Only the SVV was an adequate predictor of fluid responsiveness in this cohort of high risk surgical patients. Whereas PPV and SPV may be obtained from the arterial trace, estimation of the SVV requires a cardiac output monitor which is able to convert an arterial pressure trace into an estimation of stroke volume.

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Introduction: Postural Orthostatic Tachycardia Syndrome (POTS) is a form of dysautonomia which primarily affects young adult women. The hallmark of this condition is an exaggerated heart rate in response to postural changes. The symptoms of POTS can cause cerebral hypoperfusion and include generalized weakness, dizziness, lightheadedness, darkening of the visual fields and in some, palpitations and loss of consciousness. Increased sympathetic activation results in increase of the conduction through the AV node. Increased conduction through the AV node results in a shorter PR interval and a faster heart rate. The aim of this study is to determine if patients with severe POTS have resting Adrenal Hyperactivity by utilizing PR-Intervals. Methods: A team of researchers randomly selected pts with POTS from our clinic. This group consisted of 455 pts and these pts’ tilt table results as well as their resting ECG’s were reviewed from their electronic medical records. Pts were then categorized based on the degree of change in heart rate during the tilt table test. The categories were as follows: Orthostatic intolerance (<30 bpm), mild POTS (30-50 bpm), and severe POTS (>50 bpm). A few patients in the data set did not have tilt table results and were subsequently removed. We noted the resting PR intervals of these pts from their multiple ECG’s. For each pt the mean of these values was gathered and biostatistical analysis was performed on this first collection of data. After the first data was analyzed, a second team of researchers, blinded to the first team, collected the same data set on patients with POTS from our clinic. This was done in order to minimize observer bias and reproduce results. This team of researchers further filtered out 8 patients whose data did not meet the criteria required to categorize the patients, thus the second data set consisted of 447 pts. Tilt table results and resting PR intervals were taken from their electronic medical records and the pts were then categorized in the same manner as the first data set. Results: In the second group of 447 pts (n=447), 28.6% (n= 128) are categorized as having orthostatic intolerance, 51.6% (n=231) are categorized as mild POTS, and 19.6% (n=88) are categorized as severe POTS. Using a significance level of 0.05, the P-value was lower than 0.05 (0.00787), thus ANOVA fails to accept the null hypothesis that the means of the PR-intervals across the various categories are equal. That is to say, statistically the resting PR intervals are not equal across the different POTS categories in both groups with a significance level of 0.05. Average P-R (Severe POTS:137.0 ms & Orthostatic Intolerance: 145.59 ms) Conclusion: A statistically significant increase in resting Adrenal Hyperactivity in pts with severe POTS (>50 bpm) as opposed to pts with Orthostatic Intolerance (<30 bpm); the severity of which may have long-term prognostic significanc...