Page 459 - Clinical Small Animal Internal Medicine

43 Septic Shock 427

One method for determining if volume loading has been application of wet to dry bandages for continued debride-
VetBooks.ir adequate is measurement of central venous pressure, ment following the initial surgical intervention.
If the septic source is an abdominal viscus such as the
with a target of 8–12 cmH 2 O. Many of these patients
will not have a central line in place, in which case lack of
improvement in blood pressure following IV fluid uterus or bowel then laparotomy should be performed as
soon as the patient is stable enough for anesthesia with
boluses can be interpreted as evidence that volume the goal of eliminating ongoing bacterial contamina-
expansion is complete. When this happens, vasopressors tion with dilution or removal of already affected tissue.
are needed to increase systemic vascular resistance in an Similarly, if the septic source is in the thorax (ex. pyotho-
effort to increase blood pressure and maintain vital rax or lung abscess) then thoracotomy should be recom-
organ perfusion. There is no consensus on which vaso- mended. Pyothorax can be managed conservatively with
pressor is most effective and selection is largely based on placement of thoracostomy tubes acting as source con-
clinician preference. The most commonly used first‐line trol mechanisms and is reported to be effective 71% of
vasopressors are dopamine (5–20 μg/kg/ min) and nor- the time. The decision to manage cases with thoracos-
epinephrine (0.05–0.3 μg/kg/min). If normotension is tomy tubes versus surgical intervention depends on
not achieved at the upper end of the dose range for a geography, as well as clinician preference or training. In
single vasopressor then the addition of a second agent is areas of the country where inhaled grass awns from fox-
needed. Typical secondary vasopressors include vaso- tails are common, the frequency of surgery is expected to
pressin (0.01–0.04 U/kg/h) or norepinephrine if not be higher than that of an area in which those plants are
already used as a first‐line agent. not found. Lung abscesses must be managed with lung
While vasopressors function to increase systemic lobectomy. For cases with severe sepsis or septic shock
vascular resistance and improve perfusion of tissue secondary to pyelonephritis, source control interven-
beds, patients with sepsis or septic shock often have tions to consider include percutaneous renal pelvis cen-
concurrent systolic dysfunction. Positive inotropes are tesis or nephrectomy.
drugs that increase inotropy (contraction strength)
and chronotropy (contraction rate), resulting in an Antimicrobial Therapy
increased stroke volume and heart rate, and conse-
quently cardiac output. The most commonly used ino- The early administration of appropriate antibiotics is key
tropic medication is dobutamine. If evidence of systolic for successful treatment of patients with sepsis and sep-
failure is present then dobutamine should be started tic shock. Every effort should be made to collect culture
(5–15 μg/kg/min) and the dose titrated up every 15 samples before antibiotics are administered; however,
minutes until endpoints are reached or the top of the one cannot wait indefinitely to initiate treatment and the
dose range is reached. If dobutamine fails to result in goal should be to begin antibiotics within one hour of
resolution or improvement in shock then the addition recognition of septic shock. In patients with sepsis with-
of a vasopressor should be considered. It should be out shock, it is often much more feasible to withhold
remembered that many adrenergic drugs are positive antibiotic therapy until appropriate cultures have been
inotropes in addition to being vasopressors (ex. dopa- obtained.
mine and norepinephrine) and the primary effect is Ideally, the antibiotic administered would be effective
often dependent on the dose administered. For more against the offending organism in question. Unfortunately,
information about resuscitation endpoints, the reader in most cases the antibiotic sensitivities or the identity of
is directed to Chapter 41. the organism are unknown prior to initiation of antimi-
crobial therapy. Even when appropriate culture samples
are collected, the results are delayed by 48–72 hours
Source Control
or longer. Therefore, the initial antimicrobial selection
Source control is important for the resolution of sepsis should be effective against bacteria in all four quadrants
and septic shock and should be performed as soon as (gram positive, gram negative, aerobic, and anaerobic).
possible after the source is identified to improve the like- This usually requires the co‐administration of two or
lihood of recovery. Source control almost always requires more antibiotics. Unless a clear contraindication exists,
some degree of surgical intervention, ranging from lanc- the dose of all antibiotics should be at the high end of the
ing of an abscess to resection of perforated bowel. Good dose range, they should be given IV, and penetrate the
source control for wounds includes early and aggressive desired tissue bed. Examples of effective antibiotic com-
debridement of devitalized or infected tissue. Dogs with binations include combining potentiated penicillins
necrotizing fasciitis may require radical resection of (ex. ampicillin/sulbactam 30–50 mg/kg q8h or ticarcillin/
affected tissue and the use of vacuum bandaging or clavulanate 40–50 mg/kg q8h) with fluorquinolones