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Basic things you need to know in surgery department

Posted: October 2, 2012 by kiamseong in Surgery

Things you need to know in surgical dept

(i)     ABG interpretation

Norms

pH 7.35-7.45

pO2 80-100 mmHg

pCO­2 35-45 mmHg

HCO3 22-26

*To convert mmHg to kPa divide 7.5

(ii)    If pH>7.45

pCO2 < 35

HCO3 >26

Respiratory Alkalosis

Metabolic Alkalosis

Hyperventilation

-stroke

-SAH

-meningitis

-anxiety

-hyperthermia

-PE

-salicylates poisoning

-profuse vomiting

-hypoK

-burn

(iii)  If pH<7.35

pCO2 > 45

HCO3 <22

Respiratory Acidosis

Metabolic Acidosis

         NAGMA                          HAGMA

Respiratory failure -RTA

-Diarrhoea

-Addison ds

-Pancreatic fistula

-NH­4 ingestion

-Drug-acetazolaminde

Increase in organic acid production

-lactoacidosis-shock, sepsis,hypoxia

-uric acid

-ketone-DM, alcohol

-drug – metformin, metanol

*anion gap = [ Na + K ]– [ Cl + HCO3 ]

(iv)  Oxygen dissociation curve

Left side of curve – ­pH ¯T ¯DPG (2,3 dephosphoglycerate)
Right side of curve – ¯pH ­T ­DPG (2,3 dephosphoglycerate)

p50 – point where saturation of Hb reaches 50% (at pO2=26.6)

ICU point (PaO2, SaO2) = (60mmHg, 91%) = lowest acceptable paO2 in ICU patient because further drop beyond this point lead to drastic drop in SaO2

Mixed venous point at SaO2 = 75%

(v)   Indication for intubation

ü  To deliver positive pressure ventilation

ü  Airway protection from aspiration

ü  During surgical procedures involving neck and head in non-supine position

ü  Neuromuscular paresis

ü  Procedures increases intracranial pressure

ü  Profound disturbance n consciousness

ü  Severe pulmonary and multi-systemic injury

(i)     Content in each pint of solution

Sol. Content Na K Ca Cl HCO3
NS NaCl 9g (0.9%) 150 150
HS NaCl 4.5g (0.45%) 77 77
D5% Dextrose 50g/L
D10% Dextrose 100g/L
HM NaCl + KCl + CaCl2 + Na lactate 131 5 2 111 29
3%Sal NaCl 30g (3%) 513 513

(ii)    Dehydration

Mild Moderate Severe
Adult 5% 7.5% 10%
Paeds* <3% 3-9% >9&

*according to Acute Diarrhoea Protocol 2011

(iii)  Fluid requirement

Total = Maintenance + Deficit + On-going losses

Maintenance = 40cc/kg/day

For Paeds: (use Holliday Segar Formula)

4cc/kg/h for 1st 10 kg

2cc/kg/h for next 10 kg

1cc/kg/h for subsequent kg

Deficit = 10 X % X Body wt

*replace over 12 hrs

On-going losses = losses from RT Aspiration, Drainage, third space loss, plasma loss etc

*usually replace per shift with HM/NS

In all head injury patient – give only NS

In burn patient – Parkland correction by HM

In paeds patient – usually use HSD5%

(iv)  Assess degree of dehydration based on

–           Mental status

–           Eye – sunken eye/crying with tears

–           Breathing

–           Mucosa/tongue

–           Skin turgor

–           Pulse volume

–           PR/BP

–           CRT

–           Periphery warm/cold

–           Urine output *good UO = 0.5-1cc/kg/h

(v)   Na requirement

Total requirement = Maintenance + Deficit

Maintenance = 2-3mmol/kg/d

Deficit (in mmol)= (140-x) X Wt X 0.6

*to convert to g, divide with 23.3

(vi)  K requirement

Total requirement = Maintenance + Deficit

Maintenance = 0.5-1mmol/kg/d

Deficit (in mmol)= (4-x) X Wt X 0.4

*to convert to g, divide with 13.3

Rules of K correction:

Rate should not > 1.5g per hour

Concentration should not > 3g in 1L (1.5g in 500ml)

If hypoK – use Mist KCl 15ml TDS

If severe hypo – load 1g KCl in 100cc NS over 1 hr

Or 2g KCl in 200cc NS over 2 hr

*make sure take ECG/put on cardiac monitoring during loading AND repeat RP post loading 2 hrs

If hyperK – use oral Kalimate 15g TDS

If severe hyper – “insulin chase”

ü  IV Ca Gluconate 10% 10cc over 2-5 min then

ü  IV Dextrose 50% 50cc then

ü  IV Actrapid 10unit

ECG changes

Hypo K Hyper K
Flat T wave

Narrow QRS

ST depression

U wave

Small P

Tall tented T wave

Widen QRS complex

Ventricular tachy/fibrillation

(vii)          Hyperglycaemia

DKA HHS/HONK
Absolute insulin deficiency Relative insulin deficiency
Dx:-pH < 7.3

-Dxt > 14

-Blood Ketone > 2 (get a ketone stick)

Dx:- Serum osmolarity >320

– Dxt >33

*Osm = 2(Na+K)+Glu+Urea

Principle of management:

  1. Fluid resuscitation – 2 large bore IV cannula (green 18G or grey 16G) in 2 antecubital fossa – 1 for maintenance, 1 for bolus
  2. Insulin therapy (not to start first if K less than 3.3), target Dxt in DKA 8-11, HHS 14-16 then ½ dose of insulin, if hypo – do not stop insulin, instead to use D10% drip
  3. Correction of electrolytes – BUSE & VBG 4hrly, make sure good urine output and no ECG evidence of hyperK when planning to load K
  4. Treat underlying causes (sepsis, MI etc)

*Indication of HCO3 – if HCO<10 give 100meq (10 Amp NaHCO3)

*if resolved and patient tolerating orally – to change to basal bolus regime 0.5-0.8u/kg/d and titrate with overlapping 1-2hrs with IVI sliding scale

(viii)           Preparing DM patient for elective and emergency surgery

Elective Emergency
Minor Major Treat DKAPostpone surgery until RBS <20 unless life threateningAim 7-11 mmol/L during surgeryGive D5% or DS + 20mmol KCl 8hrly + IVI insulin sliding scale
OHA – give normal regimeInsulin – omit on day of surgeryDXT QID OHA – omit long acting (glibenclamide)DXT QID* If RBS >15, to start insulin sliding scale