Blood Pressure Monitoring And Pulse Pressure Variation In The Prone Position: Agreement Between Invasive Radial Artery And Dorsalis Pedis Artery

Background and ObjectiveArterial blood pressure?BP?is one of the basic vital signs.As long as the anesthetist give the patient an anesthetic,no matter how small the dose is,arterial blood pressure measurement should be done.Maintaining blood pressure within a certain range is very important,which ensures patients under anesthesia have a normal cerebral vascular autoregulation.It is an important factor in preventing cerebral hypoperfusion.Accurate blood pressure monitoring is very important for clinical decision-making of anesthesiologists.Clinical experience and research show that the blood pressure readings of different parts and different measurement methods are not the same.The radial artery and dorsalis pedis artery are peripheral arteries.With the pulse wave propagating from the aorta to the periphery under physiological conditions,the pressure waveforms are distorted due to the reflections of the waves,causing the systolic pressure and pulse pressure to be amplified.The duration of neurosurgery surgery is long and there is fluctuation of blood pressure.In addition to ASA anesthesia basis monitoring,invasive blood pressure monitoring is also performed.Although the radial artery is the most commonly site for puncture and pressure measurement,due to strict sterility requirements,anesthesiologists do not easily contact the patient's upper body.It is not easy to manage the radial artery when the tube is broken or blocked.The direct measurement of the dorsalis pedis artery is far away from the surgical field,which is more convenient for management and easier to press the hemostasis.Therefore,in the neurosurgical anesthesia,the dorsal artery is frequently punctured.At present,There are many studies on the blood pressure gradient between different arteries in the supine position under anesthesia.However,there are few reports on the blood pressure differences in the prone position.Neurosurgery and other operations require the patient to be placed in a prone position.Although the prone position facilitates surgical operations,it has a significant effect on the patient's circulation and respiratory function.Blood pressure fluctuations and hypotension often occur in the prone position.Anesthesiologists should be aware of non-invasive cuff pressure in the brachial artery,invasive radial artery and dorsalis pedis artery pressure in the prone position.Because difference in blood pressure can lead to different treatment measures and clinical outcomes.Hypotension often occurs in the prone position.Ephedrine is a commonly used vasopressor.Compared with phenylephrine and dopamine,ephedrine has less effect on pulse pressure variability.In the prone position,ephedrine increased blood pressure more clearly and lasted longer.Compared with phenylephrine,ephedrine makes cerebral oxygen saturation higher.Whether ephedrine affects the difference in blood pressure is unclear.The pulse pressure variation?PPV?reflects the cyclic changes in preload induced by mechanical ventilation and PPV values,expressed as a percentage,were calculated in an automated fashion using the established formula:PPV=?PPmax-PPmin?/[?PPmax+PPmin?/2]×100%.PPmax and PPmin represent the maximum and minimum PPs observed on the arterial waveform throughout phases of the respiratory cycle.PPV had been shown to reflect accurately volume responsiveness in high-risk surgery.Liquid therapy based on PPV had also been shown to improve the patient's outcome.Although the prone position will make the PPV measurement larger,it still has directive significance for liquid therapy.The radial artery is the most commonly cannulation site for invasive blood pressure monitoring.Therefore,the pulse pressure variation is mostly derived from the radial artery.However,the relationship between pulse pressure variation from the dorsalis pedis artery and radial arterial is worth to be studied.This study aimed to observe the invasive blood pressure and pulse pressure variability of the radial artery and dorsalis pedis artery during neurosurgery prone position surgery,and to analyze consistency of monitoring of arterial blood pressure and pulse pressure variability at both sites and the effect of ephedrine on it.We hope this study provides a reference for blood pressure management and fluid therapy in the prone position during neurosurgery.MethodsSixty patients with ASA?-?from January 2017 to December 2017 who were scheduled for selected neurosurgery in a prone position were enrolled in this study.After admission to the operation theater,ECG was performed.SpO₂ levels,heart rate,and noninvasive blood pressure were measured routinely in all patients.Immediately after induction of anesthesia,the ipsilateral radial artery and dorsalis pedis artery were cannulated with the same catheter.A double-headed disposable invasive pressure monitoring transducer was used and positioned at the patient's midaxillary line and zeroed to atmospheric pressure.Radial artery blood pressure?RABP?,dorsalis pedis artery blood pressure?DABP?and pulse pressure variation?PPV?were monitored.Ephedrine 0.1 mg/kg was used when the direct radial artery systolic pressure was?90-110 mmHg.Observation indicators:Monitor and record the systolic blood pressure and mean blood pressure of radial artery and dorsalis pedis artery at 5min?T₁?after prone position,30min?T₂?,60min?T₃?,and 90min?T₄?.simultaneous recording of PPV?HR and NIBP at the above time.The times of ephedrine used,the blood pressure before and after the use of ephedrine,frequency of radial arterial waveform abnormalities,frequency of dorsalis pedis artery waveform abnormalities,anesthesia time,operation time,blood loss,urine volume,total input.The pearson method was used for correlation analysis and Bland-Altman method was used to analyze the agreement between RABP and DABP,PPVR and PPV_D.Results1.The bias of systolic pressure radial artery and dorsal artery in the prone position was?-8.8±6.2?mmHg,which did not satisfy the AAMI standard,while the bias of mean arterial pressure was?0.2±4.4?mmHg and sastfied the AAMI standard.2.After patients receiving ephedrine,the bias of systolic blood pressure between radial artery and dorsal artery was from?-13.3±7.8?mmHg to?-9.9±6.3?mmHg?P<0.05?;and the bias of mean arterial pressure was from?0.6±2.3?mmHg to?0.1±1.8?mmHg?P>0.05?,respectively.3.In the prone position,the correlation between pulse pressure variability of radial artery and the dorsalis pedis artery was well?r²=0.79,P<0.05?,The bias was?-0.4±1.4?%.4.After patients receiving ephedrine,pulse pressure variation of the radial arterial decreased from 8.3%to 6.8%?P<0.05?;the pulse pressure variation of dorsal artery decreased from 9.7%to 6.3%?P<0.05?.5.Compared with the waveform of the dorsalis pedis artery,there were more abnormal waveforms occurring in the radial artery?P<0.05?.ConclusionIn the prone position of neurosurgery,the systolic pressure of the invasive radial artery and the dorsalis pedis artery was different,but the mean arterial pressure and pulse pressure variation was smaller difference.