The Differential Effects of Prostaglandin E1 and Nitroglycerin on Regional Cerebral Oxygenation in Anesthetized Patients:

The effect of high-dose nitroglycerin on the cerebral saturation and renal function in cardiac surgery: A propensity score analysis

BACKGROUND

The aim of the study was to evaluate the effects of high-dose nitroglycerine administered during cardiopulmonary bypass on the intraoperative cerebral saturation and postoperative serum creatinine concentration in cardiac surgery.

METHODS

In a retrospective cohort study, a total of 239 patients undergoing cardiac surgery with cardiopulmonary bypass at a tertiary medical center were included. General anesthesia consisted of volatile anesthetic and either intravenous loading of high-dose nitroglycerin (infusion rate 10 to 20 mg·h with a total dose of ≥0.5 mg·kg) starting from rewarming of cardiopulmonary bypass throughout the end of the surgery (NTG group; N = 96) or without high-dose nitroglycerin (control group; N = 143). Data for intraoperative cerebral saturation and serum creatinine concentrations before and after cardiac surgery were collected. Propensity score method was used to adjust for potential confounders.

RESULTS

Patients receiving high-dose nitroglycerin had significantly lower mean arterial pressure and hematocrit levels during and after cardiopulmonary bypass. The risk of intraoperative cerebral desaturation was left-sided 23.9% versus 38.5% (p = 0.023), right-sided 28.1% versus 35.7% in the NTG and control groups, respectively. The risk of new-onset stroke and postoperative dialysis was 2.1% versus 6.3% and 1.0% versus 3.5% in the NTG and control groups, respectively.

CONCLUSION

An infusion of high-dose nitroglycerin initiating at rewarming of cardiopulmonary bypass and throughout the postbypass interval may induce hypotension and hemodilution in cardiac surgical patients. Cerebral saturation and renal function were well maintained without increasing the risk of stroke and renal replacement therapy after cardiac surgery with cardiopulmonary bypass.

Intravenous Infusion of Nitroglycerine Leads to Increased Permeability on Dynamic Contrast-Enhanced MR Imaging in Pig Brains

BACKGROUND AND PURPOSE

It has been suggested that off-label use of transdermal nitroglycerine patches to prevent frostbite may lead to severe acute mountain sickness and ataxia. The aim of this study was to investigate the effect of nitroglycerine on brain vascular permeability by using dynamic contrast-enhanced MR imaging in a swine model.

MATERIALS AND METHODS

Eight Danish Landrace-Yorkshire-Danish Landrace pigs of approximately 20-25 kg were scanned with a dynamic contrast-enhanced MR perfusion protocol with and without nitroglycerine intravenous infusion. Compartmental analysis was performed on the basis of the Tofts model, and voxel-based quantitative values of the volume transfer constants from the vascular to the extracellular space were determined.

RESULTS

The scan with nitroglycerine infusion resulted in significantly higher volume transfer constant values than values derived from the first scan without nitroglycerine infusion. Increased volume transfer constant values were observed in 6 of 8 animals.

CONCLUSIONS

Infusion of nitroglycerine increases the vascular permeability of the swine brain on the basis of the transfer constant estimated from dynamic contrast-enhanced MR imaging.

Nitroglycerin- and nicardipine-induced hypotension does not affect cerebral oxygen saturation and postoperative cognitive function in patients undergoing orthognathic surgery

PURPOSE

The aim of this study was to investigate the influence of nitroglycerin- and nicardipine-induced hypotension on regional cerebral oxygen saturation (rSO(2)) and postoperative cognitive function in patients undergoing orthognathic surgery.

PATIENTS AND METHODS

Sixty adult patients scheduled for orthognathic surgery were randomly assigned to either the nitroglycerin group (group 1) or nicardipine group (group 2). After induction of anesthesia, hypotension was induced with continuous infusion of nitroglycerin or nicardipine. Mean arterial pressure (MAP), heart rate (HR), and rSO(2) were measured at the following time points: before induction of anesthesia, immediately before commencing induced hypotension, at 30 and 60 minutes after induced hypotension, and immediately before the end of surgery. Cerebral desaturation was defined as a reduction of rSO(2) less than 75% of baseline for > or = 15 seconds. The Mini Mental State Examination (MMSE) was conducted before surgery and then repeated after 1 week.

RESULTS

Baseline rSO(2) values were similar in the 2 groups. There were no significant differences in rSO(2) values between the 2 groups. Cerebral desaturation was not observed in any of the patients. Both nitroglycerin and nicardipine reduced MAP and increased HR during induced hypotension as compared with the baseline values (P < .05). No differences in MAP and HR during baseline and induced hypotension were observed between the 2 groups. Decreased MMSE scores were not observed in any of the patients.

CONCLUSION

Cerebral oxygen saturation and postoperative cognitive function were not impaired during nitroglycerin- and nicardipine-induced hypotension in patients undergoing orthognathic surgery.

Risks and benefits of deliberate hypotension in anaesthesia: a systematic review

This systematic review was performed to investigate and review the evidence on the risks and benefits of hypotensive anaesthesia in order to answer the following question: 'Should deliberate hypotension be used routinely during orthognathic surgery?' An electronic search on MEDLINE and the Cochrane Library database was carried out for all relevant articles using specific search keywords. All articles were classified by their levels of evidence. Studies with highest level of evidence and rated to have the lowest risk of bias were reviewed. Regarding the benefits of hypotensive anaesthesia, three studies reported significant decrease of blood loss in patients receiving hypotensive anaesthesia. Two studies reported a significant decrease in transfusion rate. Two studies demonstrated improved surgical field and significant reduction in operation time. In terms of risk, no significant changes in cerebral, cardiovascular, renal and hepatic functions in patients receiving hypotensive anaesthesia compared to control were reported. In conclusion, hypotensive anaesthesia appears to be effective in reducing blood loss. Serious consequences due to organ hypoperfusion are uncommon. Hypotensive anaesthesia can be justified as a routine procedure for orthognathic surgery especially bimaxillary osteotomy. Patient selection and appropriate monitoring are mandatory for this technique to be carried out safely.

Effects of nicardipine-induced hypotension on cerebrovascular carbon dioxide reactivity in patients with diabetes mellitus under sevoflurane anesthesia

PURPOSE

The purpose of this study was to examine the effects of nicardipine-induced hypotension on cerebrovascular CO2 reactivity in patients with diabetes mellitus under sevoflurane anesthesia.

METHODS

Nineteen diabetic patients, and 11 nondiabetic patients (serving as controls), undergoing elective orthopedic, cardiovascular, or thoracic surgery were included in the study. The diabetic patients were divided into three groups according to the antidiabetic therapy they were receiving, i.e., diet therapy (n = 6), oral antidiabetic drugs (n = 7), and insulin (n = 6). Anesthesia was maintained with 1.0 minimum alveolar concentration of sevoflurane. Absolute and relative cerebrovascular CO2 reactivity was calculated using a 2.5-MHz pulsed transcranial Doppler (TCD) probe for the continuous measurement of mean blood flow velocity in the middle cerebral artery (Vmca). The cerebrovascular CO2 reactivity was measured both at baseline and during hypotension by increasing the ventilatory frequency by 4 to 7 breaths.min(-1). Nicardipine was used to induce hypotension.

RESULTS

We found that values for the Bispectral index (BSI), baseline mean blood pressure, endtidal CO2 (Pet(CO2)), and Vmca were essentially identical in all patients, irrespective of the type of antidiabetic treatment being taken. Values for absolute and relative CO2 reactivity in insulin-dependent patients, at both baseline blood pressure and during hypotension, were lower than those in patients in the antidiabetic drug, diet, and control groups (during hypotension, absolute CO2 reactivity: diet group: 3.2 +/- 0.9; oral antidiabetic drug group: 3.2 +/- 0.7; insulin group: 1.5 +/- 0.6; control group: 3.4 +/- 0.8 cm.s(-1).mmHg(-1), [P < 0.05 insulin group vs the other groups]; relative CO2 reactivity: diet group, 6.3 +/- 1.0; oral antidiabetic drug group, 6.5 +/- 0.8; insulin group, 3.5 +/- 0.8; control group, 6.5 +/- 0.7%.mmHg(-1), [P < 0.05 insulin group vs the other groups].

CONCLUSION

We concluded that cerebrovascular CO2 reactivity in insulin-dependent patients is impaired during nicardipine-induced hypotension under sevoflurane anesthesia.

The effect of acute normovolemic haemodilution on cerebral oxygenation

Acute normovolemic haemodilution (ANH) may cause an imbalance in cerebral oxygen metabolism because it decreases the arterial oxygen content. This study was designed to investigate the effect of ANH on cerebral oxygenation. By using cerebral oximetry, the regional cerebral oxygen saturation (rSO2) was monitored during ANH in 26 patients without systemic illness (initial haematocrit = 42 +/- 1%). The rSO2 did not show a significant change until the Hct reached >30%. However, it decreased significantly thereafter to reach 88% of the baseline value when the ANH was completed with a Hct value of 24 +/- 1% (before ANH; 71 +/- 6% vs. after ANH; 62 +/- 4%, p < 0.01). In conclusion, an ANH can lead to a reduction in cerebral oxygenation when a patient's Hct goes below 30%.

Cerebral hemodynamics and brain oxygen changes related to gravity-induced loss of consciousness in rhesus monkeys

The aim of the present experiment was to study the influence of +Gz acceleration (head-to-foot inertial forces) onset on cerebral oxygenation changes (cerebral oxy- and deoxy-hemoglobin) and cerebral blood volume (CBV) in order to evaluate the role of cerebral hypoxemia and ischemia in the appearance of +Gz-induced loss of consciousness (G-LOC). We used five rhesus monkeys which were equipped with near infrared spectroscopy optodes fixed onto the parietooccipital cranial bone. G-LOC (isoelectric electrocorticogram) was detected with silver balls electrodes in contact with the dura matter. The animals were centrifuged up to +12 Gz with two onset rates (0.1 and 3 G/s). Cerebral deoxy-hemoglobin increased significantly (max: +30 +/- 6% of control, P < 0.01) only during the 0.1 G/s run. At G-LOC, CBV changes were not related to G-onset rate (P = 0.30; mean change: -32 +/- 6% of control). We conclude that cerebral ischemia is the main mechanism in the occurrence of G-LOC.

Effects of small doses of prostaglandin E(1) on systemic hemodynamics and jugular venous oxygen saturation during cardiopulmonary bypass

STUDY OBJECTIVE

To examine the effects of small doses of prostaglandin E(1) (PGE(1)) on systemic hemodynamics and cerebral oxygenation during cardiopulmonary bypass(CPB).

DESIGN

Randomized, prospective study.

SETTING

Cardiac surgery at Saitama Cardiovascular and Pulmonary Center.

PATIENTS

Forty patients who underwent elective coronary artery bypass surgery.

INTERVENTIONS

The study was performed at the stable CPB period. Patients were randomly divided into four groups: control group (n = 10) received an infusion of saline, PGE(1) 10 group (n = 10) received an infusion of PGE(1) 10 ng/kg/min, PGE(1) 25 group (n = 10) received an infusion of PGE(1) 25 ng/kg/min, and the PGE(1) 50 group (n = 10) received an infusion of PGE(1) 50 ng/kg/min.

MEASUREMENTS

After measuring the baseline partial pressure of the arterial oxygen saturation (SpO(2)), mixed venous oxygen saturation (SvO(2)), and jugular venous oxygen saturation (SjvO(2)), blood gases, and cardiovascular hemodynamic values, PGE(1) was infused intravenously at rate of between 10 and 50 ng/kg/min. PGE(1) infusion continued 30 minutes after the start of drug infusion, and the blood gas analysis and cardiovascular hemodynamic values were simultaneously determined together with the hemodynamic values at 2, 5, 10, 20, and 30 minutes during drug infusion. At 30 minutes after discontinuation of the drug infusion, the blood gas analyses were simultaneously determined together with the hemodynamic values.

MAIN RESULTS

Mean arterial pressure (MAP) in PGE(1) 25 and 50 groups was decreased 20 and 30 minutes after the start of PGE(1) infusion compared with the baseline value (p < 0.05). In contrast, SvOm(2) in PGE(1) 25 and 50 groups was increased 20 and 30 minutes after the start of PGE(1) infusion compared with the baseline value (p < 0.05). There was no change in SjO(2) value despite a decrease in MAP during the study.

CONCLUSIONS

Cerebral oxygenation estimated by SjvO(2) was maintained despite a decrease in MAP during the administration rate of PGE(1) between 10 and 50 ng/kg/min.

Reduction of cerebral hyperemia with anti-hypertensive medication after electroconvulsive therapy

PURPOSE

Several different anti-hypertensive regimens have been introduced for the prevention of systemic hyperdynamic responses after electrically induced seizures. In the present study, the effects of anti-hypertensive medications on cerebral circulation were studied.

METHODS

Systemic blood pressure was controlled by several anti-hypertensive medications, nicardipine, prostaglandin EI, alprenolol and nitroglycerin, in 30 patients (150 electroconvulsive therapy trials). Changes in cerebral blood flow velocity were measured by transcranial Doppler sonography of the right middle cerebral artery from the start of anesthesia to 10 min after the electrical shock.

RESULTS

Administration of a Ca2+ antagonist, nicardipine, or prostaglandin EI did not alter the augmented cerebral blood flow velocity after the seizure. However, a beta-adrenergic blocking agent, alprenolol (P<0.05) or nitroglycerin (P<0.01) partially inhibited the increase in cerebral blood flow velocity. Maximal blood flow velocity was 133% larger than the pre-anesthesia value in the control group, 109% in the nicardipine group, 113% in the prostaglandin EI group, 72% in the alprenolol group, and 45% in the nitroglycerin group, respectively. The increase in cerebral blood flow velocity after electrically induced seizure was independent of systemic blood pressure. Internal jugular venous saturation (SjO2) was increased, and difference in arterial and venous concentrations of lactate was not altered in all groups.

CONCLUSIONS

Cerebral hemodynamics is altered by ECT, even when systemic hemodynamics are stabilized by antihypertensive medication. Although the effects of antihypertensive medicine on cerebral hemodynamics are variable, systemic blood pressure control by these agents does not induce cerebral ischemia after ECT.

Balloon pump-induced pulsatile perfusion during cardiopulmonary bypass does not improve brain oxygenation

BACKGROUND

Whether pulsatile flow offers substantial advantages for brain protection during cardiopulmonary bypass is controversial. The purpose of this study is to determine whether differences exist between pulsatile and nonpulsatile bypass concerning the effects on internal jugular venous saturation and on the state of regional cerebral oxygenation during normothermia.

METHODS

Twenty-two patients undergoing elective coronary artery bypass grafting were randomly divided into 2 groups: group 1 (n = 11) received nonpulsatile perfusion during cardiopulmonary bypass and group 2 (n = 11) received pulsatile perfusion during bypass. We used an intra-aortic balloon pump to generate pulsatility. A spectrophotometric probe (INVOS 3100R, Somanetics, Troy, Mich) was used to assess the state of regional cerebral oxygenation. A 4F fiberoptic oximetry oxygen saturation catheter was inserted into the right jugular bulb to monitor jugular venous oxygen saturation. Hemodynamic variables, arterial and jugular venous blood gases, and regional cerebral oxygenation were measured at 7 times points.

RESULTS

In both groups, jugular venous oxygen saturation decreased at the early stage of the cardiopulmonary bypass (P =.03). Five patients in group 1 and 6 in group 2 had a jugular venous oxygen saturation of less than 50%. In both groups, the regional cerebral oxygenation value decreased during cardiopulmonary bypass (P =.04).

CONCLUSIONS

The present results showed that pulsatility generated through the use of intra-aortic balloon pumping did not produce any beneficial effects on jugular venous oxygen saturation and regional cerebral oxygenation at normothermia.

Effects of hypothermic and normothermic cardiopulmonary bypass on brain oxygenation

BACKGROUND

In this study, we assessed the effects of normothermia and hypothermia during cardiopulmonary bypass (CPB) both on internal jugular venous oxygen saturation (SjvO2) and the regional cerebral oxygenation state (rSO2) estimated by near infrared spectroscopy (NIRS).

METHODS

Thirty patients scheduled for elective coronary artery bypass graft surgery (CABG) were randomly divided into two groups. Group 1 (n = 15) underwent surgery for normothermic (> 35 degrees C) CPB, and group 2 (n = 15) underwent surgery for hypothermic (30 degrees C) CPB, and alpha-stat regulation was applied. A 4.0-French fiberoptic oximetry oxygen saturation catheter was inserted into the right jugular bulb to continuously monitor the SjvO2 value. To estimate the rSO2 state, a spectrophotometer probe was attached to the mid-forehead. SjvO2 and rSO2 values were then collected simultaneously using a computer.

RESULTS

Neither the cerebral desaturation time (duration during SjvO2 value below 50%), nor the ratio of the cerebral desaturation time to the total CPB time significantly differed (normothermic group: 18+/-6 min, 15+/-6%; hypothermic group: 17+/-6 min, 13+/-6%, respectively). The rSO2 value in the normothermic group decreased during the CPB period compared with the pre-CPB period. The rSO2 value in the hypothermic group did not change throughout the perioperative period.

CONCLUSIONS

These findings suggest that near infrared spectroscopy might be sensitive enough to detect subtle changes in regional cerebral oxygenation.

Cerebral oxygenation during prostaglandin E1 induced hypotension

PURPOSE

To evaluate the cerebral oxygenation effects of hypotension induced by prostaglandin E1 (PGE1) during fentanyl-oxygen anaesthesia.

METHODS

Ten patients who underwent elective cardiac surgery received infusion of PGE1. After measuring the baseline arterial, mixed venous and internal jugular vein blood gases, systemic haemodynamics, and regional cerebral oxygen saturation (rSO2) estimated by INVOS 3100R, PGE1 was continuously infused at 0.25-0.65 microgram.kg-1.min-1 (mean dosage: 410 +/- 41.4 mg.kg-1.min-1) intravenously. Ten, 20 and 30 minutes after the start of drug infusions, blood gases described above were obtained simultaneously with the measurement of systemic haemodynamics and rSO2. Thirty minutes from the start of drug infusions, administration of PGE1 was stopped. The same parameters were measured again 10, 30 minutes after the stop of drug infusion.

RESULTS

PGE1 decreased mean arterial pressure (MAP) to approximately 70% of the baseline value (P < 0.05). PGE1 increased mixed venous saturation, but in contrast did not affect internal jugular pressure, internal jugular oxygen saturation and rSO2.

CONCLUSIONS

These results suggest that PGE1 is a suitable drug for induced hypotension because flow/metabolism coupling of brain and regional cerebral oxygenation were well maintained during hypotension.