NEONATAL SURGICALEMERGENCIES & ANAESTHETIC MANAGEMENT Dr.Narasimha Reddy, M.D.,DA Professor & H.O.D, Dept. of Anaesthesiology, Kurnool Medical College , Kurnool
PART IPHYSIOLOGICALCONSIDERATIONS & ANAESTHETIC IMPLICATIONS
• Neonatal surgical emergencies are common in developing countries. – High birth rate – Consanguinity – Infections during pregnancy – Multiple pregnancies – malnutrition
Some terminologies:• Fetus: intrauterine period• Newborn: upto 12 hrs after birth• Neonate: upto 30 days after birth• Infant: first 12 months of age.• Gestational age:time from conception to birth• Post-natal age:time from birth to present time• Post-conceptual age:from conception to present age (G.A+post natal age)
CNS• Gets 1/3rd of CO• Autoregulation present, but not effective• Myelination incomplete, senses are active• Can feel pain , can smell & hear• Blood – brain barrier – Immature,hydrophilic & lipophilic cross the barrier – Autonomic regulation good – Parasympathetic domination – Less number of receptors & variant protein binding
CNS…..• InterVentricular hemorrhage: – Surgical stimulation, – inadequate analgesia, – Airway instrumentation, – Excessive transfusion, prematures are more prone, stressed neonate lacks autoregulation, Fluctuations in CPP
CVS• Heart contractile mass 30%,• Ventricles less compliant,• CO 350- 400ml/kg/mt.• CO depends on heart rate & SV• O2 consumption is 7 ml/kg/mt.• Bradycardia is due to hypoxia, low CO, vagal stimulation in anesthesia
AUTONOMIC NERVOUS SYSTEM• Baroreceptors are immature & sensitive to anesthetics• Sympathectomy due to spinal or epidural- no fall in B.P.(as sympathetic system is immature).• Fall of BP & HR due to sympathetic blockade is offset by inhibition or withdrawal of cardiac vagal activity.
RESPIRATORY SYSTEM• Neonate has a large head, small weak neck,obligate nose breather, large tongue, U-shaped epiglottis, funnel shaped larynx, Subglottic portion is the narrowest larynx is anterior & cephalad cricoid is complete ring, tracheal length is 2-5 cms.
• Respiratory centre is immature & sensitive to depressant drugs• More in prematures, apnoeic episodes are common• Lung volumes – Tidal volume is small, 6 ml/kg 15 ml/kg – O2 consumption is 7-9 ml/kg – Resp.rate & alveolar vent. 2-3 times adult. – FRC/VA ratio in neonates is 0.23, – Changes in FiO2 causes rapid changes in oxygenation, – MV/FRC is 5:1 – Less number of underdeveloped alveoli, surfactant less – Ventilation is better controlled in infants < 3/12 of age
BLOOD• Hb 18-19 gm/dl.• PCV 60%• Fetal Hb 70-90%• ODC shifted to left• Blood volume 80 ml/kg• Cardiac index ,i.e CO/BSA is more
Metabolism & Thermal Homeostasis• O2 consumption is 7 ml/kg/mt – 7th day• Temperature control is the most imp. Consideration in pediatric anesthesia• Metabolism drives MV & CO by increasing rate.• Resting energy requirements is double that of older child.• Glucose is primay substrate for heart & brain
Metabolism & Thermal Homeostasis……• Neonate has core temp. of 370C – Increasing metabolic demands, – Decreased stored carbohydrates, – Decreased liver function, – Increasing tendency to hypoglycemia – Heat production by non shivering mech.
Fluid & Electrolyte Balance• Initial fluid replacement must be low• Overhydration can cause pulmonary edema• Neonate requires Na: 2-3 meq/kg/day• K : 2-3meq/kg/day• Hypocalcemia is common in premature, sick & acidotic• Daily maintenance of Ca 500mg/kg/day• Hypoglycemia is common in prematures < 20mgs/dl
PAC & OPTIMISATION• Keep in mind – Neonatal problems – Surgical problems – Associated congenital problems• Maintain – Clear airway – O2 therapy to achieve PaO2 of 50-70mm.Hg – Stomach decompression – Keep the baby warm at 370 C. – I.V.line – Correct acidosis if pH is < 7.3 with soda bicarb. 1-2meq/kg, slow infusion over 10-30 mts.
PAC & OPTIMISATION….. – Ventilate if PaCO2 is > 50mm.Hg. – Correct dehydration ( crystalloids), • Insensible loss • GI losses • Others – Correct hypovolemia ( colloids) • Albumin, plasma, RBC, & whole blood if necessary. – Arterial line in critically ill patients.
MONITORING• Precordial stethoscope or esophageal steth.• ECG lead II• BP cuff, oscillometer, arterial cath• CVP – int.jugular, cubital vein• Temp., thermister probe – rectal,esophageal or nasopharyngeal
MONITORING…..• Ventilation – Airway pr.monitoring, – O2 analyser – Mass spectrography – Infra red capnograph• Blood gases- – SPO2, ETCO2, blood glucose & electrolytes
MONITORING…..• Blood loss – Small vol.suction traps, – Swab weighing, – Serial Hct estimation• Urine volume – Urinary catheter & collecting bag• Above all, trained anesthesiologists eyes , hands & ears are indispensible.
ANESTHESIA• Major decision is whether or not the neonate needs post-op ventilation & resuscitation.• If post-op ventilation is needed, anesthesia technique is of little importance, any tech. which maintains BP & oxygenation is acceptable.• If extubation is planned, anesthesia tech. is very crucial.• GA + Regional tech. with epidural Bupivacaine 0.25 %, 1 ml./kg with adrenaline is good.
ANESTHESIA….• Regional block reduces doses of muscle relaxants, narcotics & recovery will be good.• Post-op pain relief can be planned• All new borns must be intubated unless it is a very minor procedure• Consider them always ‘full stomach’• Rapid sequence induction- no need of priming with NDMR before DM. No fasciculations, no rise of pressure with DMR.
INDUCTION• It is to eliminate stress,• CVS stability,• To secure airway & ventilation,• To prevent aspiration.• Gastric pH at birth is 6.0; after 6 hrs. it is 2.5
INTUBATION• It can be awake, or anesthetised.• Indications for awake intubation: – Very sick patients – Anesthesiologist inexperienced in pediatric anesthesia – H/o apnoea or respiratory distress, – Full stomach.
INTUBATION…..• Complications of awake intubation: – Arterial hypertension, – IVH – Apnoea, – Obstruction to breathing, – Desaturation & bradycardia• Deep inhalational induction & 2% xylocaine spray followed by intubation• Intubation after paralysing with SUXA 2mg/kg (controversial) , or NMDR & cricoid pressure.
INTUBATION…..• Preoxygenation for 2 mts.is a must, uncuffed ET , 20-40 cm/H2O pressure, no pillow under the head & head extended.• MAINTENANCE: • Good oxygenation, prevention of stress due to pain by short acting narcotics, intermittent inhalational & muscle relaxants.
Maintenance… – Intra – op fluid therapy: • 0.2 % saline with 5% dextrose closely resembles the obligatory fluid of neonate • 4 ml/kg/hr. ( hyponatremia if given more) • Better to use 0.45 % saline c 5% Dx. • RL for 3rd space losses • More 5% Dx causes hyperglycemia which leads to IVH due to diuresis, cell dehydration & severe hyperosmolality. • 5% Dx should not exceed 15-20ml/kg • Serial estimation of glucose is necessary.
Maintenance… • 3rd space losses in NEC, Omphalocele & gastroschisis can exceed patients blood volume. • CDH , congenital heart patients may not tolerate larger vol. • Interstitial edema develops • Serial estimation of Hct , proteins , osmolality , electrolytes & urine output help in accurate replacement of fluids. • Neonate can tolerate 10% of blood loss • Transfusion reactions like coagulation defects, temp. changes, metabolic problems occur early in neonates
RECOVERY• Recovery is quick ,• Extubation without good recovery causes laryngeal spasm,• Rx with IPPV , head extension , mandible thrust.• If desaturation occurs ( < 85% ) IV suxa & intubation.• Don’t wait for cyanosis & bradycardia!• Strong inspiratory efforts c obstruction causes pul. edema,• NMJ block must be reversed fully until active movements of all 4 limbs occur• Temp. must be > 35 0 C before reversal.
POST-OP PERIOD• Most vulnerable period , hypoxia , laryngospasm & cardiac arrest are common.• Respiratory depression: Due to – Apnoea • Prematurity , narcotics , anesthetics , incomplete reversal , hypothermia , concomitant antibiotics & hypermagnesemia –(PIH) apnoea is more common below 41 weeks of PCA upto 4th mth.
POST-OP PERIOD…Hypoxemia due to – Hypothermia , sepsis & acidosis.• Rx: FiO2 for 1st 24 hrs., monitor SaO2• In conditions c reduced FRC like peritonitis, int.obstruction, massive transfusions, correction of omphalocele & gastroschisis- minimum of CPAP should be provided
POST-OP PERIOD…• Pre-op lung problems like RDS , pulmonary dysplasia needs active ventilation.• NMJ transmission impairment• Hypotension may be due to hypovolemia or residual inhalational agents• Metabolic complications: hypocalcemia, hypo & hyperglycemia.