Subarachnoid Hemorrhage And Pregnancy (PART 4)

Physiologic changes of pregnancy:         Anesthetic management (1)

-------------------------------------           --------------------------------------------

1.Increase in cardiac output(C0)     Careful monitoring of intravascular

                                                      volume.  

2.Increase in uterine size.               Aortocaval compression in supine  

                                                      position;maintain left lateral uterine

                                                      displacement perioperatively.

3.Reduced FRC ,increased 02               Preoxygenation higher Fi02.

   consumption.

4.Increase in minute ventilation           Monitor changes in PaC02 closely.

    decrease in PaC02,leftshift of           prevent hyperventilation,avoid dec-

    oxyhemoglobin dissociation               rease in C0,UBF,02 supply to the

    curve.                                                    fetus.

5.Decrease in gastric emptying             Aspiration prophylactis ,rapid sequ-

    gastro oesophageal reflux.                ence induction.

6.Maternal hyperventilation ,re-            Monitor EtC02,mantain adequate

    duced PaC02,cerebralvaso-                CPP.

    spasm,cerebral ischemia/in-    

    farction.

7.Reduced MAC for inhalation                 Avoid overdose and cardiovascular 

    anesthetics.                                        depression.

8.Decreased epidural and sub-                Decrease local anesthetics require-

   arachnoid space.                                 ment for regional anesthesia.

9.UBF is not autoregulated and                Avoid hypotension and consequent

   is proportional to mean perfu-              decrease in UBF with reduced 02

   sion pressure.                                       to the fetus.

10.Decrease in serum choline es-             Monitor neuromuscular blockade

    terase.                                                 after succinylcholine use.

Adverse uteroplacental drugs effects  (2)           

          Drugs                                                adverse effects

       Phenytoin                                             minimal

       Thiopental                                            neonatal depression(>8mg/kg in

                                                                   humans),worsening of preexisting

                                                                   fetal distress caused by maternal 

                                                                   hemodynamic effects.

       Lidocaine                                             Uterine hypertonus and vasocons-

                                                                   triction with fetal distress (toxic

                                                                   dose in sheep);worsening of pre-

                                                                   existing fetal distress.

       Mannitol                                               Oligohydromnios with fetal hyper-

                                                                   osmolarity,hypernatremia,dehyd-

                                                                   ration,cyanosis,bradycardia(12,5

                                                                   g/kg in rabbits);fetal hyperosmo-

                                                                   larity in humans 1 hr after 200g

                                                                   intravenous.

      Furesemide                                           Possible dilatation of ductus arte-

                                                                  riosus,electrolyte abnormalities.

      Nitropruside                                         Decreased uterine vascular resis-

                                                                  tance;electrolyte abnormalities,

                                                                  lethal fetal cyanide levels with on-

                                                                  set of maternal tachyphylaxism

                                                                  sheep.

     Nitroglycerine                                       Decreased uterine vascular resis-

                                                                  tance.

     Hydralazine                                           Decreased uterine vascular resis-

                                                                  tance.

     Propranolol                                           Decreased umbilical blood flow in

                                                                  sheep,premature labor,worsen-

                                                                  ing of preexisting fetal distress

                                                                  neonatal acidosis,bradycardia,

                                                                  hypoglycaemia,apnea,diminished

                                                                  response to hypoxia and acidosis

Management of subarachnoid hemorrhage(SAH) in pregnancy:(1)

         Lesion                             Pregnancy                       Management

1.Incidental aneurysm          before 26 weeks         Risk of SAH regardless

                                                                             of the mode of delivery

                                                                             surgical treatment of a

                                                                             neurysm reduces risk

                                                                             for both mother and 

                                                                             baby.

2.Incidental aneurysm          34 - 36 weeks             C-Section,aneurysm 

                                                                             clipping under same a-

                                                                             nesthetic.The take ho-

                                                                             me rate is same as full

                                                                             term infants.

3.Corrected aneurysm           Any stage                  Negligible risk of bleed

                                                                             ing needs normal obs-

                                                                             tetric management.

4.Ruptured aneurysm            Before 26 weeks         Aneurysm surgery and

                                                                               vaginal delivery at term

                                                                               according to obstetric

                                                                              indication.

 5.Ruptured aneurysm            Beyond 26 weeks        Moribund patient-->

                                                                               C-section to save the

                                                                               infant.

6.Ruptured aneurysm             Beyond 34 weeks        Neuroresuscitation to

   unstable patient                                                    CT/angiogram --->

                                                                               C-section and aneu-

                                                                                rysm surgery;maintain

                                                                                uterine tone during

                                                                                lengthy surgery.

7.Ruptured aneurysm             In utero death              Aneurysm surgery and

                                                                                then vaginal delivery.

8.Unruptured AVM                Term pregnancy           No C-section when no

                                                                               adverse circumtance 

                                                                               prevail.

9.Ruptured AVM                  Before 26 weeks          Conservative manage-

                                                                              ment (risk of rebleed

                                                                                            less than aneurysm).

10.Ruptured AVM un-          Term pregnancy            Neuroresuscitation ->

      stable.                                                              CT/angiogram-->C-

                                                                              section --> surgery

                                                                              and excision of AVM.

 PERIOPERATIVE MANAGEMENT:(1,2)

Management of SAH during pregnancy is similar to that in non pregnant patients and depends on the neurologic condition of the mother and the stage of pregnancy.
Craniotomy for aneurysm is perfomed under neurosurgical criteria while C-section is done for obstetrics indication.

Perioperative management depends on the neurologic evaluation,viability of the fetus,effect of anesthetic technique and drugs on intracranial pressure,uteroplacen 
tal transfer of the drugs and their teratogenicity and effect on uterine relaxation.

Before fetal viability (<32 weeks) and patients with good SAH grades surgical clipping should be performed as soon as possible to prevent rebleeding. About 80% of these patients aneurysm ruptures occur before 36 weeks of pregnancy. 
In these patients aneurysm clipping followed by delivery 
at fullterm generally in a satisfactory outcome for both 
the mother and infant.

During craniotomy continuous fetal heart rate monitoring should be used with an obstetric team available.

If fetal distress develop,caesarean delivery may be considered.

In general the timing and method of operative corrections should be decided on neurosurgical grounds without regard to the status of pregnancy.

A C-section is indicated when the mother moribund after SAH to preserve a fetus deemed mature enough for delivery.

Oxytocix drugs have been used to decrease uterine atony and bleeding after delivery without causing detererious neurologic effects although they have not been studied extensively in this setting.
The most common hemodynamic alteration with oxytocin is hypotension whereas hypertension is associated with methyergonovine maleate (methergine) and proataglandins.
The basic requisite of intraoperative management are the maintenance of adequate cerebral perfusion and favourable operative field ,monitoring fetal homeostasis and uterine relaxation,preventing fetal depression.

Patients who have AVMs are morelikely to suffer intracra
nial hemorrhage during labor than are those who have aneurysm. In an AVM is amenable to surgical treatment there is no need to delay this treatment because of pregnancy although a case of successful  management of pregnancy to term followed by delivery without incident has been reported.

The basic management consist of:(1)

1. Smooth induction:

   Avoiding rebleeding from rise in blood pressure and cereb
   ral ischemia from hypotension and hypovolemia.

2.Controlled laryngoscopy:

   Avoid both rise in BP and rise in ICP.

3. Prevent aspiration of gastric content:

    As with any other C-section it is imperative to prevent 
    regurgitation and aspiration of gastric contents. 
    Metoclopropamide,ranithidin,anticholinernics,and 
    famotidine have been used preoperatively to reduce both 
    gastric volume and acidity in pregnant women.
    Oral sodium citrate given immediately before induction 
    has also been shown to increase the pH of gastric 
    contents.

    A rapid sequence induction with thiopental,succinylcho
    line or rocuronium intravenous lidocaine,fentanyl and 
    propranolol or sodium nitropruside (SNP) and cricoid
    pressure have been used in good results.

4.Avoid fetal depression :

   Discontinue long acting drugs such as diazepam,and pheno
   barbital and use drugs that do not depress the infant.

5.Prevent uterine relaxation:

   Avoidance of inhalational drugs like halothane is impor
   tant to prevent uterine relaxation with consequent 
   hemorrhage in the postpartum period.Isoflurane to 1% has 
   been used in such situations with good outcome,as it has 
   been shown to reduce awareness and blood loss during C-
   section.

 6.Control of blood pressure(BP):

    Systemic hypertension increases the CBF,CBV,and ICP 
    and may induce rebleeding.
    Controlled hypotension or temporary proximal occlusion 
    meets surgical requirements.
    The use of SNP in obstetrics is still controversial owing to 
    the potential toxicity from cyanide and fetal hypoxia 
    from the hypotension induced reduction in placental 
    perfusion. With judicious use of SNP however,fetal 
    compromise may be kept atbay.

7.Control ICP :

   Mannitol an osmotic diuretic,may have adverse effects on 
   the fetus including dehydration and bradycardia.

8.Management of ruptured aneurysm intraoperatively:

  Aggressive restoration of acute blood loss, hypotension 
  (anesthesia, SNP or ipsilateral carotid compression) 
  avoidance of excessive ventilation and a relaxed brain.

9.Maintain uetrine tone:

   Oxytocin has been safely infused after combined neuro
   resuscitation and C-section and continued throughout 
   the subsequent angiogram and six hours craniotomy for 
   clipping of saccular aneurysm of the middle cerebral 
   artery with hyppocampal herniation and evecuation of 
   a large hematoma in the left tempoparietal region.
   The hypertension caused by methyl ergonovine maleate 
   and prostaglandin for treatment of uterine atony maybe

   detrimental the aneurysm is secured.

10.Ventilation during anesthesia has to be carefully 
     matched to the needs of patients with due consideration 
     for the unborn baby.Hyperventilation may aggrevate 
     preexisting cerebralvasospasm and will also cause 
     uteroplacental insufficiency due to vasoconstriction with 
     attendant felal hypoxia and acidosis.

11.Continous BP monitoring :

     This is essential when hypotensive drugs are employed.       
     Monitoring arterial blood gases(ABG) in the perioperative 
     period will confirm adequate oxygenation,effective CO2 
     elemination,and metabolic homeostasis may indicate 
     the early occurence of cyanid toxicity.

12.Urinary output:

     Good urine output is an indication of adequacy of intra
     vascular volume and organ perfusion and the effective
     ness of diuresis.

13.Fluids,electrolytes,glucose and osmolarity must be moni
     tored closely to detect and treat contracted intravascu
     lar volume and disordered sodium and potassium 
     balance.

Summary :

Because these aneurysms present primarily in the third trimester of pregnancy,the anesthesiologist must face the possible complications associated with pregnancy and the special consideration for aneurysm clipping.The anesthetic management also depends on the gestational age,and obstetric plan,that is whether delivery of the fetus will precede the neurosurgical procedure or whether the aneurysmal clipping will be done followed by normal maturations of the fetus with subsequent delivery at term.

The goal of anesthesia during pregnancy are to ensure the recovery of the mother and the normal continuation of pregnancy without damage to the fetus. The anesthetic management should be the same as for the non pregnant aneurysm patient except that one is taking care of two patients. Pregnant patients have special needs because of the physiologic changes that occur during pregnancy including consideration for decrease in MAC, an increased potential for aspiration and having difficult airway,special positioning,the influence of anesthetic induced depression on maternal BP and the risk of inducing premature labor.

Special needs with respect to the fetus are,adequate fetal maternal oxygen exchange which depends on adequate maternal BP,potential for teratogenic effects secondary to drugs and perioperative monitoring of the fetus.

One should anesthetize the patient to an adequate depth of anesthesia with the aim of preventing aneurysmal rupture during induction as well as during maintenance and accept the price of neonatal depression.

Equipment and personal for for neonatal resuscitation should be at hand when delivery occurs.

REFERENCES :

1.Newfield Philippa,Hamid AK,Rukayya,Lans M.Arthur:
   Subaracnoid hemorrhage and Pregnancy:Albin S Maurice:   
   Textbook of Neuroanesthesia with Neurosurgical and    
   Neuroscience perspectives;The MCGraw Hill Companies 
   Newyork,St.Louis,San Franscisco 1997.pp 885-91.

2 Lam M Arthur:Cerebral aneutysm:Anesthetic considera
   tion:Subarachnoid and Pregnancy;Cottrell E James.Smith 
   S David;Anesathesia and Neurosurgery,4th edit,Mosby 
   Inc,St Louis,London,Philadelphia,Sydney,Toronto,2001.
   pp 385-88.

3.Stone J.D,Bogdonoff L David: Anesthesia for intracranial 
   surgery;Stone J.D,Sperry J Richard;The Neuroanesthesia 
   Handbook, Mosby Company,st.louis,Baltimore,Boston ,
   1996.pp 352-3.

4.Morgan Barbara:The physiology of Pregnancy and 
   Anesthesia:Morgan Barbara; Foundations of obstetric 
   Anesthesia,Farrand Press,London,1987.pp 126-33

5.Barrier G,Surean C:Effects of Anesthesia and Analgesic 
   drugs or Labor Fetus and Neonate;Rosen Michael;Clinics 
   in Obstetric and Gynaecology,WB Saunders Company 
   Ltd,London,Toronto,Philadelphia,1982,pp.351-61.

6.Snow C Johnson: Anesthesia and Analgesia in Obstetric 
   and Gynaecology;Manual of Anesthesia,Asian edition,
   Little Brown and Company Boston,Tokyo ,1978,pp.427-29.

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Subarachnoid Hemorrhage And Pregnancy (PART 2)

CARDIOVASCULAR CHANGES :(2,4)

The pregnancy induced changes in maternal cardiovascu
lar system begin in early pregnancy are extensive by the end of the first trimester increasing until term,diminish after delivery until 6 weeks postpartum the mother has returned to her pre pregnant cardiovascular state.

The changes are :

1.Increase in cardiac output(CO).

2.reduced peripheral resistance.

3.increased blood volume.

Ad.1 The CO increases by 40% by the end of the first 
        trimester is achieved by 30% in stroke volume and 
        smaller increase in heart rate(HR).

Ad.2. Peripheral resistance falls early in pregnancy and 
         is reflected by a lowering of BP in the second 
         trimesters.

Ad.3. Circulating blood volume increases in the first 
         trimester continues to increase until term it is 
         1250 ml above non pregnant levels is a result of  
         the expansion of the plasma volume by 45% and 
         smaller increase the redcell by 20%. 
         This cause a haemodilution with hemoglobin 
         concentration around 11g/100 ml and hematocriet
         (Ht)of 33% of normal. The blood volume return to 
          normal about 14 days post partum.                 

          Plasma protein concentration is reduced giving 
          lower osmotic pressure.The absolute quantity of 
          plasma albumin is decreased. 
         The globulin fraction is increased.

The purpose of the increased  plasma volume and CO is three fold :
1.An increase uterine blood flow(UBF) which at term is 
   600-800 ml/min,the placental flow wholly dependent on 
   maternal BP.

2.An increase in renal blood flow(RBF) by 400-500ml/min 
   by the end of the first trimester,which required to 
   eleminate extra waste products produced by the very 
   rapid fetal growth.

3.An increase in skin blood flow because peripheral 
   vasodilatation is necessary to eleminate heat produced 
   by rapid growing fetus.

Anesthetic consideration :

The mother has her cardiac stress increased to the extent that output in the first trimeter is half the maximum of 12 litres which she can achieve with vigorous exercise,she
has therefore a lot less cardiac reserve.This is especially important in those with cardiac disease,the older mother 
the obese and those with multiple pregnancies.

Drugs with negative inotropic and chronotropic effects must be used with care and titrated where possible.
Hypotensive side effect must be minimized as the placen
tal flow is pressure dependent.
Drugs withknown cardiovascular effects like ergometrine should where possible be avoided as they increase cardiac work.

The supine hypotensive syndrome can occur from the 16th week of pregnancy or in multiple pregnancy from the 12th week;cause a decrease venour return to the right heart and a reduction in CO. While aortic compression reduced UBF,utero placental perfusion and renal blood flow (RBF).

UBF is not autoregulated,it varies directly with systemic maternalBP and is inversely proportional to uterine vascular resistance. 
Maternal SBP < 100 mmHg in the previously normotensive  or a 20% drop in the hypertensive for more than 10 minutes can result in fetal asphyxia, bradycardia and acidosis.

Awareness of this problem should ensure that all pregnant woman from the second trimester onwards must be tilted laterally 20 degrees during surgery or while being transported on a trolley Maternal BP and fetal HR should be continuously monitored.                        

RESPIRATORY CHANGES:(1,4)

These changes are established by the end of the first trimester they include :

1.Increased tidal volume

2.Fall in PaCO2

3.Increased O2 consumption

Minute ventilation rises 7,5-10,5 litres in the late pregnancy. Functional residul capacity(FRC) is decreased.

PaCO2 of 30 mmHg is present from early in pregnancy until delivery.This reduction of PaCO2 which causes dyspnoe and giddiness in early pregnancy may be progesterone effect.

Oxygen consumption increases from an avarage of 189 ml/min in the non to 234ml/min in late pregnancy
(Fishburne 1979).


Anesthetic consideration :

It is essential to prevent wide swings in maternal PCO2 for fetal wellbeing.Premedicant and post operative drugs that depress ventilation must be used with caution as the fefus shows greater sensitivity to CO2 than adult.

Excessive hypocarbia with hyperventilation must be avoided may reduce placental perfusion by vasocons
triction in the same way as maternal cerebral perfusion is decreased, PaCO2 should therefore be maintained at about 30 mmHg.

Also it decreases maternal cardiac output and raised pH thus reducing the oxygen releasing capacity of maternal Hb therefore reducing fetal oxygen supply.

Maintaining the slightly raised PO2 must be borne in mind.

Hypoxia during intubation as well as hypotenion which increases ventilation perfusion abnormalities must be avoided. Decreased FRC allows a more rapid rise in partial pressures of inhalational agents and a more rapid uptake of volatile agents.

The nasal mucous membrane is congested throughout pregnancy possibly to humidify the increased tidal volume. Excessive bleeding can be caused when the passage nasal tubes to the stomach or trachea are attempted.

Pharmacokinetic changes:(4)

During pregnancy the absorbtion,distribution,metabolism and excretions of drugs are altered largely due to the increased plasma the fall in absolute quantity of plasma albumin,the possible increase in liver metabolism and greatly increased glomerular filtration rate(GFR).

This result in :

1.a lower plasma concentration because because of the 
   large dilutional volume.

2.less albumin is available to bind drug to the plasma 
   protein depot and thus with repeated doses the free 
   drug concentration rises rapidly once the albumin stores 
   are taken up.

3.prolonged half life of drugs because of longer time taken 
   to clear greater volume of plasma.

4.increased liver metabolism may occur and possibly some 
   alteration in the metabolism.

5.better elimination of metabolized drugs because of    
   increased GFR.

6.pseudocholine esterase activity is decreased by 30% but 
   this seems not to prolong the activity of succinylcholine.

Changes in conduction anesthesia(4)

By the end of first trimester some degree of obstruction to venous return even when the mother is not supine;
hence
1.Dilatation of venous collateral in paravertebral venous 
   plexus which result in a smaller epidural space.
   There is an increased risk of epidural venous puncture 
   with greater hazards of intravenous local anesthetic 
   solution resulting from a bolus of drug going via the 
   azygos vein to the heart.

2.Increased sympathetic tone of the lower limbs is 
   common in pregnancy.Usually the pregnant woman 
   complains of cold feet and has hot vasodilated upper 
   limbs.When sympathetic block is initiated profound 
   hypotension occurs.

3.Local anesthetic drugs like buvipacaine are strongly 
   protein bound to plasma glycoprotein which rises in 
   pregnancy in maternal leaving less free drugs available 
   to cause toxic effects.

To be continued

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Subarachnoid Hemorrhage And Pregnancy (PART 1)

INCIDENCE(1,2)
Intracranial hemorrhage(ICH) cause catastrophic complica
tions during pregnancy and is considered an important non
obstetric of maternal morbidity and mortality.
Generally SAH resuls from cerebral aneurysmal rupture or bleeding from arteriomalformation(AVM).
SAH has been reported to be the third leading the cause of non obstetric maternal morbidity.
About 50% of the patients who present with SAH during pregnancy have a ruptured AVM,as compared with 10%
in the non pregnant group.
In non pregnant patient,SAH is more commonly caused by the rupture of an intracerebral aneurysm than by AVM.
In pregnancy these occur with equal frequency.
SAH from an aneurysm during pregnancy usually occurs in multiparous women between 25 to35 years of age,where
as bleeding from AVM occurs in patients between 18 to 25 years of age and parity is not a factor.
The risk of rebleeding after a hemorrhage during the same pregnancy is 27%.
AVMs tend to rupture at any stage of pregnancy but most commonly between 20 weeks of gestationn and 6 weeks
postpartum.


The relationship of aneurysmal hemorrhage to stage of pregnancy has been reported as follows :
First trimester 6%,second trimester 31%,third trimester 55% and postpartum 86%.
The tendency to rupture may be related to hemodynamic,
hormonal and coagulation changes that occur during
the third trimester including the increase of blood volume.


PATHOPHYSIOLOGIC  CEREBROVASULAR ACCIDENT(CVA) 
during pregnancy :
Arterial aneurysm are the most common cause of non traumatic SAH and the spontaneous of an aneurysm has been temporally related to the use of cocaine,booth 
cocaine and alcohol abuse have been linked to intracereb
ral hemorrhage. Studies indicate that 2 to 9% of pregnant women are heavy drinkers and about 8 to 17% of pregnant women abuse cocaine.
Robinson reported a ruptured aneurysm in ascociation with severe preeclampsy and Amios reported a relation
ship between pregnancy associated hypertension and ruptured cerebral aneurysm.


An aggressive treatment regiment of antihypertensive is indicated when blood pressure rise above 160/110 mmHg as chronic hypertension are at increased risk of ruptures of intracranial aneurysm.
The onset of aneurysmal bleeding has also occured during an elective caesarean section. Vasospasm is frequent complication of SAH.
Vascular compression and/or vasospasm may produce ischemic and infarction in 5 to 7 days after the initial SAH and cause delayed neurologic deficit.


NEUROLOGIC ASSESSMENT :
The clinical feature of CVA in pregnant women are not any different than in the general population.
The initial investigation needs to be prompt and thorough in order to differentiate CVA from other disorders pre
senting with severe headaches associated with neurologic signs. 
The differential diagnosis includes pre eclampsy,chronic hypertensi,seizure disorder,intracranial tumors,abscess and other space ocupying lesions,saggital sinus thrombo
sis,meningitis,encephalitis,demyelinating disease,cerebral arterial occlussive disease and moya moya disease all of which may worsen during pregnancy and are associated with intracerebral hemorrhage.
Pituitary apoplexy,abuse of cocaine and alcohol,dissemi
nated intravascular coagulation,ectopic endometriosis,
subacute bacterial endocarditis,and choriocarcinoma
may also produce symptom complexes that are indis
tinguisable from ICH and should be included in the differential diagnosis.
The clinical examination after SAH may reveal fever,
nuchal rigidity,and high blood pressure(BP).
There may be focal neurologic deficits caused by hemato
ma hydrocephalus,ischemia and recurrent bleeding,inclu 
ding aphasia,hemiparesis and hemianopsia.
Seizures may be the presenting symptom in some cases of SAH from AVM,
Hypothalamus irritation from SAH may cause a variety of systemic abnormalities.
Contraction of intravascular volume or secretion of atrial natriuretic hormone lead to electrolyte imbalances.
SAH may also mimic eclampsy especially as severe hypertension and protenuria may develop after SAH.


PHYSIOLOGIC CHANGES DURING PREGNANCY :
Pregnancy has a stimulating effect on aneurysmal growth especially during the third trimester.
There is an increased incidence of rupture during this period. The hemodynamic stress of increased blood volume ,heart rate,cardiac output and stroke volume, 
pregnancy induced hypertension in the third trimester and hormonal alteration in pregnancy which cause changes in the wall of the arteries and vein may all contribute to the increased risk of of intracerebral lesions during pregnancy
The hemodynamic alteration of pregnancy do not,howe
ver,alter CBF or the CMR for O2. As such any factore that reduce perfusion pressure or increasevascular resistance will adversely affect placental perfusion with concequent ill effect on the fetus.


Maternal hypotension should be avoided during operation.
Pregnancy itself causes a progressive increase in minute ventilation and decrease in functional residual capacity (FRC).Changes in minute ventilation,the mechanical 
effect of possitive pressure ventilation and decrease in the PaCO2 may reduce placental blood flow to the fetus.
Respiratory alkalosis shift the oxygen Hb dissociation curve to the left and increases the affinity of maternal Hb for oxygen thereby fetal oxygen supply.
Hypocapnia also reduces uterine blood flow with 
attendant fetal hypoxia and acidosis.
Maternal PaCO2 should therefore be maintained at about 30 mmHg.


to be continued

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