Page 48 - TNFlipTest

A14 Anesthesia
Intraoperative Management Toronto Notes 2019
What is the Deficit?
• patientsshouldbeadequatelyhydratedpriortoanesthesia
• totalbodywater(TBW)=60%or50%oftotalbodyweightforanadultmaleorfemale,respectively
(e.g.fora70kgadultmaleTBW=70x0.6=42L)
• total Na+ content determines ECF volume; [Na+] determines ICF volume • hypovolemiaduetovolumecontraction
■ extra-renal Na+ loss
◆ GI: vomiting, NG suction, drainage, fistulae, diarrhea ◆ skin/resp: insensible losses (fever), sweating, burns
◆ vascular: hemorrhage
◆ renal Na+ and H2O loss
◆ diuretics
◆ osmotic diuresis
◆ hypoaldosteronism
◆ salt-wasting nephropathies
◆ renal H2O loss
◆ diabetes insipidus (central or nephrogenic)
◆ hypovolemia with normal or expanded ECF volume ◆ decreased CO
◆ redistribution
– hypoalbuminemia: cirrhosis, nephrotic syndrome
– capillary leakage: acute pancreatitis, rhabdomyolysis, ischemic bowel, sepsis, anaphylaxis • replacewaterandelectrolytesasdeterminedbypatient’sneeds
• withchronichyponatremia,correctionmustbedonegraduallyover>48htoavoidcentralpontine
myelinolysis
Table 4. Signs and Symptoms of Dehydration
TBW (42 L)
2/3 ICF (28 L)
3/4 Interstitial (10.5 L)
1/3 ECF (14 L)
1/4 Intravascular (3.5 L)
(Starling's forces maintain balance)
Figure 9. Total body water division in a 70 kg adult
Percentage of Body Water Loss
3% 6%
9%
Severity
Mild Moderate
Severe
Signs and Symptoms
Decreased skin turgor, sunken eyes, dry mucous membranes, dry tongue, reduced sweating
Oliguria, orthostatic hypotension, tachycardia, low volume pulse, cool extremities, reduced filling of peripheral veins and CVP, hemoconcentration, apathy
Profound oliguria or anuria and compromised CNS function with or without altered sensorium
Colloids vs. Crystalloids for Fluid Resuscitation in Critically Ill Patients
Cochrane DB Syst Rev 2013;2:CD000567 Purpose: To evaluate the effects of colloids compared to crystalloids for fluid resuscitation, specifically when used in critically ill patients. Methods: A meta-analysis was performed looking at randomized controlled trials comparing colloid vs. crystalloid use in patients requiring volume replacement. Pregnant women and neonates were excluded. Primary outcome was overall mortality. Results: Results were broken down based on specific colloid. For albumin (or plasma protein fraction) the relative risk (RR) was 1.01 (95%
CI 0.93-1.10) as compared to crystalloid. For hydroxyethyl starch the RR was 1.10 (95% CI 1.02-1.19). Modified gelatin had a RR of 0.91 (95% CI 0.49-1.72) and Dextran had a RR of 1.24 (95% CI 0.94-1.65). For colloids mixed in a hypertonic crystalloid as compared to isotonic crystalloid the RR was 0.88 (91% CI 0.71-1.06).
Conclusions: There is no evidence that use of colloids improves survival in trauma patients, burn patients, or post-operative patients when compared to crystalloid solutions. Given the increased
cost of colloids as compared to crystalloids, it
is recommended that crystalloids be the fluid of choice in these patients.
What are the Ongoing Losses?
• traditionalthoughtthatfluidlossduringsurgeryresultedfrombloodloss,lossesfromFoleycatheter, NG, surgical drains, and third spacing (sequestration of fluid into other body compartments such as GI, lung, evaporation)
• fluid therapy accounting for these losses often resulted in excess crystalloid administration
• goal-directedfluidregimensassociatedwithlowerrateofpost-opcomplicationscomparedtopre-
determined calculations
IV Fluids
• replacementfluidsincludecrystalloidandcolloidsolutions
• IV fluids improve perfusion but NOT O2 carrying capacity of blood
Initial Distribution of IV Fluids
• H2Ofollowsions/moleculestotheirrespectivecompartments
Crystalloid Infusion
• salt-containingsolutionsthatdistributeonlywithinECF
• consensusguidelinesrecommenduseofbalancedcrystalloid(egRinger’slactate)overnormalsalinefor
routine replacement and resuscitation
• maintaineuvolemiainpatientwithbloodloss:3mLcrystalloidinfusionper1mLofbloodlossfor
volume replacement (e.g. 3:1 replacement)
• if large volumes are to be given, use balanced fluids such as Ringer’s lactate or Plasmalyte®, as too much
normal saline (NS) may lead to hyperchloremic metabolic acidosis
Colloid Infusion (see Blood Products, Hematology, H52)
• includesproteincolloids(albuminandgelatinsolutions)andnon-proteincolloids(dextransand
starches e.g. hydroxyethol starch [HES])
• distributeswithinintravascularvolume
• 1:1ratio(infusion:bloodloss)onlyintermsofreplacingintravascularvolume
• theuseofHESsolutionsiscontroversialbecauseofrecentRCTsandmeta-analyseshighlightingtheir
renal (especially in septic patients) and coagulopathic side effects, as well as a lack of specific indications for their use
■ colloids are being used based on mechanistic and experimental evidence but there is a paucity of definitive studies investigating their safety and efficacy; routine use of colloids should be avoided