Elevated serum levels of S-100 after deep hypothermic arrest correlate with duration of circulatory arrest

Objective.

Cerebral damage is a major problem after reconstructive surgery of the aortic arch and the descending aorta. Current protective strategies, including deep hypothermia and retrograde cerebral perfusion, are used to prolong the tolerated duration of circulatory arrest, and the latter may also decrease the possibility of air/particle embolization. The aim of the current study was to investigate whether the neurochemical marker S-100 is related to the duration of circulatory arrest, when the influence of embolic injury has been minimized by the use of retrograde cerebral perfusion during the last part of circulatory arrest.

Methods.

Arterial serum levels of S-100 were followed before, during and after reconstructive surgery of the thoracic aorta during deep hypothermic arrest in ten adults. Retrograde cerebral blood perfusion was used during the latter part of the arrest period in eight of the ten patients. Neurologic status was followed daily.

Results.

All patients survived the operation. The median (range) duration of cardiopulmonary bypass (CPB) was 184.5 (121 – 386) min. The median duration of circulatory arrest and retrograde cerebral perfusion was 50 (3 – 118) min and 16 (0 – 84) min, respectively. S-100 increased from 0.10 (0.02 – 0.18) g/l preoperatively to 2.37 (0.64 – 10.80) g/l after CPB (P<0.01), followed by a decrease to 0.79 (0.21 – 2.64) g/l on the first postoperative day (P<0.01). The duration of circulatory arrest correlated with S-100 levels after CPB (r_S=0.71, P<0.05) and even better with the S-100 levels on the first postoperative day (r_S=0.83, P<0.01). However, there was no significant correlation between duration of arrest and duration of CPB. The duration of circulatory arrest without retrograde cerebral perfusion correlated well with S-100 levels on the first postoperative day (r_S=0.88, P<0.01), but not significantly with S-100 levels after CPB.

Conclusions.

S-100 levels after aortic surgery with deep hypothermic arrest correlate with the duration of circulatory arrest, indicating that the duration of circulatory arrest is damaging to the brain despite the use of deep hypothermia and partial retrograde cerebral perfusion. The highest correlation between S-100 and duration of arrest was seen on the first postoperative day. S-100 appears to perform well under clinical circumstances as a sensitive and discriminative marker for neuronal injury.     

Cerebral oxygen metabolism during total body flow and antegrade cerebral perfusion at deep and moderate hypothermia

The aim of this study is to evaluate the effect of temperature on cerebral oxygen metabolism at total body flow bypass and antegrade cerebral perfusion (ACP). Neonatal piglets were put on cardiopulmonary bypass (CPB) with the initial flow rate of 200 mL/kg/min. After cooling to 18°C (n = 6) or 25°C (n = 7), flow was reduced to 100 mL/kg/min (half‐flow, HF) for 15 min and ACP was initiated at 40 mL/kg/min for 45 min. Following rewarming, animals were weaned from bypass and survived for 4 h. At baseline, HF, ACP, and 4 h post‐CPB, cerebral blood flow (CBF) was measured using fluorescent microspheres. Cerebral oxygen extraction (CEO₂) and cerebral metabolic rate of oxygen (CMRO₂) were monitored. Regional cranial oxygen saturation (rSO₂) was continuously recorded throughout the procedure using near‐infrared spectroscopy. At 18°C, CBF trended lower at HF and ACP and matched baseline after CPB. CEO₂ trended lower at HF and ACP, and trended higher after CPB compared with baseline. CMRO₂ at ACP matched that at HF. Cranial rSO₂ was significantly greater at HF and ACP (P < 0.001, P < 0.001) and matched baseline after CPB. At 25°C, CBF trended lower at HF, rebounded and trended higher at ACP, and matched baseline after CPB. CEO₂ was equal at HF and ACP and trended higher after CPB compared with baseline. CMRO₂ at ACP was greater than that at HF (P = 0.001). Cranial rSO₂ was significantly greater at HF (P = 0.01), equal at ACP, and lower after CPB (P = 0.03). Lactate was significantly higher at all time points (P = 0.036, P < 0.001, and P < 0.001). ACP provided sufficient oxygen to the brain at a total body flow rate of 100 mL/kg/min at deep hypothermia. Although ACP provided minimum oxygenation to the brain which met the oxygen requirement, oxygen metabolism was altered during ACP at moderate hypothermia. ACP strategy at moderate hypothermia needs further investigation.     

The effects of cardiopulmonary bypass on postoperative oxygen metabolism

The relationships between oxygen delivery (DO₂), oxygen consumption (VO₂), and the extraction rate (ER=VO₂/DO₂x100) in patients undergoing cardiopulmonary bypass (CPB) may differ from the normal physiologic state due to the oxygen debt acquired during CPB. Blood gas analysis and hemodynamic parameters were repeatedly measured for the determination of DO₂ and VO₂ in 40 patients undergoing CPB, every 8h during the first 48h postoperatively. As a control, 20 patients who had suffered acute myocardial infarction (AMI) were also studied using the same protocol. In the CPB group, a regression analysis showed that VO₂ was significantly dependent on DO₂, even within the physiologic range of DO₂ (>500 ml/min per m²); VO₂=121.4+0.0844×DO₂ (r=0.254,P=0.023). Conversely, in the AMI group, no such supply-dependent consumption was observed within the same range of DO₂. At an ER of 30%, which is the optimal value in general, the DO₂ of the CPB group was 575 ml/min per m² and that of the AMI group was 493 ml/min per m². All these results suggest that patients undergoing CPB need a much higher oxygen supply to recover from the oxygen debt acquired during open heart surgery.     

Influence of the analgesic strategy on the respiratory function after thoracic surgery for lobectomy

Objective

To compare the influence of thoracic epidural analgesia (TEA) with intravenous patient-controlled analgesia with morphine (PCA) on the early postoperative respiratory function after lobectomy.

Study design

Prospective and comparative observational study.

Patients and methods

Fourty-four patients scheduled for lobectomy (n = 22 per group) were studied on the evolution of the postoperative respiratory function assessed by the forced vital capacity (FVC) and the forced expired volume (FEV₁) during the first two postoperative days and the analysis of noctural arterial desaturation during the three first postoperative nights.

Results

The use of TEA resulted in fewer decrease both in FEV₁ (1.01 ± 0.34 versus 1.31 ± 0.51 l/s for Day 1, P = 0.03; 1.13 ± 0.37 versus 1.53 ± 0.59 l/s for Day 2, P = 0.01) and in FVC (1.23 [1.05-1.51] versus 1.57 [1.38–2.53] l for day 1, P = 0.008; 1.33 ± 0.43 versus 2.24 ± 0.87 l for day 2, P < 0.001). Moreover, the duration of arterial desaturation < 90% were longer in the PCA group during the first (8.6 [0.8–28.2] versus 1.3 [0–2.6] min, P = 0.02) and the second postoperative night (13.5 [3.5–54] versus 0.4 [0–2.6] min, P = 0.025).

Conclusion

The results of this study suggest that the use of TEA is associated with a better preservation of respiratory function assessed by spirometric data and noctural arterial desaturation recording after thoracic surgery for lobectomy.     

Risikofaktoren bei Patienten mit zweizeitigem Thoraxverschluss nach Korrektur eines angeborenen Herzfehlers

Background

Primary sternal closure after cardiac operations in infants with congenital heart defects can lead to hemodynamic instability due to cardiac dilation and increased inotrope dependency. The alternative comprises secondary sternal closure (SSC).

Patients and methods

We performed a retrospective study on 43 neonates and infants, who were operated for congenital heart defects with the use of cardiopulmonary bypass (CPB) in our clinic between January 1994 and September 2003. In these infants SSC was indicated. The age difference at the time of operation was 48.4 months (0.03 months to 48.43 months), the weight difference varied from 1.0 kg to 12.8 kg (median 3.7 kg). The average operation time was 377.9 min (45 min to 670 min), during which CPB was used on average for 221.1 min (31 min to 521 min). In 34 (79 %) infants the sternum was left open primarily, while in the other 9 (21 %) patients the thorax was reopened secondarily on the same day as the operation. In order to makeshift close the thorax, an EPIGARD^® membrane was used in 31 cases (72.1 %) and in the other 12 patients (27.9 %) a SILASTIC^® membrane was used.

Results

6 patients (14 %) died before SSC. In the other three the thorax was closed secondarily; however they succumbed postoperatively to multi-organ failure. In three patients superficial thoracic wound infections occurred. There was no correlation detected between weight, CPB time and mortality. We found a positive correlation between epinephrine- dose 60 minutes after the end of CPB and the interval to final sternal closure. The central venous pressure (CVP) of the 9 patients who died were between 9 and 20 cm H₂O (median =15 cm H₂O). The CVP of the 34 survivors was between 2 and 28 cm H₂O (median = 10 cm H₂O), p<0.007. 77.8 % of patients who had deceased had an oxygen partial pressure below normal 60 minutes after the end of CPB. In addition, the median of 39.1 mmHg was much lower compared to the survivors (median = 199 mmHg).

Conclusion

SSC is not a routine procedure and is associated with a low infection risk. Higher epinephrine dependency 60 minutes after the end of CPB prolongs the time until final sternal closure. Patients with a CVP over 15 cm H₂O 30 minutes after CPB and with oxygen partial pressure below 95 mmHg at 60 minutes after CPB have a worse postoperative prognosis.     

Jugular Venous Oxygen Saturation During Mild Hypothermic Versus Normothermic Cardiopulmonary Bypass in Elderly Patients

Purpose. Age is known to be a major risk factor for adverse postoperative cognitive dysfunction after cardiac surgery. We conducted this study to determine if jugular venous oxygen saturation (SjvO₂) differed during mild hypothermic (32°C) and normothermic cardiopulmonary bypass (CPB) in elderly patients.Methods. Sixty patients aged over 70 years who underwent elective coronary artery bypass grafting were randomly divided into two groups. Group 1 (n = 30) underwent normothermic CPB (>35°C) and group 2 (n = 30) underwent mild hypothermic CPB (32°C). For the continuous monitoring of SjvO₂, a fiberoptic oximetry oxygen saturation catheter was inserted into the right jugular bulb after the induction of anesthesia. Hemodynamic parameters, and arterial and jugular venous blood gases were measured at seven time points.Results. The SjvO₂ in the normothermic group was lower at the onset of CPB and 20min after the onset, than from the time of induction of anesthesia until the start of surgery (period 1), the respective SjvO₂ values being 50.3% ± 1.0%, 50.1% ± 1.6%, and 59.5% ± 1.9% (P < 0.05). However, in the mild hypothermic group there were no changes in the SjvO₂ value throughout the study. The cerebral desaturation time (when the SjvO₂ value was <50%) and the ratio of the cerebral desaturation time to the total CPB time in the normothermic group differed significantly from those in the hypothermic group, being 19 ± 11min and 17% ± 10%, and 9 ± 3min and 8% ± 4%, respectively (P < 0.05).Conclusions. The SjvO₂ value was better during mild hypothermic CPB than during normothermic CPB in elderly patients.     

Less Platelet Damage in the Curved Vane Centrifugal Pump: A Comparative Study with the Roller Pump in Open Heart Surgery

Abstract: The centrifugal pump with the curved vane (Lifestream Centrifugal Pump [LCP]) was applied to cardiopulmonary bypass (CPB) in 10 patients who underwent elective coronary artery bypass grafting. Serum hemoglobin levels, platelet counts, and serum β–thromboglogulin (β–TG) levels were measured during CPB. The results were compared with those for a comparative roller pump (RP) group (n = 10). There was no difference in CPB time between LCP (112 ± 22 min) and RP (121 ± 22 min) groups. Serum β–TG levels (ng/ml) were lower in the LCP group than in the RP group (34 ± 9 vs. 101 ± 80, 5 min; 81 ± 33 vs. 236 ± 112, 30 min; 120 ± 53 vs. 314 ± 100, 60 min after initiation of CPB; p < 0. 05). There were no significant differences in hemolysis and platelet depletion. The LCP showed excellent hemodynamic performance with less blood trauma in clinical application to open heart surgery.     

Thyroid function during and after cardiopulmonary bypass in children

Background: The aim of the study was to elucidate the changes in thyroid function during and after cardiopulmonary bypass (CPB) in children.
Methods: Triiodothronine (T3), thyroxine (T4), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) were determined preoperatively, at specific times throughout CPB, and serially up to 48 h postoperatively, in 10 children (median age 35, range 23–68 months) undergoing elective surgery for congenital heart disease.
Results: T3 decreased from 2.01±0.08 preoperatively to 0.94±0.10 nmol/1 24 h postoperatively ( P <0.05). T4 levels followed a pattern similar to changes in T3. FT4 increased from 17.4±0.7 preoperatively to 30.0±0.4 pmol/1 after 30 min of CPB ( P <0.05). TSH decreased from 2.44±0.43 preoperatively to 0.93±0.21 24 h postoperatively ( P <0.05).
Conclusion: T3, T4 and TSH are significantly depressed after open heart surgery in children.     

Subcutaneous Oxygen Pressure in Spontaneously Breathing Lean and Obese Volunteers: a Pilot Study

Background Oxidative killing is the primary defense against surgical pathogens; risk of infection is inversely related to tissue oxygenation. Subcutaneous tissue oxygenation in obese patients is significantly less than in lean patients during general anesthesia. However, it remains unknown whether reduced intraoperative tissue oxygenation in obese patients results from obesity per se or from a combination of anesthesia and surgery. In a pilot study, we tested the hypothesis that tissue oxygenation is reduced in spontaneously breathing, unanesthetized obese volunteers. Methods Seven lean volunteers with a body mass index (BMI) of 22 ± 2 kg/m² were compared to seven volunteers with a BMI of 46 ± 4 kg/m². Volunteers were subjected to the following oxygen challenges: (1) room air; (2) 2 l/min oxygen via nasal prongs, (3) 6 l/min oxygen through a rebreathing face mask; (4) oxygen as needed to achieve an arterial oxygen pressure (arterial pO₂) of 200 mmHg; and (5) oxygen as needed to achieve an arterial pO₂ of 300 mmHg. The oxygen challenges were randomized. Arterial pO₂ was measured with a continuous intraarterial blood gas analyzer (Paratrend 7); deltoid subcutaneous tissue oxygenation was measured with a polarographic microoxygen sensor (Licox). Results Subcutaneous tissue oxygenation was similar in lean and obese volunteers: (1) room air, 52 ± 10 vs 58 ± 8 mmHg; (2) 2 l/min, 77 ± 25 vs 79 ± 24 mmHg; (3) 6 l/min, 125 ± 43 vs 121 ± 25 mmHg; (4) arterial pO₂ = 200 mmHg, 115 ± 42 vs 144 ± 23 mmHg; (5) arterial pO₂ = 300 mmHg, 145 ± 41 vs 154 ± 32 mmHg. Conclusion In this pilot study, we could not identify significant differences in deltoid subcutaneous tissue oxygen pressure between lean and morbidly obese volunteers.     

Der i-STAT Analyzer Ein neues, tragbares Gerät zur Bedsidebestimmung des Hämatokrits, der Blutgase und Elektrolyte

Exact and quick measurements of basic laboratory parameters are important in selected patients in the perioperative period. Depending on the capabilities of a hospital’s central laboratory, the anaesthesiologist may only obtain such laboratory tests after unacceptable delays. This problem may be overcome by a new bedside measurement device that has become available from i-STAT Corporation, Princeton, USA. The hand-held, battery-driven analyser accepts blood specimens that are injected into a disposable cartridge (EG7+) and measures acidity, blood gas tensions, haematocrit, and electrolytes. The aim of this study was to determine the accuracy of such measurements by comparing them with measurements obtained by conventional laboratory test methods. Methods: Heparinised arterial blood specimens were collected in duplicate from 49 surgical patients. Measurements of ionised calcium (Ca), sodium (Na), potassium (K), pH, pCO₂, pO₂, base excess (BE), haematocrit (Hct), and haemoglobin (Hb) obtained by the i-STAT analyser were compared with measurements from the calibrated analysers ABL 615 and EML 100 (Radiometer, Copenhagen). Because the i-STAT analyser calculates the Hb concentration from a conductometrically measured Hct, 19 blood specimens were centrifuged in order to compare test results with conventionally obtained Hct and Hb values. As the Hct test sensitivity with the i-STAT changes with diluted blood due to its low albumin concentration, Hct and Hb measurements during cardio-pulmonary bypass (CPB) must be corrected by activating an analyser-implemented correction algorithm (Hct/CPB and Hb/CPB). Correlation analysis was performed between conventional measurements and i-STAT values (Ca, Na, K, Hct, pCO₂, pO₂), between values that the i-STAT analyser derives (Hb, HCO₃, BE) and conventionally obtained results, and between normal and CPB-corrected Hct and Hb values. Accuracy was judged according to the national quality standard, whic h requires test results to lie within the 95% confidence interval of conventional tests. Results: Each blood specimen was analysed: erroneous results or technical failures did not occur. Measurement of one set of i-STAT values required 2.5 min. Correlation coefficients (r) between conventional and i-STAT results were: 0.85 for CA, 1.0 for K; 0.86 for Na; 0.99 for pH; 0.98 for pCO₂; 0.99 for pO₂; 0.93 for HCO₃; 0.93 for BE; 0.46 for Hb values not corrected for CPB and 0.95 for CPB-corrected Hb; and 0.74 for Hct values not corrected for CPB and 0.98 for CPB-corrected Hct. The correlation coefficient for Hct between centrifuged and CPB-uncorrected i-STAT values was 0.81 and that for CPB-corrected values was 0.98. National accuracy requirements were not met for tests of: Ca (by 0.02 mmol/l); pH (by 0.01); pO₂ including hyperoxic values (by 26.7 mmHg, but were met for pO₂ values <200 mmHg); Hb (by 1.6 g/dl); Hb/CPB (by 0.8 g/dl); and Hct (by 6.5%, but were met for Hct/CPB values). All other tests fulfilled the required standards. Conclusion: This analyser is easy to use, reliable, and portable, and therefore suitable for the operating room, for analyses during emergencies, on peripheral wards, for preclinical screening, or at times when availability of lab tests is time-consuming or limited. The test accuracy for electrolytes, blood gases, and Hb is high enough to justify routine use of the i-STAT analyser in clinical practice. That the nationally required quality standards for Ca, pH, and Hb were not met is not of importance because the measured deviation was too small to have clinical relevance. When analysing diluted blood with a low Hct and low oncotic pressure, it is important to activate the analyser’s correction algorithm ?CPB”, because the obtained results will then comply with the required accuracy.     

Metabolic monitoring during continuous warm- and cold-blood cardioplegia by means of myocardial tissue pH and Po2

Objectives

To study the changes in myocardial tissue pH and Po₂ during cold- and warm-blood cardioplegic arrests.

Design

An experimental study in dogs.

Methods

Nine dogs underwent the following procedures: 30 minutes with an empty heart beating under cardiopulmonary bypass (control period); 30 minutes of warm (33 °C) cardioplegic arrest with a 1:4 mix of crystalloid in blood solution administered continuously at 150 mL/min; 30 minutes of cold (15 °C) cardioplegic arrest; and 30 minutes of myocardial reperfusion. The cardioplegic blood solution was administered antegradely through the ascending aorta.

Main outcome measures

Tissue pH and Po₂. Arterial and coronary sinus oxygen content and myocardial consumption calculated.

Results

There was a modest but significant increase in the left anterior descending (LAD) and circumflex (Cx) tissue pH throughout the experiment. Pmo₂ in the LAD territory averaged 44 (7) mm Hg (mean and standard error of the mean) during the bypass period, 123 (23) mm Hg at the termination of warm cardioplegic arrest, 146 (28) mm Hg at the end of cold arrest and 66 (17) mm Hg after reperfusion. Oxygen consumption averaged 0.65 (0.15) mL/min during the bypass period, 0.3 (0.18) mL/min at the end of warm arrest, 0.25 (0.16) mL/min at the end of cold arrest and 0.45 (0.08) mL/min after reperfusion (p < 0.05). Oxygen delivery to the LAD territory was greater than myocardial oxygen consumption by an average of 2.02 (0.4) mL/min during bypass, 2.02 (0.62) mL/min after warm arrest, 2.12 (0.5) mL/min after cold arrest and 1.55 (0.25) mL/min after reperfusion (p > 0.05).

Conclusions

During cardioplegic arrest, tissue Po₂ increased and oxygen consumption decreased significantly, whereas tissue pH remained normal, suggesting that continuous warm- and cold-blood cardioplegia maintained aerobic glycolysis during myocardial arrest. Thus, the increase in myocardial tissue Pmo₂ during cardioplegic arrest reflects the decrease in myocardial oxygen consumption while maintaining oxygen supply.     

Oxygen delivery and consumption in the perioperative period of coronary artery bypass grafting without blood transfusion

The perioperative changes in relationship between oxygen delivery (D¨_{O 2}) and oxygen consumption (V¨_{O 2}) were examined in forty patients who underwent coronary artery bypass grafting (CABG) without blood transfusion. Hemodilution was performed to maintain hematocrit of 19.2 ± 1.8% during cardiopulmonary bypass (CPB). Hemodynamic and metabolic parameters were measured in four stages; before CPB (stage I), after CPB (stage II), after ICU arrival (stage III), and the following day (stage IV). In each stage, there was a strong positive correlation between V¨_{O 2} and D¨_{O 2}. In stage I, a decrease in D¨_{O 2} was met with low V¨_{O 2}, and there was no imbalance between them (r = 0.67, P 0.01). V¨_{O 2} increased significantly in stage II, and this increased V¨_{O 2} was compensated by an increase in D¨_{O 2} sufficiently to meet tissue oxygen demand (r = 0.59, P 0.01). In stage III and IV, the increases in tissue oxygen requirements were met by increases in oxygen extraction ratio (r = 0.81, P 0.01, r = 0.60, P 0.01, respectively) reflected in lowered mixed venous oxygen tension and saturation. From these results, it is assumed that the adequate relationship between V¨_{O 2} and D¨_{O 2} can be maintained in the perioperative period of CABG without blood transfusion.(Mizushima A, Niimi Y: Oxygen Delivery and consumption in the perioperative period of coronary artery bypass grafting without blood Transfusion. J Anesth 4: 313–318, 1990)     

Pharmacokinetics of doxacurium during normothermic and hypothermic cardiopulmonary bypass surgery

Purpose

To compare the pharmacokinetic behaviour of doxacurium in patients undergoing normothermic or hypothermic cardiopulmonary bypass (CPB) for coronary artery bypass graft surgery.

Methods

Twenty patients in two equal groups were studied. Anaesthesia was induced with sufentanil and midazolam after a standard premedication. Doxacurium was administered at 3 × ED₉₅ (80μ·kg^?1), and anaesthesia was maintained with 0.5 μg·kg^?1 hr^?1 sufentanil, 0.05 mg·kg^?1 midazolam and isoflurane 0.5–1%. Systemic temperature for patients in the normothermic and hypothermic groups was maintained at 33–36C and 26–30C respectively. Timed blood and urine samples were collected and pharmacokinetic parameters were estimated using a non-compartmental approach.

Results

For the normothermic and hypothermie groups, terminal elimination half-life (t_1/2B) was 100.1 ± 28 and 183.8 ± 60 min (P < 0.05) respectively, elimination half-life during the CPB phase (T_1/2 CPB) 114.5 ± 10 and 183.8 ± 60 min (P < 0.05), mean residence time 108.8 ± 25 and 164.8 ± 34 min (P < 0.05) and apparent volume of distribution at steady state 0.20 ± 0.03 and 0.26 ± 0.04 L·kg^?1 (P < 0.05). Compared with the hypothermie group, the normothermic group had a higher rate of renal clearance (1.40 ± 0.4 vs 0.93 ± 0.3 ml·min^?1·kg^?1;P < 0.05) and a higher value for renal clearance as a percentage of the total clearance (76.2 ± 10 vs 58.3 ± 20%).

Conclusion

The elimination rate of doxacurium during normothermic CPB is faster than that in hypothermic CPB.     

The Benefits of High‐flow Management in Children With Pulmonary Atresia

The high‐flow management of cardiopulmonary bypass (CPB; ≥2.4 L/min/m²) is a standard strategy used at this institute for children with pulmonary atresia (PA) due to a fear that the blood flow may be diverted by the major/minor aortopulmonary‐collateral‐arteries and hypervascularization due to long‐term hypoxia. The purpose of this study was to describe the validity of high‐flow management in children with PA. The CPB records of 23 children with PA who underwent a definitive biventricular repair between Feb 2006 and Nov 2008 were retrospectively reviewed. The mean age at the operation was 33 ± 22 months. The blood‐pressure during bypass was controlled with the same protocol. The mean cooling‐temperature was 28.4 ± 3.7°C. The mean minimum hematocrit was 25.0 ± 3.4%. The mean maximum bypass flow index at the initiation, the mean maximum flow index during aortic cross‐clamping, the mean minimum flow index during aortic cross‐clamping, and the mean maximum flow index after rewarming were 3.1 ± 0.5, 3.1 ± 0.5, 2.6 ± 0.4, and 3.2 ± 0.4 L/min/m², respectively. The higher bypass flow indexes significantly correlated with the lower serum lactate levels. The lowest oxygen delivery during CPB had significant influences on the urine output during bypass (R = 0.547, P = 0.007), the serum lactate levels at the end of CPB (R = ?0.442, P = 0.035), and the postoperative thoracic effusion (R = ?0.459, P = 0.028). A bypass flow index of 2.4 L/min/m² may not be sufficient and the maximum requirement of bypass flow index may be 3.2 L/min/m² or more in this patient population.     

Evaluation of cerebral oxygen balance during normothermic cardiopulmonary bypass using jugular oxygen saturation

BACKGROUND: Previous studies suggest that normothermic cardiopulmonary bypass(CPB) impairs cerebral oxygen balance. We studied the effect of normothermic CPB on cerebral oxygen balance evaluated by continuous measurement of oxygen saturation in the jugular vein (SjO2). METHODS: Eleven patients undergoing coronary artery bypass grafting with normothermic CPB were studied. A 4 Fr oxymetry catheter was inserted into the internal jugular bulb for SjO2 monitoring. We measured mean arterial pressure (MAP), SjO2 and hemoglobin (Hgb) concentration at five time points-1) pre CPB, 2) 3) 4) 5, 30, 60 min after the onset of CPB, respectively, 5) 5 min after the end of CPB. RESULTS: MAP decreased significantly 30 min (47 +/- 9 mmHg) and 60 min (48 +/- 9 mmHg) after the onset of CPB compared with the pre CPB (80 +/- 14 mmHg) value. Hgb also decreased significantly 5 min (7.8 +/- 1.1 g x dl(-1)) and 30 min (7.1 +/- 1.0 g x dl(-1)) and 60 min (7.1 +/- 0.8 g x dl(-1)) after the onset of CPB compared with the pre CPB (11 +/- 1.0 g x dl(-1)) value. However, SjO2 showed no significant change throughout the study period. No significant correlation was observed between MAP and SjO2. CONCLUSIONS: Cerebral oxygen balance assessed by SjO2 was not impaired during normothermic CPB, and was unaffected by hypotension and hemodilution.     

Intraoperative myocardial acidosis as a risk for hospital readmission after cardiac surgery

Background

This study elucidates the relationship between intraoperative myocardial acidosis/ischemia and the risk of unplanned hospital readmissions within 30 days and 6 months after cardiac surgery.

Methods

Myocardial tissue pH (corrected to 37°C: pH_37C) was monitored in 221 patients during cardiac surgery. Regional myocardial acidosis was defined in terms of specific pH thresholds.

Results

Fourteen percent and 27% of the patients were readmitted within 30 days and 6 months postoperatively, respectively. The mean number of readmissions was 1.67 ± 1.24; pH_37C <6.85 at the end of cardiopulmonary bypass (CPB) was identified as the threshold most significantly associated with readmission. This threshold was associated with a 6-fold increased risk of readmission within 30 days and a 5-fold increased risk within 6 months.

Conclusions

Persistent regional myocardial acidosis after weaning from CPB independently determines unplanned readmission rates up to 6 months postoperatively. This study underscores the importance of avoiding myocardial tissue acidosis during cardiac surgery.     

Effects of pulsatile and nonpulsatile perfusion on cerebral regional oxygen saturation and endothelin-1 in tetralogy of fallot infants

Although benefits of pulsatile flow during cardiopulmonary bypass (CPB) in pediatric heart surgery remain controversial and nonpulsatile CPB is still widely used in clinical cardiac surgery, pulsatile CPB must be reconsidered due to its physiologic features. In this study, we aimed to evaluate the effects of pulsatile perfusion (PP) and nonpulsatile perfusion (NP) on cerebral regional oxygen saturation (rSO₂) and endothelin‐1 (ET‐1) in pediatric tetralogy of Fallot (TOF) patients undergoing open heart surgery with CPB. Forty pediatric patients were randomly divided into the PP group (n = 20) and the NP group (n = 20). Pulsatile patients used a modified roller pump during the cross‐clamp period in CPB, while NP patients used a roller pump with continuous flat flow perfusion. The subjects were monitored for rSO₂ from the beginning of the operation until 6 h after returning to the intensive care unit (ICU). We also monitored the hemodynamic status and ET‐1 concentration and plasma free hemoglobin (PFH) in blood samples of all patients over time. Effective PP was monitored in PP patients, and pulse pressure was significantly higher in the PP group than in the NP group (P < 0.01). rSO₂ of the PP group was higher than that of the NP group (P < 0.01) during the cross‐clamp period, and this advantage of PP would be maintained until 2 h after patients returned to the ICU (P < 0.05). ET‐1 level in blood samples was lower at clamping off and CPB weaning and early ICU period in the PP group than in the NP group (P < 0.01), and ET‐1 concentration remained at a normal level after patients were transferred to the ICU 24 h in all patients. PFH levels in the PP group at pre‐clamp off and CPB weaned off were higher than those of the NP group (P < 0.05) in these cyanotic patients. PP can increase rSO₂ and improve microcirculation during cross‐clamping period in TOF pediatric patients, while PP resulted in more severe hemolysis in these cyanotic patients than NP.     

LUNG MANAGEMENT DURING CARDIOPULMONARY BYPASS: IS CONTINUOUS POSITIVE AIRWAYS PRESSURE BENEFICIAL?

It is not clear if the use of continuous positive airway pressure(CPAP) during cardiopulmonary bypass (CPB) improves lung functionafter cardiac surgery. We have measured alveolar-arterial oxygenpartial pressure difference (PA_o2 – PA_o2) in 61 patientsundergoing elective coronary artery bypass surgery. We studiedthree groups of patients: in group 1 the lungs were disconnectedfrom the breathing system (no CPAP) during CPB; in group 2,5 cm H₂O CPAP with air was applied to the lungs; in group 3,5 cm H₂O of CPAP was applied with 100% oxygen.(PA_o2 –PA_o2) was measured before CPB and then at 30 min, 4 h and 8h after CPB. Compared with group 1 (no CPAP), (PA_o2 –PA_o2) was significantly smaller in groups 2 and 3 at 30 min(P=0.036), but not at 4 h and 8 h after CPB (P=0.32, P=0.96).The time to extubation (P=0.42) and early extubation (P=0.87)were not affected by the use of CPAP. The results of this studydo not support the use of CPAP during CPB as a mechanism ofimproving lung function after cardiac surgery. (Br. J. Anaesth.1993; 71: 864–868)     

Hydroxocobalamin for the treatment of cardiac surgery-associated vasoplegia: a case series

Purpose

Vasoplegia is a clinical syndrome marked by severe arteriolar vasodilatation, hypotension, and low systemic vascular resistance refractory to multiple vasopressor treatment. We report our experience with hydroxocobalamin (B₁₂) infusion as a potential rescue adjunct for refractory vasoplegia during cardiopulmonary bypass (CPB).

Methods

We performed a retrospective chart review of 33 patients undergoing cardiac surgery between 1 January 2013 and 31 December 2015, who were given intravenous B₁₂ for refractory hypotension during, or immediately following, CPB. We assessed mean arterial pressure (MAP) responses using semi-parametric group-based models (trajectory analysis). Vasopressor use was evaluated by norepinephrine-equivalent rates calculated five minutes prior, and up to 60 min following, B₁₂ administration.

Results

Patients were mostly male (82%), had a mean (SD) age of 53 (13) yr, and median (IQR) EuroSCORE mortality index of 9 [4-40]. Four patterns of MAP responses to B₁₂ were identified. In Group 1 (“poor responders”) nine of 33 patients (27%) had the highest median [IQR] mortality risk (EuroSCORE 40 [4-52]), lowest mean pre-B₁₂ MAP (50 mmHg), and minimal hemodynamic response in spite of continued vasopressor support. In contrast, Group 2 “responders” (8/33, 24%) showed a brisk MAP response (> 15 mmHg) to B₁₂, sustained for > 60 min post-infusion, with 50% vasopressor reduction. Groups 3 and 4 had the lowest median mortality risk (EuroSCORE 8) and highest pre-B₁₂ MAP (72 mmHg). Although Group 3 patients (“sustainers”; 9/33, 27%) showed a sustained MAP improvement, those in Group 4 (“rebounders”; 7/33, 21%) were characterized by hypertensive overshoot followed by a decrease in MAP.

Conclusion

These data indicate considerable heterogeneity in patient response to B₁₂, potentially dependent on both patient preoperative condition and non-standardized time of administration. B₁₂ may provide a useful alternative therapy for refractory hypotension and vasoplegia, but controlled clinical trials to assess efficacy are needed.

     

Risk factors for prolonged ICU stay in patients following coronary artery bypass grafting with a long duration of cardiopulmonary bypass

Purpose Risk factors for prolonged stay in the intensive care unit (ICU) in patients following coronary artery bypass grafting (CABG) have been reported in many previous studies. However few have focused on circulatory and respiratory status as immediate postoperative risk factors. Therefore we examined immediate postoperative risk factors for prolonged ICU stay after CABG with a long duration of cardiopulmonary bypass (CPB).Methods We studied retrospectively 100 consecutive patients undergoing elective CABG with CPB. Patients were excluded from this study if the duration of aortic cross-clamping was less than 60min. Patients were divided into three groups according to the duration of the ICU stay. Patients in group A (n = 68) were discharged from the ICU on the next morning after surgery, those in group B (n = 19) stayed for 3 days, and group C (n = 13) stayed for more than 3 days. Perioperative variables were compared among the three groups and we demonstrated risk factors for prolonged (more than 3 days) ICU stay.Results There were significant differences in duration of CPB (157 ± 34 versus 184 ± 48 minutes, P < 0.05) and aortic cross-clamping (119 ± 32 versus 141 ± 40min) between groups A and B. On the other hand, there were significant differences in age (62.8 ± 7.8 versus 67.4 ± 6.2 years), mean pulmonary artery pressure (MPAP) (17 ± 2 versus 22 ± 3mmHg), and Pa_{O 2}/FI _{O 2} (PF ratio) (409 ± 94 versus 303 ± 108mmHg) on admission to the ICU between groups A and C. There were no significant differences in intraoperative fluid balance and duration of CPB. Multiple logistic regression analysis identified age (>65 years), MPAP (>21mmHg), and PF ratio (<300mmHg) as independent risk factors for more than a 3-day ICU stay.Conclusion Advanced age, increased MPAP, and decreased PF ratio on admission to the ICU were significant risk factors for a prolonged ICU stay of more than 3 days.