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Biomedical subjects

P S Colley

Publications and source records attributed to P S Colley.

31 records · Page 2Linked to original sources
PubMed1981

Pulmonary gas exchange effects of nitroglycerin in canine edematous lungs.

The authors determined the effects of nitroglycerin on pulmonary edema induced by oleic acid injury. Measurements of venous admixture (QVA/Qt) and shunt (Qs/Qt) using both oxygen and inert-gas-elimination methods were done before, during, and after nitroglycerin infusion, first during air ventilation and then during ventilation with 100 per cent oxygen. Nitroglycerin reduced mean blood pressure (MAP) approximately 30 per cent (P less 0.01) during both air and oxygen ventilation. During air ventilation, nitroglycerin caused PVR to decrease by 29 per cent (P less than 0.01) but caused no change in PVR during oxygen ventilation. Pa02 decreased from 64 +/- 8 torr (mean +/- SD) to 55 +/- 9 torr (P less than 0.01) with nitroglycerin infusion during air ventilation. The decrease in Pa02 was primarily due to an increase in QVA/Qt which increased from 28 +/- 12 per cent to 36 +/- 14 per cent (oxygen method) (P less than 0.05). Similarly, the inert gas QVA/Qt increased from 31 +/- 10 to 37 +/- 14 per cent (P less than 0.05). During oxygen ventilation, the effect of nitroglycerin on gas exchange was similar in direction but less in magnitude. These results provide evidence that nitroglycerin may cause significance impairment of pulmonary gas exchange when abnormal lung function is present and FI02 is low. The mechanism is most likely due to inhibition of hypoxic pulmonary vasoconstriction.

Air↗
PubMed1977

Sodium nitroprusside increases Qs/Qt in dogs with regional atelectasis.

This study investigated the effects of sodium nitroprusside (SNP) on arterial oxygen tension (Pao2), pulmonary shunt (Qs/Qt), and pulmonary vascular resistance (PVR) in the presence of atelectasis of one lung. Ten dogs were anesthetized, their tracheas intubated with a bronchial divider, and their lungs ventilated with IPPB with pure oxygen. Atelectasis of the left lung was produced by occluding the left side of the bronchial divider and ventilating the right lung. SNP was infused to decrease mean arterial blood pressure by 25%. Pao2 decreased from (mean value+/-1 SD) 134+/-75 to 77+/-23 torr (P less than 0.05) with SNP infusion. Qs/Qt increased from 30+/-7.0 to 39+/-6.0% (P less than 0.05), while cardiac output did not change significantly. PVR of the atelectatic lung decreased, while PVR of the ventilated lung was unchanged. The decrease in PVR in the atelectatic lung suggests that SNP decreases Pao2 and increases Qs/Qt by reversing the hypoxic pulmonary vasoconstriction. As a result, during SNP infusion, perfusion of the atelectatic lung was maintained while perfusion of the ventilated lung decreased.

Animals↗
PubMed1977

Mechanism of change in pulmonary shunt flow with hemorrhage.

In the presence of regional atelectasis, hemorrhage increases the pulmonary shunt fraction (Qs/Qt). We wanted to determine if the increase in Qs/Qt occurs due to inhibition of hypoxic vasoconstriction or due to hydrostatic effects associated with a collapsed lung and decrease in cardiac output. We compared the effects of hemorrhage on flow to a hypoxic lung (Qh) produced in two ways in anesthetized dogs. In six dogs atelectasis of one lung was produced by bronchial occlusion and in a second group of six dogs one lung was ventilated with 100% nitrogen. The other lung in each group was ventilated with 100% nitrogen. The other lung in each group was ventilated with 100% O2. Hemorrhage (20 ml/kg) had no effect on Qh/Qt in dogs with a nitrogen-ventilated lung suggesting that hemorrhage did not inhibit hypoxic vasoconstriction. In contrast, hemorrhage caused a marked increase in Qh/Qt in dogs with a collapsed lung because the flow to the inflated ventilated lung fell, while flow to the collapsed lung did not change. The increase in Qs/Qt in the dogs with atelectasis can be explained solely on the basis of mechanical effects produced by the differences in lung heights and alveolar pressures between ventilated and atelectatic lung.

Animals↗
PubMed1975

Pulmonary shunt: a comparison between oxygen and inert gas infusion methods.

Pulmonary shunt measurement was compared using the standard oxygen (Berggren) technique and a new multiple inert gas infusion (Wagner et al.) technique in 11 mongrel dogs with either regional atelectasis or diffuse pulmonary edema. Relative retentions of sulfur hexafluoride, ethane, cyclopropane, halothane, diethyl ether, and acetone were used to calculate intrapulmonary shunt. Relative dilution of oxygen (Berggren method) was used to calculate total right to left shunt. The two methods gave similar results in the range of 20-80%. At low shunts the oxygen method measured higher values. This is because of the greater relative importance of fixed extrapulmonary shunts at this level and, as well, error in the measurement of PO2. Both techniques are suitable for normal clinical use.

Acetone↗
PubMedDate not supplied

Propofol versus isoflurane for endoscopic sinus surgery.

PURPOSE: A previous retrospective study reported that propofol anesthesia decreased bleeding during endoscopic sinus surgery compared with isoflurane. We performed a prospective study to compare the effects of propofol versus isoflurane on measured blood loss and the surgeon's subjective assessment of operating conditions during endoscopic sinus surgery. PATIENTS AND METHODS: After receiving institutional review board approval and written informed consent, 56 patients undergoing endoscopic sinus surgery were randomly assigned to receive propofol (n = 30) or isoflurane (n = 26) supplemented with nitrous oxide-oxygen and alfentanil. Blood loss was calculated from the hemoglobin concentration in suction canisters. One surgeon, who was blinded to the anesthetic agent, performed every procedure and assessed bleeding as follows: 1, no bleeding; 2, modest bleeding; 3, bleeding interfering with operating conditions and cause for an agent switch; and 4, intolerable bleeding requiring a change in surgical plan. Results were compared in the two anesthetic groups using chi-squared test, unpaired t-test, Mann-Whitney Utest, and a permutation test. A P of .05 was considered significant. RESULTS: Mean bleeding scores were less over time (P = .02) with propofol anesthesia, particularly in surgery in the ethmoid and sphenoid sinuses (P = .03), and the proportion of patients with a mean score >2 was less in the propofol group (30% v 54%; P = .033). Time until discharge to home or to a limited stay in a hospital bed was also less in the propofol group (183 v 243 minutes; P = .019). CONCLUSION: In our study, surgical blood loss was the same for both anesthetic agents overall, but propofol appeared to offer an advantage in terms of subjective improvement in operating conditions, particularly in the ethmoid and sphenoid sinuses.

Adult↗
PubMedDate not supplied

Cerebral blood flow responses to hypocapnia during hypotension.

Cerebral vascular responses to hypocapnia during hypotension to a mean arterial blood pressure (MAP) = 50 mm Hg induced with sodium nitroprusside (SNP, n = 12) or trimethaphan (TMP, n = 12) were examined in dogs. Cerebral vascular resistance (CVR) and cerebral blood flow (CBF) at PaCO2 = 40 mm Hg, and PaCO2 = 20 mm Hg were examined first at normal MAP then at hypotension in six dogs in the SNP group and six dogs in the TMP group. In both the SNP group and the TMP group, CO2 responsiveness, as indicated by increased CVR and decreased CBF, was intact at normal MAP, but absent during hypotension. In the remaining 6 of 12 dogs in the SNP group and 6 of 12 dogs in the TMP group, CO2 responsiveness at MAP = 50 mm Hg was examined without prior determination of CO2 responsiveness at normal MAP. These additional studies were performed to rule out the possibility that absent CO2 responsiveness during hypotension in the initial groups resulted from (1) physiologic deterioration of the preparation with time, or (2) adaptation of brain extracellular fluid pH to a preceding period of hypocapnia. Again, during both SNP- or TMP-induced hypotension CO2 responsiveness was absent.

Animals↗