Yu, Yan – Hypocalcemia – Clinical Findings – FINAL.pptx
Hypocalcemia: Clinical FindingsAuthor: Yan YuReviewers:David WaldnerSean SpenceGreg Kline** MD at time of publicationLegend:Published May 7, 2013 on www.thecalgaryguide.comMechanismPathophysiologySign/Symptom/Lab FindingComplicationsHypocalcemia(serum [Ca2+] <2.1mmol/L)Altered sensory ability of peripheral nervesLess Ca2+ outside cells, with no change in + charges inside cellsPeripheral paraesthesia? Neuronal "excitability" (tendency to depolarize/trigger action potentials)Seizures(Refractory to anti-seizure medication)Spontaneous action potentials in motor neuronsPeri-Oral NumbnessSkeletal muscle tetany (chronic muscle contraction due to repetitive motor neuron depolarizations)LaryngospasmOn neuronal and cardiac myocyte membranes, voltage-gated Na+ channels become more permeable to Na+ influxSpontaneous action potentials in the brainTrousseau's SignTetany in the hand, esp after ? perfusion to hand (elicited via a blood pressure cuff, due to spontaneous action potentials from the median nerve. Often the first tetanic sign to develop with hypocalcemia.Chvostek's signTapping in front of the ear stimulates facial nerve depolarizations ? triggering ipsilateral facial muscles around the eye and mouth to contract (less specific)Delays repolarization of the myocardiumQT-prolongationRespiratory distressContraction of laryngeal muscles obstructs airwayIntracellular fluid becomes more positively charged relative to extracellular fluid (relative cellular depolarization) Note: "Total Ca2+" in the blood is either "free", or bound to albumin. The lab value measures the "Total Ca2+", but it is the "free Ca2+" that carries out Ca2+'s functions and determines if someone is hyper- or hypo-calcemic.Note: sick/ICU patients have ? serum albumin, due to ? synthesis from a sick liver. Their lab Ca2+ values can be "low", but since they have less "albumin-bound Ca2+", their "free Ca2+" may still be normal!Correct this by adding 0.2mmol/L to the lab Ca2+ value for every 10g/L drop of albumin below 40g/L? cardiac myocyte depolarization Rarely: ventricles can contract at abnormally fast ratesVentricular tachycardia (i.e. Torsades de Pointes)
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