Thursday 29 March 2012

Uroflowmetry: definition, procedure, indications and types

Definition:
        Uroflowmetry is a simple, diagnostic screening procedure used to calculate the flow rate of urine over time.

        The test is noninvasive (the skin is not pierced), and may be used to
  assess bladder and sphincter function.
 
 Uroflowmetry:
        The measured urinary flow is a product of detrusor contractility and urethral resistance,in some cases modified by abdominal straining.

        Even though uroflowmetry is not specific in identifying outlet obstruction ,the flow rate remains an extremely sensitive indicator of lower urinary tract symptoms.
        Today most commercially available uroflowmeters are based on –

 1)Weight transducers, measuring voided volume and calculating flow rate by means of differentiation with respect to time.


 2) Rotating disc, measuring the power necessary to maintain a constant rotation ,where as urine tends to slow down the speed.

Procedure:

        Uroflowmetry is performed by having a person urinate into a special funnel that is
   connected to a measuring instrument.

         The measuring instrument calculates the amount of urine, rate of flow in seconds, and length of time until completion of the void. This information is converted into a graph and interpreted by a urologist.

        The information helps to evaluate function of the lower urinary tract or help determine if there is an obstruction of normal urine outflow.
Indications :
        1- Benign prostatic hypertrophy (BPH).
        2-Cancer of the prostate, or bladder tumor.
        3- Urinary incontinence - involuntary release of urine from the bladder.
        4- Urinary blockage - obstruction of the urinary tract can occur for many reasons along any part of the urinary tract from kidneys to urethra. Urinary obstruction can lead to a back-flow of urine causing infection, scarring, or kidney failure if untreated. 
          5- Neurogenic bladder dysfunction - improper function of the bladder due to an alteration in the nervous system such as a spinal cord lesion or injury. 
          6- Frequent urinary tract infections (UTI’s).

   Uroflowmetry may be performed in conjunction with other diagnostic procedures, such as cystometry and cystography.
Uroflowmetry :
        Properly performed uroflow rate determination should specify:
    - voided volume
    - patient environment and position
    - filling : by diuresis or by catheter
    - type of fluid voided
    - type of measuring equipment
    - solitary procedure or combined  with other measurements

Definitions :
        Voided volume : The total volume of urine expelled from the bladder.

        Residual urine volume : The total volume of urine remaining in the bladder after voiding.

        Flow time : The time over which measurable flow actually occurs.

        Maximum flow rate(Qmax): The maximum measured value of the flow rate.
        Time to maximum flow : the elapsed time from the onset of flow to the point of maximum flow.

        Mean flow rate(Qmean):  volume voided divided by flow time.


        Continuous urinary flow : a constant urinary stream without interruption
Types of flow curve patterns


        Type 1 : The normal flow curve is unbroken and bell shaped with only slight to moderate asymmetry of the bell.
   
        Type 2: The prostatic curve is unbroken with pronounced asymmetry and an elongated ,flattened course from Qmax to end of voiding.
Type-2

   
        Type 3 : The fluctuating flow curve is unbroken but characterized by greater fluctuations without reaching zero before the end of voiding.
        Type 4 : The fractionated flow curve is discontinuous. 
        Type 5 : The plateau flow curve is unbroken and a large part of the voided volume is voided by a constant Qmax.
Types 1,3,4,5










 Normal urinary flow:
 

        The normal flow pattern is a continuous, bell-shaped, smooth curve with a rapidly increasing flow rate .

        Because small voided volumes affect the curve shape and Qmax is volume dependent, only voided volumes of at least 150 ml should be interpreted .

        The maximum flow rate should always be documented together with the total voided volume and post void residual volume with the following standard format: maximum flow rate/volume voided/post void residual volume.

        Uroflow in men :
    Most consider Qmax greater than 15 to 20 ml/sec as normal and less than 10 ml/sec abnormal. These numbers decline with age by 1 to 2 ml/sec per 5 years. There is a decline in peak flow with age resulting in a maximum flow of 5.5 ml/sec at 80 years .

        Uroflow in women :
   In the normal woman Qmax can be greater than 30 ml/sec, the flow curve is bell shaped as in men, and the flow time is shorter. Maximum flow in women does not seem to be dependent upon age.

 
Pitfalls:
        Electronic analysis of uroflowmetry may introduce errors because the electronic device reads the absolute maximum value recorded by the machine and may read spikes on the curve that do not represent true flow .

        Bladder over distension may be responsible for artifacts during uroflowmetry.

        Another pitfall during uroflow evaluation is that of measuring only one flow parameter, such as peak flow.

Conclusion :
        Accurate measurement of the urinary flow rate provides important and useful information that may indicate the presence of bladder outlet obstruction.

        Careful examination of the flow pattern may indicate a possible etiology for an abnormal flow pattern.

        The uroflow by itself, can neither diagnose bladder outlet obstruction nor predict which patients will benefit from surgery to relieve obstruction.

        In view of its limitations ,in circumstances in which doubt remains after a uroflow study,further complex urodynamic studies are needed to identify the etiology of voiding dysfunction.

Wednesday 28 March 2012

Labor induction: history, physiological background, different methods of labor induction.

Labor is a process through  which the fetus moves from the  intra uterine to extra uterine environment . It is a clinical diagnosis defined as the initiation and perpetuation of uterine contractions with the goal of producing progressive cervical effacement and dilatation and expulsion of fetus and after births.

 Induction of labor :
Refers to the process whereby uterine contractions are initiated  by medical  means before the onset of spontaneous labor with the intension to have vaginal delivery. Occasionally it may end in cesarean section or instrumental delivery.

Historical introduction :
    The need to time delivery has been recognized and practiced for centuries. Although the indications have clearly changed during the past 200 yrs from a need to expel a dead fetus to the pre-emptive action to reduce the threat to fetal or maternal health. Effective and safe methods of achieving delivery   always have been the primary objectives.
                  A number of folkloric or old midwives tales used at those days and are still used today by women to encourage their labor to start.  Among the more common approaches are  frequent walking,   vaginal intercourse, participating in heavy exercise, consumption of laxatives, spicy foods or herbal tea, nipple stimulation and administration of a purgative.
                                  Most methods of inducing labor before the last half century involved mechanical manipulations, including Galvinism, repeated pressurized douches, extra-amniotic aqua pica, tents, bougies, catheters.The issue of threats, incantations and chants was doubtless popular when nothing else was on hand. While the administration of potions and later castor oil, quinine and posterior pituitary extract were also utilized.
                     Less well known approaches include taking a hot both, dancing, eating Chinese food, drinking warm gin or cranberry juice and riding in a car over a bumpy road.
                     During the last 40 yrs, labor induction has mostly involved combining the recognized advantages of physical manipulation with a pharmacological myometrial stimulant like oxytocin.
                                         For  the last 30 yrs the state of uterine cervix has been recognized as having a major influence on success of attempts to induce labor. It is common practice to describe methods of labor induction used when the cervix is unripe or unfavorable and those used when cervix is favorable. In reality it is continuum.
                                In  the 1980s and 1990s patient’s acceptance of when and how delivery was achieved became a significant and sometimes over powering consideration, but has not necessarily always been in the long term best interests of mother or fetus.
                       In some countries the fear of legal redress if the pregnancy outcome is not entirely favorable has become so concerning that the patient demands are frequently acquiesced to and in many cases, requests for delivery  by cesarean section are agreed although there is no clear medical indication.      


 Physiological back ground:
The cervix is essential in maintaining uterine stability during pregnancy. To achieve this, the maintenance of cervical shape and consistency is imperative since cervical ripening is a physiological process occurring throughout the latter weeks of pregnancy and is completed with the onset of labor. When delivery is necessary and ripening has not had time to occur, or has failed to be initiated, the natural process has to be accelerated.
The cervix possesses a unique construction  to enable it to perform its various roles.
It consists predominantly of a stromatous body of connective tissue that can be subdivided into a superficial loose zone and deeper dense stromal zone. The main element of this connective tissue are collagen together with a small amount of elastic tissue and an even smaller component of muscle fibers. The collagen is composed of dense regular fibrils arranged in parallel bundles held together by cross-links, with a few interspersed mast cells and other cellular elements.
The ground substance is composed of proteoglycan complexes consisting of glycosaminoglycan side chains (GAGs) on core proteins linked to a hyaluronic acid chain that bind tightly. The dominant GAGs in the cervix are dermatan sulphate and chondroitin sulphate, both of which contain hyaluronic acid conferring additional binding strength and have hydrophilic properties.
In the ground substance fibroblasts with numerous long cytoplasmic processes radiating from one cell to another are found these are possibly similar to myometrial gap junctions, infiltrating the ground substance.
With the advance of pregnancy, increased vascularity is seen and fibroblasts become secretory, white cells and macrophages migrate out of vessel walls in to the cervical stroma with an increase in water content. There is a reduction in collagen content and relative increase the glucoronic acid  containing GAG heparin sulphate that binds much less strongly.  Enzymatic beak down of collagen fibrils by collagenases or matrix metalloproteinases  produced by fibroblasts and polymorphonuclear leukocytes alongside leukocyte elastase which catabolises elastin, leads to increased cervical compliance.
                              The precise mediation and inter- relationships remain to be elucidated , but the prostaglandins and their synthase inhibitors are closely implicated with the known increase observed as pregnancy advances.
                                Significantly there is reasonably strong evidence that the process of cervical ripening will occur without any detectable uterine contractions.
 Cytokines , notably IL-8 or platelet activating factor PAF and monocyte chemotactic protein - 1 (MCP-1)  have been proposed as possible interactants in the remodeling process involved in cervical ripening, as has nitric oxide,synthesized by macrophages, myometrium and the cervix.
 As yet , the precise role if any, for these agents in this physiological process  remains to be elucidated.

Current methods of inducing labor :
The methods of induction of labor used at present are,
A. Mechanical methods
B. Pharmacological methods
C. Surgical methods
                                                                                                                                  
A. Mechanical methods:
All mechanical modalities share a similar mechanism of action, that is
exerting some form of local pressure that stimulates the release of
prostaglandins.
Eg. Hygroscopic dilators 
Laminaria japonicum and synthetic osmotic dilators  eg. Lamicel.
Balloon catheter

B. Pharmocological methods:
Oxytocin :
 Du Vignaeaud synthesized syntocinon from the nona- peptide oxytocin in the 1950s . It has been used by intravenous infusion for the majority of women having their labor induced. 
Although still used as primary induction agent occasionally, it is more frequently given to assist the induction process using prostaglandins when the cervix is unfavorable or an adjunct to low amniotomy in more favorable cases.
         These are usually set as starting rate around 1 to 4 mu / min and increases variably, either arithmetically  or logarithmically at 15 to 30 min intervals often to a maximum of around 32 mu/min  or  until satisfactory labor has been established, occasionally higher rates may be required. Because of the ease of turning off the oxytocin infusion, they suggested that this method may have a preferential role in high risk patiens whose fetuses are at increased risk for intolerance of labor.

Prostaglandins :
By the mid 1980s prostaglandins had become established as the most effective pharmacological agents for inducing labor when the cervix is unripe.  A variety of administration routes had been employed during the preceding years, including  oral , intravenous, sublingual, rectal, intra amniotic, extra amniotic, intra cervical,  and vaginal administration. The vaginal route is found to be the most acceptable, providing good efficacy and acceptability for the parturient and is now the preferred method of choice. Prostaglandin E2 (dinoprostone) is licensed for the use of labor induction in the cases of viable pregnancies.
Two forms of PGE2  are available commercially. The first is formulated as gel and is placed inside the cervix but not above the internal os. The application  (3g gel / 0.5 mg dinoprostone) can be repeated in 6 hrs, not to exceed 3 doses in 24 hrs.

 The second form is 10 mg of dinoprostone embedded in a mesh and is placed in the posterior fornix of vagina, this allows for control release of dinoprostone over 12 hrs, after which it is removed.

Prostaglandin E1 analog (misoprostol)  available in tablet form for induction of labor was described recently in a series of articles. This is a synthetic prostaglandin, which is marketed as an antinuclear agent under the trade name cytotec.  25 or 50 micro g   placed in the posterior fornix, has been shown in several studies to be quite effective in inducing cervical ripening and initiation of  labor. The application of medication can be repeated every 4 -6 hrs up to 5 doses.
                                  
The major risk of above prostaglandin preparation is uterine poly systoly, hyper-stimulation, meconium stained liquor   and fetal distress. The women and fetus must be monitored for contractions, fetal wellbeing and changes in Bishop score.
                     Finally, it was demonstrated that the combination of oxytocin induction preceded by dinoprostone insert is safe, and this significantly shortens induction to delivery time.
Recently explored methods:
Anti progesterone   eg.  Mifepristone
Ostrogens
Relaxin
Nitric oxide

C. Surgical methods :
Membrane sweeping
Amniotomy
                                                                                                                                  
Natural and complementary medicine methods:
Homeopathy
Breast stimulation
As a general principle the simplest inductions are those performed when the cervix is ripe and probably precede the spontaneous onset of  labor by a few hours to a day or two. And for the most difficult inductions, when the cervix is very unripe, a combination of a pharmacological agents, possibly involving more than one drug along with mechanical stimulus may be needed.



Sunday 25 March 2012

Labor induction: indications, contra indications, methods predicting success of labor induction, complications of labor induction.

Indications of labor induction :
The indications for labor induction can be subdivided into maternal , fetal or social or a combination of these.
A. Maternal indications:
1. Obstetrical indications:
 Post dated or post term pregnancy        
 Ante partum hemorrhage
 Red-cell alloimmunisation
 Previous unexplained still birth at term
 Intrauterine fetal death
 Oligohydromnios
Congenital fetal malformations
 Premature rupture of membranes

2. Medical indications:
 Chronic nephritis superimposed acute nephritis and failure
 Hypertension
 Diabetes

B. Fetal indications:
 Placental insuffiency
 IUGR
 Postdatism
Rh isoimmunisation
Previous unexplained still births
Deteriorating antenatal tests for fetal wellbeing.
Specific definitions and the relative importance of the various indications for labor induction vary between obstetrician, obstetric unit and country.
Post dated pregnancy is probably the commonest indication in many units but definitions may include any gestation beyond 40, 41 or 42 completed weeks of gestation.
Some obstetricians consider that cervical state should determine the timing of delivery,  particularly when post–dates pregnancy is the indication for induction. It must be remembered however , that there is often a poor relationship between cervical favorability and gestational age.
Hypertensive states constitute the second most common primary indication for labor induction in many obstetric units, again generally because of anticipated fetal or maternal problems rather than because of evidence of deteriorating maternal or fetal health.
The other indications are varied, some universally accepted, such as recent or current ante partum hemorrhage, diabetes mellitus, red cell alloimmunisation, demonstrable placental failure and previous unexplained still birth at term and others with little logic, such as fetal breech presentation and suspected cephalo- pelvic disproportion. In many countries there is now a reluctance to encourage labor when there is a fetal breech presentation.
Labor induction performed at maternal request or convenience at term is generally frowned upon. However the reluctance to accommodate such requests, believing it is not in the best interests of mother or fetus, is at variance with the willingness to allow patients to opt  for delivery by elective cesarean section, usually performed before full term, particularly in cases such as breech presentation or previous delivery by caesarean section.

                                                                                                                             
Contraindications to labor induction:
A. Absolute:
1. Disproportion that is more than borderline.
2. Where the lie is other than longitudinal, for obvious reasons.    
3. In cases of previous caesarean section for contracted pelvis or who have failed in a previous trail of labor for disproportion.
4. Where a tumor occupies the pelvis.
5. When vaginal delivery is contraindicated in conditions like major degree placentaprevia, vasaprevia, cord presentation and prolapse, invasive carcinoma of cervix and infections like active herpes genitalis.
6. Previous classical caesarean section.
7. Regular contractions.
8. Unification surgery for uterine didelphis.

B. Relative contraindications:
1. Maternal heart disease
2. Breech presentation
3. Multiple pregnancy
4. Poor biophysical profile and Doppler studies
5. Grand multipara
6. Previous myomectomy
7. A history of prior difficult or traumatic delivery   
8. Maternal fever

Predicting the success of labor induction:
Cervical condition exerts a significant influence upon induced labor outcome and its consequences. The decision about how to induce labor must take account of the favorability of cervix.
To assist an obstetrician in deciding which way to induce labor a cervical scoring system is often used. More than 12 different pelvic or cervical scoring schemes have been described during the past 70 yrs, but only four to five are in vogue.
The semi-quantitative clinical scoring system described by Bishop in 1964 is the one most widely employed.  He originally described it with basic requirements of multiparity, gestational age >36 weeks, vertex presentation, normal previous and present obstetric history, advance knowledge and permission of the patient.  The score uses the cervical dilatation, effacement, consistency, position, and the station of the presenting part.
Because it is simple and has the most predictive value , it was used in many studies and doctoral dissertations   to assess the predictability of induction and to determine the agent to be used.       
                                                                                                                                                                   Bishop score :
parameter
         0
          1
        2
         3
position
  posterior
intermediate
   anterior
          -
consistency
  firm
intermediate
   soft
          -
effacement
  0 to 30%
40 to 50%
  60 to 70%
    ≥80%
dilatation
   <1cm
1 to 2 cms
2 to 4cms
    > 4 cms
Foetalstation
     - 3
      - 2
    - 1, 0
   + 1 to + 2

Bishop score is somewhat subjective, but a score of less than 5 suggests further ripening is needed, while a score of 9 or greater suggests that ripening is completed.


The modified Bishop score by Calder:
Calder modified the original Bishop score in 1974, which is known as the modified Bishop score and is currently used by most obstetric units.. He replaced the ‘effacement of cervix’ denoted as percentage in the original score with length of cervix in centimeters, which is having more reproducibility and reliability than original Bishop score.

Modified bishop score:
parameter                  
         0
          1
        2
         3
position
  posterior
intermediate
   anterior
          -
consistency
  firm
intermediate
   soft
          -
Length of cx
  >3cms
>2cms
  >1cm
    > 0cm
dilatation
   <1cm
1 to 2 cms
2 to 4cms
    > 4 cms
Foetalstation
     - 3
      - 2
    - 1, 0
   + 1 to + 2

Maximum possible score would be 12, at which point , of course delivery would be just about imminent.
As the evaluation of score rises, the latent phase becomes shorter. This is an important matter because the latent phase contributes significantly to a   prolonged induction to delivery interval. Of all the parameters of the score , the degree of cervical dilatation seems to be the most important .However once the active phase of labor supervenes it does not necessarily differ significantly in length or other characteristics from spontaneous labor.
Other cervical scoring systems that were described in literature were as follows :

 Calkins  in 1930 :  
First published description of a method to quantify cervical factors that could predict the course of labour.
Multiparity was taken as predictive of successful labor.
Dichotomous scoring system
effacement :  present / absent
engagement:  above/ below spines
consistency:  soft -like lips=2/ firm like nose=3
Labor intensity:   good =  one contraction/3min, 
                                fair=one contraction/5min,
                                 poor=one contraction/>5min
If completely favourable, in 95-100% of women had 1st stag of less than 6 hrs. Assessment was made via rectal examination.

 Cocks in 1955 :
 having 5 categories of cervix                                                                           
1.      Soft, effaced ,1cm dilated
2.      Soft,uneffaced,1cm dilated
3.      Firm,somewhat effaced,closed os
4.      Firm, uneffaced,closed os
5.      Anomalous cervix

Modified Bishop score by Friedman  in 1967:
Multiply Bishop factor
Factor 
  Simple weighting             
       complete weighting               
Dilatation
     2
   4
Effacement
     1
    2
Station     
    1
     2
Consistency
      1
     2
Position
     0
     1
Range of scores
    0-14
0-30

Ultrasound assessment of the cervix has been investigated as a way of predicting the likely outcome of induced labour as an alternative to clinical digital examination.
Before proceeding to trans vaginal ultrasound the woman was asked to empty the bladder.
The endo vaginal probe is first covered with a sterile condom into which has been placed sterile gel. The condom prevents vaginal secretions from contacting the probe. Sterile gel is also applied to the outside of the condom.
As described by Anderson  with the patient in lithotomic position, 5 Mhz vaginal probe was introduced into the vagina and the length and width of the cervix was measured with the probe placed in the anterior fornix of the vagina. The appropriate sagital view of the cervix was obtained by simultaneous imaging of external and internal os.
External os was identified by its triangular echo density and internal os by its v shape appearance. The cervical canal was seen as a triangular line connecting these two points. The distance between the external and internal os taken as cervical length. The width was measured at the level of internal os. All these measurements were repeated thrice and the average of the readings was taken for statistical analysis.
To reduce inter observer variability and improve reproducibility of cervical measurements using trans vaginal ultrasonography , the following criteria were adopted.
The internal os is visualized as a flat dimple or an isosceles triangle
The whole length of cervix is visualized
The external os appears symmetric
The distance from the surface of the posterior lip to the cervical canal is equal to the distance from the surface of the anterior lip to the cervical canal.
Transducer pressure on the cervix is kept to minimum.
The widest viewing angle of the available ultrasound field should be used.
Ultrasonographic cervical measurement has been known as a reproducible , objective and quantitative method and can be performed easily.
Cervical length of > 2.8 cm was shown to have a better sensitivity in deciding the need for cervical ripening.
If there is no much change in cervical length 6 hrs after induction it can predict the prolongation of induction.
 Parity is another factor which may predict the success of labor induction. parity  is an independent predictor of the total duration of labor as well as the duration of induction.
For the same cervical length, the induction to delivery interval in multigravidae was 37 % lower than nulligravidae. The incidence of successful vaginal delivery within 24 hrs of induction was about 30% higher than in nulligravidae.
Other factors in predicting the success of labor:
Fetal fibronectin (FFN) concentration in cervical transudate represent a laboratory approach and have been shown to correlate with induced labor outcome with concentrations greater than 50 microgs/ml associated with a favorable cervix and reduced intrapartum morbidity.
Electrical impedance measurements across the surface of the cervix using a 8 mm tetrapolar pencil probe have been used to investigate correlations with clinical examination to assess cervical favorability.
Serum nitrite/ nitrate levels have also been assayed in nulliparae  undergoing prostaglandin induction of labor and using multiple regression analyses significantly lower levels of each were found in women who delivering over a longer period.

Labour induction is not without its risks for the mother and particularly for the fetus
Complications :
 1. Inadvertent delivery of a preterm baby has largely been eliminated by the widespread use of ultrasound assessment of gestation.
2. Unforeseen cephalo pelvic disproportion
3. Sepsis, risk is negligible, if amniotic sac is intact. Risk increases if  membranes have been ruptured.
4. Partial placental detachment in cases of surgical induction if placenta sited low in uterus. And bloody tap in cases of vasa preavia.
5. Accidental hemorrhage, abruptioplacenta in cases of polyhydromnios following ARM due to sudden release of enormous quantities of liquor.
6.  Fetal pneumonia due to prolonged retention of the fetus in utero with ruptured membranes, particularly in association with prolonged labor.
7. Cord prolapse, when amniotomy done and fails to engage or in malpresentation
8. Amniotic fluid embolism
9. Prolonged oxytocin infusion can lead to fluid and electrolyte imbalance to mother and in baby neonatal jaundice can occur due to osmotic fragility of erythrocytes.
10. Uterine hyper stimulation                                                                                                                   
11. Failed attempts at induction leading to caesarean section probably because of mistaken belief that any attempt at inducing labor should not persist beyond a few hours.
12. Any possible long term consequences for the babies
The issue of cost benefit equations is now an important factor to be taken into account, when discussing alternate options. Thus not only must the method of labor induction be safe and acceptable for the mother and fetus, it must also be cost effective.
The search for an ideal method of induction that modulates the unfavorable cervix to favorable cervix without stimulating uterine contractions and improves the ultimate outcome of labor, almost eliminates the risk to fetus still has to be found.