Steven McGee, MD; William B.
Abernethy III, MD; David L. Simel, MD, MHS
ABSTRACT
Objective To review, systematically, the physical
diagnosis of hypovolemia in adults.
Methods We searched MEDLINE (January 1966-November
1997), personal files, and bibliographies of textbooks on physical diagnosis
and identified 10 studies investigating postural vital signs or the capillary
refill time of healthy volunteers, some of whom underwent phlebotomy of up to
1150 mL of blood, and 4 studies of patients presenting to emergency departments
with suspected hypovolemia, usually due to vomiting, diarrhea, or decreased
oral intake.
Results When clinicians evaluate adults with suspected
blood loss, the most helpful physical findings are either severe postural
dizziness (preventing measurement of upright vital signs) or a postural pulse
increment of 30 beats/min or more. The presence of either finding has a
sensitivity for moderate blood loss of only 22% (95% confidence interval [CI],
6%-48%) but a much greater sensitivity for large blood loss of 97% (95% CI,
91%-100%); the corresponding specificity is 98% (95% CI, 97%-99%). Supine
hypotension and tachycardia are frequently absent, even after up to 1150 mL of
blood loss (sensitivity, 33%; 95% CI, 21%-47%, for supine hypotension). The
finding of mild postural dizziness has no proven value. In patients with
vomiting, diarrhea, or decreased oral intake, the presence of a dry axilla
supports the diagnosis of hypovolemia (positive likelihood ratio, 2.8; 95% CI,
1.4-5.4), and moist mucous membranes and a tongue without furrows argue against
it (negative likelihood ratio, 0.3; 95% CI, 0.1-0.6 for both findings). In
adults, the capillary refill time and poor skin turgor have no proven
diagnostic value.
Conclusions A large postural pulse change (≥30
beats/min) or severe postural dizziness is required to clinically diagnose
hypovolemia due to blood loss, although these findings are often absent after
moderate amounts of blood loss. In patients with vomiting, diarrhea, or
decreased oral intake, few findings have proven utility, and clinicians should
measure serum electrolytes, serum blood urea nitrogen, and creatinine levels
when diagnostic certainty is required.
CLINICAL SCENARIOS
In each of the following clinical scenarios, clinicians need
to identify which physical signs reliably and accurately indicate volume depletion
or dehydration.
Case 1
A 54-year-old man, taking ibuprofen for knee arthritis,
presents with a 1-day history of melena. Physical examination reveals a pulse
of 80/min and blood pressure (BP) of 140/82 mm Hg when supine, and 115 and
132/86 mm Hg when standing. There is mild epigastric tenderness and
hemoccult-positive stool. The hematocrit is 0.39.
Case 2
A 62-year-old woman has 6 months of episodic vertigo and
unilateral hearing loss, attributed to Ménière disease. She begins treatment
with hydrochlorothiazide, but during a follow-up visit 3 weeks later, she
reports her dizziness is slightly worse since starting the medication. Her
heart rate is 80/min and BP is 160/84 mm Hg when supine, 88 and 134/72 mm Hg
when standing. She experiences slight dizziness when standing.
Case 3
An 82-year-old nursing home resident presents to the
emergency department with a 1-day history of nausea and vomiting. Her
underlying medical problems include dementia, coronary artery disease, atrial
fibrillation, emphysema, and hypertension. She has been treated with aspirin,
isosorbide dinitrate, furosemide, β-agonist inhalers, and lisinopril. The
clinician diagnoses viral gastroenteritis or food poisoning because other
members of the nursing home have an identical illness. On examination, the
patient is afebrile, alert, and demonstrates normal speech and strength. Her
mental status is no different from her baseline. The pulse is 75/min and the BP
is 154/90 mm Hg supine, and 90 and 130/76 mm Hg when upright. The tongue,
mucous membranes, and axillae are moist. Results of an examination of the
heart, lungs, and abdomen and an electrocardiogram are normal.
WHY IS CLINICAL EXAMINATION IMPORTANT?
The term volume depletion describes the loss of
sodium from the extracellular space (intravascular and interstitial fluid) that
occurs after gastrointestinal hemorrhage, vomiting, diarrhea, and diuresis. In
contrast, the term dehydration refers to losses of intracellular
water that ultimately cause cellular desiccation and elevate the plasma sodium
concentration and osmolality.1 This
distinction is important to clinicians (patients with volume depletion exhibit
prominent circulatory instability and should receive 0.9% saline rapidly,
whereas those with pure dehydration may lack circulatory instability and should
receive 5% dextrose, usually more slowly). Most patients presenting with
dehydration, however, also have volume depletion. Moreover, in most clinical
studies of related physical findings, investigators lump the 2 disorders
together, by using as a combined criterion standard either the presence of an
elevated serum urea nitrogen–creatinine ratio (a measure of volume depletion) or
an elevated serum sodium level or osmolality (a measure of dehydration). We
will use the term hypovolemia to collectively refer to both
conditions.
Gastrointestinal tract hemorrhage, the prototype of volume
depletion, is a common and important problem. Hospitalizations for upper
gastrointestinal tract hemorrhage occur in 150/100,000 population per year2 and
are associated with a case fatality rate of 3% to 10%. 2,3 Hypernatremia,
the hallmark of dehydration, affects primarily elderly patients with infections
and poor access to water, accounting for less than 1% of hospital admissions
but associated with a mortality rate exceeding 40%. 4,5 Risk
factors for hypovolemia in the elderly include female sex, age older than 85
years, having more than 4 chronic medical conditions, taking more than 4
medications, and being confined to bed. 6
Clinical examination attempts to address (1) whether the
patient's symptoms are related to hypovolemia and (2) how severely hypovolemic
the patient is. In case 1, symptoms and laboratory data do not gauge the
severity of the gastrointestinal tract hemorrhage. For example, the presence of
melena has been associated with both insignificant (as little as 100 mL of
blood loss)7 and
massive hemorrhage.8 The
admission hematocrit also correlates poorly with the degree of blood loss and
overall mortality,3-10 especially
in cases of persistent or recurrent bleeding, because a decrease in hematocrit is
often delayed 24 to 72 hours after hemorrhage.11-13 In 1 large study,3 however,
postural vital signs were a significant univariate predictor of mortality and
complications. By influencing decisions to hospitalize the patient with
hemorrhage, perhaps even in the intensive care unit, postural vital signs may
be useful to the clinician. But how accurate are they and which component of
the postural change, pulse or BP, provides more meaningful information?
In case 2, the clinician recognizes that hydrochlorothiazide
may benefit patients with Ménière disease14 but
also wonders if the diuretic could be causing volume depletion and aggravating
her dizziness. How significant is the postural decrease in systolic BP of 26 mm
Hg and the mild postural dizziness?
Finally, case 3 differs from case 1 in that the fluid losses
are not directly from the vascular space and that emesis typically has only one
third the sodium concentration of serum. How reliable are findings of postural
vital signs, capillary refill, and moist axilla, tongue, and mucous membranes
in this patient?
METHODS
Using the MEDLINE database for articles from January 1966 to
November 1997, an author (S.M.) used 3 search strategies, all limited to the
English language and to humans 16 years or older, to retrieve all relevant
publications on the bedside diagnosis of hypovolemia. The first strategy used
the search
termsdehydration/di or hypotension, orthostatic or tilt-table
test. The second strategy used exp dehydration orexp
hypotension, orthostatic or exp heart rate and exp
physical examination or exp medical history takingor exp
professional competence or exp "sensitivity and
specificity" or reproducibility of results or observer
variation or diagnostic tests, routine or exp decision
support techniques or Bayes theorem. Finally, textword searches
were completed for skin turgor or acute blood
loss or orthostatic vital signs or (posturaland pulse).
Based on review of titles and abstracts, relevant publications were retrieved.
To complete the search, this author reviewed the bibliographies of these
articles and those of textbooks on physical diagnosis. Studies of the physical
diagnosis of hypovolemia in infants and children were not included in this
review.15-23
Two types of studies are presented. The first group (Table 1) investigated the postural vital signs and capillary refill time in healthy
volunteers, some of whom underwent phlebotomy of up to 1150 mL of blood.
Despite their limitations, these studies are included because they are the only
studies that compare physical signs with objective measurements of blood loss.
A second set (Table 2) included patients presenting to emergency departments with suspected
hypovolemia, usually due to vomiting, diarrhea, or decreased oral intake. Two
authors (S.M. and W.B.A.) independently graded these studies A, B, or C,
according to the criteria that appear in the footnote of (Table 2). There was complete agreement regarding classification.
A random effects model was used to generate summary measures
and confidence intervals (CIs).37-38 The
model was appropriate because the studies of pulse and pressure change in
normovolemic individuals were representative of all such investigations and
included a broad mix of relevant subjects. For studies of diagnostic accuracy,
the random effects summary measures provided suitable benchmarks for
clinicians' use in actual practice and avoided errors when testing for
homogeneity among a number of investigations. Calculations of sensitivity and
specificity derive from graphs or tabulated data that appear in the original article
or were available from the authors of the studies.26,34,35 Those
phlebotomy studies that described their results only as mean and SDs of the
postural change in heart rate and BP, before and after phlebotomy, were
reviewed but excluded from the calculations of sensitivity and specificity.39-42 We
used the method of Simel et al43 to
calculate CIs for the likelihood ratios (LRs).
RESULTS
Postural Vital Signs
When obtaining postural vital signs, clinicians should wait
2 minutes before measuring the supine vital signs and 1 minute after standing
before measuring the upright vital signs, based on investigations of healthy
individuals discussed below. Sitting instead of standing up the patient
markedly reduces the clinician's ability to detect the postural changes induced
by blood loss.24 Clinicians
who count the pulse for 30 seconds and double the result are more accurate than
those using only 15 seconds.44
Within 1 to 2 minutes after standing up from the supine
position, about 7 to 8 mL/kg of blood shifts to the lower body, causing the
thoracic blood volume, stroke volume, and cardiac output to decrease and
circulating norepinephrine levels and systemic vascular resistance to increase.40,41,45- 48 As
revealed in Table 3,
which presents data from 25 studies that investigated the postural vital signs
of more than 3500 normovolemic individuals (ie, during the tilt test, moving
from supine to upright positions by active standing in 97%, by tilt table in
3%), the most prominent finding is an increment in heart rate of 10.9/min (95%
CI, 8.9-12.8/min). This increase usually stabilizes after 45 to 60 seconds in
the upright position.24,45,52,54 The
systolic BP drops slightly by 3.5 mm Hg (95% CI, −1.5 to −5.5 mm Hg),
stabilizing 1 to 2 minutes after standing, 45,54 whereas
the diastolic BP increases by 5.2 mm Hg (95% CI, 2.8-7.6 mm Hg).
The variability of the postural pulse increment observed in
these studies is in part attributable to the patients' ages and perhaps to the
physical examination method. In Table 3,
the mean age from each study correlates inversely with the observed mean pulse
increment (r, −0.50; P = .02; Table 3).
Other studies 47, 56, 61, 62 also
confirm that as patients age, the pulse increment becomes smaller, although no
obvious cutpoint exists that allows the clinician to stratify patients. The
duration of supine rest before the patient stands might also affect variability
of the pulse change, based on the 1 outlier study in Table 3, 25 which
demonstrated a mean postural pulse increment of only 2 beats/min and used the
shortest time of supine rest before having the patient stand (only 1 minute;
all other studies waited at least 2 minutes). Longer periods of supine rest
before standing may produce a greater immediate pulse increment, perhaps by
causing a greater transfer of blood to the legs and decrement in cardiac
output.48-63 Aside
from the patient's age and period of supine rest, however, no other trend was
evident. There was no clear relationship between the postural pulse increment
and period of supine rest beyond 2 minutes, resting supine pulse rate, time
upright before vital signs measurement (all >45 seconds), technique of pulse
measurement (palpation vs automated), setting of the study (emergency
department, prephlebotomy vs other), or method of assuming the upright posture
(active stand vs tilt table).
Based on the studies in Table 3 that
enrolled more than 25 individuals and presented tabulated data (n = 774), the
specificity of a postural pulse increment of 30/min or more (ie, the most
common threshold used in clinical studies) was 96% (95% CI, 92%-98%).
Postural hypotension, defined as a decrement in systolic BP
of more than 20 mm Hg after standing from the supine position, occurs in up to
10% of normovolemic individuals younger than 65 years39-26 and
in 11% to 30% older than 65 years.64-71 Postural
hypotension is more likely if the patient has supine systolic hypertension,58, 67, 68, 71-73 but
is not more likely, surprisingly, if the patient takes cardiovascular or
psychotropic medications. 47, 65, 68, 71, 74 Finally,
the symptom of mild or moderate postural dizziness is a poor predictor of
postural hypotension in most studies.56, 67, 70
Pathogenesis and Definition of Other Physical Findings
The capillary refill time is determined by compressing the
distal phalanx of the patient's middle finger, positioned level with the heart,
for 5 seconds and then timing the return of normal color to the finger. With an
ambient temperature of 21°C, the upper limits of normal for the refill time are
2 seconds for children and adult men, 3 seconds for adult women, and 4 seconds
for the elderly.75
Poor skin turgor refers to the slow return of skin to its
normal position after being pinched between the examiner's thumb and
forefinger.76 The
protein elastin, which is responsible for the recoil of skin, is markedly
affected by moisture content. As little as 3.4% loss in wet weight may prolong
the recoil time 40-fold.76 Elastin
deteriorates with age, suggesting that the recoil of skin normally declines
with age, although this has never been formally studied to the authors'
knowledge. No studies on the normal recoil time nor precise definitions of
technique could be found.
Cellular dehydration, interstitial space dehydration, and
poor perfusion are presumably responsible for many of the other classic signs
of hypovolemia, such as longitudinal tongue furrows, dry mucous membranes, dry
axillae, and sunken eyes. No studies on the pathogenesis of these findings,
however, could be found.
Precision of Physical Signs
Reproducible measurements of BP depend on many variables,
including the examiner's technique, the patient examined, and various observer
biases and errors, all of which are thoroughly reviewed in another article.77
Outside of an extensive literature devoted to patients with
syncope that uses different methods and end points than those discussed in this
article, the few studies of tilt test reproducibility focus more on biological
variation (ie, reproducibility of the test when repeated days later) than on
immediate interobserver reproducibility. In 1 study, which measured postural
vital signs of 911 elderly nursing home residents 4 times during the day,
postural hypotension was present only 1 of the 4 times in 18.3% of the
residents, 2 or 3 times in 19.9%, and all 4 times in only 13.3%.68 Postural
hypotension is more reproducible in the morning than afternoon 68, 76 or
if the patient's cardiovascular medications are withheld (which tends to unmask
supine systolic hypertension, a known risk factor for postural hypotension).58, 73
In acutely ill elderly patients, interobserver agreement for
axillary sweating (dry vs moist) was moderate (κ, 0.50; 80% simple agreement).33 In
addition, the clinician's assessment of axillary moisture correlated well with
the weight gain of a piece of preweighed tissue paper applied to the patient's
axilla for 15 minutes.33Using
stopwatches, the measurements of capillary refill time by 2 observers were
within 0 to 0.3 seconds of each other.75
Accuracy of Physical Signs for Acute Blood Loss
Table 4 reveals
that the 2 most valuable observations from the tilt test are either a postural
pulse increment of 30/min or more or the inability of the patient to stand for
vital signs because of severe dizziness. After blood loss of 450 to 630 mL,
only 1 in 5 patients demonstrate these findings. The sensitivity increases to
97% (95% CI, 91%-100%) after 630 mL to 1150 mL blood loss. The specificity is
98% (95% CI, 97%-99%), a value similar to that generated from the studies
in Table 3.
Either of these findings is durable after hemorrhage, lasting at least 12 to 72
hours if intravenous fluids are withheld.11, 30, 39 If
the patient sits instead of stands up from the supine position, the sensitivity
decreases, being 39%24and
78%30 in
2 studies after 1000 mL of hemorrhage. Because the studies of large blood loss
(630-1150 mL) enrolled younger healthy individuals, the sensitivity may also be
lower in elderly patients or those taking medications such as β-blockers. The
patient complaint of postural dizziness, not severe enough to prevent standing
and accompanied by a pulse increment lower than 30/min, has little predictive
value. 25, 56
After excluding those unable to stand for vital signs,
postural hypotension (a more than 20-mm Hg decrease in systolic BP) has little
additional predictive value. Its sensitivity for 450 to 630 mL of blood loss is
only 9% in those younger than 65 years and 27% in those older than 65 years.
These numbers are similar to the false-positive rates in some studies of the
same age groups, 10% (<65 years)26 and
28% (>65 years),71 resulting
in positive LRs close to unity. There are insufficient data to address the
value of isolated postural hypotension after 630 to 1150 mL of blood loss.
Supine tachycardia (pulse >100/min) is a specific but
insensitive indicator of blood loss (96% specificity). Thus, patients without
supine tachycardia can still have significant blood loss. In contrast,
bradycardia occurs frequently after significant blood loss, often immediately
preceding the decrease in systemic vascular resistance and the fainting that
may occur. 11,27-32, 39, 79-81One
study80 showed
a strong correlation between the decrease in heart rate after blood loss and
the maximal decrease in BP (r, 0.79), and, in hypotensive patients receiving
fluid resuscitation, the pulse may paradoxically rise initially.81
In patients with suspected blood loss, supine hypotension
(systolic BP <95 mm Hg) is a specific finding of hypovolemia (97%
specificity), although it is insensitive to both moderate blood loss of 450 to
630 mL (13% sensitivity) and more significant loss of 630 to 1150 mL (33%
sensitivity).
Using the age- and sex-specific upper limits of normal for
capillary refill time defined earlier, a prolonged refill time does not
accurately predict 450 mL of blood loss (6% sensitivity and 93% specificity)
and yields a positive LR of 1.0.36 If
the clinician instead uses an arbitrary upper limit of 2 seconds, diagnostic
performance is no better (11% sensitivity, 89% specificity, positive LR, 1.0).36
Accuracy of Physical Signs for Other Causes of Hypovolemia
Table 5 reviews
the sensitivity and specificity of various physical signs for the diagnosis of
hypovolemia derived from studies of individuals usually presenting to emergency
departments with vomiting, decreased oral intake, or diarrhea. Except for 1
study,35 which
enrolled young women with hyperemesis gravidarum, these studies generally
recruited older adults.
The finding of a dry axilla increases the probability of
hypovolemia (positive LR, 2.8; 95% CI, 1.4-5.4), although it is an insensitive
physical sign (50% sensitivity).33 The
finding of a moist axilla decreases the probability of volume depletion only
slightly (negative LR, 0.6; 95% CI, 0.4-1.0).
In the study by Johnson et al35 of
23 women with hyperemesis gravidarum, neither postural hypotension nor a
postural pulse increment of more than 30/min was particularly helpful (Table 5).
In this study, however, the specificity of a pulse increment of more than
30/min was unusually low (75%). One possible reason for this could be the
authors' definition of dehydration (≥5% weight gain after 12 hours of
rehydration), which led them to classify as nondiseased the dehydrated women
with less than 5% weight gain, thus devaluing the specificity calculation.
Alternatively, the postural pulse increment may be less specific because of
pregnancy.
In another study of 202 individuals with acute illnesses,
investigators used multiple analysis of variance to identify which clinical
findings best explained the variation in total body water deficit, as
calculated from the patient's serum osmolality.59 The
finding of a dry axilla was significantly associated with level of dehydration
(P = .03). The postural pulse increment was also significantly associated
but only weakly so (r, 0.22; P = .02).59 The
mean water deficit in this study was only 3.9%, correlating with a 140-mL
deficit from the vascular space (or about 250 mL of blood), a level below that
in the phlebotomy studies discussed earlier. This study found no association
between dehydration and postural changes of systolic BP.
In Table 5,
the capillary refill time seems to perform impressively, especially when the
capillary refill time is prolonged (positive LR, 6.9).36 However,
the criterion standard in this study was the supine and postural vital signs,
raising the question whether capillary refill time has any incremental
diagnostic value. Another study found no correlation between capillary refill
time, tested over the patella, and objective measures of hypovolemia.34
In a study of 55 elderly patients presenting with suspected
hypovolemia, the 7 physical signs of confusion, extremity weakness, nonfluent
speech, dry mucous membranes, dry tongue, furrowed tongue, and sunken eyes
correlated best with measurement of the serum sodium and serum urea
nitrogen–creatinine ratio (Table 5).34 Based
on the CIs of the LRs, however, none of these findings is particularly helpful
when present in isolation. Combinations of findings may be more helpful—on
average, patients with severe and moderate hypovolemia had 5.7 and 3.9,
respectively, of these 7 signs, whereas those without dehydration had only
1.3—but this requires validation.34The
most helpful negative findings, arguing against hypovolemia, are moist mucous
membranes, absence of sunken eyes, and absence of furrows on the tongue.
Another study found no correlation between degree of
hypovolemia and dryness of mucous membranes.59 In
adults, 2 studies have found poor skin turgor to have no diagnostic value.34, 59
THE BOTTOM LINE
When obtaining postural vital signs, clinicians should wait
at least 2 minutes before measuring the supine vital signs and 1 minute after
standing before measuring the upright vital signs. Counting the pulse for 30
seconds and doubling the result is more accurate than 15 seconds of
observation.44 In
normovolemic individuals, a postural pulse increment of more than 30 beats/min
is uncommon, affecting only about 2% to 4% of individuals.
When evaluating patients with suspected blood loss, the most
helpful physical findings are severe postural dizziness (preventing measurement
of upright vital signs) or a postural pulse increment of 30 beats/min or more.
Having the patient sit instead of stand reduces the sensitivity of the tilt
test. After excluding those unable to stand, postural hypotension has no
incremental diagnostic value.
Supine hypotension and tachycardia are frequently absent,
even with more than 1000 mL of blood loss, and the symptom of mild postural
dizziness has no proven diagnostic value. Bradycardia is common after
significant blood loss.
Rigorous conclusions about the role of physical examination
in assessing the volume and hydration status of patients with vomiting,
diarrhea, or decreased oral intake are difficult to make because there are few
studies. Severe postural dizziness or a postural pulse increment of 30
beats/min or more should be just as accurate as after blood loss, although 1
study of the pulse increment in patients with hyperemesis gravidarum failed to
confirm this. A dry axilla supports the diagnosis of hypovolemia in the
elderly, and moist mucous membranes and a tongue without furrows argue against
it. However, clinicians should recall that the criterion standard of
hypovolemia in these studies—simple serum chemistry measurements—is easily accessible
to clinicians. When applying these findings to practice, until further data are
available, clinicians should have a low threshold for ordering tests of serum
electrolytes, serum blood urea nitrogen, and creatinine. In adults, the
capillary refill time and poor skin turgor have no proven diagnostic value.
Case 1 demonstrates a postural pulse increment of more than
30 beats/min, suggesting significant blood loss. The clinician should admit
this patient to the hospital for fluid resuscitation and further testing. In
case 2, postural hypotension and mild postural dizziness lack the specificity
necessary to condemn the diuretic at this time. The clinician should continue
the diuretic if he believes the patient's dizziness resembles inner-ear
vertigo. Finally, despite the negative physical examination findings in case 3,
this patient has many risk factors for significant hypovolemia, and the
clinician should measure the serum blood urea nitrogen, creatinine, and
electrolytes before making the decision to discharge the patient.
The Rational Clinical Examination Section Editors:David L.
Simel, MD, MHS, Durham Veterans Affairs Medical Center and Duke University
Medical Center, Durham, NC; Drummond Rennie, MD, Deputy Editor (West), JAMA.
Virtual Journal Club June 2015: CME Questions
1.
Historically orthostatic vital signs have been taught as a useful method for determining
a patient’s ____________ status.
a a. payment
b b. mental
c c. volume
d d. marital
2.
Traditionally orthostatic measurements are taken after a patient stands from a
supine position; and are defined as either:
a. An increase in systolic blood pressure > 20 mm Hg; or a
decrease in heart rate by > 30 beats per minute.
b b. A drop in systolic blood pressure > 20 mm Hg; or an increase
in heart rate by > 30 beats per minute.
c c. A drop in diastolic blood pressure > 30 mm Hg; or an increase
in heart rate by > 20 beats per minute.
d d. A drop in systolic blood pressure > 20 mm Hg; or a decrease
in heart rate by > 30 beats per minute.
3.
True or False: pooled data suggests that when diagnosing patients with moderate
blood loss (450-630 mls) a pulse increase of greater than 30 beats per minute
or severe postural dizziness was only 22% sensitive for hypovolemia.
4. True or
False: The diagnostic accuracy of postural vital signs for ‘hypovolemia not due to blood loss’ showed
that a pulse increase of greater than 30 beats per minute was only 43%
sensitive and only 75% specific.
5. True or
False: The diagnostic accuracy of postural vital signs for ‘hypovolemia not due to blood loss’ showed
that a systolic blood pressure decline of greater than 20 mm Hg was only 29%
sensitive and only 81% specific.
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