Renal lactate extraction as an indicator of tissue hypoxia in haemorrhagic hypotension

The interrelation between the renal cortical pO2 and renal fractional extraction of arterial lactate was investigated in dogs subjected to gradual haemorrhage up to 45-50% of their blood volume. The cortical pO2, measured by means of an implanted Silastic tube, responded immediately to graded haemorrhage. The renal lactate extraction increased parallel with the arterial lactate concentration when the cortical pO2 declined from the mean initial value of 36 mmHg to 15 mmHg. A further decline of the cortical pO2 was followed by a sharp fall in the renal lactate extraction. A decrease in lactate extraction correlated closely with the cortical pO2 below 15 mmHg during severe hypoperfusion. These results suggest that the changes in the renal lactate utilization are independent of the tissue oxygen tension until the cortical pO2 decreases to the level at which the renal metabolism becomes limited by the availability of oxygen. Below this cortical pO2 the renal lactate extraction decreases in proportion to the developing tissue hypoxia.     

重度蒸汽吸入性损伤后组织氧合的变化

采用蒸汽吸入造成实验犬急性肺损伤，探讨伤后心输出量（ＣＯ）、氧供量（ＤＯ_２）、氧耗量（ＶＯ_２）、氧摄取率（ＥＲＯ_２）、动脉和混合静脉血氧分压（ＰａＯ_２和ＰｖＯ_２）、动脉和混合静脉血氧饱和度（ＳａＯ_２和ＳｖＯ_２）、肺泡氧分压（Ｐ_ＡＯ_２）以及肺泡－动脉氧分压差（Ｐ_（Ａ－ａ）Ｏ_２）等变化。结果表明，蒸汽吸入４ｈ内，ＣＯ、Ｄ０_２、ＰａＯ_２、ＰｖＯ_２、ＳａＯ_２、ＳｖＯ_２、ＰＡＯ_２和ｐＨ值均显著下降（Ｐ＜０．０１）、Ｐ_（Ａ－ａ）Ｏ_２、ＥＲＯ_２和ＰａＣＯ_２均显著升高（Ｐ＜０．０１和０．０５），ＶＯ_２则无显著变化。提示，蒸汽吸入性损伤后２～４ｈ即可出现组织缺氧，其直接原因是组织灌注和供氧不足。     

Effects of indomethacin on hemodynamics of dogs in refractory hemorrhagic shock.

We examined the effects of indomethacin upon anesthetized control dogs and dogs in refractory hemorrhagic shock. Systemic arterial pressure, central venous pressure, cardiac output, and blood flow to the kidney, the heart, the brain, a small intestinal segment, and a piece of skeletal muscle were measured. Systemic vascular resistance and resistances of the vascular beds of the kidney, the heart, the brain, a small intestinal segment, and a piece of skeletal muscle were calculated. Blood flow distribution within the renal cortex was also examined. Indomethacin treatment had little effect upon dogs that were not in shock. Blood flow to the skeletal muscle was decreased. There was also a redistribution of blood flow within the renal cortex with a greater proportion of renal cortical flow going to the outer cortex. However, systemic vascular resistance, cardiac output, and blood flow to the heart, kidneys, brain, and small intestine were unchanged.The refractory shock state was characterized by low systemic arterial pressure and cardiac output with vascular resistance identical to control. Blood flow to the kidney and brain appears to be decreased while coronary flow is maintained. In addition, the ratio of outer renal cortical blood flow to inner renal cortical blood flow, which in the control dog was about 1.5, decreases to 1.Indomethacin treatment largely reversed the hypotension of refractory shock. The increase in arterial pressure following indomethacin treatment is the result of an increase in systemic vascular resistance. Indomethacin treatment had no effect upon cardiac output. The vascular resistances of the kidney, heart, brain, and small intestine increased following treatment of dogs in refractory shock with indomethacin. Renal blood flow was decreased 57%. The renal cortical blood flow distribution was shifted toward the outer cortex as in the controls.Substances dependent upon prosta glandin synthetase may be involved in the hypotension that is characteristic of refractory hemorrhagic shock and may be important in maintaining blood flow to the kidneys and gut.     

Oxygen Transport to Tissue under Normovolemic Moderate and Extreme Hemodilution during Coronary Bypass Operation

Oxygen transport to tissue was studied in 12 patients undergoing coronary bypass operation under normovolemic moderate and extreme hemodilution. Normovolemic moderate hemodilution (15 ml per kilogram of body weight), carried out immediately after induction of anesthesia, decreased the mean hematocrit from 0.43 to 0.33. Simultaneously, the cardiac index and the left ventricular filling pressure increased slightly but the systemic oxygen transport was reduced by 20%. The subcutaneous tissue oxygen tension (Po₂) was approximately 40 mm Hg after induction of anesthesia and underwent a transient increase during moderate hemodilution. During cardiopulmonary bypass and extreme hemodilution, the mean hematocrit declined to 0.16. Concurrently, the mean tissue Po₂ fell sharply and reached a minimum of 14 mm Hg at deepest hypothermia. After decannulation and reinfusion of autologous blood, the Po₂ rose to 30 mm Hg. In general, total-body oxygen consumption changed along with tissue Po₂. Blood lactate concentration underwent a clear increase in the early phase of extracorporeal circulation and remained rather stationary thereafter. No perioperative myocardial infarctions were encountered, and each patient made an uneventful recovery.     

Renal hemodynamics during carbon dioxide pneumoperitoneum

Background: Laparoscopic living donor nephrectomy is increasingly being performed, although the effects of carbon dioxide pneumoperitoneum (CO2 PP) on renal function and hemodynamics and the levels of vasopressin are not well studied. Methods: Renal blood flow, renal venous pressure, urine output, and vasopressin concentrations in renal venous blood were measured in pigs subjected to 12 mmHg of CO2 PP for 150 min. Results: Renal blood flow was decreased at induction of PP and increased during the first 30 min after exsufflation. Renal venous pressure was increased during PP. There was indirect evidence of a decrease in urine output during PP. No changes in renal venous vasopressin concentrations were seen. Conclusion: A CO2 PP of 12 mmHg causes changes in renal hemodynamics and urine output. No changes in vasopressin levels were seen in this pig model, suggesting that other explanations for the observed changes must be sought.     

Postoperative Hepatic Blood Flow and Its Relation to Systemic Circulation and Blood Gases During Splanchnic Blockade and Fentanyl Analgesia

Thirty-four patients with gallbladder disease, but otherwise healthy, were studied in connection with cholecystectomy. For postoperative analgesia, 22 patients were given a posterior splanchnic blockade with 0.5 % plain lidocaine, and 12 were injected intramuscularly with fentanyl in a dose of 3.5 ùg/kg b.w. Postoperatively, before administration of the analgesic agent, the cardiac output, mean arterial blood pressure, heart work and estimated hepatic blood flow were increased and the total peripheral resistance, splanchnic vascular resistance, arterial oxygen tension and base excess values were decreased. Fentanyl in addition to its analgesic effect, also decreased the arterial oxygen tension and pH and increased the arterial carbon dioxide tension. There was little change in cardiac output, mean arterial blood pressure and estimated hepatic blood flow. Following splanchnic blockade, on the other hand, pain relief was accompanied by a decrease in cardiac output, mean arterial blood pressure and heart work to about the preoperative level, while the estimated hepatic blood flow remained unchanged and the splanchnic vascular resistance decreased rapidly. Neither total peripheral resistance nor blood gases altered as a result of splanchnic blockade.     

Correlation between cerebral oxygen saturation measured by near-infrared spectroscopy and jugular oxygen saturation in patients with severe closed head injury.

Near-infrared spectroscopy has been used to monitor cerebral oxygen saturation during cerebral circulatory arrest and carotid clamping. However, its utility has not been demonstrated in more complex situations, such as in patients with head injuries. The authors tested this method during conditions that may alter the arteriovenous partition of cerebral blood in different ways. METHODS: The authors compared changes in measured cerebral oxygen saturation and other hemodynamic parameters, including jugular venous oxygen saturation, in nine patients with severe closed head injury during manipulation of arterial carbon dioxide partial pressure and after mean arterial pressure was altered by vasopressors. RESULTS: The Bland and Altman representation of cerebral oxygen saturation versus jugular oxygen saturation showed a uniform scatter. Values for changing arterial carbon dioxide partial pressure were: bias = 1.1%, 2 SD = +/-21%, absolute value; and those for alterations in mean arterial pressure: bias = 3.7%, 2 SD = +/-24%, absolute value. However, a Bland and Altman plot of changes in cerebral oxygen saturation versus changes in jugular oxygen saturation had a negative slope (alteration in arterial carbon dioxide partial pressure: bias = 2.4%, 2 SD = +/-17%, absolute value; alteration in mean arterial pressure: bias = -4.9%, 2 SD = +/-31%, absolute value). Regression analysis showed that changes in cerebral oxygen saturation were positively correlated with changes in jugular venous oxygen saturation during the carbon dioxide challenge, whereas correlation was negative during the arterial pressure challenge. CONCLUSIONS: Cerebral oxygen saturation assessed by near-infrared spectroscopy does not adequately reflect changes in jugular venous oxygen saturation in patients with severe head injury. Changes in arteriovenous partitioning, infrared-spectroscopy contamination by extracerebral signal, algorithm errors, and dissimilar tissue sampling may explain these findings.     

Cerebral oxygen extraction and autoregulation during extracorporeal whole body hyperthermia in humans

BACKGROUND: The effects of hyperthermia on the human brain are incompletely understood. This study assessed the effects of whole body hyperthermia on cerebral oxygen extraction and autoregulation in humans. METHODS: Nineteen patients with chronic hepatitis C virus infection, not responding to interferon treatment, were subjected to experimental therapy with extracorporeal whole body hyperthermia at 41.8 degrees C for 120 min under propofol anesthesia (23 sessions total). During treatment series A (13 sessions), end-tidal carbon dioxide was allowed to increase during heating. During series B (10 sessions), end-tidal carbon dioxide was maintained approximately constant. Cerebral oxygen extraction (arterial to jugular venous difference of oxygen content) and middle cerebral artery blood flow velocity were continuously measured. Cerebral pressure-flow autoregulation was assessed by static tests using phenylephrine infusion and by assessing the transient hyperemic response to carotid compression and release. RESULTS: For treatment series A, cerebral oxygen extraction decreased 2.2-fold and cerebral blood flow velocity increased 2.0-fold during heating. For series B, oxygen extraction decreased 1.6-fold and flow velocity increased 1.5-fold. Jugular venous oxygen saturation and lactate measurements did not indicate cerebral ischemia at any temperature. Static autoregulation test results indicated loss of cerebrovascular reactivity during hyperthermia for both series A and series B. The transient hyperemic response ratio did not decrease until the temperature reached approximately 40 degrees C. Per degree Celsius temperature increase, the transient hyperemic response ratio decreased 0.07 (95% confidence interval, 0.05-0.09; P = 0.000). This association remained after adjustment for variations in arterial partial pressure of carbon dioxide, mean arterial pressure, and propofol blood concentration. CONCLUSION: Profound hyperthermia during propofol anesthesia is associated with decreased cerebral oxygen extraction, increased cerebral blood flow velocity, and impaired pressure-flow autoregulation, indicating transient partial vasoparalysis.     

The Effects of Intrathoracic Pressure During Continuous Two‐Lung Ventilation for Thoracoscopy on the Cardiorespiratory Parameters in Sevoflurane Anaesthetized Dogs

The cardiopulmonary effects of different levels of carbon dioxide insufflation (3, 5 and 2 mmHg) under two‐lung ventilation were studied in six sevoflurane (1.5 minimum alveolar concentration; MAC) anaesthetized dogs during left‐sided thoracoscopy. An arterial catheter, Swan–Ganz catheter and multianaesthetic gas analyser were used to monitor the cardiopulmonary parameters during the experiment. Baseline data were obtained before intrathoracic pressure elevation and the measurements were repeated at intervals after left lung collapse induced by insufflation with carbon dioxide gas. The intrapleural pressure levels used were 3, 5 and 2 mmHg. Arterial blood pressures, cardiac index, stroke index, left and right ventricular stroke work index, arterial haemoglobin saturation, arterial oxygen tension and systemic vascular resistance decreased significantly during hemithorax insufflation, whereas heart rate, right atrial pressure, mean, systolic and diastolic pulmonary arterial pressure, pulmonary capillary wedge pressure, pulmonary vascular resistance and arterial carbon dioxide tension significantly increased during intrapleural pressure elevation. Although carbon dioxide insufflation into the left hemithorax with an intrapleural pressure of 2–5 mmHg compromises cardiac functioning in 1.5 MAC sevoflurane anaesthetized dogs, it can be an efficacious adjunct for thoracoscopic procedures. Intrathoracic view was satisfactory with an intrapleural pressure of 2 mmHg. Therefore, the intrathoracic pressure rise during thoracoscopy with two‐lung ventilation should be kept as low as possible. Additional insufflation periods should be avoided, since a more rapid and more severe cardiopulmonary depression can occur.     

Carbon dioxide output in laparoscopic cholecystectomy

In pneumoperitoneum, carbon dioxide eliminated in expired gas (carbon dioxide output) contains both metabolic and absorbed carbon dioxide from the peritoneal cavity. When elimination of carbon dioxide is much higher than carbon dioxide output, storage of tissue carbon dioxide and arterial carbon dioxide concentrations change. Finally, the rate of carbon dioxide eliminated in expired gas is not a match for the real rate of metabolic production and absorbed carbon dioxide from the peritoneal cavity. During and after insufflation of carbon dioxide, changes in carbon dioxide output were elucidated under constant arterial carbon dioxide pressure (PaCO2), the same as the preinduction level. We studied patients undergoing elective laparoscopic cholecystectomy. Carbon dioxide output, oxygen uptake, respiratory exchange ratio (RER), expired minute ventilation (VE), deadspace to tidal volume ratio (VD/VT ratio) and arterial to end-tidal carbon dioxide partial pressure difference (PaCO2-PE'CO2) were determined before induction, and during anaesthesia, pneumoperitoneum and recovery. By controlling ventilatory frequency (f) every 1 min, PaCO2 was adjusted to concentrations before induction. Constant monitoring of end-tidal carbon dioxide partial pressure (PE'CO2) and intermittent measurement of (PaCO2-PE'CO2) (15-min intervals) were conducted to predict PaCO2). Carbon dioxide output and oxygen uptake decreased significantly from mean values of 83.5 (SEM 5.2), 101.6 (5.1) to 68.5 (4.2), 81.1 (4.6) ml min-1 m-2 (ATPS, P < 0.05) with sevoflurane anaesthesia, and RER did not change. During carbon dioxide pneumoperitoneum (intra-abdominal pressure 8 mm Hg), carbon dioxide output increased by 49% (102.4 (5.0) ml min-1 m-2) (P < 0.05) while oxygen uptake remained stable and RER increased from 0.84 (0.02) to 1.16 (0.03) (P < 0.05). It was necessary to increase VE during pneumoperitoneum by 1.54 times that during anaesthesia to maintain individual PaCO2 values constant. After removal of carbon dioxide from the abdominal cavity, the regression equation of excess carbon dioxide output/BSA best fitted a two-compartment model. The time constants of the rapid and slow compartments were 8.2 and 990 min, respectively. Excess carbon dioxide output/BSA was still 5.5 ml min-1 m-2, 30 min after pneumoperitoneum.      

Renal vasoconstriction in association with acute pancreatitis

Renal failure is a common complication of pancreatitis. To better understand this association, renal function was evaluated in eleven patients in the acute phase of alcoholic pancreatitis and again during convalescence in seven patients. Parameters measured included glomerular filtration rate, effective renal plasma flow, true renal plasma flow, renal vascular resistance, osmolar clearance, amylase clearance, renal oxygen consumption, cardiac output, and peripheral resistance.Average glomerular filtration rate, effective renal plasma flow, and true renal plasma flow were decreased in the acute phase. Osmolar clearance, amylase clearance, mean arterial blood pressure, renal vascular resistance, and total peripheral resistance rose in the acute phase. Cardiac index and extracellular fluid space remained normal. All parameters returned toward normal with convalescence.The combination of systemic hypertension, increased total peripheral resistance and renal vascular resistance, and normal extracellular fluid space suggests a release of a vasopressor during the acute phase of pancreatitis. The therapeutic implications of these findings including the role of vasodilator infusion are discussed.     

Changes in canine conjunctival and cerebral oxygen tension during hemorrhagic hypotension

On-line conjunctival oxygen tension (PcjO2) and cerebral cortical oxygen tension (PcxO2) were measured simultaneously using polarographic oxygen sensors during hemorrhagic hypotension in dogs. Mean arterial pressure (MAP) decreased from a control value of 119 +/- 7 to 52 +/- 1 (SEM) mmHg during initial bleeding of 30 minutes, and then this level of MAP was maintained for another 150min by adjusting the height of the reservoir. During the early phase of arterial hypotension, PcjO2 fell sharply, and this was accompanied by a parallel decrease of carotid artery blood flow and cardiac output, whereas PcxO2 remained unaffected with this level of hypovolemic hypotension which was possibly due to the cerebral tissue autoregulatory mechanism. Thus, it was demonstrated that despite the anatomical similarity and proximity of their blood supply, the conjunctival tissue responded differently to the intracranial cerebral tissues when compared during hemorrhagic hypotension. The study also suggests that monitoring the PcjO2 during surgery may be a useful monitoring tool in detecting early signs of tissue ischemia and hypoxia during hypovolemic shock.     

Hemodynamic and arterial blood gas changes during carbon dioxide and helium pneumoperitoneum in pigs

The effects of pneumoperitoneum with carbon dioxide and helium on systemic hemodynamics and arterial blood gases were investigated in pigs in an attempt to clarify the mechanisms by which pneumoperitoneum may induce organ dysfunction. A total of 16 anesthetized female pigs underwent pneumoperitoneum with carbon dioxide or helium (n=8 each) in a stepwise fashion to intraabdominal pressures of 8, 10, 12, 16, and 20 mmHg. Changes in cardiac output; renal and hepatic blood flow; mean arterial, mean pulmonary arterial, mean pulmonary arterial wedge, inferior vena caval, and portal venous pressures; and total peripheral resistance were measured. Arterial blood samples were obtained at the same time the above parameters were determined. Urine volume was measured as an indicator of renal function. Pneumoperitoneum with either carbon dioxide or helium significantly increased venous pressures and simultaneously decreased cardiac output. These changes were associated with decreases in organ blood flow due to increased peripheral resistance. Urinary output was reduced to a similar degree in the two groups. Blood gas analysis revealed pneumoperitoneum-induced metabolic acidosis in both groups, although hypercapnia was observed only in the carbon dioxide group. These findings suggest that pneumoperitoneum-related organ dysfunction may be due to increased intraperitoneal pressure rather than to hypercapnia.     

Effects of PEEP on residual vascularization in oesophageal substitution gastroplasty by surface oximetry-capnometry and photoplethysmography: an experimental study

OBJECTIVE: To evaluate the effects of positive end-expiratory pressure (PEEP) on residual vascularization in gastric tubes for oesophageal replacement. DESIGN: Experimental open study. MATERIALS: Eleven mongrel dogs. METHODS: Intestinal parietal blood flow was evaluated by photoplethysmography (PPG) and measurement of surface oxygen (PsO(2)) and carbon dioxide (PsCO(2)) tensions under basal conditions. After Akiyama's tubular gastroplasty, three levels of PEEP were administered. At each level, fluids were infused to counter the drop in cardiac output. PPG, surface gas tensions, arterial pressure, cardiac output and arterial blood gas tensions were monitored. Control sections of the bowel were also monitored by PPG. RESULTS: Cardiac output dropped for each level of PEEP and returned to basal levels on volume restabilization and on removal of PEEP. Central venous pressure and pulmonary arterial and capillary pressures increased for each level of PEEP and only returned to basal levels on removal of PEEP. PsO(2) values dropped for each level of PEEP and returned to basal levels on volume restabilization and on removal of PEEP. PsCO(2) levels rose, and PPG wave amplitude dropped, for each level of PEEP; these two variables only returned to basal levels on removal of PEEP. PPG values for the control sections reflected those of the anastomotic area. CONCLUSIONS: PEEP affects surface oxygen values at the level of the gastroplasty by means of its effect on cardiac output. PEEP also creates a venous return compromise and PPG wave amplitude and surface carbon dioxide values are related to this compromise. All three variables could be significant in anastomotic wound healing.     

Changes in jugular bulb oxygenation in patients undergoing warm coronary artery bypass surgery (34-37 degrees C)

BACKGROUND AND OBJECTIVE: Imbalance between cerebral oxygen supply and demand is thought to play an important role in the development of cerebral injury during cardiac surgery with cardiopulmonary bypass. METHODS: We studied jugular bulb oxygen saturation, jugular bulb oxygen tension, arterial-jugular bulb oxygen content difference and oxygen extraction ratio in 20 patients undergoing warm coronary artery bypass surgery (34-37 degrees C) with pH-stat blood gas management. RESULTS: Only two patients showed desaturation (jugular bulb oxygen saturation < 50%) at 5 min on bypass, and none from 20 min onwards. Multiple regression models were performed after using bypass temperature, mean arterial pressure, cerebral perfusion pressure, haemoglobin concentration and arterial carbon dioxide tension as independent variables, and arterial-jugular bulb oxygen content difference, jugular bulb oxygen saturation, oxygen extraction ratio and jugular bulb oxygen tension as individual dependent variables. CONCLUSIONS: We found that jugular bulb oxygen saturation, jugular bulb oxygen tension and oxygen extraction ratio are mainly dependent on arterial carbon dioxide tension, and arterial-jugular bulb oxygen content difference is dependent on arterial carbon dioxide tension and the bypass temperature. Our results suggest jugular bulb oxygenation is mainly dependent on arterial carbon dioxide tension during warm cardiopulmonary bypass.     

Detection of organ ischemia during hemorrhagic shock

BACKGROUND: In a porcine hemorrhagic shock model we aimed to determine: (a) whether blood flow to the intestine and kidney was more reduced than cardiac output; (b) whether parameters of anaerobic metabolism correlated with regional blood flow; and (c) whether metabolic parameters in intestine, kidney and skeletal muscles detected a compromised metabolic state at an earlier stage than did systemic parameters. METHODS: In an animal research laboratory at a university hospital six domestic pigs were subjected to volume-controlled hemorrhage. Every 30 min samples of blood were withdrawn. Systemic and regional hemodynamic parameters and tissue levels of PCO2 were monitored. Whole body and organ-specific oxygen consumption (VO2) and veno-arterial (VA) differences of lactate, glucose, potassium (K+), PCO2, H+ and base excess (BE) were calculated every 30 min. RESULTS: With progressive hemorrhage, intestinal blood flow decreased to the same extent as cardiac output, whereas the reduction in renal blood flow was more pronounced. We found a concomitant reduction in VO2 (onset of supply dependent metabolism) in intestine, kidney and skeletal muscles. In muscular tissue PCO2 increased to levels three times higher than baseline, while renal and intestinal PCO2 increased eightfold. Supply dependency was associated with a concomitant increase in VA CO2 and VA H+. Also, VA lactate increased, mostly in intestine and least in skeletal muscle. Intestinal and renal VA K+ increased, while muscular VA K+ decreased. Arterial lactate and H+ increased considerably, whereas arterial BE decreased. CONCLUSION: With progressive hemorrhage, renal blood flow, but not intestinal and skeletal muscle blood flow, was reduced more than cardiac output. Supply dependent oxygen metabolism (VO2) and organ acidosis occurred simultaneously in the three organs, despite differences in blood flow reductions. Organ ischemia coincided with a pronounced change in arterial lactate and systemic acid base parameters.     

Correlation between Cerebral Oxygen Saturation Measured by Near-infrared Spectroscopy and Jugular Oxygen Saturation in Patients with Severe Closed Head Injury

Background: Near-infrared spectroscopy has been used to monitor cerebral oxygen saturation during cerebral circulatory arrest and carotid clamping. However, its utility has not been demonstrated in more complex situations, such as in patients with head injuries. The authors tested this method during conditions that may alter the arteriovenous partition of cerebral blood in different ways.

Methods: The authors compared changes in measured cerebral oxygen saturation and other hemodynamic parameters, including jugular venous oxygen saturation, in nine patients with severe closed head injury during manipulation of arterial carbon dioxide partial pressure and after mean arterial pressure was altered by vasopressors.

Results: The Bland and Altman representation of cerebral oxygen saturation versus jugular oxygen saturation showed a uniform scatter. Values for changing arterial carbon dioxide partial pressure were: bias = 1.1%, 2 SD = +/-21%, absolute value; and those for alterations in mean arterial pressure: bias = 3.7%, 2 SD = +/-24%, absolute value. However, a Bland and Altman plot of changes in cerebral oxygen saturation versuschanges in jugular oxygen saturation had a negative slope (alteration in arterial carbon dioxide partial pressure: bias = 2.4%, 2 SD = +/-17%, absolute value; alteration in mean arterial pressure: bias = -4.9%, 2 SD = +/-31%, absolute value). Regression analysis showed that changes in cerebral oxygen saturation were positively correlated with changes in jugular venous oxygen saturation during the carbon dioxide challenge, whereas correlation was negative during the arterial pressure challenge.     

Unilateral high-frequency jet ventilation during one-lung ventilation for thoracotomy

One-lung ventilation is indicated during thoracic operations for bronchopleural fistula, pulmonary abscess, and pulmonary hemorrhage in spite of the possibility of the development of severe hypoxemia. To evaluate methods for improving oxygen transport during one-lung ventilation, we applied high-frequency jet ventilation (HFJV) and continuous positive airway pressure (CPAP) to the nondependent lung following deflation to atmospheric pressure in each procedure, and measured the effects on cardiac output and arterial oxygenation. In each case, the dependent lung was ventilated with conventional intermittent positive pressure ventilation (IPPV).

Eight patients were studied during posterolateral thoracotomy using double-lumen endobronchial tubes. HFJV or CPAP to the nondependent lung improved arterial oxygenation significantly during both closed and open stages of the surgical procedures (p < 0.008). When the chest was open, HFJV maintained satisfactory cardiac output, whereas CPAP usually decreased cardiac output (p < 0.008). There were no significant differences in mean partial pressure of arterial carbon dioxide between HFJV, CPAP, and deflation to atmospheric pressure.

In conclusion, HFJV to the nondependent lung provides not only satisfactory oxygenation but also good cardiac output, thereby maintaining better oxygen transport than CPAP or deflation to atmospheric pressure, while the dependent lung is ventilated with IPPV during one-lung ventilation for thoracotomy.     

Arterial blood gases in extraperitoneal laparoscopic urethrocystopexy

BACKGROUND: The aim of this study was to investigate the effects of extraperitoneal laparoscopy and carbon dioxide insufflation on hemodynamic parameters, arterial blood gases and complications in urethrocystopexy operations. METHODS: Twenty-five female patients who underwent extraperitoneal laparoscopic mesh urethrocystopexy operation for the correction of urinary incontinence were allocated to the study. Hemodynamic parameters were noted and blood gas analyzes were performed before the induction of anesthesia, 10 min after induction, 5 and 10 min after the beginning of carbon dioxide insufflation, at the end of carbon dioxide insufflation and 30 min after exsufflation. RESULTS: There was no significant change in mean arterial pressure, peripheral oxygen saturation, arterial carbon dioxide pressure, and arterial oxygen saturation compared to preinsufflation and preinduction values. End-tidal carbon dioxide pressure did not increase above 45 mm/Hg during carbon dioxide insufflation. Arterial oxygen saturation and partial oxygen pressure did not decrease. Subcutaneous emphysema, pneumothorax, pneumomediastinum and pleural effusion were not noted in any patient. CONCLUSION: We conclude that, extraperitoneal laparoscopic urethrocystopexy is not associated with hemodynamic and respiratory impairment.     

Unilateral high-frequency jet ventilation during one-lung ventilation for thoracotomy

One-lung ventilation is indicated during thoracic operations for bronchopleural fistula, pulmonary abscess, and pulmonary hemorrhage in spite of the possibility of the development of severe hypoxemia. To evaluate methods for improving oxygen transport during one-lung ventilation, we applied high-frequency jet ventilation (HFJV) and continuous positive airway pressure (CPAP) to the nondependent lung following deflation to atmospheric pressure in each procedure, and measured the effects on cardiac output and arterial oxygenation. In each case, the dependent lung was ventilated with conventional intermittent positive pressure ventilation (IPPV). Eight patients were studied during posterolateral thoracotomy using double-lumen endobronchial tubes. HFJV or CPAP to the nondependent lung improved arterial oxygenation significantly during both closed and open stages of the surgical procedures (p less than 0.008). When the chest was open, HFJV maintained satisfactory cardiac output, whereas CPAP usually decreased cardiac output (p less than 0.008). There were no significant differences in mean partial pressure of arterial carbon dioxide between HFJV, CPAP, and deflation to atmospheric pressure. In conclusion, HFJV to the nondependent lung provides not only satisfactory oxygenation but also good cardiac output, thereby maintaining better oxygen transport than CPAP or deflation to atmospheric pressure, while the dependent lung is ventilated with IPPV during one-lung ventilation for thoracotomy.