- Factors related to hypotension in dogs under general anesthesia
- The study ...
- 🩺 What is a dog's hypotension?
- 🩺 What is the ASA status?
- ... and the most important knowledge of the study
- 🩺 Practical tips for anesthesia monitoring
- 📌 Memory for hypotonia prevention:
- 5 in -depth questions about "hypotension in dogs under general anesthesia"
- Comprehensive summary on the subject: hypotension in dogs under general anesthesia
Factors related to hypotension in dogs under general anesthesia
In the literature
Miller L, Duncan JC, Handel IG, Shaw DJ, McKenzie He, Greenhalgh Sn. Association between Body Mass and Hypotension in Dogs Under General Anaesthesia . J Small Anim Pract. 2023; 64 (11): 687–695. Doi: 10.1111/JSAP.13671
The study ...
Hypotony is one of the most common complications during general anesthesia in dogs, in addition to hypoventilation and hypothermia. It occurs in up to 38 % of the cases and can lead to delayed recovery, neurological deficits, intestinal degrees (e.g. suturehiscan) as well as renals -mixtemia and damage.
In this retrospective study, anesthesia protocols of 1,789 dogs were examined in a transfer clinic. Hypotony was defined as at least two consecutive measurements of the middle arterial pressure (map) below 60 mmHg at a distance of at least five minutes. The blood pressure measurement was invasively or non -invasively, depending on the assessment of the anesthetist: inside.
The following factors were significantly associated with an increased risk of hypotension:
- Brachyzeple breeds
- A higher ASA status (> III)
- Implementation of a surgical (compared to a diagnostic) intervention
- Bradycardia
In contrast, the following factors were associated with a lower risk of hypotension:
- Higher body weight
- Use of an alpha-2 agonist for a premium
- Higher body temperature during anesthesia
In 32 % of the cases, hypotension occurred at least once, with a median time of 31 minutes after the initiation of anesthesia until the first appearance. The duration of anesthesia had no significant influence on the risk of hypotonizing.
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🩺 What is a dog's hypotension ?
📌 definition
Hypotony refers to abnormally low blood pressure . In the dog, medium arterial pressure (map) below 60 mmHg or a systolic pressure below 90 mmHg is considered critical, since the organs are then no longer sufficiently supplied with blood - and thus with oxygen and nutrients.
🧬 Physiology: Why is blood pressure important?
The blood pressure is the pressure that the heart generates to pump the blood through the circulation. Stable blood pressure is crucial for:
- Tissue and organ perfusion
- Maintaining kidney function
- Oxygen supply of the brain
- Metabolic stability
If the pressure is too low, these functions can be quickly impaired.
⚠️ Causes of hypotension in dogs
🔹 During anesthesia:
- Vasodilation (vascular expansion) by inhalation anesthetics such as isofluran or Sevofluran
- Bradycardia (slow heartbeat)
- Myocardial depression (heart muscle is inhibited by medication)
- Volume deficiency (e.g. through soberness, blood loss or dehydration)
- Hypothermia (body temperature drop → slow metabolism & reduced cardiac volume)
🔹 General medicine:
- Heart diseases (e.g. dilatative cardiomyopathy)
- Sepsis or systemic inflammation
- Endocrine disorders (e.g. Addison disease)
- Blood loss, shock, trauma
🧩 Symptoms of hypotension
Often difficult to recognize because symptoms are non -specific:
- Weakness, apathy, lethargy
- Blow or cyanotic mucous membranes
- Extended capillary filling time (> 2 seconds)
- Cold body feeling, lower temperature
- Slowed pulse
- Tachycardia or bradycardia
- In severe cases: collapse, unconsciousness, kidney failure
🧪 diagnosis
- Blood pressure measurement (non -invasive: Doppler, oscillometry / invasive: arterial catheter)
- Control of accompanying vital parameters (heart rate, ETCO₂, temperature)
- Blood tests for the declaration of causes (e.g. hematocrit, electrolytes, kidney values)
🛠 treatment and management
Academy:
- Volume replacement : crystalloid liquids (e.g. ring lactate, NaCl 0.9 %)
- Medication:
- Atropin at Bradycardia
- Vasopressors (e.g. dopamine, dobutamine, noradrenaline)
- Heat maintenance : heat mats, heat lamps
- Reduction of the anesthesia depth , if possible
Prevention:
- Good premedication with a stable circulatory profile
- Early monitoring measures , especially with risk patients
- Heat management , keep fluid balance stable
- Regular blood pressure controls - every 5–10 minutes under anesthesia
🐾 risk patients
Special caution applies to:
- Small or geriatric dogs
- Brachyzephalen breeds (higher vagotonus)
- Heart or kidney patients
- Dogs with high ASA status (> III)
Hypotension in dogs is a serious, potentially life -threatening complication , especially under anesthesia. Early recognition and targeted intervention are crucial to avoid consequential damage to organs
Regular monitoring, risk assessment and good anesthesia management are the best measures to prevent and control.
:
🩺 What is the ASA status ?
📌 definition
The ASA status is a classification of a patient's general condition and was originally developed by the American Society of Anesthesiologists (ASA) .
It serves to assess the anesthesiological risk and to document them standardized- both in human and veterinary medicine.
🎯 Goal of the ASA status:
- Risk assessment of anesthesia or operation
- Communication aid in the medical team
- Basis to choose from:
- Anesthetic
- Monitoring intensity
- Postoperative care
📊 ASA classification (1–5) in veterinary medicine
| ASA status | Description | Example in dogs |
|---|---|---|
| Asa I | Healthy patient without illness | Young, healthy dog for castration |
| Asa II | Light systemic disease without functional restriction | Light skin infection, stable levy disease without symptoms |
| Asa III | Serious systemic disease with restriction of body function | Heart failure grade II, chronic renal failure |
| Asa IV | Severe, life -threatening systemic disease | Shock state, decompensated heart failure |
| Asa V | Moribund patient, survival without an operation not to be expected | Gausty, heavy trauma, terminal disease |
⚠️ Additional classification: "E" for "Emergency"
If an operation in an emergency , an "E" attached (e.g. ASA IV-E ).
🧠 meaning in practice
- The higher the ASA status , the higher the risk of anesthesia .
- Patients with Asa III or higher need:
- More intensive monitoring (e.g. invasive blood pressure)
- Special anesthetics (less cardiocetric)
- Often pre- and post anesthetic management (infusion, pain therapy)
- The ASA status does not depend on the operating type , but solely on the animal's state of health.
The ASA status is an important tool to systematically evaluate the state of health and anesthetizing risk of a dog.
He helps veterinarian: Inside, safe decisions when planning and implementing anesthesia - and specifically protecting particularly risk patients .
... and the most important knowledge of the study
Central practical knowledge:
- Most hypotension episodes occurred within the first 30 minutes after anesthesia input.
- Small patients have a lower ratio of body mass and body surface, which makes them more susceptible to hypothermia - a possible risk factor for hypotension.
- Brachyzephal dogs have an increased vagotonus, which can lead to bradycardia - this lowers the cardiac volume and increases the risk of hypotonizing.
- The non -invasive blood pressure measurement (e.g. Doppler, oscillometry) is technically more difficult and often less reliable in small or brachyzephal dogs.
- Although the invasive measurement provides more precise data, the observation of trends in the non-invasive method (e.g. continuously falling enddidal CO₂ value, waste of heart rate and blood pressure) can indicate hypotension at an early stage and intervention.
🩺 Practical tips for anesthesia monitoring
1. Early and continuous monitoring
- Start monitoring immediately after premium and continuously continue through all phases (introduction, maintenance, recovery phase).
- Use multiple parameter monitors to capture heart rate, blood pressure, temperature, enddidal CO₂ (ETCO₂), SPO₂ and ECG.
2. Use blood pressure monitoring specifically
- Invasive (arterial catheter) in risk patients (e.g. small breeds, brachyzephal dogs, Asa> III, long surgical time).
- Non-invasive (Doppler or Oscillometry) with a suitable cuff size (width = approx. 40 % of the leg or tail circumference).
- Pay attention to trend observation , not only individual values - a constant waste is a warning sign.
3. Pay attention to signs of hypotension
- Map <60 mmHg = critical
- Warning signals:
- Waste of heart rate (bradycardia)
- Falling ETCO₂ values (reference to lower perfusion)
- Blow mucous membranes, extended capillary filling time
4. Keep body temperature stable
- Small dogs cool faster from → heat documents, heat lamps and preheated infusions.
- Hypothermia favors Bradycardia and continues to reduce blood pressure.
5. Choose awards consciously
- Alpha-2 agonists (e.g. dexmedetomidine) can reduce hypotensive risk , but must be carefully used in heart patients.
- Hold anticholinergics (e.g. atropine), especially in brady karden patients.
6. Adjust liquid therapy individually
- Standard: 5–10 ml/kg/h crystalloid infusions
- In the case of hypotension possibly bolus (e.g. 3–5 ml/kg over 5–10 minutes) , then check effect
- Too much volume → Risk for volume overload, especially for cardiac patients
7. Team communication and logging
- Clear communication in the operating room in the event of changes in the vital values.
- Complete logging of every change + reaction to it (e.g. bolus administration, temperature measures etc.)
📌 Memory for hypotonia prevention:
"Small, cold, short - particularly vigilant!"
→ Small, hypothermic, brachyzephal patients have an increased risk of hypotension!
5 in -depth questions about "hypotension in dogs under general anesthesia "
Why is hypotension under general anesthesia in dogs so often and which physiological mechanisms are involved?
Hypotony under general anesthesia is not uncommon in dogs - it occurs in about 30–40 % of cases. The cause lies in the combination of several physiological and pharmacological factors:
vasodilation through inhalation anesthetics:
substances such as isofluran or Sevofluran have a direct impact on the smooth muscles of the blood vessels and lead to vasodilation (vasodilation). This reduces systemic vascular resistance - and thus the blood pressure.
Cardio -of -printing effect:
Many anesthetics have a negative effect inotropic, ie they reduce the contraction of the heart. This reduces the cardiac volume (HZV) - a decisive factor for maintaining blood pressure.
Bradycardia:
Especially with brachyzephalia breeds or when using opioids and alpha-2 agonists (e.g. dexmedetomidine), bradycardia can also occur, which also lowers HZV.
Lack of volume:
Many animals are soberly sober, which, in combination with possible loss of fluids (blood, evaporation, exudate), leads to a relative or absolute volume deficit.
Hypothermia:
hypothermia reduces the metabolism, slows down the heart and can lead to a further deterioration in the circulatory situation.
These factors often appear additive, which significantly increases the risk of hypotension during anesthesia.
Which dogs are particularly at risk of developing hypotension under anesthesia and why?
Some dog groups have a significantly increased risk of the occurrence of hypotension under general anesthesia. The risk patients include:
small dog breeds (e.g. Chihuahua, Yorkers Terrier):
They have an unfavorable ratio of the surface of the body to volume. That means: they cool out faster (hypothermia), which significantly affects the circulatory function. In addition, blood pressure measurement in small dogs is technically more difficult.
Brachyzephal races (e.g. bulldog, pug):
These animals often have an increased vagotonus, which leads to a higher tendency towards bradycardia. This reduces the cardiac volume, which in turn favors hypotension. Their anatomical peculiarities often make intubation and ventilation more difficult.
Dogs with ASA status III or higher:
These animals already have systemic diseases (e.g. cardiac or kidney diseases) before anesthesia, which restrict their circulatory stability. Even low changes due to anesthetic or fluid shifts can lead to blood pressure waste.
Older animals:
With increasing age, the ability to regulate the circulation decreases. In addition, there is often a reduced organ reserve.
Dehydrated or hypovolae animals:
dogs with lack of fluid have a limited circulating blood volume, which can significantly increase blood pressure drop under anesthesia.
The early detection of these risk factors enables targeted preparation and monitoring during anesthesia.
What are the consequences of an untreated hypotension under anesthesia for dogs?
Untreated or insufficiently recognized hypotension can lead to serious, sometimes irreversible organ damage :
kidney failure:
the kidney is very sensitive to ischemia (less blood circulation). Permanently low blood pressure can lead to acute kidney damage or insufficiency -with a significant increase in urea and creatinine postoperatively.
CNS damage:
A less blood flow to the brain can lead to hypoxia-related neurological failures-in rare cases up to blindness, seizures or loss of consciousness.
Delayed wound healing / seam of seam abhisces:
In surgical interventions, especially in the abdominal cavity, inadequate perfusion can affect the healing of the intestinal seam or other tissue.
Collapse and death:
In particularly severe cases, hypotension can pass into a cardiogenic or hypovolemic shock and let valley go away if not intervened in time.
close monitoring and immediate therapeutic reaction are essential for survival and recovery of the animal.
How can you recognize hypotension in dogs under anesthesia at an early stage?
The early detection of hypotension requires precise, continuous monitoring and the correct interpretation of early warning signs:
blood pressure measurement:
non -invasive (Doppler, oscillometry): easy to use, but inaccurate for small or restless dogs.
Invasively (arterial catheter measurement): gold standard - allows continuous, reliable values.
Combined observation of vital values:
falling ETCO₂ : Note on reduced perfusion
of bradycardia or tachycardia
Delayed capillary filling time (> 2 s)
pale or cyanotic mucous membranes
falling body temperature
of weak or poorly palpable pulse
trend monitoring instead of individual values:
a one -off value is less meaningful than a falling trend over 5–10 minutes .
Observe breathing patterns and reflexes:
Changes can indirectly indicate metabolic or hemodynamic instability.
By means of timely recognition, volume administration, medication or adaptation of the anesthesia depth can be reacted to immediately.
Which therapeutic measures are available when a dog becomes hypoton under anesthesia?
The management of the hypotension is caused by the cause and gradually:
reduce anesthesia depth:
If possible, the concentration of the inhalation anesthetic should be reduced in order to minimize vasodilatational effects.
Fluid administration (volume expansion):
crystalloid bolus administration (e.g. 5–10 ml/kg wrestling lactate over 10–15 minutes)
with persistent hypotension if necessary colloid or blood products
drug therapy:
anticholinergika (e.g. atropin): for bradycardia
inotropic substances ): Increase in contraction power
vasopressors (e.g. dopamine, noradrenaline): For vasodilation and refractory hypotension
heat therapy:
active heat supply with heat mats, warm infusions, heat lamps
goal: Normothermia
intensify:
blood pressure every 2–5 minutes
ETCO₂, temperature, heart frequency Check
oxygen supply:
100 % O₂ if necessary
check the ventilation settings
A structured reaction and close cooperation in the OR team are crucial to intervene quickly and to minimize the risk of consequential damage.
Comprehensive summary on the subject: hypotension in dogs under general anesthesia
Hypotension in dogs under general anesthesia is one of the most common and most potentially dangerous complications during surgical or diagnostic interventions. Studies show that up to 38 % of all anesthetized dogs experience at least one episode of hypotension. Effective prevention, early detection and therapy of hypotension in dogs under general anesthesia is therefore a central goal of any anesthesiological management in veterinary medicine.
The hypotension in dogs under general anesthesia is created by the complex interaction of various factors. The most common causes include drug -induced vasodilation, myocardial depression, bradycardia, hypothermia and hypovolemia. Inhalation anesthetics such as isofluran or Sevofluran systemically reduce vascular resistance, which leads to a drop in blood pressure. In the case of inadequate counter-regulation by the cardiovascular system, this results in the typical hypotension in dogs under general anesthesia .
Risk patients for hypotension in dogs under general anesthesia are in particular small dogs, brachyzephal breeds, geriatric patients, animals with cardiovascular previous illnesses and patients with high ASA status (American Society of Anesthesiologists). Special caution is advised in these animals, since hypotension in dogs under general anesthesia can occur faster and can have more serious consequences.
The monitoring of vital parameters is essential in order to recognize an early hypotension in dogs under general anesthesia In particular, the continuous measurement of the middle arterial pressure (map), the enddidal CO₂ (ETCO₂), heart rate, oxygen saturation and body temperature provides information about the circulatory situation. From a map of less than 60 mmHg, one speaks of clinically relevant hypotension in dogs under general anesthesia .
Non -invasive blood pressure measuring methods such as Doppler or Oscillometry are helpful, albeit inaccurate in very small or troubled patients. The invasive arterial measurement is the gold standard, especially for quantitative evaluation and continuous representation of the pressure of pressure in hypotension in dogs under general anesthesia .
hypotension in dogs under general anesthesia can have serious consequences: it leads to a reduced organ perfusion, which in particular can damage the kidneys, the central nervous system and the intestinal mucosa. Wound healing can also be impaired by insufficient blood circulation. Postoperative morbidity and mortality increases significantly if hypotension in dogs under general anesthesia is not recognized and treated in time.
The therapy of hypotension in dogs under general anesthesia depends on the cause and severity. The most important measures include reducing the depth of anesthesia, fluid boli with crystalloid solutions, gift of atropine in bradycardia as well as the targeted use of inotropics and vasopresses such as dobutamine, dopamine or norepinery. Normothermia should be guaranteed by active heat preservation measures in order to avoid temperature -related hypotension in dogs under general anesthesia .
An important aspect in the prevention of hypotension in dogs under general anesthesia is the individual anesthesia protocol. The choice of suitable premiums, especially Alpha-2 agonists in stable patients, can improve circulatory stability. Nevertheless, their application must always be weighed up individually, since these medication can also lead to bradycardia - an additional risk factor for hypotension in dogs under general anesthesia .
The documentation and trend monitoring are essential: a one -time measurement cannot reliably grasp hypotension in dogs under general anesthesia Dangerous blood pressure waste can only be seen in good time through close-knit controls every 5 minutes. Accompanying parameters such as a waste of ETCO₂ can also be an indication of reduced perfusion - often an indirect sign of hypotension in dogs under general anesthesia .
Heat management plays a key role. Due to the high surface-volume ratio, many small dogs quickly develop hypothermia that hypotension in dogs under general anesthesia . The use of heat lamps, heat lamps and preheated infusion solutions is a simple but effective protective mechanism.
, hypotension in dogs under general anesthesia is a multifactorial, frequent and clinically relevant complication. It requires a high degree of vigilance, experience and well -thought -out, patient -adapted procedure. Only through targeted preparation, continuous monitoring, differentiated therapy options and structured communication in the surgical team can the risk of hypotension in dogs under general anesthesia successfully minimize.
A holistic anesthesia management, which also pays attention to aftercare and fluid balance postoperatively, can help to further reduce hypotension in dogs under general anesthesia The aim must be not only to survive, but also to ensure the full recovery of the patient - without the late consequences of an undetected or inadequate hypotension in dogs under general anesthesia .