|Year : 2016 | Volume
| Issue : 1 | Page : 52-56
Correlation between central venous and peripheral venous pressures in surgical patients
Rajan Sunil, Nadarajan Vishnu, Kumar Lakshmi
Department of Anaesthesiology and Critical Care, Amrita Institute of Medical Sciences and Research Centre, Kochi, Kerala, India
|Date of Submission||12-Jul-2014|
|Date of Acceptance||25-Sep-2014|
|Date of Web Publication||17-Mar-2016|
Department of Anaesthesiology and Critical Care, Amrita Institute of Medical Sciences and Research Centre, Amrita Vishwa Vidyapeetham, Kochi, Kerala
Source of Support: None, Conflict of Interest: None
The central venous pressure (CVP) measurement is important in assessing right ventricular function and systemic fluid status, and the venous pressures measured from peripheral venous catheters closely correlate with CVP and/or CVP trends. The correlation between CVP and peripheral venous pressure (PVP) in patients undergoing major surgical procedures under mechanical ventilation during normotension, hypotension, in the presence of inotropes, and postoperatively during spontaneous respiration was studied in this study.
Materials and methods
In this prospective, observational study, 40 adult patients undergoing surgical procedures lasting for more than 5 h, where a major blood loss was expected, were studied. The CVP and PVP were recorded simultaneously at a 15 min interval until 4 h intraoperatively, followed by hourly during the postoperative period for 4 h. Statistical analysis used Student's t-test to analyze statistical significance of difference in mean, Pearson's product moment correlation coefficient to assess correlation, and paired t-test to assess changes in mean arterial pressure.
Throughout the study period, PVP persistently showed a positive trend with a significantly higher value than CVP (P < 0.001), but a statistically significant correlation could not be demonstrated persistently.
Hence, it is concluded that measurement of PVP can be considered as an alternative to CVP monitoring, when conditions are impractical for central venous catheterization.
Keywords: central venous pressure, peripheral venous pressure, major surgery, hypotension
|How to cite this article:|
Sunil R, Vishnu N, Lakshmi K. Correlation between central venous and peripheral venous pressures in surgical patients. Ain-Shams J Anaesthesiol 2016;9:52-6
|How to cite this URL:|
Sunil R, Vishnu N, Lakshmi K. Correlation between central venous and peripheral venous pressures in surgical patients. Ain-Shams J Anaesthesiol [serial online] 2016 [cited 2019 Sep 18];9:52-6. Available from: http://www.asja.eg.net/text.asp?2016/9/1/52/178880
| Introduction|| |
The central venous pressure (CVP) measurement is important in assessing right ventricular function and systemic fluid status and is a reflection of cardiac function and the venous return to the heart. Studies have demonstrated that venous pressures measured from peripheral venous catheters closely correlate with the CVP and/or CVP trends in both surgical ,,, and critically ill patients ,, . In the present study, the correlation between CVP and peripheral venous pressure (PVP) in patients undergoing major surgical procedures under mechanical ventilation during normotension, hypotension, in the presence of inotropes, and postoperatively during spontaneous respiration was assessed.
| Materials and methods|| |
On the basis of the results observed in the existing literature and the correlation coefficient between CVP and PVP, with 99% confidence and 90% power, the minimum sample size comes to 30. Study was conducted from December 2011 to December 2013, in 40 adult American Society of Anesthesiologists physical status (ASA) I and II patients, aged 20-60 years, undergoing major surgical procedures lasting for more than 5 h, where a major blood loss intraoperatively was expected.
Patients were included in the study after taking consent from patient and after obtaining approval from Hospital ethical committee. Patients in whom peripheral intravenous lines were difficult to obtain, with history of deep vein thrombosis, and those undergoing cardiovascular surgery were excluded.
All patients received anesthesia observing a standardized anesthesia protocol. Venous access was obtained with an 18-G canula, and Ringer's lactate solution was started and maintained following the Holliday-Segar formula. All patients received glycopyrolate 0.2 mg followed by fentanyl 2 mcg/kg body weight and midazolam 2 mg intravenously. Induction of anesthesia was obtained with propofol 2 mg/kg body weight after preoxygenating with 100% oxygen for 3 min. Following loss of response to verbal commands, vecuronium 0.1 mg/kg body weight was given and the patients were mask-ventilated with a mixture of O 2 and isoflurane (99 : 1%) and intubated after 3 min.
Anesthesia was maintained with O 2 , N 2 O, and isoflurane (33 : 66 : 1%), and vecuronium 1 mg was repeated every 30 min. Patients were ventilated with a tidal volume 6-8 ml/kg body weight and respiratory rate of 12-15/min maintaining end tidal carbon dioxide between 30 and 35 mmHg.
A central venous catheter was put through the subclavian or internal jugular vein using a 7 F triple lumen catheter, and a peripheral line was put in the cubital fossa using a 16-G intravenous canula. Both lines were connected to two separate transducers and values of CVP and PVP along with mean arterial pressure (MAP) were recorded simultaneously at 15 min interval until the completion of 4 h. Four readings during the postoperative period were again taken at 1-h interval when patients were normotensive and breathing spontaneously.
Intraoperatively, hypotension was defined as a 20% decrease in MAP from the preinduction value, which was initially treated with a bolus 200-300 ml of a crystalloid solution. Hypotension following blood loss of more than 10% of total blood volume was treated with equal volumes of colloid. Blood was replaced if there was blood loss more than 20% of the total blood volume. Number of patients requiring vasopressors during the study period was also noted.
To test the statistical significance of difference in mean value, Student's t-test was applied. Pearson's product moment correlation coefficient was computed between CVP and PVP, and their statistical significance was tested. To test the statistical significance of change in MAP from basal value to different points of time, paired t-test was performed. Data were analyzed using statistical package for social sciences (SPSS version 20; IBM, Bengaluru, India).
| Results|| |
The patients included in the study had a mean age of 47.4 ± 11.6 years, a mean weight of 69 ± 8.4 kg, and a mean height 162.7 ± 7.9 cm. In all, 60% patients were ASA I and 65% were women.
While comparing the mean intraoperative CVP and PVP, it was found that PVP always had a significantly high value throughout the study period, compared with CVP (P < 0.001), the difference being minimum at 15 min (17.1 vs. 10.1) and maximum at 195 min (15.1 vs. 5.9) [Table 1], [Figure 1]. However, the statistical interpretation of correlation revealed that there was a positive correlation existing only at 15 and 240 min (correlation coefficient r = 0.353, P = 0.025 and r = 0.356, P = 0.024, respectively), although there was a positive trend [Table 2].
|Figure 1: Comparison of intraoperative CVP and PVP. CVP, central venous pressure; PVP, peripheral venous pressure|
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Similarly, during the postoperative period also, PVP persistently showed a significantly high value until 4 h (P<0.001, [Table 3], [Figure 2]. However, irrespective of a positive trend, on statistical analysis, there was no significant correlation between CVP and PVP [Table 4].
|Figure 2: Comparison of postoperative CVP and PVP. CVP, central venous pressure; PVP, peripheral venous pressure|
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The comparison of changes in MAP from baseline value showed that there was a statistically significant increase in MAP during 45-90 min. No significant decrease in mean MAP was noticed during the study period [Table 5]. While comparing the mean intraoperative blood loss, it was found that there was a significantly high blood loss during second, third, and fourth hours [Table 6], [Figure 3]. However, the maximum number of patients who developed intraoperative hypotension was only 10%. Similarly, the maximum number of patients who required vasopressors was also 10% [Table 7].
| Discussion|| |
Although it is mandatory to insert catheters into peripheral veins of all surgical patients, measurement of PVP from those veins is not commonly practiced. Despite the more invasive nature of the procedure and inherent complications involved with central venous cannulation, anesthesiologists are accustomed to monitoring CVP.
As PVP is linked to CVP by a continuous fluid column, comparing them usually shows a consistent correlation. Studies have demonstrated that pressures measured from peripheral venous catheters closely estimate the CVP and/or CVP trends ,,,,, . As the difference between CVP and PVP measurements usually remain in a constant range, serial assessment of PVP can be used to monitor the changes occurring in CVP during intraoperative bleeding, hypotension, or mechanical ventilation, the advantages being cost effectiveness and avoidance of complications associated with central venous catheterization.
In the present study, it was shown that PVP always had a significantly high value compared with CVP throughout the study period (P<0.001) showing a positive trend. This observation is supported by previous studies by Munis et al.  , Amar et al.  , Desjardins et al.  , Tobias et al.  , and Charalambous et al.  .
Although there was a positive trend between CVP and PVP at 15 and 240 min in the present study, no statistically significant correlation could be demonstrated during the rest of the study period. However, most of the previous studies had shown a definite positive correlation between the two ,,,, . This could be explained by the fact that most of the previous studies were conducted on specific group of patients, such as neurosurgical  , cardiothoracic , , liver transplant , , laparoscopic colorectal surgery  , or critically ill intensive care unit patients  .
Our study population included patients undergoing craniofacial resection, maxillectomy, hepatectomy, and laparotomy for gynecological malignancies. The position of patients and position of hands during surgery varied with each procedure. During craniofacial resections and maxillectomy, a 20°-30° head up position was used and the hands were kept by side of the body, whereas during laparotomy for gynecological malignancies, a head low position was used and the hands were kept abducted to almost 90° intraoperatively. In addition, surgical retractors and intra-abdominal packs were also used intraoperatively, which could also influence venous pressures. There is a possibility of changes in PVP value with different hand positions such as adduction or abduction, as the flow through the vein might get impeded reflecting as a false increase in PVP.
Hence, in case of an individual patient, the CVP and PVP values might have had a definite correlation. However, when the mean values in a group of patients in whom different factors might have influenced CVP and PVP were compared, the correlation might have failed to manifest.
Although the analysis of blood loss showed a significant loss intraoperatively during the second, third, and fourth hour, it did not manifest as significant hypotension when the mean values of MAP were compared. It could be because the numbers of patients who developed hypotension or needed vasopressors to maintain normotension were not significantly high or because the hypotension was corrected rapidly with crystalloids, colloids, and blood.
Limitations of the study include small sample size and not standardizing patient position and position of hands during surgery. Another drawback was that CVP and PVP values at onset of hypotension and following fluid therapy were not separately documented; hence, response to correction of hypovolemia with fluids and vasopressors separately could not be assessed.
| Conclusion|| |
As the changes in CVP parallel the changes in PVP showing a definitive positive trend, measurement of PVP can be considered as an alternative to CVP monitoring, when conditions are impractical for central venous catheterization.
| Acknowledgements|| |
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5], [Table 6], [Table 7]