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Biomedical subjects

P S Colley

Publications and source records attributed to P S Colley.

At least 19 recordsLinked to original sources
PubMed1990

Nitrous oxide: suppression of focal epileptiform activity during inhalation, and spreading of seizure activity following withdrawal.

Intraoperative brain surface electrocorticography (ECoG) is an integral part of the surgical excision of epileptogenic foci. If surgical excision is performed under general anesthesia, anesthetics should be selected that do not seriously interfere with the ECoG. We report a case where nitrous oxide appeared to suppress focal epileptiform activity at the time of intraoperative ECoG, and subsequent withdrawal of nitrous oxide produced generalized electrical seizure activity. We recommend that low concentrations of volatile anesthetics may be preferrable to nitrous oxide when ECoG is performed during epilepsy surgery in anesthetized patients.

Journal Article↗
PubMed1989

Autoregulation of cerebral blood flow during normocapnia and hypocapnia in dogs.

The effect of hypocapnia on autoregulation of cerebral blood flow (CBF) and the lower limit of autoregulation (LLA) was determined in dogs anesthetized with nitrous oxide (66%) and halothane (0.2%, end-expired concentration). CBF and cerebral vascular resistance (CVR) were determined during both normocapnia and hypocapnia (PaCO2 21-22 mmHg) at control cerebral perfusion pressure (CPP) and after reducing CPP (by hemorrhage) to 80%, 60%, 50%, and 40% of control. At control CPP hypocapnia decreased CBF from 75 +/- 5 to 48 +/- 3 ml.100 g-1.min-1 (mean +/- SEM, P less than 0.05). During both normocapnia and hypocapnia CVR decreased and CBF did not change as CPP was reduced to 60% of control. When CPP was reduced to 50% or 40% of control, CVR remained decreased and CBF fell sharply. The LLA during hypocapnia, 61 +/- 2% of control CPP, was not different than that during normocapnia, 59 +/- 3% of control CPP. Below the LLA the CBF-CPP slopes differed from zero but did not differ between hypocapnia and normocapnia. Hypocapnia does not produce a substantial shift of the LLA, and over the range of CPP values studied here, autoregulatory cerebral vasodilation only partially abolishes hypocapnia-induced cerebral vasoconstriction. The results suggest that when cerebral autoregulation is intact and in the absence of cerebrovascular disease, hypocapnia does not reduce global CBF to a level that is likely to produce ischemia and remains a useful therapeutic treatment so long as CPP remains above the LLA.

Animals↗
PubMed1989

Bunegin-Albin catheter improves air retrieval and resuscitation from lethal venous air embolism in upright dogs.

Three types of catheters, the Arrow multi-orifice catheter, the American Edwards 7 Fr Swan-Ganz catheter and the Cook Bunegin-Albin multi-orifice CVP catheter were evaluated for their ability to retrieve venous air emboli and effect on the success rate of resuscitation from venous air emboli. The catheters were inserted in dogs anesthetized with isoflurane (1.7%, inspired) and N2O (66%) in O2 and placed in the sitting position with the head 90 degrees to the horizontal. Swan-Ganz catheters were positioned with the right atrial (RA) port just above the junction of the superior vena cava (SVC) and the RA and the pulmonary artery (PA) port in the pulmonary artery. The Arrow and Bunegin-Albin multi-orifice catheters were placed with the proximal orifice just above the SVC-RA junction and the distal orifice near the mid-RA. Dogs were then given a predetermined lethal dose of air (5 ml.kg-1) over 30 sec via the jugular vein. Attempts to aspirate venous air emboli were begun with the first decrease in expired CO2. Both RA and PA ports of the Swan-Ganz catheter were used for aspiration. The amounts of gas retrieved expressed as a percent of the injected air and the incidence of successful resuscitation were compared. Significantly greater percentages of injected venous air were retrieved with the Bunegin-Albin catheter (63 +/- 14%, mean +/- SEM) than with the Arrow multi-orifice catheter (6 +/- 2%) or the Swan-Ganz catheter (14 +/- 5%).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

The site of origin of the intravascular electrocardiogram recorded from multiorificed intravascular catheters.

Successful retrieval of venous air emboli via central venous catheters requires accurate placement of the distal tip of the catheter. The distal tip of single-orificed central venous catheters can be precisely located using intravenous electrocardiography (IVECG). However, the site of origin of the IVECG complex with multiorificed central venous catheters is not well known. In this study, the site of origin of the IVECG complex deriving from the wire within a multiorificed Arrow Antecubital Central Venous Catheterization Kit, the same Arrow catheter type without wire, and a multiorificed Cook Bunegin-Albin CVP Kit was determined in ten anesthetized dogs. The IVECG was found to originate from the distal portion of the Arrow wire whether the distal tip of the wire was within the distal segment of the Arrow multiorificed catheter, at the tip of the catheter, or protruding several cm from the tip of the catheter. When the Arrow multiorificed catheter (without wire) was used to determine the IVECG, the mean site of origin of the IVECG was 1.7 +/- 1.2 cm (mean +/- SD) proximal to the distal catheter tip. When the Cook multiorificed catheter (without wire) was used to determine the IVECG, the mean site of origin of the IVECG was 2.5 +/- 0.6 cm proximal to the distal catheter tip. Knowledge of the site of origin of the IVECG with the Arrow and Cook multiorificed catheters should permit the distal tips of these catheters to be placed in locations where efficient retrieval of venous air emboli is likely.

Animals↗
PubMed1987

Bunegin-Albin catheter improves air retrieval and resuscitation from lethal venous air embolism in dogs.

Three types of catheters, the single-orifice Sorenson CVP kit catheter, the right atrial (RA) port of an American Edwards 7F Swan-Ganz catheter, and the Cook Bunegin-Albin multi-orifice CVP catheter were evaluated for their ability to retrieve venous air emboli and effect on the success rate of resuscitation from venous air emboli. The catheters were inserted in anesthetized dogs in the prone position. Swan-Ganz catheters were positioned with the RA port just above the junction of the superior vena cava (SVC) and the RA, single-orifice Sorensen catheters with the orifice tip located either just above the SVC-RA junction or in the mid-RA, and Bunegin-Albin multiorifice catheters with the proximal orifice just above the SVC-RA junction and the distal orifice near the mid-RA. Dogs were then given a predetermined lethal dose of air (5 ml/kg) over 30 sec via the femoral vein. Attempts to aspirate venous air emboli were begun with first decrease in expired CO2. The amounts of air retrieved and the incidence of successful resuscitation were compared. Significantly greater percentages of injected venous air were retrieved with the Bunegin-Albin catheter (60 +/- 7%) than with the Sorenson catheter in the SVC (16 +/- 6%), with the Sorenson catheter in the mid-RA (10 +/- 3%) or with the Swan-Ganz RA port (4 +/- 1%). Resuscitation was significantly more often successful with the Bunegin-Albin catheter (six of nine dogs) than with either Sorenson catheter (zero of seven in both groups) or the Swan-Ganz RA port (one of seven).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1986

Cerebral effects of hypocapnia plus nitroglycerin-induced hypotension in dogs.

This study examined the effect of hypocapnia (PaCO2 20 mm Hg) on cerebral metabolism and the electroencephalogram (EEG) findings in 12 dogs during nitroglycerin (NTG)-induced hypotension. Previous studies suggest that NTG is a more potent cerebral vasodilator than sodium nitroprusside or trimethaphan. It was speculated that combining hypocapnia with NTG-induced hypotension would cause less disturbance of cerebral metabolism and the EEG than the disturbances previously reported when hypocapnia was combined with hypotension induced by sodium nitroprusside or trimethaphan. All 12 dogs were examined at 1) normocapnia with normotension; 2) hypocapnia with normotension; and 3) hypocapnia combined with NTG-induced hypotension to mean arterial blood pressure (MABP) levels of 60, 50, and 40 mm Hg. In six dogs the cerebral metabolic rate of oxygen was determined, and the EEG was evaluated using compressed spectral analysis. Brain tissue metabolites were calculated in the other six dogs. During normotension, hypocapnia caused no deterioration of cerebral metabolism or of the EEG. Hypocapnia combined with NTG-induced hypotension caused a decrease of the power of the alpha and beta 2 spectra of the EEG at MABP's of 60 mm Hg or less. At an MABP of 40 mm Hg, brain tissue phosphocreatine and the cerebral energy charge decreased, while the brain tissue lactate:pyruvate ratio increased. Thirty minutes after restoration of normocapnia with normotension, cerebral metabolites returned to initial values, but the power of the EEG alpha and beta 2 spectra was decreased compared to baseline values. The cerebral metabolic disturbances and EEG alterations seen here with hypocapnia plus NTG-induced hypotension were similar to those previously reported with hypocapnia plus sodium nitroprusside-induced hypotension, and less than those previously reported with hypocapnia plus trimethaphan-induced hypotension. For hyperventilated patients, administration of NTG may be a better hypotensive treatment than trimethaphan, but similar in effect to sodium nitroprusside.

Animals↗
PubMed1984

Effects of cardiac output on the clearance of air emboli from the superior vena cava.

The authors assessed the effect of cardiac output on the rate of clearance of air emboli from the superior vena cava (SVC) in 11 dogs placed in a supine 30 degrees head-up inclined position. Venous air emboli were produced by infusing 4 ml of air into the dorsal sagittal sinus. Air emboli appearance and clearance from the SVC were determined from the analog record produced by a transesophageal Doppler ultrasound monitor. Cardiac output was altered by changing the level of anesthesia and the administration of intravenous fluid. Eighty-eight per cent of air infusions resulted in an analog response of consistent amplitude indicating that all or a similar fraction of the infused air arrived consistently at the ensonified region of the SVC. In this group, air emboli passed from the SVC with a clearance time (CT) that was related inversely to the cardiac index (CI). CT = 24 CI-1.3 with a correlation coefficient = 0.57. Following 12% of the air infusions, there was evidence that a part of the air became detained in vascular sites cranial to the ensonified portion of the SVC. This evidence consisted of the following observations: analog responses were diminished in amplitude; subsequent air injections evoked responses that sometimes were exaggerated; and/or subsequent increases in cardiac output alone, produced spontaneous analog responses characteristic of air emboli. The authors postulate that air similarly may be detained in clinical settings and may explain such phenomenon as persistent precordial Doppler sounds of air emboli after pulmonary artery pressure has returned to normal following symptomatic air embolism and occurrence of air emboli after scalp closure.

Animals↗
PubMed1984

Regional blood flow in dogs during halothane anesthesia and controlled hypotension produced by nitroprusside or nitroglycerin.

We used the radioactive microsphere method to measure and compare the effects of sodium nitroprusside (SNP) and nitroglycerin (NTG) on organ blood flow during hypotension induced by each drug. The study was done in 10 dogs anesthetized using 0.7% end-tidal halothane. Each animal received both SNP and NTG to decrease the mean arterial blood pressure (MABP) to 45 mm Hg, but the sequence in which the drugs were administered was alternated. Five of the dogs received SNP first and five received NTG first. Organ blood flow was measured after a stable period of hypotension that was brief by necessity in order to avoid cyanide toxicity due to increasing dose requirements for SNP. Measurements were made before and during hypotension induced with each drug. The mean duration of stable hypotension was shorter (P less than 0.05) with NTG (5 +/- 1 min) (mean +/- SEM) than with SNP (7 +/- 1 min). During NTG-induced hypotension, blood flows to the brain, kidneys, liver, gastrointestinal tract, pancreas, and skeletal muscle were maintained at control levels. During SNP-induced hypotension, blood flows to the myocardium, liver, gastrointestinal tract, pancreas, and skeletal muscle were maintained at control levels. NTG increased myocardial blood flow (P less than 0.05), while SNP decreased blood flow to brain (P less than 0.05) and kidneys (P less than 0.01). Both drugs decreased blood flow to the spleen (P less than 0.001). Our results indicate that during the first few minutes of NTG-induced hypotension, blood flows to all organs except the spleen are well-maintained, while the first few minutes of SNP-induced hypotension are associated with decreases in blood flow to brain and kidneys as well as to the spleen.

Animals↗
PubMed1983

Evaluation of transesophageal Doppler detection of air embolism in dogs.

The authors assessed the use of a cylindrical sensor which transceives (transmits and receives) ultrasound in a 360 degree arc mounted on a standard esophageal stethoscope catheter to detect air embolism in dogs. They used electronic circuitry developed specifically to provide a continuous analog recording of high frequency Doppler energy as well as an audible signal. They found that the esophageal Doppler sensor was easy to position. In 25 of 30 dogs, the system distinguished Doppler sounds of venous air emboli that were present either in the superior vena cava, right atrium, right ventricle, or pulmonary artery from normal cardiovascular sounds. In the remaining five animals, Doppler heart and air emboli sounds were initially of poor quality, but improved with aspiration of air from the esophagus. In another five dogs, arterial air emboli produced by left ventricular injections also were detected. The esophageal sensor was sensitive to both venous and arterial air emboli ranging from 0.05--0.2 ml of air, and the authors consistently detected repeated intravenous injections of air throughout a 5-h time period. Optimal position of the sensor for detection of venous air emboli was at the level of the superior vena cava above its junction with the right atrium. Optimal position to detect arterial air emboli introduced via a left ventricular catheter was at the level of the aortic arch. Tissue analysis of the esophagus revealed no morphologic damage due to the sensor or transmitted energy.

Animals↗
PubMed1983

The effects of prophylactic expiratory positive airway pressure on the resolution of oleic acid-induced lung injury in dogs.

It is not known whether positive end-expiratory airway pressure (PEEP) merely improves gas exchange in patients with the adult respiratory distress syndrome (ARDS) or if it also affects the resolution of their lung injury. The present investigation was performed to determine whether expiratory positive airway pressure (EPAP), a form of PEEP, is prophylactic in preventing the lung injury induced by oleic acid in dogs or in enhancing its resolution. Arterial and mixed venous blood gases and functional residual capacity (FRC) were measured in 14 pairs of mongrel dogs with indwelling catheters and permanent tracheostomies. One member of each pair was treated with 10 cm H2O EPAP through a valve attached to the tracheostomy tube. Both dogs received 0.06 ml/kg oleic acid intravenously at hour 0. Measurements were made at three, 12, and 24 hours, when EPAP was discontinued, and over the next six days. Five dog pairs were sacrificed at 72 hours; the other surviving animals were sacrificed at 168 hours. FRC was higher at three, 12, and 24 hours in dogs receiving EPAP than in the untreated dogs. The arterial oxygen tension (PaO2) was higher and the venous admixture (Qva/Qt) was lower at three and 12 hours in the dogs receiving EPAP than in the untreated dogs. However, after 24 hours, no differences were noted between the two groups in FRC, PaO2, Qav/Qt, mortality, final lung compliance to initial lung compliance differences, lung water to dry lung weight ratios, or histology. It is concluded that EPAP improves gas exchange during its administration, but has no demonstrable prophylactic effect on the resolution of lung injury in the oleic acid model of human ARDS.

Animals↗
PubMed1982

The effects of expiratory positive airway pressure on the resolution of oleic acid-induced lung injury in dogs.

It is not known whether positive end-expiratory pressure (PEEP) merely improves gas exchange in patients with the adult respiratory distress syndrome or also affects the resolution of their lung injury. We examined the effects of expiratory positive airway pressure (EPAP), a form of PEEP, on 13 pairs of spontaneously breathing mongrel dogs with permanent tracheostomies that were subjected to acute lung injury from oleic acid. One member of each pair was treated with 10 cm H2O EPAP by means of a special valve attached to its tracheostomy tube; the other member breathed through the tracheostomy tube alone. The EPAP was applied 3 h after an intravenous injection of 0.06 ml/kg oleic acid and continued for a total of 21 h. Functional residual capacity (FRC) was increased to preinjury values in the EPAP-treated dogs at 3, 12, and 24 h compared with that in the untreated dogs. The PaO2 was higher and the venous admixture (Qva/QT) was lower in the EPAP-treated dogs compared with that in the untreated dogs at 3 and at 12 h. However, over the 7 days after removal of EPAP no significant differences were noted between the 2 groups in FRC, PaO2, Qva/QT, inert gas elimination profiles, mortality, final lung compliance to initial lung compliance differences, lung water to dry lung weight ratios, or histologic features. We conclude that EPAP improves gas exchange during its administration but has no demonstrable effect on the resolution of lung injury induced by oleic acid in dogs.

Animals↗