory rate was feedback controlled to maintain PaCO2 at 35 torr. After injury, 10 cm H2O of PEEP was applied to the injured lung and the dogs were ventilated with FIO2 = 0.40 for 4 h. There was no statistically significant difference in gas exchange ([PaO2, Qva/Qt, PaCO2, P(A-a)O2] or hemodynamics [mean arterial pressure (MAP), CVP, mean pulmonary arterial pressure (MPAP), mean pulmonary arterial wedge pressure (WP), cardiac output in triplicate (Q), heart rate (HR)] between the 2 groups. With this particular model, there is no need to synchronize the 2 ventilators when using DLV with unilateral PEEP.

Animals↗
PubMed1983

Ketanserin prevents platelet aggregation and endotoxin-induced pulmonary vasoconstriction.

Pulmonary hypertension secondary to sepsis is due, in part, to release of serotonin from platelets. This study examines the effects of ketanserin, a new, highly specific serotonin antagonist, on platelet aggregation and the cardiovascular changes associated with bacterial endotoxemia in dogs. Ketanserin markedly inhibits in vitro platelet aggregation induced by mixing serotonin and epinephrine. When ketanserin is administered to animals before endotoxin infusion, cardiac output is greater and mean pulmonary artery pressure (MPAP), pulmonary and systemic vascular resistance (PVR and SVR) and arteriovenous oxygen content difference [C(a-v)O2] are less than in animals not receiving ketanserin. Similar results for PVR, SVR, and C(a-v)O2 are obtained when ketanserin is administered after endotoxin infusion. The data indicate that ketanserin inhibits serotonin-induced platelet aggregation and modifies many cardiovascular changes associated with bacterial endotoxemia.

Animals↗
PubMed1983

The effect of ketanserin, a specific serotonin antagonist, on burn shock hemodynamic parameters in a porcine burn model.

A number of vasoactive substances, including serotonin, have been implicated in the pathophysiology of burn shock. Ketanserin, a specific serotonin antagonist, was investigated in a porcine burn shock model. Fifteen swine were given a mean 44% total body surface area full-thickness scald burn and received fluid resuscitation with Ringer's lactate for 24 hours postburn. The swine were divided into three groups: Group I (control group) received no ketanserin; Group II received ketanserin as a single intramuscular dose preburn and continuously via intravenous drip postburn; and Group III received ketanserin continuously via intravenous drip postburn only. The ketanserin-treated groups demonstrated improved cardiac index, decreased pulmonary artery pressures, and smaller arteriovenous oxygen content differences compared to the control group in the early postburn period. Ketanserin should be investigated further as a possible adjunctive therapeutic agent during burn shock resuscitation.

Animals↗
PubMed1983

Differential lung ventilation with unilateral PEEP following unilateral hydrochloric acid aspiration in the dog.

Differential lung ventilation with positive end expiratory pressure (PEEP) improves pulmonary gas exchange when used in the supportive care of patients with severe unilateral or asymmetrical lung disease. Once the provision of selective PEEP to the two lungs is accomplished, the best method of partitioning the tidal volume between the two lungs is unknown. Twelve mongrel dogs were given a unilateral hydrochloric acid (HCl) aspiration injury. A computer controlled differential lung ventilation system was used to ventilate four dogs with equal volumes to each lung, four dogs with equal driving pressure (end inspiratory pressure-PEEP) to each lung, and four dogs with equal end-tidal CO2 fraction from each lung. The respiratory rate was feedback controlled to maintain PaCO2 at 4.67 kPa. The dogs were kept supine and ventilated with 30% O2. Following injury, the PEEP was set at 0 kPa for 1 h. The dogs were then given 1.36 kPa and 2.72 kPa PEEP to the injured lung for 2 h in a cross-over fashion. The assignment of the tidal volume controller, the side of injury, and the PEEP sequence was random. Oxygen tension fell and pulmonary venous admixture increased after giving the HCl injury. In all three groups considered simultaneously, unilateral PEEP improved PaO2 and venous admixture. The equal tidal volume distribution was the only group to show a significant improvement in PaO2 at both PEEP increments (0 to 1.36 kPa and 2.72 kPa). There was a significant difference in tidal volume allocation between the three groups with the equal end-tidal and equal pause pressure groups only minimally ventilating the injured lung.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1983

Narcotic dosage and central nervous system opiate receptor binding.

Increasing doses of lofentanil (0, 0.08, 0.16, 0.31, 0.63, 1.25, 2.50, 5.00, and 10.0 micrograms/kg), a potent long-acting narcotic, were administered intravenously to rats to examine the relationship among narcotic dosage, degree of analgesia (inhibition of tail withdrawal reflex), anesthesia (no response to bone-crush injury), and central nervous system (CNS) opiate-receptor occupancy (inhibition of [3H] sufentanil binding). Our results demonstrate that increasing doses of lofentanil produce increasing analgesia and anesthesia and eventually complete opiate receptor occupancy. Analgesia occurs with doses of lofentanil (0.31 micrograms/kg) that result in levels of CNS opiate-receptor binding too low to be measured and anesthesia occurs with doses of lofentanil (1.25 micrograms/kg) that produce occupancy of about 25% of the available opiate receptors in subcortical areas and cortex. These findings in rats cannot be applied to narcotic usage in humans, but the data do indicate that in rats a dose eight times the anesthetic dose of lofentanil is needed to saturate virtually all available CNS opiate receptors (10.0 micrograms/kg). Whether saturation of most or all available CNS opiate receptors during narcotic anesthesia is of clinical importance remains to be determined.

Analgesia↗
PubMed1982

Failure of narcotic antagonist to alter electroacupuncture modification of halothane anaesthesia in the dog.

Sixteen dogs were used to study the analgesic effects of electroacupuncture. Electroacupuncture lowered halothane MAC significantly (1.21 +/- 0.04 to 1.05 +/- 0.05 per cent, p less than 0.005). Reversibility of this effect by narcotic antagonist was then studied, using naltrexone 5 mg . kg-1 injected intravenously (10 dogs) or 0.5 mg . kg-1 intrathecally (3 dogs). We failed to see any reversal of the effect of electroacupuncture on MAC. Narcotic antagonist reversibility of acupuncture effect is taken currently to imply endorphin mediation. Possible explanation for our result include an electroacupuncture analgesia not mediated by endorphins.

Acupuncture Therapy↗
PubMed1982

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.

Animals↗
PubMed1981

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.

Acupuncture Therapy↗
PubMed1981

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.

Adult↗
PubMed1981

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.

Anesthesia, Inhalation↗
PubMed1980

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.

Animals↗