Effects of changes in arterial blood gas tensions, acid-base balance and anaesthetic agents upon liver blood flow and oxygen consumption in the greyhound

Hughes, Roger Llewellyn (1979) Effects of changes in arterial blood gas tensions, acid-base balance and anaesthetic agents upon liver blood flow and oxygen consumption in the greyhound. MD thesis, University of Glasgow.

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There have been major technical advances in the surgery of hepatobiliary disease during the past few years. However, the knowledge of the effects upon the liver of changes in blood gases and acid base balance or of the effects of anaesthetic agents, remains limited. The investigations detailed in this thesis were designed to utilise recent advances in construction of electromagnetic flowmeters which allow the simultaneous continuous measurement of blood flow in the hepatic artery and portal vein. This thesis describes studies upon liver blood flow and oxygen consumption in the greyhound. Greyhounds between 25 and 55 kg body weight were anaesthetised with thiopentone and paralysed with pancuronium. Anaesthesia was maintained with pentobarbitone. The dogs were ventilated artificially with a mixture of 75% nitrogen and 259% oxygen. Laparotomy was performed and electromagnetic flow- probes were placed upon the hepatic artery, portal vein and splenic vein, allowing continuous measurement of these blood flows with Statham SP 2202 flowmeters. A cannula was placed in the stump of the gastroduodenal vein to record portal venous pressure and allow portal venous blood sampling and another was placed in a hepatic vein via the external jugular vein. Systemic arterial blood pressure was recorded via a cannula placed in a femoral artery and cardiac output was measured using the thermodilution technique via a triple lumen thermistor tipped catheter placed in the pulmonary artery. Systemic arterial, hepatic venous and portal venous oxygen contents were measured using a Lex-02-Con oxygen content analyser and using the hepatic arterial and portal venous blood flow measurements obtained, hepatic oxygen consumption was calculated. The following groups of experiments were carried out;- 1. Control. A control group was studied to assess the stability of the preparation over a three hour period. This series of experiments demonstrated that the preparation was stable and all the subsequent groups of experiments were designed to be completed in this three hour period. 2. Hypercarbia. A group of animals were studied at four PaCO2 tensions from 55 mm Hg to 100 mm Hg. Portal venous blood flow increased with a simultaneous decrease in hepatic arterial blood flow. Hepatic oxygen consumption was unchanged. 3. Hypocarbia and Positive Pressure Ventilation. A group of animals were passively hyperventilated and the effects of the raised intrathoracic pressure-accompanied by hypocarbia and then normocarbia were studied. Hypocarbic hyperventilation produced a decrease in portal venous and hepatic arterial blood flow. Normocarbic hyperventilation resulted in a restoration of portal venous blood flow but with a further decrease in hepatic arterial blood flow. A decrease in hepatic oxygen consumption with hypocaxbia returning to control with normocarbia was seen. 4. Hyperoxia. A group of animals were studied at three raised PaO2 tensions from 200 to 400 mm Hg. The only significant change seen was a small increase in hepatic oxygen consumption. 5. Hypoxia. This was studied at PaO2 tensions of 70, 55> 40 and 25 mm Hg. Mean arterial pressure was found to increase significantly at each Pa02 tension immediately the hypoxic gas mixture was introduced but returned to control by the time 20 min had passed. At the same time a significant decrease in hepatic arterial blood flow was seen, returning to control by 20 min. No changes in portal venous blood flow were seen. Hepatic oxygen consumption decreased significantly at 25 mm Hg PaOg2 6. Metabolic Acidosis. The effects of an infusion of lactic acid were studied at progressively increasing base deficits. Portal venous blood flow increased while hepatic arterial blood flow decreased. Total liver blood flow remained unchanged. There were no significant changes in hepatic oxygen consumption. (Abstract shortened by ProQuest.).

Item Type: Thesis (MD)
Qualification Level: Doctoral
Additional Information: Adviser: Robert Mathie
Keywords: Veterinary science
Date of Award: 1979
Depositing User: Enlighten Team
Unique ID: glathesis:1979-73166
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56
URI: https://theses.gla.ac.uk/id/eprint/73166

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