Mixed venous to arterial CO 2 gap as a marker to identify fluid responsiveness in septic shock patients / 中华急诊医学杂志

Objective:To investigate the value of the venous-to-arterial CO 2 gap (Δ CO 2 gap) before and after the fluid challenge (FC) in determining the fluid responsivenessin septic shock patients. Methods:A total of 104 septic shock patients admitted to the Medical Intensive Care Unit (MICU) of Peking Union Medical College Hospital were included in the retrospective study. All patients were monitored by Swan Ganz floating catheter during the FC. Hemodynamics and blood gas indices were collected before FC (T0) and immediately (T1), 10 min (T2), 30 min (T3) and 60 min (T4) after FC. Responders were defined as patients with a > 10% increase in cardiac output (CO) after FC. Spearman correlation analysis was used to evaluate the correlation between CO 2 gap and CO. The value of ΔCO2 gap were calculated by the area under the receiver operating characteristic (AUROC) curve in the whole population. Results:Among 104 patients, the effective rates of FC at T1, T2, T3 and T4 were 59% (61/104), 72% (75/104), 73% (76/104), and 77% (80/104), respectively. CO of patients in the reactive group was lower than that in the non-reactive group at T2 [6.0 (4.7, 7.5) vs. 7.2 (6.4, 8.5) L/min, P=0.019], and there was no significant difference in CO 2 gap between the two groups before FC. Spearman correlation analysis showed that CO 2 gap was negatively correlated with CO, and the correlations between CO 2 content gap and CO was -0.34, and -0.33 of CO 2 pressure gap and CO, respectively (both P <0.05). ROC curve analysis showed that the ΔCO 2 gap at T1 could weakly judge the reactivity at T2, T3 and T4, but could not judge the reactivity at T1. The AUROC at T2 was 0.669 of ΔCO 2 content gap and 0.684 of ΔCO 2 pressure gap (both P <0.05). Conclusions:The evaluate time judging the effect of FC should be appropriately extended. The change value of CO 2 gap before and immediately after volume expansion in septic shock patients can judge the fluid responsiveness within 10 min after FC.

The prognostic value of PI combined with Pv-aCO 2 /Ca-vO 2 in patients with septic shock / 中华急诊医学杂志

Objective:To explore the predictive value of peripheral perfusion index (PI) combined with central venous-arterial carbon dioxide tension to arterial-venous oxygen content ratio(Pv-aCO 2/Ca-vO 2)for prognosis after initial resuscitation of septic shock. Methods:A total of 76 cases of patients with septic shock from January 2019 to January 2021 in emergency intensive care unit (EICU) of Harrson international peace hospital affiliated to Hebei Medical University were enrolled. All recovered according to 2016 Severe Sepsis and Septic Shock Treatment International Guidelines 2016 (SSC 2016) , and PI was monitored, central vein and arterial blood gas analysis was performed, and the ratio of Pv-aCO 2/Ca-vO 2 was calculated.The PI and Pv-aCO 2/Ca-vO 2 at 3 h,hemodynamic variables,oxygen metabolism indexes,APACHEⅡ and SOFA score were recorded.Patients were divided into survival group and death group according to 28 d survival condition, the dfferences in demographics and clinical data were compared between two groups.The Kaplan-Meier urviving curve was created and the survival of the patients was analyzed by the Log-rank test. Risk factors associated with the prognosis were analyzed using the Cox regression analysis. The role of PI and Pv-aCO 2/Ca-vO 2 in prediting death was evaluated by receiver operating characteristic curves(ROC). Results:There were 37 cases in survival group and 39 cases in death group.Compared with death group, PI in survival group [(1.77±0.63) vs. (0.89±0.69)]was significantly higher,and Pv-aCO 2/Ca-vO 2[(1.52±0.52) vs. (2.57±0.86)] was significantly lower ( P<0.05). Kaplan-Meier survival curve showed that the median survival time in the high PI group [20.09 d (95% CI:16.95-23.24) vs.11.00d (95% CI:7.14-14.86)] was longer than that in the low PI group(χ 2=12.424, P=0.000),and that in low Pv-aCO 2/Ca-vO 2 group [23.74 d (95% CI:20.35-27.13) vs.12.85d (95% CI:9.75-15.95)] was longer than that in the high Pv-aCO 2/Ca-vO 2 group (χ 2=12.200, P=0.000) .Cox regression analysis showed that both PI ( RR=0.397, 95% CI: 0.230-0.687, P =0.001) and Pv-aCO 2/Ca-vO 2 ( RR=1.878, 95% CI: 1.169-3.019, P =0.009) were predictors of 28 d mortality.The area under the ROC curve of PI and Pv-aCO 2/Ca-vO 2 for predicting 28 d death in patients with septic shock were 0.828 (95% CI: 0.732-0.923) and 0.785 (95% CI: 0.6777-0.893)respectively. The optimal cutoff values were 0.52 (sensitivity 58.3% and specificity 94.4%) and 0.35 (sensitivity 88.9% and specificity 63.9%)respectively, and the AUC of the combined prediction of the two indicators was 0.903 (95% CI: 0.835-0.971). Conclusions:Combination of PI and Pv-aCO 2/Ca-vO 2 is better to predict the risk of adverse outcomes of septie shock patients,and may provide useful information for the resuscitation at early stage.

Relationship between end-tidal carbon dioxide tension obtained from the distal ends of the tracheal tube and arterial pressure of carbon dioxide with the side stream capnometerin infants with congenital heart disease / 临床麻醉学杂志

Objective To determine the relationship between end-tidal carbon dioxide tension (PET CO 2 )obtained from the distal ends of the tracheal tube and arterial pressure of carbon dioxide (PaCO 2 ) compared with the sidestream capnometer in infants with congenital heart disease. Methods Twenty infants undergoing congenital heart disease surgery,12 males and 8 females,aged 3-48 months,ASA physical statusⅠ-Ⅲ were enrolled.Measurements of PET CO 2 were obtained from the distal ends of the tracheal tube using a sterile 22 G catheter that was inserted into the tube and from the proximal end with a sidestream capnometer in 20 intubated infants with congenital heart dis-ease.The data including PET CO 2 and the arterial PaCO 2 were obtained both after the anesthesia induc-tion and the CPB.Results The data of PET CO 2 obtained from the distal ends of the tracheal tube after the anesthesia induction [(36.8 ±2.7)mm Hg vs.(32.5 ± 1.4)mm Hg,P <0.05 ]and the CPB [(40.8±2.5)mm Hg vs.(36.5±1.6)mm Hg,P <0.05]were both higher than those from the proximal end with a sidestream capnometer.The difference between PaCO 2 and PET CO 2 obtained from the distal ends of the tracheal tube after the induction [(7.1 ±0.7)mm Hg vs.(1 1.4 ± 1.5 ) mm Hg,P <0.01]and the CPB [(9.3±1.2)mm Hg vs.(13.5±2.3)mm Hg,P <0.01]were sig-nificantly lower than that between PaCO 2 and PET CO 2 obtained from the proximal end.Distal side-stream PET CO 2 correlated with the PaCO 2 (R 2 =0.94 after induction and R 2 =0.93 after the CPB,P<0.05).However,the proximal PET CO 2 with the sidestream capnometer correlated very poorly with PaCO 2 whether after the induction (R 2 = 0.68,P < 0.05 )nor the CPB (R 2 = 0.66,P < 0.05 ). Conclusion We conclude that the PET CO 2 obtained from the distal ends of the tracheal tube provides accurate estimates of the PaCO 2 in critically ill infants with congenital heart disease.

Difference in the value of arterial and end-tidal carbon dioxide tension according to different surgical positions: Does it reliably reflect ventilation-perfusion mismatch? / 대한마취과학회지

BACKGROUND: Body posture, as a gravitational factor, has a clear impact on pulmonary ventilation and perfusion. In lung units with mismatched ventilation and perfusion, gas exchange and/or elimination of carbon dioxide can be impaired. In this situation, differences in the value of arterial and end-tidal carbon dioxide tension [Delta(PaCO2 - PETCO2)] are expected to increase. This study was conducted to observe how Delta(PaCO2 - PETCO2) changed according to the 3 different surgical positions, and to determine whether Delta(PaCO2 - PETCO2) is a reliable predictor of ventilation/perfusion mismatch when a patient is in different postural positions. METHODS: Fifty-nine patients were divided into either the chronic obstructive pulmonary disease (COPD) group (n = 29) or the non-COPD group (n = 30). PaCO2 and PETCO2 were measured during surgery in the supine, prone, and lateral decubitus positions after a 10 minute stabilization period. The Delta(PaCO2 - PETCO2) were calculated and compared among positions. RESULTS: The Delta(PaCO2 - PETCO2) decreased slightly in the prone position and increased significantly in the lateral decubitus position compared with the supine position in both groups. These patterns almost corresponded with the degree of ventilation/perfusion mismatch from the results of the radiological studies. The Delta(PaCO2 - PETCO2) in the COPD group was significantly greater than that in the non-COPD group at all surgical positions. CONCLUSIONS: Lateral decubitus position is associated with marked increase in Delta(PaCO2 - PETCO2), especially in patients with COPD. The Delta(PaCO2 - PETCO2) is a simple and reliable indicator to predict ventilation/perfusion mismatch at different surgical positions in patients with or without COPD.

Recent advance in patient monitoring / 대한마취과학회지

Recent advance in technology has developed a lot of new aspects of clinical monitoring. We can monitor sedation levels during anesthesia using various electroencephalographic (EEG) indices, while it is still not useful for anesthesia depth monitoring. Some attempts are made to monitor the changes in sympathetic nerve activity as one of the indicators of stress, pain/analgesia, or anesthesia. To know the balance of sympathetic and parasympathetic activity, heart rate or blood pressure variability is investigated. For trend of cardiac output, low invasive monitors have been investigated. Improvement of ultrasound enables us to see cardiac structure and function continuously and clearer, increases success rate and decreases complication of central venous puncture and various kinds of nerve blocks. Without inserting an arterial catheter, trends of arterial oxygen tension or carbon dioxide tension can be monitored. Indirect visualization of the airway decreases difficult intubation and makes it easier to teach tracheal intubation. The changes in blood volume can be speculated non-invasively. Cerebral perfusion and metabolism are not ordinary monitored yet, but some studies show their usefulness in management of critically ill. This review introduces recent advances in various monitors used in anesthesia and critical care including some studies of the author, especially focused on EEG and cardiac output. However, the most important is that these new monitors are not almighty but should be used adequately in a limited situation where their meaning is confirmed.

Effects of catecholamines on the splanchnic perfusion in rabbit model of septic shock / 中国小儿急救医学

ObjectiveTo assess the effects of dopamine,dobutamine and norepinephrine on the P(g-a)CO2 and superior mesenteric blood flow in septic shock.MethodsRabbit septic shock model was established by challenging with intravenous injection of lipopolysaccharides from Escherichia coil(2 mg/kg).The rabbits with septic shock were randomly assigned to 3 groups-dopamine group(n = 8),dobutamine group(n = 8) and norepinephrine group(n = 8).Apart from volume resuscitation with normal saline solution [20 ml/(kg· h)]，dopamine[5μg/(kg·min)],dobutamine[(5μg/(kg·min)]and norepinephrine [(1μg/(kg·min)]were infused in dopamine group,dobutamine group and norepinephrine group respeclively.Cardiac index(CI) and superior mesenteric blood flow index(SMBFI) were continuously monitored by doppler flowrneter.Gastric mucosal PCO2 was evaluated by gas tonometry every 10 min.Arterial and venous blood gas analyses and lactate levels were measured every 1 h.ResultsMAP,CI,and SMBFI significandy decreased and P(g-a) CO2 increased after lipopolysaccharides infusion in three groups.After 2-hour treatment,MAP in norepinephrine group[(70 +3) mm Hg]was higher than that of dopamine group[(66±4) mm Hg]and dobutamine group[(65±4) mm Hg](P ＜0.05).SMBFI in norepinephrine group [(18.7±2.9) ml/(kg·min)]was higher than that of dopamine group[(16.2±1.6) ml/(kg·min)]and dobutamine group[(15.8±1.9) ml/(kg·min)](P＜0.05).P(g-a) CO2 in norepinephrine group [(30±6) mm Hg]was lower than that of dobutamine group[(23±5)mm Hg](P＜0.05).Condnsion As an adjuvant therapy of volume resuscitation,norepinephrine is more effective than low dose dopamine and dobutamine in improving splanchnic perfusion.

The Relationship between Arterial Carbon Dioxide Tension and Oxygenator Exhausted Carbon Dioxide Tension during Cardiopulmonary Bypass

BACKGROUND: The neurologic deficit is one of the most serious complications after cardiopulmonary bypass (CPB). This complication has reported to be closely associated with arterial partial pressure of carbon dioxide tension (PaCO2). The traditional way to measure PaCO2 is by intermittent arterial gas analysis during CPB. We tested the relationship between PaCO2 and CPB exhausted partial pressure of carbon dioxide tension (exPCO2) which can be monitored continuously during CPB. METHODS: The total 46 patients who underwent cardiac surgery under CPB were studied. Capnography sampling line was connected to CPB exhausted port to monitor exPCO2. We sampled arterial blood from CPB for gas analysis at cooling, stable hypothermia, and rewarming phase and recorded exPCO2 simultaneously at each phase. RESULTS: We found out that exPCO2 was associated with temperature corrected PaCO2 (cPaCO2) at all 3 phases(r = 0.73, 0.70, 0.84, P < 0.05) and with temperature uncorrected PaCO2 (ucPaCO2) at cooling (r = 0.64, P < 0.05) and rewarming phases (r = 0.81, P < 0.05). CONCLUSIONS: We concluded that exPCO2 could be used to monitor either ucPaCO2 or cPaCO2 at cooling and rewarming phase and cPaCO2 at hypothermia during CPB.

Is End-tidal Carbon Dioxide Tension Useful to Predict Arterial Carbon Dioxide Tension during One Lung Ventilation?: A Comparison with during Two Lung Ventilation / 대한마취과학회지

BACKGROUND: End-tidal carbon dioxide tension (PETCO2) is widely used to estimate arterial carbon dioxide tension (PaCO2) under various clinical conditions. This study was conducted to determine if PETCO2 during one lung ventilation (OLV) is as useful as PETCO2 during two lung ventilation (TLV) for predicting PaCO2. METHODS: Forty patients undergoing thoracic surgery were enrolled in this study. During OLV (n = 20) and TLV (n = 20), PaCO2 and PETCO2 were measured. The arterial-end tidal carbon dioxide difference (Pa-ETCO2) was then calculated and a correlation between PaCO2 and PETCO2 was evaluated during OLV and TLV. RESULTS: Pa-ETCO2 was significantly higher during OLV (8.9 +/- 5.1 mmHg) than during TLV (6.1 +/- 3.9 mmHg). In addition, the correlation between PETCO2 and PaCO2 was less significant during OLV (R(2) = 0.43) than during TLV (R(2) = 0.59). CONCLUSIONS: PETCO2 during OLV was not as accurate as PETCO2 during TLV for predicting PaCO2, which indicates that greater attention should be given to the maintenance of normocarbia during OLV than during TLV.

Comparison of Ventilations with LMA and Endotracheal Tube during Closed Circuit Anesthesia / 대한구급학회지

BACKGROUND: LMA has larger dead-space than tracheal tube, ventilation may be influenced by difference of dead space. Closed circuit mechanical ventilation has high risk of hypercarbia because of inadequate CO2 elimination or gas supply. Thus, end-tidal carbon dioxide tension (EtCO2) and arterial carbon dioxide tension (PaCO2) were compared during closed circuit mechanical ventilation with LMA or tracheal tube. METHODS: Thirty adult patients scheduled for general anesthesia were divided into 2 groups. After induction of general anesthesia, laryngeal mask airway (Group 1, n=15) or tracheal tube (Group 2, n=15) were randomly inserted and closed circuit mechanical ventilation was initiated. When steady state had been reached, PaCO2 and EtCO2 were recorded. RESULTS: The PaCO2 was 32.2+/-2.8 (Group 1), 31.5+/-2.2 (Group 2) and the EtCO2 was 33.0+/-2.9, 31.6+/-2.4 respectively and there was no statistical significance between groups. The difference of arterial and end-tidal carbon dioxide tension in each group was -0.8+/-2.6, -0.03+/-2.2 respectively and there was no statistical significance between groups. CONCLUSIONS: The results indicate that in patients who are mechanically ventilated via the closed circuit system, EtCO2, PaCO2, and the difference between arterial and end-tidal carbon dioxide tension were not significantly different between groups.

Monitoring of PETCO2 during High Frequency Jet Ventilation for Laryngomicrosurgery

In general, PETCO2 is well correlated with PaCO2 during spontaneous and conventional mechanical ventilation in normal lungs. However, it is known that during high frequency jet ventilation, PETCO2 may underestimate PaCO2 because of inadequate washout of the anatomical dead space by a small tidal volume and the relatively slow response time of infrared CO2 analyzers. The validity of PETCO2 as a reflection of PaCO2 was assessed during HFJV in 40 patients undergoing laryngeal microsurgery. HFJV was applied through an injector inserted into the trachea 6 cm below the vocal cord. PETCO2 was obtained from a sampling line placed 2 cm below the injector. Both PETCO2 and PaCO2 were measured simultaneously after decreasing the frequency from 100 beats per minute to 15 beats per minute 10 and 20 minutes after the commencement of HFJV. There was a strong correlation (r = 0.955, P < 0.001) and a good correspondence between the mean PETCO2 and PaCO2 values with an average difference of 1.93 +/- 1.21 mmHg and a limit of agreement from -0.49 to 4.35 mmHg. It is suggested that the PETCO2 obtained following a decrease in the jet frequency during HFJV could closely reflect PaCO2.

The Cerebral Oxygen Extraction Ratio during Propofol and Isoflurane Anesthesia / 대한마취과학회지

BACKGROUND: The cerebral vascular response to CO2 has been reported to be preserved during isoflurane and propofol anesthesia. This study compared the cerebral oxygen extraction ratio during normoventilation versus hyperventilation in propofol anesthesia and isoflurane anesthesia. METHODS: 28 patients undergoing cerebral aneurysmal surgery were studied following informed consent. In the isoflurane group (n = 14), anesthesia was induced with thiopental 5 mg/kg, and maintained with isoflurane and nitrous oxide (N2O) in oxygen (FiO2 0.33). In the propofol group (n = 14), anesthesia was induced with propofol 2 mg/kg, and maintained by infusion of propofol and N2O-O2 (FiO2 0.33). Monitoring included measurement of mean arterial blood pressure, heart rate, body temperature, end-tidal CO2 (PetCO2), jugular bulb O2 saturation (SjO2) and arterial O2 saturation (SaO2). Mechanical ventilation was adjusted to achieve PetCO2 levels of 40 and 25 mmHg. Ten minutes of equilibration were allowed at each PetCO2 level. Blood was sampled from the jugular bulb and radial artery at each PetCO2 level (40 and 25 mmHg). The cerebral oxygen extraction ratio was calculated as (CaO2 CjO2) / CaO2 (CaO2; arterial oxygen content, CjO2; jugular bulb oxygen content). RESULTS: The cerebral oxygen extraction ratio was higher in hyperventilation (PetCO2 25 mmHg) compared to normoventilation (PetCO2 40 mmHg) in each group (P < 0.05) and higher in the propofol group compared to the isoflurane group (P < 0.05). CONCLUSIONS: The increased cerebral oxygen extraction ratio in hyperventilation during both isoflurane and propofol anesthesia showed that cerebral vascular CO2 reactivity was maintained during both isoflurane anesthesia and propofol anesthesia. The cerebral oxygen extraction ratio was higher during propofol anesthesia compared to isoflurane anesthesia in both normoventilation and hyperventilation, therefore this data showed that cerebral blood flow was lower during propofol anesthesia compared to isoflurane anesthesia.

Monitoring of Tracheal CO2 Tension during High Frequency Jet Ventilation for Laryngomicrosurgery / 대한마취과학회지

BACKGROUND: The monitoring of end-tidal CO2 tension (PETCO2) during high frequency jet ventilation (HFJV) has been unsatisfactory because of a small tidal volume and slow response time of CO2 analyser, although several authors have reported strategies of successful PETCO2 measurement during HFJV. The aim of this study was to assess the validity of tracheal CO2 tension (PtCO2) as a PaCO2 during HFJV. METHODS: We studied 24 patients undergoing laryngomicrosurgery during HFJV (rates: 100/min; I:E= 0.2; driving pressure: 0.25-0.35 MPa) through a 12 Fr. polyethylene injector placed 6-7 cm below the vocal cord. A gas sampling line was placed longitudinally against the injector and they were wrapped with aluminum foil. Continuous capnography was recorded during 20 minutes of HFJV. Every 5 minutes of HFJV, PtCO2 was obtained from the plateau value of CO2 wave after the stopping of JV and arterial blood gas analysis was done at 20 minutes of HFJV comparing PaCO2 to PtCO2. A Pearson's product moment correlation and regression analysis between PtCO2 and PaCO2 and the agreement between the two methods using Bland-Altman method were assessed. RESULTS: A regression analysis (R2=0.928) and a Pearson's product moment correlation (r=0.965, P<0.001) indicated a strong correlation of PtCO2 and PaCO2 during HFJV. The difference against a mean scatter diagram showed a relative good agreement between the two method (mean difference: 1.58 (SD 2.22) mmHg; limit of agreement: 2.86 and -6.02). CONCLUSIONS: PtCO2 obtained from a plateau of CO2 wave on capnography after interruption of HFJV can accurately reflect PaCO2 during HFJV in relative.

Changes in Arterial to End Tidal CO2 Difference during Pediatric Open Heart Surgery: Cyanotic vs Acyanotic Congenital Heart Diseases / 대한마취과학회지

BACKGROUND: The arterial to end-tidal carbon dioxide tension difference(Pa-ETCO2) can be increased in patients with congenital heart disease(CHD) and, therefore, end-tidal carbon dioxide tension(PETCO2) does not accurately approximates arterial carbon dioxide tension(PaCO2). The purpose of this study was to evaluate the stability of the Pa-ETCO2 in pediatric patients with congenital heart disease undergoing open heart surgery. METHODS: Forty three children with CHD were studied: twenty two were acyanotic and twenty one were cyanotic. Simultaneous PETCO2 and PaCO2 measurements, as well as pulse rate, blood pressure, pH and arterial oxygen tension(PaO2) were obtained for each patient during four intraoperative events: (1) after induction of anesthesia and before sternotomy, (2) after sternotomy and before cardiopulmonary bypass(CPB), (3) after weaning of CPB, and (4) after closure of sternotomy. RESULTS: The PETCO2 of cyanotic group were lower than that of acyanotic group throughout operation period, and did not change significantly after CPB. Cyanotic children demonstrated a greater Pa-ETCO2 difference before CPB as compared with acyanotic group. In acyanotic group, Pa-ETCO2 difference increased significantly after CPB(P <0.05), whereas it remained unchanged in cyanotic group. CONCLUSIONS: Since cyanotic children had higher Pa-ETCO2 differences intraoperatively and acyanotic children showed an increase in Pa-ETCO2 after CPB, the PETCO2 cannot be the alternative value to estimate reliably the PaCO2 during open heart surgery of pediatric CHD.

The Monitoring of PETCO2 via Nasal Cannula in Spontaneously Breathing Patients during Spinal Anesthesia / 대한마취과학회지

BACKGROUND: Monitoring of PETCO2 in the patients during regional anesthesia may be no less important than under general anesthesia, but will aid in early detection of potentially catastrophic events. However, the utility and accuracy of capnography in non-intubated patients has received little attention. We examined correlation between PETCO2 measured via nasal cannula and PaCO2 values in the sedated spontaneously breathing patients during spinal anesthesia. METHODS: Thirty adult patients who underwent elective surgery were administered optimal doses of tetracaine and epinephrine mixture in their site of operation, length, weight and age. Thereafter, we sampled expired gas by 175ml/min and administered oxygen by 3L/min using oxygen delivery CO2 sampling nasal cannula. End tidal carbon dioxide tension, heart rate, blood pressure and respiratory rate were measured before and 20 min after 0.02 mg/kg midazolam i.v.. And arterial blood gases were once measured 20 min after 0.02 mg/kg midazolam i.v.. RESULTS: The patients, sedation state was asleep or calm in awake. End tidal carbon dioxide tension was significantly increased after midazolam injection (p<0.01), but another values were not different after midazolam injection. Linear regression analysis of arterial carbon dioxide tension and end tidal carbon dioxide tension after midazolam injection yielded y = 0.77x + 4.82 and r2 = 0.76 (p<0.01). CONCLUSIONS: End tidal carbon dioxide tension using oxygen delivery CO2 sampling nasal cannula in the sedated spontaneously breathing patients with midazolam during spinal anesthesia were significantly related with arterial carbon dioxide tension. Therefore, we conclude that monitoring of PETCO2 via nasal cannula is a reliable means during spinal anesthesia.

Responsiveness of Cerebral Blood Flow to changes in Arterial Carbon Dioxide during Propofol Anesthesia in Dogs / 대한마취과학회지

BACKGROUND: Propofol is a relatively new intravenous anesthetic agent, and the cerebral blood flow (CBF) response to changes in PaCO2 during propofol anesthesia has not been extensively studied. The purpose of this study was to investigate the effects of propofol anesthesia on the CBF response to changes in PaCO2 in dogs. METHODS: In six dogs, after surgical preparation for posterior sagittal sinus outflow method, loading dose of propofol 5~6 mg/kg was injected and then anesthesia was maintained with a propofol infusion of 20 mg . kg-1 . hr-1 during study. Ventilation was controlled to hypocapnia(PaCO2 20~35 mmHg), normocapnia(PaCO2 35~45 mmHg) and hypercapnia(PaCO2 45~60 mmHg) by adjustment of minute ventilation. Posterior sagittal sinus blood flow was measured by metered syringe and then CBF was calculated. Cerebral metabolic rate for oxygen(CMRO2) was calculated with arterial and sagittal sinus blood analysis. RESULTS: CBF at normocapnia (PaCO2 41+/-5 mmHg) was 28.7+/-11.6 ml . 100 g-1 . min-1 which increased to 46.5+/-14.4 ml . 100 g-1 . min-1 and decreased to 22.1+/-8.9 ml . 100 g-1 . min-1 on increasing PaCO2 (63+/-18 mmHg) and decreasing PaCO2 (33+/-3 mmHg), respectively. The slope of CBF versus PaCO2 was 1.29 ml . 100 g-1 . min-1 . mmHg. Blood pressure, herat rate, PaO2, CMRO2 were not changed between groups. CONCLUSIONS: CBF response to changes in PaCO2 during propofol anesthesia is maintained and the slope of the CBF-CO2 response is similar to that found during anesthesia with other intravenous agents such as thiopental, midazolam, etomidate, opioids.

Respiratory and Cardiovascular Effects in Relation to Single Intravenous Dose of Fentanyl / 대한마취과학회지

BACKGROUND: Fentanyl is a narcotic analgesic with rapid onset and brief duration of action, so we can use it for analgesia in painful condition. But respiratory depression due to high dose is one of the major complications. We studied the respiratory and cardiovascular effects in relation to single dose of fentanyl. METHODS: We selected forty-two adults who had clear conciousness and received spinal anesthesia without premedication. After the fixation of level of anesthesia, we measured respiratory rate(RR), PaCO2, mean arterial pressure(MAP), and heart rate(HR) as a control value. We allocated patients randomly to 4 groups and administrated a bolus of fentanyl(1, 2, 3, 4 mcg/kg) intravenously. The changes of RR, PaCO2, MAP, and HR were observed. RESULTS: In all groups, RR decreased and PaCO2 increased after injection of fentanyl. The change was peak at 5min, and then maintained until 20min. MAP was not changed in all groups and HR decreased with higher dose than 2 mcg/kg. CONCLUSION: Intravenous injection of fentanyl depress the ventilatory function but has not clinically significant depressant effect up to 4 mcg/kg in normal patients.

Variation in Arterial to End - Tidal Carbon Dioxide Tension Differences by Duration of Anesthesia and Position during Anesthesia / 대한마취과학회지

BACKGROUND: The adquacy of ventilation can be monitored noninvasively, continuously, and in real time by using capnography. But the difference between arterial and end-tidal carbon dioxide tension was related to the presence or absence of lung disease, age, ASA class, systolic blood pressure and the other factors. The purpose of this study is to evaluate the effect of duration of anesthesia and position on the difference between arterial and end-tidal carbon dioxide tension. METHOD: 15 patients were selected for supine group(group 1) and 15 patients scheduled for spine surgery were selected for prone group(group 2). The anesthesia was induced by penthotal sodium(5mg/kg) and succinylcholine(2mg/kg). After intubation, anesthesia was maintained by demerol, midazolam, nitrous oxide and oxygen. The patients were ventilated mechanically with tidal volume 10mi/kg and respiration rate 12/min. Arterial and end-tidal carbon dioxide tension, heart rate, arterial blood pressure and esophageal temperature were estimated at 10min after induction of anesthesia. At 30min, 60min and 90min after placement in the position for operation and the end of the surgical procedure, these parameters were also measured. RESULT: 1) Arterial and end-tidal carbon dioxide tension decreased significantly at 30min, 60min and 90min after placement in the position for operation and the end of the surgical procedure in both group. 2) There was no statistically significantly difference in P(a-ET)CO2 between both group. But a gradual increase in mean P(a-ET)CO2 occured with maintenance of anesthesia in group 2. 3) No significant relationship was seen between mean P(a-ET)CO2 and heart rate, mean arterial pressure and temperature. CONCLUSION: We do not believe it is valid to assume that a constant arterial to end-tidal CO2 gradients exists when estimating PaCO2 from P(ET)CO2 when the patient is in the prone position for spine surgery.

Comparison of Arterial Carbon Dioxide Tension and End-tidal Carbon Dioxide Tension in Infants and Children / 대한마취과학회지

End-tidal PCO2 measurements are less accurate in neonates, infants, and small children than in adults. These in accuracies may by attributed in part to the dilution of end-tidal gas with fresh gas as a result of placing the sampling catheter between the endotracheal tube and a partial rebreathing circuit. To determine the most accurate catheter position for measurements of end-tidal gas tensions, end-tidal PCO2 was measured continuously from the distal and proximal end of the endotracheal tube and these data were compared with simultaneous arterial PCO2 The results were as follows: 1) In children weigthing above 15 kg ventilated with partial rebreathing circuit, both distal and proximal end-tidal PCO2 values approximated arterial PCO2 (p<0.05). 2) In infants and children weigthing below 15 kg ventilated with Ayre's T-piece breathing circuit(Jackson-Rees modification), only distal end-tidal PCO2 approximated arterial PCO2.

Comparison between End - Tidal Carbon Dioxide Tension and Arterial Carbon Dioxide Tension during Cardiopulmonary Bypass / 대한마취과학회지

The changes in arterial carbon dioxide tension (PaCO2) during cardiopulmonary bypass reflect changes of temperature and gas flow through an oxygenator. The changes in PaCO2 can be reduced through the frequent analysis of arterial blood gases and subsequent adjustment of total gas flow and CO2 concentration in the gas flow or both. Utilizing a capnometer (CAPNOMAC AGM-103. Datex), we compared end-tidal carbon dioxide tension (PetCO2) from the capnometer with temperature corrected PaCO2 during cardiopulmonary bypass. One end of the sampling port of the capnometer was incorporated into the prime port of the arterial reservoir in a bubbling type oxygenator (William-Harvey). When arterial reservoir temperatures of the oxygenator were 30 degrees C and 35 degrees C, PetCO2 from the capnometer was recorded and two arterial blood gas samplings were done at the same temperatures. The results were as follows: 1) The difference of PetCO2 and temperature corrected PaCO2 was below 3 mmHg in all cases. 2) The relationship between PetCO2 and temperature corrected PaCO2 was significantly linear. The results show that continuous monitoring of PetCO2, using a capnometer is useful to control the changes in PaCO2 during cardiopulmonary bypass.

Relationship between Arterial and End-tidal CO2 Tensions in Anesthetized Infants and Children / 대한마취과학회지

End-tidal (PETCO2) and arterial CO2, tensions (PaCO2) were measured in 66 anesthetized infants and children. 35 patients were under 7 year-old (group 1) and 31 patients were over 7 year-old (group 2). In both groups, differences between PETCO2, and PaCO2, were evaluated, and correlations between PETCO2, and PaCO2, were carried out. The children in group 1 had a PaCO2, (mean+/-S.D.) of 29.2+/-4.1mmHg and a PCO2, (mean+/-S,D.) of 29.2+4.1mmHg. The range of the PaCO2, and PETCO2 difference (P alpha-ETCO2) was from -1.0 to 1.2 mmHg. The children in group 2 had a PaCO2 (mean+/-S.D.) of 29.3+/-3.0 mmHg and a PETCO2 (mean+/-S.D.) of 29.3+/-4.0mmHg. The range of the P alpha-ETCO2 was from 1.9 to 2.5mmHg. The significant direct correlations between PaCO2 and PETCO2 in both groups (r=0.96,0.84, respec-tively) were defined. The difference between groups wasnt statistically significant. It is concluded that in normal infants and children during anesthesia, noninvasive measurement of PET CO2 can be used as a reliable estimate of PaCO2 and that PETCO2did not differ significantly from PaCO2.